A 30-L electrical radiator containing heating oil is placed in a well-sealed 50-m3 room. Both the air in the room and the oil in the radiator are initially at the environment temperature of 10°C. Electricity with a rating of 1.8 kW is now turned on. Heat is also lost from the room at an average rate of 0.35 kW. The heater is turned off after some time when the temperatures of the room air and oil are measured to be 20°C and 50°C, respectively. Taking the density and the specific heat of oil to be 950 kg/m3 and 2.2 kJ/kg = °C, determine (a) how long the heater is kept on, (b) the energy destruction, and (c) the second-law efficiency for this process.

Transcribed Image Text:

Room 10°C Radiator