A Study on Year-round Cooling and Heating System by a Gravity Air Cooling and Heating Unit Hung at Peripheral Window Side Ceiling : Part 1-Radiant Effect in Heating Cycle

This study relates to the cooling and heating effect by a natural convection type cooling/heating unit installed in the ceiling plane right above building perimeter. The test was conducted at a mock-up room with facilities to control its exterior (outdoor) temperature condition in -20℃〜+35℃ variable range. Under this variable outdoor air temperature, measurements were made on the convection and heat radiation in the test room. Extensive reference was then made to the effect given on human body. This report particularly deals with the radiant effect in heating cycle. The test result obviously shows reduction of cold draught stream along window face and cold temperature radiation through window glass. Assuming a total surface of a human body of 1.8 square meters, the net radiant heat upon the human body will come in 50kcal/h and 30kcal/h when heating water temperatures are 75℃ and 55℃, respectively. The test results conclude that a sufficient amount of radiant effect can be expected even at such low temperatures. When this radiant-heat unit performs, the mean radiant temperature MRT in the test room rises 2.4〜3.2deg when water temperature is 75℃, and 1.5〜2.1deg when water temperature is 55℃. As the MRT rises, the effective temperature also increases; approximately in the order of 1.5deg and 1deg when water temperatures supplied are 75℃ and 55℃, respectively. Approximately 50% of the unit's heating capacity is transmitted to the room by radiation of ceiling panel, and the remaining 50% heat by convection plus ancillary radiation effect of warm air layer which moves along ceiling plane very slowly. As for temperature distribution in the room, the following results were obtained; at the point 0.5 meter away from the window face, floor temperature gets low by a direct effect of temperature radiation of cold window glass and down ward cold draught stream along window face, yet at the point 1 meter away from the window face, all temperatures measured at floor level, 0.5 meter and 1.5 meters levels above floor, fall under ±0.5deg fluctuation range of the mean room temperature. At any points 2 meters or more away from the window face, the floor temperatures get even higher than the temperatures measured at the plane 0.5 meter above floor,where by the test results set forth pattern of temperature distribution in the room the getting assumingly similar to that obtainable by the ceiling radiation panel heat systems. The study here to will develop here after to the extensive comparisons with the experimental data on the room environments by several conventional heating systems.