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… Continue reading Condenser
Category: Advance Concept Mechanical Eng
Compressor
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… Continue reading Compressor
Evaporator
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:
REFRIGERATOR AND HEAT PUMP
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… Continue reading REFRIGERATOR AND HEAT PUMP
Multi-pass and Mixed Flow Recuperators
To increase the necessary surface area with a simple tube and annulus arrangement, the length of the tube may be too large for practical purposes. In order to make the heat exchanger more compact, which is desirable from space considerations, and also to reduce the heat loss from the outside surface, it is necessary to… Continue reading Multi-pass and Mixed Flow Recuperators
Cross flow Recuperator
A simple cross flow recuperator is shown in Figure 7.12. The calculation of the mean temperature difference is much more difficult in this case. Θm depends on the ratio of the product of the mass flow and specific heat of fluids A and B, as well as on the ratio of the temperature difference between the fluids at… Continue reading Cross flow Recuperator
Parallel and Counter Flow Heat Exchangers
Consider the case of a fluid flowing through a pipe and exchanging heat with a second fluid flowing through an annulus surrounding the pipe. When the fluids flow in the same direction along the pipe the system is known as parallel flow, and when the fluids flow in opposite directions to each other the system… Continue reading Parallel and Counter Flow Heat Exchangers
HEAT EXCHANGER
Heat exchanger is used to exchange the heat from one fluid to another. In heat exchangers the temperature of each fluid changes as it passes through the exchanger, and hence the temperature of the dividing wall between the fluids also changes along the length of exchanger. Heat exchangers have many applications in engineering such as… Continue reading HEAT EXCHANGER
Heat Transfer Through Sphere
Consider a hollow sphere of internal radius r1 and external radius r2 as shown in Figure 7.8. Let the inside and outside surface temperature be t1 and t2; and let the thermal conductivity be k. Consider a small element of thickness dr at any radius r. It can be shown that the surface area of this spherical element is given by 4πr2. The heat transfer rate Figure 7.8 Heat… Continue reading Heat Transfer Through Sphere
Heat Transfer Through Hollow Cylinder
Consider a cylinder of internal radius r1 and external radius r2 as shown in Figure 7.7. Let the inside and outside temperatures be t1 and t2, respectively. Consider the heat flow through a small element of thickness dr at any radius r, where the temperature is t. Let the thermal conductivity of the material be k, temperature of fluid flow inside the cylinder be tf1, heat transfer coefficient be hf1, temperature… Continue reading Heat Transfer Through Hollow Cylinder