Ex.No: Date:
DETERMINATION OF COP OF A
REFRIGERATION SYSTEM
Aim:
To determine the
[i] Theoretical COP, [ii] Experimental COP, [iii] Carnot COP, [iv] Relative COP
on a refrigeration system.
Facilities Required and Procedure:
Description
Vapour compression
cycle is widely used refrigeration cycle. The main object of the trainer is to
demonstrate refrigeration system with basic components and necessary controls.
The practical working is demonstrated in the system and considerable amount of
theoretical analysis and performance can be studied.
The trainer
consists of components of a refrigeration system viz. Hermetically sealed
components, evaporator, condenser, capillary tube. The condenser is air cooled
type for which a condenser fans and motor has been provided. Evaporator is
water immersion type which is housed in a thermally insulated calorimeter.
Calorimeter is provided with an electric heater which can be used for heating
the water initially to be desired temperature.
In addition to
capillary tube a thermostatic expansion valve is also provided. We have to
select either a capillary tube or thermostatic expansion valve at a time. A
toggle switch has been provided to facilitate this selection.
A temperature
indicator with six point selection switch has been provided to get the various
temperature of Freon-12 viz. Compressor suction, compressor discharge after
condenser and after expansion and water temperature.
Special gauges
have been provides for indicating Freon-12 pressure at above mentioned points
except for colorimeter water.
An energy meter
has been provided which indicates the consumption of energy of compressor. An additional energy meter
has been provided to indicate the energy consumption of water heater.
The
students are advised to find out the saturation temperature of F-12 after knowing the pressures at various
points and based on the saturation temperatures study the working of refrigeration considering the
cycle based on
[a] Reversed Carnot cycle,
[b] Simple vapour compression cycle.
Specification:
Compressor: Hermetically sealed
compressor.
Air cooled condenser.
Expansion valve:
(a) Capillary tube. (b) Thermostatic Expansion valve.
Evaporator.
Rota meter: For liquid refrigerant flow
rate.
Refrigerant: Freon-12.
Energy meters for power measurement of
compressor and the fans and heater.
Pressure gauges - 4 Nos. (Two for H.P. and
Two for L.P.)
Temperature indicator.
Solenoid valves.
H.P. / L.P. cut out.
Ammeter, Voltmeter, Thermostat.
c] Procedure for doing the experiment:
Specimen Calculations:
P1 = Pressure of the Condenser
inlet. P2 =
Pressure of the Condenser outlet.
P3 = Pressure of the Cooling
inlet. P4 =
Pressure of the Cooling outlet.
Sensor Meter Reading:
T1 = Temperature of Compression
Outlet T2 = Temperature
of Condenser Outlet
T3 = Temperature of Capillary
Outlet T4 =
Temperature of Cooling Coil Outlet
T5 = Temperature of Cooling Coil
TABULATION:
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S. No. |
Time |
Energy Meter Reading For 10 Rev. in |
Pressure |
Temperature |
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P1 |
P2 |
P3 |
P4 |
T1 |
T2 |
T3 |
T4 |
T5 |
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Formula:
Ø Total Refrigerating effect Q = mCp DT/Dt.
Where, m = Mass of water in kg.
Cp = Specific heat of water = 4.186 KJ/kg.
DT
= Temperature drop in the water.
Ø Theoretical COP = [h1 - h3]/ [h2
– h1]
[Enthalpy is to be found out from the P-h
diagram of R-12]
Where,
h1
= Enthalpy corresponding to pressure P1 and refrigerant entering
temperature at T1°C.
h2 = Enthalpy
corresponding to pressure P2 and refrigerant leveling temperature at
T2°C.
h4 = h3 =
Enthalpy corresponding to pressure P3 and refrigerant temperature
after condensing at T3o C.
Ø Experimental COP = [Actual Refrigeration
Effect/time] / Workdone.
Actual Refrigeration effect/time = mCp DT/Dt.
Where, mw = mass of water in kg.
Cp = Specific heat of water = 4.186 KJ/kg.
DT
= Temperature drop in the water.
Workdone = Energy consumed by the
compressor motor to be found out from the energy meter. Workdone = (10/t) x
(3600/e) x 0.9.
Where, e = Energy meter constant = 1500
rev./kW-hr.
t = Time taken in sec. for 10 revolutions
of energy meter reading.
Experimental COP = mCp DT/Dt
/ workdone.
Ø Carnot COP = TL / [TH - TL]
TL = Lowest Temperature from
table at corresponding to Pmin
Where, Pmin
= [P1 + P4] / 2
bar
TH = Highest Temperature from
table at corresponding to Pmax
Where, Pmax
= [P2 + P3] / 2
bar
Ø Relative COP = Actual COP / Carnot COP
Result:
The COP of the Refrigeration system were
determined and tabulated.
|
Theoretical COP |
Experimental COP (Actual) |
Carnot COP |
Relative COP |
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PO Attainment: |
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Composed By:
R.Satheesh, M.E.,
Asso.Prof.,
