In order to investigate the electrochemical corrosion behavior of hydrogen chloride diaphragm pump membranes in high-chloride and high-temperature hydrogen chloride environments, Tafel polarization method and Electrochemical Impedance Spectroscopy (EIS) were employed to analyze the corrosion resistance of the membranes. The corrosion samples of the membranes under different operating conditions were analyzed by SEM, EDS, and XPS testing methods. The results indicate that 301L stainless steel membranes suffer severe corrosion in hydrogen chloride environments, with no stable passivation region observed in the polarization curves. With increasing solution concentration and temperature, the self-corrosion current density increases, leading to a decrease in corrosion resistance. The stainless steel membranes exhibit high sensitivity to temperature. The charge transfer resistance in a 90 ℃ HCl solution environment is 3.682, which is only 6.7% of that at 50 ℃. The corrosion current density is 1.258×10^-2 A/cm², which is 3.94 times that at 50 ℃, and the ion diffusion rate accelerates. Competition for Cl^- adsorption makes it difficult for oxides in the corrosion products to maintain stability, hindering the formation of a passive film on the surface, thus leading to the occurrence of pitting corrosion in stainless steel. These findings provide a basis and reference for the study and design of corrosion-resistant membranes for diaphragm pumps.

In responese to the current low temperature conditions of electric rehicle heat pump air conditioning systems, the surface of the outdoor evaporator is prone to frosting, which in turn affects the heat transfer efficiency, system performance, and driving range. Existing research has found that due to the different heat exchange capabilities of the two phases of the refrigerant in the evaporator, the frosting phenomenon is uneven, thus having a negative impact on the system performance. To address this issue, this paper proposes a solution of adding a gas-liquid separator in front of the outdoor evaporator. By adjusting the opening degree of the gas-phase bypass valve, the evaporation pressure can be optimized, and the overall performance of the evaporator and the system can be improved. By comparing the specific variation trends of the system's heat transfer efficiency, coefficient of performance (COP), and the outlet temperature of the evaporator under the conditions of the optimal opening degree of the gas-phase bypass valve and zero opening degree, at different ambienttemperatures (-5, 0, 5 ℃), evaporation pressures (0.199, 0.242, 0.291 MPa), and compressor speeds (2 000, 3 000, 4 000 r/min), the experimental results show that after adding the gas-liquid separator, the heat transfer efficiency is increased by up to 6.9%, the COP is increased by up to 7.4%, and the outlet air temperature of the evaporator is increased by 3.6% ~ 11.2%. This improved design can effectively alleviate the frosting problem under low-temperature conditions and enhance the system performance.

To address the issue of inadequate cooling capacity of mechanical ventilation air-cooled towers during the summer season, a kind of mechanical ventilation cooling tower with dry and wet combined ventilation is proposed, and the variation rules of water temperature and evaporation of cooling tower under 3 groups of circulating water flow, 2 groups of inlet water temperature and 2 groups of fan frequency are studied experimentally. It has been discovered that a decrease in circulating water temperature is correlated with an increase in circulating water flow rate and a decrease in both inlet water temperature and fan frequency. When the inlet water temperature of the tower is 40 ℃ and the fan frequency is 35 Hz, the circulating water temperature drop of the combined dry and wet mechanical ventilation cooling tower is 4.74, 3.95, 3.56 ℃ when the circulating water flow rate is 30, 45, 60 m³/h, respectively. Compared with the mechanically ventilated air cooling tower (the circulating water temperature drop is 2.22, 1.50, 1.05 ℃ respectively), the water temperature drop is further reduced by 2.52, 2.45, 2.51 ℃. The water evaporation of different circulating water flow rates is 0.098, 0.106, 0.142 kg/s, respectively. It can be seen that the dry and wet combined mechanical ventilation cooling tower can further reduce the water temperature out of the air-cooling tower with the help of a small amount of water evaporation, which helps to improve the cooling capacity of the air-cooling tower in the summer high temperature period, and the research results can provide theoretical guidance for energy saving and efficiency improvement of air cooling tower.

