PERFORMANCE TEST ON VAPOUR COMPRESSION REFRIGERATION SYSTEM

Aim:

To conduct a performance test on Refrigeration test rig and to determine the coefficient of performance , Work done , Refrigeration effect produced by the refrigerant Tonnage of system & Plant efficiency.

Apparatus Required:

1. Vapour Compression Refrigeration system Test Rig.

Theory:

Refrigeration systems basically consists of a compressor, condenser, throttling unit and evaporator, all the components connected by tubes to form a closed circuit. Wherein the heat transfer media is called refrigerant circulates in different phases like liquid, vapour and gas. The low pressure refrigerant in vapour phase from the evaporator is sucked and compressed by the compressor and discharged in high pressure & high temperature gas phase the condenser. The condenser condenses the gas phase refrigerant into liquid phase refrigerant and removes the heat from the system and also keeps the pressure in high range itself. The liquid refrigerant phase passes through the filter drier unit and enters rotameter. The rotameter measures the mass flow rate and different load and flow conditions. The high pressure medium temperature liquid refrigerant is allowed through the throttling device viz. usually a capillary in most of the commercial units and expansion valve where the expansion valve is throttled/ cooled to low temperature as well as the pressure is lowered. Thus the low temperature and low pressure vapour refrigerant is enters the evaporator. In the evaporator refrigerant absorbs heat from its surrounded substance and is sucked by the compressor. The cycle is repeated and the refrigeration effect is achieved till the compressor and refrigerant are worked together.

Description of the system:

The equipment is a closed circuit refrigeration test rig withFeron-12 as a working fluid. The high temperature low pressure Freon vapour is sucked by the

compressor, compressed to high temperature high pressure vapour. This vapour is condensed to low temperature high pressure liquid or liquid + gas state by on air cooled condenser. Then it passes through a throttling unit through a silica filter drier which removes the foreign material and moisture if any. Aratometer is fitted before the throttling unit to read the mass flow rate of the Freon directly.

The throttling unit has a standard capillary unit. The low temperature high pressure condensed Freon is throttled to low temperature low pressure liquid by the capillary unit and flows to the evaporator. In the evaporator low temperature low pressure liquid gas boiled by the heat energy of the space / articles stored in it to high temperature low pressure vapour. An accumulator at the end of the evaporator outlet where the liquid Freon will be stored and Freon vapouronly will be allowed to enter compressor. Hp-lpcut out control/save the compressor/ system of the two preset limits of pressures at high (18kgf/cm2 )and the low end of (-0.075kgf/cm2 ).

Precautions:

1. The equipment must have proper “ Earth” point.2. Before energizing the system or starting experimentation hand shut off

valves at the throttling unit must be in open position.3. Since charged with Freon 12 gas and having a number of joints, flare

end connection, the system and must be handled very gently, carefully and smoothly. Unwanted, rough or mishandling must be avoided, or otherwise lead to leakage of Freon gas thereby put the system out of order.

4. Multichannel temperature indicator selector switch knob must handled softly, gently and should not be tampered.

5. Heater control and boiler switch must be put to ‘ON’ only in need and must put to ‘OFF’ immediately after the particular test is over.

6. When the system is not in use , it should be isolated from electrical circuit.

7. Either the capillary unit or thermostatic expansion valve unit must be fully opened, before and after the experimentation. The refrigerant line must not be interrupted by the valves. If so the rota meter may explode.

8. Steam boiler must be kept with required water level, because dry heating will damage the heater immediately.

Procedure:

1. Switch on the refrigeration system mains.2. Switch on the condenser fan.3. Switch on the system.4. Allow the system to run freely to stabilize and note down the readings

as per observation table after steady state condition.

Formulae used:

1. Work done ,(w)

W=(h2-h1) (kj/kg)

2. Refrigerating effect,(qc)

qc=(h1-h4) (kj/kg)

3. Co-efficient of performance,(theoretical)COP th = qc/W

4. Net refrigerating effect ,(Q net)

Q net = m x qc (kj/hr)

Where,

M = Mass flow rate of refrigerant(Kg/hr).

5. Refrigeration capacity, (C)

C = Q/12560 Tones of refrigeration

6. Net work done, (W)

W = (m x w)/3600 (kw)

Where,

W = work done (kj/kg)

7. Input Energy, (E)

E = (x/t) X (3600/1200) (kW)

Where,

X = No. of revelations of compressor energy meter disc.

T = Time taken for ‘x’ revelations of energy meter disc.

8. Co-efficient of performance, (COPactual)

COPactual = Net refrigeration(Q)/Input energy(E) =(kj/hr)/(kj/(sx3600))

9. Co-efficient of performance, (COPTheoritical)

COPTheoritical = Refrigeration effect(qc)/Work done(w)

10. Co-efficient of performance, (COPRelative)

COPRelative = COPactual / COPTheoritical

11. Co-efficient of performance, (COPcarnot)

COPcarnot) = TL / (TH - TL)

12. P lant effiency , (Plant)

Plant = (COPactual / COPcarnot )x 100 (%)

Result:

Thus the performance test on closed circuit vapour compression refrigeration system has been carried out and the results are tabulated below.

Sl.

No.

Net work

done (W)

Net

Refrigeration

effect (Q)

COP

(actual)

COP

(theoretical)

COP

(relative)

COP

(Carnot)

Refrigeration

capacity(C)

Plant

effiency

(kW) (kW) (TR) (%)

INFERENCE: