A/C & R fA/C & Ref.ME73273

Dr. Ahmed F. ElsaftyM h i l & M i E i i D tMechanical & Marine Engineering Dept. College of Engineering and Technology

Arab Academy for Science, Technology & Maritime TransportMaritime Transport

References:References:

• ASHRAE Handbooks.• Mc-Quiston, F. C. et al. “HVAC Analysis and y

Design”, John Wiley& Sons Inc. USA. 2000.• Wang, S. K. “Handbook of Air Conditioning andWang, S. K. Handbook of Air Conditioning and

Refrigeration”, Mc Graw-Hill, Singapour,2001.• TROTT A R and Welch T “Refrigeration and• TROTT, A. R. and Welch T., Refrigeration and

Air-Conditioning 3rd ed”, Butterworth-Heinemann 20002000.

What you will learn?What you will learn?You will develop an understanding of the basics of air

fconditioning systems, the components of air distribution systems, considerations of human comfort, load and occupancy demand, and how codes and standards affect p ythe design of air systems. After completing the course, you should know:

– The functions of the components of an air distribution system, including p y gmajor equipment types and auxiliary components.

– The principles of air distribution as they relate to human comfort.– The principal codes and standards affecting air system design.

H t l t d i i l d t t d l l t– How to layout and size a simple duct system and calculate pressure losses in the system.

– Common methods for reducing airborne sounds in systems and– How to start an air system and diagnose common problems associated– How to start an air system and diagnose common problems associated

with air system start-up.

A/C & Refrigeration Contents:g• Definitions• Types of A/C• IAQ• Direct expansion Systems

– Unitary A/C Systems -VRV and VRF.C t l A/C S t• Central A/C Systems– All Air Systems. -Air-Water Systems– All Water Systems

• Refrigeration Methods• Refrigeration Methods– Vapour Compression System. - Absorption Air Conditioning– Thermo-electric Air Conditioning- - Desiccant systems– Thermo-acoustic Air ConditioningThermo acoustic Air Conditioning– Steam Jet Air Conditioning

• Methods of Heat Transfer• Methods of Air Distributionet ods o st but o• Duct System Design - Design overview, duct materials, duct construction,

design and sizing, and sample systems.• Air Outlets• The principal codes and standards affecting air system design.• BMS

Definitions:Definitions:

Refrigeration:The process of removing heat.p g

Air-conditioning:A form of air treatment whereby temperature, humidity, ventilation, and air cleanliness are all controlled within limits determined by the requirements of the air conditioned enclosure.

Trott, 2000

DefinitionDefinition

Air treatment (conditioning)The purpose is to keep -within well definedp p plimits- acceptable (comfortable) inside airdry bulb temperature, relative humidity, airy p , y,cleanliness, odor level, noise level and airmovement.This is to be done keeping in mind that thecost and the control are of premiumcost and the control are of premiumimportance.

The Air Conditioning SystemThe Air Conditioning System

A/C i th i lt C t l f• A/C is the simultaneous Control oftemperature, humidity, quality andmovement of air in a conditioned space orbuilding.

• An Air conditioning unit is understood to consist of heat transfer surface for heating co s st o eat t a s e su ace o eat gand cooling, a fan for air circulation, means of cleaning the air, a motor, a drive,means of cleaning the air, a motor, a drive, and a casing.

IntroductionIntroduction

• Purpose of air conditioning

Luxury:ResidentialCCommercial

NecessaryPharmaceuticalsPharmaceuticals industryLaboratoriesIT Industry

Air ConditioningAir Conditioning

Central Unitary

There are four basic system categories:1 Central chilled water air conditioning systems - All Air Systems

1.1 Single zone 1.4 Dual Duct1.2 Reheat 1.5 Multizone1.3 Variable Air Volume

2 Central chilled water air conditioning systems - Air-and Water Systems2.1 Induction 2.3 Two-pipe2.2 Fan Coil 2.4 Three-pipe

3 Central chilled water air conditioning systems - All Water Systems, including cooling towers which can also be applied to systems 1, 2 above

3 1 F il it3.1 Fan-coil units3.2 Central chilled water air conditioning system with fan coils and

other devices3 3 Water cooling tower3.3 Water cooling tower

4 Direct expansion Systems [i.e. direct expansion of refrigerant, without the chilled water cooling medium ]

4 1 Window air conditioners4.1 Window air conditioners4.3 Split type and package air conditioning systems4.2 Unitary and Rooftop Air Conditioners4 4 Heat pumps4.4 Heat pumps

Commonly used temperature scalesCommonly used temperature scales.