Given the lack of relevant research on thermal management systems and core heat exchange equipment in China, the high energy consumption, and the difficulty in realizing long-cycle and low-energy operation, the basic operation characteristics of liquid hydrogen refueling stations were first discussed, the typical process routes of various thermal management systems were sorted out, and the current technical research status and the technical characteristics were analyzed. Finally, a new thermal management system that integrates the functions of vaporization temperature regulation, mixing-heat transfer, and accumulated cooling capacity release is proposed, and the technical aspects of efficient thermal management equipment are analyzed. The total hydrogen refueling capacity of 2 000 kg/d and the maximum refueling rate of 7.2 kg/min station design objectives are also examined. The study shows that through the proposed thermal management system and heat exchanger equipment for the orderly use of energy, while reducing the heat load of the air ambient vaporizer and the footprint, 62% of the cold energy of liquid hydrogen can be recovered; Moreover, through the multi-effective use of cold energy of the hydrogen BOG, the fuel cell conditions of the whole station peak electric power consumption ≤ 100 kW can be realized. It is hoped that pertinent research can offer theoretical and technical support and promote the development and application of the hydrogen energy.

Conventional mechanical vapor recompression (MVR) distillation technology cannot meet the energy-saving distillation requirements for ethanol-water, while balancing the safety and economy of the distillation system, taking into account the safety and economy of the distillation system, an external working medium splitting MVR heat pump distillation system was developed. A combined NRTL-RK model using NRTL equation in liquid phase and RK equation in gas phase was constructed to fit the thermodynamic properties of the system. With the help of Aspen Plus software, four kinds of systems, namely conventional distillation, conventional MVR heat pump distillation, direct compression MVR heat pump distillation and external working medium separation MVR heat pump distillation, were simulated and analyzed. The results show that the safety of the system is improved by introducing water as circulating working medium and compressing water vapor instead of ethanol vapor. With the split structure, the temperature difference of the upper distillation column is only 3.54℃, which effectively reduces the temperature difference of the compressor inlet and outlet. The comparison between the analysis results of the NRTL-RK combination model and experimental data shows that the constructed NRTL-RK combination model can accurately fit the thermodynamic characteristics of the ethanol-water system. Compared with the conventional ethanol distillation system, the designed and developed external working fluid split MVR heat pump distillation system can save 72.15% of energy and 70.87% of operating costs. The system has been successfully applied in actual production, with significant energy-saving effects. The research results can provide reference for energy saving transformation in ethanol distillation process.

To improve the working ability of Helmholtz self-excited waterjets, LES was used in the flow of the cavity using UDF dynamic grid-driven ultrasonic focusing vibration boundary, and the reliability of the model was verified by comparing the simulated and experimental values of the outlet pressure. The study explored how external ultrasonic vibration and varying frequencies influenced self-excited frequency, velocity, and cavitation. From the perspective of energy conversion, the reason for the enhanced shear characteristics inside the chamber is revealed. The vapor phase distribution in the lower chamber under various conditions was compared, and the jet performance of each section of the jet structure was analyzed. Explained the development process of periodic vortex structures under ultrasonic excitation. The results show that when the ultrasonic excitation at 25 kHz compared to ordinary jet, the natural oscillation frequency soared 3.14-fold, main frequency and amplitude became more pronounced, though jet speed marginally decreased (1.89%). Higher excitation frequencies didn't significantly curb speed. The ultrasonic excitation bolstered energy transfer and vortex feedback, intensifying shear and raising vapor phase content (0.5 ≤ y/r₂≤ 0.81) in the outlet. The ability of self-excited oscillating cavitation waterjets can be significantly improved. The research results can provide theoretical basis for the application of Helmholtz type self oscillating jet.

In order to study the internal flow field and induced pressure pulsation phenomena at the inception of cavitation and to determine a reasonable critical cavitation criterion, this paper conducted cavitation experiment on a low specific speed centrifugal pump and carried out steady and unsteady CFD simulations based on the RNG k- ε turbulence model and Rayleigh-Plesset cavitation model. The errors of efficiency and head are within 3%. Energy performance, flow field, and pulsation analyses were conducted under both non-cavitating conditions and different degrees of cavitation. The results indicate that the overall flow state is stable, and that the transport and collapse of local bubbles cause turbulent dissipation, leading to low-frequency pressure pulsation when cavitation triggers a 1% efficiency drop. When the head drops by 3%, the flow state in the pump is disturbed with vortex and large energy loss, and the wide band pressure pulsation which is easy to cause the vibration and noise of the pump body is induced. In the design of low-specific-speed centrifugal pump, it is recommended to set the critical cavitation margin to the device cavitation margin and above when the efficiency is reduced by 1% to ensure the stable operation of the pump. The research results can provide reference for the optimization design of low specific speed centrifugal pumps.

