Evaporators Coils

The term refrigeration refers to the gas coming into contact with evaporator coils on a dx vapor-compression cycle, coils on an absorption cycle, vortex... 

Where an evaporator coil is divided into a number of parallel passes, a distribution device with a small pressure loss is used to ensure equal flowthrough each pass. Pressure drops of 1-2 bar are common. There will nowbe a much larger finite difference between the pressure under the diaphragm and that at the coil inlet. To correct for this, the body of the valve is modified to accommodate a middle chamber and an equalizing connection which is taken to the coil outlet, close to the phial position. Most thermostatic expansion valves will have provision for an external equalizer connection (see Figure 8.8). 

Dairy farms have bulk-storage tanks with their own refrigeration plants. These are usually made in the form of a double-skin, insulated tank, having the evaporator coils in the jacket, which also contains water. The refrigeration system runs throughout the 24 hours and... 

Trays of product to be frozen can be loaded onto trollies, which are taken through an air blast tunnel. The evaporator coils will usually be in the upper part of the tunnel, with air flow across the trays. 

There will also be a gain in usage of the evaporator coil and a corresponding rise in the evaporator temperature, giving a further increase in compressor capacity. This would need to be evaluated from the compressor curves, but might be a further 1%. 

This first estimate for the evaporator coil performance must now he corrected for the change in compressor duty if it is a direct expansion coil, or of water temperature change if using chilled water. Another method is to re-calculate the basic rating figures at the new air flows and plot these against compressor curves. 

Moist warm air from the stacks is drawn through the evaporator coils and is cooled until the absolute humidity of the air corresponds to the absolute humidity at saturation (Table 8.1), the dew point. On further cooling moisture condenses on the cold evaporator coils. This water is collected and drained from the kiln. The cold air then passes through the warm condenser coils where it is reheated. The dry warm air then passes through the timber stacks again. 

Another disadvantage of the conventional approach is that the air leaving the evaporator coil is nearly saturated, with a relative humidity typically above 90%. This moist air travels through duct work until the air either is mixed with dryer air or reaches the reheat unit. The damp ducts, along with wet evaporator coils and standing water in a condensate collection pan (Fig. 4), foster problems with microbial growth and the associated problems of health and odor. 

FIGURE 7.13. Tungsten evaporation coils for thin-film technology. By courtesy of Plansee AG, Austria. 

Evaporator coil- The part of a cooling system that absorbs heat from air in your home. Also see condensing unit. 

Evaporator Coil - The inner coii in a heat pump that, during the cooiing mode, absorbs heat from the inside air and boils the liquid refrigerant to a vapor, which coois the house. 

Expansion Valve - The device that reduces the pressure of liquid refrigerant thereby cooling it before it enters the evaporator coil in a heat pump. 

Another point worth mentioning is that as the warm air flows over the evaporator section of an air-conditioning unit, and as the air cools, the moisture (the vraier wipor) in the air condenses on the outside of the evaporator coil. The condensation forming on the outside of the evaporator is eventually drained. Thus, the evaporator acts as a dehumidificadon device as well. This process is similar to what happens when hot, humid air comes into contact with a g ass of ice water. You have all seen the condensation that forms on the outside surface of a g ass of ice water as the ndg boring hot, humid air cools down. We will discuss what we mean by absolute and relative humidity in Chapter 17. 

Air Handler Device that blows air across a split-unit central air-conditioning evaporator coil into the air ducts of a building. 

The evaporator coils in my attic were also leaking. The condensate collection pan had not drained freely for the past five years. Condensate had backed up and submerged the bottom tube of the evaporator and caused the tube to corrode and leak freon. 

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