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R22의 대체냉매를 사용한 공기조화기의 성능 시뮬레이션
장세동,노승탁,Chang, S.D.,Ro, S.T. 대한설비공학회 1994 설비공학 논문집 Vol.6 No.1
Cycle simulation of the air-conditioner was carried out using a number of candidate alternatives to R22;R32/R125/R134a(30/10/60, by mass percent), R32/R125/R134a(10/70/20), R32/R134a(25/75), R32/R134a(30/70), R32/R125(60/40), R290(propane) and R134a. In this study, we considered only the basic parts of the air-conditioner such as the compressor, the evaporator, the condenser and the capillary tube, for the purpose of analysis. The performance characteristics of alternatives considered here were examined by comparing with the case using R22 at the constant volumetric flow rate condition. The results of our analysis revealed that the use of refrigerant mixtures, R32/R134a(30/70) and R32/R125/R134a(30/10/60), was appropriate for the alternatives to R22 in view of the cooling capacity and the COP. For the case of using R134a and R290, the COP was observed to increase under the same volumetric flow rate condition, but the cooling capacity was substantially decreased. Therefore the use of R134a and R290 should be accompanied with increasing considerably the size of compressor in order to maintain the same cooling capacity of R22.
정사각형 단면을 갖는 용기에서 단면의 크기 변화가 융해 열전달에 미치는 영향
한진호,노승탁,Han, Jin Ho,Ro, Sung Tack 대한설비공학회 1990 설비공학 논문집 Vol.2 No.3
A rectangular test section is devised by assuming two dimensional melting of a solid phase change material heated from two sides which are maintained at constant temperature and allowing a free expansion due to density difference between solid and liquid. The timewise melting shape is recorded photographically by the shadow graph method for several experimental conditions. The analysis shows that the melting process consists of four regimes. At first, the pure conduction heat transfer is dominant, and as time goes by natural convection grows and plays a role greatly. Experiments are carried out varying not only the wall temperature but height of the wall. Each effect of them on the melting process is obtained in the form of combination of dimensionless parameters, $Ste^{0.8}\;FoRa^{0.2}$. An algebraic correlation is suggested, which predicts the melted fraction well.
최정운,노승탁,Choi, Kyung-Jin,Ro, Sung-Tack 대한설비공학회 1978 설비저널 Vol.7 No.1
An experiment has been performed of find a temperature distribution of the circulating fluid in a packed bed thermal storage system when the inlet fluid temperature is constant. The thermal storage system is a specific-heat type in which the circulating fluid, hot air, exchanges heat directly with the heat storage materials, glass balls, in a heat storage bin. An empirical equation which includes two dimensionless variables $t^*\;and\;T_f^*$, is obtained. Also, heat storage efficiency and heat storage capacity are calculated from this equation, The heat transfer coefficient calculated by the suggested equation was compared with the value determined by the existing empirical equation.
태양열에 의한 냉방 및 난방시스템의 성능향상 (III) - 성층화계수의 예측을 위한 1차원 해석모델의 개발 -
유재경,노승탁,이준식,정석호,Yoo, J.K.,Ro, S.T.,Lee, J.S.,Chung, S.H. 대한설비공학회 1989 설비공학 논문집 Vol.1 No.1
A one dimensional analytic model for the prediction of the stratification coefficient of a liquid-based solar heating system is developed. The stratification coefficient, $K_s$, is defined as the ratio of the actual useful energy gain to the energy gain that would be achieved if there were no thermal stratification in the storage tank. Previous studies incorporated only collector-side effects, but in this study both the collector and load-side effects are included for the overall performance evaluation.