Thermal efficiency - Revision history

Jmdonev: 1 revision imported

2018-05-18T22:53:15Z

1 revision imported

← Older revision	Revision as of 22:53, 18 May 2018
(No difference)

Jmdonev at 19:21, 18 May 2018

2018-05-18T19:21:53Z

← Older revision		Revision as of 19:21, 18 May 2018
Line 1:		Line 1:
	~~[[category:371 topics]]~~		[[Category:Done 2018-05-18]]
	[[Category:Done ~~2015~~-09-~~06]]~~
	~~[[category:301 topics]]~~
	~~[[Category:waiting for simulation~~]]
	[[File:Flow Chart thing.png\|340px\|thumbnail\|Figure 1: The amount of work output for a given amount of heat gives a system its thermal efficiency.<ref>This picture was made by the Energy Education team.</ref>]]		[[File:Flow Chart thing.png\|340px\|thumbnail\|Figure 1: The amount of work output for a given amount of heat gives a system its thermal efficiency.<ref>This picture was made by the Energy Education team.</ref>]]
	<onlyinclude>The '''thermal efficiency''' of ~~a [[~~heat ~~engine]] is the amount of~~ useful [[work~~]] an engine can do based on the amount of [[heat]] input~~.</onlyinclude> The thermal efficiency is represented by the symbol <m>\eta</m>, and ~~given by~~ the equation		<onlyinclude>[[Heat engine]]s turn [[heat]] into [[work]]. The '''thermal efficiency''' expresses the fraction of heat that becomes useful work.</onlyinclude> The thermal efficiency is represented by the symbol <math>\eta</math>, and can be calculated using the equation:

	<center><m>\eta=\frac{W}{Q_H}</m></center>		<center><math>\eta=\frac{W}{Q_H}</math></center>

	Where:		Where:

	<m>W</m> is the useful work and		<math>W</math> is the useful work and

	<m>Q_H</m> is the total heat energy input from the hot source.</onlyinclude><ref>TPUB Engine Mechanics. (April 4, 2015). ''Thermal Efficiency'' [Online]. Available: http://enginemechanics.tpub.com/14075/css/14075_141.htm</ref>		<math>Q_H</math> is the total heat energy input from the hot source.</onlyinclude><ref>TPUB Engine Mechanics. (April 4, 2015). ''Thermal Efficiency'' [Online]. Available: http://enginemechanics.tpub.com/14075/css/14075_141.htm</ref>

	Heat engines often operate at around 30% to 50% efficiency, due to practical limitations. It is impossible for heat engines to achieve 100% thermal efficiency (<m>\eta = 1</m>) according to the [[Second law of thermodynamics]]. This is impossible because some [[waste heat]] is always produced produced in a heat engine, shown in Figure 1 by the <m>Q_L</m> term. Although complete efficiency in a heat engine is impossible, there are many ways to [[Waste heat#Harnessing waste heat\|increase a system's overall efficiency]].		Heat engines often operate at around 30% to 50% efficiency, due to practical limitations. It is impossible for heat engines to achieve 100% thermal efficiency (<math>\eta = 1</math>) according to the [[Second law of thermodynamics]]. This is impossible because some [[waste heat]] is always produced produced in a heat engine, shown in Figure 1 by the <math>Q_L</math> term. Although complete efficiency in a heat engine is impossible, there are many ways to [[Waste heat#Harnessing waste heat\|increase a system's overall efficiency]].

	===An Example===		===An Example===
	If 200 [[joule]]s of [[thermal energy]] as heat is input (<m>Q_H</m>), and the engine does 80 J of work (<m>W</m>), then the efficiency is 80J/200J, which is 40% efficient.		If 200 [[joule]]s of [[thermal energy]] as heat is input (<math>Q_H</math>), and the engine does 80 J of work (<math>W</math>), then the efficiency is 80J/200J, which is 40% efficient.

