႔

Chapter-7 Condensers and Evaporators

Chapter-7 Condensers and Evaporators Refrigeration system (

component

) Cooling load

refrigeration effect

( )

(continuous performance applications)

frost control

(ဂ) Refrigerant (ဃ) ၁ Direct expansion refrigerant unit ၂ Gravity ၊ pump recirculated ၊ flooded refrigerant ၃ Secondary coolant (brine, e.g., salt and glycol)

႔

၍

( ) System efficiency ( ) Air cooled၊ water cooled (

) Compressor

condenser

(open ၊ hermetic ၊ semi-hermetic motor drive ၊ reciprocating ၊ screw or rotary)

( ) System type (single stage ၊ single economized ၊ compound or cascade arrangement) ( )

refrigerant operating temperature

pressure

၍

)

၇.၁ Heat Rejection Condenser

႔

(၇-၁) (

Condenser load

႔

)

– (

)

(

)

(rate of heat rejection) (

)

(

) 7-1

Chillers and Chilled Water Systems

႔

၇-၁ Carnot cycle for refrigeration Oil cooler

႔

(oil-injected) screw compressor

(energy) compressor

၇.၂ Condenser Condenser

heat exchanger

condenser

Refrigerant

( ႔

႔

႔

၊

) ႔

Condenser

၍ (၁) air cooled ၊ (၂) water cooled

evaporative condenser ႔

႔

၍

Air cooled condeser

၍

water cooled condenser ၍

Chiller

Evaporative condeser

႔ condenser

heat exchanger

Shell and tube ၊ shell and coil ၊ tube within a tube condenser

(၃)

႔

evaporative

Condenser

Condenser

Condenser

(size)

(weight)၊

(location)၊

(weather conditions)၊

(availability of electricity) (process industry)

(availability of water)

condenser

႔

configuration

condenser (criteria) (၁) Condenser heat capacity (၂) Condensing temperature and pressure (၃) Refrigerant (၄)

coolant ႔၏

(operation period)

(၆)

(climatic conditions) refrigeration ႔

(၁) Water cooled condenser 7-2

(flow rate)

(design temperature for water and/or air)

(၅) Air conditioning

႔၏

(heat rejecting)

႔ condenser

႔

Chapter-7 Condensers and Evaporators

(၂) Air cooled condenser (၃) Evaporative condenser

႔

Commercial refrigeration

water cooled

air cooled refrigerant

condenser (၁) Shell and tube ၊ blow-through ၊ horizontal air flow (၂) Shell and coil ၊ draw-through ၊ vertical air flow (၃) Tube in tube ၊ static or forced air flow

႔

Water cooled condenser (၁) Cooling load (၂)

refrigeration

(၃)

cooling water ၏

(၄)

(temperature)

(amount of water)

Shell and tube tube

condenser

chilled water ၊ glycol

Condenser shell ၏ T

႔

heat exchanger

refrigerant

(quality)

(lower portion)

T

subcooler

Air cooled coil auxiliary receiver

coolant

liquid receiver

refrigerant flash gas

Shell

evaporative condenser

႔

cooler

Fan (heat transfer rate)

၇.၂.၁ Condenser building service ႔

chilled water

႔

heat rejection equipment (၁) Air cooled condenser (၂) Water cooled with dry cooler (၃) Water cooled with open cooling tower (၄) Water cooled with closed cooling tower (၅) Evaporative condenser

Refrigeration industry

႔ condenser

(၁) Shell & tube condenser

(၄) Plate heat exchanger condenser

(၂) Evaporative condenser

(၅) Open-type condenser

႔

(၃) Air cooled condenser

Tube in tube

Shell and tube

Shell and coil

Ammonia application

Coaxial

၇-၂ Water cooled condenser 7-3

Chillers and Chilled Water Systems

႔

၇.၃ Water Cooled Condensers Water cooled condenser

(၇-၂)

refrigerating machine condenser

cooling tower

Water cooled condenser chiller

႔

၊

႔

Water cooled condenser (၁)

႔

Water cooled ၍

၊

၍

(heat rejection)

(၂)

႔(pump)

(pipe)

(၃)

) water treatment system

(၄) Cooling tower

condenser water pump

(၅) Cooling tower

condenser water pump

(၆) water cooled condenser (ground water)

႔

refrigerating system

cooling tower ၍

႔

၊

၊

႔

water cooled condenser

Refrigerant

(condenser water) ၍

(waste water)

