Refrigerant system with economizer, intercooler and multi-stage compressor

Abstract

A refrigerant system is provided with a multi-stage compression system. An intercooler is positioned between at least two compression stages to cool a refrigerant, by heat transfer interaction with a secondary fluid, after it has been compressed in the lower compression stages to some intermediate pressure. The intercooler enhances refrigerant system performance, improves compressor reliability, and extends operational envelope. Further, at least one economizer circuit is incorporated into the refrigerant system that returns the economized refrigerant flow at the location between at least two compression stages.

Description

BACKGROUND OF THE INVENTION[0001]This application relates to a refrigerant system with a multi-stage compressor that combines the benefits of an intercooler heat exchanger and an economizer cycle. In particular, this application relates to a refrigerant system operating, at least for a portion of the time, in a transcritical cycle.[0002]Refrigerant systems are known, and are utilized to condition a secondary fluid. As an example, an air conditioning system cools and dehumidifies air being delivered into a climate controlled environment.[0003]A basic refrigerant system includes a compressor compressing refrigerant and delivering that refrigerant through a discharge line downstream to a first heat exchanger, a so-called condenser for subcritical applications or a gas cooler for transcritical applications. In the first heat exchanger, the heat is removed from the refrigerant by a secondary media, such as ambient air. From the first heat exchanger, refrigerant passes through an expansio...

AI Technical Summary

Benefits of technology

The invention is a refrigerant system with multiple compression stages connected in series. An intercooler is placed between the stages to cool the refrigerant after it exits the lower stage and before it enters the higher stage. The system also incorporates an economizer cycle, where a portion of the refrigerant is returned from an economizer branch to an intermediate compression point between the higher and lower stages. The intercooler and economizer circuit can be positioned between the same compression stages or between different stages depending on the temperature of the secondary fluid and the capacity-efficiency tradeoff of the economizer circuit. The positioning of the economizer circuit between the lower stages allows for larger temperature differentials and higher refrigerant cooling potential, improving system performance and reliability. The invention also allows for a larger step in refrigerant system unloading strategy and optimizing discharge pressure in transcritical operation.

Problems solved by technology

If the compression ratio for the compressor system is high (which is typically the case for multi-stage compression systems) and / or refrigerant suction temperature is high (which is often the case for a refrigerant system equipped with a liquid-suction heat exchanger), then refrigerant discharge temperature can also become extremely high, and may exceed the limit defined by safety or reliability considerations.

However, the additional cost and complexity of the circuitry and components associated with the intercooler and economizer, makes the provision of the intercooler less feasible.

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