Efficiency with which a power source transforms the potential heat of its fuel into work or output, expressed as a ratio of the useful work done by the power source in a given time interval to the total heat energy contained in the fuel burned during the same time interval, both work and heat being expressed in the same units.
1. Same as thermodynamic efficiency. 2. In climatology, an expression of the effectiveness of temperature in determining the rate of growth, assuming sufficient moisture. The idea was introduced by B. E. and G. J. Livingston (1913). It was applied by C. W. Thornthwaite (1948) in his system of climatic classification. The recognition of this general concept led to one of the first uses of the degree-day, that is, application to plant growth and relationship to the phenological effective temperature of about 42°F. Compare precipitation effectiveness. Livingston, B. E., and G. J. Livingston, 1913: Temperature coefficients in plant geography and climatology. Botanical Gazette, 56, 349–375. Thornthwaite, C. W., 1948: An approach toward a rational classification of climate. Geogr. Review, 38, 55– 94.
The efficiency of a boiler, based on the ratio of heat absorbed to total heat input. This does not include heat loss from the boiler shell.
Quantity of heat produced in relation to fuel input
ratio of the work done to the heat input (see equation 13.3)
The thermal efficiency of a cycle is defined as the ratio of net work output to the heat supplied at high temperature.
Ability to transfer and absorb heat from fuel sources into the water.
of an engine, is the ratio of work done by the engine to the available heat energy in the fuel consumed; for steam reciprocating engines, this may range from 11 to 13.5 per cent while diesel engines from 35 to 41.5 per cent, according to whether waste heat boilers are used
The thermal efficiency of a system is directly analogous to the normal efficiency, being the thermal output of the system compared to the energy input.
the rate at which heat exchange surfaces transfer heat to the transfer medium (e.g., air to water or water or air). It is typically measured as the ratio of BTU output of hot water to BTU input of fuel. Types of heat movement that impact thermal efficiency: Conductive/Convective heating surfaces – also referred to as secondary or indirect heating surfaces including all surfaces exposed only to hot combustion gases. Radiant heating surfaces – also called direct or primary heating surfaces and consist of heat exchanger surfaces directly exposed to radiant heat from the flame. Radiant heat transfer is tremendously more effective than conductive/convective heat transfer and, contrary to commonly accepted belief, is where most of the heat transfer occurs in a boiler, furnace or forced air system.
A measure of the efficiency of converting a fuel to energy and useful work; useful work and energy output divided by higher heating value of input fuel times 100 (for percent).
The thermal efficiency (\eta_{th} \,) is a dimensionless performance measure of a thermal device such as an internal combustion engine, a boiler, or a furnace, for example. The input, Q_{in} \,, to the device is heat, or the heat-content of a fuel that is consumed. The desired output is mechanical work, W_{out} \,, or heat, Q_{out} \,, or possibly both.
