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Study on Heat Transfer Characteristics of Internal Heat Exchanger for $CO_2$ Heat Pump under Heating Operating Condition  

Kim, Dae-Hoon (Department of Mechanical Engineering, Hanyang University)
Lee, Sang-Jae (Department of Mechanical Engineering, Hanyang University)
Choi, Jun-Young (Korea Testing Laboratory)
Lee, Jae-Heon (Department of Mechanical Engineering, Hanyang University)
Kwon, Young-Chul (Department of Mechanical Engineering, Sunmoon University)
Publication Information
Journal of Energy Engineering / v.17, no.2, 2008 , pp. 116-123 More about this Journal
Abstract
In order to study the heat transfer, effectiveness and pressure drop of an internal heat exchanger (IHX) for $CO_2$, heat pump under heating condition, the experiment and numerical analysis were performed. Four kinds of IHXs were used. The section-by-section method and Hardy-Cross method were used for the numerical analysis. The effects of IHX on the flow rate of refrigerant, the IHX length, the operating condition of a gas-cooler and an evaporator and the type of IHXs were investigated. With increasing the flow rate, the heat transfer rate increased about 25%. The heat transfer of the micro-channel tube was larger about 100% than that of the coaxial tube. With increasing the IHX length, the heat transfer rate decreased. The low-side pressure drop was larger compared with that of the high-side. And the pressure drop of the microchannel tube was larger about 100% than that of the coaxial tube. With increasing the high-side temperature and decreasing the low-side temperature, the heat transfer rate increased about 3%. From this study, we can see that new correlation on $CO_2$ heat transfer characteristics and tube type is necessary.
Keywords
$CO_2$; Heat pump; Internal heat exchanger (IHX); Heating;
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