1. Refrigeration and Air Conditioning
Basic Principles
Machineries
Plant Diagnostic
Air Conditioning
Cargo Refrigeration
Environmental Matters

2. Key Factors Coefficient of Performance Capacity Control
Refrigeration Effect

3. LEGEND High press Low press Liquid vapour mixture
Direct expansion evaporator
Vapour
Expansion valve
Seawater
out
Liquid
Oil separator
Receiver with gauge glass
Refrigeration compressor
Condenser
Seawater in
Oil return to sump

4. Meat room
at -18oC
Heat energy E1 at low temp.
being passed to refrigerant
Energy E3 thrown out to sea
Compression
energy E2

5. + = Heat energy E1 at low temp. Compression energy E2
Energy E3 thrown out to sea + =
WASTE ENERGY TO SEA
OUR OBJECTIVE
WE NEED TO SPEND THIS

6. Coefficient of Performance
COP is ratio of
Energy Extracted E1over
Energy Spent E2

7. COP Energy Extracted = 304 -150 = 154kJ/kg
Energy Spent = = 61 kJ/kg
COP = 154 / 61 = 2.52

8. Capacity Control Constant Pressure = Supply to Evaporator =
Constant Temperature
Supply to Evaporator =
Removal
Quantity of refrigerant α Load

9. Back pressure valve Suction line of warmer evaporator
Pressure higher ; thus higher temperature

10. Control Methods Start /Stop Speed Several compressors in parallel
Bypass hot gas
Unloading (reciprocating)
Throttle suction (centrifugal)
Slide valve (screw)

11. Safety Spring
Delivery Valve
Suction Valve
Unloader pin

13. to unload Capacity Reduction Gear Suction valve Push rod Moving ring
Operating rod
Oil servo: manual or auto
Capacity Reduction Gear
to unload

14. Throttling Devices Maintain pressure difference
Meter correct amount for varying load
Reduce boiling point by reducing pressure

15. Refrigerating Effect Depends on:
Refrigerant mass circulated per unit time
Refrigerating effect per unit mass circulated

18. AUTOMATIC EXPANSION VALVE
Adjusting screw to alter spring pressure
Refrigerant
OUT
Spring Pressure
- Opening
Action
Spring
Diaphragm
Throttling orifice
Refrigerant Pressure
- Closing Action
Refrigerant
Refrigerant (liquid) IN
EVAPORATOR

19. THERMOSTATIC EXPANSION VALVE (TEV) (internally equalised)
Refrigerant (slightly superheated gas)
OUT
Refrigerant
Remote bulb
Diaphragm
Throttling orifice
Refrigerant
Spring
Adjusting
screw to alter spring
pressure
Refrigerant (liquid) IN
EVAPORATOR

20. THERMOSTATIC EXPANSION VALVE (TEV) (externally equalised)
To overcome this problem, an externally equalised thermostatic
Refrigerant (slightly superheated gas)
OUT
Diaphragm
Throttling orifice
Equalising connection
Refrigerant
Spring
Remote bulb
Adjusting
screw to alter spring
pressure
Refrigerant (liquid) IN

21. Desirable properties of refrigerant
HIGH
Latent heat of evaporation
smaller mass flow for same effect
Specific heat at liquid state
less flash gas
LOW
Specific volume
smaller piping, compressor
Low compression ratio
lower pressure required
Specific heat at vapour state
less surface for superheat

22. Above saturated vapour or super-heated region
Pressure
(bar)
Vapour to Liquid
transformation in
CONDENSER
Enthalpy
(kJ per kg of refrigerant)
Saturated liquid line
Below saturated
liquid or
sub-cooled
region
Saturated vapour line
Above saturated vapour or
super-heated region
Liquid to vapour
transformation in
EVAPORATOR

24. Superheating

25. Subcooling