Fundamentals of Engineering $($FE$)$ Exam Problems

$6-159$ Consider a Carnot refrigerator and a Carnot heat pump operating between the same two thermal energy reservoirs. If the COP of the refrigerator is $3\mathrm{.}4,$ the COP of the heat pump is

$($a$)1\mathrm{.}7$

$($b$)2\mathrm{.}4$

$($c$)3\mathrm{.}4$

$($d$)4\mathrm{.}4$

$($e$)5\mathrm{.}0$

$6-160$ A $2\mathrm{.}4-$m$-$high $200-m^2$ house is maintained at $22C$ by an air$-$conditioning system whose COP is $3\mathrm{.}2.$ It is estimated that the kitchen, bath, and other ventilating fans of the house discharge a houseful of conditioned air once every hour. If the average outdoor temperature is $32C,$ the density of air is $1\mathrm{.}20k\frac{g}{m^3},$ and the unit cost of electricity is $$\frac{0\mathrm{.}10}{k}Wh,$ the amount of money "vented out" by the fans in $10$ hours is

$($a$)$ $$0\mathrm{.}50$

$($b$)$ $$1\mathrm{.}6$

$($c$)$ $$5\mathrm{.}0$

$($d$)$ $$11\mathrm{.}0$

$($e$)$ $$16\mathrm{.}0$

$6-161$ A window air conditioner that consumes $1$ kW of electricity when running and has a coefficient of performance of $3$ is placed in the middle of a room and is plugged in$.$ The rate of cooling or heating this air conditioner will provide to the air in the room when running is

$($a$)3k\frac{J}{s},$ cooling

$($b$)1k\frac{J}{s},$ cooling

$($c$)0\mathrm{.}33k\frac{J}{s},$ heating

$($d$)1k\frac{J}{s},$ heating

$($e$)3k\frac{J}{s},$ heating

$6-162$ The drinking water needs of an office are met by cooling tap water in a refrigerated water fountain from $23$ to $6C$ at an average rate of $18k\frac{g}{h}.$ If the COP of this refrigerator is $3\mathrm{.}1,$ the required power input to this refrigerator is

$($a$)1100$ W

$($b$)355$ W

$($c$)195$ W

$($d$)115$ W

$($e$)35$ W