Mansoura UniversityFaculty of Engineering

Mechanical Power Department Year 2008

Cooling Load estimationCooling Load estimation

Cooling loadCooling load :

We can define the cooling load as the rate at which heat must be removed from the conditioned space in order to maintain a specific air temperature and moisture content.

We are concerned with the cooling load more than the heating load because there is a lot of heat sources that increase the cooling load; such that solar radiation, Light inside the conditioned space, electrical equipments……even our bodies are heat sources. But on the other hand all these heat sources decrease the heating load required.

Components of Cooling Load:

External Cooling Loads: These loads are formed because of heat gains in the conditioned space from external sources through the building envelope or building shell and the partition walls.

Sources of external loads include the following cooling loads:1. Heat gain entering from the exterior walls and roofs2. Solar heat gain transmitted through the fenestrations3. Conductive heat gain coming through the fenestrations4. Heat gain entering from the partition walls and interior doors5. Infiltration of outdoor air into the conditioned space

Internal Cooling Load: These loads are formed by the release of sensible and latent heat from the heat sources inside the conditioned space.

These sources contribute internal cooling loads:1. People.2. Electric lights.3. Equipment and appliances.

Components of Cooling Coil Components of Cooling Coil LoadLoadCooling coil load Cooling coil load = = space heat gain + Duct system space heat gain + Duct system

heat gain + ventilation load.heat gain + ventilation load.

Load profile

Peak Load and Block Load Peak Load and Block Load

The zone peak loadThe zone peak load The block loadThe block load

Calculation Procedure Calculation of the over all heat transfer coefficients Calculation of external heat gain Specification of the peak hour load estimation for each room in every level Calculation of ventilation load

DESIGN CONDITIONSDESIGN CONDITIONS

Calculation of the over all heat Calculation of the over all heat transfer coefficientstransfer coefficients

External heat gain:External heat gain:

Heat gain through exterior wallHeat gain through exterior wall

Heat gain through the Heat gain through the ceilingceiling : :

Heat gain through glass windows:

Specification of the peak Specification of the peak hourhour

The peak time is 5 P.M

Load estimation for every room Load estimation for every room in each class:in each class:

D-1-External heat gain at the peak D-1-External heat gain at the peak timetime

heat gain through exterior walls (brick & concrete)

heat gain through exterior glass:heat gain through exterior glass: heat gain from ceiling:heat gain from ceiling:

D-2- Heat gain from light:

D-3-D-3- Heat gain from occupants:Heat gain from occupants:

D-4-D-4- Heat gain from equipments:Heat gain from equipments:

D-5- Heat gain from unconditioned spaces:

FINAL: The Total heat gain for every room

The ventilation loadThe ventilation load

The ventilation is the amount of fresh air required The ventilation is the amount of fresh air required not only for breathing but also for achieving not only for breathing but also for achieving

comfort & health requirements.comfort & health requirements. The importance of ventilation is:

1-Meeting the oxygen needs of the occupants.2-The dilution of the concentration of co2 to a satisfactorily level.3-Maintain positive pressure with in the building.4-To dilute indoor air from particles & contaminates.

Calculation of ventilation Calculation of ventilation load:load:

Ventilation per personVentilation per person

Ventilation per areaVentilation per area

1-Ventilation air sensible heat:

2-Ventilation air latent heat:

PSYCHROMETRICPSYCHROMETRIC

•psychrometrypsychrometry

Psychrometry is the science Psychrometry is the science dealing with the physical laws of dealing with the physical laws of air – water mixtures.air – water mixtures.

•Moist airDry air + water vapor

•Moist air is perfect gas

psychrometric chartpsychrometric chart

The psychrometric chart contains five The psychrometric chart contains five physical properties to describe the physical properties to describe the characteristics of aircharacteristics of air : :

•Dry-bulb temperature•Wet-bulb temperature•Dew-point temperature•Relative humidity•Humidity ratio

When any two of these five properties of air are known, the other three can be quickly determined from the

psychrometric chart.

