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United Nations Environment ProgrammeDivision of Technology, Industry and EconomicsEnergy and OzonAction UnitOzonAction Programme

Multilateral Fund for the Implementationof the Montreal Protocol

Study on the Potentialfor HydrocarbonReplacements

in Existing Domesticand Small Commercial

Refrigeration Appliances

UNEP


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Disclaimer

The United Nations Environment Programme (UNEP), the authors and the reviewers of this document and their employeesdo not endorse the performance, worker safety, or environmental acceptability of any of the technical or policy optionsdescribed in this document.

While the information contained herein is believed to be accurate, it is of necessity presented in a summary and generalfashion. The decision to implement one of the options presented in this document requires careful consideration of a widerange of situation-specific parameters, many of which may not be addressed by this document. Responsibility for thisdecision and all its resulting impacts rests exclusively with the individual or entity choosing to implement the option.

UNEP, the authors, the reviewers and their employees do not make any warranty or representation, either expressed or

implied, with respect to its accuracy, completeness or utility; nor do they assume any liability for events resulting from theuse of, reliance upon, any information, material or procedure described herein, including but not limited to any claimsregarding health, safety, environmental effects, efficacy, performance, or cost made by the source of information.

The reviewers listed in this document have reviewed one or more interim drafts of this document, but have not reviewedthis final version. These reviewers are not responsible for any errors which may be present in this document or for anyeffects which may result from such errors.

Trademarks

All product names and trademarks used in this document belong to their respective companies.

Reproduction of this document

Any or all parts of this document may be reproduced without prior or written consent, as long as the reproduced portion isattributed to UNEP.

UNITED NATIONS PUBLICATIONISBN 92-807-1765-0

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A Message from UNEP’s Executive Director

One of the major challenges posed to the Montreal Protocol is to protect the stratospheric ozone layerwhile ensuring that developing countries are not economically disadvantaged during their transition tonew technologies that do not rely on ozone depleting substances (ODS). This is particularly applicableto the refrigeration sector, which accounts for the largest share of ODS consumption in developingcountries and touches virtually every person’s life, directly or indirectly.

Today, developing countries face another unique challenge. What should those nations do with the

millions of existing domestic and commercial refrigerators and freezers that use ozone-depletingCFC-12 refrigerants? Unlike the practice in industrialized countries, the replacement of refrigeratorsand freezers due to old age or fashion is not common in developing countries. For some families andbusinesses, refrigerators are life-long possessions. Accordingly, repair, rather than replacement, is thehabit. Can those appliance owners in developing countries continue to use their existing refrigeratorsand freezers but at the same time protect the ozone layer by retrofitting the equipment to use non-CFCrefrigerants?

Under the leadership of UNEP DTIE’s OzonAction Programme under the Multilateral Fund for theImplementation of the Montreal Protocol, and with the generous support of Environment Canada,

GTZ/Proklima, National Research Council Canada, the Netherland’s Ministry of DevelopmentCooperation, the Swiss Agency for Development and Cooperation (SDC) and the Swiss Agency forEnvironment, Forests and Landscape (SAEFL), technologists and environmentalists around the worldresearched possible answers to this question. Their findings of their global studies and field experiencesare presented in this publication, the Study on the Potential for Hydrocarbon Replacements in ExistingDomestic and Small Commercial Refrigeration Appliances.

The study addresses retrofitting of existing appliances with hydrocarbons, which apart from protectingthe ozone layer, also have the advantage of not contributing to climate change as they are not greenhouse

gases (unlike HFCs). The study is intended to provide background to decision-makers in developingcountries who must weigh the positive and negative aspects of this retrofitting option.

UNEP believes that this study contributes to addressing the unique challenge faced by developingcountries in phasing-out CFCs and protecting the ozone layer.

I am particularly pleased that this study is being released in 1999, a year whichmarks the beginning of the Montreal Protocol control measures by developingcountries.

Klaus TöpferUnited Nations Under-Secretary-General

and Executive Director of UNEP


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Acknowledgements

This document was produced by UNEP Division of Technology, Industry and Economics (UNEP TIE) as part

of its OzonAction Programme under the Multilateral Fund.

The project was managed by:

Ms. Jacqueline Aloisi de Larderel Director, UNEP TIE

Mr. Rajendra ShendeChief, UNEP TIE Energy and OzonAction Unit

Mr. Steve Gorman Regional Network Manager, UNEP TIE

OzonAction Programme

Mr. James S. Curlin Information Officer, UNEP TIE

OzonAction Programme

And

Dr. W. Keith Snelson National Research Council Canada

Synthesis Report

Dr. W. Keith Snelson National Research Council Canada

Desk Survey

Prof. Radhey S. AgarwalCo-Chair, UNEP Refrigeration TechnicalOption Committee Indian Institute of

Technology (New Delhi)

Ir. Martien Janssen Member, UNEP Refrigeration Technical Option

Committee Re/genT BV (The Netherlands)

Workshop Report

Mr. Samuel Hess INFRAS Consulting Group for Policy Analysis

and Implementation

Mr. Nikolas SchallConsultant

Dr. Othmar Schwank INFRAS Consulting Group for Policy Analysis

and Implementation

Costa Rica Country Study

Mr. Ebel Dijkstra andMs. Marja Tummers

Ecozone (Netherlands)

Ms. Marcela Velázquez

CEGESTI (Costa Rica)

Cuba Country Study

Dr. Nelso Espinosa PinaOficina Técnica de Ozono (Cuba)



Ms. Marcela Vel·zquezCEGESTI (Costa Rica)

Indonesia Country Study

Mr Manfred EggerSwisscontact - SMEP



The document was written by:

Quality review of specific sections of this document was done by:

Dr. Lambert KuijpersCo-chair, UNEP Technology and Economic Assessment Panel

UNEP TIE wishes to thank all contributors and their employees for helping to make this document possible,as well as the generous support of Environment Canada, GTZ/Proklima, National Research Council Canada,the Netherland’s Ministry of Development Co-operation, the Swiss Agency for Development andCooperation (SDC) and the Swiss Agency for Environment, Forests and Landscape (SAEFL).


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TABLE OF CONTENTS

Page

PREFACE............................................................................................................ 7

SYNTHESIS REPORT ......................................................................................... 9

PART I - DESK SURVEY ..................................................................................... 27

1 Introduction .................................................................................................... 31

2 Acceptability of a retrofit refrigerant for domestic and small

commercial refrigeration systems ................................................................. 32

3 Refrigerant property data ............................................................................. 34

4 Material compatibility and refrigerant/lubricant interaction .................... 39

5 Appliance performance ................................................................................. 42

6 Reliability ........................................................................................................ 50

7 Safety aspects of hydrocarbon refrigerants ................................................. 53

8 Regulations and standards ............................................................................ 58

9 Availability and costs of hydrocarbon refrigerants ..................................... 62

10 Servicing and drop-in conversion of R-12 appliances

to hydrocarbon blends ................................................................................... 64

11 Conclusions and recommendations .............................................................. 66List of References .................................................................................................. 69

PART II - COUNTRY SPECIFIC SURVEYS............................................................ 85

Indonesia ......................................................................................................... 85

Introduction .......................................................................................................... 89

1 Overview phase-out of ODS in Indonesia ..................................................... 91

2 Methodology................................................................................................... 92

3 The proposed alternatives.............................................................................. 934 Could Hydrocarbons work.............................................................................. 94

5 Results UNEP Study ......................................................................................... 95

6 General observations and recommendations............................................... 114

ANNEXES ............................................................................................................... 117

Costa Rica ........................................................................................................ 163

1 Overview phase-out of ODS in Costa Rica .................................................... 167

2 Methodology................................................................................................... 168

3 The proposed alternatives.............................................................................. 1694 Could Hydrocarbons work.............................................................................. 170

5 Results UNEP Study ......................................................................................... 171


ANNEXES ............................................................................................................... 187

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Cuba ................................................................................................................. 229

Introduction ........................................................................................................... 233

1 Overview phase-out of ODS in Cuba............................................................. 234

2 Political background ....................................................................................... 2353 The Ministry of Environment ......................................................................... 236

4 The development of hydrocarbon refrigerant in Cuba............................... 237

5 Methodology................................................................................................... 238

6 Results Unep Study.......................................................................................... 239


ANNEXES ............................................................................................................... 255

PART III - WORKSHOP REPORT ......................................................................... 283

1 Introduction..................................................................................................... 2872 Results of the Workshop ................................................................................ 289

3 Conclusions...................................................................................................... 292

ANNEXES ................................................................................................................ 295

About the UNEP DTIE OzonAction Programme ....................................................... 367

About the UNEP Division of Technology, Industry and Economics .......................... 368

Table of con tents

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Preface

The possibility of using hydrocarbons (HCs) to retrofit existing CFC-based domestic and smallcommercial refrigeration applicances (e.g. refrigerators, freezers, small display cases, soft drink and icecream coolers) has been informally considered and applied for some years as a possible option to helpdeveloping countries meet their obligations under the Montreal Protocol. Until now, this issue has notbeen substantially investigated and documented in the context of the Multilateral Fund for theImplementation of the Montreal Protocol.

