Effect of External Recycle on the Performance in Parallel-Flow Rectangular Heat-Exchangers

Ho-Ming Yeh

doi:10.6180/jase.2010.13.4.06

Effect of External Recycle on the Performance in Parallel-Flow Rectangular Heat-Exchangers

Ho-Ming Yeh This email address is being protected from spambots. You need JavaScript enabled to view it.¹

¹Energy and Opto-Electronic Materials Research Center, Department of Chemical and Materials Engineering, Tamkang University, Tamsui, Taiwan 251, R.O.C.

Received: July 13, 2009
Accepted: December 15, 2009
Publication Date: December 1, 2010

Download Citation: ||https://doi.org/10.6180/jase.2010.13.4.06

ABSTRACT

The analysis of heat transfer in the heat exchangers of cocurrent and countercurrent flows with external recycle, has been carried out by heat-transfer theory. Considerable improvement is achievable by recycle operation if the increase in heat-transfer coefficient by applying the recycle effect to enhance the fluid velocity, can compensate for the decrease in the driving force (temperature difference) of heat transfer due to the remixing of inlet fluid. As expected, the heat-transfer rate obtained in the countercurrent-flow heat exchangers with or without recycle are superior to those in the cocurrent-flow devices. However, the space for the improvement in performance by recycle in the countercurrent-flow device is smaller than that in the cocurrent-flow one.

Keywords: Heat Exchanger, External Recycle, Parallel Flow

REFERENCES

[1] Korpijarvic, J., Oinas, P. and Reunaneu, J., “Hydrodynamics and mass transfer in airlift reactor”, Chem. Eng. Sci., Vol. 54, PP. 2255-2262 (1998).
[2] Santacesaria, E., Di Serio, M. and lengo, P., “Mass transfer and kinetics in ethoxylation spray tower loop reactors”, Chem. Eng. Sci., Vol. 54, PP. 1499-1504 (1999).
[3] Atenas, M., Clark, M. and Lazarova, V., “Holdup and liquid circulation velocity in a rectangular air-lift bioreactor”, Ind. Eng. Chem. Res., Vol. 38 (3), PP. 944-949 (1999).
[4] Ho, C.D., Yeh, H.M. and Sheu, W.S., “An analytical study of heat and mass transfer through a parallel-plate channel with recycle”, Int. J. of Heat and Mass Transfer, 41, 2589-2599 (1998).
[5] Ho, C.D., Yeh, H.M. and Sheu, W.S., “The influence of recycle on double-pass heat and mass transfer through a parallel-plate device”, Int. J. of Heat and Mass Transfer, Vol. 42 (9), PP. 1707-1722 (1999).
[6] Yeh, H.M., Tsai, S.W. and Lin, C.S., “A study of the separation efficiency in thermal diffusion column with a vertical permeable barrier”, AIChE J., Vol. 32, PP. 971-980 (1986).
[7] Yeh, H.M., Tsai, S.W. and Chiang, C.L., “Recycle effects on heat and mass transfer through a parallel-plate channel”, AIChE J., Vol. 33, PP. 1743-1746 (1987).
[8] Yeh, H.M., Ho, C.D., “Solar air heaters with external recycle”, Applied Thermal Engineering, Vol. 29, PP. 1694-1701 (2009).
[9] Bird, R.B., Stewart, W.E. and Lightfoot, E.N., “Transport Phenomena”, 2^nd ed., New York, John Wiley & Sons, Inc., P.435,(2002).
[10] Middleman, S., “An Introduction to Mass and Heat Transfer”, New York, John Wiley & Sons, Inc., P. 468, (1998).
[11] Geankoplis, C.J., “Transport Processes and Unit Operations”, 2^nd ed., Boston, Allyn and Bacon, Inc., P.805, (1983).