To address the issue of unreasonable buried pipe length design in ground-source heat pump projects, a three-dimensional dynamic simulation platform was developed. The reasonableness of the buried pipe length was evaluated by comparing the simulated outlet temperature with the designed outlet temperature based on specifications. Using a building in Beijing as a case study, the effects of soil thermal properties and borehole-related parameters on the design error in buried pipe length were analyzed. A sensitivity analysis further examined the impact of these factors. Results indicate that the relative error in buried pipe design length increases with rising soil thermal conductivity, soil volumetric heat capacity, borehole depth, and borehole spacing. Relative error ranges were 10.7%-27.3%, 8.0%-23.8%, 7.3%-12.5%, and 12.5%-17.4% for the respective factors. Sensitivity analysis revealed soil thermal conductivity as the most significant factor influencing pipe length, with a quantitative index of 0.909. Other influential factors, in descending order, were soil volumetric heat capacity, borehole spacing, number of borehole columns, and borehole depth.

A composite cold storage phase change material (PCM) based on Na₂SO₄·10H₂O and Na₂HPO₄·12H₂O was developed to meet the temperature requirements of cold storage air conditioning. The phase change temperature was 8.3 ℃, with a latent heat of 151.3 kJ/kg, representing a 14.24% increase in latent heat compared to previous works. Additionally, a novel thermal energy storage device utilizing spherical encapsulated PCM within a packed bed was proposed. A three-dimensional physical model of the packed bed was constructed using EDEM software to study the effects of sphere capsule size, inlet temperature, and heat transfer fluid (HTF) flow rate on the system's thermal performance. Results show that reducing the sphere capsule size, lowering the HTF inlet temperature, and increasing the HTF flow rate accelerate the thermal energy storage process and reduce charging time. For instance, when the HTF inlet temperature increases from 2 ℃ to 4 ℃, the packed bed's cold storage capacity and density decrease by 5%, the average cold storage rate drops by 41.93%, and the pressure drop remains relatively constant. However, the effect of sphere capsule size on thermal energy storage capacity and density lacks a clear trend and depends on specific engineering applications. These findings offer theoretical guidance for the practical application and broader use of packed-bed thermal energy storage systems for air conditioning.

As a core heat exchange component in forced-draft cooling towers, the performance of packing material significantly impacts the power consumption of the equipment. In this study, an experimental platform for crossflow cooling tower packing was developed to examine the effects of wind speed, water spray density, and packing height on the heat and mass transfer performance and resistance characteristics of herringbone corrugated packing. Empirical formulas were derived to analyze fan power consumption in crossflow cooling towers. Results reveal that heat and mass transfer performance improves with increased wind speed and water spray density and decreased packing height. Wind speed was found to be the most influential factor; increasing wind speed from 0.96 m/s to 2.05 m/s raised the mass-transfer coefficient by 70%. At low water spray densities, increasing the density significantly enhanced heat and mass transfer. Air resistance in the packing zone increased with air velocity, approximately proportional to the 1.68-1.91 power of wind speed. When the cooling water volume flow rate was 70 m³/h, sacrificing 20% of heat exchange capacity and reducing the inlet-outlet temperature difference from 5 ℃ to 4 ℃ reduced power consumption by approximately 71%. To maintain a power consumption ratio of 0.035 kW·h/m³, lowering the approach temperature from 4 ℃ to 3 ℃ required a 31% reduction in cooling water volume flow rate.

