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The Bell-Coleman air refrigeration cycle was developed by Bell-Coleman and Light Foot by reversing the Joule’s or Brayton’s air cycle. The schematic diagram of such a cycle is shown in Fig. 18.8. It consists of a compressor, a cooler, an expander, and a refrigerator. The p-v and T-s diagrams are shown in Fig. 18.9. Figure 18.8 Schematic diagram of Bell-Coleman air refrigeration…

A reversed Carnot cycle, using air as working medium is shown in Fig. 18.5 on p-v and T-s diagrams. The reversed Carnot cycle is represented by four processes as described below: Heat absorbed by air (or heat extracted from cold body) per kg of air. q4−1 = are 4-1-2′-3′ =T4 (s1 − s4)=T4 (s2 − s3)=T1 (s2 − s3) Work done during the cycle per kg of air, wcycle = q2−3 − q4−1 = are 1-2-3-4 = T2 (s2 − s3)…

There are two types of air refrigeration cycles. 1 Open Air Refrigeration Cycle In an open air refrigeration cycle, the air is directly (at atmospheric pressure) led to the space to be cooled (i.e. refrigerator). The air is then allowed to circulate through the cooler and returned to the compressor to start another cycle. This…

The power consumption of a refrigerating machine is determined in terms of kW. However the power consumption of the driving motor is sometimes rated in horsepower (H.P). we have where Wref is in kW and HP is in metric units, where Q1 = refrigerating capacity in kW Since 1 TR = 3.5167 kW, therefore Example 18.4 The ambient air temperature during…

Heat Engine: In a heat engine, as shown in Fig. 18.4(a), the heat supplied to the engine is converted into useful work. If Q2 is the heat supplied to the engine and Q1 is the heat rejected from the engine, then the net work done by the engine is given by,   We =Q2 −Q1 Efficiency of heat engine, Refrigerator: A refrigerator is an…

The reversed Carnot cycle is shown in Fig. 18.3 on p-v and T-s. diagrams. The sequence of operations is given below: The Carnot cycle is practically not feasible since isothermal energy rejection requires extremely slow motion followed by isentropic process during which the piston should move at extremely faster rate, which is mechanically not obtainable. The COP of reversed Carnot…

During evaporation, the liquid-vapour refrigerant absorbs its latent heat of vapourisation from the medium (air, water, brine) which is to be cooled. This heat which is absorbed by the refrigerant is called the refrigeration effect. In other words, the refrigeration effect is the amount of cooling produced.   Refrigeration effect = Enthalpy of vapour refrigerant…

The capacity of a refrigeration unit is given in tons of refrigeration. A ton of refrigeration is defined as the quantity of heat to be removed in order to form one ton of ice in 24 hours when the initial temperature of water is 0°C. 1 ton of refrigeration, TR = 211 kJ/min or 3.5167 kW. Taking…

The methods of refrigeration are: 1 Vapour Compression Refrigeration System The schematic diagram of simple vapour compression refrigeration system is shown in Fig. 18.1. It consists of the following five essential parts: Note: In any compression refrigeration system, there are two different pressure conditions. One is called the high pressure side and other is known as low pressure side. The high…

A refrigeration system is a device to produce the refrigeration effect. Some of the popular refrigeration systems are: