The stainless steel flat plate solar collector is a new type of collector that has a longer lifespan in high-temperature and high-humidity environments. When using stainless steel as the base material of the collector, the microchannel structure is typically employed to increase the heat transfer area and compensate for the lack of heat transfer coefficient of stainless steel. However, the shape of the channel section in microchannel structures affects the flow resistance of the heat transfer medium. This article presented the equation for the optimal feature size of the channel, obtained through fluid theory analysis of the stainless steel flat plate collector. The study analyzed the impact of different section parameters on the flow distribution and pressure drop characteristics of the medium in the channel through numerical simulation. The results showed that for a certain inlet flow rate, the cross-sectional geometry of the microchannel heat-absorbing plate determined the parameters such as the type of core cross-section, the degree of wall urgency, and the geometrical length of the microchannel, which in turn affected the distribution of the fluid in the flow channel and the energy loss. The optimal thermal performance of the stainless steel collector was observed when the width of the micro-channel was 8.7 mm and the corrugation height of the tube group was 3.00 mm.

The problem of massive discharge of livestock wastewater is becoming more and more severe, causing irreversible damage to the ecological environment, and how to treat livestock wastewater efficiently and rapidly deserves to be studied in depth. In this work, CuO/granular activated carbon (GAC) loaded catalysts were prepared and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption/desorption techniques, and X-ray energy spectroscopy (EDS). The results showed that CuO was successfully attached to the GAC surface with good adsorption performance. The effects of catalyst dosage, H2O2 dosage, initial pH, microwave power and microwave irradiation time in different reaction systems on the degradation efficiency of chemical oxygen demand (COD) in wastewater were investigated, and the orthogonal experiments were used to explore the importance ranking of these factors. The highest degradation rate of COD was found to be enhanced by 12.1% in the reaction system of CuO/GAC, and the initial pH had the greatest effect on the COD removal rate. The combined MW/catalyst/H2O2 method used in this work provided a rapid and effective degradation of COD in wastewater, which can be helpful for reference in other microwave catalytic oxidation studies.

Curtain walls are widely used in high-rise office buildings, but the curtain wall enclosure significantly impacts building energy consumption, which contradicts China's dual carbon goals. This article proposes a ventilated energy-productive wall, with cogeneration to replace the curtain wall in order to reduce energy consumption. A ventilated energy-productive wall consists of a photovoltaic module, an air channel and a curtain wall, which performance is closely related to the structure and size of the air channel. According to the physical model of the ventilated energy-productive wall, a mathematical model is established and solved to analyze the airflow characteristics within the air channel and the heat transfer characteristics of the system. Numerical results show that the inner surface and average temperature of the photovoltaic panel are reduced by a maximum of 7.12 % and 2.12 % respectively by adding an air channel. The maximum temperature drop occurs in the 200-mm-thick air channel, and its outlet temperature drop is approximately 6.14 % lower than that of a 140-mm-thick air channel. An energy room is built based on the optimization results with a 200-mm-thick air channel in the ventilated energy-productive wall. At the peak moment, the average testing temperature on the inner and outer surfaces of the photovoltaic module are 50.12 degrees C and 48.9 degrees C, respectively, and the average temperature in the air channel is 38.2 degrees C. The numerical results agree well with the experimental results with an error not exceeding 5 %.

As a new type of building material for plants, photovoltaic roof building materials can be used as roofs of ordinary plants to reduce damage caused by secondary construction to the roofs, and can also absorb and utilize solar radiation to make full use of renewable energy. This article combines photovoltaic modules with air channels to form building material structures with ventilation ducts, establishes physical and mathematical models for photovoltaic roofs in three different inlet modes, and studies the flow and heat transfer characteristics inside air cooling integrated photovoltaic roofs. The simulation results show that the staggered-overlap-joint waterproof double-inlet photovoltaic roof can prevent rain and snow infiltration, and meanwhile, has a cooling effect on the PV panels significantly better than that of the traditional single-inlet air cooling system and the ordinary parallel double-inlet system, and its temperature difference between the inner and outer surfaces of the PV panels is increased by 19.88% compared to the traditional single-inlet air cooling system and by 15.12% compared to the parallel double-inlet system at the maximum. When the included angle between the PV panels of the staggered-overlap-joint waterproof double-inlet photovoltaic roof and the roof is 3 degrees, the change in average temperature difference between the inner and outer surfaces of the PV panels is maximum, which is increased by 3.88% compared with that at 2 degrees. The thickness of the air channel has small influences on the temperature change inside the air channel, the temperature difference between the inner and outer surfaces of the PV panels, and the outlet temperature. When the thickness increases from 50 mm to 200 mm, the change in outlet temperature does not exceed 0.3 K, but the increase in thickness of air layers increases the airflow velocity, which helps to take away more heat.

In order to improve the efficiency of the conventional serpentine solar air heaters, this article proposed a serpentine solar air heater containing a triangular spoiler. A 3-D verified mathematical model of serpentine solar air heaters with triangular spoilers was established. The results showed that the arranging triangular spoiler had a positive effect on enhancing the thermal performance of solar air heaters. It could be seen from the velocity and temperature contours that the triangular spoiler could reduce the intensity and area of the vortex zones, and hence decrease the temperature dead zone in the flow channel. The collection efficiency reached its peak value when the angle of triangular spoiler was 64 degrees. Compared with the nontriangular spoiler, the collection efficiency was increased by 4.4% similar to 6.2%. In general, the optimal angle of triangular spoiler was determined to be 40 degrees by comprehensive analysis of effective efficiency.

