Topological fins can significantly improve heat transfer in latent heat storage units. In this study, a two-dimensional topology optimization model for a shell-and-tube latent heat storage unit was developed and experimentally validated. The optimal fin for different operating conditions and charge-discharge cycles was investigated. Box-counting dimensions and fin surface areas per unit length were used to characterize the topological fins. The results showed that increasing the charging time simplified the fin structures, whereas discharging times of more than 600 s extended the fin tips. For the 3 000 s charge-discharge cycle, the optimal fin increased the surface area per unit length by 80% and the discharge energy density by 37.6% compared to the fin for the 3 000 s charging process. The topological fin for a 300 s discharge-charge cycle with an extended branch resulted in a 7.7% increase in heat storage density.

A transcritical CO₂ heat-pump air-conditioning system has effective heating performance at low temperatures, and the variation of dynamic parameters during operation significantly affects the thermal comfort inside the passenger cabin. To study the comfort of the passenger compartment and the coupling law of the dynamic changes in the parameters of the transcritical CO₂ heat-pump air-conditioning system, a joint simulation model was built based on the one-dimensional simulation software GT-Suite and the three-dimensional computational fluid dynamics (CFD) software STAR-CCM+. The three-dimensional cabin model can provide accurate real-time state parameters of the supply and return air for a one-dimensional simulation system of heat-pump air conditioners. The results show that the temperature distribution of the thermal environment of the passenger compartment is relatively non-uniform, necessitating the application of the weighted predicted mean vote (PMV) to evaluate this non-uniformity. In a multi-PID control transcritical CO₂ automobile heat pump air conditioning system, a control method based on the weighted PMV comfort model can maintain the regulation and stability of the system's target parameters. Under ambient temperature conditions of 43 ℃ in cooling mode, the control method can reduce the compressor's power consumption by 9.4%. At an ambient temperature of -10 ℃ in heating mode, this method can reduce compressor's the power consumption by 17.9%. This control method can reduce the power consumption of the system compressor while satisfying comfort requirements, constituting a highly efficient energy-saving strategy.

With the development of cold chain Internet of Things (IoT) technology, real-time temperature monitoring and data sharing have become important means to improve the efficiency of chilled meat supply chain management. In this paper, a strategy for optimizing time and temperature coordination based on the cold chain IoT was proposed to improve the operational efficiency of the chilled meat supply chain. Based on predictive microbiology and system reliability theory, this study investigated the effects of time and temperature on the quality of chilled meat. A quality-change model for chilled meat and an energy consumption model for the chilled meat supply chain were developed. To illustrate this approach, a case study of a chilled chicken supply chain was conducted. The findings revealed that there is an optimal level of freshness in the chilled meat supply chain that maximizes the benefits of the supply chain. If the freshness level in one stage deviates from this optimal value, subsequent stages can adjust the time and temperature to achieve maximum supply chain efficiency.

This study utilizes machine learning techniques to conduct an in-depth analysis of time-series historical data on energy consumption in buildings. A generalized model identification method was developed using an optimization algorithm based on black-box models. The final identification model was determined after optimizing three machine learning methods, including polynomial regression, artificial neural networks, and extreme gradient boosting. A near-zero energy office building in Beijing is the primary focus of this study. Using historical building data and simulation data of the heating system in TRNSYS, load prediction and equipment energy consumption models were established using the developed model identification method. During deployment, the predicted R² value and total energy consumption deviation were 0.87 and 5.18%, respectively. The results demonstrate that the prediction models established through this method possess high accuracy, providing a reliable basis for subsequent system energy consumption optimization.

Solution absorption energy storage is a new energy storage and release technology characterized by high energy storage density, low heat loss, good mobility, and long-term energy storage. Energy storage density and energy storage efficiency are the key indexes for measuring the energy storage capacity of absorption energy storage systems and the key parameters for evaluating the energy conversion efficiency of absorption energy storage systems, respectively. Based on thermodynamic principles, the energy storage characteristics and applicability of absorption energy storage systems were investigated using six types of absorption solutions under different conditions. The results show that both energy storage density and energy storage efficiency increase with an increase in heat source temperature and cooling water temperature and decrease with solution concentration. At a heat source temperature of 70-120 ℃ and condensing temperature of 24-36 ℃, NaOH-H₂O has the largest energy storage density and efficiency, CaCl₂-H₂O has the smallest energy storage density and efficiency, and LiBr-H₂O has the widest applicability of temperature range.

