This paper discusses the results of comparative experiments for humidification performance and humidified air cleanliness of an air conditioning system using steam or evaporative humidifiers. Three types of evaporative humidifiers are compared with a steam humidifier in terms of their characteristics. To evaluate the humidified air cleanliness, the number of microorganisms was counted. As a result, no differences were found in cleanliness of humidified air between the steam humidifier and the evaporative humidifier. Then, three operating conditions were assumed: reference-case (24hours humidification), UV light irradiation, and compulsory drying (2-4hour/day). Difference in humidified supply air cleanliness of the humidifiers was not observed from the microorganism count. Moreover their humidified supply air cleanliness did not decline over two years of continuous operation.

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This study aims to propose an optimal planning method of maintenance schedule for air-conditioning system to determine maintenance frequencies, month of maintenance and the equipment to be recovered from deterioration by the simulation. The proposed method determines a maintenance schedule so that energy consumption and operation costs would be at a minimum value during a lifetime of system. It is possible to determine the maintenance schedule considering the actual condition of system by inputting the data of daily changing conditions of systems and boundary conditions into the simulation. In this paper, the energy and cost saving effects of introducing the optimal maintenance schedule are evaluated by comparing the optimal maintenance with periodic maintenance and condition-based maintenance. As results, in the case where the objective function was energy consumption, the reduction rate of the annual average energy consumption increased due to deterioration was approximately 5%-7% higher than in the other cases. In the case where the objective function was operation cost, the annual average operation cost increased due to deterioration decreased by 61.5%.

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An effective means for greenhouse gas reduction is to use sewage heat for air conditioning, which is a type of renewable energy. This study conducts energy evaluation of the utilization of treated sewage, heretofore discarded from a sewage treatment plant adjacent to a redeveloping area, as a heat source of air conditioning for that redeveloping area by simulation. It was found that in terms of primary energy, systems using heat pumps reduced energy consumption by 12.2% per year (6.4% cooling, 36.1% heating) and greenhouse gas emissions by 16.8%. Thus, the effectiveness of sewage as a heat source was evaluated.

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Central-exhaust ventilation systems operate 24 hours, and exhaust formaldehyde gas or volatile organic compounds. For such systems in newly constructed houses, door undercuts are often applied as the exhaust opening of bed rooms. However, in order to exhaust CO_2 and humidity generated by occupants in bed rooms efficiently, installing an opening in the vicinity of the top of the door might be more effective than that in the vicinity of the door undercut. To compare and confirm which of the locations for the opening is more suitable, authors have examined air flow distribution, temperature distribution, and CO_2 concentration distribution of a bed room during a winter night by CFD simulation. It was found that installing the opening in the vicinity of the top of the door is more effective than under cut, and existing ventilation design manuals should introduce the opening in the vicinity of the top of the door.

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