Evaluation of heat transfer coefficients in various airconditioning modes by using thermal manikin

Today, radiant floor heating systems are generally used for heating indoor environments of residential buildings. Radiant heating is physically comfortable and energy use largely differs compared to convective heating. It is believed that one reason for that is if there is an air flow, there is a difference in surface heat transfer of the human body. The heat transfer coefficient of the human body is an indispensable parameter to evaluate the indoor thermal environment, thermal comfort and heat loads in air-conditioned and ventilated buildings. Measuring the heat transfer coefficient of the human body under various air-conditioning conditions is rather difficult due to the multitude of factors, such as temporal changes in air temperature, airflow, cold draft, ventilation condition, storage effect, heat due to radiation, etc. Considering the above, in order to measure surface heat transfer precisely, an expensive thermal manikin or highly controlled environment laboratory is necessary. For this, recent developed computational fluid dynamics (CFD) are suitable. With the objectivity of prediction results and the degree of freedom of condition settings, they are able to become a beneficial investigative method. The purpose of this paper is to verify the heat transfer coefficient of the human body and operative temperature in various air-conditioning environments, such as radiant floor heating and convective air heating using numerical simulation for evaluation of energy saving possibility in residential buildings. First, we measure the heat transfer coefficient of the human body using a thermal manikin in an experimental chamber under natural convection conditions. Then, to confirm CFD calculation accuracy, heat transfer coefficient of the thermal manikin with a temperature difference is verified using an experimental chamber model. Second, we measure the heat transfer coefficient of the thermal manikin surface with CFD calculation to verify its characteristics under forced convection conditions. Finally, we evaluate the operative temperature in an air-conditioned room using computer fluid dynamics to propose the correlation relation in various air-conditioning modes for residential buildings. The measured results showed the heat transfer coefficient of the thermal manikin increased from temperature difference increase and air velocity. Furthermore, the results showed the radiant floor heating environment is more energy consumption efficient than a convective air heating environment.