Three-media evaporator for a cooling unit

Abstract

A three-media evaporator for a cooling unit utilizing the vapor compression refrigeration cycle. The apparatus includes a number of heat exchange tubes, each tube including an inner heat exchange tube adapted to carry a primary heat exchange medium and an outer heat exchange tube, adapted to carry an intermediate heat exchange medium. The intermediate heat exchange medium is in thermal communication with the primary heat exchange medium. A direct heat exchange mechanism, which in one aspect can be a set of fins, is in simultaneous thermal communication with the ambient medium and with the intermediate heat exchange medium. In each heat exchange tube the outer tube at least partially surround the inner tube, defining an annular space between the tubes. The intermediate medium is carried in the annular space.

Description

FIELD OF THE INVENTION[0001]The present disclosure deals generally with heat exchange devices, and more specifically with evaporative cooling devices.BACKGROUND OF THE INVENTION[0002]Vapor compression refrigeration cycles are widely used in many cooling systems, including refrigerators, air-conditioning systems, industrial and commercial refrigeration systems and the like. The process of refrigeration refers to extracting heat from a space and rejecting it somewhere else, thus lowering the temperature of the space. Vapor compression refrigeration cycles use a refrigerant for this process. The cycle includes four basic components: a compressor, a condenser, an expansion valve and an evaporator. The circulating refrigerant enters the compressor in the form of saturated vapor and undergoes isentropic compression, thus increasing its pressure and temperature, and converting into a superheated vapor. The refrigerant in the superheated vapor form is now in a state where it can be condense...

AI Technical Summary

Benefits of technology

[0011]A flow control means changes the mass flow rate of the refrigerant at the refrigerant inlet when any change in the temperature of the fluid at the fluid outlet is observed. Changing the mass flow rate of the refrigerant ensures that the rate of heat gained by the refrigerant complies with the rate of heat required by it for its complete vaporization.

Problems solved by technology

Ensuring the complete vaporization of the refrigerant at the outlet of the evaporator of a cooling unit utilizing vapor compression refrigeration cycle presents a difficult task, as the process occurs at constant saturation temperature and pressure of the refrigerant.

In situations where considerable variations exist in the temperature of the air at the inlet to the evaporator, sufficient latent heat of vaporization may not be provided to the refrigerant to completely vaporize it.

This problem becomes more difficult if the cooling unit is installed to condition outdoor fresh air.

If the design allows a fraction of the refrigerant to enter the compressor in liquid form, that liquid may considerably affect compressor performance, and that condition may also lead to partial or complete damage of the compressor's mechanical parts.

As outside air temperature changes during the day, the water loses or gains sensible heat, and those changes affect the ability of water to transfer heat to the refrigerant.

However, in many cases this configuration requires huge chilled water piping networks in the chillers to circulate the intermediate medium (water), making the entire system considerably more expensive.

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