1. (2 pts) Short-answer and Multiple-choice Problems

A. When Bi << 1, which of the following is approximately true for the temperature, 7, of the object

being transiently cooled? Explain your reasoning.

a.

T = f(t) only

b. T = f(t) and one spatial dimension

c. T = f(t, x,y,z)

B. Consider a plate of material X, originally at To, that is exposed to fluid at T

heat-transfer coefficient h at time t = 0. If the plate is now replaced with material Y with a higher

thermal conductivity but the same plate size and given heat-transfer coefficient, how will the time

for the center of the plate to cool to a given value change with the new material Y?

C. Cite two reasons that insulation is used for chemical engineering process equipment.

D. Consider a hot oven with an insulated door exposed to a cold room. If the room temperature was

increased but all other variables were not changed, would

(i) the heat loss to the room increase, decrease, or not change?

(ii) the temperature of the outside surface of the door increase, decrease or not change?

Explain your reasoning.