* Types of Evaporators Based on Defrosting and Shape of Construction — Sheet 2

Types of Evaporators Based on Defrosting and Shape of Construction — Sheet 2

Types cooling coil based of frost formation

(a) Frosting type—Used in frozen food cabinets

(b) Defrosting type – Used in fridges. Defrosting was manual in earlier days. Presently it is automatic by using a heater in the evaporator with a timer. Say after every 24 hours, compressors becomes off and heater is on for a fixed period (say ten minutes). The heater goes off and compressor automatically restarts. The evaporator becomes frost free.

(c) Non frosting type – when the evaporator is working above freezing point of water i.e. in water coolers.

Types of Evaporators on shape of construction

(a) Bare tube type –Used in ice plants for cooling of the brine solution.

(b) Plate and tube type – Used in fridges

(c) Finned tube type – Used in window air conditioners and water coolers

(d) Shell and tube type – Used for getting chilled water (between 5-90C) in central air conditioning plants. Chilled water is sent to the various rooms. Each room is having a fan coil unit. In this, chilled water flows through the coil and air is blown over it with a blower. The cooled air cools the room. The hot water returns back to the shell and tube type evaporator. Refrigerant flows through the tubes and water is there in the shell. This type of evaporator is also called WATER CHILLER.

(e) Shell and coil Type — Used in ice plants for the cooling of the brine solution much below 00C.  Sodium chloride solution do not freeze till -290C and calcium chloride brine solution do not freeze till -550C. These solutions are called antifreeze solutions. There are many more anti-freeze solutions. Any one of these can be used as a secondary refrigerant in the ice plant.