Principles of Engineering

Thermodynamics

Thermodynamics - The study of thermal energy as it moves from one substance to another.

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British Thermal Unit (BTU) - The US Customary unit of thermal energy; the amount of energy needed to raise the temperature of one pound of pure water by one degree Fahrenheit.

Conduction - The transfer of heat energy by physical contact.

Convection - The transfer of heat energy by moving a heated substance from one place to another.

Radiation - Transfer of heat by temporarily transforming the heat into electromagnetic waves.

K - Value - A numeric expression of a material’s ability to conduct heat energy on a unit-thickness basis.

R-Value - A numeric expression of thermal insulation. R-values are the reciprocals of U-values.

U-Value - A numeric expression of a material’s thermal conductivity; the degree that heat energy can pass through a material.

Thermal or Heat Energy - Thermal energy is basically kinetic energy. It is the sum of the individual atoms’ kinetic energies. Even in a completely motionless object, the atoms from which the object is made are in constant motion and thus have thermal energy

• Heat Transfer

• 1st Law of Thermodynamics

Energy can be changed from one form to another, but it cannot be created or destroyed.

1st Law (closed system): Q - W = /\U   Q = heat transfer W = work /\U = m (u2 - u1)

1st Law (open system): Q - W = /\H   Q = heat transfer W = work /\H = m (h2 - h1)

• 2nd Law of Thermodynamics