႔

(recirculating wate)

Waste water

၍

condenser

႔ Recirculating

condenser

cooling tower Condenser

(၃)

(၁) Double type (၂) Shell and tube ၇-၃ Double pipe condensers

(၃) Shell and coil

႔

Double tube type refrigerant ၃)

(၇-

refrigerant ႔ ႔

႔ refrigerant refrigerant

Shell and tube (steel)

steel shell ႔ shell

7-4

refrigerant

tube

႔

Chapter-7 Condensers and Evaporators

tube

႔

tube

႔

႔

၍ velocity

Condenser (၄

႔

capacity 2 tons

100 tons

(၆၀)

5/8"

Shell ၏

(၃

2"

Shell ၏

(၂၀)

Tube

၍ tube

႔

၏

၊

(maintenance) Shell and tube condenser

၇-၄(

) Air cooled condenser

liquid receiver

၇- ၄( ) Open type condenser

၇-၄(ဂ) Evaporative condenser

၇-၅ Shell and tube condenser Shell and coil

shell

coil

Finned tube coil

coil

၍ refrigerant ႔

receiver tank

shell

coil

shell

႔

ဂ

၍ ႔

shell

refrigerant

coil

refrigerant coil

hot gas

compressor (commercial application) ႔

႔

shell shell ၏

႔

(steel)

႔

႔၏ condenser

10 ton capacity

၊ 7-5

Chillers and Chilled Water Systems

႔

၇.၄ Air Cooled Condensers Air cooled condenser

(domestic) ၊

(industrial) refrigerating machine ၍

(commercial)

၊ chilling ၊ freezing

air-conditioning system

air cooled condenser Heat recovery

20 RT

auxiliary ventilation application

centrifugal fan

capacity 3 RT

100 RT

air cooled condenser

Air cooled condenser

(outside air)

႔

refrigerant

refrigerant

120 RT

cooling medium

၍

႔

latent heat

(outside air)

sensible

heat Air cooled condenser

၏

(၁)

(low installation costs)

(၂)

(low maintenance requirements)

(၃)

(freezing)၊ (corrosion)

(scaling)၊

Water piping၊ circulating pump

(၄)

၏

(weather)

၍

(၅) Water cooled condenser

water treatment

႔

႔

air cooled condenser

chiller ၏ (၆) Refrigerant line

system

ဂ

(၇)

refrigerant

(၈)

(low ambient temperatures)

(၉) Air cooled (၁၀)

refrigerant

condenser

႔

refrigeration system

၇-၆(

air cooled condenser

) Water cooled condenser

၇-၆( ) Air cooled condenser

Air cooled condenser air cooled

chiller plant

condenser

refrigerant coil

remote air cooled condenser

400 RT 7-6

finned

centrifugal fan

႔

Air cooled refrigerant condenser 250 RT

Remote

propeller fans

႔

finned refrigerant coil

႔

႔

၏ air cooled chiller

၏

႔

Chapter-7 Condensers and Evaporators

Air cooled chiller (၁)

(water shortage)

(၂) Water cooled equipment (၃) Packaged air cooled

chiller

(machine room)

႔

၊

venting

႔

(၅) Water treatment

႔

Air cooled chiller cooled chiller

(water quality)

၍

၊ monitoring (၄) Cooling tower

႔

water cooled chiller

water cooled

၏ efficiency

chiller

energy efficient

႔၏

Air chiller

system

water cooled chiller

condenser water pump

Air cooled chiller

cooling tower

႔ ၏

part-load performance COP

200 tons

၏ chiller plant

air

cooled chiller ၇.၄.၁ Air Cooled Condenser

၏

(Advantages)

(၁)

(No water requirement)

(၂)

(Standard outdoor installation)

(၃)

(freezing)၊

(၄)

(corrosion problems)

(water piping) ၊

circulation pump

(၅)

water treatment system

႔

(Low installation cost)

(၆)

(Low maintenance and service requirement)

၇.၄.၂ Air Cooled Condenser

၏

(Disadvantages)

(၁) Condensing temperature (၂)

(long piping)

(၃)

cooling capacity

compressor

၍

refrigerant air cooled

condenser

chiller

၏

(power) (၄)

(High noise intensity)

(၅) Air cooled condenser capacity) system

heat rejection capacity

(large cooling

(units)

