• Title/Summary/Keyword: heat transfer characteristics

Search Result 2,671, Processing Time 0.027 seconds

Experimental study on the characteristics of heat transfer for new type aluminum tube (신형 알루미늄관의 열전달 특성에 관한 실험적 연구)

  • 문춘근;윤정인;김재돌
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.24 no.2
    • /
    • pp.31-37
    • /
    • 2000
  • This study investigated heat transfer characteristics of refrigeration system using new type aluminium heat transfer tube for evaporator of refrigeration and air-conditioning comparing with bare tube. From the result of heat transfer experiment form one phase flow using cooled and hot water, about 20% heat transfer performance is superior in case of same quantity of flow and about 4% heat transfer performance if superior in case of same velocity comparing with bare tube. Casing of two phase flow, heat transfer performance of new type aluminum heat transfer tube shows about 50% superior heat transfer performance comparing with bare tube in the same evaporating pressure when using heat transfer tube as evaporator and shows about 47% increase when expressing performance coefficient as the rate of refrigerating capacity and compressing work. However, it can be known that pressure drop in the heat transfer tube is taken higher value of about 18% in case of new type aluminum heat transfer tube. From the above result, new type aluminum heat transfer tube is excellent comparing with bare heat transfer tube using the existing heat exchanger for refrigerator.

  • PDF

Conjugate Heat Transfer Characteristics in a Ribbed Channel:Effect of Reynolds Number and Heat Capacity Ratio (요철이 설치된 채널 내에서 레이놀즈수와 열용량비에 따른 복합열전달 특성)

  • Song, Jeong-Chul;Ahn, Joon;Lee, Joon-Sik
    • Proceedings of the KSME Conference
    • /
    • 2007.05b
    • /
    • pp.2297-2302
    • /
    • 2007
  • Numerical simulations are conducted to analyze conjugate heat transfer characteristics in a ribbed channel. In this simulation, the effects of Reynolds number and heat capacity of the solid channel wall on convective heat transfer are observed in the turbulent flow regime. In the case of the conducting wall against isothermal wall, the relative ratio of the thermal resistance between the solid wall and the flow field varies with Reynolds number. Thus the characteristics of the conjugate heat transfer are changed with the Reynolds number. Heat capacity ratio affects the temperature fluctuation inside solid wall. The temperature fluctuation inside the solid wall decreases with increasing the heat capacity of the solid wall so that the convective heat transfer increases. When the thermal conductivity ratio is smaller than 10, the effects of flow characteristics on heat transfer are changed.

  • PDF

An Experimental Study on the Heat Transfer Characteristics of Corrugated Impinging Jets (파형 충돌분류의 열전달 특성에 관한 실험적 연구)

  • Kim, Ye Yong;Kim, Kui Soon
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.23 no.3
    • /
    • pp.320-329
    • /
    • 1999
  • An experimental study has been performed to investigate the heat transfer characteristics of impinging jets with corrugated nozzle and wake generation plate. Three different shapes of corrugated nozzle and five different shapes of wake generation plate were tested to improve the heat transfer characteristics of impinging jet. Heat transfer coefficients were obtained by using transient method based on the liquid crystal thermography. The effects of corrugated nozzle and wake generation plate on the heat transfer characteristics of impinging jets were discussed in detail. The results showed that both the corrugated nozzle and the wake generation plate improved the heat transfer characteristics of impinging jet. Especially, heat transfer coefficients around stagnation region of impinging jets were highly increased.

EXPERIMENTAL INVESTIGATION OF CONVECTIVE HEAT TRANSFER IN A NARROW RECTANGULAR CHANNEL FOR UPWARD AND DOWNWARD FLOWS

  • Jo, Daeseong;Al-Yahia, Omar S.;Altamimi, Raga'i M.;Park, Jonghark;Chae, Heetaek
    • Nuclear Engineering and Technology
    • /
    • v.46 no.2
    • /
    • pp.195-206
    • /
    • 2014
  • Heat transfer characteristics in a narrow rectangular channel are experimentally investigated for upward and downward flows. The experimental data obtained are compared with existing data and predictions by many correlations. Based on the observations, there are differences from others: (1) there are no different heat transfer characteristics between upward and downward flows, (2) most of the existing correlations under-estimate heat transfer characteristics, and (3) existing correlations do not predict the high heat transfer in the entrance region for a wide range of Re. In addition, there are a few heat transfer correlations applicable to narrow rectangular channels. Therefore, a new set of correlations is proposed with and without consideration of the entrance region. Without consideration of the entrance region, heat transfer characteristics are expressed as a function of Re and Pr for turbulent flows, and as a function of Gz for laminar flows. The correlation proposed for turbulent and laminar flows has errors of ${\pm}18.25$ and ${\pm}13.62%$, respectively. With consideration of the entrance region, the heat transfer characteristics are expressed as a function of Re, Pr, and $z^*$ for both laminar and turbulent flows. The correlation for turbulent and laminar flows has errors of ${\pm}19.5$ and ${\pm}22.0%$, respectively.

Heat Transfer Characteristics of a Circular Fin-tube Heat Exchanger (원형휜-원형관의 열전달 특성)

  • 강희찬;조동영;강민철
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.15 no.9
    • /
    • pp.762-767
    • /
    • 2003
  • An experimental study was conducted to investigate the heat transfer characteristics of a circular finned-tube heat exchanger. The nineteen cases of configuration varying fin material, fin outer diameter and fin pitch were tested by means of the experiment and the numerical calculation. The measured heat transfer data for the circular finned-tube heat exchanger were provided. A transition of heat transfer was found in the case of low fin pitch. The thermal conductivity of fin affected on the pure heat transfer coefficient.

