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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. [ABSTRACT FROM AUTHOR]

The impact of air supply control strategies (louvers movement) on indoor thermal environment were evaluated in this study. The temperature uniformity was evaluated by: (i) the air distribution performance index (ADPI) to determine the air diffusion performance in heating mode; (ii) the air draught rate (DR%) on the face to determine the local discomfort due to cold draught; (iii) the mathematically determined vertical temperature stratification in a room with Beta distributions. A comparison of the conventional type with three different oscillating type airflows (louvers swing angle ±20°, ±40° and ±60°) were experimentally analysed to determine appropriate air supply control strategies. The results indicated that Beta distributions could capture the overall trend of the oscillating airflow, to establish the acceptable thermal uniformity and higher thermal effectiveness. The oscillating airflow as generated by the side-to-side swing type delivery louvers mounted inside a cassette split type air conditioner could shorten heating time by 20% to attain room temperature from 9°C. The data reveal that oscillating airflow can provide a better thermal sensation to feeling warm in the heating mode at both ankle and neck level. The ADPI is approximately 85% in the occupied zone. The actual draught rates on the face ranged 0–35%. [ABSTRACT FROM AUTHOR]

Heat shock is generated from zonal temperature differences. The pre-heating control through an air conditioning system can provide a good thermal environment, and reduce the risk of suffering heat shock in a house and with low energy consumption. In this study, a room air-conditioner (RAC) and air recirculating fan system (ARF) connected to the temperature zone of living room and washing room are applied in a detached house. The design aims to reduce the overconsumption of system energy and fulfil the healthy demand. With low air supply velocity (0.5 m/s) of ARF, the floor supply case can produce a saving of 33.9% energy for RAC to reach the target temperature 20°C in wash room (0.8 m height) in comparison to the ceiling supply case. However, return opening located on the floor was closer to RAC compared to ceiling case, hence, place of return opening should be accounted for energy reduction rate relatively. [ABSTRACT FROM AUTHOR]

As ventilation is one of the critical heat loads in an office space, the ventilation rate might be optimized to develop sustainable, low-energy buildings and a healthy indoor environment. To create comprehensive and optimized indoor environmental designs, a building energy simulation (BES)-computational fluid dynamics (CFD)-integrated simulation is used to provide accurate and informative prediction of the thermal and air-quality performance in buildings, especially in the design stage. With the aim of developing an optimization procedure for the ventilation rate, this paper presents simulations that integrates BES and CFD with CO2 demand-controlled ventilation (DCV) system, and applies them to a typical office space in Japan to optimize the ventilation rate through an energy recovery ventilator (ERV). The transient system control strategy is applied to two different airflow conditions in an office: a traditional ceiling supply system and an under-floor air distribution system. Compared with the fixed outdoor air intake rate, which is referred to as constant air volume ventilation, optimized ventilation systems associated with a CO2 DCV produces energy savings of 11.6% and 24.1%, respectively. The difference in the energy saving effects of the two ventilation systems is caused by the difference in the ventilation efficiency in the occupied zone. The ventilation rate and ventilation efficiency have a significant impact on the energy penalty of an ERV. Therefore, optimizing the ventilation rate according to a CO2 DCV system with an appropriate airflow pattern could contribute to both creating and maintaining a healthy, comfortable environment, in addition to saving energy. [ABSTRACT FROM AUTHOR]

Highlights: [•] CO2 demand controlled optimized ventilation was designed for a typical Japan office. [•] Field measurements were used to quantify energy conservation of ERVs implementation. [•] IEQ, ventilation effectiveness, containment removal, duct heat loss were analyzed. [Copyright &y& Elsevier]