With only anecdotal stories and isolated data available, Article 5 countries, developed countries andother interested parties within the Multilateral Fund community have had little on which to basepotential future decisions about the viability of this technical option. This study helps close theinformation gap to some extent.

The study is designed to help policy-makers make informed judgements about retrofitting existingdomestic and small commercial appliances with HCs. It provides key information: conclusions a crucialinternational forum on this subject (the Workshop Report), existing technical information collectedfrom diverse sources (the Desk Survey), newly collected data from the field (the three Country Studies),and a “big picture” report that ties each of these elements together (the Synthesis Report). It also

identifies additional work that needs to be done before making decisions.

Although developed countries, bilateral agencies and refrigeration sector experts and others should findthe data and conclusions useful and thought-provoking, the study will be of particular interest to lowvolume ODS-consuming countries (LVCs). Like mid- and large-sized Article 5 countries, LVCs havecommited to reducing and eliminating CFCs and other ozone depleting substances (ODS) under theMontreal Protocol. However unlike their larger bretheren, LVCs have more limited options available inthe short term to reduce CFC consumption in order to meet their 1999 freeze and subsequent reductioncommitments under the Protocol. Retrofitting with hydrocarbons is one approach that could help them

meet these targets.

The need for this study emerged during late 1996 at meetings of the Regional Networks of ODSOfficers, during which UNEP received repeated requests for information on such issues as the technicaland economic feasibility of equipment conversion, safety and liability aspects, servicing requirements,and training needs. The study was approved and funded as part of UNEP’s 1997 Work Programmeunder the Multilateral Fund with additional financial support from Environment Canada,GTZ/Proklima, National Research Council Canada, the Netherland’s Ministry of Development Co-operation, the Swiss Agency for Development and Cooperation (SDC) and the Swiss Agency forEnvironment, Forests and Landscape (SAEFL).

In the interest of disseminating this information as widely as possible, UNEP is also making this reportavailable free-of-charge on its website at http://www.unepie.org/ozonaction.html.

Preface

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Study on the Potential for Hydrocarbon Replacements

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W. Keith Snelson

National Research Council Canada

Study on the Potential

for Hydrocarbon Replacements

in Domestic and Small

Commercial Refrigeration Appliances

Synthesis Report

January 1999

UNEP

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1. INTRODUCTION

In late 1996 interested delegates from Article 5, non-Article 5, as well as all the Implementing Agenciesattended a meeting in Costa Rica to discuss the possibilities of retrofitting used domestic and smallcommercial appliances with hydrocarbons (HCs) to replace CFCs. During this and follow-up meetingsof the networks of ODS officers a strong interest was expressed by all participants in the viability of thistechnology as a possible option to assist in complying with the requirements of the Montreal Protocol.The main target for this technology would be the Low Volume Consuming countries (LVCs) that havelimited options available in the short term to reduce CFC consumption for various appliances includingrefrigerators, freezers, small display cases, soft drink and ice cream coolers, etc. Any consideration of this option leads to the question whether there is sufficient information available to enable the policymakers and others in those countries to make informed decisions on the use of HCs for suchapplications. In an attempt to respond to requests especially from national ozone unit officers and othersfor more information on issues such as technical and economic feasibility of equipment conversion,safety and liability aspects, servicing requirements, training needs, etc., the United NationsEnvironment Programme - Division of Technology, Industry and Economics (UNEP DTIE) proposeda Study on this topic in its 1997 Work Programme and approval was obtained from the ExecutiveCommittee of the Multilateral Fund.

The Study was sponsored by UNEP with additional support from the Ministry of DevelopmentCo-operation in the Netherlands government. The National Research Council of Canada (NRC) was

selected to provide overall project management services for the Study. As the Project Manager, theindependent stature of NRC was perceived as being able to add credibility and provide an objective andunbiased approach to the final synthesis reporting process. The initial study work was conducted duringJuly/August 1997 and preliminary reports covering the various sections were prepared by thecontractors as input to a Workshop held in Montreal in September 1997. The Workshop provided aforum for dissemination and discussion of the issues among ozone officers, technicians, and policy-level officials from Article 5 countries as well as experts from Article 2 countries and others. (TheMontreal Workshop was funded, managed and reported separately and was not included under theproject management tasks in the Terms of Reference for the Study.) Follow-up work continued after the

Workshop and revised draft reports were completed and reviewed. Most of the study reports weresubsequently finalized in late 1997. However release of the Cuban country report was delayed at therequest of the government authorities to enable the Cuban Technical Ozone Office to provide its owninput which was received in April 1998.

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2. PURPOSE AND SCOPE

The overall objective of the Study was to review and assess the information and knowledge available(and identify areas where the level of understanding needs to be improved) on the feasibility of usingvarious HCs as replacements for CFCs, especially in existing domestic and small scale commercialrefrigeration equipment. With the focus on applications in Article 5 countries and the potential foreligibility of financing from the Montreal Protocol Multilateral Fund (MF) the Study was also intendedto address the issues that need to be considered by the MF in its efforts to assess whether the technologyis proven, environmentally viable, and represents a cost-effective option.

The Study was divided into two parts:

(1) A Desk Survey (Part 1) to review all existing literature available on experiences with HCs whenused as replacements in existing domestic/small commercial refrigeration systems. The objectiveof the literature review was to establish whether sufficient information was available to accept HCsas possible drop-in or retrofit refrigerants in such applications. This task was shared by Re/genTBV (Mr. Martien Janssen) and the Indian Institute of Technology (Prof. R.S. Agarwal).

(2) A Country Specific Survey (Part 2) to assess the particular experiences in three selected countriesof Costa Rica, Cuba and Indonesia, where various HC (and LPG) technology related programs inthis particular application area were known to have been active in recent years. This part of the

Study was undertaken by Ecozone BV (Mr. Ebel Dijkstra and Ms. Marja Tummers), with supportfrom Swisscontact-SMEP (Mr. Manfred Egger) and Cegesti (Ms. Marcela Velázquez). Additionalinput for Cuba was subsequently provided by the Oficina Técnica de Ozono (Dr. Nelson EspinosaPena).


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containing a corresponding set of observations, followed at the end by some general conclusions andrecommendations.

In the case of Indonesia a total of 51 individuals were interviewed representing 25 organizations,comprising government ministries and agencies, refrigeration equipment manufacturers/retailers,service workshops, technical training centres, etc. Since HC refrigerants are relatively new in Indonesia,most respondents were not able to answer all questions and some were not relevant, but thequestionnaire served as a satisfactory framework for discussion in the various interviews.

In Costa Rica a series of 12 interviews were performed, covering a representative cross-section of thoseinvolved in the potential introduction of HC refrigerants in that country. The group interviewed includedindividuals from government, refrigerator manufacturing, refrigeration equipment distribution, serviceand maintenance workshops, user industry, and university/training institutes.

