An office with 25x25 ft2 floor area and 12 ft ceiling high in a large building has a large south envelope with 50% area for a R30 (30 ft2-h-oF/Btu) wall and 50% area for a R2 (2 ft2-h-oF/Btu) glass window. Assuming the indoor and outdoor h(C+R) are, respectively, 2 and 5 Btu/(ft2-h-oF). The ceiling, floor and other walls are next to rooms of similar conditions (and thus can be assumed adiabatic).

[air density: 0.075 lb/ft3; specific heat: 0.24 Btu/lb*oF]

1. a) If outdoor air temperature is (-1) oF, disregarding any solar impact and there is no

   heating/cooling device inside, what is the ultimate indoor air temperature if the internal

   heat load is 1000 Btu/h? How much heat is lost through the window?

2. b) If the ceiling diffuser is supplying 100% fresh warm air at a flow rate of 0.5 ACH and

   Tsupply=(89) oF. There is no return duct in the room and the room air is released through exfiltration and the room is perfectly mixed, what is the ultimate indoor air temperature if the internal heat load is 1000 Btu/h?

3. c) Check the given sun path diagram, find the sunrise time and solar altitude angle at the

   th solar noon of Jan 27 .

   th

4. d) At solar noon of Jan 27 , if the direct normal irradiance (i.e., direct beam solar on a

   2 surface normal to the sun) is (49) Btu/h-ft , only consider the solar normally

   transmitted through the window and the transmittance of the glass is 0.9, calculate the indoor air temperature when considering this passive solar heat gain (with 1000 Btu/h internal load but without supply warm air from ceiling).