A novel variable liquid-properties thermal network model for researching on thermodynamic characteristics of ethylene glycol piston pump

Abstract

Due to the flame resistance and lubricity of ethylene glycol solution, an ethylene glycol piston pump can be used as motion sources for extreme operating conditions. In this paper, a novel variable liquid-properties thermal network model (VLTNM) is proposed to analyze the thermodynamic characteristics of piston pump. The VLTNM considers the interaction between the changes in properties of liquid passing through piston pump and the heat generated by motion, and calculates the heat transfer between solid and liquid through a thermal network. A numerical calculation model for VLTNM is established in MATLAB using simscape language, and the results show that the temperature rise of outlet liquid can be reduced by 10.36%, when the thermal conductivity of shell is doubled. The working pressure has a positive effect on temperature variation, which is more significant in high-temperature environments, while the volume fraction of ethylene glycol solution has a negative effect. Additionally, a high load helps to improve the efficiency of piston pump, while the temperature rise caused by high pressure can also reduce the efficiency. When the working pressure increases from 6 MPa to 10 MPa, the efficiency decline of piston pump increased by 1.12%. Besides, comparing the two models of variable and non-variable liquid properties, there is a significant deviation in steady temperature of outlet liquid. The deviation in low temperature is more prominent, with a deviation of 6.1% when the temperature of air is 10 °C. Finally, the predicted steady temperature by VLTNM is in good agreement with the experimental data in reference, with a prediction error of less than 2.01%.