Zhiqiang Wang

In buildings with the solar heat collection/insulation energy-saving window (SHC/IESW), when the insulation device is placed at night in winter, a double-wall structure façade (DSF) is formed between the glass and the insulation curtain, and the existence of air inlet and outlet leads to cold air penetration. In this paper, the Nusselt number (Nu) correlation and convective heat transfer coefficient (CHTC) of the cavity in SHC/IESW were calculated through an experiment combined with a theoretical analysis. Then, numerical simulation was performed on the fluid dynamics and thermal characteristics caused by air convection in an asymmetrically heated cavity under uniform heat flow conditions, to optimize the SHC/IESW structure and analyze its heat transfer mechanism to solve the problem of convection heat transfer between plates under cold air infiltration. Using the calculation formulas obtained from the experiment, the heat transfer coefficient of SHC/IESW is 1.71 W·m⁻²·K⁻¹. The numerical simulation results showed that with the increase of air layer thickness, the outlet temperature, the average air velocity of the cavity, and the surface temperature of thermal insulation curtain all decrease; with the increase of inlet width, the outlet temperature and the surface temperature of thermal insulation curtain decreases significantly, while the average air velocity of cavity increases. It can help to weaken the convective heat transfer in the cavity and thus, reduce the total heat transfer coefficient to 1.28 W·m⁻²·K⁻¹ when the air layer thickness is 12 mm and the inlet width is 1 mm.

The thermal insulation performance of a building's windows can have an important role in its energy-saving capability. In this work, we proposed a novel, energy-saving insulated window (ESIW) and investigated its winter insulation ability by conducting temperature, comfort, energy and entropy analyses of a house outfitted with the ESIW system. The natural indoor temperature of houses with ESIW(A) structure windows was generally higher than that with some single-layer functional glasses. Furthermore, it costs less, and therefore demonstrated the highest cost benefit performance. Then, four different ESIW structures (A to D) were designed and tested. The inner ESIW(D) system with 3-cm insulator thickness and an 8-cm air layer had 4.3% superior performance in energy saving relative to the outer ESIW(A) system, which was comprised of 2-cm insulator thickness and an 8-cm air layer. The lower the insulation level, the greater the energy loss with a decrease in the predicted mean vote of occupants. While the predicted percentage dissatisfied of occupants, entropy of energy loss ( S_g), and entropy difference of the whole insulation system ( ΔS_iso) would be increased. Finally, the period from 22:00 to 8:00 appears to be the optimal time interval for the use of a roller curtain.

Window energy consumption has become a key factor in designing buildings with optimal energy efficiency. To that end, herein, the use of an energy-saving insulated window (ESIW) is proposed, particularly for winter heat conservation. DeST software was used to evaluate the energy consumption properties of a house with an ESIW-structure window, as well as that of six other window structures currently on the market. The results were subsequently compared. Furthermore, a series of numerical simulations were carried out using Airpak software to investigate the insulation performance of four ESIW models (A, B, C, and D) under different influencing factors. Finally, the response surface method (RSM) was used to obtain the optimal ESIW structure installation conditions and the weight of each factor. The data shows that houses with ESIW-structure windows exhibit a more suitable indoor natural temperature; less heating load, cooling load, and cumulative annual load; and a more feasible price–load ratio than other energy-saving windows. Furthermore, the average temperature gradually decreased in response to decreasing the electric heater power and energy-saving standard, and increasing the heat transfer coefficient (HTC) and window-to-wall ratio (WWR). Thus, as the energy-saving standard (ESS) increases, the importance of the WWR increases in parallel. This study puts forward an HTC prediction formula that is applicable to different conditions. The optimal thermal efficiency conditions consisted of HTC = 1.07 W/m² × K, WWR = 0.26, and an ESS of 75%. This study demonstrates that the ESIW system has optimal energy-saving properties and broad adaptability and operability, which can be applied in building insulation as a key insulation component.