عنوان مقاله [English]
In recent years, there has been growing interest in the use of floor heating systems because of their onsiderable advantages, such as being energy-saving and a comfortable thermal environment. In these systems, a significant part of heat energy is transmitted in radiant mode. Therefore, the human body thermal conditions can be considerably influenced by changing the body posture and the view factor between the heated floor and the human body. On the other hand, in most eastern countries, people traditionally tend to directly sit or sleep on the floor. Moreover, floor heating and other air-conditioning systems are commonly designed based on the thermal neutrality of sedentary occupants. This can impose some limitations on the use of floor heating systems for people with such eastern lifestyles. In this paper, investigations are made to discover whether floor heating systems are convenient for persons who tend to sleep traditionally on the floor, and how the thermal and physiological responses of the human body are affected under the mentioned conditions. In this study, a new model has been developed to predict the sensation of sleeping occupants on the floor heating systems. This model is based on the well-known Fangers thermal comfort model. Fanger developed his model in 1970, using an energy balance equation for the human body. But, it should be noted that Fangers model has not exclusively been developed for thermal sleeping conditions. Nevertheless, the bodys thermal condition during sleep is distinctly different from that under sedentary conditions, because of a decrease in the metabolic rate, an increase in the portion of conductive heat transfer and, also, an increase in thermal resistance between the body and the environment. Therefore, in the present study, a new thermal comfort model has been developed by considering the thermal sleeping conditions of the human body. Using this thermal comfort model, the thermal sensation of occupants under traditional sleeping conditions has been compared with that of occupants of conventional beds. Results indicate that the thermal sensation of sleeping occupants is significantly dependent upon blanket insulation. Additionally, the calculations show that the thermal comfort conditions of sleeping occupants on floor heating systems are only satisfied in the narrow range of blanket insulation (0.2 clo - 1.75 clo), whereas the proper range of blanket insulation for persons sleeping on conventional beds is 0.65 clo - 3.7 clo.