In Cuba some of the planned interviews were subsequently cancelled, but eventually 11 organizationswere visited and 25 representatives mostly from government agencies were questioned. Very significantand extensive experiences with retrofitting of a special LPG blend were discussed in some of theseinterviews. Initial reporting of this information was completed by the contractor but not released,pending review and authorization from Cuban government officials. Eventually the contents of the samereport were accepted with minor changes.


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4. MAJOR FINDINGS

4.1 Part 1 - Desk Survey

Most of the literature discussed in the Desk Survey pertains to blends of R-290/R-600a (propane andisobutane), since these fluids can be composed to form blends having a very similar cooling capacityand pressure/temperature conditions to that of CFC-12 and are therefore most suitable for the domesticrefrigerator working fluid replacement scenario.

• Refrigerant Properties Data

The thermodynamic and thermophysical properties data for R-290 and R-600a as singlecomponent refrigerants are all well established over many years, and with the increasing use of these substances as refrigerant mixtures the corresponding properties of the blends of theserefrigerants are also well documented. Sophisticated computer software is also readily available toprovide complete and accurate properties data for pure hydrocarbons and their blends.

Upper and lower flammability limits by volume in air and corresponding auto ignitiontemperatures are well known for R-290, R-600a and typical blends. Sufficient data is also availableon the toxicity levels, exposure limits, and corresponding safety classifications of theserefrigerants.

In hydrocarbons the presence of contaminants can lead to problems and, depending on the level,may cause damage to compressors as well as adversely affecting system refrigeration capacitiesand efficiencies. This is particularly an issue when using LPG which often contains water and othercontaminants. Impurities within the refrigerant blend concentrations can also affect capacities andefficiencies, especially at higher deviations from the specified composition. The purityrequirements for R-290 and R-600a and limits on types of contaminants have been clearly specifiedby refrigerant manufacturers, and the same spedifications would apply for the blends. Howeverthere is little information available on the effects on refrigeration systems of deviating from the

specified purity levels.

It is clear that adequate information is available on pure HCs and blends including

thermodynamic and thermophysical properties, flammability and toxicity data,

contaminant/purity levels, and environmental data (ODP, GWP, etc.)

• Material Compatibility and Refrigerant/Lubricant Interaction

Some information is available to indicate good compatibility of both propane and isobutane withcommonly used refrigeration system materials including steel, brass, copper, aluminium, and

various elastomers and desiccants. An equal or better compatibility is claimed compared to CFC-12 and mineral oil systems. Further extensive but unreported experience with materials mustclearly exist among equipment manufacturers involved in the production of new domesticrefrigerators designed to operate (especially) with isobutane.

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In any refrigeration system some lubricating oil circulates around with the refrigerant through thevarious system components. The effects of the oil content are strongly related to the ability of therefrigerant to be dissolved into the lubricant. Higher levels of refrigerant solubility lead to marked

reductions in viscosity of the refrigerant/lubricant solution, which is beneficial for oil return to thecompressor but may be detrimental for bearing lubrication. In the case of hydrocarbons theavailable experimental data seems to be somewhat conflicting on the solubility effects of propaneand isobutane in mineral oil when compared to CFC-12 in mineral oil. For the most part it isreported that the hydrocarbons are more soluble than CFC-12, causing a reduction of viscosity inthe refrigerant/oil mixture, and therefore higher viscosity oil is recommended to compensate.However there is also contradictory evidence which indicates that higher levels of viscosity areexperienced with hydrocarbons and mineral oil, leading to corresponding recommendations forusing a lower or similar viscosity oil. In other retrofit investigations the original mineral oil wasused successfully with the hydrocarbon blend replacement, implying that the viscosity of the

solution did not change significantly and provided satisfactory operation.

In summary although publications on detailed analysis of materials compatibility are

relatively limited, it is concluded that propane and isobutane in combination with mineral

oils are compatible with commonly used refrigeration system materials. However

information on the solubility of hydrocarbons in mineral oil and the effects on viscosity is

somewhat contradictory, and further investigation is needed to clarify these issues.

• Appliance Performance

There are abundant references covering the performance of HC blends (especiallypropane/isobutane) applied in domestic refrigerators designed for CFC-12. Many investigatorshave conducted theoretical and experimental studies to determine the effects of substitutionparticularly on energy consumption. The studies have investigated single temperature and two-temperature appliances and cover drop-in and various levels of optimization including capillarytube size variation, refrigerant charge adjustments, and different blend compositions.

Various researchers have conducted measurements on the changes in energy consumption for anunmodified single temperature refrigerator using a R-290/R600a blend (50%/50%wt.) as a drop-inreplacement for CFC-12. Reported results vary from seeing little or no change up to an increase of over 20% in energy usage. In some cases substantial performance improvements were observed byincreasing capillary tube length, and varying the amounts of charge and mixture composition.Minimal information is reported on the effects on cooling capacity, but there are some reports of longer pull down times indicating reductions in capacity.

Several reports indicated that the zeotropic refrigerant blend is unsuitable for application in two-temperature appliances due to the separation of the two fluids causing unacceptably highrefrigerator temperatures and leading to elevated energy consumption levels (up to 30% higher).

However this temperature glide effect problem has been addressed in some cases by redesign of theunit to accommodate the two-temperature capability within a single evaporator.

In the case of small commercial refrigeration appliances conversion to hydrocarbons is simplerthan for domestic refrigerators since most are single temperature appliances. One company has


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reported achieving an energy efficiency increase of 15-20% after conversion of its line of displaycases to HC blends from HFC-134a. The only modification made was to seal any electricalcomponents that could possibly cause a spark. Other reports of retrofitting small commercial units

with the R-290/R-600a blend indicate that energy consumption is about the same or even less thanwith CFC-12, after making changes to the capillary tube length.

Sufficient information is available on energy consumption to indicate that application of

HC blends can yield small improvements depending on the level of system modifications

(e.g. adjustment of charge, capillary tube length, etc.), but can also result in increases up

to 30% for certain types of appliances (e.g. two-temperature compartments with separate

evaporators). However with regard to cooling capacity, there is clearly a lack of

information on the effects of hydrocarbon replacement. The latter is an important missing

element since it relates directly to the ability of the refrigerator to maintain specified

product storage temperatures at maximum ambient temperature conditions.

• Reliability

Some lifetime tests on compressors and domestic appliances with HC mixture refrigerants havebeen reported, and in general a good reliability is demonstrated. Specifically for the compressorstested, observations indicated no problems with wear, sludge and acid formation, copper plating,and deposits. Before and after analysis of refrigerant and lubricant also showed no degradation.

An important consideration for long-term reliability is the ability of the compressor to start andoperate at low or high voltages while exposed to low or high ambient temperatures. No data isreported on this topic for HC mixtures operating under retrofit conditions.

There are no significant amounts of data available on reliability testing of domestic

refrigeration equipment converted to run on propane/isobutane.

• Safety of refrigerant and equipment

Hydrocarbon blends are flammable in concentrations in air between 2% and 9% by volume, andpossibly a fire can start if a combustible mixture of fluid and air is present within those limits andsimultaneously an ignition source of sufficient intensity is present. Given the concern over thepotential of flammability under such conditions it is essential to adopt adequate safety measures inthe system when retrofitting or servicing with these refrigerants. The importance of the need forsafety is emphasized by the large number of relevant publications reviewed in the Study.Approaches vary from that of ignoring the safety problem altogether (due to the small chargeinvolved) to the other extreme of considering all possible events leading to hazardous situationswith corresponding detailed risk analyses. There are many references which emphasize thatappliances using flammable refrigerants need to be designed to meet very high technical standards

of safety. Systematic approaches have been developed for the safe handling, transport, and storageof hydrocarbon refrigerants. Depending on the safety classification selected for a particularappliance various levels of protection may be adopted, such as evaporators foamed into the cabinetwall and explosion proof electrical equipment (thermostat and lighting) located outside the cabinet.With new product the adoption of such measures is achievable and the corresponding risk

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assessment indicates a very low probability of a fire-event. Furthermore it is mentioned thatattitudes towards the use of a small charge of flammable refrigerant (less than 100 grams) mightnot be a major concern in some developing countries where much larger quantities of flammable

material are often utilized for domestic cooking purposes on a daily basis.

