JSS 2 BASIC TECH THIRD TERM Week 3
Topic: PRINCIPLES OF EVAPORATION LEADING TO COOLING BY REFRIGERANTS
Compressor: The refrigerant is a low pressure gas at the evaporator section while it is expected to be a high pressure gas at the condenser side. Therefore, in order to circulate the refrigerant throughout the system, we must provide the means to raise the pressure of the refrigerant from low evaporator pressure to high condenser pressure. This can be achieved by simply using a device called a compressor. The compressor takes the gas at the suction pressure (evaporator pressure) and increases it to the discharge pressure (condenser pressure). In addition to increasing the pressure of the refrigerant gas, the compressor circulates the refrigerant through the system.
Controls: The foundation of the control is to maintain a proper rate of cooling and the temperature of cooled space. There are different methods of achieving control. The capillary tube is one of the most popular. The capillary tube is a tube with small internal diameter and a specific length, which throttles the high-pressure liquid/gas going into the evaporator. This type of control is called the capillary tube refrigerant control. This system is commonly used in household refrigerators, freezer and air conditioners.
Basic Features of a Domestic Refrigerator
A modern domestic refrigerator and a freezer consists primarily of three parts:
(i) The cabinet
(ii) The refrigeration system (condenser, evaporator and compressor);
(iii) The electric circuits.
A typical refrigerator is shown below. While the other figure shows the refrigeration cycle diagram locating the different components whose main functions have already been discussed.
You should endeavour to locate these components in your refrigerator at home, or more easily in scrapped refrigerator. The condenser is a wire type condenser, which uses small metal wires welded to the condenser tubing to achieve rapid cooling. The compressor is what is called a hermetic type. This means that it is completely sealed.
Fig. Household refrigerator
