Flow and Heat Transfer in a Simple Trapezoidal Minichannel Flow System

摘要

Incompressible flow through a minichannel system have been considered in the present study. The channel considered has a trapezoidal cross-section, the height of the cross-section being equal to the average width of the cross-section. The flow enters the channel with a uniform velocity and passes through a straight channel section that has a length that is 30 times the mean channel width. The flow then passes around a 90obend.Following the bend,the flow passes down another straight channel which also has a length of 30 times the mean channel width.A uniform heat flux is applied over the entire surface of the duct.The flow geometry does not represent any that is likely to occur in minichannel system applications but is adequate for the evaluation of the assumptions of- ten adopted regarding pressure losses,and heat transfer rates in real systems.It has been assumed that the flow is steady,that the flow is incompressible and that there is no slip on the channel walls.The governing equations have been written in dimensionless form.Solutions to these dimensionless governing equations have obtained using a commercial finite-element software package,FI- DAP.The solution has the following parameters: the Reynolds number,Re,the Prandtl number, P r,the ratio of the width of the lower surface A of the duct to the width of the upper surface A and the dimensionless radius of the bend Ri.Results are only presented for P r=0.7.Re values be- tween 3 and 300,A values between 1 and 1.5 and R_i values between 0.5 and 1.5 have been consid- ered.The effects of the governing parameters on the pressure losses,flow development lengths and heat transfer rates have been studied.