Heat transfer characteristics of supercritical CO₂ in a helical coil gas cooler on the change of coil diameter

다국어 초록 (Multilingual Abstract)

The heat transfer characteristics of supercritical CO₂ during gas cooling process are investigated experimentally. The test section is a helically coiled tube with I.D. of 4.55, O.D. of 6.35 and length of 10000 [㎜]. The helical coil diameter is 41.35 and 26.75 [㎜], respectively. The apparatus consist of a receiver, a variable-speed pump, a mass flow meter, a pre-heater, a gas cooler (test section) and an isothermal tank. The range of the refrigerant mass fluxes is from 200 to 800 [㎏/㎡s] and the pressure in the gas cooler varies from 7.5 to 10.0 [㎫]. The main experimental results are summarized as follows; as the gas cooling pressure decreases gradually, the heat transfer coefficient increases greatly. The mass flux has a positive effect on heat transfer like constant property condition. The heat transfer coefficient at coil diameter 26.75 [㎜] is larger than that of coil diameter 41.35 [㎜]. The data is compared with the existing correlations, which generally under-predict the measured data. However the experimental data show a relatively good agreement with correlations by Pitla et al. except for pseudo critical temperature.