Start-up procedure for refrigerant systems having microchemical consensor and reheat cycle

Abstract

A refrigerant system has a condenser of microchannel design and construction and includes a reheat cycle. The reheat cycle includes a refrigerant flow control device, such as a three-way valve, for selectively routing at least a portion of refrigerant through a reheat heat exchanger from a location between a compressor and expansion device. A control for the refrigerant system selectively actuates this refrigerant flow control device to route at least a portion of refrigerant through the reheat heat exchanger at system start-up.

Description

RELATED APPLICATIONS[0001]This application claims priority to U.S. Provisional Patent Application No. 61 / 061,142, which was filed Jun. 13, 2008.BACKGROUND OF THE INVENTION[0002]Refrigerant systems utilize a refrigerant to condition a secondary fluid, such as air, delivered to a climate-controlled space. In a basic refrigerant system, the refrigerant is compressed in a compressor, and flows downstream to a condenser in a subcritical refrigerant cycle or to a gas cooler in a transcritical refrigerant cycle, where heat is typically rejected from the refrigerant to ambient environment, during heat transfer interaction with this ambient environment. Then refrigerant flows through an expansion device, where it is expanded to a lower pressure and temperature, and to an evaporator, where during heat transfer interaction with a secondary fluid (e.g., indoor air), the refrigerant is evaporated and typically superheated, while cooling and often dehumidifying this secondary fluid.[0003]In recen...

AI Technical Summary

Benefits of technology

[0009]These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

Problems solved by technology

Due to low internal volume, microchannel heat exchangers are more susceptible to refrigerant pressure variations due to instantaneous changes in refrigerant flow throughout the refrigerant circuit.

Microchannel heat exchangers are also very sensitive to refrigerant charge amounts, with even a small amount of extra refrigerant charge in the system leading to higher than desirable discharge operating pressures and instantaneous pressure spikes.

These problems are especially pronounced during start-ups.

Nuisance interruptions of the refrigerant system operation can be a result of emergency shutdown by control software on a high pressure alarm or by mechanical safety, such as a high pressure switch, leading to complete inability to operate the refrigerant system, if a discharge pressure spike exceeded predetermined allowable safe limit (typically for a preset number of times).

This consequently would results in a failure to keep a climate-controlled environment within desirable temperature and humidity ranges, leading to occupant discomfort and liability claims.

Under certain circumstances, repeated starts and shutdowns in short periods of time can potentially lead to a compressor failure.

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