Vapor compression system

Abstract

A vapor compression system includes a main vapor compression circuit including a compressor, a condenser, an expansion device and an evaporator serially connected by main refrigerant lines, the compressor having a main discharge port, a suction port and an economizer/bypass port, an economizer circuit connected between the condenser and the economizer/bypass port of the compressor and including an auxiliary expansion device and a heat exchanger serially connected by economizer refrigerant lines, the economizer refrigerant lines and the main refrigerant lines being exposed to each other for heat exchange in the heat exchanger; and a bypass circuit including a bypass line extending from the economizer/bypass port to the suction port, and a bypass valve positioned along the bypass line, the bypass valve being positionable between a closed position wherein the economizer circuit is active and the bypass circuit is inactive, and an open position wherein the economizer circuit is active and the bypass circuit is active. The system and method advantageously allow for the economizer circuit and bypass circuit to be operational at the same time. By using an electronically controlled auxiliary expansion device, four modes of operation are permissible. As a result, life cycle and system costs can be reduced and compressor reliability and system performance can be enhanced. Additionally the control scheme and method extend the system operating envelope, hence preventing nuisance shutdowns, and further improving compressor reliability.