To improve airflow-distribution controllability and heating thermal-environment performance in Vertical Single-row Inclined Slit Ventilation (VSISV), splitter plates were installed in the main supply duct to guide internal flow and redistribute multi-slit jets. A modular adjustable VSISV test duct was developed, and slit outlet flow rates were measured to validate the numerical predictions. The effects of splitter-plate parameters on the duct flow field, slit flow-splitting ratios, and indoor airflow organization were then evaluated through numerical simulations. Data-driven screening identified equivalent total pressure loss (Δpeq), draft rate (DR0.1), and head–ankle temperature difference (Δt1.1-0.1) as the core metrics, and multi-objective optimization was performed using an Extra Trees surrogate coupled with NSGA-II. The results showed that upstream splitter plates tended to induce a dominant split, increasing jet velocity and indoor mixing but raising Δpeq and DR0.1, whereas plates located at mid-to-lower slit positions mainly provided coordinated adjustment with lower penalties. The optimization further indicated that splitter-plate regulation involved a trade-off among resistance penalty, draft risk, and stratification control, rather than simultaneous improvement in all metrics. Owing to the inherent top-to-bottom staged splitting in VSISV, splitter plates mainly strengthened upstream and midstream flow redistribution, while their ability to enhance lower-zone supply remained limited.

In order to alleviate the energy crisis caused by high-temperature climates, a radiation sky cooler (RSC) device that utilizes sky radiation as a cold source is proposed. Based on multi-physics simulations, the influences of inlet velocity, ambient wind speed, ambient temperature, and solar irradiance on the heat transfer performance of the RSC are investigated. The results show that the cooling power exhibits an average enhancement of 7.3 % for each 0.1 m/s increment in inlet flow velocity. The cooling power exhibits an average enhancement of 22.38 % for each 1 degrees C increase in T-s-T-a. The cooling power decreases by an average of 6-7 Wm(-2) for each 100 Wm(-2) increase in solar irradiance. The cover-plate structure delays the onset of the critical irradiance by approximately 200 Wm(-2), shifts the peak ambient sensitivity by about 2 degrees C, and enhances the cooling power by roughly 20 %. The sensitivity ranking of the parameters is as follows: solar irradiance > ambient temperature > inlet velocity > ambient wind speed. The study elucidates the multi-parameter heat-transfer mechanisms of RSC and provides a theoretical basis for the design of passive cooling heat exchangers.

Impingement quick freezers are widely used because high-velocity, low-temperature air jets enhance convective heat transfer. However, the refrigeration units in quick-freezing tunnels consume substantial energy, and nonuniform airflow distribution can cause asynchronous freezing and energy waste. Therefore, optimizing the tunnel structure and internal flow field is urgently needed to improve system performance. In this study, computational fluid dynamics (CFD) was employed to investigate the airflow organization in a conventional single-unit impingement belt tunnel freezer. The effects of key structural parameters, including the return-air path, the distance between the nozzles and the frozen product surface, the plenum chamber volume, and the number and arrangement of air outlets, on airflow distribution were systematically analyzed. The results indicate that optimizing the return-air path significantly enhances airflow uniformity, with the standard deviation of airflow velocity reduced from 1.69 m/s to 1.05 m/s, corresponding to a 37% improvement in flow-field uniformity. Adjustments to the nozzle-to-product distance and plenum chamber volume primarily influence airflow intensity; specifically, the airflow velocity over the product surface increases with decreasing nozzle-to-product distance, but decreases with increasing plenum chamber volume. Moreover, increasing the number of air outlets with appropriate layout enhances airflow velocity by 12%-14% while maintaining favorable uniformity. These findings provide robust theoretical support and practical guidance for airflow optimization in impingement belt tunnel freezers, contributing to the development of more energy-efficient and high-performance quick-freezing systems.

Impingement quick freezers are widely used because high-velocity, low-temperature air jets enhance convective heat transfer. However, the refrigeration units in quick-freezing tunnels consume substantial energy, and non-uniform airflow distribution can cause asynchronous freezing and energy waste. Therefore, optimizing the tunnel structure and internal flow field is urgently needed to improve system performance. In this study, computational fluid dynamics (CFD) was employed to investigate the airflow organization in a conventional single-unit impingement belt tunnel freezer. The effects of key structural parameters, including the return-air path, the distance between the nozzles and the frozen product surface, the plenum chamber volume, and the number and arrangement of air outlets, on airflow distribution were systematically analyzed. The results indicate that optimizing the return-air path significantly enhances airflow uniformity, with the standard deviation of airflow velocity reduced from 1.69 m/s to 1.05 m/s, corresponding to a 37% improvement in flow-field uniformity. Adjustments to the nozzle-to-product distance and plenum chamber volume primarily influence airflow intensity; under these conditions, the airflow velocity can be reduced by up to 38% without altering the overall flow-field pattern. Moreover, increasing the number of air outlets with appropriate layout enhances airflow velocity by 12%–14% while maintaining favorable uniformity. These findings provide robust theoretical support and practical guidance for airflow optimization in impingement belt tunnel freezers, contributing to the development of more energy-efficient and high-performance quick-freezing systems.

