• Title/Summary/Keyword: Air side pressure drop

Search Result 103, Processing Time 0.042 seconds

Analysis of Mixed Convection Heat Transfer in Arbitrarily Shaped Flat Tubes (임의형상을 갖는 납작관에서의 혼합대류 열전달 해석)

  • 박희용;박경우;이상철
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.13 no.5
    • /
    • pp.398-410
    • /
    • 2001
  • The flow and heat transfer characteristics for three-dimensional mixed convection flows in a radiator flat tube with U--shaped grooves are analyzed numerically. The flow and temperature fields are calculated by using the modified SIMPLE algorithm for irregular geometry. One tube specification among the various flat tube exchangers is recommended by considering the heat transfer and pressure drop. The effects of variation of coolant flow conditions and external air conditions on the flow and the thermal characteristics for the selected tube are investigated. the results show that inlet velocity of coolant flow is the very important factor in heat transfer and pressure drop, and top side is better position than the others as fin cleave to tube.

  • PDF

Heat Transfer and Pressure Drop Characteristics in Zigzag Channel Angles of Printed Circuit Heat Exchangers (지그재그채널 PCHE의 각도에 따른 열전달 및 압력강하특성)

  • Choi, Mi-Jin;Kwon, Oh-Kyung;Cha, Dong-An;Yeun, Jae-Ho
    • Proceedings of the SAREK Conference
    • /
    • 2009.06a
    • /
    • pp.1147-1152
    • /
    • 2009
  • The objectives of this paper are to study the characteristics of heat transfer and pressure drop of the zigzag channel PCHE using diffusion bonding technology by numerical analysis. PCHE of five types are designed, which are zigzag channel angle $180^{\circ}$, $160^{\circ}$, $140^{\circ}$, $120^{\circ}$ and $100^{\circ}$. The zigzag PCHE was numerically investigated for Reynolds number in a range of $150{\sim}800$. The temperatures of the hot side were performed at $80^{\circ}C$ while that of the cold side was conducted at $20^{\circ}C$. The results show that the performance of heat transfer rate for zigzag channel $100^{\circ}$ increases about 11.5% compared to that of zigzag channel $180^{\circ}$. On the other hand, the performance of pressure drop for zigzag channel $100^{\circ}$ is remarkably higher than that of zigzag channel $180^{\circ}$, about 1.4 times.

  • PDF

Comparison of Heat Transfer Performance and Pressure Drop of Fin-Tube and Aluminum Heat Exchangers (핀-튜브 열교환기와 알루미늄 열교환기의 전열성능과 압력강하 특성비교)

  • Chang, Keun-Sun;Lee, Hyun-Su;Kim, Jae-Duck
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.10 no.2
    • /
    • pp.222-229
    • /
    • 2009
  • This study presents comparison of heat transfer and air side friction characteristics in a condenser condition of air conditioner between Louver fin-tube heat exchangers and aluminum parallel heat exchangers. All experiments are performed using an air-enthalpy type calorimeter, which is designed based on the method described in ASHRAE standards. The air velocities crossing the heat exchanger tubes are varied from 0.7 to 1.6 m/s with 0.3 m/s interval, maintaining air dry temperature and relative humidity at $20^{\circ}C$ and 60% respectively. Water temperature and flow rate inside the tube are $70^{\circ}C$ and 10 LPM, respectively. Experimental results show that the heat transfer performances of aluminum heat exchangers are 17-163% higher than those of Louver fin-tube heat exchangers based on the data per unit volume, mass, and heat transfer area, whereas air side pressure drops of aluminum heat exchangers are 19-81% lower.

Heat Transfer and Pressure Drop Characteristics of Cross-Flow Plastic Air Heater for a Cooling Tower (냉각탑용 직교류형 플라스틱 공기가열기의 열전달 및 압력손실)

  • Kim, Nae-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.14 no.12
    • /
    • pp.6072-6081
    • /
    • 2013
  • In this study, experiments were performed on air heater samples with three different shapes (chevron, wave and dimple type) to reduce the plumes from cooling towers. The tests were conducted for a range of frontal air velocities of 1~3 m/s and water flow rate 0.19~0.33 kg/s. The results showed that the heat transfer rate increased with increasing air velocity or water flow rate. The air-side pressure drop also increased with increasing air velocity. At the same frontal air velocity, the highest heat transfer rate was obtained for the chevron sample (1.5~1.7 times compared to that of the plate sample), followed by the dimple, wave and plate samples. The heat transfer rate per unit power consumption was also 15% larger than that of the dimple sample. On the other hand, there was no noticeable difference between the other samples.

Effect of Fin Pitch on Air Side Heat Transfer in Louvered-Fin Heat Exchanger (루우버핀 열교환기의 핀피치가 공기측 열전달에 미치는 영향)

  • Jang, B.J.;Kim, S.J.
    • Solar Energy
    • /
    • v.20 no.3
    • /
    • pp.31-38
    • /
    • 2000
  • In order to study on influence of fin pitch and shape of heat exchanger on the elevation of heat transfer efficiency, we make models of louvered fin type heat exchanger which was given a transformation of fin pitch in louvered fin type heat exchanger which are of en used now. And the influence of fin pitch on pressure drop and characteristics of heat transfer was experimented and analysed when air velocity and fin pitch was a variable. The results of experiment shows below. Pressure drop shows larger in louvered fin type heat exchanger than in plate fin type heat exchanger, size of pressure drop shows like this order that fin space is 4mm, 5mm, 6mm. Mean heat transfer coefficient shows higher in louvered fin type heat exchanger than in plate fin type heat exchanger, size of mean heat transfer coefficient by fin space shows same in both case in louvered fin type heat exchanger and plate fin type like this order that fin space is 4mm, 5mm, 6mm.

