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Chaobin Dang / Assistant Professor / Division of Environmental Studies
Department of Human and Engineered Environmental Studies / / Thermal Engineering, Refrigeration and Air Conditioning
http://www.hee.k.u-tokyo.ac.jp/dangcb

Career Summary
Assistant, Institute of Environmental Studies, University of Tokyo, 2005?present
Researcher, National Institute of Industrial Science and Technology, 2003?2005

Educational Activities

Research Activities
(1) Study on transcritical CO2 heat pump system
Carbon dioxide is promising as a substitute refrigerant for use in hot water heaters and automobile air conditioners due to the increasing attention to environmental protection. However, due to its low critical temperature, a heat pump using carbon dioxide as a refrigerant is operated transcritically, where heat absorption occurs at a subcritical pressure while heat rejection occurs at a supercritical pressure. Therefore, studies on the heat transfer characteristics of supercritical and subcritical fluids with high reduced pressure are of great importance for the design of carbon dioxide heat pumps. In addition, the ejector cycle is studied to verify its applicability to such heat pump systems. (Refs.1, 2)

 Heat transfer characteristics of supercritical CO2
Heat transfer characteristics of supercritical CO2


(2) Study on heat transfer characteristics of supercritical fluid with entrained lubricating oil
The transitions of the flow pattern of supercritical CO2 with entrained PAG oil was found to drastically affect heat transfer performance. Change of thermophysical properties of supercritical CO2 with temperature and pressure, as well as the change of CO2 solubility in PAG oil, makes the prediction of the flow pattern and heat transfer performance a challenging task. To clarify the heat transfer characteristics of supercritical CO2 with entrained lubricating oil, experimental measurements, visual observation, and numerical studies are being carried out. (Refs. 3, 4)

 Two phase flow pattern of supercritical CO2 with lubricating oil
Two phase flow pattern of supercritical CO2 with lubricating oil


(3) Development of novel optical-fiber type temperature and humidity sensors
POF-type sensors for detecting humidity and temperature change, which are based on the swelling phenomena in the cladding polymer layer of POF sensors, have been proposed, and their effectiveness has been experimentally studied. Currently, theoretical studies on optimal structure and material selection are being carried out.

 Schematic diagram of temperature/humidity sensor
Schematic diagram of temperature/humidity sensor

Literature
1) Dang, C., Hihara, E., In-tube cooling heat transfer of supercritical carbon dioxide, part 1: experimental measurement, Int. J. Refrigeration, Vol. 27, pp. 736?747, 2004.
2) Dang, C., Hihara, E., In-tube cooling heat transfer of supercritical carbon dioxide, part 2: comparison of turbulence models in numerical calculation, Int. J. Refrigeration, Vol. 27, pp. 748?760, 2004.
3) Dang, C., Iino, K., Fukuoka, K., Hihara, E., Effect of lubricating oil on cooling heat transfer of supercritical carbon dioxide, Int. J. Refrigeration, Vol. 30, No. 4, pp. 724?731, 2007.
4) Dang, C., Iino, K., Hihara, E., Study on two-phase flow pattern of supercritical carbon dioxide with entrained PAG-type lubricating oil in a gas cooler, Int. J. Refrigeration, in press.
Other Activities
The Japan Society of Mechanical Engineers (JSME)
Japan Society of Refrigerating and Air Conditioning Engineers (JSRAE)
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Future Plan
1. Numerical simulation of two-phase transition processes, including evaporating and gas-cooling with entrained lubricating oil
2. Experimental study on the interaction of flow boiling and nucleate boiling
3. Micro-scale heat exchangers

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