ASHRAE Material Properties 2

Question 1

Which value is closest to the thermal conductivity of pure copper at room temperature?

Accepted Answer

About 400 W/m·K

Answer

Pure copper conducts about 400 W/m·K, roughly twice as well as aluminum (~205), which is why it is used for heat exchanger tubing.

Question 2

A radiant barrier works mainly because its surface has which property?

Accepted Answer

Low emissivity, around 0.05

Answer

Polished aluminum foil has an emissivity of about 0.03-0.05, so it gives off very little radiant heat across an air space.

Question 3

What is the approximate specific heat of liquid water in I-P units?

Accepted Answer

1.0 Btu/lb·°F

Answer

The Btu was originally defined from water, so water's specific heat is about 1.0 Btu/lb·°F.

Question 4

What is the approximate density of water at 60°F?

Accepted Answer

62.4 lb/ft³

Answer

Water at 60°F weighs about 62.4 lb/ft³, which is the same as about 8.34 lb/gal.

Question 5

Under the International Codes, what is the maximum vapor permeance of a Class I vapor retarder?

Accepted Answer

0.1 perm or less

Answer

Class I vapor retarders, such as polyethylene sheet, are rated at 0.1 perm or less.

ASHRAE - American Society of Heating, Refrigeration and Air Conditioning Engineers Certification Practice Test