• Title/Summary/Keyword: air temperature drop

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Effect of Filler on the Flow of Counter Flow Type Cooling Tower (충진재(Filler)가 대향류형(Counter Flow Type) 냉각탑 유동에 미치는 영향에 대한 연구)

  • Shin, Jeong-Hoon;Lee, Jun-Kyoung;Jin, Cheol-Gyu
    • Journal of the Korean Society of Industry Convergence
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    • v.25 no.4_2
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    • pp.565-572
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    • 2022
  • The white plume from the cooling tower can be generated by mixing between discharging hot and humid air and cold air outside. This causes various problems such as icing, traffic disturbances, and fire factors in the vicinity, moreover it can also damage the image of a company. Various methods can be used to prevent white plume, one of them is to install a heat exchanger at the outlet of the cooling tower so that the heat exchanger transfers as much heat as possible to lower the temperature. Therefore the air flow path in the cooling tower should be optimized. Installation of the filler can be used to make the air flow better, thus we investigate the effect of filler on the air flow using CFD method. The pressure and velocity profile in the cooling tower could be acquired by the calculations. The filler made the velocity of the air entering the heat exchanger uniform this was because high flow resistance of the filler suppresses the generation of eddy in the cooling tower. But the total air pressure drop increased about 2 times with filler because the pressure drop by the filler accounted for about 60% of the total pressure drop.

The pressure drop characteristics in LNG heat exchanger of cryogenic cascade refrigeration cycle (초저온 캐스케이드 냉동사이클의 LNG 열교환기 압력강하 특성)

  • Yoon, J.I.;Choi, K.H.;Kwag, J.W.;Son, C.H.;Baek, S.M.
    • 한국태양에너지학회:학술대회논문집
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    • 2012.03a
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    • pp.376-381
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    • 2012
  • Natural gas is converted in to LNG by chilling and liquefying the gas to the temperature of $-162^{\circ}C$, when liquefied, the volume of natural gas is reduced to 1/600th of its standard volume. This gives LNG the advantage in transportation. The pressure dorp of the cascade liquefaction cycle was investigated and simulated using HYSYS software. The simulation results showed that the pressure drop in the LNG heat exchanger is set to 50 kPa considering the increase in the compressor work of cryogenic cascade liquefaction cycle.

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A Numerical Study on Evaporation and Combustion of Liquid Spray (액체분무의 증발 및 연소에 관한 수치적 연구)

  • 정인철;이상용;백승욱
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.2073-2082
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    • 1991
  • The vaporization and combustion of liquid spray in a cylindrical shape combustor was studied numerically. Mixture of liquid drops and air was assumed to be ejected from the center-hole and assisting air from the concentric annulus with swirling. Eulerian-Lagrangian scheme was adopted for the two phase calculation, and the interactions between the phases were considered with the PSIC model. Also adopted were the infinite conductivity model for drop vaporization, the equation of Arrhenius and the eddy break-up model for reaction rate, and the k-epsilon model for turbulence calculations. Gas flow patterns, drop trajectories and contours of temperature and mass fractions of the gas species were predicted with swirl number, drop diameter, and equivalence ratio taken as parameters. Calculations show that the vaporization and the consequent combustion efficiency enhance with the increase of the swirl number and/or with the decrease of drop size, and the higher maximum temperature is attained with the higher equivalence ratio.

Numerical Shape Optimization for Plate-Fin Type Heat Sink (평판-휜형 방열판의 수치적 형상최적화)

  • 김형렬;박경우;최동훈
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.16 no.3
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    • pp.293-302
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    • 2004
  • In this study the optimization of plate-fin type heat sink for the thermal stability is peformed numerically. The optimum design variables are obtained when the temperature rise and the pressure drop are minimized simultaneously. The flow and thermal fields are predicted using the finite volume method and the optimization is carried out by using the sequential quadratic programming (SQP) method which is widely used in the constrained non-linear optimization problem. The results show that when the temperature rise is less than 34.6K, the optimal design variables are as follows; B$_1$=2.468mm, B$_2$=1.365mm, and t=10.962mm. The Pareto optimal solutions are also presented for the pressure drop and the temperature rise.

Effect of the Heat Exchange between Low and High Temperature Refrigerant on the Heat Pump Performance (저온측과 고온측 냉매간 열교환이 열펌프의 성능특성에 미치는 영향)

  • 이건중;송현갑
    • Journal of Biosystems Engineering
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    • v.24 no.4
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    • pp.343-350
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    • 1999
  • The ambient air is commonly used as low-temperature heat source for heat pump operation. However, the coefficient of performance(COP) of the air to water heat pump is decreased with the ambient air temperature drop. In this study to solve this problem, the AVACTHE(Automatic Variable Area Capillary Type Heat Exchanger) with 3 levels of heat exchange area(0, 1,495.4, 1,794.5$\textrm{cm}^2$)was installed in the refrigerant circuit of the heat pump. The AVACTHE effect on the performance of heat pump was tested with the ambient air temperature variation. The COP improvement of the heat pump could be achieved by the AVACTHE installation when below -5$^{\circ}C$ of the ambient air temperature.

