heat transfer problem

MECE 4364 Mid-term Exam 1 October 26, 2016

Name:

1. (30) In a manufacturing process two identical thin transparent films are being bonded together

as shown below. A very thin layer of thermal glue is inserted at the interface between the films. To cure the bond at 400K, a continuous laser beam provides a heat flux all of which is absorbed

by the glue. The top and bottom surfaces are exposed to air at T∞=300K with a convection heat transfer coefficient h-5 W/m2K. The density, thermal conductivity and specific heat of the film are ρ=1000 kg/m3, k=0.1 W/mK and c=500 J/kgK respectively. Neglect the thermal resistance and heat capacity of the glue layer.

(a) In a steady state process calculate the required laser power q” (W/m2). (b) Estimate the time tc taken for the film at the glue interface to cool down to 310 K after

turning off the laser at t=0. (c) If the film thickness increases to 5mm what would be the new time tc taken for the film

to cool down to 310 K after turning off the laser at t=0. (d) Draw the 1D transient temperature distribution for case (b) and (c).

L=0.5 mm

L=0.5 mm

Laser Irradiation

Ai r

Ai r

MECE 4364 Mid-term Exam 1 October 26, 2016

Name:

MECE 4364 Mid-term Exam 1 October 26, 2016

Name: