• 수산해양교육연구
• /
• 제28권5호
• /
• pp.1273-1279
• /
• 2016

Flow boiling pressure drop in multi channels was experimently investigated. The multi channel has a width and depth of 0.45 and 0.2mm respectively, and comprises 15 parallel channels. The measured total pressure drop is expressed by the sum of the frictional pressure drop and acceleration pressure drop. In order to predict the total pressure drop, it is required to obtain the correct frictional pressure drop. The existing correlations to predict the frictional pressure were compared with measured frictional pressure drop. The new correlation was developed in the form of the Chisholm correlation. It was related to Chisholm Constant B as a function of Martinelli parameter. The new correlation predicted the experimental data within a mean absolute error of 5.5%.

• 한국유체기계학회 논문집
• /
• 제5권1호
• /
• pp.20-26
• /
• 2002

This study reports the analysis of the pressure drop characteristics for the air-particle flow in powder transport piping system. The pressure drop characteristics of air-particle flow in piping system is not well understood due to the complexity of particles motion mechanism. Particles or powders suspended in air flow cause the increase of the pressure drop and affect directly the transportation efficiency. In this study, the pressure drop in powder transport piping system with straight and curved pipes is analyzed for the interactions of air flow and particle motion. The total pressure drop increases with increasing of the pipe length, the mixture ratio, and the friction factor of particles due to the increasing friction loss by air and particles in a coal piping system. For the coal powders of $74{\mu}m$ size and powder-to-air mass mixture ratio of 0.667, the total pressure drop by the consideration of powders and air flow is $30\%$ higher than that of air flow only.

• 수산해양교육연구
• /
• 제14권2호
• /
• pp.177-190
• /
• 2002

An experimental study was carried out to make clear heat transfer characteristics in flow boiling of binary mixtures of refrigerants R134a and R123 in a uniformly heated horizontal tube. Experiments were run at a pressure of 0.6 MPa both for pure fluids and mixtures in the ranges of heat flux $10{\sim}50{kW/m}^2$, vapor quality 0~100% and mass flux 150-600 $kg/m^2s$. Heat transfer coefficients of mixtures were reduced compared to the interpolated values between pure fluids both in the low quality region where the nucleate boiling is dominant and in the high quality region where the convective evaporation is dominant. Total pressure drop during two-phase flow boiling in a horizontal tube consists of the sum of two components, that is, the frictional pressure drop and pressure drop due to acceleration. The frictional pressure drop is the most difficult component to predict, and makes the most important contribution to the total pressure drop. On the other hand, the acceleration pressure drop resulting from the variation of the momentum flux caused by phase change is generally small as compared to the frictional pressure drop. There is no significant difference in measured pressure drop between mixtures and pure fluids. The correlation of Martinelli and Nelson predicted most of the present data both for pure and mixed refrigerants within 30%.

• 한국산업융합학회 논문집
• /
• 제11권4호
• /
• pp.157-163
• /
• 2008

The present study investigated the pressure drop and the total frost mass of the louvered fin type heat exchanger, which is widely used at the air-conditioning system. The pressure drop due to the frosting phenomenon and the total frost mass were investigated by changing the wet bulb temperature condition of the inlet air. Hence the brain of 55wt% was used as a cooling solution instead of a common refrigerant. The temperature difference between the brine and the tube outside wall at the outlet of heat exchanger was $10^{\circ}C$, at maximum, higher than that at the inlet of heat exchanger. As the wet bulb temperatures were increased, the pressure drop was linearly increased due to the increment of frost mass. And the increment of heat exchange rate was smaller than that of inlet air enthalpy due to the increment of frost mass. The pressure drop of air side was rapidly increased due to the progress of frosting phenomena. The run time that the pressure drop occurred rapidly was decreased by the growth of frost.

• 유기물자원화
• /
• 제23권4호
• /
• pp.52-62
• /
• 2015

본 연구에서는 퇴비화공정에서 첨가재로 주로 사용되는 톱밥을 대상으로 톱밥 내 공기투과성 변화에 영향을 미치고 있는 요인별 특성과 총차감압력에 미치는 기여도를 평가하였다. 공기투과성 변화에의 영향요소로서 층류속도(v), 난류속도($v^2$), 수분함량(MC*v), 공기공극률(AFP*v), 입자크기(SIZE*v)를 선정하여 차감압력 산정을 위한 회귀식을 제시하였다. 차감압력에의 증가요인은 층류속도(v)와 입자크기(SIZE*v)이며, 감소요인은 난류속도($v^2$), 수분함량(MC*v), 공기공극률(AFP*v)이다. 공기유입속도를 높이면 총차감압력이 지속적으로 증가하였으며, 이러한 총차감압력 변화에 영향을 크게 미치는 증가요인은 입자크기(SIZE*v)이며, 감소요인은 공기공극률(AFP*v)이다. 또한 총차감압력에의 증가기여도는 낮은 유속에서는 층류속도(v)가 높은 유속에서는 입자크기(SIZE*v)의 기여도가 높았으며, 감소기여도는 공기공극률(AFP*v)이 가장 높았다. 반면에 수분함량 변화에 따른 총차감압력 변화는 그리 크지 않았다. 따라서 총차감압력은 증가요인보다는 감소요인인 공기공극률(AFP*v)과 수분함량(MC*v)에 의하여 영향을 받고 있음을 알 수 있다. 본 연구결과로서, 효율적 퇴비화공정을 위하여는 적정 수분함량 유지와 함께 공기공극률이 높은 첨가재를 선정하여 공기투과성을 향상시키는 방법이 적절할 것이다.

