Ahousehold refrigerator that has a power input of 450 w and a cop of 1.5 is to cool five large watermelons, 10 kg each, to 8°c. if the watermelons are initially at 28°c, determine how long it will take for the refrigerator to cool them? the watermelons can be treated as water whose specific heat is 4.2 kj/kg·°c. is your answer realistic or optimistic?

Determine the time of the day and month of the year at which the peak sensible cooling load occurs for a top floor, north-eastern corner room of an office building in durban for the following conditions: floor area: 8 x 8 x 3 m east and north walls: 115 mm face brick (outside), 20 mm air space, 115 mm ordinary brick (inside) with 15 mm plaster roof construction: suspended plasterboard ceiling, 450 mm air space, 150 mm concrete, 75mm screed, waterproofing no heat transfer across other surfaces window area 3x 1,5 m high in north wall only. ordinary glass with venetian blinds. lights and occupants : from 07: 00 to 18: 00 average light density: 25 w/m2 number of occupants : 5 seated, light office work room temperature 24°c