Second law analysis of transient heat transfer for turbulent flow in a circular tube with baffle inserts

This paper presents the results of an experimental investigation of transient forced convective heat transfer for turbulent flow of nine circular tubes with baffle plate inserts using different pitch to tube inlet diameter ratios and baffle orientation angles in the range of Reynolds number 3000 <= Re <= 20000 in the case of constant heat flux. The characteristic parameters of the tubes are: pitch to tube inlet diameter ratio H/D = 1, 2 and 3; baffle orientation angle beta = 45, 90 and 180 degree. Air, having a Prandtl number of 0.71 was used as the working fluid, while stainless steel was considered as the pipe material. The data show that unsteady entropy generation numbers for the baffled tubes are higher than those from the steady one. A generalised correlation for the unsteady entropy generation number relative to the steady dimensional entropy generation number for the baffle inserted tubes has been developed

Effect of flow geometry parameters on transient heat transfer for turbulent flow in a circular tube with baffle inserts

The effect of the flow geometry parameters on transient forced convection heat transfer for turbulent flow in a circular tube with baffle inserts has been investigated. The characteristic parameters of the tubes are pitch to tube inlet diameter ratio H/D = 1, 2 and 3, baffle ;orientation angle beta = 45 degrees, 90 degrees and 180 degrees. Air, Prandtl number of which is 0.71, was used as working fluid, while stainless steel was considered as pipe and baffle material. During the experiments, different geometrical parameters such as the baffle spacing H and the baffle orientation angle beta were varied. Totally, nine types of baffle inserted tube were used. The general empirical equations of time averaged Nusselt number and time averaged pressure drop were derived as a function of Reynolds number corresponding to the baffle geometry parameters of pitch to diameter ratio HID, baffle orientation angle beta, ratio of smooth to baffled cross-section area S-o/S-a and ratio of tube length to baffle spacing L/H were derived for transient flow conditions. The proposed empirical correlations were considered to be applicable within the range of Reynolds number 3000 <= Re <= 20,000 for the case of constant heat flux. (c) 2006 Elsevier Ltd. All rights reserved

Energy dissipation analysis of transient heat transfer for turbulent flow in a circular tube with baffle inserts

In this paper energy dissipation analysis was conducted to evaluate the performance of nine circular tubes with baffle plate inserts having different pitch to tube inlet diameter ratio and baffle orientation angle in the range of Reynolds number 3000 <= Re <= 20,000 for the case of constant heat flux. The characteristic parameters of the tubes are pitch to tube inlet diameter ratio H/D = 1, 2, 3 and baffle orientation angle beta = 45, 90, 180 degrees. Air having Prandtl number is 0.71 was used as working fluid, while stainless steel is considered as a pipe material. As an evaluation criteria of i(E) has been proposed by Sano et al., which is based on correlating the heat transfer coefficient and the dissipation energy in a fluid has been considered to evaluate transient forced convection. The data show that unsteady dissipation energy criterion for the baffled tubes is higher than smooth tube and the type of 9031 has been found as the most effective one. (c) 2005 Elsevier Ltd. All rights reserved

Flow geometry optimization of channels with baffles using neural networks and second law of thermodynamics

Artificial Neural Networks results from an experimental study on the heat transfer and flow characteristics in channels with baffles are presented. Nine different types of channels with baffles were used in order to test the effects of baffle spacing to and the influence of baffle geometries and their positions on heat transfer, and their flow characteristics. Experiments were performed for laminar and turbulent flows, and Prandtl number of 0.7. The convective heat transfer coefficients and pressure drops provided by the experimental studies and artificially generated data were examined. Finally, the geometric features of the proposed flow geometry to improve heat transfer can be selected in order to yield the maximum opposite reduction in heat exchange channel irreversibility by using entropy generation minimization method. The experimental results for different design constraints show that optimum baffle position angle for laminar flow is 90degrees and for turbulent flow is 45degrees and baffle spacing modulo length ratio is 3 for laminar flow and two for turbulent flow, respectively. Then, some new data is generated using artificial neural networks for succession parameters. Also these generated data are compared with experimental results. New flow geometries are presented for the future applications