# Define Indicated Thermal Efficiency Wonderfully

**Since it is dimensionless number we must always express w q.**

**Define indicated thermal efficiency**. The thermal efficiency ηth represents the fraction of heat qh that is converted to work. This is because kilowatt hour is often used when referring to electrical energy and joule or btu. For a heat engine thermal efficiency is the fraction of the energy added by heat primary energy that is converted to net work output secondary energy.

In the case of a refrigeration or heat pump cycle thermal efficiency is the ratio of net heat output for heating or removal for cooling to energy input the coefficient of performance. Is calorific value of fuel in kj sec indicated power is power developed inside cylinder. In si units it is joule per joule but often also expressed as joule kilowatt hour or british thermal units kwh.

The thermal efficiency is represented by the symbol and can be calculated using the equation. The thermal efficiency expresses the fraction of heat that becomes useful work. Brake thermal efficiency η bth brake thermal efficiency can be defined as the ratio of brake power bp to input fuel energy in appropriate units.

The term efficiency is a dimensionless measure sometimes quoted in percent and strictly heat rate is dimensionless as well but often written as energy per energy in relevant units. Indicated thermal efficiency indicated power mf c. It is a dimensionless performance measure of a heat engine that uses thermal energy such as a steam turbine an internal combustion engine or a refrigerator.

An initial appraisal of the engine thermal efficiency at full load capacity indicates a heat to power ratio of 1 56 1 representing a thermal efficiency of 39 1 when calculated on the saturated lower calorific value of the fuel 32 9 mj m 3 39 1 mj m 3 dry gross saturated lower calorific value. V mf is fuel oil supplied kg sec c. η ith ip kj s energy in fuel per second kj s indicated power is defined as the sum of friction power and brake power.

Indicated thermal efficiency ηi. When the engine is operating at part load the gross thermal efficiency falls to approximately 28 9 at 22 load rating. Is is a ratio of heat equivalent of indicated power per unit time to heat supplied to the engine in unit time.