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손창효(Chang-Hyo Son),이동건(Dong-Gun Lee),노건상(Gun-Sang Roh),박기원(Gi Won Park),오후규(Hoo-Kyu Oh) 한국마린엔지니어링학회 2003 한국마린엔지니어링학회 학술대회 논문집 Vol.2003 No.-
The heat transfer coefficient and pressure drop of CO₂(R-744) during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop consist of a receiver, a variable-speed pump, a mass flowmeter, an evaporator, and a gas cooled test section). The main components of the water loop consist of a variable-speed pump, an isothermal tank, and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal stainless steel tube of 9.53 mm outer diameter and 7.75 mm inner diameter. The length of test section is 6 m. The refrigerant mass fluxes were 200 -300kg/(m2·s) and the inlet pressure of the gas cooler varied from 7.5 MPa to 8.5 MPa.<br/> The main results were summarized as follows: Pressure drop of CO2 increases with increasing gas cooler pressure. The friction factors of CO2 in a horizontal tube are showed relatively good agreement with correlation predicted by Blasius. The heat transfer coefficient of CO₂ in transcritical region increases with decreasing gas cooler pressure and decreasing mass flux of CO2. Most of correlations proposed in a transcritical region showed significant deviations with experimental data except for those predicted by Gnielinski.<br/>