Chapter 1, Problem 1.47P

Consider a carton of milk that is refrigerated at a temperature of $T_m=5°\text{C}$ . The kitchen temperature on a hotsummer day is $T_{\infty }=30°\text{C}$ . If the tour sides of the cartonare of height and width $L=200\text{mm}$ and $w=100\text{mm}$ , respectively, determine the heat transferred to the milkcarton as it sits on the kitchen counter for durations of $t=10s,60s,$ and 3(X) s before it is returned to the refrigerator. The convection coefficient associated withnatural convection on the sides of the cartonis $h=10\text{W}/{\text{m}}^{\text{2}}\cdot \text{K}$ . The surface emissivity is 0.90. Assume themilk carton temperature remains at 5°C during theprocess. Your parents have taught you the importance ofrefrigerating certain foods from the food safety perspective. Comment on the importance of quickly returningthe milk carton to the refrigerator from an energy coneservation point of view.