PROBLEM $3.(20$ POINTS$)$

A factory has two zones. Zone $1$ and $2$ are both maintained at $75FdB.$ The design supply

air flow rates to Zone $1$ and $2$ are $3200$ and $2000$ CFM$,$ respectively. At a certain hour in

summer, the cooling loads for Zone $1$ and $2$ are $60,000Bt\frac{u}{h}r$ and $30,000Bt\frac{u}{h}r,$

respectively.

Assume dry air conditions and air density of $0\mathrm{.}075lb\frac{m}{f}{t}^3$

$($a$)$ If a single$-$duct constant$-$volume system with local reheat boxes is used with

discriminator control, what would the required amount of reheat $(Bt\frac{u}{h}r)$ to be provided in

each zone at the hour?

The design cold air supply temperatures are $55FdB.$

$($b$)$ If a VAV system with $20\%$ minimum position is used with discriminator control, what

would the required amount of reheat $(Bt\frac{u}{h}r)$ be provided by a reheater in each zone at the

hour? The design supply air temperature is $55FDB.$