Placement of Evaporator in Cold store
PLACEMENT OF COILS
Decisions about the number of coils, their locations in the refrigerated space,and the directions of air discharge are interrelated and influenced by room geometry, ceiling arrangement, and product placement. The sum of the refrigeration capacities of the coils must equal or exceed the design refrigeration load, but the number of coils into which the total capacity is divided is a compromise.A small number of large coils usually results in the lowest first ost (and lowest maintenance cost) because of the reduction in piping, valves,and controls for the coils.
On the other hand, distribution of the total capacity into a large number of coils helps avoid pockets of high temperature in the space. The goal of achieving uniform temperatures is dominant in the selection of the number of coils and their placement. Several guidelines frequently used by system designers include:
- Select the coils and place them on the basis of a throw of 30 to 60 m (100
- to 200 ft)
- blow the discharge air in the same orientation as the beams
- blow across doors and not away or toward them (Fig. 6.39)
- direct the discharge air down aisles
- direct the discharge air downward from ceiling coils in high-rise storage
- facilities
Sometimes, discharge air is ducted from the coil to convey it further, but most coils probably discharge directly into the space. There is a danger of ducts in low-temperature spaces becoming frosted without any automatic means of defrost. Coils are occasionally mounted near the floor for easy servicing (Fig. 6.40), and the air ducted to the ceiling. Dampers should be installed in the duct, and should close during defrost. Otherwise, the warm coil creates a chimney effect that retards the defrost rate. One of the situations where the floor-mounted.
unit would be considered is when coils are being installed in an existing facility where the roof structure may not be able to accommodate the weight of ceiling hung or rooftop units.
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