As the driving component of a valved linear compressor, the matching relationship between the motor force and gas force directly affects the performance of the compressor. A simulation model of the linear motor was established based on the equivalent gas-force model. In addition, a test bench for the valved linear compressor was constructed to analyze both the simulation and experimental results under various working conditions. This study aimed to investigate the performance of a compressor across different operating scenarios while verifying the reliability of gas force linearization. When the inflation pressure and piston pressure were 0.2 MPa and 5 mm, respectively, the resonance frequency of the experiment and simulation was 50 Hz, and the motor efficiency was 84.3%. The maximum relative errors of the input work, voltage, current, and motor efficiency were 25.8%, 21.7%, 22.7%, and 13.5%, respectively. This indicates that the motor efficiency of the compressor is related to its resonance frequency and that the motor efficiency of the compressor is the highest when the resonance frequency is consistent with the operating frequency. The simulation model of the linear motor is reliable, and the calculation results for the gas load are relatively accurate.

Nucleator nozzles play an important role in promoting the rapid nucleation, crystallization, and snow formation of artificial snow droplets. A visual experimental platform was designed to investigate the gas-liquid two-phase flow process inside the nucleator nozzle and its influence on atomization behavior. The results showed the presence of a two-phase annular flow within the nucleator nozzle and a continuous hollow-cone spray field outside the nucleator nozzle. As the gas-liquid pressure ratio (Φ_GL) increases, the interfacial disturbance waves at the gas-liquid interface of the internal flow gradually disappear. As the air core occupied more space, the liquid film thickness gradually decreased and became uniform and stable. This markedly improved the atomization efficiency and quality. When the Φ_GL was increased from 20% to 67%, the uniformity and stability of droplet distribution increased by 17% and 60%, respectively. This research offers important guidance for the structural design of high-performance atomized components.

The refrigeration industry is advancing towards environmentally friendly, efficient, and safe alternative refrigerants. To analyze compressor performance with various refrigerants, this study proposes a modified semi-empirical model with 13 characteristic parameters. Experiments were conducted with R22, R507, and R744 under variable operating conditions to identify parameters and validate the model. The experimental and simulated results showed strong agreement, with average relative errors of 2.07% for input power and 1.17% for mass flow rate. Using a typical operating condition, the losses and efficiencies of different refrigerants were compared at various frequencies. Results indicate that R744, with the lowest pressure, leakage, and power losses, demonstrated superior performance. While R507 and R22 showed similar efficiencies, the efficiency of R507 declined significantly at frequencies above 50 Hz due to increased pressure losses. This study provides a theoretical basis for optimizing compressor designs for various refrigerants.

Refrigerant leakage is a frequent and costly fault that deteriorates the normal operation of a chiller; however, it is difficult to measure directly. This study proposes a data mining- and key-feature-based approach for the soft measurement of refrigerant leakage. Random forest importance ranking and distance correlation coefficients were used to select the characteristic features, and a support vector regression (SVR) soft measurement model was established to measure leakage quantitatively. The proposed model was validated through a leakage experiment conducted on a screw chiller with a rated cooling capacity of 1 440 kW and a refrigerant charge of 330 kg. The results showed that the SVR soft measurement model established on the three selected key features achieved significantly improved performance. The model had a root mean square error (RMSE) of 0.844 kg and a mean absolute error (MAE) of 0.734 kg, outperforming the other three feature subsets.

Because the piston volume of a scroll compressor with variable base circle involute can be reduced under the premise of obtaining the same cooling capacity, it can satisfy the compact and lightweight requirements of vehicle air conditioning compressors. To improve the isentropic and volumetric efficiencies of the scroll compressor, a mathematical and geometric model of the scroll disc with a variable base circle involute was established. With the variable index k and the modified increment δ₀ as variables, the internal flow field of the scroll compressor is numerically simulated, and fluid dynamic analysis is conducted. The numerical results show that when the parameters of the variable base circle line are k=1 and δ₀=-0.03 mm, the specific dissipation rate of the fluid in the compressor working chamber is 180.28 s^-1, which is 103.11 s^-1 lower than the 283.39 s^-1 of the flow field in the fixed base circle compressor. The isentropic efficiency of the scroll compressor can be improved by reducing energy loss due to the turbulent kinetic energy dissipation. The performance of the scroll compressor for electric vehicle air-conditioning was tested. Compared with the fixed base circle scroll compressor, the input power of the variable base circle scroll compressor with k=1 and δ₀=-0.03 mm decreases by 1.392%, and the performance coefficient COP_el increases by 4.204%.