Question 11.CSGP.179c: A refrigerator in a meat warehouse must keep a low temperatu......
A refrigerator in a meat warehouse must keep a low temperature of -15°C and the outside temperature is 20°C. It uses R-12 as the refrigerant which must remove 5 kW from the cold space. Find the flow rate of the R-12 needed assuming a standard vapor compression refrigeration cycle with a condenser at 20°C.
Basic refrigeration cycle: T _1= T _4=-15^{\circ} C , \quad T _3=20^{\circ} C
Computer Tables: h _4= h _3=54.87 \,kJ / kg ; \quad h _1= h _{ g }=180.97 \,kJ / kg
\begin{aligned}& \dot{ Q }_{ L }=\dot{ m }_{ R -12} \times q _{ L }=\dot{ m }_{ R -12}\left( h _1- h _4\right) \\& q _{ L }=180.97-54.87=126.1 \,kJ / kg \\& \dot{ m }_{ R -12}=5.0 / 126.1= 0 . 0 3 9 6 5 \,k g / s\end{aligned}
Ideal refrigeration cycle
\begin{aligned}& T _{\text {cond }}=20^{\circ} C \\& T _{\text {evap }}=-15^{\circ} C = T _1\end{aligned}
