For tunnels in cold or serious cold areas, the problem of leaking in the spring thawing period is very frequent, which will cause various tunnel diseases due to freezing. By using the surrounding rock geothermal energy in the tunnel project, especially the tunnel project below the permafrost layer, the cold area tunnel heat pump system is able to improve the overall heating energy efficiency as the side temperature regarding the heat pump evaporation increases, that furtherly serves the surrounding supporting building facilities. Inspired by this system and the active and passive coupling building technology, a heat recovery type of heat storage wall model is proposed in this research. By describing the heat transfer process regarding the heat recovery type of heat storage wall and carrying out the experimental research, its feasibility and effectiveness are verified. The results show that when the outdoor ambient temperature in Urumqi is −7~−15°C and the instantaneous total solar radiation reaches the range of 0~1108 W/m2, this kind of wall can create hot wall-near air whose temperature is 11.89°C higher than the ambient temperature for providing a high-quality air heat source for the air source heat pump when the temperature is low, thereby significantly improving the air source heat pump heating system efficiency. Without the photovoltaic and photothermal equipment, the heat recovery type of heat storage wall can make the utilization rate of solar energy reach 13% to 20%, even up to 36%.
In tunnel heating systems, phase change materials may minimize the consumption of conventional electric energy, which is very considerate in the field of tunnel heating in cold regions. Because of the phase change material’s poor heat conductivity, its annual growth rate heat absorption and release is slower; thus, the majority of phase change heat storage systems must improve heat transmission. In this study, a spiral metal ring is implanted in the paraffin to improve heat transmission to achieve this objective using a concentric sleeve-type paraffin heat storage device as a medium. Experiments were performed out in order to determine the effects of heating rate, hot fluid flow rate, and the use of a spiral metal ring on the heat storage and release process of a thermal storage device. In comparison to the paraffin thermal storage device, the embedding of the spiral metal ring accelerates the internal thermal performance of the composite heat storage device, resulting in a more uniform temperature distribution. When the thermal radiation heating rate is 60°C, 65°C, or 70°C during the heat storage process, the heat storage time of the composite heating storage device is reduced by 59.2 percent, 44.4 percent, and 40.7 percent, respectively. When the ambient temperature is 26°C and the heat storage device’s starting temperature is 65°C, the exothermic time is reduced by 22.6 percent.
In recent years, energy consumption has continuously been increasing, and the energy consumption proportion in buildings has risen yearly. In order to promote the carbon-neutral goal of carbon peaking, the building sector realizes green and low-carbon transformation. This paper proposes a new type of solar flat plate collector with an additional transparent cover made by the ETFE film, which is tested for thermal performance under different environmental and operational parameters. The Ansys Fluent software was used to build a three-dimensional steady-state model of the collector, which can simulate the collector components’ temperature and the mass outlet temperature under the test conditions. The collector’s instantaneous heat collection efficiency curve fitted by comparing and analyzing the theoretical, experimental, and simulated data. The instantaneous efficiency intercept was 0.72, and the heat loss coefficient was 3.94 W/(m2·K). The results show that the collector efficiency of the ETFE film structure collector is 18.6% higher, and the heat loss coefficient is 27.3% lower than that of an ordinary collector under standard mass flow conditions.
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