၇.၄.၃ Application ၊ Selection and Maintenance of Remote Air Cooled Condensers Remote air cooled condenser

Condenser

႔

total heat rejection

(heat rejection)

condensing

pressure 7-7

Chillers and Chilled Water Systems

႔

Air cooled condenser

(remote)

(pressure drop) ဂ Condenser

Cooling

load

evaporator ၏

flashing

(pressure drop)

liquid line

subcooling Condenser

compressor

(gravity)

refrigerant

compressor

႔

Hot gas line (U

)

႔

႔

Condenser ၏ upstream

Air cooled

chiller

check valve

(maintenance)

႔

Coil

refrigerant ၊

ဂ

Air cooled

condenser

efficiency (manufacturer)၏

(guideline)

၇.၄.၄ Air Cooled Condenser Controls Air cooled condenser

compressor refrigerant

Valve(TXV)၏

(pressure drop)

၊ fan

၏

Expansion

၍

air cooled condenser

control Air cooled condenser

control

(၁) Flooded Coil Condenser

(heat transfer surface)

refrigerant

control valve refrigerant

၍

Receiver

(charge)

(၂) Fan Cycling fan ၍

fan

၊

႔

(minimum head pressure)

(၃) Dampers Discharge damper

၍ condenser fan ၏

(air flow)

control

(၄) Variable Speed Fans Fan speed

၍

(air flow)

40°F

system 0°F

fan speed control 7-8

control

႔

damper

႔

fan cycling system

႔

Chapter-7 Condensers and Evaporators

Air cooled condenser

(commercial application) ႔

႔

air cooled condenser Air cooled

condenser

႔

၊ blower

၍

(natural

ventilation)

condensing Plate type condenser

refrigerator ၏

Finned tube condenser Compressor

liquid receiver

refrigerator ၏

႔

႔

condenser Condenser

Compressor head

valve

condenser (၂)

Refrigerant

condenser

Air cooled

႔

႔

၏

႔

(velocity)

capacity

condenser

႔

500

1000 fpm

plant

air cooled

100 Ton

၇.၅ Evaporative condenser ၇.၅.၁ Basic Operating Principles Evaporative condenser

package

condenser refrigerant

heat transfer

(၇-၈)

tube bundle

compressor ႔

Tube

mass transfer

Tube bundle

႔

refrigerant

tube bundle

႔ ႔

႔

receiver vessel

႔

(basin) ႔

၍

Tube bundle

႔

(heat transfer)

႔ ႔

refrigerant ႔

႔

၇.၅.၂ Common Configurations of Condenser evaporative condenser (

) Forced-draft with axial fans

( ) Induced-draft with axial fans (ဂ) Forced-draft with centrifugal fans

႔

၇.၅.၃ Forced-Draft, Axial Fan Condensers ၇-၈(a) (end)

႔

forced-draft axial fan condenser (side)

tube bundle

Fan ႔ 7-9

Chillers and Chilled Water Systems

ၭ

႔

fan (၆)

driven) fan

Fan

E

(belt-

fan

႔

(a) Forced-draft, axial fan condenser

(b) Induced-draft, axial fan condenser ၇-၇ Evaporative condenser

၏

diagram

၇.၅.၄ Induced Draft, Axial Fan Condensers Forced draft axial fan unit

induced draft condenser ႔

Fan

Fan (၄)

fan

Fan fan

gear box

၇.၅.၅ Forced Draft, Centrifugal Fan Condensers Forced draft centrifugal fan condenser ႔

fan

tube bundle ၏

Fan (၈)

Fan

(belt-driven) fan pressure) air flow

Efficiency

system

႔

(highEvaporative cooling cooled fluid

refrigeration

chiller ၏ shell and tube condenser

၇.၆ Evaporative Cooling Evaporative cooling ၏ effectiveness (volume of airflow) Evaporative condenser

၏

air/water

(air entering)၏ wet bulb ႔

(characteristics)

(၁) Circulating (၂) Water treatment system (၃) 7-10

(Reduced space requirement)

၊

႔

Chapter-7 Condensers and Evaporators

(၄)

၊

(၅)

႔

(Small system pumps)

(၆) Capacity (

)

indoor configuration

capacity

cooling tower

၍

water cooled

condenser

circulating water ( )

၊

(ဂ)

႔

(Small system pumps)

(ဃ)

(Indoor locations are possible)

