Energy Transfer Equation
The energy transfered with a substance can be expressed as
Q = m cp dt (1)
where
Q = quantity of energy transferred (kJ, Btu)
m = mass of substance (kg, lb)
cp = specific heat of the substance (kJ/kgoC, kJ/kgoK, Btu/lb oF)
dt = temperature difference (rise or fall) in the substance (oC, K, oF)
Example - Energy Transfer with Water
2 kg of water is heated from 20oC to 60oC. The specific heat of water is 4.2 kJ/kgoC. The heat transfered can be calculated as
Q = (2 kg) (4.2 kJ/kgoC) ((60oC) - (20oC))
= 336 kJ
= (336 kWs) (1/3600 h/s)
= 0.093 kWh
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