Heat Units

Reference data and engineering information about heat units for thermodynamics applications.

heatunits

Overview

Engineering reference data for Heat Units in thermodynamics.

$\Delta U = Q - W$

Energy is conserved — heat added minus work done.

$PV = nRT$

Relates pressure, volume, and temperature of an ideal gas.

$Q = mc\Delta T$

Sensible heat transfer.

$\eta = 1 - T_C/T_H$

Maximum efficiency between two temperatures.

The following formulas express conversions between common heat units:

$1 \text{ BTU} = 1055.06 \text{ J} = 107.6 \text{ kpm} = 2.931 \times 10^{-4} \text{ kWh} = 0.252 \text{ kcal}$

$1 \text{ kcal} = 4186.8 \text{ J} = 426.9 \text{ kpm} = 1.163 \times 10^{-3} \text{ kWh} = 3.9683 \text{ BTU}$

$1 \text{ J} = 0.1020 \text{ kpm} = 2.778 \times 10^{-7} \text{ kWh} = 2.389 \times 10^{-4} \text{ kcal} = 9.478 \times 10^{-4} \text{ BTU}$

The calorie has several historical and specialized definitions. The most common are:

Thermochemical calorie
4 °C calorie
15 °C calorie
20 °C calorie
Mean calorie
International Steam Table calorie (1929)
International Steam Table calorie (1956)
IUNS calorie (Committee on Nomenclature of the International Union of Nutritional Sciences)

Note: The calorie unit is considered outdated for scientific purposes and has largely been replaced by the SI unit, the Joule.