( ) Water treatment ( ) Capacity (

) Cooling tower

၍

shell and tube condenser

air cooled condenser

Evaporative condenser

႔

၊ condenser

Evaporative

၏

closed circuit fluid cooler

၏

၇.၆.၁ Evaporative Condensers Evaporative condenser (water)

water cooled chiller

႔

၏

(air stream) Evaporative

condenser

refrigerant coil Coil

႔

႔

refrigerant vapor ႔

refrigerant vapor

႔ blowdown

႔

၊

drift

႔

evaporative condenser

႔

Evaporative condenser

air cooled

water

cooled condenser ၇-၈ Evaporative condenser Evaporative cooling process ၏ effectiveness

၏ Wet Bulb temperature

Evaporative condenser

water cooled condenser

cooling tower

၍

Spray header (tank)

႔ ႔

၍

႔

႔

၍

blower Condenser

႔ sensible heat

၍ latent heat 7-11

Chillers and Chilled Water Systems

Condenser

႔

refrigerant

႔

႔ ၍

႔

႔

၍

႔

1000 Btu

႔ ၍ ႔

drift eliminator

႔ Condenser

(tank)

႔

၍

၏ plant

Evaporative condenser (၄)ဂ

႔

၍

႔၏

Capacity (၃)ဂ

႔

evaporative condenser

၏

refrigeration

(RT)

႔

၇-၉ Cooling tower ၇.၆.၂ Cooling Towers Cooling tower

evaporative condenser

႔

႔

႔ ၏ wet bulb

၊

Evaporative cooling ၏ effectiveness cooling tower

evaporative cooler

Cooling tower

tower

Condenser water

condenser

cooling

Cooling tower condenser water

(၁) Condenser water (၂)

႔

(loss)

(evaporation loss)

႔

cooling

tower

႔

(drift loss) (၃)

၊ “B

D

”

႔

“D

”

႔

(blow down

loss) ၏ ႔

condenser water

၊

႔

water-

cooling tower Cooling tower

၊

၊

(၇-၁၀)

Tower ၏ Float valve

refrigerant low side float (galvanized iron)၊ Cooling tower

7-12

႔

၊ stainless steel၊

Cooling tower ႔ Air Conditioning and Mechanical Ventilation (Volume One)

႔

Chapter-7 Condensers and Evaporators

၇-၁၀ Cooling tower ၇.၆.၃ Water Cooling Water cooled system ၊

၊

႔

water treatment

filtration

cooling tower

closed circuit evaporative cooler ၇.၆.၄ Capacity Control Water flow ၊ air flow

႔

၏

၍ capacity control

Fan and Pump Cycling Pressure switch ၊

႔

၍

stages)

capacity

၍ pump

control

fan

Capacity

(different

set point

Air Flow Control ႔ 0%

fan

၏

control

100%

VSD

Fan

၏

Resonant frequencies VSD

(two-speed motor)

Water Flow Control (varying water flow

condenser ၏ capacity

control tube

(fouling)

tube

velocity 7-13

Chillers and Chilled Water Systems

႔

၇.၆.၅ Capacity Ratings

Full Load Evaporative condenser

၏ capacity rating

(nominal conditions)

Condensing temperature

၏ Wet Bulb

temperature

correction factor (manufacturer)

correction factor

Part Load Condenser manufacturer

part load performance data

႔

Air flow

condenser capacity A

capacity

႔

heat transfer

႔ performance

၇.၇ Methods of Refrigerant Feed Refrigerant feed

(set-up cost) ၊ operational efficiency

(temperature stability)

႔

Refrigerant feed (၁) Gravity feed operation

႔

surge drum operation

(၂) Pump recirculation operation (flooded operation) (၃) Dry expansion operation (cheapest solution)

႔

Evaporator liquid

႔

၏

refrigerant

႔

refrigerant ၏

evaporator capacity control

Evaporator

႔ refrigerant

(၁)

Recirculated

႔

(၂)

Flooded

(၃)

Direct expansion(DX)

႔ overfeed ႔

၇-၁၁ Recirculated (overfeed) refrigerant transport Refrigerant feed (၁)

(simple)

(၂)

(smaller systems)

(၃) Thermostatic valve (၄) Feron

system

(၅)

(unstable temperature)

(၆) Compressor

႔ refrigerant

၇.၇.၁ Gravity Feed Operation Gravity feed operation (၁) Surge drum 7-14

႔

surge drum operation ၏ low pressure float valve

(risk of liquid carry over)

