Distribution of Air-Water Two-Phase Flow in a Flat Tube Heat Exchanger

알루미늄 다채널 평판관 증발기 내 냉매분배

  • Published : 2006.10.01

Abstract

The R-134a flow distribution is experimentally studied for a heat exchanger composed of round headers and 10 flat tubes. The effects of tube protrusion depth as well as mass flux, and quality are investigated, and the results are compared with the previous air-water results. The flow at the header inlet is stratified. For the downward flow configuration, the liquid distribution improves as the protrusion depth or the mass flux increases, or the quality decreases. For the upward configuration, the liquid distribution improves as the mass flux or quality decreases. The protrusion depth has minimal effect. For the downward configuration. the effect of quality on liquid distribution is significantly affected by the flow regime at the header inlet. For the stratified inlet flow, the liquid is forced to rear part of the header as the quality decreases. However, for the annular inlet flow, the liquid was forced to the frontal part of the header as the quality decreased. For the upward flow, the effect of the mass flux or quality on liquid distribution of the stratified inlet flow is opposite to that of the annular inlet flow. The high gas velocity of the annular flow may be responsible for the trend. Generally, the liquid distribution of the stratified inlet flow is better than that of the annular inlet flow. Possible explanation is provided from the flow visualization results.

References

  1. Bullard, C. W., 2002, Design trade-offs in micro-channel heat exchangers, ACRC Report #124
  2. Webb, R. L. and Chung, K., 2004, Twophase flow distribution in tubes of parallel flow heat exchangers, Heat Transfer Engineering, Vol. 26, pp.3-18
  3. Hrnjak, P., 2004, Flow distribution issues in parallel flow heat exchangers, ASHRAE Annual Meeting, AN-04-1-2
  4. Lee, S. Y. and Lee, J. K., 2005, Aspects of two-phase .distribution on header-channels assembly, Proceedings of the International Conference on Enhanced, Compact and Ultra-Compact Heat Exchangers: Science, Engineering and Technology, CHE 2005-46, Engineering Conference International, Sep, 11-16
  5. Watanabe, M., Katsuda, M. and Nagata, K., 1995, Two-phase flow distribution in multipass tube modeling serpentine type evaporator, ASME/JSME Thermal Engineering Conf., Vol. 2, pp. 35-42
  6. Tompkins, D. M., Yoo, T., Hrnjak, P., Newell, T. and Cho, K, 2002, Flow distribution and pressure drop inmicro-channel manifolds, 9th Int. Refrigeration and Air Conditioning Conference at Purdue, R6-4
  7. Vist, S. and Pettersen, J., 2004, Two-phase flow distribution in compact heat exchanger manifolds, Exp. Thermal Fluid Sci., Vol. 28, pp. 209-215 https://doi.org/10.1016/S0894-1777(03)00041-4
  8. Lee, J. K. and Lee, S. Y., 2004a, Distribution of two-phase annular flow at header-channel junctions, Exp, Thermal Fluid Sci., Vol. 28, pp. 217-222 https://doi.org/10.1016/S0894-1777(03)00042-6
  9. Lee, J. K. and Lee, S. Y., 2004b, Two-phase flow behavior inside a header connected to multiple parallel channels, Proceedings of 3rd International Symposium on Two-Phase Flow Modelling and Experimentation, Pisa, Italy
  10. Cho, H., Cho, K. and Kim, Y., 2003, Mass flow rate distribution and phase separation of R-22 in multi-microchannel tubes under adiabatic condition, 1st lnt. Conf. Microchannels and Minichannels, pp.527-533
  11. Kim, N. H., Shin, T. R. and Sim, Y. S., 2006, Distribution of air-water two-phase flow in a header of aluminum flat tube evaporator, J. SAREK, Vol. 18, No. 1, pp. 55-66
  12. Kim, N. H., Han, S. P. and Park, T. K, 2006, Two-phase distribution in a header of a parallel flow heat exchanger, 13th Int. Het Transfer Conference, Sydney, Aug. 13-18