The Evaluation of Air Blowing Method of Variable-Air-Conditioning-System using Coanda Effect by Computational Fluid Dynamics

Abstract

Government of Japan aims to achieve net zero energy buildings on average regarding newly constructed buildings by 2030. Therefore, we studied the ductless air conditioning system using Coanda effect which is one of the technologies to realize net zero energy buildings. By reducing duct space on the ceiling, it can reduce fan power and save resources. However, when the amount of blowing air volume is small, there is the possibility the conditioned air is not diffuse into the room. Also, when the blowing air volume is large, the draft airflow possibly occurs. Hence, the distribution of the airflow in the room was confirmed by computational fluid dynamics. 15 cases were analysed at the thermal load of 30%, 50% and 100%. The default case was set as the blowing temperature difference of 10 Kelvin and the blowing wind speed of 3.0 meters per second. Then, Air Diffusion Performance Index was calculated from Effective Draft Temperature. As a result, the thermal comfort was generally good when the thermal load was 100%. However, there were some cases that the thermal comfort was low by the draft and hot spaces. It was comfortable in most cases when the thermal load was 30% and 50%.