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INFECTION CONTROL Hideki Tanaka – Chubu University


Evaporative humidified air for hospital HVAC systems


This article discusses a study undertaken to acquire the proof needed to choose a humidifier in an air-conditioning system design within a hospital.


In recent years, evaporative humidifiers have become the standard for general air conditioning systems in Japanese office buildings. However, steam humidifiers are usually adopted as a humidification method for air conditioning systems in hospitals due to the sterilising properties of steam. Many guidelines also recommend the use of steam humidifiers in hospitals because the air cleanliness of evaporator humidifiers has not been evaluated.


This paper looks at the results of


comparative experiments – based on continuous operation over three months – to access humidified air cleanliness of an air conditioning system using steam or evaporative humidifiers.


Method of comparative experiments A fresh air processing air conditioner was chosen for an experimental air handling unit (AHU) in this experiment (Fig. 1 and 2). Outdoor air is controlled to a specific temperature by a heating process with a hot- water coil, and humidity is controlled by a humidification process. The humidification chamber was divided into four units with four different types of humidifiers in each unit. Two comparative experiments were conducted – a comparison between


Hideki Tanaka


Hideki Tanaka is Associate Professor at the Department of Architecture, College of Engineering, Chubu University in Japan. He is a doctor of engineering, expert of IEA/ECES. His key areas of research include energy conservation and indoor environmental contamination derived from HVAC systems in hospitals; efficient use of energy for houses, buildings and district, solar and natural energy utilisation on energy supply system.


IFHE DIGEST 2014


Air source Heat pump


Figure 1: Schematic of the experimental system.


‘Many guidelines also recommend the use of steam humidifiers in hospitals because the air cleanliness of evaporator humidifiers has not been evaluated.’


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Hygrothermal regulator (humidity control)


Water supply


Humidity Temperature


Hygrothermal sensor


Water supply


Switch signal temperature flow rate


Evaporative humidifier


Drain tap Measured value input Data logger measuring at an interval of 5 seconds


Airflow rate control damper CAV control


Blower EA


Airflow rate 3,200 m3


Thermocouple Nonwoven filter QA Humidifier


Temperature regulator (temperature control)


Temperature


Temperature Humidity


Heating coil


Airflow rate 3,200 m3


/h /h Water Solenoid valve


Water flow regulator


Electromagnetic flowmeter


Water


Steam humidifier


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