RETA Breeze Sep-Oct 2022

Refrigeration The Economizer Suction is a side port strategically placed between the suction and discharge of a compressor. The purpose for the Economizer Suction port is to accept small heat loads primarily off a subcooling device often referred to as an Economizer. The Economizer is placed between the condenser and the evaporator. This can be a plate and frame or shell and tube heat exchanger. This is done to subcool the liquid feeding the evaporator using pressure differential, which yields a better refrigerating effect in the evaporator due to less flash gas being developed at the point of expansion. The way it typically works is the High Pressure, High Temperature Saturated Liquid leaves the condenser where a portion of the liquid passes through an expansion valve dropping both pressure and temperature, while the High-Pressure warm liquid passes though the remaining heat exchanger. (Warm liquid passes through one set of plates while cooler liquid passes through the opposite plates). The Low Pressure, Low Temperature liquid removes heat from the High Pressure, High Temperature liquid without effecting the pressure effectively subcooling the liquid feeding the evaporator. The heat exchange causes some of the liquid to evaporate. The vapor generated from the heat exchange at the Economizer is drawn into the side port (Economizer Suction) of the compressor. The subcooler (Economizer) is maintained at an intermediate pressure by the placement of the economizer suction port entering part way up the compression chamber. The evaporators

that are being fed by the subcooled liquid leaving the economizer can run at a lower temperature because of where the vapor leaving the evaporator enters the compressor. The vapor leaving the evaporator enters through the main suction port of the compressor where a much larger volume of vapor can be compressed giving you a variety of options in regard to temperature and pressure. Utilizing economized suction ports allows you to handle small and large loads utilizing only one compressor reducing the Kw demand on the low side of the system as well as the high side of the system. This is a much deeper topic than what was covered, and this was only meant to be an introduction to economized suction not an all-inclusive detailed description. The way it typically works is the High Pressure, High-Temperature Saturated

Liquid leaves the condenser (b) where it is then split. A portion of the liquid (m1) passes through an expansion valve dropping both pressure and temperature (e), while the remaining High-Pressure warm liquid (m2) passes though the heat exchanger. The warm liquid passes through one set of plates while cooler liquid passes through the opposite plates. This heat exchange causes some of the warmer liquid to evaporate (m1) where it enters the economizer suction port (f ) which is strategically placed between the main suction and discharge ports of the compressor. In the next issue of the RETA BREEZE, I will expand on the subject in more detail. If you have any more information in regard to economized suction and want to include them in my next article, please email me at harry@reta.com.

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