The drying process of a heat pump clothes dryer (HPCD) has complex characteristics such as strong coupling (the thermal cycle of the refrigerant side is coupled with the drying cycle of the air side), time variation (the system operating parameters change with drying time), and integration (limited space integrating evaporator, condenser, fan, compressor, etc.), and such complexity makes theoretical analysis of the drying performance of HPCD difficult. Based on certain simplifications, this study analyzes the effects of different compressor capacities and fan airflows on the moisture extraction rate per unit time (MER) and moisture extraction rate per unit energy consumption (SMER) of the HPCD. Under the same airflow, the SMER increases first and then decreases with the condenser discharge air temperature and evaporator discharge air temperature, when the discharge air temperature of the condenser is between 20 ℃ to 80 ℃ and the discharge air temperature of the evaporator is between 10 ℃ to 50 ℃. For the HPCD analyzed in this paper, when drying a half load (5 kg) of clothes, theoretical calculations identified an optimal condenser discharge air temperature of 53 ℃ and an evaporator discharge air temperature of 27 ℃ that maximized the SMER. The optimal temperatures are related to the COP of the heat pump system and the mass and heat transfer capacity of air with clothes. Under the same evaporator discharge and condenser discharge temperatures, within the airflow range of 0.02~0.08 kg/s, the SMER first increases and then decreases with the airflow. There is an optimal working airflow of 0.047 kg/s that maximizes the SMER, which is related to the drum power and the airflow resistance characteristic of the clothes dryer. According to methods for measuring the performance of tumble dryers for household use, testing verified that the theoretical analysis results were consistent with experimental tests. This research method and its conclusions provide theoretical guidance for the design and optimization of HPCD.

Helium throttling refrigeration technology is a key cooling method used in liquid helium temperature zones in space. Research on the rapid cooling of chillers coupled with large heat capacity loads is important for the efficient operation of large heat capacity loads. To clarify the cooling characteristics of helium throttling chillers under different rapid cooling schemes, cooling experiments with no additional measures scheme, room-temperature valve bypass scheme, and thermal switch scheme were conducted based on GM pre-cooled helium Joule-Thomson chillers under different heat capacity loads. The experimental results show that the load-free pull-down times of the three schemes were 39.8 h, 20.5 h, and 19 h, respectively. Based on thermodynamics and heat transfer theories, the changes in the radiation, convection, heat conduction, and throttling source terms during no-load cooling were quantitatively analyzed, and the reasons for the difference in cooling time of helium throttling chillers under different schemes were explained. With a simulated load of 0.136 kg of copper, schemes of the room-temperature valve bypass and hot switch were adopted, and the corresponding cooling times were 25.5 h and 20 h, respectively. The experimental results show that the cooling effects of the thermal switch and room-temperature valve bypass scheme are essentially the same for the cooling of a small heat capacity load. Therefore, thermal switch cooling has significant advantages for large-heat-capacity load cooling.

Capillary mat heat exchangers are increasingly used in transportation energy tunnels owing to their large heat-transfer area and uniform temperature. Thermal energy tunnels, a new type of energy tunnel, differ from transportation energy tunnels because of the heat source inside such tunnels. To examine the feasibility of applying capillary mat heat exchangers in thermal energy tunnels under endothermic conditions, heat transfer performance was experimentally investigated using a 1∶1 intermittent operating mode. The results showed that the higher the initial air temperature (T₀) in the tunnel, the greater the heat flux. With the inlet temperature of circulating water (t_in) fixed at 5 ℃, as the temperature difference between T₀ and t_in increases by 10 ℃, the heat flux increases by 45.9%. The heat flux also increases with the increase of circulating water velocity (u); whereas u increases up to 0.1 m/s, the heat transfer rate saturates and approaches 187.22 W/m². The lower the t_in is, the greater the heat flux. When the T₀ is 50 ℃ and the u is 0.075 m/s, for every 1 ℃ increase in the t_in, the heat transfer rate decreases by 2.04%.

To reduce energy consumption in temperature- and humidity-independent air-conditioning systems and enhance solar energy utilization, this study developed a solar-assisted desiccant wheel and adsorption cooling system (SDCS-A) using TRNSYS 18. System performance under Guangzhou's climatic conditions was analyzed by varying collector areas and tank volumes together with evaluating metrics such as system coefficient of performance (COP_sys), solar fraction (F_s), and primary energy consumption (E_p). These results were compared with those of a solar-assisted desiccant wheel and vapor compression cooling system (SDCS-C). Findings indicate that changes in collector area significantly influence F_s and E_p, with F_s increasing by an average of 12.18%, while variations in tank volume predominantly affect COP_sys, with a maximum difference of 0.1. Compared to SDCS-C, SDCS-A achieved 6.51% higher monthly average COP_sys, a 21.05% increase in F_s, and a 21.45% reduction in E_p during the cooling season. Furthermore, the system's performance across different climates was evaluated, demonstrating that Guangzhou offers more stable and higher monthly COP_sys values than Beijing, Shanghai, and Lhasa.

