Category: Advance Concept Mechanical Eng

During winter it is essential to heat and humidify the room air for comfort. As shown in Figure 8.11, this is normally done by first sensibly heating the air and then adding water vapour to the air stream through steam nozzles as shown in the figure. Figure 8.11 Heating and Humidification Process Mass balance of water vapour for…

It is defined as the ratio of sensible to total heat transfer rate (Qt), i.e.,   SHF = Qs/ Qt = Qs/(Qs + Q1)   From the above equation, we can observe that a SHF of 1.0 corresponds to no latent heat transfer and a SHF of 0 corresponds to no sensible heat transfer. A SHF of 0.75−0.80 is quite common in…

When moist air is cooled below its dew point by bringing it in contact with a cold surface, some of the water vapour in the air condenses and leaves the air stream as liquid, as a result both the temperature and humidity ratio of air decreases as shown. This is the process air undergoes in…

During this process, the moisture content of air remains constant but its temperature decreases as it passes over a cooling coil. To keep the moisture content constant, the surface of the cooling coil should be dry and its surface temperature should be greater than the dew point temperature (DPT) of air. If the cooling coil…

8.8.1  Psychrometric Chart A view of psychrometric chart is shown in Figure 8.6. The different psychrometric process are shown in Figure 8.7. Figure 8.6 Psychrometric Chart Figure 8.7 Psychrometric Processes

Psychrometry is the study of air–water vapour mixtures. It is also sometimes referred to as hygrometry. Many mechanical engineering devices exploit psychrometric processes, such as air conditioning systems and cooling towers. Two important principles upon which psychrometric relationships are based are the perfect gas equation and Dalton’s law regarding the mixture. The perfect gas equation, PV = RT,…

This is not widely used model. For those who want fresh food selection at eye level, this model is most suitable for their household. The configuration is similar to that of the top mounted freezer refrigerators and the cooling is more even. It does not use much energy to keep the section cool. The main…

This refrigerator is more expensive as compared to the top-mount refrigerator. This is more advanced with features such as through the door cool water dispenser. With the freezer and the fridge being adjacent to each other, it allows easy access to food items that are stored. However, this refrigerator has its own disadvantage. Apart from…

This is the most common type of refrigerator. The refrigerator has wider shelves in both the freezer and fridge. In this refrigerator, the freezer is placed at the top level. Generally, the height of the freezer varies in between 60 and 69 in., which is why they tend to offer more storage capacity as compared…

A refrigerator maintains the temperature slightly higher than the freezing point of the water. There is a freezer which maintains the temperature below the freezing point of water. As far as the classification of refrigerators is concerned, it can be widely classified into four classes. They are top-mount freezer refrigerator, side-by-side refrigerators, freezer on bottom,…