	This same result can be gained by measuring the waste heat of the engine. For example, if 200 J is put into the engine, and observe 120 J of waste heat, then 80 J of work must have been done, giving 40% efficiency.		This same result can be gained by measuring the waste heat of the engine. For example, if 200 J is put into the engine, and observe 120 J of waste heat, then 80 J of work must have been done, giving 40% efficiency.
Line 25:		Line 22:
	There is a maximum attainable efficiency of a heat engine which was derived by physicist Sadi Carnot. Following laws of [[thermodynamics]] the equation for this turns out to be		There is a maximum attainable efficiency of a heat engine which was derived by physicist Sadi Carnot. Following laws of [[thermodynamics]] the equation for this turns out to be

	<center><m>\eta_{max}=1 - \frac{T_L}{T_H}</m></center>		<center><math>\eta_{max}=1 - \frac{T_L}{T_H}</math></center>

	Where		Where

	<m>T_L</m> is the [[temperature]] of the cold 'sink'		<math>T_L</math> is the [[temperature]] of the cold 'sink'
	and		and

	<m>T_H</m> is the temperature of the heat reservoir.		<math>T_H</math> is the temperature of the heat reservoir.

	This describes the efficiency of an idealized engine, which in reality is impossible to achieve.<ref>Hyperphysics, ''Carnot Cycle'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html</ref> From this equation, the lower the sink temperature <m>T_L</m> or the higher the source temperature <m>T_H</m>, the more work is available from the heat engine. The [[energy]] for work comes from a decrease in the total energy of the [[fluid]] used in the [[system]]. Therefore the greater the temperature change, the greater this decrease in the fluid and thus the greater energy available to do work is.<ref>R. A. Hinrichs and M. Kleinbach, "Heat and Work," in ''Energy: Its Use and the Environment'', 4th ed. Toronto, Ont. Canada: Thomson Brooks/Cole, 2006, ch.4, sec.E, pp.115</ref>


	''~~Click~~ [[~~Heat engine\|here~~]] to ~~learn about how a heat engine works~~.''		This describes the efficiency of an idealized engine, which in reality is impossible to achieve.<ref>Hyperphysics, ''Carnot Cycle'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html</ref> From this equation, the lower the sink temperature <math>T_L</math> or the higher the source temperature <math>T_H</math>, the more work is available from the heat engine. The [[energy]] for work comes from a decrease in the total energy of the [[fluid]] used in the [[system]]. Therefore the greater the temperature change, the greater this decrease in the fluid and thus the greater energy available to do work is.<ref>R. A. Hinrichs and M. Kleinbach, "Heat and Work," in ''Energy: Its Use and the Environment'', 4th ed. Toronto, Ont. Canada: Thomson Brooks/Cole, 2006, ch.4, sec.E, pp.115</ref>

	''For thermal efficiency of car engines, click [[fuel efficiency\|here]]~~.''~~		== For Further Reading ==
			For further information please see the related pages below:
			*[[Heat engine]]
			*[[Hydrocarbon combustion]] is often the source of heat for these engines.
			*[[Solar thermal power plant]]
			*[[Nuclear power plant]]
			*For thermal efficiency of car engines, click [[fuel efficiency\|here]]
			* Or explore a [[Special:Random\| random page!]]

	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]
			[[category:371 topics]]
			[[category:301 topics]]

J.williams: 1 revision imported

2015-09-18T16:52:04Z

1 revision imported

← Older revision	Revision as of 16:52, 18 September 2015
(No difference)