This study investigates a novel ventilation technology called vertical single-row inclined slit ventilation (VSISV). Numerical simulations were employed to analyse the effects of slit quantity, supply air flow and flow distribution strategies on indoor environment. Results show that increasing slit number improves vertical jet flow continuity but has limited effect on horizontal reach and overall temperature distribution. The VSISV system performs inadequately at low supply air flow rates, but as the supply flow increases, its performance gradually approaches that of the impinging jet ventilation (IJV) system. At high supply flow rates, its unique airflow circulation characteristics contribute to a more concentrated high-temperature distribution. By adjusting the thermal buoyancy length scale (lm) of the flow from the lowest slit to match that of the IJV system, an independent air supply flow distribution strategy for the slits in the VSISV system is proposed. This strategy significantly enhances the horizontal spread of the jet, thereby enhancing temperature uniformity, energy efficiency and indoor air quality. However, at high air supply rates, caution should be taken to prevent potential localised discomfort in the room's front zone, such as increased draft rate (DR) and predicted mean vote (PMV) issues.

With the increasing demand for cold-chain logistics, the inlet airflow organization of external condenser heat exchangers in refrigerated trucks plays an important role in heat-transfer efficiency and energy consumption. To address the problem that hot air rising from the engine compartment easily enters the windward side of the heat exchanger, causing local heat accumulation and uneven airflow distribution, a three-dimensional CFD model of a refrigerated-truck external condenser heat exchanger was developed. The effects of fan configuration, flowdeflecting baffle, fan rotational speed, and inlet air temperature on the windward-side airflow organization and temperature distribution were investigated. The results show that the top-mounted fan configuration performs better than the inclined fan configuration. After adding a flow-deflecting baffle to the top-mounted fan structure with a lower opening, the proportion of the 52-55 degrees C high-temperature region decreased from 40.84% to 24.44%, while the medium-temperature region increased to 32.15%. A baffle length of 150-170 mm provided a favorable balance among airflow guidance, temperature reduction, and engineering feasibility. Increasing fan speed enhanced forced convection, but the improvement became limited above 4000 r/min. Higher inlet air temperature significantly deteriorated the windward-side thermal environment; when the inlet temperature increased from 26 degrees C to 38 degrees C, the average windward-side velocity decreased from 1.838 m/s to 1.690 m/s, while the area above 39 degrees C increased from 0.124 m2 to 0.265 m2.

To address the challenges of insufficient heat source utilization and poor thermal matching in building heating systems with multi-temperature heating terminals, an integrated cascade large temperature-difference heating configuration combining a photovoltaic/thermal–air-source heat pump coupled heat source and two-stage water-source heat pumps is investigated. The system integrates source-side cascade heat extraction and load-side cascade heating to improve thermal energy utilization across different temperature levels. Simulation analyses were conducted to evaluate the effects of heat source temperature, operating mode, and control strategy on system performance, energy self-sufficiency, and economic feasibility. The results show that the cascade heat extraction strategy enables a large heat extraction temperature difference of 12.30 °C, thereby extending the utilization range of low-grade thermal energy. Under the load-side series configuration, the optimal performance is achieved at a heat source temperature of 34 °C and a control threshold of 40 °C, yielding a seasonal performance factor of 3.43. In addition, electricity generated by the photovoltaic/thermal subsystem supplies 33.90% of the seasonal electricity demand, with the maximum energy self-sufficiency ratio reaching 53.77% at the end of the heating season, significantly reducing dependence on grid electricity. The findings demonstrate that the integration of multi-source heat supply and cascade thermal utilization can effectively improve heating performance and renewable energy utilization, providing a solution for multi-temperature building heating applications.

This study investigates the performance of a Vertical Single-Row Inclined Slit Ventilation (VSISV) system under winter heating conditions. Response Surface Methodology (RSM) is applied to evaluate the influence of slit aperture configurations on indoor ventilation performance. A multi-criteria evaluation is conducted using the TOPSIS method, and the optimization results are validated using a Radial Basis Function Neural Network-Genetic Algorithm (RBFNN-GA) framework. The optimal configuration enlarges the lower slits while moderately restricting the upper slits (d1/d2/d3/d4 = 0.085/0.07/0.013/0.032 m). Compared with impinging jet ventilation (IJV) under the same supply conditions, Delta t1.1-0.1 and DR0.1 are reduced by 18.7 % and 9.9 %, respectively. The downward air circulation (Qz3) is enhanced by more than two orders of magnitude, and PMV0.1 shifts 26.3 % closer to thermal neutrality, demonstrating that the optimized VSISV system provides superior thermal comfort and airflow organization under winter heating conditions.

