Training Session of Absorption Chiller

ABSORPTION CHILLER

MAIN EQUIPMENTSAbsorber EvaporatorCondenser First Stage Steam Generator2nd Stage Steam Generator

Dependence on TemperatureDependence on PressureNature of Chemicals

According to Newton’s Law Of cooling, Evaporation causes cooling effect

Evaporation

Operations Cycle of Absorption Chiller

Properties of Lithium bromide and Water

SpongeWater

Wat

er te

mp.

(°C

)

-18

10

38

66

93

121

0 200

400

600

800

1000

Saturation pressure (mm Hg)

Properties of Lithium bromide

• Molecular Formula : LiBr• APPEARANCE: Clear, colorless solution.• ODOUR: Odorless• BOILING POINT: 140°C.• DENSITY OR SPECIFIC GRAVITY: 1.6 g/ml at 25°C.

Pre heater

Pre heater

1st Stage generator

2nd Stage generator

Drain cooler

Absorber

Steam

Dilute Solution

Concentrated solution

Refrigerant cycle

Absorber

Pre heater

Pre heater

Drain cooler

2nd Stage generator1st Stage generator

Condenser

Evaporator

Vapor RefrigerantLiquid RefrigerantSolution

Back

In the evaporator• the refrigerant (water) is

sprayed over the evaporator tubes

• Operates at high vacuum• the refrigerant (water)

evaporates at a temperature of approx. 4°C

• evaporation takes heat from the chilled water in the tubes

Operations cycle - Evaporator

To E1-2582

From E1-2582

Back

In the absorber• the solution (lithium bromide)

is sprayed over the absorber tubes

• the solution is extremely hygroscopic to water vapour

• the solution absorbs the water vapour at a temperature of approx. 35°C

• absorption heat is removed by the cooling water in the tubes, which then flows to the condenser

Absorber

In the solution heat exchangers is heat exchanged between diluted solution from the absorber

(approx. 35°C) and concentrated solution from the low temperature generator (approx. above 80°C) and from the high temperature generator (approx. 130°C)

this improves the efficiency of the cycle

Solution Heat Exchangers

Back

In the high temperature generator• the solution (lithium bromide)

flows around the generator tubes (and flame chamber with YPC-DF)

• the solution is heated up to approx. above 130°C

• refrigerant is driven out and the concentration of the solution is increased

High Temperature Generator (1st stage)

Back

In the low temperature generator• the solution (lithium bromide)

is sprayed over the generator tubes

• the solution is heated up to approx. above 80°C by refrigerant vapour from high temperature generator

• refrigerant is driven out and the concentration of the solution is increased

Low Temperature Generator (2nd stage)

In the condenser• the refrigerant vapour, driven out in the 2nd stage (low temp) generator,

is condensed at a temperature of approx. 40°C• condensing heat is removed by the cooling water in the tubes, coming

from the absorber and flowing to the cooling tower• In addition the refrigerant liquid, condensed in the tubes of the low

temperature generator, is collected here• All refrigerant liquid flows back to the evaporator

Condenser

Back

STARTUP PRECHECKS

• Open cooling water supply & return valves • Open chilled water supply & return valves• Release ESD & confirm power on control panel • Check that no alarm appeared • Check level of absorber, confirm there is no

overflowing• Select local on panel• Check that refrigerant and solution pumps are selected

on auto• Check ready to start indication appearing on panel• Confirm that purge pump has been operated for 5

minutes• Confirm that steam valve on 0% opening• Confirm that condensate drain valve is open and drain

condensate• Remove isolation of steam and press AUTO START

button on panel

START UP

• Push Auto Start button & Observe startup• MPC will confirm startup sequence as follow

1. Chilled water flow Yes2. Cooling Water flow Yes3. Solution & Refrigerant pump selected on Auto Yes4. Solution temperature high No5. Refrigerant low temperature No6. Ist generator high pressure No

• Once all permissive are satisfied, steam control valve will achieve 20% opening from zero .This will cause increase in temperature of LiBr solution

• Solution pump( 15 Kpa Pressure of Ist generator) and refrigerant pump (Solution temperature 37) will simultaneously start on auto

What is Crystallisation and how does it happen?

Crystallization will most likely occur in the Solution Heat Exchanger

The place in the machine

where we have the highest

concentration and lowest

temperature

SYMPTOM

• Refrigeration capacity reduced• Solution level is at lower side • Steam flow is normal ,temperature of diluted

solution returned from absorber decreases gradually

• Pump is rotating ,Solution does not flow • Pump overload relay actuated

CAUSES

• High steam pressure increases Concentration of solution in Ist generator

• Insufficient amount of solution flowing • Excessive amount of steam supplied• Cooling water temperature is too high OR suddenly

decreased • In the event of power failure solution flow is stopped and

counter measure not taken in time• Failure of safety relay• Dilution process is insufficient after operation increased

Concentration

Temperature °C

Spec

ific

Grav

ity

Conc

entra

tion

%

1.85

1.80

1.75

1.70

1.65

1.60

1.55

1.50

0 10 20 30 40 50 60 70 80 90 100

67

66

65

64

62

60

59

57

54

51

50

How to solve?????????

• Perform refrigerant blowing• Start chilled water pump ,Override CW low flow switch Isolate

CW• Set steam control valve to lower level 35%,Stop refrigerant pump• Start The chiller for independent operation of solution pump• Maintain 80 °C in Ist steam generator and then stop for 10

minutes and repeat the process ,Note: Stop solution pump immediately in case of cavitation.

