Expansion Valves - Can't Cool a Mansion Without Expansion

Industrial refrigeration systems are complex when compared to an air conditioning system for residential homes, but the CORE fundamentals of how industrial vs residential refrigeration cycles operate is identical.

To keep this article short & relevant we're only going to discuss how the "EXPANSION" step of a refrigeration cycle works.

Expansion valves have different designs & applications, but they do have three (3) key fundamentals for operation. The main purpose of an expansion valve is to remove pressure & temperature from the refrigerant to allow expansion aka change of state to occur. When high-pressure liquid refrigerant (70 psig or higher) flows through an expansion valve, the following three (3) steps must occur to be identified as an expansion valve:

• Pressure drop

• Temperature drop

• Increase in velocity

Above image is a great visualization of this anomaly occurring. On the left side (orange pipe) is high-pressure ammonia liquid refrigerant (150 psig approx.) that has reached its final voyage before flowing across the motorized expansion valve MEV (V738). The ammonia exiting the valve body has encountered a pressure drop, temperature drop, and has increased its velocity, you can see that these steps have successfully occurred because of the ice/frost on the exit of the valve (right side). For the ammonia refrigerant, this is not a one-time voyage, it will travel through the remaining refrigeration system just like a roller coaster ride, but for the ammonia, the ride never ends, and the ride starts over and over again.

Expansion Valve Flash-Gas is produced when condensed liquid is subjected to boiling. When compared to other types of energy loss, such as heat energy that is wasted when a 60-watt incandescent light bulb is illuminated. To have light, you must accept the penalty of wasted electrical energy through heat energy. This concept is comparable to expansion valves that produce flash-gas. Depending on the temperature difference, the lower the temperature = more flash-gas created across the expansion valve. This wasted flash-gas travels back to the compressor to be compressed and provides no benefit to the refrigeration system efficiency. The refrigeration cycle is not possible without some amount of flash-gas occurring.

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Liquid Injection Cooling

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