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Fundamentals of Evaporators

written by: Mike Aguilar • edited by: Lamar Stonecypher • updated: 2/22/2010

In this article, fundamentals of the working of an evaporator will be discussed, including their types, and requirement of correct circuit of coils.

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    Introduction

    The evaporator is a component of a refrigeration system in which a refrigerant is heated to remove heat from the environment and transform from a liquid to a gas. Thus, chillers, cooling coils, unit coolers, or the ice cube producer in a home refrigerator can all be categorized as evaporators. In an air conditioner, the evaporator produces cooling, thereby reducing the temperature, and also extraction of latent heat in which moisture is drained out of the air. In both the processes, peaceful environments are created.

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    Types of Evaporators

    Types of evaporators are:

    Flooded Evaporator: It is intended to transmit a steady quantity of liquid refrigerant inside the evaporator, and the amount is sustained by a float valve or other appropriate system. The water is delivered inside the tubes, and an excessive quantity of liquid refrigerant is moved between the shell and tubes.

    Dry Expansion Evaporator: It is planned to control only that volume of refrigerant essentially required by the load. Liquid refrigerant is supplied through an expansion valve in the correct quantity so that all liquid is transformed to gas before the refrigerant arrives at the suction end of the evaporator. It carries water between the tubes and shell. The channel is baffled to amplify the speed and boost heat transfer. The refrigerant moves through the tubes of the chiller. The liquid begins to boil when it enters the tubes, and keeps on boiling as it moves in the tube circuits. The capacity of this evaporator is dependent upon the amount of air being sent through the coil, the temperatures of this air, and the temperature of the refrigerant.

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    Proper Coil Circuiting of Evaporators

    The correct circuit of coils in an evaporator is important, as is having suitable capacity in the evaporator. The proper speed of refrigerant, and the maintenance of the pressure drop within the designed restrictions, can be achieved by separating the stream of refrigerant inside the coil into multiple paths. The speed of the refrigerant should be adequate to rub the walls of the tubes and rupture the layer of liquid refrigerant and oil which is united on the walls. The velocity of refrigerant should be enough to make sure that the oil is traveling constantly, but not so excessively that it creates an extreme drop in pressure, which lowers the capacity of the system.