1.47 Consider a carton of milk that is refrigerated at a tem- perature of Tm = 5°C. The kitchen temperature on a hot summer day is T00 = 30°C. If the four sides of the carton are of height and width L = 200 mm and w = 100 mm, respectively, determine the heat transferred to the milk carton as it sits on the kitchen counter for durations of t = 10 s, 60 s, and 300 s before it is returned to the refrigerator. The convection coefficient associated with natural convection on the sides of the carton is h = 10
W/m2 · K. The surface emissivity is 0.90. Assume the milk carton temperature remains at 5°C during the process. Your parents have taught you the importance of refrigerating certain foods from the food safety perspec- tive. Comment on the importance of quickly returning the milk carton to the refrigerator from an energy con- servation point of view.