Article,
Hyperbolic axial dispersion model: concept and its application to a plate heat exchanger
International Journal of Heat and Mass Transfer, 38 (16): 3065 - 3076 (1995)
DOI: 10.1016/0017-9310(95)00034-7
Abstract
A new concept of hyperbolic axial dispersion in fluid is introduced. This is an extension of the already established method of considering axial dispersion which takes the flow maldistribution into account in the analysis of heat exchangers. The concept is introduced by analogical treatment of the axial dispersion with the fluid conduction. Hyperbolic conduction, which considers a finite conduction wave propagation velocity, is important only in special cases such as cryogenic temperatures or sudden incidence of high heat flux. On the other hand the similar propagation velocity of the dispersion wave appears to be a general phenomenon which affects the thermal performance of heat exchangers even for common applications. Based on the proposed theoretical foundation, the dynamic analysis of a U-type plate heat exchanger is presented for step and sinusoidal change in one of the inlet temperatures. For this purpose the traditional inlet boundary condition for the dispersion model has been extended to incorporate the effect of the finite propagation velocity of the dispersion wave. The method of Laplace transforms has been applied for the analysis, and the Laplace inversion is carried out numerically using fast Fourier transforms. The results indicate that the proposed concept of 'hyperbolic dispersion' can be developed as a powerful tool for the analysis of heat exchangers particularly in the transient regime of operation.
