수평관내 CO2의 초임계 영역내 열전달에 관한 연구
The heat transfer characteristics of supercritical CO2 in a horizontal tube
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Abstract
The cooling heat transfer coefficient of CO2(R-744) in a horizontal tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and gas cooler(test section). The test section consists of a smooth, horizontal stainless steel tube of 7.75 mm inner diameter. The experiments were conducted at mass flux of 200 to 400 kg/m2s and the inlet cooling pressure of 7.5 MPa to 10.0 MPa. The variation of heat transfer coefficient tends to decrease as cooling pressure of CO2 increases. The heat transfer coefficient with respect to mass flux increases as mass flux increases. The pressure drop of CO2 in the gas cooler shows a relatively good agreement with that predicted by Blasius's correlation. The local heat transfer coefficient of CO2 agrees well with the correlation by Bringer-Smith.
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