Document Type: Original Article
Faculty of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, Iran
Department of Mechanical Engineering, Imam Khomeini International University, Qazvin, Iran
Design and optimization of various thermodynamic processes that are used in chemical industries such as low temperature refrigeration and cryogenic cycles, requires computer software to simulate the thermodynamic cycle and examine the effect of various parameters on the performance of the cycle. So existence of an equation of state to predict thermodynamic properties of working fluids in a wide range of temperatures and pressures is essential. Despite the greater complexity than the other equations, the fundamental equations of state have higher accuracy in the calculation of the thermodynamic properties and main advantage of them is that other thermodynamic properties can be obtained with high accuracy by differentiating them. In this study the thermodynamic properties of Helium and Neon as working fluids in cryogenic processes including density, internal energy, enthalpy, entropy, isobaric specific heat capacity and isochoric heat capacity, have been calculated based on fundamental equations of state using a developed computer code in MATLAB software. By comparing the results with the valid reference data, a range of temperature and pressure in which the fundamental equations of state can be used with high accuracy, have been presented. In this high accuracy region, the maximum error is related to the isobaric heat capacity that is 3.37 % and 1.1 % respectively for Helium and Neon.