Book Mechanical and Engineering Systems in Architecture Engi

Book: Mechanical and Engineering Systems in Architecture, Engineering, and Construction

Question: (Ch. 9 #13. part B) a 2(1/4)\"x5\"x24 gauge-1(1/4)\" steel tube convector (Tb. 9.1) has an output of 860 btu/hr per foot of tube at a fluid tempeature of 200 degrees F. A classroom in an elementary school has a heating load of 17,850 btu/hr.

at a flow rate of 1gal/min (8.3lb/min), determine what the tempeature of the water leaving the convector, if water enters at a tempeature of 200 degrees F

Solution

Solution:

Specific heat capacity of water = 1 Btu/lbm-F.

Energy balance equation for steel tube convector: (Assuming that the convector can provide the exact the heat load requirement for the class room in elementary school.)

So, m_w X C_p X (T - 200) = 17850/60 [m_w is the mass flow rate of water in the convector]

Or, 8.3 X 1 X (T - 200) = 297.5 [ T is the exit temperature of water in F]

Or, T = 235.84 F

The temperature of the water leaving the convector is 235.84 F.