Cy. Choi et Sj. Kim, CONJUGATE MIXED CONVECTION IN A CHANNEL - MODIFIED 5 PERCENT DEVIATION RULE, International journal of heat and mass transfer, 39(6), 1996, pp. 1223-1234
Three dimensional conjugate mixed convection in a rectangular channel
is numerically investigated. The focus is on the effects of local buoy
ancy generated by a discrete heat source mounted on a thermally conduc
ting board. Calculations cover 0.126 less than or equal to Re less tha
n or equal to 1260, Gr = 7.8789 x 10(7), 1 less than or equal to kappa
less than or equal to 100, and Pr = 0.71, respectively. Flow fields s
how active interaction between the buoyancy-induced thermal plume and
the approaching external flow in the mixed convection regime where the
temperature distribution, heat flux, and heat transfer coefficients a
ll strongly depend on such flow interaction. In addition, the Nusselt
number on top of the heat source indicates significant three-dimension
al effects. The 'modified 5% deviation rule' is proposed in an effort
to define the natural, mixed and forced convection regimes. The propos
ed rule is especially appropriate for conjugate heat transfer problems
in which the thermal conductivity of the board plays an important rol
e in determining the heat transfer mode. A correlation for theta(max)/
kappa(1/2) is sought, and the mixed convection regime is accordingly d
etermined as 1.81 x 10(-3) less than or equal to Re/Gr(1/2) < 2.80 x 1
0(-2).