This study investigates the magnetocaloric properties and refrigeration performance of batch-prepared (La, Ce)(Fe, Mn, Si)₁₃H_y alloys. After heat treatment and hydrogenation, the Curie temperatures of M1, M2, and M3 were 292.9 K, 287.8 K, and 283.9 K, respectively, decreasing with higher Mn content. Arrott plots indicated an itinerant-electron metamagnetic transition. M2 exhibited the highest isothermal magnetic entropy change of 12.0 J/(kg·K) under a 2 T magnetic field, with a full width at half maximum of 11 K. Relative cooling capacities (RCP) were 110.2 J/kg, 132.0 J/kg, and 110.0 J/kg for M1, M2, and M3, respectively. Adiabatic temperature changes measured under a 1.5 T magnetic field were 3.48 K, 3.14 K, and 2.96 K for M1, M2, and M3, respectively. A maximum refrigeration temperature span of 16.9 K was achieved by cascading the alloys at an ambient temperature of 295 K.

Large cold storage systems play a significant role in economic development with substantial energy consumption and environmental impacts. To promote the green, low-carbon, and efficient development of cold storage, this study mainly focuses on refrigerant substitution, refrigeration system optimization, and the application of transcritical CO₂ systems with ejectors in large cold storage systems. The performance and energy consumption characteristics of different refrigeration systems were compared through a comprehensive annual hourly energy consumption analysis based on the cold storage demands at different temperatures and under various climatic conditions. The results show that the COPs of a transcritical CO₂ system integrated with specifically optimized ejectors are higher than that of the R507A system in all four cities for low-temperature (-32 ℃), medium-temperature (-8 ℃), and high-temperature (0 ℃) cold storages. However, it exhibited performance advantages over the R717 system only in cold climate zones, with the highest system COPs of 2.45, 4.86, and 5.98 for low, medium, and high-temperature cold storages, respectively. Considering the system′s annual energy consumption, the application of CO₂ transcritical systems in low, medium, and high-temperature cold storages in Beijing achieved energy savings of 7.9%, 10.1%, and 10.5%, respectively, compared to the R507A system. The energy savings of the R717 system were slightly higher than that of the CO₂ system in low-temperature cold storage, but the CO₂ system had more obvious advantages in medium- and high-temperature cold storage. The energy consumption of the CO₂ transcritical system also varied across climate zones. In the cold climate zone, the energy savings reached 9.3%, outperforming the R717 system, while in the hot climate zone, its energy savings dropped to 2.8%, slightly lower than that of R717. With the appropriate selection of temperature range and climate zone, the overall operational efficiency and energy-saving performance of the transcritical CO₂ system can surpass those of the R717 system. This study conducted a comprehensive analysis of the operational performance and energy consumption distribution characteristics of the CO₂ system and highlighted its applicability in different scenarios, providing important references for promoting and applying the system, which is crucial for achieving dual carbon goals.

Superhydrophobic surfaces, a new type of green material, exhibit promising application prospects in the field of anti-/de-icing. In this paper, the kinetic behavior of impinging droplets on surfaces with different temperatures (-25-16 ℃), different inclination angles (0°-60°), and different wettability (hydrophilic and superhydrophobic surfaces) is investigated through experimental comparisons. The variations of the droplet morphology, spreading factor, spreading time, and contact time are analyzed. The results show that the impinging droplets exhibit different kinetic behaviors after spreading due to the different inclination angles and wettability. The maximum spreading factor and spreading time on hydrophilic surfaces increase with the inclination angle. The variation of the spreading time on superhydrophobic surfaces follows the same trend as that on hydrophilic surfaces, while the maximum spreading factor decreases with an increase in the inclination angle, especially at T_s-25 ℃; Compared to hydrophilic surfaces, the impinging droplets have shorter spreading times on superhydrophobic surfaces, which can reach about 10 times at T_s=-25 ℃. Increasing the wall inclination angle breaks the symmetric bounce of the droplets on the horizontal superhydrophobic surface, thereby shortening the contact time of the droplets. This suggests that increasing the inclination angle can effectively inhibit the freezing of water droplets.