Risk assessment is an essential methodology used to address safety aspects of an operation, identifythe possibility of accidents, analyze the consequences, and assess the related risk probability.Results from several studies have indicated that the risk associated with the use of flammablerefrigerants in domestic appliances is reasonably low. However there is some experimentalevidence reported and demonstrated in videotapes, which shows that flammable conditions canexist in the vicinity of a refrigerator. In this series of tests quantities of propane/isobutane wereallowed to leak under controlled conditions into the space around the appliance and then a sparkwas introduced to cause ignition. These tests indicated that the heavier gases can accumulate at

ground level and lead to concentrations of refrigerant in air within the flammability range evenunder moderate ventilation conditions.

The issue of consumer safety as it relates to liability is briefly addressed. In the case of any safetyrelated problems with new equipment liability normally rests with the system’s manufacturers, butthe important question of who carries legal responsibility when an appliance is converted to operatewith flammable refrigerants has not been resolved.

It is concluded that sufficient safety related information is available on product design and

modification practices for the application of hydrocarbons in domestic refrigerationsystems, and this kind of information is being incorporated into amendments of some

existing standards. However more conversion details are required on specific products,

i.e. what modifications must be applied, when and how?

• Standards and regulations

Many investigators have conducted overview studies on regulations and standards relevant to theuse of HC blends as service refrigerants, but it is concluded that at present there is no singlestandard available anywhere in the world that addresses all the safety related issues. However thereare some national and international standards which discuss the mechanical and electrical safetyrequirements of domestic refrigeration appliances, and a few of these do include safety aspects of flammable refrigerants. In general most of the developing countries do not have any standardswhich include flammable refrigerants.

The European standard EN378 is currently under revision to include the use of flammablerefrigerants, and when adopted it is expected to supersede British standard BS4434 and Germanstandard DIN7003. In its revised form standard EN378 will classify refrigerants according to theirpotential hazards. For each refrigerant (including HCs and blends) a maximum practical limit is

specified in terms of allowable charge per unit of volume in a humanly occupied space.Additional limits are placed on maximum allowable charge according to the type of occupancy of the space. This standard also forbids the location of any ignition sources in the vicinity of systemscontaining flammable refrigerants. Elsewhere, other standards such as ANSI/ASHRAE Standard15 in the United States bans the use of flammable refrigerants except in experimental and


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industrial applications. However the U.S. EPA will consider approval of the use of hydrocarbonrefrigerants under its SNAP program if the application meets the requirement of a nationallyrecognized safety standard. The UL-250 standard for household refrigerators and freezers

now permits the use of flammable refrigerant in amounts, which would limit leaks to less than 40grams. In the international standards area IEC 335-2-24 (safety standard for householdrefrigerators) has been revised and now allows the use of flammable refrigerants in quantities up to150 grams.

A joint IEC/ISO working group has also been established to develop requirements pertaining to theuse of flammable refrigerants, and ultimately the measures approved will be incorporated asamendments to safety standards IEC 335-2-40 (heat pumps and air conditioners) as well as ISO5149 (mechanical refrigeration systems used for cooling and heating). It is anticipated thatcorresponding European, U.S., and Japanese standards will eventually harmonize with these ISO

and IEC standards.

It is clear from the level of activities reported in this area that there are many national and

international standards now under review, and that revisions involving the adoption of

flammable refrigerants are being considered. Whether the new provisions adopted by

such standards will be broad enough to apply to modification of existing equipment is an

important issue. As regards the existence of any rules and regulations permitting the

retrofit of refrigeration appliances with hydrocarbons this can only be determined for

specific cases by examination of regulations at the national level. Similarly in the case of

storage and transport of flammable refrigerants, where any laws do exist they aretypically governed by local authorities.

• Availability and costs

Refrigerant grade high purity hydrocarbons including propane and isobutane can be obtained fromrefinery distillation processes and are abundantly available from international manufacturersmostly located in Europe. Some manufacturers are extending their supply networks to servedeveloping countries. In some of those countries it may be possible to obtain refrigerant gradehydrocarbons as a by-product from local petroleum refineries or gas processing industries.

Costs of HC refrigerants are dependent on quantities being purchased, purity levels, and

various other market driven factors. However the data suggests that prices will be similar

to or lower than current CFC-12 cost.

• Servicing procedure

Safe servicing practices for appliances using hydrocarbon refrigerants are similar to the servicingprocedures followed for CFC-12 based units, except that additional safety precautions are needed

to avoid any risk of flammability. The necessary detailed safety measures have been widelyreported, covering the safe practices to be followed, guidelines for workmanship, and the specialtools and equipment required. The need for proper training of service technicians in this area isemphasized in many publications.

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As regards conversion of refrigeration appliances to operate with hydrocarbons, a systematic step-by-step procedure has been developed and documented for retrofitting of domestic refrigeratorsfrom CFC-12 to hydrocarbon blends. In this procedure it is suggested that any sparking electrical

components need to be replaced, re-positioned or enclosed when an appliance is converted.However in some cases the additional costs associated with making these and other retrofit safetymeasures may be prohibitive, depending on local economic conditions.

It is concluded that some useful practical guidelines and manuals have been developed for

safe servicing of domestic refrigeration equipment using flammable refrigerants, as well as

conversion procedures for such appliances to operate with hydrocarbon blends. However

this information needs to be improved with respect to emphasis on safety measures, and to

be more specific about which products can be converted and under what conditions.

4.2 Part 2 - Country Specific Survey

• Indonesia

So far the use of HCs in domestic refrigeration appliances in Indonesia has been limited to a smallnumber of entrepreneurs who have attended training workshops conducted by Swisscontact andEcozone to promote this technology. As a result there are less than ten service centres in the countrythat are currently applying the technology.

From these limited experiences reported there appears to be a good acceptance of HC technologyby those entrepreneurs and technicians who are involved in its application. No before and afterconversion performance measurements have been done for domestic refrigeration appliances. Noaccidents or problems are reported except for some misapplied refrigerant blend chargingtechniques. Apparently safety issues related to flammability are not a serious concern torefrigeration technicians working with HCs. This attitude is influenced by the widespreadhousehold use for cooking purposes of LPG in 12 kg cylinders, as compared to the small charge of less than 100 g used in typical refrigerators. There are no laws, rules, or regulations applied to theuse of HCs as refrigerants, and no general agreement on what body would be responsible foraccepting any liability.

With an impending government ban in Indonesia on future import of CFCs all seven of thecountries’ refrigerator manufacturers are in the process of converting their production lines fromCFC-12 to R-134a (with Multilateral Fund support). Therefore it appears likely that ultimately R-134a will become more readily accessible throughout the country for domestic refrigeration retrofitapplications as well as new production. In the case of existing systems however the choice of replacement refrigerant is driven by market forces and the use of HCs could become financiallyattractive as an alternative to CFC-12 if a sufficient cost advantage develops.

• Costa Rica

Experience here is also limited to those organizations that have been trained on HC technologiesduring projects involving Swisscontact, Ecozone, and others. The total number of entrepreneurs


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with access to imported HCs and to the technology is 43, out of an estimated total of 2,500 serviceworkshops existing throughout the country. Those who have used the technology in refrigerationsystem conversions consider it to be a useful option since the procedure is simple to follow

and requires no hardware changes. No accidents are reported. There is no conclusiveinformation available on the real performance of the HC refrigerant since observations from severalsources are conflicting on energy efficiencies, compressor pull down times, and producttemperatures.

Refrigeration service technicians are generally well trained, many having graduated from nationaltraining institutes, and therefore the introduction of HC technology on a broader scale withstructured training programs would not present any technical difficulties. Some of those questionedon the viability of hydrocarbons expressed the opinion that it is a good solution only if it isaccompanied by a strong training program and safety regulations. There are no regulations in the

country that control the use of refrigerants or refrigerant technologies and practices. This being thecase there is no clear direction on which organizations or persons should be legally responsible inthe case of an accident or a problem in the performance of the equipment.

