This study aims to provide an experimental investigation and comparison of the condensation heat transfer characteristics in a plate–fin heat exchanger (PFHE). The heat flux, mass flux, and saturation pressure were adjusted as experimental parameters to verify the effects on the condensation heat transfer. In addition, condensation heat transfer correlation of two-stream PFHEs was provided based on the experimental data for utilization as a design reference for the heat exchanger. The turbulence is the most influential in heat transfer. One of the ways to foster turbulence is to increase shear stress. The higher flow velocity results in the higher shear stress. That was why increasing mass flux or the flow with higher vapor quality showed the higher heat transfer coefficient (HTC). Refrigerant properties such as viscosity and specific volume of vapor changed according to the saturation pressure. It is expected they affect the degree of turbulence too in similar manners. The mass flux was more influential than the heat flux and saturation pressure. Thus, the equivalent mass flux of the refrigerant is dominant in the derived correlation model. The average difference between experimental and calculated HTC from correlations was about 6.5%. Multi-stream PFHE comprises an additional heat transfer surface, which implies a more active droplet formation. The average pressure drop in the multi-stream is 15% larger than that of the two-stream.

This study investigated the evaporative heat transfer coefficient and pressure drop characteristics of R-1234yf in a horizontal tube with an inner diameter of 6.95 mm under various experimental conditions. The heat transfer coefficient increased with an increase in quality but showed a sharp decrease in the high-quality area. In addition, the heat transfer coefficient increased as the mass flux, heat flux, and saturation temperature increased. Although R-1234yf and R-134a presented similar heat transfer coefficients, that of R-134a was higher. The pressure drop increased with an increase in the quality and mass flux but decreased with an increase in the saturation temperature. The pressure drop of R-134a was larger than that of R-1234yf. In light of the flow pattern diagram by Taitel and Dukler, most of the experiments were included in the annular flow region, and some regions showed intermittent and stratified corrugated flow regions. Kandlikar’s heat transfer coefficient correlation provided the best prediction for the experimental database, with approximately 84% of the predicted data within ±30%. Moreno Quibén and Thome’s equation for pressure drop predicted approximately 88.71% of the data within ±30%.

Demand for low temperatures below -60℃ is increasing in various places. Accordingly, SMR refrigerators are attracting attention as a way to supply them. we recognized the limitation that the study of SMR refrigerators is focused on selecting the composition ratio of mixed refrigerants. However, operating pressure is also an important factor that greatly affects the performance of the refrigerator. In this study, we attempted to understand the performance characteristics of the refrigerator according to the change in operating pressure. The experiment was conducted by changing the compressor discharge pressure to 15bar and 20bar while the compressor suction pressure was fixed to 2.5bar, and the compressor discharge temperature, power consumption, cooling time, refrigeration capacity, and COP were calculated and compared. As a result of the experiment, it was confirmed that when the compressor discharge pressure was high, the compressor discharge temperature increased due to the increase in the compression ratio, and larger power consumption was required. It was confirmed that the cooling time was faster due to a decrease in the heat exchange amount of the intermediate heat exchanger when the compressor discharge pressure was high. It was confirmed that the refrigeration capacity and COP also increased when the compressor discharge pressure was high.