႔

Chapter-7 Condensers and Evaporators

(၂)

(Relatively stable temperature)

(၃)

(Requires routine oil draining)

၇.၇.၂ Recirculated

႔

Recirculated (LPR)

Overfeed ႔

overfeed system

vessel ႔

-

evaporator coil

recirculated (overfeed) (၃)

႔

(၄)

Coil ႔ ၏ capacity

႔

႔

(၇-

(boil)

“over feed” LPR

(weight)၏ ႔

႔

compressor ၏ solenoid

refrigerant

႔

Refrigerant

refrigerant ႔

low pressure receiver

Low pressure receiver

mechanical pump ၁၁)

liquid refrigerant

control

Recirculated system Solenoid valve

evaporator coil

၊

refrigerant

control

Refrigerant flow through Shell with liquid storage. Used for cooling water only ၇-၁၂(

) Flooded evaporator

၇-၁၂( ) Flooded evaporator

၇-၁၃ Flooded evaporator cut-away ၇.၇.၃ Flooded Evaporator Flooded system

refrigerant

vessel

Accumulator

evaporator coil ၏

refrigerant Evaporator ႔

accumulator evaporator coil

refrigerant compressor

vapor bubble

coil

႔ accumulator

႔ vapor 7-15

Chillers and Chilled Water Systems

Flooded system

႔

pressure regulator

refrigerant

Accumulator

Compressor ၏ suction refrigerant

gas

Refrigerant

refrigerant

၇-၁၄ Flooded evaporator (a) Shell-and-tube. (b) Jacketted. (c) Raceway. Regulator

compressor

refrigerant Regulator

suction pressure

capacity coil

(corresponding temperature)

႔

refrigerant

coolant

(temperature difference)

၇-၁၅(

၇-၁၆( 7-16

) Level master control for flooded chiller

) Flooded evaporator construction detail

၇-၁၅( ) Flooded shell and tube evaporator

၇-၁၆( ) Heat transfer on tube wall

႔

Chapter-7 Condensers and Evaporators

Flooded evaporator ၏ effectiveness temperature)

refrigerant

chiller

(temperature)

(temperature difference) ” difference

၍ ႔

(leaving water ႔၏

“

”

(၇-၁၇)

flood evaporator

႔

“

၏ small temperature

approach temperature

(44°F -

40°F = 4°F)

၇-၁၇ Flood evaporator

၏ small temperature difference ၍ evaporator

Class

႔

approach temperature pressure vessel

Certifying Agent

Design Pressure

Refrigerant

High Pressure

ASME

>15 psig

R-12, 22, 134a, 407C, 410A, 717 (ammonia)

Low Pressure

Manufacturer

< 15 psig

Water, R-11, 123

၇.၇.၄ Direct Expansion (DX) Direct expansion(DX) system evaporator coil evaporator coil

႔

high pressure receiver ႔

refrigerant

superheat temperature

refrigerant flow

thermal

Dx-Evaporator ၇-၁၈ Dry expansion operation

၇-၁၉ Direct-expansion evaporator cut-away (shell-and-tube evaporator) Direct

expansion

evaporator

refrigerant DX coil

(evaporate)

၃၀%

superheated temperature

႔ (evaporate) refrigerant 70% ႔

႔

႔ ႔ 7-17

Chillers and Chilled Water Systems

DX coil

႔

liquid overfeed

flooded coil

fan power

refrigerant flow control

Refrigerant

႔ refrigerant

(flow)

suction line

Compressor

႔ refrigerant

Refrigerant refrigeration capacity

DX coil

(flow)

evaporator efficiency

(၇-၁၉)

direct-expansion (DX) shell-and-tube evaporator

warmer water

refrigerant

Approach temperature

refrigerant

(temperature difference

chilled water

Evaporator ၏ heat transfer efficiency

shell tube

႔ ၊

approach temperature

၇-၂၀ DX Evaporator tube detail DX evaporator

၇-၂၁ DX Evaporator

၏ small temperature difference

flooded evaporator

႔

approach temperature

DX evaporator

saturated evaporator temperature

leaving water

႔

heat exchanger၏ Flooded evaporator

၇-၂၂ DX evaporator

၏ small temperature difference

႔

approach temperature

၇.၈ Evaporator Evaporator

႔ refrigerant Refrigerant

႔

႔

chilled water Evaporator

refrigerant

ၭ chilled water evaporator 7-18

(copper tube)

