Conference Year

2014

Keywords

secondary loop refrigeration, accumulator, receiver, near-optimal control, R134a

Abstract

Recent attempts to find energy-efficient thermal management systems for electric and plug-in hybrid electric vehicles have led to secondary loop systems as an alternative approach to meet dynamic heating and cooling demands and reduce refrigerant charge. As such, a thorough understanding of the vapor compression cycle, which serves as the central thermal supply unit, is required. In addition to design considerations concerning the type and size of components such as the heat exchangers or compressor, the refrigerant reservoir choice between a high pressure receiver or a low pressure accumulator is critical for energy-efficient operation under varying operation conditions. In this work, two possible positions of the accumulator/receiver are experimentally examined and optimal control is applied. Therefore, either the superheating at the compressor inlet or outlet of the receiver system or the subcooling at the condenser outlet of the accumulator system are chosen as control variables and adjusted by an electrical expansion valve. Experimental results based on a simple automotive R134a primary loop system containing a scroll compressor are presented. Comparing these two different systems with a receiver or an accumulator, a receiver system shows a slightly higher COP under the examined operation conditions when operated optimally. However the receiver/accumulator position has a non-negligible impact on high and low pressure itself resulting in an advantage for the accumulator system in a cold winter scenario.

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