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송길홍,이준강,정동수,김종보 대한설비공학회 1998 설비공학 논문집 Vol.10 No.4
In this study, experiments were carried out to provide nucleate pool boiling heat transfer data for a plain tube and 4 different low fin tubes employing 2 refrigerant mixtures of R410A, R407C, and 12 pure fluids. Low fin tubes were machined on a 19.05mm nominal outside diameter copper block according to the manufacturer's low fin tube specifications. Cartridge heaters were used to generate uniform heat flux on the tubes. For all refrigerants, heat flux varied from 10㎾/$\m^2$ to 80㎾/$\m^2$. It is found that heat transfer coefficients(HTCs) of high vapor pressure refrigerants are usually higher than those of low pressure fluids. On the other hand, the fin effect was more prominent with low pressure refrigerants than with high pressure ones. Optimum fin density as well as the increase in heat transfer coefficient with the increase in fin density were found to be strongly fluid dependent. HTCs of Rl23, a low pressure alternative refrigerant, were similar to those of Rll while HTCs of R134a, an intermediate pressure alternative refrigerant, were roughly 20% higher than those of Rl2. Finally, HTCs of R32, R125, R143a, and R410A were all higher than those of R22 by 30~50%.
김신종,송길홍,정동수 대한설비공학회 2002 설비공학 논문집 Vol.14 No.2
Flow Condensation heat transfer coefficients (HTCs) of Rl2, R22, R32, Rl23, Rl25, R134a, R142b were measured experimentally on a horizontal plain tube. The experi- mental apparatus was composed of three main parts; a refrigerant loop, a water loop and a water-glycol loop. The test section in a refrigerant loop was made of a copper tube of 8.8 mm inner diameter and 1000 mm length respectively. The refrigerant was cooled by passing cold water through an annulus surrounding the test section. All tests were performed at a filed refrigerant saturation temperature of 4$0^{\circ}C$ with mass fluxes of 100, 200, 300 kg/$m^2$s. The experimental result showed that flow condensation HTCs increase as the quality, mass flux, and latent heat of condensation increase. At the same mass flux, the HTCs of R32 and R142b were higher than those of R22 by 35~45% and 7~14% respectively while HTCs of R134a and Rl23 were similar to those of R22. On the other hand, HTCs of Rl25 and Rl2 were lower than those of R22 by 28 ~30% and 15 ~25% respectively Finally, a new correlation for flow condensation HTCs was developed by modifying Dobson and Chato's correlation with the latent heat of condensation considered. The correlaton showed an average deviation of 13.1% for all pure fluids data indicating an excellent agreement.
고영환,김종곤,송길홍,정동수,김영일 대한설비공학회 2000 설비공학 논문집 Vol.12 No.10
Pool boiling heat transfer coefficients (HTCs) of HCFC123, CFC11, HCFC142b, HFC134a, CFC12, HFC22, HFC125 and HFC32 on a horizontal smooth tube have been measured. The experimental apparatus is specially designed to simulate the real heat transfer tube with the use of the secondary fluid of water as a heat source rather than a conventional electric heat source. Data were taken in the order of decreasing heat flux starting at $80 ㎾/m^2\; and \;ending\; at\; 5㎾/m^2\;in\; the\; poo\;l temperature\; at\; 7^{\circ}C$, Test results showed that HTCs of HFC125, and HFC32 are 50~67% higher than those of HCFC22. It is also found that some of the popular pool boiling heat transfer correlations in the literature are not good to predict the HTCs of newly developed alternative refrigerants. A new correlation was developed by a regression analysis which is based upon the consistent data obtained in this study and it showed an excellent agreement with all experimental data having an absolute mean deviation of less than 10%.
이준강,고영환,정동수,송길홍,김종보,Lee, Jun-Gang,Go, Yeong-Hwan,Jeong, Dong-Su,Song, Gil-Hong,Kim, Jong-Bo 대한기계학회 1998 大韓機械學會論文集B Vol.22 No.7
In this study, nucleate pool boiling heat transfer coefficients of alternative refrigerants on a plain, low fin, and two enhanced tubes were measured and compared against each other. To obtain data at conditions similar to the actual evaporator, a fluid heating method was employed instead of an electric heating method in the experiments. R123, R134a, R22 and R410a were used as working fluids and data were taken at 7 deg.C ar heat fluxes of 20 ~ 100 kW/m$\^$2/. Comparison of the plain tube data against some correlations showed that the simplest correlation of Cooper based on reduced pressure predicted the data for all fluids tested with a 10% deviation. For all refrigerants, enhanced tubes composed of subsurface and subtunnels, especially Thermoexcel-E tube, showed the highest heat transfer coefficients among the tubes tested with one exception that the low fin tube's performance was better than those of enhanced tubes for high vapor pressure fluid such as R410a at high heat flux. Finally, a low fin and enhanced tubes showed higher heat transfer enhancement for low vapor pressure of R123 than for high vapor pressure fluisd. For R123, the enhancement factors for Turbo-B and Thermoexcel-E tubes were 2.8 ~ 4.8 and 4.6 ~ 8.1 respectively.