Effect of Sensible Heat and Effect of Sensible Heat and Moisture Changes:Moisture Changes:

AHU 1AHU 1 fresh air unit fresh air unit

AHU 2AHU 2 fresh air fresh air

AHU 3AHU 3 mix air unit mix air unit

AHU 4AHU 4 mix air unit mix air unit

AHU 5AHU 5 mix air unit mix air unit

AHU 6AHU 6 mix air unit mix air unit

AHU 7AHU 7 fresh air fresh air

AHU 8AHU 8 mix air unit mix air unit

AHU 7AHU 7IT TAKES ROOMS (1-2-3-4-5-6-IT TAKES ROOMS (1-2-3-4-5-6-7-8-14-22- disk 1- Loopy"L/W" )7-8-14-22- disk 1- Loopy"L/W" ) ROOM SENSIBLE HEAT & ROOM LATENT ROOM SENSIBLE HEAT & ROOM LATENT

HEATHEAT SAFTEY FACTOR = 5%SAFTEY FACTOR = 5% New RSH =1.05 *ROOM SENSIBLE HEATNew RSH =1.05 *ROOM SENSIBLE HEAT New RLH =1.05 *ROOM LATENT HEATNew RLH =1.05 *ROOM LATENT HEAT RTH = RSH + RLHRTH = RSH + RLH RSHF = RSH / RTHRSHF = RSH / RTH HEAT FROM FAN HP = 5%HEAT FROM FAN HP = 5%

HEAT FROM DUCT LEAKAGE =0.5%HEAT FROM DUCT LEAKAGE =0.5% HEAT GAIN FROM DUCT = 0.5%HEAT GAIN FROM DUCT = 0.5% Final RSH Final RSH Final RLHFinal RLH SUITABLE BPF = 0.15SUITABLE BPF = 0.15 OUT SIDE AIR SH ( OASH )OUT SIDE AIR SH ( OASH ) OUT SIDE AIR LH ( OALH )OUT SIDE AIR LH ( OALH ) Calculation of EFFECTIVE HEATCalculation of EFFECTIVE HEAT Calculation of Grand HEATCalculation of Grand HEAT We know from chapter 2 that :We know from chapter 2 that : CMMo CMMo MOMO

But not equal to CMMo then we can use CMMs But not equal to CMMo then we can use CMMs in new calculation :in new calculation :

We can calculate supply air :

Calculation of EFFECTIVE HEATCalculation of EFFECTIVE HEAT Calculation of Grand HEATCalculation of Grand HEAT We can draw this on We can draw this on

psychrometric chart :psychrometric chart :

PROPERITIES OF POINT FROM CHART:

POINT T DB T WB RH W H V

O 40 28 40.67158 19.08975 89.36721 0.914102

R 24 17.06 50 9.338036 47.9 0.85416

M 0 0 0 0 0 0

S 13.5 12.726 91.80556 8.880191 36 0.823296

ADP 8.7 8.7 100 7.011069 26.4 0.807076

AHU 8AHU 8

IT TAKES ROOMS (9-10-11-12-13-15-16-17-18-19-IT TAKES ROOMS (9-10-11-12-13-15-16-17-18-19-20-21-22-23-24- disk 2- Loopy"L/N" - Loopy " 20-21-22-23-24- disk 2- Loopy"L/N" - Loopy "

L1 / SE"- Loopy " L2 / SE")L1 / SE"- Loopy " L2 / SE")

ROOM SENSIBLE HEAT & ROOM LATENT HEATROOM SENSIBLE HEAT & ROOM LATENT HEAT SAFTEY FACTOR = 5%SAFTEY FACTOR = 5% New RSH =1.05 *ROOM SENSIBLE HEATNew RSH =1.05 *ROOM SENSIBLE HEAT New RLH =1.05 *ROOM LATENT HEATNew RLH =1.05 *ROOM LATENT HEAT RTH = RSH + RLHRTH = RSH + RLH RSHF = RSH / RTHRSHF = RSH / RTH HEAT FROM FAN HP = 5%HEAT FROM FAN HP = 5%

HEAT FROM DUCT LEAKAGE =0.5%HEAT FROM DUCT LEAKAGE =0.5% HEAT GAIN FROM DUCT = 0.5%HEAT GAIN FROM DUCT = 0.5% Final RSH Final RSH Final RLHFinal RLH SUITABLE BPF = 0.15SUITABLE BPF = 0.15 OUT SIDE AIR SH ( OASH )OUT SIDE AIR SH ( OASH ) OUT SIDE AIR LH ( OALH )OUT SIDE AIR LH ( OALH ) Calculation of EFFECTIVE HEATCalculation of EFFECTIVE HEAT Calculation of Grand HEATCalculation of Grand HEAT

•We can calculate supply air :

We can draw this on psychrometric chart :

PROPERITIES OF POINT FROM CHART:

POINT T DB T WB RH W H V

O 40 28 40.67158 19.08975 89.36721 0.914102

R 24 17.06046 50 9.338036 47.9 0.854156

M 29.8 21.63373 48.93095 12.92529 63 0.8758

S 13 12.13594 90.7242 8.48839 34.5 0.821347

ADP 10.16 10.16 100 7.744306 29.75 0.812213

AIR DISTRIBUTION SYSTEMAIR DISTRIBUTION SYSTEM

Introduction:Introduction:

Purpose of designing ductPurpose of designing duct

Importance of high quality air Importance of high quality air distribution system.distribution system.

