Development and verification of simulation model of heat transfer process through window unit with heat-reflecting screens

Window units account for the largest specific heat losses. The use of movable heat-reflecting screens and photovoltaic solar panels is of particular interest among the existing technologies to improve the thermal protection of windows. Despite the large number of scientific papers on this issue, which consider experimental laboratory studies and numerical simulation of heat transfer processes through window units, there is no data on the influence of the edge zones of a double-glazed window, as well as the areas of interface of the window profile and the light opening on the thermal processes that occur in these energy-saving units with screens. Vertical replacing of specific heat fluxes and temperature on the inner surface of the window unit strongly influences the correctness of determining the value of the minimum allowable temperature of the indoor air. Thus, the development and verification of models of the heat transfer process through a window unit with screens is an urgent task in the context of an indoor microclimate creation. Simulation numerical modeling is performed using the finite element method based on the fundamental laws of heat transfer. The authors have used the results of experimental studies of windows with heat-reflecting screens carried out in a certified climatic chamber. The authors have developed a two-dimensional simulation model of heat transfer through a window unit with heat-reflecting screens located in the partition wall of the climate chamber. The distribution of temperatures, air flow velocities, and reduced total thermal resistance along the height of a translucent structures has been studied. The adequacy of the proposed simulation model is confirmed by comparison with the results of the experiment in a certified laboratory, as well as data obtained by other authors and regulatory documentation. The use of heat-reflecting screens in the window unit increases the resistance to heat transfer by 1,6–3,7 times depending on their number. A significant decrease in temperature in the edge zones of the double-glazed window is revealed. The use of the developed simulation model makes it possible to determine the application of heat-reflecting screens in windows for intermittent heating systems including the case of using pre-drying air technology for humid, wet, or normal operation modes of industrial premises.