Applying Conservation of MassThe small two-story office

Chapter 4, Problem 10P

(choose chapter or problem)

The small two-story office building shown in Fig. P4.10 has \(36,000 \mathrm{ft}^3\) of occupied space. Due to cracks around windows and outside doors, air leaks in on the windward side of the building and leaks out on the leeward side of the building. Outside air also enters the building when outer doors are opened. On a particular day, tests were conducted. The outdoor temperature was measured to be \(15^{\circ} \mathrm{F}\). The inside temperature was controlled at \(70^{\circ} \mathrm{F}\). Keeping the doors closed, the infiltration rate through the cracks was determined to be \(75 \mathrm{ft}^3 / \mathrm{min}\). The infiltration rate associated with door openings, averaged over the work day, was \(50 \mathrm{ft}^3 / \mathrm{min}\). The pressure difference was negligible between the inside and outside of the building. (a) Assuming ideal gas behavior, determine at steady state the volumetric flow rate of air exiting the building, in \(\mathrm{ft}^3 / \mathrm{min}\). (b) When expressed in terms of the volume of the occupied space, determine the number of building air changes per hour.