천장형 에어컨 컨트롤러 주변 열환경이 난방 운전 성능에 미치는 영향 평가를 위한 CFD 해석

Abstract

As the demand of air conditioning for heating in winter season and the concern about the building energy consumption increases, many experimental and analytical investigations of the heating performance and operational characteristic of ceiling-type air conditioner have been carried out to increase the efficiency of the system. In earlier studies, the primary concerns were the operating algorithm, mechanical efficiency and physical factors like discharge angle and flow rate of indoor unit. There is no doubt that these efforts definitely have contributed to improve the performance of the systems. However, people's dissatisfaction on indoor thermal environment still exists because of the poor performance of air conditioner due to the abnormal control of the system. The abnormal control may occur by the influence of the thermal environment near the controller. The cold wall on which the controller is installed, for example, can affect the control temperature thus the desired comfort environment may not be achieved. This study investigated two major factors that are closely related with the control temperature of ceiling-type air conditioner. The first is the air passage through the slit of controller that is located near the temperature sensor. The other is thermal inertia of the controller-mounted wall whose temperature drops down severely over the night. To investigate the effect of these two factors on the heating performance, transient CFD simulations using ANSYS CFX v.19 have been carried out for a small office room with ceiling-type air conditioner and wall-mounted controller. In these simulations, outdoor temperature was 0℃, the initial indoor temperature was varied between 0℃ and 10℃. The set temperature for heating mode was 20℃. The simulation results showed that the thermal environment near the controller strongly affects the indoor air current, indoor thermal environment, and the behavior of control temperature. Furthermore, its airflow field and the temperature distribution, and the relationship between the two factors and the control temperature were discussed. All the simulation results have been analyzed to get better understanding of room air conditioning and the role of control temperature.