Main components of an air Main components of an air distribution system & distribution system & functions of it.functions of it.

Steps of design air distribution system.

Types of air distribution Types of air distribution system:system:

VelocityVelocity PressurePressure Duct designDuct design perimeter system(winter)perimeter system(winter) Overhead system(summer)Overhead system(summer) Individual duct methodIndividual duct method Trunk duct methodTrunk duct method

There are two general systems There are two general systems for supplying air is in common for supplying air is in common

use:use:

Ceiling distribution system Ceiling distribution system Inside Wall distribution Inside Wall distribution

supply air system.supply air system.

Return Air Systems.Return Air Systems.

Duct consideration.Duct consideration.

Duct Shape & Duct Shape & material&insulation.material&insulation.

Pressure in Ducts.

Pressure Losses in DuctsPressure Losses in Ducts

Duct Designing methodsDuct Designing methods

Velocity reduction method.Velocity reduction method. Equal Friction Method.Equal Friction Method. Static Regain MethodStatic Regain Method

Equal Friction Method.Equal Friction Method.

Equipment selectionEquipment selection

Why Sizing Is Important?Why Sizing Is Important?

Careful selection and sizing of Careful selection and sizing of cooling and heating (condition) cooling and heating (condition) equipment can reduce initial costs& equipment can reduce initial costs& increase homeowner comfort increase homeowner comfort &increase operation efficiency& and &increase operation efficiency& and greatly reduce utility costs. greatly reduce utility costs.

A common mistake is to oversize heating and A common mistake is to oversize heating and cooling equipmentcooling equipment

Bigger does not always mean better Bigger does not always mean better Bigger units cause more noise.Bigger units cause more noise.

Design And Demand Design And Demand ManagementManagement

Separate zones that require special Separate zones that require special conditions from general use areas.conditions from general use areas.

Selection MethodologySelection Methodology

Cooling load & load profile.Cooling load & load profile. Number & planet capacity.Number & planet capacity. Type of equipments available.Type of equipments available. Cost of redevelopment & replacement.Cost of redevelopment & replacement. Energy available.Energy available. Choose type of system & equipment.Choose type of system & equipment. Required works ( power & construction).Required works ( power & construction).

Calculate life cycle cost analysis.Calculate life cycle cost analysis. Review the Risk profile.Review the Risk profile. If a water cooled system is identified If a water cooled system is identified

as the least cost option but the air as the least cost option but the air cooled system remains as a viable cooled system remains as a viable alternative, consider whether the alternative, consider whether the associated risks should be eliminated associated risks should be eliminated by paying a cost premium to go with by paying a cost premium to go with the air cooled system. the air cooled system.

The flow of the heat in central The flow of the heat in central air conditioning system can be air conditioning system can be

summarized as follow summarized as follow

Chiller selectionChiller selection

GTH = 256.74 TR GTH = 256.74 TR

The available model From York-YAEP The available model From York-YAEP Catalogue which can cover the load Catalogue which can cover the load is (YAEP7777XC9B50PA) Air cooled is (YAEP7777XC9B50PA) Air cooled chillerchiller

Y: YorkY: York A : Air cooledA : Air cooled E: Export series E: Export series P: P series compressorP: P series compressor 7777: Compressor Size7777: Compressor Size X: Cooler typeX: Cooler type C: Condenser typeC: Condenser type 9:Fan type9:Fan type B:R407,CB:R407,C 50:Frequency(Hz)50:Frequency(Hz) P: Starting (Part wind)P: Starting (Part wind) A: Design level (Engineering change or PIN A: Design level (Engineering change or PIN

level)level)

Since QSince Qevpevp= 901 KW =256 T.R= 901 KW =256 T.R & Compressor Power = 348 KW = & Compressor Power = 348 KW =

466 hp 466 hp

Then the COP= 901/348 = 2.6Then the COP= 901/348 = 2.6

Grilles selection Grilles selection

We will use 3 types of grilles in We will use 3 types of grilles in supply duct & 3 types of grills in supply duct & 3 types of grills in return and exhaust duct : return and exhaust duct : ((we will we will use BETA INDESTRIAL catalogueuse BETA INDESTRIAL catalogue))