• Increase solution level in absorber ,confirm from sight glass• If de-crystallization is unsuccessful then contact with vendor.

Chilled water suspension

• Insufficient purging of non-condensed gases• Insufficient amount ,strainer chocking OR

suspension of CW• Failure in CW temperature control• Contamination inside tubes of CW

• Failure of chilled water pump• Strainer clogged

High Pressure of Ist Steam Generator

Excessive Refrigeration

• Overload for refrigeration • Chilled water outlet temperature too low• Refrigerant mixed with solution

Recovery procedure

• 1:Faulty stopped due to chilled water suspension OR excessive cooling ,Refrigerant and chilled water may freeze .

• To avoid this immediately stop Solution & Refrigerant pumps, Since dilution operation is not performed Solution may be crystallized if chiller is left in failed condition for and extended period of time .The recovery procedure therefore must be taken as promptly as possible.

• 2:Faulty stop due to other causes• Take recovery procedure as promptly as possible ,Press Stop

button to release the hold state of trouble indication and restart the chiller.

Cooling capacity decreased

Cause Countermeasure

Too high CW Temperature Check CW system OR cooling tower

Insufficient CW flow rate Maintain CW flow, Clean CW strainer

Low steam pressure & flow Check steam control valve opening

Purging trouble Check operation of vacuum pump

Air introduced Retighten the packing parts ,if air intrusion still persist then remove solution & refrigerant from chiller. Charge N2 approximately 0.2Kg/cm2

and conduct bubble testTube contamination of CW side Clean the tubes after draining CW

Cooling capacity decreased

Cause Countermeasure

Refrigerant pollution by solution mixing

Blow refrigerant from refrigerant to absorber by blow off valve

Improper amount of refrigerant OR solution charged

Adjust refrigerant and solution ,If charged amount is insufficient pump produces abnormal sound

Improper solution flow rate Check valve opening & pump

Counter rotating pump Check rotating direction by discharge pressure

Refrigerant overflow Extract refrigerant by performing the purge pump

Clogged steam strainer Clean the steam strainer

Refrigerant overflow

Cause Countermeasure

Too high CW temperature Check cooling water system

Refrigerant overcharging If overflow takes place at full load, The refrigerant may be overcharged Extract the proper amount

Too high steam pressure Flow Adjust steam pressure Flow

Poor Performance Of Vacuum Pump

Cause Countermeasure

Oil contaminated Replace the oil

Rust formed on components such as valves

Clean off rust

Automatic Purge Arrangement

York’s Smart Purge™

YorkMicropanel

Purge Tank

Valve 2

Valve 1

F

E

Purge TankFull

Start PurgePump

OpenValve 1

OpenValve 2

Empty Tank

Add 1 toPurge Counter

M

M

DATA SHEET• Cooling capacity: 550 USRT(refrigeration ton)• Power: 9.4 kW @MRC (3 phase, 400V)• CW Flow: 550 T/h. Temperature in: 32, out: 37 (Passes 1+1, Max

Working Pressure: 8 bar)• CHW flow: 182T/hr, Temperature in: 16.67, Out: 6 (Double pass,

Max working pressure: 8 bar)• Steam: Consumption: 2.5 Tons @4.0bar pressure.• Chemicals: Refrigerant: water, Absorbent: LiBr solution (53% w/w),

Corrosion Inhibitor(LiNO3): Ethyl Hexyl Alcohol (Mass & Heat Transfer Enhancer)

YORK Millennium Panel• Combines the chiller protection functions, optimize the

system efficiency and provides ease of operation.• Following information is provided as standard.1. CHW entering/leaving temperature.2. CW entering/leaving temperature.3. Generator Temperature and pressure.4. Refrigerant and solution temperature.5. Operating hours and number of starts.6. Number of purge cycles (last 7 days)7. Steam control valve position in %age8. Operating indication for refrigerant/solution and purge pumps9. Steam pressure and temperature to generator

Setting of sensors, control switches

• Symbol Description/Function Setting value

• S 01 (1st generator) pressure -760 mm HG to 2kg/cm2 g

• S 02 (High temperature generator) ON: 40 mm Hghigh pressure cut-out OFF: 710 mm Hg

• S 03 measure the inside pressure 0 to 760 mm Hg• S 04 measure the inside pressure - 60 to 60 mm Hg• S 05 Pump starting relay microprocessor• S 06 To end dilution cycle microprocessor• S 07 Chilled water flow switch ON: 0.4 kg/cm2 g

prevent of freezing OFF: 0.3 kg/cm2g evaporator tubes (126M3/H)

Setting of sensors, control switches

• Symbol Description/Function Setting value• S 08 Solution high temperature ON: 165 / 169°C

To protect unit of crystallizations OFF: 165.6 /169°C• S 09 Refrigerant low temperature 1.7 °C

prevent of freezing evaporator tubes• S 10 chilled water low temperature 6°C

control the steam controlvalve and to cycle the unit withlow load conditions

• S 11 Cooling water flow switch ON: 0.4 kg/cm2 gprevent of malfunction of the OFF: 0.3 kg/cm2g

(70%)385M3/H

• S 12 Chilled water return temperature in microprocessor• S 13 Cooling water inlet temperature in microprocessor• S 14 Cooling water outlet temperature in microprocessor