Basics Overview of Vapour Absorption Machine.pptx

Basics Overview of Refrigeration System
Prepared By:
AMIYA KUMAR SAMAL
Thermax Limited
Power O & M

Energy | Environment | Chemical www.thermaxglobal.com
Safety and Environment Oath
I will set excellent safety standards by adhering to safety norms,
reporting hazards and taking prompt actions to prevent
accidents.
I will do my share to preserve the planet’s future by conserving
resources and minimizing carbon footprint through reduce,
reuse and recycle.

Refrigeration System
Refrigeration:
Producing and maintaining a temperature below that of the surrounding
atmosphere.
Mostly use Vapour Compression Refrigeration technology built upon the
Thermodynamic principles of the Reverse Carnot Cycle.

Why We Require Refrigeration
Since heat cannot flow from low temperature reservoir to high
temperature reservoir on its own, external work is required to achieve
refrigeration.
Removal/Transfer of heat from source to sink by performing an external
work; even a body @ -272*C has one more degree of heat energy to be
removed to achieve absolute zero (i.e.), 0*K (or) -273*C

Types of Refrigeration System
Refrigeration
System
Natural
Mechanical
Gas
Refrigerators
Vapour
Refrigerators

Types of Refrigeration System
Vapour Refrigeration
System
Vapour
Compression
Screw Chiller
Centrifugal
Chiller
Reciprocating
Chiller
Vapour
Absorption
Lithium
Bromide
Ammonia

Range & Uses of Refrigeration System
• Capacity = 25 – 300 TR
• Any Temperature
Screw Chiller
• Capacity > 300 TR
• Temperature > 0 Degree C
Centrifugal Chiller
• Low Capacity < 100 TR
• Any Temperature
Reciprocating Chiller
• Good COP & Capacity = 10 – 3500 TR
• Temperature > 0 Degree C
Lithium Bromide
• Low COP & Custom Built
• Sub Zero Application
Ammonia

Ton of Refrigeration
Tons of Refrigeration :
Rate at which heat has to be removed from 1 US ton of Water (907 kg)
at 0 Degree C to get 1 US ton of Ice at 0 Degree C in 24 Hours
Commonly used unit to express refrigeration capacity
Unit Conversion:
1 USRT = 3024 kCal/Hr = 3.51628 kW

Refrigerant
Working Substance
Primary and Secondary refrigerants.
Primary refrigerants are those fluids, which are used directly as working fluids.
Ex.-refrigerant used in VCC and VAR systems.
These fluids provide refrigeration by undergoing a phase change process in the
evaporator.
Secondary refrigerants are those liquids, which are used for transporting
thermal energy from one location to other.
Secondary refrigerants are also known under the name brines or antifreezes.

Primary Refrigerant
The refrigerants which are directly used to obtain the cooling effect in
evaporator by undergoing a phase change process are referred as Primary
refrigerants.
Halocarbon Refrigerants
Azeotropes Refrigerants
Inorganic Refrigerants
Hydro-carbon Refrigerants

Secondary Refrigerant
 Used for transporting thermal energy from one location to other.
 Does not undergo phase change process.
 Used when refrigeration is required at sub-zero temperatures.
 Known as Brines or Antifreezes.
 Used in large refrigeration units.
 Commonly used secondary refrigerants are:-
Solution of water & ethylene glycol, propylene glycol etc.
 If working temperature is above 30C, Water is used as SR.
 Brine is aqueous solution of NaCl and CaCl2 in water and used at temperature below freezing
point of water 00C.
 It is Used in cooling of fish, meat & ice plant.
 Ethylene glycol & Propylene glycol mixes with water and gives colorless & odourless solutions.
 These have capacity to lower freezing temperatures and hence used as antifreeze mixtures for
I.C. engine cooling systems.
 These solutions become corrosive after some use, hence corrosive treatment is necessary.

Advantages of Secondary Refrigerant
Different rooms of building can be cooled up to different temperatures by adjusting the flow rates
of secondary refrigerants.
SR can be easily handled.
SR can be easily controlled.
Eliminates long refrigeration lines and thus reduces pressure drops.

Properties of Secondary Refrigerant
Low Freezing Point.
High Heat Transfer Coefficients.
High Specific Heat.
Low Vapour Pressure.
Good Stability.
Non-Flammable and Non-Toxic.