AHUNO. GTH FLOW RATE

AHU 1 74 2583AHU 2 110 1683AHU 3 91 2650AHU 4 76 2500AHU 5 75 2083AHU 6 106 2650AHU 7 155 2483AHU 8 133 3967

Selection of air handling Selection of air handling unitsunits

From MCQUAY CATALOGUE:

According to the Total heat According to the Total heat capacity capacity

According to Air flow rate According to Air flow rate

THE SELECTED MODLESTHE SELECTED MODLES

e-AHU Model (6 row)

AHU 1 e4000AHU 2 e5400AHU 3 e4000AHU 4 e4000AHU 5 e4000AHU 6 e5400AHU 7 e8400AHU 8 e6300

PIPING SYSTEM DESIGNPIPING SYSTEM DESIGN

What is the piping system?What is the piping system?

It is the piping network that connects It is the piping network that connects the chiller with all air-handling units the chiller with all air-handling units at different levels through the at different levels through the building. building.

The components of piping The components of piping system:system:

ChillerChiller Pipes ( supply & return )Pipes ( supply & return ) Fittings Fittings ValvesValves AHU coilAHU coil Expansion tankExpansion tank

Requirement of a piping Requirement of a piping system:system:

Achieve the required flow rate with Achieve the required flow rate with minimum pressure loss which leads to minimum pressure loss which leads to smaller pump and hence less first cost.smaller pump and hence less first cost.

Piping system typesPiping system types

1. Open system:1. Open system:

In which water is exposed to atmospheric In which water is exposed to atmospheric pressure so an open reservoir is used.pressure so an open reservoir is used.

2. Closed system:2. Closed system:

In which water is not exposed to the In which water is not exposed to the atmosphere at any point so an atmosphere at any point so an expansion tank is used with air vent.expansion tank is used with air vent.

Factors affecting losses in Factors affecting losses in pipespipes

1.1. Major losses.Major losses.

2.2. Minor losses.Minor losses.

Pipe sizingPipe sizing

1. Diameter calculation:1. Diameter calculation: GTH = Heat gain to water in cooling GTH = Heat gain to water in cooling

coilcoil GTH = Q waterGTH = Q water GTH = mw*Cpw*∆TwGTH = mw*Cpw*∆Tw Cpw=4.186 Kj /Kg.k & ∆Tw=5oCCpw=4.186 Kj /Kg.k & ∆Tw=5oC

& Let v=1.6 m/sec & Let v=1.6 m/sec

So from the past chart we So from the past chart we calculated all the calculated all the

sections diameters and sections diameters and the major pressure loss the major pressure loss per unit length for all per unit length for all

sections.sections.

2.Total pressure loss 2.Total pressure loss calculationcalculation

For minor losses we entered charts and got For minor losses we entered charts and got the required values.the required values.

SOSO

Total pressure drop = 13.7 kpaTotal pressure drop = 13.7 kpa

Total head loss = 45.85 ftTotal head loss = 45.85 ft

3.Pump selection3.Pump selectionUsing total water mass flow rate and Using total water mass flow rate and

total head loss,from the following total head loss,from the following chartchart

SoSo

We selected the following model:We selected the following model:

From Taco catalogueFrom Taco catalogue

FI series 1160 rpm (5011).FI series 1160 rpm (5011).

& for pump power:& for pump power:

ηη=80% So power = 9 HP=80% So power = 9 HP

4.Expansion tank selection4.Expansion tank selection

Tank volume = .08*Total system volumeTank volume = .08*Total system volume

= 178 litre.= 178 litre.

SO we selected from Taco catalogue:SO we selected from Taco catalogue:

CBX254CBX254

Water piping insulation:Water piping insulation:

Company : Enviropac.Company : Enviropac.

constructure :constructure :

outer layer : woven glass fiber.outer layer : woven glass fiber.

inner layer : Plain glass fiber.inner layer : Plain glass fiber.

thermal conductivity:k=0.04 w/m.kthermal conductivity:k=0.04 w/m.k

AdvantagesAdvantages

ControlControl

What ?What ? Why ?Why ? How ?How ? Control modes ?Control modes ?

Two position.Two position. Floating.Floating.

Proportional.Proportional.

Sensing elementsSensing elements

Temperature sensors.Temperature sensors. Pressure sensors.Pressure sensors. Moisture sensors.Moisture sensors. Flow sensors(paddle or vane).Flow sensors(paddle or vane).