႔

Chapter-7 Condensers and Evaporators

Water chiller exchanger

၏ evaporator

shell-and-tube

Chiller

refrigerant-to-water heat

၍ tube

refrigerant

Evaporator

႔

chilled water

refrigerant

Chilled water leaving temperature

refrigerant boiling temperature

Refrigerant boiling temperature

(corresponding

pressure)

Air conditioning

expansion (DX) evaporator

Dry expansion evaporator

refrigerant

Flooded evaporator evaporator

refrigerant

refrigerant

Dry expansion (DX) evaporator

DX cooling coil

DX chiller

cooling coil ႔

၍

tube

refrigerant

shell

flooded evaporator

၍

Cooling water

coolant

chiller

Evaporator (၁)

Shell

(၄) Tube support

(၂)

Distribution plate

(၅) Water boxes

(၃)

Tubes

(၆) End sheets

Evaporator

႔

rolled carbon steel plate

Evaporator

၏

chiller capacity

Chiller capacity

design efficiency

evaporator

evaporator ၇.၈.၁ Evaporator (၁)

Air Coolers

(၅) Evaporator Coils

(၂)

Shell & Tube Coolers

(၆) Freezing Drums

(၃)

Plate Heat Exchangers

(၇) Contact Freezing Plates

(၄)

Chilling Plates

(၈) M

……..

Single Pass Arrangement Single pass arrangement

chilled water

Baffle

႔

evaporator

partition

Two Pass Arrangement Two pass arrangement Pass baffle evaporator

tube

(nozzle) tube bundle

evaporator ၏ Chilled water ႔

7-19

Chillers and Chilled Water Systems

႔

Three Pass Arrangement Three pass arrangement nozzle

evaporator ၏

Pass baffle

tube bundle Chilled

evaporator

water

tube

႔ ၇-၂၃ Pass arrangement Evaporator

(nozzle)

(၇-၃၈) water box

box

Marine Waterbox (MWB)

evaporator ၏ shell

“water box”

(leakage)

rubber gasket

(copper tube)

chilled water velocity

(heat transfer)

႔

(pressure drop)

႔

(erosion)

velocity

chilled water pump

Velocity

(heat transfer)

turbulence

laminar

(fouling)

Evaporator evaporator ၊

၊ ၊

ၭ

၊

႔

႔

၊ refrigerant control

၊

၍ Evaporator

၇-၂၄ (

) Bare-tube coils.

၇-၂၅ Plate type evaporator. 7-20

(၁) bare tube (၂) plate surface

( ) Flat zigzag coil

(၃) finned

(ဂ) Oval trombone coil.

၇-၂၆ Standard serpentine plate evaporator.

၍

႔

Chapter-7 Condensers and Evaporators

၏

၍ bare tube coil

၊

ၭ

ၭ ၭ

oval trombone

tube coil

ၭ

႔

flat zigzag

(၇-၂၄-ဂ)

bare

liquid chilling ၍

(ceiling-hurg)

bare coil

storage cooler

centrifugal blower

Evaporator through type

(၁) dry expansion type (၂) forced

(၃) pump circulation type

႔

၇.၈.၂ Dry Expansion Type ၭ ႔

Coil

(V-shape bend)

၍ coil

refrigerant

Capacity

expansion valve

evaporator

coil

refrigerant

၏

႔

(diameter)

၊

fin

႔

႔ defrosting system ၇.၈.၃ Forced Through Type Evaporators dry expansion

႔

fan

၍

evaporator

cool room Evaporator

Refrigeration plant defrosting effect

defrosting system

၇.၈.၄ Pump Circulation Type Evaporators Capacity

evaporator ႔

Evaporator ႔

႔

refrigerant

cold room

refrigerant plant

႔

၇.၉ Evaporator Fan Liquid Cooling ႔ ႔

၊

၊

refrigeration

၊

Evaporator

(၁)

bottle liquids ၊ (၂) liquid under atmospheric pressure Liquid cooled

evaporator

(၃) liquids under pressure

႔

'immersed' evaporator ၍ flooded shell and tube liquid cooler

expansion shell and tube cooler

၍

dry

Flooded shell and tube cooler ၏ 7-21

Chillers and Chilled Water Systems

႔

shell and tube condenser ႔

႔

႔

၍

(coolant)

tube

၏

shell

refrigerant

(level)

control

expansion valve

Refrigerant

(coolant)

