Refrigeration system with bypass subcooling and component size de-optimization

Abstract

A refrigeration system having a primary refrigerant path including a compressor, a condenser, a primary expansion device, and an evaporator connected together to form a closed loop system with a refrigerant circulating therein; and a bypass path coupled to an outlet of the condenser. The bypass path includes a secondary expansion device; and a heat exchanger thermally coupled to the primary refrigerant path between the condenser outlet and the primary expansion device inlet to remove heat from the refrigerant discharged from the condenser. The condenser is downsized such that lacks the heat transfer capacity to provide some or all of the required subcooling as provided according to conventional practice, and the heat exchanger provides some or all the required subcooling according to the capacity of the condenser. A pressure differential accommodating device operative to mix two vapors at different pressures may also be provided to connect the outlets of the evaporator and the heat exchanger to an inlet of the compressor. A method of operating a refrigeration system with a downsized condenser and an a bypass path including a heat exchanger to provide subcooling is also described.

Description

CROSS-REFERENCE TO PRIOR APPLICATION [0001] This application claims priority to U.S. Provisional Application Ser. No. 60 / 426,073, filed Nov. 11, 2002.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to a high efficiency refrigeration system and more specifically, to a refrigeration system utilizing a bypass path for subcooling, in combination with selection of the sizes of the condenser, compressor and evaporator, to achieve increased overall system efficiency. [0004] 2. Relevant Art [0005]FIG. 1 is a block diagram of a conventional refrigeration system, generally denoted at 10. The system includes a compressor 12, a condenser 14, an expansion device 16 and an evaporator 18. These components are connected together, typically by copper tubing such as indicated at 19 to form a closed loop system through which a refrigerant such as R-12, R-22, R-134a, R-407c, R-410a, ammonia, carbon dioxide or natural gas is cycled. [0006] The ...

AI Technical Summary

Benefits of technology

[0021] According to the present invention, it has been found that significant improvements can be obtained using a bypass circuit for subcooling in a system in which the conventional balanced or optimized relationship between the evaporator, compressor and condenser is abandoned, and in which a condenser is used which would not provide sufficient heat removal capacity according to normal practice. In other words, in an optimized system, the required capacity determines the evaporator size which then dictates the compressor size, and the heat input of these together dictate the condenser size. In contrast, according to the present invention, after the evaporator size has been determined, the condenser size is “de-optimized” by reducing or eliminating the subcooling capacity, and providing the lost subcooling through use of a heat exchanger driven by refrigerant diverted into a bypass circuit, e.g., from the main expansion valve. This allows use of smaller compressor, with consequent improved EER and system cost. The smaller condenser also reduces space requirements for the system.

[0022] This surprising ability to achieve improved performance beyond that thought possible using bypass technology comes about because in a balanced system, the condenser is already large enough, and the system cannot utilize the additional subcooling. However, in a refrigeration system like the present invention where the condenser is substantially smaller than the optimum-sized condenser, the bypass method is able to show significant benefit as the increased subcooling makes the small condenser behave like an optimum-sized condenser or an oversized condenser. This increases both the cooling capacity and EER significantly.

[0023] Similarly, the invention allows the evaporator to be made substantially larger than the optimum-sized evaporator, and the heat absorption is increased accordingly. Then, the bypass method is able to demonstrate significant benefit as the increased subcooling makes the proportionally smaller condenser behave like an optimum-sized condenser or an oversized condenser. In such an embodiment of the present invention, the condenser pressure is maintained constant despite the increased heat absorption at the evaporator, thus increasing both the cooling capacity and EER without increasing compressor work.

Problems solved by technology

This allows use of smaller compressor, with consequent improved EER and system cost.

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