Heat is a form of energy that flows from a higher temperature object to a lower temperature object. It's a fundamental concept in thermodynamics and thermal engineering.
Common applications include:
- Thermal engineering and heat transfer analysis
- HVAC system design and energy efficiency
- Food science and cooking processes
- Chemical engineering and process design
- Power generation and energy systems
Common heat energy values:
- Boiling 1 liter of water: ~2,260 kJ
- Daily human energy needs: ~8,400 kJ (2,000 kcal)
- 1 kWh of electricity: 3,600 kJ
- 1 gallon of gasoline: ~131,000 kJ
Conversion examples:
- 1 J = 0.000948 BTU = 0.239 cal
- 1 BTU = 1,055.06 J = 252 cal
- 1 cal = 4.184 J = 0.00397 BTU
- 1 kWh = 3,600,000 J = 3,412 BTU
Common Conversions
Unit Definitions
Joules (J)
The SI unit of energy and heat
Formula: 1 J = 1 N × 1 m
British Thermal Units (BTU)
Imperial unit of heat energy
Formula: 1 BTU = 1,055.06 J
Calories (cal)
Amount of energy to raise 1g water by 1°C
Formula: 1 cal = 4.184 J
Kilocalories (kcal)
Large calorie unit for food energy
Formula: 1 kcal = 4,184 J
Electron Volts (eV)
Atomic energy unit
Formula: 1 eV = 1.60218 × 10⁻¹⁹ J
Ergs (erg)
CGS unit of energy
Formula: 1 erg = 10⁻⁷ J
Foot-pounds (ft⋅lb)
Imperial unit of mechanical energy
Formula: 1 ft⋅lb = 1.35582 J
Watt-hours (Wh)
Electrical energy unit
Formula: 1 Wh = 3,600 J
Kilowatt-hours (kWh)
Large electrical energy unit
Formula: 1 kWh = 3,600,000 J
Therms (therm)
Natural gas energy unit
Formula: 1 therm = 100,000 BTU = 105,505,585.262 J