Calibration of a test rig and experimental measurements for the characterization of suction accumulators for heat pumps

This thesis was conducted in collaboration with Ghent University and supported by Daikin Europe. The project involves experimental research on a setup designed to test the behavior of a refrigerant within a suction accumulator. This innovative prototype is equipped with a second bleed hole, a solution not yet reported in the scientific literature. A suction accumulator is a component of heat pumps, typically located between the evaporator and the compressor. Its function is to prevent liquid refrigerant from flooding back into the compressor and to regulate the amount of refrigerant/oil mixture circulating within the heat pump. The setup was tested with R454C, a low-GWP refrigerant that is a promising candidate for compliance with European F-gas regulations. The Global Warming Potential (GWP) index allows for the comparison of the environmental impacts of different gases. This work focuses on estimating the influence of the liquid level on the outlet vapor quality of the accumulator and the pressure drop across it, considering different refrigerant mass flow rates and saturation pressures. The results were also compared with references found in the literature. The pressure difference between the inlet and outlet, as well as the liquid level, was measured directly using sensors, while the inlet and outlet qualities were calculated indirectly via an energy balance. The setup was optimized to test under satisfactory steady-state conditions. Due to foaming, a correlation was observed between the liquid level inside the accumulator and the outlet quality. Foaming occurs when, at steady state, a moderate refrigerant mass flow rate into the accumulator disrupts the liquid level, transforming it into a foam-like mixture of liquid and gas. Comments were made regarding the foaming behavior in this setup of both R32 and R454C.