Currently CFC-12 is still abundantly available in Costa Rica and the price is very low which makesit difficult to introduce alternatives to this refrigerant. However if the shipping costs of the importedHCs are reduced or if the local refinery is able to produce a suitable blend of HCs with the requiredlevel of purity, then hydrocarbon refrigerants could compete in the market with CFC-12 and maybe used more extensively as replacements.

• Cuba

Cuba is committed to complying with the Montreal Protocol ODS phase out requirements asdefined for Article 5 countries, and accordingly in 1998 the government there will legislate a banon importation of CFCs. However with the collapse of support from the former USSR in the early1990s the Cuban economy has experienced serious financial problems. With insufficient foreigncurrency being generated and a continuing trade embargo from the U.S., the import of basic goodsand materials was greatly reduced. This also affected the availability of refrigerants and created theneed to search for an acceptable, low cost, readily available alternative that could be adapted fordomestic refrigeration purposes.

The search led researchers at the Universidad de Oriente in Santiago de Cuba to develop ahydrocarbon blend LB-12, based on LPG produced at a local oil refinery and consisting of anunknown composition of propane, iso-butane,and n-butane. Starting in 1992 this development wassupported by the Government of Cuba, and the Cuban Ozone Technical Office has indicatedrecently that annual usage of LB-12 amounts to about 50 tonnes and that 175,000 domesticrefrigerators and 5,000 small commercial units are now successfully operating with LB-12 withoutany accidents reported. (This is approaching 10% of the estimated total number of refrigerators

existing in Cuba.) A limited amount of research has been conducted at the Universidad de Orienteon performance comparison of domestic refrigerators before and after conversion. However noinformation was available on the results of such tests, other than remarks to indicate that the energyconsumption was lower.

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Under control of the Cuban government the existing rules and regulations concerning production,transportation, storage and use of LPG as a fuel and cooking gas are currently being reviewed andadapted to cover hydrocarbons (including LB-12) as refrigerants. The new laws will be based on

national experience as well as existing relevant British and German standards.

Throughout the country all of the 200 plus refrigerator service workshops are state owned and allare now familiar with the application of LB-12 and the safety handling procedures. The workshopsare competent to carry out such conversions in spite of sometimes difficult working conditions andlack of spare parts and equipment. The service technicians employed in the workshops have usuallyreceived training in refrigeration technology at an intermediate level technical training institute, andnew regulations coming into force will require all service workers to acquire sufficient trainingneeded to obtain a certified permit to work in refrigeration.


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5. RECOMMENDATIONS FOR FURTHER INVESTIGATIONS

Based on analysis of the refrigerant acceptability criteria matrix and practical experiences reported inSection 4, some areas of information are still missing from the knowledge base. Accordingly thefollowing tasks have been identified for future investigation, with particular emphasis on thepropane/isobutane refrigerant mixture:

• Solubility data of selected HC blends with mineral oil and the effect of solubility on viscosity of the lubricant is required. Possible effects on blend composition change due to component solubi-lity differences should also be investigated.

• Some comparative calorimeter performance tests taking into account temperature glide effectsshould be undertaken to measure changes in cooling capacity and efficiency which can be expec-ted after a conversion.

• More specific lifetime tests are needed under severe conditions such as very high or very lowambient temperatures combined with low or high compressor start voltage conditions.

• Detailed information on product specific modification procedures needed to minimize risk shouldbe included in guidelines to be used for adapting appliances to hydrocarbon refrigerants.

• Further improvements are required to existing training and servicing manuals to expand on safetyguidelines and focus on which types of appliance may be converted under which conditions.

• Whether specific standards are enforced by the prevailing regulations in any particular country isan issue which needs investigation at the national level, to determine if a retrofit to HC refrigerants

is prohibited by law or not.

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6. CONCLUSIONS

An important observation documented in the concluding discussion at the September 1997 MontrealWorkshop stated that “The issue of retrofitting of small refrigeration appliances with hydrocarbons is acomplex one”. The significance of this statement was clearly demonstrated from the diverse experienceswhich emerged from the various investigations in this Study. It is evidently not possible to generalizeabout the feasibility of using HCs to replace CFCs in existing domestic and small commercialrefrigeration systems. From a technical standpoint the resulting performance after conversion will bevery product specific, may certainly be acceptable in cases such as one-temperature appliances, whilein others large energy efficiency penalties and excessive compressor running times may result. Safetyissues must also be addressed and this will be country specific, dependent on attitudes and sensitivitiestowards the use of flammable refrigerants and the existence of any regulations or standards within thecountry. The first requirement is to analyze whether a product can be safely retrofitted to the use of hydrocarbons. The level of safety measures adopted will also impact on the cost of conversion. Theavailability of sufficient numbers of adequately trained service technicians familiar with the handling of hydrocarbon refrigerants is another requirement to be addressed on a national basis. It seems clear thenthat the issue of feasibility must be approached on a case by case basis, to consider all the prevailingconditions and establish whether there is sufficient incentive to proceed. For some countries it may beworthwhile to facilitate this decision process by developing guidelines specific to that country’sinfrastructure and targeting specific products.

With regard to the funding support criteria used by the Multilateral Fund, not all of the issues areclarified:

• From an environmental viability standpoint, HCs are natural substances with zero ODP and negli-gible GWP, and this clearly represents an improvement over CFC based equipment. As regardsother environment related issues CO2 releases may be an additional factor to be considered in caseswhere the adoption of HC refrigeration systems leads to significantly higher levels of energyconsumption. The Total Equivalent Warming Impact (TEWI) includes the impact of greenhousegas emissions due to energy consumption as well as the impact of refrigerant emissions over the

lifetime of the system. Since the energy consumption component typically represents over 90% of the TEWI for domestic refrigerators, the energy efficiency of the system may be (environmentally)significant in situations where electrical power is derived from fossil fuel sources.

• Cost effectiveness is concerned with the price and availability of HC refrigerants, but is also rela-ted to the incremental cost of safety measures associated with conversion of refrigeration systemsto HC technology. These are country specific considerations which will be influenced by nationalpolicies on regulation of flammable refrigerants, and other factors such as possible access to localsources of suitable hydrocarbons at lower cost.

• Although there are indications that HCs could be a promising option for certain applications, thereremain some outstanding technical issues related to whether HC retrofit technology is generallyproven and these need to be further pursued. The next steps in this direction are outlined in therecommendations contained in Section 5.


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It can be concluded that this Study has assessed a broad cross-section of information and

experience related to the potential retrofit or drop-in application of HCs in small scale

hermetic refrigeration systems, and although some issues are still unresolved there is sufficient

evidence to indicate that this approach may be a valid option worth considering as a means of accelerating CFC phaseout in some developing countries.

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Study on the Potential

for Hydrocarbon Replacements

in Domestic and Small

Commercial Refrigeration Appliances

Part I - Desk Survey

UNEP

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28

PREFACE

This report presents Part I (being the so called Desk Survey) of the “Study on the Potential forHydrocarbon Replacements in Domestic and Small Commercial Refrigeration Appliances”. The reporthas been prepared by Prof. Radhey S. Agarwal of the Indian Institute of Technology, India and Mr.Martien Janssen of Re/genT, The Netherlands, being co-chair and member of UNEP’s TOCRefrigeration,AC and Heat Pumps, respectively. Compilation of all the material has been carried out byMr. Martien Janssen, in close collaboration with Prof. Radhey S. Agarwal during July/August 1997,after which the material was submitted to the National Research Council, Canada (Mr. Keith Snelson),being in charge of the project management of the study on behalf of UNEP DTIE. The material hasserved as input to a workshop held in Montreal, 8 September 1997. Hereafter, the report has beenamended upon comments received, and has been completed in November 1997.