In heat pump drying (HPD) processes, closed-loop systems are widely used to recover latent heat from material moisture and utilize waste heat. However, during the later drying stages, the reduced moisture content in materials makes deep dehumidification challenging, leading to excessive temperature rise in the drying chamber and compromised product quality. To address these limitations, this study proposes a novel condensation-rotary wheel cascade dehumidification drying system, which enables low-temperature, high-temperature, and hybrid drying modes. This system overcomes the insufficient latent heat issue in closed-loop HPD while significantly reducing rotary wheel regeneration energy consumption through advanced material design. An experimental prototype was developed to evaluate its operational performance and dehumidification efficiency. Results indicate that the system stabilizes within 40 min, achieving a drying temperature of 50 degrees C and relative humidity of similar to 5 %. The system exhibits a coefficient of performance (COP) >= 4.80 and a dehumidification COP (DCOP) >= 2.68. Compared to conventional HPD, the integration of a dehumidification rotary wheel reduces energy consumption by 11 %, while achieving 20.2 % energy savings over traditional rotary wheel systems, demonstrating superior energy efficiency.

To address the issues of low efficiency, high energy consumption, and poor quality associated with traditional food drying methods, this study proposes a heat pump-low-temperature regeneration wheel collaborative drying system. This system offers advantages such as a fast drying rate, high food drying quality, and low energy consumption. To further investigate its drying characteristics, drying experiments were conducted on white radish slices at temperatures of 35 degrees C, 40 degrees C, and 45 degrees C. The results indicate that, compared to heat pump drying, the collaborative drying mode exhibits significant advantages: drying time was greatly reduced, with a minimum reduction of 60 min at all temperatures. The maximum drying rate increased significantly, ranging from 17.04 % to 19.51 %. Energy consumption was noticeably reduced, decreasing by 7.48 %-11.68 %. Moreover, the effective moisture diffusivity improved by 7.98 %- 11.49 %, product shrinkage decreased by 4.00 %-5.56 %, rehydration ratios increased by 3.25 %- 8.20 %, and sensory evaluation improved by 17.29 %-38.09 %. Additionally, based on the experimental data, the Wang and Sing model was determined to be the most suitable mathematical model for describing the collaborative drying process, exhibiting a coefficient of determination (R2) exceeding 0.999. This research demonstrates that the heat pump-low-temperature regeneration wheel collaborative drying system has significant potential for market application due to its high product drying quality and low energy consumption.

The indoor ventilation performance of an impinging jet ventilation (IJV) system with high-level placement in non-occupied zone was comprehensively investigated using numerical simulation methods. Combined with response surface methodology (RSM), the differences in thermal comfort and energy efficiency between high-level and low-level placements were quantified for different seasonal conditions. The results indicate that in summer, thermal buoyancy resistance is relatively low, and buoyancy facilitates the accumulation of cool air in the occupied zone, forming a comfortable ventilation environment. Minimal differences were observed between the ventilation environments induced by high-level and low-level air supply placements. Conversely, in winter, the warm airflow from the supply is significantly affected by buoyancy, often rising prematurely unless delivered with high inertial force, in which case high-level placement can achieve performance comparable to low-level placement. The quantitative analysis using RSM revealed that in summer, the thermal comfort and energy efficiency of both high-level and low-level placements were nearly equivalent, with high-level placement slightly outperforming in terms of thermal comfort, while low-level placement demonstrated marginally better energy efficiency. In winter, low-level placement exhibited clear advantages in heating ventilation performance. This study provides theoretical support for the efficient design of IJV systems.

A multi-objective optimization of the supply air inlet structure for Impinging Jet Ventilation (IJV) was conducted based on the Radial Basis Function Neural Network (RBFNN) and using a genetic optimization algorithm. The Predicted Mean Vote at the occupant's ankle level (PMV0.1) and the Energy Utilization Coefficient (Et) exhibited significant variability across different inlet structures, thus they were selected as optimization objectives. The predicted results showed substantial consistency with numerical simulations. Within the selected parameter range, the optimal PMV0.1 value was -0.17, and the optimal Et value was 3.57. Furthermore, by adjusting the weights of different optimization objectives, suitable structural parameters can be determined. It was also concluded that, for the given indoor ventilation conditions, the length of the supply air inlet structure should be shorter than its width to better enhance the PMV0.1 value in the areas surrounding occupants.

