Month: December 2022

Advantages Disadvantages Example 8.1: Carnot refrigeration cycle absorbs heat at 250 K and rejects heat at 300 K. Solution: Given: T1 = 250 K; T2 = 300 K Example 8.2: The capacity of a refrigerator is 150 TR when working between − 5 and 20°C. Determine the mass of ice produced per day from water at 20°C. Also find the power…

In this system, air is taken into the compressor from atmosphere and compressed and then the hot compressed air is cooled in heat exchanger up to the atmospheric temperature. The cooled air is then expanded in an expander. The temperature of the air coming out from the expander is below the atmospheric temperature due to…

Reversed Carnot cycle Reversed Carnot cycle is shown in Figure 8.2. It consists of the following processes. Figure 8.2 P−V and T−S Diagrams for Reversed Carnot Cycle Process a–b: Absorption of heat by the working fluid from refrigerator at constant low temperature TL during isothermal expansion. Process b–c: Isentropic compression of the working fluid with the aid of external work. The temperature of the fluid…

Broadly, the refrigeration systems can be categorized as

Within the refrigeration system, the expansion valve is located at the end of the liquid line, before the evaporator. The high-pressure liquid reaches the expansion valve, having come from the condenser. The valve then reduces the pressure of the refrigerant as it passes through the orifice, which is located inside the valve. On reducing the…

The purpose of the condenser is to extract heat from the refrigerant to the outside air. The condenser is usually installed on the reinforced roof of the building, which enables the transfer of heat. Fans mounted above the condenser unit are used to draw air through the condenser coils. The temperature of the high-pressure vapour…

The purpose of the compressor is to draw the low-temperature, low-pressure vapour from the evaporator via the suction line. Once drawn, the vapour is compressed. When vapour is compressed it rises in temperature. Therefore, the compressor transforms the vapour from a low-temperature vapour to a high-temperature vapour, in turn increasing the pressure. The vapour is…

The purpose of the evaporator is to remove unwanted heat from the product via the liquid refrigerant. The liquid refrigerant contained within the evaporator is boiling at a low pressure. The level of this pressure is determined by two factors:

Clausius statement of the Second Law of Thermodynamics: It is impossible to construct a device that, operating in a cycle, has no effect other than the transfer of heat from a cooler to a hotter body. Thus, the Clausius statement tells us that heat will not flow from cold to hot regions without assistance of outside…