A TOPSIS optimization for the indoor thermal environment through oscillating airflow generated from a cassette split type air conditioner

Abstract

This study evaluates the feasibility of a control method, ‘the Technique for Order of Preference by Similarity to Ideal Solution’ (TOPSIS) for the optimization of the subzone thermal environment by optimizing the oscillating airflow generated from a cassette split type air conditioner. To address the quasi-dynamic thermal comfort problems, various operation swinging angles of the louvre in the supply opening of an air conditioner and swinging periods were investigated by computational fluid dynamics (CFD) simulation. The impact of air supply control strategies (louvres movement) on the indoor thermal environment was evaluated by multi-criteria operation under quasi-dynamic conditions. The operation parameters were shown to have significantly improved the deviation in thermal uniformity by 16.5% and thermal preference by 7.6%. A 40 s swing period and wider swing angles for the operation of the inner louvre would satisfy the thermal uniformity rather than other alternatives. A shorter swing period <20 s is insufficient to allow perfect airflow mixing at the vertical section. For individual target mode such as the room corner, the thermal performance is more sensitive to the swing angle than the swing period; by increasing the swing angle to ±60° to enhance thermal preference, a 24.1% increase in the overall thermal performance would be achieved.