# British Thermal Unit (unit BTU) – Energy Unit

Energy is generally defined as the potential to do work or produce heat. This definition causes the SI unit for energy to be the same as the unit of work – the joule (J). Joule is a derived unit of energy, and it is named in honor of James Prescott Joule and his experiments on the mechanical equivalent of heat. In more fundamental terms, 1 joule is equal to:

1 J = 1 kg.m2/s2

Since energy is a fundamental physical quantity and is used in various physical and engineering branches, there are many energy units in physics and engineering.

## British Thermal Unit (unit: BTU)

British Thermal Unit (unit: BTU).  British Thermal Unit is a traditional unit of heat. It is part of the British Imperial system of units. It is defined as the amount of heat that must be absorbed by 1 pound of water to raise its temperature by 1 °F at the temperature that water has its greatest density (approximately 39 degrees Fahrenheit). Its counterpart in the International System of Units (SI) is the calorie, defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius.

• 1 British Thermal Unit (BTU) = 1055 J
• 1 British Thermal Unit (BTU) = 252 calories
• 1 British Thermal Unit (BTU) = 0.000293 kWh

References:
Reactor Physics and Thermal Hydraulics:
1. J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).
2. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.
3. W. M. Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1.
4. Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317
5. Todreas Neil E., Kazimi Mujid S. Nuclear Systems Volume I: Thermal Hydraulic Fundamentals, Second Edition. CRC Press; 2 edition, 2012, ISBN: 978-0415802871
6. Zohuri B., McDaniel P. Thermodynamics in Nuclear Power Plant Systems. Springer; 2015, ISBN: 978-3-319-13419-2
7. Moran Michal J., Shapiro Howard N. Fundamentals of Engineering Thermodynamics, Fifth Edition, John Wiley & Sons, 2006, ISBN: 978-0-470-03037-0
8. Kleinstreuer C. Modern Fluid Dynamics. Springer, 2010, ISBN 978-1-4020-8670-0.
9. U.S. Department of Energy, THERMODYNAMICS, HEAT TRANSFER, AND FLUID FLOW. DOE Fundamentals Handbook, Volume 1, 2, and 3. June 1992.

Energy