ADDRESSES

Prof. Radhey S. Agarwal

Indian Institute of Technology (IIT)Hauz khasNew Delhi 110016 - IndiaTel: 91-11- 666 979 Ext. 3112Fax: 91-11-686 2037E-mail: [email protected]

Ir. Martien Janssen

Re/genT BVMeerenakkerweg 15652 AR Eindhoven - NetherlandsTel: 31- 40- 250 3797 / 3608Fax: 31- 40- 250 3677E-mail: [email protected]

Mr. W. Keith Snelson

National Research Council (ThermalTechnology Centre)Montreal Road, Building M-17Ottawa, Ontario K1A 0R6 - CanadaTel: 1- 613- 993 4892Fax: 1- 613- 954 1235E-mail [email protected]

Mr. Rajendra Shende

Chief, Energy and Ozonaction UnitUNEP Division Technology, Industryand EconomicsTour Mirabeau39-43, Quai André Citroën75739 Paris Cedex 15 - France

Tel: 33- 1- 44 37 14 59Fax: 33- 1- 44 37 14 74E-mail: [email protected]://www.unepie.org/ozonaction.html


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Part I Desk Survey

TABLE OF CONTENTS

Page

1. Introduction ........................................................................................................... 31

2. Acceptability of a retrofit refrigerant for domestic and small

commercial refrigeration systems ....................................................................... 32

3. Refrigerant property data .................................................................................... 34

3.1 Thermodynamic and thermophysical properties ................................................ 343.2 Flammability data ............................................................................................... 35

3.3 Toxicity ............................................................................................................... 363.4 Purity of hydrocarbon refrigerants ..................................................................... 373.5 Environmental data ............................................................................................. 38

4. Material compatibility and refrigerant/lubricant interaction .......................... 39

4.1 Material compatibility and refrigerant stability .................................................. 394.2 Refrigerant / lubricant interaction ...................................................................... 40

5. Appliance performance ........................................................................................ 42

5.1 Performance of domestic appliances .................................................................. 425.2 Performance of commercial refrigeration appliances ......................................... 475.3 Compressor calorimeter tests with hydrocarbons ............................................... 485.4 Summary ............................................................................................................ 48

6. Reliability ............................................................................................................... 50

6.1 Components ........................................................................................................ 506.2 Total System ....................................................................................................... 51

7. Safety aspects of hydrocarbon refrigerants ...................................................... 53

7.1 General considerations ....................................................................................... 537.2 Safety issues ....................................................................................................... 547.3 Risk assessment .................................................................................................. 567.4 Summary ............................................................................................................ 56

8 Regulations and standards .................................................................................. 58

8.1 Mechanical standards ......................................................................................... 588.2 Electrotechnical standards .................................................................................. 608.3 Regulations for storage and transport ................................................................. 618.4 Summary ............................................................................................................ 61

9. Availability and costs of hydrocarbon refrigerants ........................................... 62

9.1 Availability ................................................................................................................ 629.2 Cost of hydrocarbon refrigerants ............................................................................... 63


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10. Servicing and drop-in conversion of R-12 appliances to hydrocarbon blends 64

11. Conclusions and recommendations .................................................................... 66

List of References ........................................................................................................ 69


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1. Introduction

This report presents Part I (being the so called Desk Survey) of the “Study on the Potential forHydrocarbon Replacements in Domestic and Small Commercial Refrigeration Appliances”. The studycontains three more phases. Part II is formed by Country Specific Surveys where the experience withhydrocarbon replacement in selected developing countries is analysed. Part III is an internationalworkshop held in Montreal, 8 September 1997. During this workshop preliminary findings of Parts Iand II were presented and discussed. Part IV is a synthesis report for the overall study.

Existing literature has been reviewed that is available on experiences with hydrocarbons (HCs) andmixtures of hydrocarbons when used as replacements in small, existing, refrigeration equipment.Replacement can be considered both as a “drop-in” and as a retrofit. A “drop-in” situation is defined ascharging the equipment with the adequate amount of refrigerant without changing any of thecomponents that influence the refrigeration cycle characteristics. A “retrofit” situation is defined ascharging the equipment with the adequate amount of refrigerant after that certain components have beenoptimised for its use, which may imply a change of the compressor (i.e. the compressor capacity). Fordomestic and small commercial appliances, the conversion from CFCs to hydrocarbons or any othersubstitute is only relevant in case a repair of the system is needed.

The scope of the literature review is to define whether sufficient information is available to accepthydrocarbons as possible drop-in or retrofit refrigerants. First one has to ask which information is

needed for this purpose? This question is not unique. Other service refrigerants to replace CFC-12 areavailable and manufacturers of small refrigeration appliances have already been faced with thisquestion. Therefore some of these manufacturers have been consulted which led to the definition of eight criteria or aspects for which information is needed before a service refrigerant can be accepted.These aspects are listed and discussed in Chapter 2.

Chapters 3 - 10 subsequently present a review of the literature available on investigations performed intoeach of these criteria. Each of the chapters contains a short paragraph which summarises the status quoof the know-how on each of the criteria.

The report shortly considers pure fluids such as propane and isobutane, as well as mixtures of propaneor butane; the emphasis lies on the applicability of mixtures of propane and isobutane (R-290/R-600a).

Chapter 11 presents a table which summarises the information available and contains recommendationson whether the level of know-how is appropriate. This chapter also presents conclusions concerning theapplicability of hydrocarbons as service refrigerants as a function of the appliance type, ambientconditions, safety aspects, etc., and elaborates on the “quality” of the product after the replacement of the original refrigerant (CFC-12).

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2. Acceptability of a retrofit refrigerant for domestic andsmall commercial refrigeration systems

To evaluate the information available on hydrocarbon (blends) to be used for retrofitting purposes, it hasfirst been analysed what kind of information is typically needed for this purpose. This issue has alreadybeen dealt with by domestic refrigerator/freezer or compressor manufacturers. A manufacturer wouldlike to maintain the quality of its product (quality to be understood in broad perspective, performance,safety, reliability etc.). Therefore such a manufacturer would only accept a certain retrofit refrigerant forits products after collecting information and gaining experience. This note lists the necessary know-howrequired to qualify a refrigerant as a reliable service refrigerant. In principle the list presented is notspecific to a certain refrigerant but is generally applicable. For example, many of the aspects mentionedhere can be found in the qualification process of a ternary refrigerant by Musso et al. [Mus97]. The listhas been reviewed and commented on by persons employed by appliance and compressormanufacturers [Han97, Pil97, Pöh97]. Obviously, depending on which manufacturer asked, one aspectis considered more important than another.

1. Refrigerant information

Information on the following topics is required: thermodynamic and thermophysical properties,flammability and toxicity data (exposure limits), data on the purity of the refrigerant, environmen-tal data (ODP, GWP etc.), mixture behaviour (zeotropic or azeotropic).

2. Material compatibility data and lubricant/refrigerant interactionInformation on the compatibility between the materials used in the compressor (including lubricant)and the new retrofit refrigerant must be available. Such information may be available from sealedtube tests or “autoclave” tests where the actual compressor components, the oil and the refrigerantare stored at high temperatures for a certain time. Also compatibility of the retrofit refrigerant withmaterials used in the refrigerant circuit must be verified (including compatibility with processchemicals during the manufacturing process). If no or limited compatibility data is available, one maymore strongly rely on reliability data obtained in special compressor or appliance tests (see point 4).

Other important information is the solubility and miscibility of the combination of service refrige-

rant and compressor lubricant.

3. Appliance performance

Information on the influence of the retrofit refrigerant on the performance of a number of appliances(different product categories) must be available. Performance can be read in various ways:• Storage temperatures at different ambient temperatures, in order to verify whether the original

product specifications are maintained (e.g. product classification tropical, subtropical etc.);• The energy consumption of the appliance;• Starting characteristics of the compressor;

• Pull down behaviour;• Effect of the retrofit refrigerant on the noise level.

Maintaining the storage temperatures is often considered of more importance than maintaining theenergy consumption in a servicing or retrofit situation.


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4. Reliability

Information on the reliability of the components (mainly compressor) as well as the reliability of the total product must be available. With respect to the compressor, reliability data could be obtai-

ned by life time tests (reliability tests) where compressors are operated in closed loop systems atsevere conditions (e.g. evaporation/condensation temperatures -5 / 70 °C) during a certain time(e.g. 2000 hours). Hereafter, compressors are dismantled and investigated on wear characteristicsand on degradation of the lubricant and refrigerant. Results can be compared with the results of thesame type of compressors applying the original refrigerant.

