Experimental investigation of heat transfer enhancement factors in the oscillating flow heat exchanger using Kurzweg's and Nishio's correlations

In the present work, an experimental investigation of heat transfer enhancement parameters of the oscillating flow heat exchanger using Kurzweg's and Nishio's correlations is carried out. An oscillatory axial movement of fluid is established within the flow tube using piston cylinder mechanism. The experiments are carried out for seven different frequencies, five tidal displacements and four heat fluxes. It is observed that at a constant tidal displacement (S), experimental effective thermal conductivity (keff) increases progressively with frequency (f) up to a maximum and then decreases. The frequency corresponding to peak keff is an optimum frequency. In addition to this, it is also observed that with increase in S, the point of peak keff is shifted towards lower frequency. A similar trend is observed for axial heat flux (qa) and convective heat transfer coefficient (h). Based on the dimensional analysis and experimental data, an empirical correlation is obtained for experimental effective thermal diffusivity (αeff) as a function of the Womersley number (Wo) and the transition number (β). Finally the result shows that, in the oscillating flow heat exchanger, f, S, Prandtl number (Pr) of fluid, fluid thermal properties to wall thermal properties, and the ratio of length of cooling tube in heat sink (Lc) to S are primary influencing parameters.