Natural Convection Heat Transfer from Vertical Parallel Plates to Air

Two-dimensional Navier-Stokes and energy equations are numerically solved for laminar natural convection of air between vertical parallel plane plates with uniform heat flux. Calculations are carried out under the conditions of the modified Grashof number (2.3×10^3≦Gr*≦8.8×10^5), and heighttoplate spacingratio (8≦l/h≦30), which cover the practical range encountered with the natural air cooling system of an electronic equipment. The numerical solutions are compared with present experimental results. The local Nusselt numbers and induced flow rates obtained numerically agree well with those measured. A correlation expression for the local Nusselt number is proposed which can predict the local plate temperature within 5% error. When the value of dimensionless variable Φ={(h/x)Gr*Pr}/{(h/l)Gr*Pr}^<1/2> is greater than about 10^2,the existing results based on the boundary layer approximation are found to be not applicable for predicting the maximum plate temperature