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Effect of the Heat Exchange between Low and High Temperature Refrigerant on the Heat Pump Performance (저온측과 고온측 냉매간 열교환이 열펌프의 성능특성에 미치는 영향)

  • 이건중;송현갑
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • 1999.12a
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    • pp.211-218
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    • 1999
  • The ambient air is commonly used as low-temperature heat sources for heat pump operation. However, the coefficient of performance (COP) of the air -water heat pump is decreased with the ambient air temperature drop. In this study to solve this problem , the AVACTHE(Automatic Variable Area Capillary Type Heat Exchanger) with 3 levels of heat exchange area(0, 1495.4, 1794.5$\textrm{cm}^2$) was installed in the refrigerant circuit of the heat pump. The AVACTHE effect on the performance of heat pump was tested with the ambient air temperature variation. The high level COP of the heat pump could be achieved by the AVACTHE installation when below -5$^{\circ}C$ of the ambient air temperature.

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A Study on the Component Performance for Automotive Air Conditioner (자동차용 에어컨의 단품 성능에 관한 연구)

  • 이대웅;유성연
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.14 no.4
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    • pp.293-303
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    • 2002
  • For successful design of component, performances of one-tank plate type evaporator, gas-liquid separation type condenser, swash plate type compressor and thermostatic expansion valve for automotive air conditioner are investigated experimentally. Heat transfer characteristics in the evaporator are examined by means of air temperature, relative humidity, air volume flow, outlet refrigerant pressure and superheat, and heat transfer characteristics in the condenser are examined by means of air temperature, air velocity and inlet refrigerant pressure. Pressure drops for both evaporator and condenser are measured arid empirical correlations are derived. Volumetric efficiencies and isentropic efficiencies for trio types of compressors with different capacity are measured and compared. Thermostatic expansion valve is tested to investigate the pressure variation according to temperature changes.

Numerical Simulation of Plate Finned-Tubes Evaporator (평판핀이 부착된 증발기의 시뮬레이션)

  • Son, B.J.;Min, M.S.;Choi, S.G.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.1 no.4
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    • pp.297-304
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    • 1989
  • Development of a more satisfactory program of computing the performance on a multi-tube evaporator with continuous plate fins is attempted in this study. The fluid flow involving a change of phase make the flow properties and fluid friction factor of refrigerants, the heat transfer coefficients of refrigerant and air sides vary significantly. Taking such variations into account, a useful program is developed to predict the steady state performance of a multi-tube evaporator. The program was applied to an evaporator which has outside diameter of 10.05mm, inside diameter of 9.35mm, length of 5.4m and two rows arraied staggered. Then the variations of refrigerant quality, temperature, pressure, velocity, enthalpy, specific volume and air temperature, tube temperature were discussed. Satisfactory results were presented that the degree of superheat at the outlet side was $4.4^{\circ}C$ and the air temperature drop between the inlet and outlet of the air conditioner was $10^{\circ}C$.

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Forced Convection Heat Transfer for Two Circular Tube Arrays with Annular Fins (환형휜이 부착된 두 개의 원형관 배열에 대한 강제대류 열전달)

  • Kim, Seung-iI;Park, Sang-Hee
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.6_2
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    • pp.1093-1101
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    • 2020
  • This study was carried out numerically to investigate the air flow and thermal performance around single and parallel fin-tube heat exchangers and the cooling performance of the fluid inside the heat exchangers. In this study, the air velocity(1~7m/s), the pitch of fin(4, 6.1, 8, 11.3, 18.3, 44mm) and the diameter of fin(31, 33, 35, 37, 39mm) were varied. The flow rate of the water at the fin-tube heat exchanger inlet is 89cc/min and the water temperature is 353K. The air temperature at the upstream region of the heat exchanger is 300K. flow rate of the water at the fin-tube heat exchanger inlet is 80cc/min and the water temperature is 353K. It was found that the air pressure drop around single and parallel fin-tube heat exchangers was highly dependent on the air velocity and the fin pitch, but was independent of the fin diameter. Also, it was shown that pressure drop increased more the parallel arrangements than in single heat exchanger. The temperature difference of water at the inlet and outlet of the heat exchanger depended on the air velocity, the fin pitch and the fin diameter, and it was found that the parallel arrangement method further reduced the temperature of water. It was shown that the Nusselt number increased as the Reynolds number and the fin pitch increased, and decreased as the fin diameter increased.

Heat and mass transfer characteristics in a vertical absorber (수직형 흡수기내 열 및 물질 전달 특성)

  • 서정훈;조금남;최기봉
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.11 no.6
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    • pp.835-845
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    • 1999
  • The objective of the present study was to investigate heat and mass transfer characteristics in a vertical falling film type absorber using LiBr-$H_2O$ solution with 6owt%. The experimental apparatus consisted of an absorber with inner diameter of 17.2 mm and length of 1150mm, a generator, an evaporator/condenser, a solution tank, a sampling trap etc. The parameters were solution temperature of 45 and $50^{\circ}C$, coolant temperature of 30 and $35^{\circ}C$, and film Reynolds numbers from 50 to 150. Pressure drop in the absorber increased as solution and coolant temperatures decreased. Pressure drop in the absorber increased up to the film Reynolds number of 90, and then decreased at the further increase of the Reynolds number above 90. The maximum absorption mass flux observed at the film Reynolds number of 90. Absorption mass flukes increased as coolant temperature decreased. Absorption mass fluxes and heat transfer coefficients under subcooled condition were larger than those under superheated condition. Heat transfer coefficients were affected by solution temperature more than coolant temperature. The maximum absorption effectiveness under the subcooled condition was 23% for coolant temperature of $30^{\circ}C$ and 31% for coolant temperature of $35^{\circ}C$ under the present experimental conditions.

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