دانلود رایگان مقاله ویژگی حرارتی در چند ورق از نوع صفحه تابشی سیستم گرمایش

Abstract

The purpose of this study is to examine the thermal characteristics of a multi-sheet-type radiant panel heating system and its effect on the indoor thermal environment. To examine the thermal characteristics using computational fluid dynamic (CFD) simulations, simulation of a radiant panel model that considers actual usage condition combined with convection and radiation is very important. We analyze the indoor thermal environment of a real-scale space, heated by a radiant heating system, using full-scale measurement and CFD simulation. In a multi-sheet-type radiant panel, the convective heat transfer is greater than the radiative heat transfer. The multi-sheet-type radiant panel is actually not a real “radiant panel.” It is named as such by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers because its radiative heat transfer is more than 50%. We also determine the effects of indoor setup location of the radiant panel and panel shape on the heat-discharge characteristics. Compared with a single-sheet-type with the same heat discharge, a multi-sheet type has a larger surface area and area of contact with air. Thus, the convective heat transfer is greater, and the radiative heat transfer is smaller.

5. Conclusions

A multi-sheet radiant panel shows significant potential for high level of convective heat transfer due to the increase in the heat exchange area with air. In this study, the thermal characteristics of multi-sheet radiant panels were evaluated, and a comparison was made between full-scale measurement of an indoor thermal environment employing a radiant panel and analysis using CFD simulation. Further, the changes in the heat-discharge characteristics depending on the radiant panel setup location and shape were ascertained. The following results were obtained: (1) We confirmed that the multi-sheet-type radiant panel has higher convective heat transfer, although the MRT at a height of 1.2 m (14.1 °C) exhibited a value 0.6 °C lower than the air temperature at the same height (14.7 °C). (2) We confirmed through comparison of the CFD simulation and full-scale measurement results that the difference in terms of temperature was approximately 0.6–3.0 °C and that the prediction precision was adequate for practical use. In addition, the heat-discharge characteristics of the multi-sheet-type radiant panel were ascertained, and the results showed that approximately 68.5% of the total heat flux of the multi-sheet panel managed the heat load through convection. (3) Changing the setup location of the radiant panel affects the indoor thermal environment. When the panel faces the insulation wall, it reduces the heat loss in the windows. The radiant panel could be placed in the wall-side positions to achieve increased indoor air temperature under the same heating surface temperature. (4) Compared with a single-sheet-type with the same heat discharge, a multi-sheet-type with a series of thin panels has a larger surface area and area of contact with air; thus, the convective heat transfer is greater and the radiative heat transfer is smaller. We believe that it reduces the air contact area and limits the convective heat transfer. Therefore, the design for a radiant panel must consider investigating its thermal characteristics.