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9.2.1.1 Evaporator
The liquid refrigerant evaporates at low pressure in the evaporator. During evaporation, liquid refrigerant accumulates latent heat from the surroundings. Evaporation
is an isothermal process. A heat exchanger fluid (air/water) is flown to the evaporator
coil for efficient cooling. Most of the evaporator is followed by an auxiliary circuit
for superheating the vapour which ensures that the liquid refrigerant is completely
evaporated before leaving the evaporator. Superheating prevents the damage of the
compressor and increases the efficiency of the system.
9.2.1.2 Compressor
Vapour refrigerant is fed into the suction line of the compressor and compressed until
the condenser pressure. The compression process of an ideal compressor is isentropic.
However, in practice, there is no idea compressor. Hence, the compression is nonisentropic. According to Gay-Lussac’s gas law, the temperature increases during the
compression. Modern compressors are variable in speed and electricity consumption
is very low.
9.2.1.3 Condenser
Hot vapour refrigerant discharges from compressor outlet and flows through the
condenser coil. The coil has fins, and the air is flown for faster heat transfer. Heat
is released from the refrigerant to the surroundings and gets liquefied. Released
refrigerant from the condenser is passed through an additional circuit which subcools
the liquid refrigerant to ensure that all the refrigerant is in the liquid state before
entering expansion device.
9.2.1.4 Expansion Device
The high-pressure liquid refrigerant is forced through a small orifice of the expansion valve, which causes a sudden pressure and temperature drop. Refrigerant is in
two-phase condition after the expansion device. This refrigerant reenters into the
evaporator and the cycle continues to repeat.
9.2.2 Solar Cooling
Unlike the VCR system, work input of a solar cooling system is thermal energy
instead of electricity. The mechanical compressor of a VCR is replaced with a
thermal compressor, namely adsorption bed (Sayigh and McVeigh 1992; Chang
Md. A. Islam and B. B. Saha
9.2.1.1 Evaporator
The liquid refrigerant evaporates at low pressure in the evaporator. During evaporation, liquid refrigerant accumulates latent heat from the surroundings. Evaporation
is an isothermal process. A heat exchanger fluid (air/water) is flown to the evaporator
coil for efficient cooling. Most of the evaporator is followed by an auxiliary circuit
for superheating the vapour which ensures that the liquid refrigerant is completely
evaporated before leaving the evaporator. Superheating prevents the damage of the
compressor and increases the efficiency of the system.
9.2.1.2 Compressor
Vapour refrigerant is fed into the suction line of the compressor and compressed until
the condenser pressure. The compression process of an ideal compressor is isentropic.
However, in practice, there is no idea compressor. Hence, the compression is nonisentropic. According to Gay-Lussac’s gas law, the temperature increases during the
compression. Modern compressors are variable in speed and electricity consumption
is very low.
9.2.1.3 Condenser
Hot vapour refrigerant discharges from compressor outlet and flows through the
condenser coil. The coil has fins, and the air is flown for faster heat transfer. Heat
is released from the refrigerant to the surroundings and gets liquefied. Released
refrigerant from the condenser is passed through an additional circuit which subcools
the liquid refrigerant to ensure that all the refrigerant is in the liquid state before
entering expansion device.
9.2.1.4 Expansion Device
The high-pressure liquid refrigerant is forced through a small orifice of the expansion valve, which causes a sudden pressure and temperature drop. Refrigerant is in
two-phase condition after the expansion device. This refrigerant reenters into the
evaporator and the cycle continues to repeat.
9.2.2 Solar Cooling
Unlike the VCR system, work input of a solar cooling system is thermal energy
instead of electricity. The mechanical compressor of a VCR is replaced with a
thermal compressor, namely adsorption bed (Sayigh and McVeigh 1992; Chang