ARE 346N Building Environmental Systems
Quiz 4 February 19, 2009
Closed book, closed notes
q = MCΔT+Mhfg for liquid water, C = 1 BTU/(lb ºF) 5 Questions
1. Name one disadvantage of using water as a heat transfer fluid in a heating system and one
disadvantage of using steam? 1 pt
Disadvantage of using water: _requires pumping, requires complex equipment for high
temperature systems,
Disadvantage of using steam: _bigger pipes, worse heat transfer, can require more complex
equipment for dealing with condensate
2. I lb of steam at 5 psig condenses and then cools to 202 ºF. How much heat energy does it give
off? 1 pt
q = MCΔT+Mhfg, q = 1 lb (1 BTU/lb ºF 25 ºF + 961 BTU/lb) = 986 BTU
3. What is the volume of the water at the end of the process above? 1 pt
V = M vf = 1 lb .0168 ft3/lb = 0.0168 ft3
4. What is an advantage and a disadvantage of using electricity to heat a building? 1 pt
advantages: simple equipment, doesn’t require venting
disadvantages: expensive, sensitive to power interruptions
5. Name any three of the components in a vapor compression cycle 1 pt
evaporator, compressor, condenser, expansion valve