MECHANICAL ENGINEERING DEPARTMENT
DATE : 28/ 09/ 2017
COURSE CODE: MDB 2063
SECTION A (To be filled by students)
DATE 28/09/2017
EXP # & TITLE REFRIGERATION
GROUP GROUP 26
SECTION B (To be filled by students)
NAME ID TIME IN TIME OUT SIGN
DANIEL AFFENDY AMRI KHAIRUL ANUAR 22714 8.00 AM 10.00 AM
GUO SHEN YEE 22737 8.00 AM 10.00 AM
KAYILASS HARI NAIR MAKENTHERAN 23082 8.00 AM 10.00 AM
LIM BOON KOK 24736 8.00 AM 10.00 AM
SECTION D (by Examiner)
MARKS
ITEM SCORE REMARKS
ALLOCATED
Abstract 10
Objectives 10
Theory & Procedure 10
Data collection 20
Results 20
Conclusions & Discussion 20
Report Format / Style 10
TOTAL 100
INTRODUCTION
The refrigeration cycle in various forms finds applications in industrial and domestic situations. For
example, the storage and transport of perishable foodstuffs and drugs would be extremely difficult if not
impossible without refrigeration. Similarly, the efficient operation of offices and factories in many parts
of the world would be impossible without the use of refrigeration plants in air conditioning systems. It is
for these reasons that engineers of many disciplines must have a good working knowledge of the
refrigeration cycle.
A refrigerator is defined as a machine whose prime function is to remove heat from a low temperature
region. Since the energy extracted cannot be destroyed, it follows that this energy, plus the energy
required to operate the machine, must be rejected to the surroundings at a higher temperature. If the
temperature of rejection is high enough to be useful (e.g. for space or water heating) and this is the
prime object of the machine, then the machine is called a Heat Pump. The most common type of
refrigerator or heat pump operates on the Vapor Compression Cycle and requires a work input.
ABSTRACT
A refrigerator, is a cyclic heat pumping device that uses a working fluid which is also known as a
refrigerant, to transfer heat from a source to sink. Vapor compression refrigeration cycle is being used in
this lab, which consists of four main components: compressor, a condenser, an expansion valve and
evaporator. Firstly, the compressor compresses the refrigerant vapor to raise its temperature and
pressure which is then cooled in the condenser by removing heat into the surrounding medium. The
high pressured, cooled mixture of liquid and gas refrigerant enters the expansion valve where
temperature and pressure will be drastically reduced. Upon going back to the compressor to complete
the refrigeration cycle, the refrigerant enters the evaporator where it will be evaporated due to heat
being absorbed which is the desired output of the experiment.
OBJECTIVE
The main objectives of this experiment were to be able to understand various properties of the
refrigeration cycle using R134a as the refrigerant. Some specific objectives that can be accomplished are
the experimental evaluation of the pressure temperature relationship for R134a refrigerant at
saturation condition, the determination of the volumetric efficiency of the compressor used in the
refrigeration cycle, the determination of heat transfer rates in the condenser and in the evaporator, the
determination of the COP at various operating conditions and the determination of the overall heat
transfer coefficients in the condenser and the evaporator. In addition to that, various heating loads
produced by the evaporator and condenser were investigated to understand how the efficiency of the
refrigeration cycle is affected.
THEORY
Refrigeration is that removes heat in simple term. Refrigeration can be defined as a process of cooling
by transferring heat out of substance. Heat is basically energy. When heat is removed from a substance,
the temperature of a substance is lowered. To accomplish cooling, refrigeration system is called
refrigerant. A commonly used refrigerant is a substance that able to absorb large amount of heat at
relatively low temperature.
A reversed Carnot cycle is a model of an Ideal Refrigeration Unit, which is externally and internally
reversible. Schematic diagram and T-S diagram of the cycle are shown in figure.
Temperature T1 is where the refrigerant leaves the evaporator and enters to a compressor. Th energy
content of the refrigerant increases by the compressor and delivered to a condenser at a high pressure
and temperature T2. The condenser is used for the fluid to cool and returns to the evaporator through
an expansion device. All the expansion and compression units are assumed to be reversible in the cycle.
Process:
1-2 Isentropic compression in the compressor
2-3 Pressure heat rejection in the condenser is constant
3-4 Isentropic expansion
4-1 Pressure heat addition in the evaporator is constant
Energy balance equation for the cycle
Evaporator (WE = 0):
Compressor(q1,2 = 0):
Condenser(WE = 0):
Expansion valve(q3,4 = 0, W3,4 = 0):
Net work done :
Coefficient of performance (Refrigeration):
Coefficient of performance (Heat Pump):
However, the real cycle will hardly as efficient as the bove cycle due to irreversibility in the system. Hence,
a new cycle called simple vapoe compression cycle is substiturted into where we have a throtthling
expansion valve with work input.
PROCEDURE
1. To ensure correct connection of the refrigerant lines and power supply lines, the system is
checked first.
2. The cooling water main shut-off valve is opened and ensure there is no any leakage.
3. The cooling water control valve is opened partially.
4. The main switch is switched on. Wait until the system stabilizers.
5. The required load in the evaporator is set. Wait until the system stabilizes.
6. The reading of temperature, pressure, rational speed, evaporator load etc. is taken and written
in table1.
7. The variable parameter is changed if the system is to be tested for different operation
conditions. Wait for stable readings and repeat step 3 to step 6.
8. The load in the evaporator is relived.
9. The main switch is switched off.
10. The main shut off valve for the cooling water supply is closed.
EXPERIMENT EQUIPMENTS
1. 8 points Digital temperature indicator
2. Digital tachometer
3. Digital wattmeter
4. Cooling water flow meter
5. Refrigerant flow meter
6. Pressure gauge
7. Force meter
8. Thermometer expansion
9. Evaporator heater
