Effect of flow geometry parameters on transient entropy generation for turbulent flow in circular tube with baffle inserts

The effect of flow geometry parameters on transient entropy generation for turbulent flow in a circular tube with baffle inserts has been investigated. Different flow geometry parameters of pitch to diameter ratio (H/D), baffle orientation angle (β), ratio of smooth to baffled cross-section area (So/Sa) and ratio of tube length to baffle spacing (L/H) were varied parametrically during the experiments. One smooth tube and nine different baffle inserted tubes geometries were tested. The characteristic parameters of the baffled tubes are pitch to tube inlet diameter ratio H/D = 1, 2 and 3; baffle orientation angle β = 45°, 90° and 180°. The time averaged entropy generation corresponding to the flow geometry parameters were compared under the condition of constant heat flux. Air having a Prandtl number of 0.71 was used as working fluid, while stainless steel was considered as the pipe and baffle material. Nine empirical equations were derived to correlate the time averaged entropy generation as a function of the Reynolds number and the other experimental individual flow geometry parameters, pitch to diameter ratio, baffle orientation angle, ratio of smooth to baffled cross section area and ratio of tube length to baffle spacing. Finally, the general empirical correlation of the time averaged entropy generation was developed and considered to be applicable within the range of Reynolds number 3000 ≤ Re ≤ 20,000 in the form ofSgenave (t) = 0.0054 Re- 0.793 Pr0.4 (H / D)- 0.656 (So / Sa)- 14.006 β- 0.0264 (L / H)- 0.6051 .. © 2006 Elsevier Ltd. All rights reserved.