Consider a small house (enclosure), 8” to the side, which contains an ice cube (1” to the side) at its
center. Wind blows by the house with outside convective coefficient ho = 6.0 Btu/hr ft2 F; the inside
convective coefficient hi = 1.5 Btu/hr ft2 F. The ground upon which the house rests is a perfect insulator,
so heat is transferred through the four walls and roof. The walls of the house are 1” thick. Which wall
materials will keep the ice cube frozen longer, ice or rigid foam (k = 0.015 Btu hr ft F)?
Solution:
Model of Ice House:
Assumptions:
1. All of ice in house walls will melt before the ice cube in the house melts.
2. Uniform heat transfer to four walls and roof; none through floor.
3. Ice starts at 32 ºF
4. House is exposed to 15 mph wind, as is ice cube when ice house melts.
5. Ice house has walls 1” thick.
6. Ice cube is 1” x 1” x 1”
7. Ambient Temperature is 70 ºF
Ground
Ice Cube at 32F
Enclosure
Wind at 70F
