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Measurement system for the specific heat of refrigerants
S. Lee, D. Kim, S.H. Lee, W. Kang, X. Xiao and S. Kwon

Research efforts have been focused on the development and discovery of alternative refrigerants with low Global Warming Potential (GWP) in response to environmental shifts. Accurate equations of state (EOS) for these new refrigerants are crucial for designing efficient cooling systems in industries. This necessitates precise measurement and analysis of specific heat capacity ₍𝑐_𝑝). To determine the specific heat capacity of unknown refrigerants, we developed a specific heat measurement system by integrating a commercial syringe pump and a Calvet calorimeter. The sample injection system can control pressures up to 100 bar, while the calorimeter accurately measures specific heat capacity within the temperature range of 203.15 K to 333.15 K. Real-time monitoring and active control of pressure and temperature are crucial as specific heat capacity measurements with a Calvet calorimeter typically consume significant time. We validated the system by measuring the specific heat capacity of heptane, a widely recognized reference substance. Additionally, to assess the precision of our refrigerant specific heat capacity measurement system, we measured the specific heat capacity of propane, R32 (Difluoromethane), and R125 (Pentafluoroethane) in the liquid phase while adjusting temperature and pressure. Our research findings are in line with values reported in existing literature, demonstrating a standard uncertainty of less than 3 % (𝑘=1) in case of specific heat capacity measurements of R32 conducted at 288.15 K

Keywords: Specific heat capacity, low temperature Calvet calorimeter, Refrigerants, Syringe pump, baseline, DSC, temperature control