Co2 refrigerant system with tandem compressors, expander and economizer

Abstract

A refrigerant system utilizes an expander that provides a more efficient expansion process and recovers at least a portion of energy from this expansion process. At least a portion of refrigerant that has been at least partially expanded in the expander is tapped and passed through an economizer heat exchanger. In the economizer heat exchanger, the tapped refrigerant cools a main circuit refrigerant increasing its thermodynamic potential. Further, a compression section is provided with at least two compressors operating in tandem and allowing for multiple stages of unloading. By selectively utilizing one or more of the tandem compressors, the economizer cycle, and the expander, the refrigerant system can achieve very efficient operation and provide enhanced control flexibility, in particular, for the CO₂ refrigerant system operating in the transcritical cycle.

Description

BACKGROUND OF THE INVENTION[0001]This application relates to a refrigerant system wherein an expander is utilized to provide a more efficient expansion process, by recapturing energy from this expansion process and utilizing that energy to power at least one system component. A portion of refrigerant is tapped from a location in the expander at which it has been at least partially expanded, and the tapped refrigerant is then utilized to subcool a main refrigerant flow in an economizer heat exchanger. In this manner, a single expander can provide both main and economizer expansion device functions for the refrigerant system, and enhance these main and economizer expansion device functions. Further, the refrigerant system includes tandem compressors only some of which may be economized. Lastly, the refrigerant system may be charged with CO2 refrigerant that, at least for a portion of the time, may operate in a transcritical cycle.[0002]Refrigerant compressors circulate a refrigerant t...

AI Technical Summary

Benefits of technology

[0007]In a disclosed embodiment of this invention, an expander is utilized to provide a more efficient active expansion process to potentially recapture energy from this expansion process, and utilize that energy to power at least one refrigerant system component. The expander increases capacity and enhances efficiency of a refrigerant system through a more efficient expansion process (reduced irreversible losses) and recovering, at least partially, the expansion process energy. Further, a portion of refrigerant that has been at least partially expanded in the expander (or through the first stage of the expander) is tapped and passed through an economizer heat exchanger in heat exchange relationship with a main refrigerant flow. This tapped refrigerant is injected back into the compressor (a single compressor or a multi-stage compressor system consisting of compressors connected in series) at some intermediate pressure. All or only some of the compressors may be economized. Exiting the economizer heat exchanger, the main refrigerant has a higher thermodynamic potential that allows for enhanced refrigerant system performance. In addition, the refrigerant system includes at least two tandem compressors that, along with the economizer function, allow for efficient system unloading and precise matching of delivered system capacity to thermal load demands in the conditioned space. The expander may transfer the recovered energy from the expansion process, directly or indirectly through an energy conversion device, to at least partially power one of the tandem compressors. The refrigerant system, as disclosed, may use a natural refrigerant such as CO2. The proposed refrigerant system enhancements are particularly beneficial for the CO2 refrigerant system operating in a transcritical cycle.

Problems solved by technology

However, no refrigerant system to date has included an expander, tandem compressors and an economizer cycle combined together to provide a powerful combination of operational options and enhancement features.

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