An experimental study on the heat transfer augmentation by using the multiple orifice nozzle (다중 오리피스 노즐을 이용한 충돌분류의 열전달 향상에 관한 실험적 연구)

  • 김예용;정기호;김귀순;서태범
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.11 no.5
    • /
    • pp.647-657
    • /
    • 1999
  • An experimental study has been peformed to investigate the heat transfer characteristics of impinging jets with multiple orifice nozzles. Four different shapes of multiple orifice nozzle were tested to improve the heat transfer characteristics of impinging jet. Heat transfer coefficients were obtained by using transient and steady method based on the liquid crystal thermography, and both methods showed very similar results. The effects of multiple orifice nozzles on the heat transfer characteristics of impinging jets were discussed in detail. The results showed that multiple orifice nozzles improved the heat transfer characteristics of impinging jet. Especially, heat transfer coefficients around stagnation region of impinging jets were highly increased.

  • PDF

A Study on the Heat Transfer Characteristics of a Self-Oscillating Heat Pipe

  • Yoon, Seok-Hun;Cheol Oh;Park, Jae-Hyuk
    • Journal of Mechanical Science and Technology
    • /
    • v.16 no.3
    • /
    • pp.354-362
    • /
    • 2002
  • In this paper, the heat transfer characteristics of a self-oscillating heat pipe are experimentally investigated for the effect of various working fluid fill charge ratios and heat loads. The characteristics of temperature oscillations of the working fluid are also analysed based on chaotic dynamics. The heat pipe is composed of a heating section, a cooling section and an adiabatic section, and has a 0.002m internal diameter, a 0.34m length in each turn and consists of 19 turns. The heating and the cooling portion of each turn has a length of 70mm. A series of experiments was carried out to measure the temperature distributions and the pressure variations of the heat pipe. Furthermore, heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients are calculated for various operating conditions. Experimental results show the efficacy of this type of heat pipe.

Performance and Heat Transfer Characteristics of Heat Pump System Using Refrigerant Mixtures (혼합냉매를 사용한 열펌프 시스템의 성능과 열전달 특성)

  • Kim, T.S.;Shin, J.Y.;Ro, S.T.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.4 no.4
    • /
    • pp.360-369
    • /
    • 1992
  • A heat pump system is constructed to evaluate its performance and heat transfer characteristics with mixtures of R22/R142b as working fluids. The heat transfer in the evaporator and the overall performance are measured and analyzed in terms of the compositions and relevant variables. Possibility of capacity modulation by changing composition is observed without degradation of heat transfer coefficients and coefficient of performance. The cooling capacity is varied continuously within 200 percent based on minimum capacity at constant compressor speed. For similar cooling capacity, COP is improved by mixing two refrigerants and shows maximum value at 60% mass fraction of R22. Average heat transfer coefficients of mixtures decrease in comparison with pure refrigerants at similar cooling capacity and mass flow rate. However, the overall heat transfer coefficients decrease moderately. A cycle simulation is performed in order to manifest the advantages of using refrigerant mixtures, considering experimentally observed heat transfer characteristics.

  • PDF

Heat Transfer Characteristics on Design Conditions of Finned-Tube Evaporators (설계조건에 따른 핀-튜브 증발기의 열전달 특성)

  • 강희정;이윤수;권영철;장근선;김영재
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.14 no.1
    • /
    • pp.46-54
    • /
    • 2002
  • To investigate the design effects of a heat exchanger on a tube type, a tube circuit and a fin pitch, an experimental study on the heat transfer characteristics of finned- tube evaporators was performed. The refrigerant was R-22. A refrigerant loop was established to measure the heat transfer rate, the air heat transfer coefficient. The experimental results showed that the heat transfer characteristics of the evaporators were affected by the design parameters. And the heat transfer rate of the slit fin was better about 25%, compared to those of the louver fin. In the present experimental range, the heat transfer performance with the straight tube circuit was more remarkable than that of the zigzag tube circuit, as seen from temperature variations of the evaporator exit. $\jmath$-factor on the tube type, the tube circuit and the fin pinch decreased, as increasing Reynolds number.

A Study on the Heat Transfer Characteristics of Loop Type Capillary Heat Pipe (루프형 세관 히트 파이프의 열전달특성에 관한 연구)

  • Yoon, Suck-Hun;Choi, Jae-Hyuck
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.24 no.3
    • /
    • pp.346-353
    • /
    • 2000
  • In this paper, heat transfer characteristics of a loop type capillary heat pipe were experimentally investigated for the effect of several fill charge ratios of working fluid and heat loads. This type of heat pipe consists of a heating section, a cooling section and an adiabatic section. The heat pipe used has a 0.002m internal diameter, a 0.34m length in one turn and consists of 19 turns. Heating and cooling sections each have a length of 70mm. Experiments were performed to measure the temperature distributions and the pressure variation of the heat pipe. Heat transfer performance, effective thermal conductivity, boiling heat transfer and condensation heat transfer coefficients were calculated for various operating conditions of heat pipe and it was found that heat transfer characteristics of this type heat pipe were very excellent. As shown by this experimental study, this type of heat pipe operates by oscillatory flow caused by pressure and temperature oscillations.