The retrofit refrigerant may also influence the compressor starting behaviour which may be analysedwith compressor starting tests (important at low/high voltages and at low/high ambient temperatures).Reliability data for complete appliances can be gained with appliance life time tests whereappliances are operated at severe operating conditions (e.g. condensation temperatures of 60 °C)for a number of months. A possible degradation of the appliance performance must be monitored.Tests at low ambient (and low evaporation temperatures) may be required if limited solubility of some materials in the refrigerant/lubricant combination is expected at low temperatures (leadingpossibly to capillary plugging).

In general the reliability constraints put to a service refrigerant are less than those of the originalrefrigerant, since no 15 years additional lifetime of the compressor/cabinet after service needs tobe guaranteed.

5. Safety of refrigerant and the product Information on the safety aspects of the retrofit refrigerant must be available. This relates not onlyto the properties of the refrigerant (e.g. flammability limits) but also to safety aspects in handlingduring the servicing operation or safety aspects of the product after the retrofit.

6. Standards and regulations

Information on existing regulations which impact or limit the use of certain retrofit options is essen-tial. Next to regulations also information on standards may be necessary.

7. Costs and availability

Obviously, information about the availability of the retrofit refrigerant is essential to the acceptabi-lity. Costs may play a different role here since the cost of the refrigerant is only a part of the costsof a service or retrofit operation. The contribution of the refrigerant costs to the total costs are lar-gely influenced by local circumstances.

8. Servicing procedure

Evidently, any retrofit or service refrigerant needs to be accompanied with proper retrofit proce-dures and guidelines, i.e. one has to know how to change the original refrigerant by the new one.These procedures may contain actual practical guidelines (e.g. liquid charging for zeotropic mix-tures) as well as recommendations for which products the refrigerant is suitable. Next to this, label-ling the systems with respect to the refrigerant applied should be an essential part of the procedure.

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3. Refrigerant property data

There are some potential hydrocarbon refrigerants (or mixtures of hydrocarbons) which could be usedas replacements for CFC-12 which are outlined in Table-1.

Refrigerant Boiling Point (Possible) Application

Isobutane (R-600a) -12°C new domestic equipment

HC blend R-290/R-600a -33.8/-25.0 °C replacement for CFC-12(different compositions possible) (50/50 %wt) in new and existing equipment

HC blend R-290/R-600 (e.g. -32.0/-16.4 °C replacement for CFC-12LPG, varying composition) (50/50 %wt) in new and existing equipment

Propane (R-290) -42°C new high, medium and lowtemperature equipment

Table 3-1: Hydrocarbon Refrigerant Applications

Each of these refrigerants has different operating characteristics and therefore will be suitable forspecific applications. The hydrocarbon blends of R-290 and R-600a (e.g. CARE 30) or LPG (which isa mixture of R-290 and R-600) have been investigated as servicing or retrofitting refrigerants. Thehydrocarbon blends of propane with butane or isobutane are all zeotropic mixtures. This means theblends do not behave like a single substance during a phase change. Instead evaporation (and

condensation) takes place between two temperatures (the so called temperature glide). The blends do nothave a single saturation curve but a bubble temperature and dew temperature curve [Gar97a]. In view of this, it is suggested to charge the appliance only via the liquid phase (when vapour is being charged tothe product this will have a different composition than the bulk of the refrigerant in the charging bottle).

Most of the literature which will be discussed in this report, pertains to the blends of R-290/R-600a.Blends of these substances can be composed to obtain a saturation temperature/pressure curve as wellas a cooling capacity very similar to those of CFC-12, and have therefore been selected in variousinvestigations. Saturation data are shown in Figure 3-1 which includes data for a blend of R-290/R-600a50/50 % by weight.

Another hydrocarbon which has a pressure/temperature curve near to CFC-12 is cyclopropane. Its highprice and low availability have prohibited the application so far. Cyclopropane is not further discussedin this report.

This chapter discusses the literature available on refrigerant property data. Important data for arefrigerant are thermodynamic and thermophysical properties, flammability data, toxicity data,information on purity of refrigerant and environmental data.

3.1 Thermodynamic and thermophysical properties

Thermodynamic, as well as thermophysical property data of pure (single component) refrigerant suchas isobutane (R-600a) and propane (R-290), are well established and are available in literature andvarious handbooks [e.g. Cla93].


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Figure 3-1 : Saturation Pressure/Temperature Curves for CFC-12 versus various HCs,

data based on Refprop 5.1 [REF96]

Hydrocarbon blends were used as an alternative to CFC-12 in new manufacturing of single temperature

domestic refrigerators by FORON (German Company) in 1993 [Mey93a]. This was the beginning of the use of hydrocarbon mixtures as refrigerants in domestic refrigerators. The vapour-liquid equilibriumdata of various mixtures of R-290/R-600a was reported as early as 1966 [Hip66]. The thermodynamicproperties, especially for a mixture of R-290/R600a 50/50%wt were reported by Vollmer [Vol94]. Pro-perties of these blends can also be computed using e.g., Refprop [Ref96]. Agarwal [Aga94b] compiledthe properties of these blends over a wide range of temperatures and complete range of compositions.

In summary, sufficiently accurate data is available on thermodynamic properties of pure R600, R-600a,R-290 as well as on the properties of blends of these refrigerants.

Thermophysical properties viz., thermal conductivity, viscosity and specific heats for both the liquid andvapour phase are needed to design refrigeration systems and better understand heat transfer and pressuredrop characteristics of the working fluids. Several authors [Aga95, Li76, Vol94, Aga95b] computed,using estimation techniques, the thermophysical properties of the blends of R-600a and R-290 over awide range of temperatures and over a complete range of compositions for both liquid and vapourphases. The Refprop program [Ref96] can also be used to compute these properties.

In summary, there is sufficient data of reasonable accuracy available on thermophysical properties of the pure hydrocarbons and their blends.

3.2 Flammability data

Under certain conditions, hydrocarbons are flammable when mixed with air and ignited. Flammabilitydata for hydrocarbon refrigerants have been studied and are well documented. Table 3-2 shows the

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lower and upper flammability levels for pure R-600a, R-290 and for CARE 30 as a typical hydrocarbonblend (composition not available).

Refrigerant Flammable Limits in air-percent by volume Auto Ignition Temp (°C)

Lower Upper

R-290 2.2 10.2 365

R-600a 1.85 8.5 502

CARE 30 1.95 9.1 430

Table 3-2: Flammability limits of R-290, R-600a and the commercially available CARE30 blend

As an example for a discussion, CARE30 is taken. If there is less than 1.95 % by volume hydrocarbonblend in air there is insufficient hydrocarbon refrigerant for combustion. If there is more than 9.1 % thereis insufficient oxygen (from the air) for combustion. It has been estimated [Cal95] that 1.95%hydrocarbon blend in air is equivalent to 35 g/m3 and 9.1% of hydrocarbon blend in air is equivalent to165g/m3. However, practical limits are kept much lower, i.e. 8 g/m3 (see chapter 8.1) taking intoaccount the fact that the leaking refrigerant will not be evenly distributed in space but will tend toaccumulate at the lower level. Further, it has also been recorded that the ignition source must be hotterthan 430°C to be able to ignite the hydrocarbon blend / air mixture.

3.3 Toxicity

Toxicity data and exposure limits of refrigerants are essential data required for human and other beings’health. The toxicity tests are being conducted on hydrocarbon refrigerants both for short-term singleexposure and chronic (long term exposure) effects with an emphasis on the former. The toxicity data onhydrocarbons is available as given in Table 3-3 [Cal96]. The data include the following:

• LC50 the “lethal concentration for 50% of tested animals” sometimes referred to as the medianlethal concentration. This is a primary measure of acute toxicity by inhalation of gases.

• Cardiac Sensitization is characterised by two limits, LOEL which is the “lowest-observed effectlevel” (the lowest concentration at which sensitization occurs in tests) and the NOEL describedas the “no-observed effect level” (the highest exposure concentration at which no sensitizationis observed).

