Cooling Load Analysis through Coupled Simulation of Convection, Radiation, and Air-Conditioning Regulation : Part 1-Cooling Load Analysis with the Identical Operative Temperature

Abstract

In this paper, a new method is presented to access heating and cooling loads with a condition of the same thermal condition. The traditional assumption of 'perfect mixing air temperature in the room' can not be applied to analyze the heating and cooling loads of different types of systems for a room. Different types of AC (Air-conditioning) systems induce different thermal conditions such as vertical temperature distributions, radiative fields, etc. These conditions can give effects on the heating and cooling loads. The CFD technique, coupled with a radiative heat transfer simulation and AC regulation, can provide information about more realistic heating and cooling loads. In the simulation, AC outputs (e.g., inflow air temperature, inflow air volume, etc) are changed by a feedback system of AC regulation. These changes are based on the simulations with various boundary conditions to keep operative temperature of a human model at the target temperature. To demonstrate the new method, thermal environment of a semi-closed space, which is opened to an atrium, is analyzed. The heat exchange can be occurred within these two spaces by air circulation and radiation. It is clear that both convective and radiative heat exchanges give an influence on the cooling load of the semi-closed space. To predict the cooling load precisely, the amount of these exchanges have to be estimated with a certain accuracy. In this paper, two types of AC systems are compared; one is radiation panel system and the other is all-air cooling system. With the new method, the required cooling loads for the condition of the same thermal sensation are quantitatively estimated. The effects of air curtain are also studied. In this study, the best energy saving AC system for the same thermal condition is able to be chosen; the radiation panel system with air curtain is decided as the least energy use method to cool the semi-closed space.