Chemistry, 26.07.2019 20:00 Snowball080717

What is the formula for calculating the efficiency of a heat engine?

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Hi there,

Efficiency=. Work
——————-
Heat energy

We know that all the energy that is put into the engine has to come out either as work or waste heat. So work is equal to Heat at High temperature minus Heat rejected at Low temperature.

Answer from: nick607

The correct answer is $Efficiency= \frac{W}{Q_{H}}$ .

Explanation:

Heat engine: It is a device which converts the heat energy in to the mechanical work. In heat engine, the heat is transferred from high temperature reservoir to the low temperature reservoir.

It is just opposite of the refrigeration.

The expression of the work done is as follows;

$W=Q_{H}-Q_{C}$

Here, $Q_{H}$ is the heat added to the system and $Q_{C}$ is the heat rejected to the cold reservoir.

The formula for calculating the efficiency of a heat engine is as follows;

$Efficiency= \frac{W}{Q_{H}}$

Here, W is the work done and $Q_{H}$ is the heat added from the reservoir which is at high temperature and $Q_{C}$ is the heat rejected to the reservoir which is at low temperature.

Answer from: Quest

True, the standard unit for volume is liters which can be represented by either a lower case "l" or a capital "l"

Answer from: Quest

definition

entropy is a measure of the randomness or the extent of disorder of a chemical process.

enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

entropy is measured in joule per kelvin (jk⁻¹) whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.

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