Refrigeration apparatus

Abstract

An extra low temperature refrigeration system consisting of a two-stage compressor that has an electronic controller. The electronic controller controls an electric expansion valve in the evaporator, which modulates the true superheat. There is also an electric pressure control valve in the condenser, which modulates the head pressure in cool mode, and the suction pressure in defrost mode. The defrost cycle uses a reversing valve. The liquid refrigerant for the inter-stage sub-cooling circuit is constantly provided by a sub-condenser separated from a conventional one condenser system. Therefore, the system provides constant cooling for the compressor motor windings as the compressor runs. There is a one-way pathway from the main condenser circuit to the sub-condenser circuit. This pathway will call for more refrigerant from the main circuit to the sub-cooling circuit as demanded. The inter-stage sub-cooling circuit uses an electric expansion valve true superheat control for its sub-cooler.

Description

[0001]This application claims benefit under Title 35 U.S.C 119(e) of U.S. Provisional Application Ser. No. 61 / 402,657 filed Sep. 1, 2010.FIELD OF THE INVENTION[0002]This invention relates generally to space cooling systems, in particular to a low temperature refrigeration apparatus for providing space cooling with significant energy and cost savings.BACKGROUND OF THE INVENTION[0003]A typical space cooling system includes at least one evaporator system contained within the space that is to be cooled, a condenser system that is located outside of the cooled space, and a compressor positioned between the condenser system outlet and the evaporator system inlet and, finally, an expansion valve which completes the loop joining together the condenser system outlet and the evaporator system inlet. A refrigerant is circulated within the loop, which cools the space as follows. The refrigerant is compressed by the compressor, which raises the temperature and pressure of the refrigerant. The ho...

AI Technical Summary

Benefits of technology

The invention is a refrigeration system with a dual valve control, two-stage compressor, dual circuit condenser design, electric expansion valve for true superheat control, oil pressure initiated defrost, and a bi-flow liquid receiver and surge protector. The system also uses a reverse cycle defrost method and a liquid reservoir for energy savings and refrigerant surge protection. The compressor uses an oil differential pressure switch to initiate defrost and a temperature-sensing probe to measure the compressor true superheat. The evaporator uses compressor-discharged vapor to defrost the drain pan. The system offers constant cooling for the compressor motor windings, improved life span of the compressor, and maximized main liquid sub-cooling. The invention also reduces pressure drop of reverse flow and offers a fast and clean defrost throughout the evaporator coil.

Problems solved by technology

However, there is not found in the prior art an extra low temperature refrigeration system that combines the features of dual valve control, dual circuit condenser design, superheat control on the sub-cooler circuit, a liquid receiver to store extra refrigerant charge, an oil-pressure initiated defrost, parallel hot gas drain pan loop design on the evaporator to defrost the drain pan, and a compressor superheat control that will provide performance and protection features and lower head pressure to achieve high reliability and substantial operating cost savings.

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