႔

႔ (coolant)

refrigerant

tube

႔

႔

႔

႔

tolerance

operating efficiency

႔

refrigerant

oil rectifier Dry expansion shell and tube cooler

၏

tube

refrigerant

shell Refrigerant

(end cover)

evaporator

compressor ႔

compressor

tube

႔

႔

႔ ႔

Flooded type ႔

၊

၊

႔

၇.၁၀ Types of Refrigeration Evaporators (၁) Air coolers

(၅)

Evaporator coils

(၂) Shell & tube coolers (၃) Plate heat exchangers

(၆)

Freezing drums

(၇)

Contact freezing plates

႔

(၄) Chilling plates refrigeration Evaporator

evaporator (construction)၊ refrigerant

evaporator

(direction of circulation of the air)

႔

(method of feeding) ၍

(classified)

၇-၂၇ Air cooler

Plate freezer

Shell & tube evaporator

Evaporator coil

၇.၁၀.၁ Evaporator Refrigeration 7-22

Flake ice unit

Rotary freezer

Welded plate evaporator

၍ air conditioning

(construction)

၍

႔

Chapter-7 Condensers and Evaporators

၇.၁၀.၂ Bare Tube Evaporators Bare tube evaporator (ammonia)

copper tube

႔

refrigerant

evaporator

Ammonia

refrigerant

evaporator

(copper tube) Bare tube evaporator tube evaporator

Bare

liquid chilling ႔

Bare tube evaporator Bare tube evaporator

fin

finned

evaporator

၇.၁၀.၃ Plate Type Evaporators Evaporator coil

copper

႔

aluminum

evaporat ”

(plate)

႔

refrigerant

Plate type evaporator heat transfer

“plate type

၏

Plate type evaporator

႔ ၭ refrigerator)

(household

deep freezer

ၭ

Plate surface evaporator

(metal)

ဂ

refrigerant

(၇-၂၇)

freezer ၭ ၍ T (

ဂ

refrigerant )

၊

၍ cream cabinet

plate (၇-၂၇)

၊

၍

၍

၊ freezer

၊

၊ food display case

၊ ice

႔

၇.၁၀.၄ Finned Evaporators Bare tube evaporator evaporator

fin

Finned

bare tube coil Fin

(metal plate)

coil

႔

(heat transfer)

႔

fin Fin

၏

Fin

႔

Evaporator ၏ Air conditioner cooling coil

finned evaporator ၍

Finned evaporator

႔

cooling coil fin

finned evaporator

႔ finned evaporator 7-23

Chillers and Chilled Water Systems

႔

Evaporator ၏ fin

(heat transfer)

tube

coil

coil ၏

၏ fin

ဂ

(soldered)

၇.၁၀.၅ Shell and Tube Evaporators refrigeration system heat exchanger evaporator

central air conditioning system

evaporator

shell and tube

Chiller

shell and tube

Chiller

refrigerant

refrigerant)

၍ dry expansion chiller

Dry expansion chiller water

(direction of the flow of the tube

Refrigerant

၏

refrigerant

refrigerant

float valve

Table 7-1 tube

shell

chilled

shell

Flooded type evaporator (level)

၍

expansion valve

Flooded type evaporator chilled water

flooded type chiller

material

tube chiller

refrigerant

refrigerant ၏

(thermal resistance)

Material

Thermal Resistance Relative to Copper

Copper

1

Red Brass ( 85% Cu/ 15% Zn)

2.4

Admiralty Brass ( 70%Cu / 28.9%Zn / 1% Sn /0.3 As)

3.1

(90/10) Copper / Nickel ( Copper Nickel)

7.3

(70/30) Copper Nickel ( Copper Nickel)

10.9

Tatanium

18.8

၇.၁၁ Condenser Small Temperature Difference

၇-၂၈ Condenser small temperature difference

႔

Leaving condenser water temperature

refrigerant temperature

(temperature)

small temperature difference

(၇-၂၈)

႔

approach

(100°F-95°F=5°F)

Thermal expansion valve (pressure differential)

7-24

approach temperature

small temperature difference

temperature

feeding

႔

approach temperature difference

over-feeding

(high pressure differential) evaporator coil

under-

႔

Chapter-7 Condensers and Evaporators

၇-၂၉ Limit of vapor compression cycle

Approach Temperature ACMV

ဂ

air con Approach temperature

(၁) Condenser approach temperature (၂) Evaporator approach temperature (၃) Cooling tower approach temperature