In order to mitigate the extreme climate change and improve the utilization of renewable resources, a solarground source heat pump system using return water of the district heating network as supplementary heating (SGSHP-DHNSH)has been proposed. This system compared with parallel and series connections of solar assist ground source heat pump systems for simulation and analysis. The results indicate that the SGSHP-DHNSH system raises the evaporation temperature, demonstrates a high rate of renewable energy utilization, and efficiently stores heat within the buried pipes. Notably, the soil temperature in the SGSHP-DHNSH system experiences only a 0.16 degrees C decrease, which represents reductions of 8 % and 9.8 % compared to the series and parallel systems, respectively. Furthermore, the system COP demonstrates a commendable improvement of 20 % and 13.7 %, the evaporator inlet temperature is higher than the series and parallel systems by 6.7 degrees C and 5.3 degrees C, respectively. Moreover, the total energy consumption throughout the heating season stands at 63 MW h, reflecting a substantial 24 % and 19 % reduction in comparison to the series and parallel systems, respectively. The SGSHP-DHNSH system plays a crucial role in improving the utilization rate of renewable resources and alleviating the soil heat imbalance caused by ground source heat pump operation.

The study investigates the drying characteristics of carrots under different coupling forms of airflow and high-voltage electric fields (parallel flow, PF, and cross flow, CF) using heat pumpelectrohydrodynamics (EHD) combined drying. The results show that, compared to single heat pump drying, the combined drying under PF mode reduces carrot drying time by 13.33 %-31.58 %, increases effective moisture diffusivity (Deff) by 17.80 %-32.32 %, increases specific moisture extraction rate (SMER) by 12.25 %-34.26 %. While the combined drying under CF mode reduces carrot drying time by 12.5 %-18.18 %, increases Deff by 7.27 %-13.14 %, increases SMER by 4.64 %-12.58 %. The improvements in parameters under the CF mode are weaker than those under the PF mode. Additionally, the beta-carotene content under PF mode is consistently higher than under CF mode. Based on the experimental results, the Modified Page model was improved, yielding an updated model MR = aexp(-(kt)<^>n), with an R2 value of up to 0.9999-1, which provides theoretical guidance for optimizing the heat pump-EHD combined drying process.

Abstract In this paper, the heat exchange process of a closed cooling tower with condensation inside the tube is analyzed. Combined with the calculation method of a traditional closed cooling tower, the thermal model and mathematical model of the whole coil closed cooling tower with condensation inside the tube are established. The fourth-order Runge-Kutta (RK4) method is used to write a program to solve the differential equation. A case is calculated to solve the heat exchange area and spray water temperature. Its feasibility for design reference is verified.

This article proposes an effective thermal management solution for electric vehicles by incorporating a low global warming potential (GWP) hybrid refrigerant R1234ze(E)/R134a/R32 (with a mass percentage of 85/10/5). By integrating R1234ze(E), the potential of substituting R134a with this mixed refrigerant in electric vehicle air conditioning for thermal analysis was analyzed. The findings are that R1234ze(E) exhibits a COP reduction of 0.51% compared to R134a, while R1234ze(E)/R134a/R32 showcases a coefficient of performance (COP) enhancement of 1.53% over R134a. The compressor exhaust temperatures of R1234ze(E) and R1234ze(E)/R134a/R32 are, respectively, 7.4 degrees C and 5.2 degrees C lower than those of R134a. R1234ze(E) demonstrates a volumetric cooling capacity similar to 26.3% smaller than that of R134a. However, the volumetric cooling capacity of R1234ze(E)/R134a/R32 aligns closely with R134a, facilitating convenient direct charging. R1234ze(E)/R134a/R32 proves to be an excellent refrigerant for applications in the thermal management of electric vehicles.

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Existing ventilation technologies often struggle to balance the limited airflow supply with the demands of indoor ventilation and air circulation in winter. This paper introduces a novel ventilation method, vertical single-row inclined slit ventilation (VSISV), which channels airflow through multiple inclined slits spaced at specific intervals along a vertical supply air duct. By ensuring continuity of the upstream and downstream slit jets, a continuous downward airflow is formed, enhancing both winter ventilation performance and indoor air circulation. The method was experimentally measured, with a focus on comparison to the IJV system. At the same airflow rate, it not only efficiently transports the supply air heat from the upper indoor area to the floor but also exhibits strong horizontal diffusion capability. The RNG turbulence model was selected for numerical simulation, focusing on indoor thermal comfort, air quality, and energy-saving potential. The results indicate that, at the same airflow rate, this method effectively maintains high indoor thermal comfort, directs airflow downward from the ceiling, reduces thermal stratification in the upper zone, achieves a more uniform and elevated indoor temperature, enhances indoor air quality, and demonstrates substantial energy-saving potential. This provides valuable insights for energy conservation, emission reduction, and the optimization in winter building ventilation systems.