Taking the solar air collector with vortex channel as the research object,the thermal per-formance and economy of five kinds of coated collectors are analyzed by simulation method.The research ob-jects are black nickel coating,black chromium coating,cobalt oxide black coating,cermet thin film coating and titanium oxynitride blue film coating.The effect of the coating on the thermal performance of the collector is relatively small,and the influence on the investment re-covery period of the collector is relatively obvious.The heat gain cost per unit air of five kinds of coated col-lectors is lower than the conventional electricity price.Considering the thermal performance and economy of the collector,the black nickel coating is the ideal choice.

In practical engineering applications, natural air cooling is often utilized for photovoltaic (PV) facades. However, the natural-air-cooling method is not effective at cooling PV wall panels, and the high temperatures accumulated on the surface of PV panels not only affect the electrical efficiency and service life of the PV modules, but also increase the energy consumption of the building. In this paper, we propose the vertical installation of heat dissipation fins in naturally ventilated PV wall panels. We used ANSYS Fluent to establish the simulation model of naturally ventilated PV wall panels and validate it. By simulating the air-cooled channels in PV wall panels with different sizing parameters, the temperature and flow rate variations were comparatively analyzed in order to optimize the air-cooled-channel sizes. The results show that installing the fins vertically in the air-cooled channel provided better cooling for the PV panels and enhanced the air heat collection effect. Additionally, it improved the airflow rate in the channel. As the thickness of the finned air-cooled channel increased or the width decreased, the temperature on the surface of the PV panels showed a decreasing trend. Compared to the flat-plate air-cooled channel, the finned air-cooled channel, with a thickness of 100 mm and a width of 20 mm, decreased the peak and average temperatures of the PV-panel surface by 3.9 °C and 8.1 °C, respectively, and increased the average temperature of the air at the outlet by 11.2 °C.

The drying characteristics of bamboo shoot slices were experimentally studied in a hot air drying system. The individual and combined influence of air temperature, velocity, and slice thickness on the drying process was analyzed. The chromatic aberration and rehydration ratio were used as response indicators, and a 17-group experimental optimization of the drying process was carried out using a response surface methodology. According to the optimization analysis, a hot air temperature of 60.4 °C, an air velocity of 0.4 m/s, and a slice thickness of 0.2 cm were the optimal conditions for hot air drying of bamboo shoots. The predicted rehydration ratio and chromatic aberration of the dried bamboo shoot slices were 10.46 and 12.03, respectively. A validation experiment was conducted under optimum conditions to confirm the applicability of the models.

直膨式太阳能热泵系统的集热蒸发器通过吸收太阳辐射,使冬季工况下热泵的性能得到有效提高,减少了电能消耗,得到了广泛应用.通过实验测试了直膨式太阳能热泵系统冬季工况下的性能参数,讨论了单日内白天在太阳辐照下热泵性能的变化.分析发现,集热蒸发器内制冷剂进口温度随太阳辐照度迅速升高,在正午时刻之前,进口温度可由0.1℃升至10.3℃.系统过热度波动维持在约0.3℃以内之间.当进口压力达到单日内极值418.8 kPa时,系统制冷剂流量以及制冷量较初始时刻分 别增加1.76 kg/h、168.2 W.系统得热量则呈现出先增后降的趋势,正午时刻达到最大得热量2 199.55 kJ.太阳辐照度由363.31 W/m2变化到585.39 W/m2,集热蒸发器有效集热率由1.01减至0.41.日均太阳辐照度变化200 W/m2时,COP由1.61升高到2.93.建立了制冷剂蒸发温度、冷凝温度与COP之间的函数关系COPa=6.01-0.284ΔT0689.

以石蜡作为相变材料,在填充率一定的前提下,分析同心套管相变蓄热装置(以下简称蓄热装置)内管数量对石蜡熔化过程的影响.以4内管为基准,考虑石蜡熔化时间、单位长度内管换热面积,确定最优的内管数量.石蜡的温度变化先快后慢,最后趋于稳定.时间相同时,内管数量越多,石蜡平均温度越高.相同时间,不同内管数量蓄热装置横截面的石蜡液相率均呈上大下小.相同时间,内管数量越大,蓄热装置内未熔化的石蜡越少.在石蜡液相率趋于稳定前,内管数量越多,相同时间石蜡液相率越大.蓄热装置的最优内管数量为10.

This paper aimed to analyze the effect of the number of longitudinal baffles on flow and heat transfer characteristics of spiral solar air heaters (SSAHs). According to the analysis of velocity contours, the results showed that the velocity gradients that appeared at the place of inlet and outlet were contributed to the size difference between inlet/outlet and cross-sectional area of the channel, and the velocity gradients that appeared at the turnings were caused by the phenomenon of boundary layer separation, all which were contributed to increasing the pressure loss of SSAHs. Furthermore, it could be obtained that the collection efficiency firstly increased with about 2 longitudinal baffles to a peak value , then reduced, which proved that the positive effect of the Q(ab) increased by placing more longitudinal baffles would not compensate the negative effect of increasing the Q(L) by placing more longitudinal baffles. In accordance with the analysis of the effective efficiency and economic benefits, the SSAH with 2 longitudinal baffles was an optimal structure. To better predict the pressure loss and collection efficiency of SSAHs with the different number of longitudinal baffles, the correlations of Nu and the pressure loss of SSAHs were obtained by the least square method.