႔

Approach temperature Approach temperature

heat t

(heat) temperature) fluid

medium

႔

fluid

႔၏

(high temperature) fluid

႔

႔

(low

(heat t

Approach Temperature Difference (ATD) Approach Temperature Difference (ATD)

၍

fluid ၏

fluid ၏

၍

၇.၁၁.၁ Condenser Approach Temperature Chiller ၏ condenser (heat t

႔ refrigerant ၏

2

refrigerant

Condenser approach temperature condenser

chiller ၏ condenser Table 7-

condenser refrigerant temperature (31.7°C @

leaving condenser water (30.7°C)

- Trane chiller

႔

condenser water ၏

condenser approach temperature

681.2Kpa)

condenser water

၍

ECV6E 56 (HFC 134a)

9:45AM

1° data

Table 7-2 Chilled Water Set Point

6.7°C

Leaving Chilled Water

6.7°C

Entering Chilled Water

10.1

Entering Condenser Water

28.4°C

Laving Condenser Water

30.7°C

Active Control Set Point

100%

Evaporator Ref Pressure

254.2Kpa 7-25

Chillers and Chilled Water Systems

႔

Condenser Ref Pressure

681.2Kpa

Saturated Ref Temp

5.0°C

Condenser Ref Temp

31.7°C

Evaporator Approach Temp

1.7°C

Condenser Approach Temp

1°C

၇.၁၁.၂ Evaporator Approach Temperature Chiller ၏ evaporator t

႔

chiller water Evaporator approach temperature

(leaving) chilled water ၏ Table 7-2 (6.7°C)

refrigerant

evaporator 2°C

(heat

chiller ၏ evaporator

chiller ၏ evaporator

refrigerant ၏

evaporator approach temperature leaving chilled water

evaporator refrigerant temperature (5.0°C @ 254.2Kpa) Chiller

႔

condenser

၍

1.7°

႔၏ approach temperature

chiller

(energy)

leaving chilled water (6.7°C) temperature

2°C

evaporator refrigerant evaporator refrigerant temperature

chiller compressor

၍

Table 7-3 evaporator DX Evaporator

Flooded Evaporator

Hybrid Falling Film Evaporator

Water outside the tubes

Water inside the tubes

Water inside the tubes

Refrigerant inside the tubes

Refrigerant outside the tubes

Refrigerant outside the tubes

Water connection at side

Water connection at ends

Two bundles of water tubes Upper bundle is covered in a film of refrigerant Upper bundle is flooded in the refrigerant

7-26

၇-၃၀ Flooded chiller

၇-၃၁ Dry expansion chiller

၇-၃၂ Evaporator tube bundle

၇-၃၃ Evaporator coil with four fans

႔

Chapter-7 Condensers and Evaporators

၇-၃၄ Recommended piping components for typical evaporator installation

၇.၁၂ Water Box Design Pressure Vessel

၏

(design pressure)

Water box design pressure (static pressure static head

300 psig

႔ Chiller

water box design (

၇-၃၇ Nozzle In Head (NIH)

၇-၃၇ Nozzle In Head (NIH)

႔၏

Dynamic head ႔

၇-၃၅ Vessel

refrigerant

chiller water system

dynamic pressure)

water box design

chiller ၏ duty

150 psig ၍

)

( )

၇-၃၆ Water box

၇-၃၈ Marine Water Box (MWB)

၇-၃၈ Marine Water Box 7-27

7-28

-End-

Evaporative

Water cooled

Air-cooled

Condenser Type

No water consumption No pumping

power input for a given refrigerant

load

Legislative compliance on

pressures (higher COP) Higher summer capacity

Fan and pump power

Higher maintenance costs

Lower condensing

cooling tower components

Water pumping and maintenance Legislative compliance on legionella and other bacteria

environments Highest efficiency due to lowest head pressure

More refrigerant required

Water consumption

Most effective in dry

legionella and other bacteria

Water consumption

More efficient

Water pumping and maintenance

lower COP

Higher head pressures lead to

Disadvantages

Circulating pump plus

environments

Appropriate in humid

No spray drift

No risk of legionella

Advantages

Fan power, higher compressor

Energy Consumption

Table 7-4 condenser types

Chillers and Chilled Water Systems ႔