• The anesthetic EC50 level is defined as the concentration that caused temporary loss of abilityto perceive pain and other sensory stimulation to 50 % of test animals.

• PEL, the “permissible exposure limit” is the concentration level established by the Occupational

Safety and Health Administration (OHSA), UL group.

• The Underwriters Laboratories’ classification (UL group) reflects the comparative life hazard ofrefrigerant in the absence of flames or surfaces at high temperature. Group 1 is the most toxicand group 6 the least.


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grade material [Lys95]. For example a cylinder labelled “propane” may contain a mixture of propaneand other saturated and unsaturated hydrocarbons. In that case:• the refrigeration capacity of the system will not be as expected;

• the energy efficiency may be lower;• the pressures may be higher than expected, possibly causing leakage and stalling of the compressor.

The refrigerant quality is particularly an issue when using LPG, which is a blend of R-290 and R-600.The blend composition can vary widely depending on supplier and season, furthermore relatively highlevels of saturated alkanes, mercaptam, non-condensables and moisture may be present [TEAP97].

R-600a R-290

Purity, Vol % >99.5 >99.5

Moistening contents (max) mg/kg 10 10

Residue after evaporation (max) mg/kg 50 50

Non condensables (max) vol % 0.05 0.05

Other hydrocarbons (max) vol % 0.5 0.5

Boiling temperature range °C (during 0.5 0.5the evaporation of 5% to 95% of quantity)

Table 3-4: Technical specification for R-600a and R-290 refrigerants

The purity requirements given by the suppliers of R-600a and R-290 (for use as refrigerant) is given inTable 3-4. The purity of the blends would be the same as its constituents. Presently, there are fewsuppliers, located especially in Europe (see chapter 9). There is not much information available up towhat purity level hydrocarbon can be used. For those domestic refrigerator manufacturers that currentlyapply isobutane in their products, it is not a priority to investigate the effect of lower quality grades of isobutane. The reason for this is that costs of development are considerable, while the refrigerant costsform only a very small part of the production costs. Some efforts have been made to study the effect of impurity of hydrocarbon refrigerants on the performance of refrigeration circuits [Bol91], but the datais too limited for general conclusions.

3.5 Environmental data

Hydrocarbons are naturally occurring substances which are normally obtained from refineries after adistillation process [Gar97a]. These refrigerants have zero ODP and negligible GWP. The environmentalproperty data for hydrocarbon refrigerants and blends of current interest [TEAP97] are given in Table 3-5.

Refrigerant Atmospheric life ODP GWP(100yr)

R-600a _ 0


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4. Material compatibility and refrigerant/lubricantinteraction

When using HC blends under retrofit conditions, it is important to know the compatibility of therefrigerants with the materials inside the system. Of specific importance is the chemical interactionbetween refrigerants, lubricant and materials. Information may typically be available from sealed tubetests [ASH89] or autoclave tests. Since these types of tests are only a simulation of the real practicalcircumstances, the tests need to be complemented with system tests where actual appliances orcompressors are operated over a longer time period (mostly under severe conditions to accelerate thetesting procedure). These latter system tests (or reliability tests) are discussed in chapter 6.

Although not really a compatibility issue, the interaction between the refrigerant and lubricant, morespecifically the solubility and miscibility of the refrigerant / lubricant combination is also important.

4.1 Material compatibility and refrigerant stability

In general a refrigerant / lubricant combination may affect electrical insulation properties of windings,varnishes and ground insulation sheets. The combination may also have an impact on the properties of elastomers and plastics. When using HC blends in a retrofit situation, the compatibility of the HCs incombination with typical mineral oil is the most relevant.

In general the ARTI data base [Cal97] contains very detailed compatibility information for a largenumber of refrigerants, lubricants and materials. The data base includes information from the MaterialsCompatibility and Lubricant Research (MCLR) program which is a large research programadministered by the Air-Conditioning and Refrigeration Institute (ARI) in the United States. However,the data included for propane and/or isobutane is so far relatively limited.

Some compatibility information of common materials in a refrigeration circuit with propane andisobutane has been presented and a good compatibility with steel, brass, copper, aluminium, commondesiccants and a number of common elastomers is concluded [Del96]. However, the sources for thisinformation are not further identified. Calor Gas [Cal94a] gives recommendations for some elastomericmaterials which can be applied together with their CARE refrigerants (which contain isobutane,propane and ethane). Some further (limited) data can be found in [ASH97] (Chapter 18) where swellingof some elastomers is reported with butane.

Sansalvadore et al. [San96] further report on the compatibility of some polymers in combination withisobutane and mineral oils. An equal or better compatibility is concluded compared to CFC-12 andmineral oil systems. In the same publication also the stability of the refrigerant (isobutane) isinvestigated by means of sealed tube tests using Fe, Cu and Al as catalysts. It is concluded that thecombination of isobutane with mineral oil (nafthenic with or without additives) and with alkylbenzene

type of oils is stable.

Especially manufacturers of hydrocarbon compressors must have developed a detailed knowledge todate of the compatibility between several materials, lubricant and (mostly) isobutane. However, thisinformation is generally not publicly available.

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Though the amount of publications which present detailed compatibility analysis is relatively limited,it can in general be concluded that isobutane and propane in combination with mineral oils arecompatible with commonly used materials in refrigeration circuits designed for use with CFC-12. The

absence of chlorine or fluorine can be seen as an advantage which avoids potential hydrolysis leadingto acid formation [Mey93b].

4.2 Refrigerant / lubricant interaction

Refrigeration systems require lubricant not only to lubricate bearings but to seal compressed gasbetween the suction and discharge sides. The lubricant also acts as a coolant to remove heat from thebearings and transfer heat via the compressor shell wall to the exterior (this for hermetic systems).

Lubricant is transported from the compressor oil sump to the refrigeration system by the compressorand must return within a reasonable time. In general a good solubility and miscibility between lubricantand refrigerant is required to guarantee oil return.

Sansalvadore et al.[San96] report on solubility tests of isobutane and propane in mineral oil (ISO VG32and ISO VG15). In general, turbidity and cloud points are found below -60 °C. The authors thereforeconclude that oil return should not pose problems even in extreme conditions. Within the samepublication also the problem of oil foaming is discussed which is of particular interest to hermeticcompressors. When a compressor starts the pressure in the shell is reduced which reduces the solubilityof the refrigerant in the oil. Due to the subsequent release of the refrigerant, foam is being formed on

top of the oil level. Excessive foam formation may potentially lead to oil transport into the compressorcylinder and create structural damages. It is often mentioned that hydrocarbons are very well soluble inmineral oil. However, [San96] concluded that the foam formation using isobutane and mineral oil wasvery similar to the foam formation using CFC-12 and mineral oil.

Evaluating the solubility issue of hydrocarbons and oils gives a somewhat confusing picture. It is oftenstated that propane and isobutane are more soluble in mineral oil than CFC-12. This is stated to have aneffect on the viscosity of the refrigerant/oil mixture within the compressor shell. Generally it ismentioned that the viscosity is lower and therefore the use of a higher oil viscosity is recommended[Boc96, But95 and Ren95]. Also Meyer mentions the application of a higher viscosity oil in theproduction of hydrocarbon blend appliances by Foron [Mey93a, Mey93b and Mey93d]. Thiscontradicts with information supplied by Spauschus et al. [Spa94] who recommends a lower or similarviscosity oil for hydrocarbons and mineral oil.

This recommendation is based on test results showing that a propane mixture with mineral oil (and alsoa isobutane / mineral oil mixture) has a higher viscosity than a CFC-12 mixture with the same mineraloil at the same refrigerant / lubricant composition in weight percentages.

The definition of “higher” or “less” soluble is not quite straightforward when comparing refrigerants

with different saturation pressures and very different densities (e.g. when comparing CFC-12 andpropane). Comparing at the same pressure level or at the same composition (%weight) is not alwaysappropriate. Of more importance is

hydrocarbon replacement

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