KNOWN: Variation of hx with x for laminar flow over a flat plate.
FIND: Ratio of average coefficient, h x , to local coefficient, hx, at x.
ANALYSIS: The average value of hx between 0 and x is
h x dx = x -1/2dx
KNOWN: Boundary conditions that change from specified heat flux to convection.
FIND: The finite difference equation for the node at the point where the boundary condition changes.
KNOWN: Dimensions of electronics package and finned nano-heat sink. Temperature and heat
transfer coefficient of coolant.
FIND: Maximum heat rate to maintain temperature below 85C for finned and un-finned packages.
D = 15 nm
KNOWN: Materials and dimensions of a composite wall separating a combustion gas from a
FIND: (a) Heat loss per unit area, and (b) Temperature distribution.
ASSUMPTIONS: (1) One-dimensional heat transfer, (2) Steady-
Midterm for ME 331
1. (20+5pts)Consider one-dimensional conduction in a plane composite wall. The outer surfaces
are exposed to a uid at 5C and a convection heat transfer coefcient of 1 OOOW/m2 - K .
The middle wall B experiences uniform h