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A numerical simulation of energy efficiency in commercially available double pipe heat exchangers in the market was investigated based on the Second law of thermodynamics in this paper. The effects of CO2 mass-flow rate, water mass-flow rate, pressure, CO2 inlet temperature, and water inlet temperature of the double pipe heat exchanger were considered to evaluate the energy efficiency by analyzing entropy generation, exergy destruction, and entransy dissipation. The changes of the entropy generation, the changes of exergy destruction, and entransy dissipation are similar regardless of the operating conditions. Pressure has the most significant effect on the energy efficiency of the double pipe gas cooler compared to other operating conditions but negligible on the exergy destruction. The pressure, flow rate, and inlet temperature have completely different effects on energy efficiency depending on the region. The entropy generation and entransy dissipation at y = 0 m to y = 0.05 m (y-axis is the radial direction) decrease with increasing pressure and the opposite after that. The increase of CO2 inlet temperature at y < 0.5 m is accompanied by an increase of entropy generation, exergy destruction, and entransy dissipation but this situation disappears after y = 0.5 m. Entropy generation, exergy destruction, and CO2 and water mass-flow rate are first negatively and then positively correlated with the cut-off point at y = 0.1 m.

Temperature control is an important factor which influences the accuracy of refrigerant heat transfer experimental results. In this paper, the three temperature control methods for the electric heating water tank (EHWT) in the single tube heat transfer experimental rig are investigated. The error of PID controller is ? 1?C and the stability time is 390s. The control performance is not satisfactory. A fuzzy controller and a fuzzy PID controller are designed to improve temperature control performance. The designed controllers are simulated by Matlab/Simulink and and the results prove that the designed controllers is suitable for EHWT. The experimental results show that the performance of the designed controllers are improved concerning. The error of two controllers is ?0.1?C. Compared to the PID controller, the stability time of the fuzzy controller and the fuzzy PID controller are decreased by 14.9% and 43.1%; the overshoot of the two controllers are reduced by 100% and 62.5% , respectively. The results and the control method have great significance for the refrigerant heat transfer experiment.

In this paper, the effect of different forms of electric heating wire forms on the anti-icing performance of the refrigerated container was studied based on numerical simulation. The heat transfer and the thermal conductivity of the refrigerated container door wall, and the uniformity of airflow distribution in the refrigerated container are analyzed. The heating wire form 2 has the best anti-icing performance and meets the anti-icing requirement When the thermal conductivity is from 0.005 W/(m?K) to 0.01 W/(m?K). The electric heating wires nearest to the inner wall surface is the optimal anti-icing solution. The spare electric heating wires placement can be determined according to the thickness of the refrigerated container door. The specific layout of electric heating wires in the future can be further optimized in combination with carbon emissions.

The adverse effects of global warming and climate change require critical measures for marine refrigeration technology because of its impact on greenhouse gas emissions. A novel transcritical CO2 two-stage compression/ejector refrigeration cycle for shipboard cold chamber is proposed in this research. A comparative analysis was conducted between the basic transcritical CO2 two-stage compression cycle and the cycle equipped with a two-phase ejector considering the coefficient of performance. Meanwhile, the refrigeration cycle was analyzed using entropy analysis to elucidate the distribution of irreversible losses in each component of the two-stage compression/ejector refrigeration cycle, and the effects of system parameters such as the evaporating and gas cooler outlet temperatures as well as the intermediate and discharge pressures on the cycle were investigated. The results showed that the ejector had the largest power capability loss, accounting for 26.95 % of the overall system, which is followed by the low-pressure compressor with 26.06 %. The coefficient of performance of basic and ejector system significantly increase as the gas cooler outlet temperature and intermediate pressure decrease as well as the evaporating temperature increases. Furthermore, the entropy production of the system components decreases gradually with increasing evaporating temperature, with the greatest reduction in the ejector. In addition, the entropy production of the two-phase ejector remains constant with the increase of the high-pressure side discharge pressure and gas cooler outlet temperature.