Heat engines, including internal combustion engines and external combustion engines ( such as steam engines ) burn a fuel to create heat which is then used to create motion.

Heat engines distinguish themselves from other types of engines by the fact that their efficiency is fundamentally limited by Carnot's theorem .< ref > Thermal physics: entropy and free energies, by Joon Chang Lee ( 2002 ), Appendix A, p. 183: " A heat engine absorbs energy from a heat source and then converts it into work for us.

Heat engines are often confused with the cycles they attempt to mimic.

* Heat engine for a view of the thermodynamics involved in these engines.

Heat haze refers to the distortive effect experienced when viewing objects through a layer of heated air, for example across hot asphalt or through the exhaust gases produced by jet engines.

This may cause a problem where it's cheaper to buy electricity than to burn fuel, therefore many engines are used in CHP ( Combined Heat and Power ) configurations that can be small enough to be integrated into portable container configurations.

Heat engines are able to convert thermal energy in the form of a temperature gradient between a hot source and a cold sink into other desirable mechanical work.

Heat engines generate mechanical power by extracting energy from heat flows, much as a water wheel extracts mechanical power from a flow of mass falling through a distance.

Heat engines, including Stirling engines, are sealed machines using pistons within cylinders to transfer energy from a heat source to a colder reservoir, often using steam or another gas as the working substance.

" Heat Riser ".... now obsolete, earlier manifolds ... with ' wet runners ' for carbureted engines ... used exhaust gas diversion through the intake manifold to provide vaporizing heat.

* Heat engines, such as the internal combustion engine used in cars, or the steam engine ( Heat → Mechanical energy )

Heat recycling, cogeneration and solar pre-heating can save 50-75 % of the gas otherwise used.

Efficiencies can be as high as 65 % when the fuel cell is paired with a turbine, and 85 % if heat is captured and used in a Combined Heat and Power ( CHP ) system.

Heat can improve gemstone color or clarity.

Heat treatment processes such as quenching and tempering can significantly change these properties however.

Some such proteins are highly specific in their function, such as protein disulfide isomerase ; others are very general and can be of assistance to most globular proteins-the prokaryotic GroEL / GroES system and the homologous eukaryotic Heat shock proteins Hsp60 / Hsp10 system fall into this category.

The statement that ƒ can be reconstructed from ƒ ̂ is known as the Fourier integral theorem, and was first introduced in Fourier's Analytical Theory of Heat,, although what would be considered a proof by modern standards was not given until much later.

Heat can also be provided electrically by resistive heating, in which conductive filaments are heated by the passage of electricity.

Heat pumps can extract heat from the air or suck heat from the ground.

Heat can be removed through radiation, convection, and by heat pump systems through a process called the refrigeration cycle.

Heat transfer to atmosphere can be aided by incorporating cooling fins onto the drum.

Heat and agitation can be applied to the bath to speed the etching rate.

Heat gain can occur through a sunspace, solarium or solar closet.

Heat pumps can move thermal energy in a direction which is opposite to the direction of spontaneous heat flow.

Heat pumps can move thermal energy against a thermal gradient at the expense of an external source of power, usually a mechanical compressor.

Heat waves can often have severe effects upon the landscape, causing famine, destruction of vegetation, and possible deaths to livestock and wildlife.

Heat waves can happen anytime from June through September and feature many days above 90 and even some above 100, although the ocean moderates the temperatures some.

Heat indexes can soar during the summer months due to high humidity and long hours of sunshine, causing a 93 degree day to feel as if it were 101 degrees.

His formulation of the second law, which was published in German in 1854, is known as the Clausius statement: " Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time.

Heat index values can consistently reach over 100 ° F from May through September.

Heat transfer by thermal radiation may be minimized by silvering flask surfaces facing the gap, but can become problematic if the flask's contents or surroundings are very hot ; hence vacuum flasks usually hold contents below water's boiling point.

Ethanol BTUs can be compared with gasoline BTUs in Heat of combustion tables.

Upon rearrangement the thermal efficiency can be obtained ( Net Work / Heat added ):

Heat pipes can be used to improve conductivity.

In 1865, the German physicist Rudolf Clausius, in his Mechanical Theory of Heat, suggested that the principles of thermochemistry, e. g. the heat evolved in combustion reactions, could be applied to the principles of thermodynamics.

Heat generated by electronic circuitry must be dissipated to prevent immediate failure and improve long term reliability.

Film noir encompasses a range of plots: the central figure may be a private eye ( The Big Sleep ), a plainclothes policeman ( The Big Heat ), an aging boxer ( The Set-Up ), a hapless grifter ( Night and the City ), a law-abiding citizen lured into a life of crime ( Gun Crazy ), or simply a victim of circumstance ( D. O. A .).

Heat pumps may use the heat output of the refrigeration process, and also may be designed to be reversible, but are otherwise similar to refrigeration units.

# Water and appropriate sports drinks should be used for rehydration as outlined in the NFHS Document “ Position Statement and Recommendations for Hydration to Minimize the Risk for Dehydration and Heat Illness ”.

Heat lightning is a common name for a lightning flash that appears to produce no discernable thunder because it occurs too far away for the thunder to be heard.

Heat pump installations may be installed alongside an auxiliary conventional heat source such as electrical resistance heaters, or oil or gas combustion.

Heat exchangers are expensive, requiring drilling for some heat-pump types or large spaces to be efficient, and the heat pump industry generally competes on price rather than efficiency.

Both picks flopped, as the Heat tried to turn Burton, a college small forward, into a shooting guard without much success and Kessler was bogged by injury problems and was not physical enough to be a quality NBA power forward.

In the wake of Rothstein's resignation prior to the 1991 – 92 season, the Heat hired Kevin Loughery, who had 29 years of experience in the NBA both as a coach and a player, to be their new head coach.

Setting the tone for a new era of Heat basketball, Arison hired Pat Riley to be the new head coach and team president of the Miami Heat ; Riley resigned as coach of the New York Knicks immediately following the 1994 – 1995 season.

Shortly thereafter, Randy Pfund, Riley's former assistant on the Los Angeles Lakers, was brought in to be the Executive Vice President of the Miami Heat.