Consider an electrically heated brick house (k = 0.40 Btu/h·ft·°F) whose walls are 9 ft high and 1 ft thick. Two of the walls of the house are 50 ft long and the others are 35 ft long. The house is maintained at 70°F at all times while the temperature of the outdoors varies. On a certain day, the temperature of the inner surface of the walls is measured to be at 55°F while the average temperature of the outer surface is observed to remain at 45°F during the day for 10 h and at 35°F at night for 14 h. Determine the amount of heat lost from the house that day. Also determine the cost of that heat loss to the home owner for an electricity price of $0.09/kWh.
Energy transfer
The flow of energy from one region to another region is referred to as energy transfer. Since energy is quantitative; it must be transferred to a body or a material to work or to heat the system.
Molar Specific Heat
Heat capacity is the amount of heat energy absorbed or released by a chemical substance per the change in temperature of that substance. The change in heat is also called enthalpy. The SI unit of heat capacity is Joules per Kelvin, which is (J K-1)
Thermal Properties of Matter
Thermal energy is described as one of the form of heat energy which flows from one body of higher temperature to the other with the lower temperature when these two bodies are placed in contact to each other. Heat is described as the form of energy which is transferred between the two systems or in between the systems and their surrounding by the virtue of difference in temperature. Calorimetry is that branch of science which helps in measuring the changes which are taking place in the heat energy of a given body.
Consider an electrically heated brick house (k =
0.40 Btu/h·ft·°F) whose walls are 9 ft high and 1 ft thick.
Two of the walls of the house are 50 ft long and the others
are 35 ft long. The house is maintained at 70°F at all
times while the temperature of the outdoors varies. On a certain
day, the temperature of the inner surface of the walls is
measured to be at 55°F while the average temperature of the
outer surface is observed to remain at 45°F during the day
for 10 h and at 35°F at night for 14 h. Determine the amount
of heat lost from the house that day. Also determine the cost
of that heat loss to the home owner for an electricity price of
$0.09/kWh.
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