• 한국대기환경학회지
• /
• 제13권3호
• /
• pp.193-205
• /
• 1997

Experiments on granular filtration of polydispersed aerosols were conducted to determine the changes in pressure drop necessary to maintain a given gas flow rate as filter becomes clogged with deposited particles. Among the various variables which affect the increase in the pressure drop during the filtration, the most important one was found to be the size of the deposited aerosol particles. It was shown that for a given extent of the total deposition, the extent of increase in pressure drop increases with the decrease of the deposited aerosol size. For the general case where the deposited particles have different sizes, a procedure was proposed for correlating and predicting experimental results on pressure drop. This procedure was found applicable to bidispersed aerosols and polydispersed aerosols.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권4호
• /
• pp.70-80
• /
• 1996

Experimental results for forced convection condensation of R-22 and R-407C inside 7.5mm ID and 4000mm length of horizontal tubes are presented. The experimental data covered total flow rate from 114.3 to 267.1kg/($m^2$.s) and quality from 0 to 1. The vapor temperature and pressure drop along the tube were measured. The pressure drop for R-407C increased with flow rate similar to that of R-22. The experimental data compared with the available perdictions for pressure drop. Based on the data a prediction method was presented for the calculation of pressure drop of R-22 alternative refrigerants.

• 한국산업융합학회 논문집
• /
• 제20권2호
• /
• pp.157-168
• /
• 2017

The pressure drop characteristics of air particle flow in a powder transport piping system were analyzed in this study. The pressure drop characteristics of air particle flow in the piping system have not well understood due to the complexibility of particle motion mechanism. Particles or powders suspended in the air flow cause the increase of the pressure drop and affect directly transport efficiency. In this study, the pressure drop in a powder transport piping system was analyzed with interactions of air flow and particle motion in straight and curved pipes. The total pressure drop increased with pipe length, mixture ratio, and friction factor of particles because of increased friction loss of air and particles in the piping system. For the coal powders of $74{\mu}msize$ and powder-to-air mass mixture ratio of 0.667, the total pressure drop under the consideration of powders and air flow was calculated as much as 30% higher than that air flow only.

• 한국자동차공학회논문집
• /
• 제7권7호
• /
• pp.187-194
• /
• 1999

In the design of catalytic converter, velocity distribution is more important than pressure drop because monolith pressure drop is about 80% of overall pressure drop. For the catalytic converter with single diffuser, pressure drop is decreased as the angle of diffuser decrease, but when the angle is below 18$^{\circ}$, the effect is almost negligible . For the catalytic converter with double diffuser, variation of the angle of the first diffuser shows the same trend as the pressure drop while the shape of diffuser gives little influence on that The outlet shape gives negligible effect on the pressure drop and velocity . distribution . Results show that recirculation region of commercial model is aoubt 30% of the total area in the front of monolith. For the catalytic converter with Model 11 that was presented in the study, recirculation region was not detected more uniform velocity distribution was obtained, and pressure drop was also decreased.

• Nuclear Engineering and Technology
• /
• 제54권1호
• /
• pp.117-129
• /
• 2022

The downward discharge of the molten fuel to the lower structure of the fuel assembly could increase of the pressure drop and degrade of coolability of the assembly. To analyze the phenomena, experiments for the generation of the debris bed were conducted as LOF-DT series. Based on the debris bed in the LOF-DT, pressure drop experiment was conducted with intact and blocked component. Parametric study on the pressure drop was conducted by CFD. The LOF-DT experiments were conducted for the position and porosity of the debris bed. 85% of the debris were sedimented in the lower reflector, and 15% were in the nose piece, approximately. Porosity of the debris bed were about 0.7 and 0.85 in the lower reflector and nose piece, respectively. Pressure drop increased significantly with debris bed, especially in the lower reflector. More than 120 time of the pressure drop increased in the lower reflector, while only 10% increased in the nose piece. According to the parametric study, mass of the debris was the most important for pressure drop. The lower discharge phenomena could have a significant effect to the total pressure drop of the fuel assembly, approximately 10.8 times for the base case.