In response to the problem that existing smart damper air flow measurement models cannot accurately describe the relationship between damper angle and air flow. Based on the Bernoulli equation to analyze the functional relationship between damper angle and flow coefficient. The rotation of the damper blade inevitably changes the airflow distribution inside the pipeline. The change in damper angle will affect the flow coefficient. The damper angle compensation is added to the flow measurement model. A new air flow measurement model is built using regression analysis. The flow value can be calculated based on the pressure difference measured by the average pitot tube and the corresponding damper angle. This paper proposes a parameter acquisition method, which sets the frequency range of the fan based on the flow range of the damper, fits the parameter values using the least squares method, and verifies the model. If the flow measurement error is less than 10%, the parameter setting is accurate. Experimental verification was conducted on circular dampers with diameters of 100, 150 mm, as well as square dampers with dimensions of 200 mm×120 mm, based on the smart air flow calibration platform. The results indicate that based on the new flow measurement model, the maximum flow measurement errors of the three different models of dampers are 10%, 6.1%, and 6.6%. Accurate flow measurement can still be achieved by changing the input air volume within the range of 0° ~70° valve angle, effectively solving the existing problem of flow measurement. This proves the feasibility and universality of the new air flow measurement model. The accuracy of flow measurement will directly affect the operation effect of smart dampers and the precision of flow control. The building of the new model provides technical support for precise control and performance improvement of variable air volume systems.

In order to investigate the impact of thermal reservoir seepage on the heat transfer characteristics of medium-deep borehole heat exchanger (MDBHE), a transient heat transfer model for both the inside and outside of the borehole was established. The finite volume method (FVM) is employed to calculate the transient temperature in different regions inside and outside the borehole, and the results were compared with field test data to validate the accuracy of the proposed model and algorithm. The results show that compared with the condition without geothermal water seepage, the scenario with a thermal reservoir thickness of 400 m and a seepage velocity of 10×10^-7 m/s showed an increase of 5.5 ℃ in the temperature difference ΔT between the inlet and outlet of the pipe and a 16.22% improvement in the average energy efficiency coefficient . Additionally, when the seepage velocity is 10×10^-7 m/s and the thermal reservoir thickness increases from 50 to 600 m, the average heat transfer power per unit buried depth during the heating period rises by 81.92%. Furthermore, with a reservoir thickness of 600 m, the stratum temperature recovery rate during intermittent periods reaches 99.43%. The calculations demonstrated that as the thermal reservoir seepage velocity and the thickness of the thermal reservoir increase, there is a corresponding enhancement in the heat exchange performance of the MDBHE and in the temperature recovery rate of the stratum. These findings provide theoretical support for the efficient operation and practical engineering application of MDBHE in complex geological conditions.

Food quality is an important indicator to evaluate the performance of refrigerated display cabinets, and the temperature of food area directly affects the freshness, safety and shelf life of food. At present, the open refrigerated display cabinet has the problems of high energy consumption and substandard food quality. This paper summarizes and analyzes the research progress of open refrigerated food display cabinets from three aspects:air flow optimization, refrigeration system improvement and cabinet improvement. Firstly, the research of air flow optimization is introduced in detail, including optimizing the structure of the air supply and return port, and installing the wing-type deflector structure to improve the performance of the air curtain and the temperature uniformity in the cabinet. Secondly, the research progress of refrigeration system improvement is reviewed, including evaporator defrosting optimization, heat exchanger structure improvement and refrigerant replacement. Finally, the application of natural cold source, phase change material, heat pipe technology and load prediction in open refrigerated display cabinets is discussed. The introduction of natural cold source can significantly reduce the energy consumption of the cabinet. The application of heat pipe to improve the air state of the evaporator inlet and outlet of the display cabinet, and improve the operating efficiency of the cabinet.