Šilumos atidavimo eksperimentinis tyrimas vertikaliame plokščiame kanale mišrios konvekcijos atveju priešingų krypčių tėkmėse pereinamojo tekėjimo zonoje 1. Vietinio šilumos atidavimo analizė.

We present results of an experimental investigation of local opposing mixed convection heat transfer in a vertical flat channel with symmetrical heating in the laminar-turbulent transition region. The experiments were performed in an airflow (p = 0.1, 0.15, 0.2 and 0.4 MPa) in the range Re from 2 ⋅ 103 to 5 ⋅ 104 and Grq up to 1.5 ⋅ 1010 at the limiting condition qw1 = qw2 = const. Numerical two-dimensional simulations were performed also for the same channel and for the same conditions as in experiments using the FLUENT 6.1 code. Experimental investigations show a sharp increase in heat transfer for the air pressure of 0.15 MPa up to Re &symph; 3 ⋅ 103, 0.2 MPa up to Re &symph; 4 ⋅ 103 and 0.4 MPa up to Re &symph; 8 ⋅ 103 in comparison to forced convection heat transfer. The numerical investigations revealed this intensification of heat transfer to be caused by the formation of vortices under the effect of buoyancy. Analysis of local heat transfer also shows that for some regimes there are regions with a vortex flow at the beginning of the heating, but due to the turbulization effect the non-vortical flow is prevailing along the channel. However, under a strong effect of buoyancy such vortices are dominating along the whole length of the channel. [ABSTRACT FROM AUTHOR]