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Heat exchangers are commonly used in water heaters to prevent freezing
Aug 14, 2020

In order to prevent freezing, the heat exchanger commonly used in solar hot water system adds a plate heat exchanger inside the water tank. The working medium (i.e., the antifreeze liquid) circulates in the circulation loop composed of collector and plate heat exchanger to continuously heat the water in the water tank.


Common heat exchangers are as follows:


As shown in the finned tube or light tube heat exchanger, add one or several tubes in the horizontal or vertical tank. This structure is easy to realize natural circulation, but the heat exchange efficiency is low. Mertol(1981) carried out numerical simulation research on the natural circulation heat exchanger with this structure. He assumed that the heat transfer coefficient U of the heat exchanger was constant, which was equal to 170WM-2K -, Webster(1987) proposed a method to determine the efficiency factor of the new collector. At present, this kind of heat exchanger is seldom used.


Interlayer tank heat exchanger usually has two forms The horizontal interlayer tank heat exchanger is shown, it is usually used in the natural circulation system, improve the inlet position of the working medium, can improve the temperature stratification and system performance of the water tank, but the high inlet position of the working medium will increase the heat loss of upper backflow, and will reduce the circulation velocity of the working medium. (2) The vertical interlayer water tank heat exchanger is shown, it is usually used in the forced circulation system, the inlet position is usually located at the bottom of the interlayer, this structure is easy to realize the temperature stratification of the water tank. If there is an electric heater in the tank, the working medium inlet must be below the position of the electric heater.


This structure of plate heat exchanger is usually put in the vertical tank, with the method of forced circulation, it is advantageous to the water tank temperature stratification, but flow resistance in the heat exchanger is bigger, should not be so use natural circulation such as shown below, this structure heat exchanger and water separation, working medium loop adopts the forced circulation, water cycle with natural circulation and forced circulation.

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