An experimental and theoretical investigation into the hyperbolic nature of axial dispersion in packed beds

The concept of hyperbolic axial dispersion of heat in a flowing fluid which is known as `third sound waveʹ has been examined taking packed bed as an example. This technique analyse fluid flow and heat transfer by introducing an axial dispersion term in the one-dimensional energy equation to take care of flow maldistribution and backmixing. The present approach models this dispersion in terms of two parameters which are proposed to follow hyperbolic conduction law. A regenerator bed consisting of stainless steel wire mesh packing has been used to carry out experiments for the purpose of validating the concept. The analytical model presented uses a Laplace transform technique for the solution of simplified energy equation. The computed outlet fluid temperature is compared with experimental output and the two model parameters, dispersive Peclet number (Pe) and its propagation velocity (c*) are estimated. The present model, the parabolic (Fourier) dispersion model and the non-dispersive plug flow model are compared with the experimental result which brings out the closeness of the present proposition to reality compared to other models. A standard experimental technique is suggested which can be used for the measurement of parameters related to axial dispersion. The present study is the first experimental evidence of `third sound waveʹ in fluids and lays foundation of this proposition.