Psychrometry is the science dealing with the h i l l f i t i tphysical laws of air – water mixtures.

A psychrometerA psychrometer.

Sling psychrometeraspiration psychrometer.

PsychometricsPsychometricsDry-bulb Temperature: The temperature of air as registered by an ordinary thermometer.Wet-bulb Temperature: The temperature registered by a thermometer whose bulb is covered by a welted wick andexposed to a current of rapidly moving air.Dew point Temperature: The temperature at which condensation of moisture begins when the air is cooled.Relative Humidity: Ratio of the actual water vapor pressure of the air to the saturated water vapor pressure of the air atthe same temperature.

Enthalpy Deviation: Enthalpy indicated above, for anyf

Moisture Content: The weight of water vapor in grains or pounds of moisture per pound of dry air.Enthalpy: A thermal property indicating the quantity of heat in the air above an arbitrary datum, in Btu per pound of dryair. The datum for dry air is 0°F and, for the moisture content, 32 F water.

given condition, is the enthalpy of saturation. It shouldbe corrected by the enthalpy deviation due to the airnot being in the saturated state. Enthalpy deviation is inBtu per pound of dry air. Enthalpy deviation is appliedwhere extreme accuracy is required; however onwhere extreme accuracy is required; however, onnormal air conditioning estimates it is omitted.Specific Volume: The cubic feet of the mixture perpound of dry air.Sensible Heat Factor: The ratio of sensible to totalSensible Heat Factor: The ratio of sensible to totalheat.Alignment Circle: Located at 80 F db and 50% RH andused in conjunction with the sensible heat factor to plotthe various air conditioning process linesthe various air conditioning process lines.

Air Handling UnitAir Handling Unit

BASIC UNIT:■ FAN■ COIL (AND/OR)HEATER■ COIL (AND/OR)HEATER■ FILTER■ MIXING BOX

Cooling processCooling processAMBIENT: 105oF db, 78oF wbROOM: 75oF db, 50% RHMIXING: 81oF db 44% RHMIXING: 81 F db, 44% RHCOIL: 53oF db, 95% RH

Comparison between split and central air conditioning systems

Item Central System Split SystemItem Central System Split SystemTemperature control Better Control Quality Higher Temperature

Fl iFluctuation

Air Cleanness Satisfactory Any Type of Air Filter May be installed

Not Satisfactory Low-Efficiency Air Filters areAir Filter May be installed Efficiency Air Filters are installed

Outdoor Air Yes No!!

Space Sound Level Lower Space Noise Criteria [NC] Curve with better Sound Attenuator

Lower Space NC Curve

better Sound Attenuator and Design

Load Diversity Higher Diversity No Diversity

Comparison between split and central air conditioning systems

It C t l S t S lit S tItem Central System Split System

System Efficiency Higher LowSyste c e cy g e ow

Equipment Life Longer Shorter

Maintenance Less Maintenance Work More Maintenance Work

Smoke Control Easier More Difficult

Operator Operator Required No OperatorOperator Operator Required No Operator

Comparison between split and central air conditioning systems

It C t l S t S lit S tItem Central System Split System

Initial Cost Higher Lowert a Cost g e owe

Energy Cost Lower Higher

Plant Room Chiller Plant and supply return fan rooms are

Separate Equipment Room not requiredreturn fan rooms are

neededRoom not required

Flexibility of Less Flexible More FlexibleOperation

Installation Complex Simple and Fast

Comparison between split and central air conditioning systems

C l S S li SItem Central System Split System

Energy Metering for Difficult SimpleEnergy Metering for individual Tenants

Difficult Simple

Future Expansion Less Flexible Flexible

If an existing Split air-conditioning system is renovatedg p g yinto a central system serving the same floor area, a life-cycle cost payback period of 3.9 years can be achieved inH t Cli tHot Climates.

Refrigeration MethodsRefrigeration Methods

• Vapour Compression System.• Vapour Absorption SystemVapour Absorption System.• Desiccant Systems.• Steam Ejectors.• Thermo-electric System• Thermo-electric System.• Thermo-acoustic System.

Comfort ChartComfort Chart

Psychrometric processesPsychrometric processes

Summer cooling loads