  • PDF

Prediction of Characteristics for the Air-side Particulate Fouling in Finned-Tube Heat Exchangers of Air Conditioners used in the Field (실공간 사용 공기조화기용 열교환기의 공기측 파울링 특성 예측)

  • Ahn, Young-Chull;Jung, Sung-Hak;Hwang, Yu-Jin;Lee, Chang-Gun;Kim, Doo-Hyun;Jung, Seong-Ir;Lee, Jae-Keun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.19 no.8
    • /
    • pp.563-568
    • /
    • 2007
  • The air-side particulate fouling in the heat exchangers of HVAC applications degrades the performances of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. Indoor and outdoor air contaminants foul heat exchangers. An empirical modeling equation has been derived from the experimental results using accelerated tests and it showed good predictions of the fouling characteristics of the slitted finned tube heat exchangers. However the modeling equation predicts only the fouling characteristics of new heat exchangers and it can not predicts fouling characteristics obtained from actual field data which contains the effect of hydrophilicity deterioration. Therefore an modified modeling equation is proposed and it shows good predictions of the actual fouling characteristics of finned-tube heat exchangers.

Study on Heat Transfer and Pressure Drop Characteristics of Internal Heat Exchanger for $CO_2$ Heat Pump under Cooling Condition ($CO_2$ 열펌프용 내부 열교환기의 냉방조건에서 열전달 및 압력 강하 특성에 대한 연구)

  • Kim, Dae-Hoon;Lee, Sang-Jae;Choi, Jun-Young;Lee, Jae-Heon;Kwon, Young-Chul
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.20 no.8
    • /
    • pp.517-525
    • /
    • 2008
  • In order to study the heat transfer and pressure drop of an internal heat exchanger for $CO_2$ heat pump under cooling condition, the experiment and numerical analysis were performed. Four kinds of internal heat exchangers with a coaxial tube type and a micro-channel tube type were used. The experimental apparatus consisted of a test section, a power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. The section-by-section method and Hardy-Cross method were used for the numerical analysis. The effects of the internal heat exchanger refrigerant flow rate, the length of the internal heat exchanger, the operating condition of the gas-cooler, the evaporator and the type of the internal heat exchangers were investigated. With increasing of the flow rate, the heat transfer rate increased about 25%. The heat transfer rate of the micro-channel tube type was higher about 100% than that of the coaxial tube type. With increasing of the length of the internal heat exchanger, the heat transfer rate increased about $20{\sim}50%$. The pressure drop of the low-side tube was larger compared with that of the high-side tube.

A Study of Dust Effect on Performance of Heat Exchangers with Louver and Wavy Fins (루버형과 파형핀 열교환기에서 분진이 성능에 미치는 영향에 관한 연구)

  • Lee, Young-Lim;Hwang, Soon-Ho
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.17 no.4
    • /
    • pp.126-132
    • /
    • 2009
  • Automotive heat exchangers use louver fins for their high efficiency. However, the efficiency can significantly drop for constructional vehicles or heavy equipments due to dust deposited on the louver fins with narrow slits. Thus it is necessary to develop new fins that lead to less fouling, so that a better performance can be achieved after exposure to a dusty environment over long period of time. New wavy fins were considered in the study and numerically analysed to compare with louver fins in the areas of air-side pressure drop, heat release rate, and particulate deposition. In addition, an experiment was done on the pressure drop and the particulate deposition. The results showed that the wavy fins would be a better choice for long-term use due to the excellent dust-proof performance in comparison to louver fins, in spite of the initial inferior performance of heat release.

Air-side Heat Transfer and Pressure Drop of a Fin-and-Tube Heat Exchanger Under Low Temperature Condition (저온 조건에서 핀-관 열교환기의 공기측 열전달 및 압력손실)

  • Kim, Nae-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.18 no.4
    • /
    • pp.15-20
    • /
    • 2017
  • Currently, residential air conditioners operate as a heat pump during winter. In this case, the outdoor heat exchanger acts as an evaporator obtaining heat from cold air. On the other hand, it acts as a condenser during summer transferring heat to hot air. The outdoor temperature changes significantly from high to low. Generally, the air-side j and f factors are obtained at a standard outdoor temperature. Therefore, the applicability of the j and f factors under different outdoor conditions needs to be checked. In this study, tests were conducted for a two-row louver finned heat exchanger changing the outdoor temperature to subzero. The effects of the tube-side brine flow rate were also checked. The results showed that air-side j and f factors were essentially constant and independent of the outdoor temperature, suggesting that an extension of j and f factors obtained under standard conditions to a low outdoor temperature is acceptable. All j and f factors agreed within 9% and 3%, respectively. Tests were also conducted by changing the coolant flow rate. Both the j and f factors did not change according to the flow rate, suggesting that the tube-side heat transfer correlation is acceptable.