Design and evaluation of an adjustable wall-sharing liquid–suction heat exchanger for a vapour-compression freezing system

Abstract

Liquid–suction heat exchangers (LSHEs) can improve vapour-compression refrigeration performance, but conventional designs are often constrained by interfacial thermal resistance and fixed heat-exchange lengths. This study proposes an adjustable wall-sharing LSHE (AWS-LSHE) that combines a direct shared copper-wall interface with selectable heat-exchange lengths while maintaining complete hydraulic separation between the liquid and suction streams. Three branches with effective contact lengths of 300, 600, and 900 mm were fabricated and tested separately under stabilized conditions in an R407C freezing system. Three-dimensional conjugate heat-transfer simulations were also conducted to examine thermal development within the shared-wall region. Increasing the contact length enhanced liquid subcooling, suction-vapour superheating, heat-transfer rate, effectiveness, and system COP, although it increased the pressure-drop penalty. Under low-ambient conditions, the 900 mm branch achieved the highest thermal performance, with a peak COP of 3.21, an effectiveness of 0.91, and an 11.0% reduction in metered 24 h energy consumption, from 17.21 to 15.31 kWh day⁻¹. The maximum COP improvement of 33.8% represents a stabilized pointwise comparison rather than a seasonal gain. A pressure-normalized screening index identified the 600 mm branch as the best heat-duty-to-pressure-loss compromise. Propagated uncertainties were ± 2.7% for COP and ± 2.3% for effectiveness, while CFD predictions agreed with measured outlet temperatures and branch pressure drops within 0.57% and 3.60%, respectively. The results demonstrate that selectable wall-sharing lengths provide a compact platform for balancing heat recovery and hydraulic penalty, with dynamic automatic switching requiring further validation.