Thermodynamic & Thermo-physical PPT
The requirements are:
a) Suction pressure:
At a given evaporator temperature, the saturation pressure should be above atmospheric
for prevention of air or moisture ingress into the system and ease of leak detection.
Higher suction pressure is better as it leads to smaller compressor displacement.
b) Discharge pressure:
At a given condenser temperature, the discharge pressure should be as small as possible
to allow light-weight construction of compressor, condenser etc.
c) Pressure ratio:
Should be as small as possible for high volumetric efficiency and low power
consumption.

d) Latent Heat of Vaporization:
Should be as large as possible so that the required mass flow rate per unit cooling capacity will be
small.
e) Isentropic Index of Compression:
Should be as small as possible so that the temperature rise during compression will be small.
f) Liquid Specific Heat:
Should be small so that degree of sub cooling will be large leading to smaller amount of flash gas
at evaporator inlet.
g) Vapour Specific Heat:
Should be large so that the degree of superheating will be

h) Thermal conductivity:
Thermal conductivity in both liquid as well as vapour phase should be high for higher heat
transfer coefficients .
i) Viscosity:
Viscosity should be small in both liquid and Vapour phases for smaller frictional pressure
drops.
The thermodynamic properties are interrelated and mainly depend on normal boiling point,
critical temperature, molecular weight and structure.

Ammonia as Refrigerant
1. A Natural Refrigerant
Ammonia is produced in a natural way by human beings and animals.
2. 17 grams/day for humans.
3. ODP = 0 and GWP = 0
4. Excellent thermodynamic characteristics: small molecular mass, large latent heat, large
Vapour density and excellent heat transfer characteristics.
5. High critical temperature (132C) : highly efficient cycles at high condensing
temperatures
6. Its smell causes leaks to be detected and fixed before reaching dangerous concentration
7. Relatively Low price

Drawbacks of Ammonia as Refrigerant
1. Toxic
2. Flammable ( 16 – 28% concentration )
3. Not compatible with copper
4. Temperature on discharge side of compressor is higher compared to other
refrigerants

PHE Check-List/Maintenance
1. Make sure that the operating conditions (temperatures and flow rates) comply with the design
specifications.
2. At start-up, vent the heat exchanger but open and close the valves slowly to avoid pressure
surges and water hammer.
3. Use upstream filters and strainers to remove particulate fouling and protect the heat
exchanger.
4. On a daily basis check for any changes in temperature or pressure and check for any signs of
external leaks.
5. On a regular basis keep the tightening bolts clean and well-lubricated.
6. Use condition monitoring techniques to avoid having to open the gasketed plate heat
exchanger for inspection.
7. Use Cleaning-In-Place (CIP) to avoid the need to open the heat exchanger for cleaning.
8. Always keep stand-by units clean and dry. If a heat exchanger is taken out of service, flush with
fresh water and drain it completely.
9. Protect heat exchangers from water splash and rain. Avoid exposure to ultra violet rays and
ozone typically generated from electrical sources.

Vapour Compression System Process &
Main Components
Parts & Process involved:
1. Evaporator : Refrigerant Vaporization
2. Compressor : Refrigerant (Vapour Phase)
Compression
3. Condenser : Refrigerant (Vapour to Liquid)
4. Expansion Valve : Pressure Reducer / Throttling Valve
To help refrigerant achieve the required
Temperature

Vapour Compression Operation Principle

Troubleshooting Procedure
S N Problem Details Probable Reasons Remedial Action
1 PLC Panel Don’t Start Main Power Supply OFF Switch ON Main Supply
MCB in OFF Condition Switch ON MCB
2 CHW O/L Not Achieved Flow or Load is very high Reduce CHW Flow/Load
SCV not opening as per requirement Check Inst. Air Pressure & Max Opening Limit
Low Steam/HW Press/Flow/Temp Check Steam/HW Side Utility
Insufficient Vacuum Perform Purging
High CW I/L Temp Check CT Fan Operation
Low CW Flow Clean Strainer & Check Pump/Motor
3 CHW Temp rising day by
day
Fouling of CHW/CW Tubes Clean the tubes
Mixing of LiBr with Refrigerant Perform Refrigerant Blow down
Insufficient Octyl Alcohol Charge Octyl Alcohol as advised
Air Leakage in M/C Perform N2 Leak Test
Insufficient Corrosion Inhibitor Analyse LiBr Sample

Troubleshooting Procedure
S N Problem Details Probable Reasons Remedial Action
1 Large Fluctuation in
CHW O/L Temp
Variation in CHW Flow Check Strainer, Pump, Motor
Variation in Cooling Load Maintain constant load
Incorrect Setting of PID Values Check PID value settings or consult OEM
Frequent On/Off of Ref Pump Check Ref level & Ref Electrode
2 Tripping of Pump
Interlock, Flow Switch,
DP Switch, Pressure
Switch
Variation in Pump Flow/Pressure,
Instrument Air Press, Settings
Rectify the same & maintain as per OEM
3 Ref/Abs/Purge Pump
Trip
OLR Settings Issue/Malfunctioning Reset with help of OEM
Variation in power Supply Check Ampere of Pump & maintain
Severe Crystallization Decryastallize
High TRG reading Check & Replace Bearing

THANK YOU

Basics Overview of Vapour Absorption Machine.pptx

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Basics Overview of Vapour Absorption Machine.pptx