ASHRAE Material Properties 4

Question 1

How does adding propylene glycol to a hydronic water loop change the fluid's properties?

Accepted Answer

Specific heat goes down and viscosity goes up

Answer

Glycol mixtures carry less heat per pound and are thicker, so you need more flow and more pump head for the same capacity.

Question 2

Low-e coatings on glazing mainly improve performance by changing which surface property?

Accepted Answer

They lower long-wave infrared emissivity

Answer

Low-e coatings cut radiant heat transfer across the glazing cavity, which lowers the U-factor.

Question 3

Which material gives a building the most thermal mass per unit volume?

Accepted Answer

Normal-weight concrete

Answer

Normal-weight concrete is dense (~140-150 lb/ft³), so it stores far more heat per unit volume than wood or insulation.

Question 4

Why is a dielectric union installed where copper pipe connects to steel pipe?

Accepted Answer

To prevent galvanic corrosion between dissimilar metals

Answer

Copper and steel are far apart on the galvanic series, so an electrical break is needed to keep the steel from corroding when the two are joined in water.

Question 5

Fibrous and cellular insulations work mainly by taking advantage of which property?

Accepted Answer

The low thermal conductivity of trapped still air or gas

Answer

Still air conducts only about 0.025 W/m·K, and insulation keeps that air from moving, which stops convection.

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

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

ASHRAE Material Properties 4