Impact of inclination changes on a liquid-to-liquid vapor compression cycle - cooling capacity and liquid flooding

Abstract

• Showed that inclination dependence of cycle correlates with mass flow rate. • Proposed inclination dependence indicator for vapor compression cycle. • Showed risk of liquid flooding due to inclination to increase with refrigerant charge level. The operation of vapor compression cycles at varying orientation with respect to gravity has rarely been investigated, except in a few studies preparing refrigeration cycles for space applications. While two-phase flow in inclined tubes is an active field of research, the translation of the findings to two-phase flow systems, such as a vapor compression cycle, is unclear. For example, the common hypothesis that two-phase flow is gravity independent under high refrigerant velocities has not been validated for systems. In this paper, a test stand to investigate the inclination dependence of the cycle is described and a system level inclination dependence indicator is presented that decreases with increasing refrigerant mass flux until 10 kg/(m 2 ∙ s) in the evaporator. For higher flow rates, the indicator shows a constant dependence. Additionally, it is shown that the intensity of liquid flooding of the suction line due to inclination increases with the refrigerant charge.