Jhanania at 23:37, 4 September 2015

2015-09-04T23:37:43Z

← Older revision		Revision as of 23:37, 4 September 2015
Line 1:		Line 1:
	[[category:371 topics]]		[[category:371 topics]]
	[[Category:Done 2015-07-24]]		[[Category:Done 2015-09-06]]
	[[category:301 topics]]		[[category:301 topics]]
	[[Category:waiting for simulation]]		[[Category:waiting for simulation]]
	[[File:Flow Chart thing.png\|340px\|thumbnail\|Figure 1: The amount of work output for a given amount of heat gives a system its thermal efficiency.<ref>This picture was made by the Energy Education team.</ref>]]		[[File:Flow Chart thing.png\|340px\|thumbnail\|Figure 1: The amount of work output for a given amount of heat gives a system its thermal efficiency.<ref>This picture was made by the Energy Education team.</ref>]]
	<onlyinclude>The '''thermal efficiency''' of a [[heat engine]] is the amount of useful work an engine can do based on the amount of heat input.</onlyinclude> The thermal efficiency is represented by the symbol <m>\eta</m>, and given by the equation		<onlyinclude>The '''thermal efficiency''' of a [[heat engine]] is the amount of useful [[work]] an engine can do based on the amount of [[heat]] input.</onlyinclude> The thermal efficiency is represented by the symbol <m>\eta</m>, and given by the equation

	<center><m>\eta=\frac{W}{Q_H}</m></center>		<center><m>\eta=\frac{W}{Q_H}</m></center>
Line 23:		Line 23:
	==Carnot Efficiency==		==Carnot Efficiency==
	:''[[Carnot efficiency\|main article]]''		:''[[Carnot efficiency\|main article]]''
	There is a maximum attainable efficiency of a heat engine which was derived by physicist Sadi Carnot. Following laws of thermodynamics the equation for this turns out to be		There is a maximum attainable efficiency of a heat engine which was derived by physicist Sadi Carnot. Following laws of [[thermodynamics]] the equation for this turns out to be

	<center><m>\eta_{max}=1 - \frac{T_L}{T_H}</m></center>		<center><m>\eta_{max}=1 - \frac{T_L}{T_H}</m></center>
Line 29:		Line 29:
	Where		Where

	<m>T_L</m> is the temperature of the cold 'sink'		<m>T_L</m> is the [[temperature]] of the cold 'sink'
	and		and

	<m>T_H</m> is the temperature of the heat reservoir.		<m>T_H</m> is the temperature of the heat reservoir.

	This describes the efficiency of an idealized engine, which in reality is impossible to achieve.<ref>Hyperphysics, ''Carnot Cycle'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html</ref> From this equation, the lower the sink temperature <m>T_L</m> or the higher the source temperature <m>T_H</m>, the more work is available from the heat engine. The energy for work comes from a decrease in the total energy of the fluid used in the system. Therefore the greater the temperature change, the greater this decrease in the fluid and thus the greater energy available to do work is.<ref>R. A. Hinrichs and M. Kleinbach, "Heat and Work," in ''Energy: Its Use and the Environment'', 4th ed. Toronto, Ont. Canada: Thomson Brooks/Cole, 2006, ch.4, sec.E, pp.115</ref>		This describes the efficiency of an idealized engine, which in reality is impossible to achieve.<ref>Hyperphysics, ''Carnot Cycle'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html</ref> From this equation, the lower the sink temperature <m>T_L</m> or the higher the source temperature <m>T_H</m>, the more work is available from the heat engine. The [[energy]] for work comes from a decrease in the total energy of the [[fluid]] used in the [[system]]. Therefore the greater the temperature change, the greater this decrease in the fluid and thus the greater energy available to do work is.<ref>R. A. Hinrichs and M. Kleinbach, "Heat and Work," in ''Energy: Its Use and the Environment'', 4th ed. Toronto, Ont. Canada: Thomson Brooks/Cole, 2006, ch.4, sec.E, pp.115</ref>

J.williams: 1 revision imported

2015-08-26T21:31:43Z

1 revision imported

← Older revision	Revision as of 21:31, 26 August 2015
(No difference)

J.williams at 17:00, 12 August 2015

2015-08-12T17:00:13Z

New page

[[category:371 topics]]
[[Category:Done 2015-07-24]]
[[category:301 topics]]
[[Category:waiting for simulation]]
[[File:Flow Chart thing.png|340px|thumbnail|Figure 1: The amount of work output for a given amount of heat gives a system its thermal efficiency.<ref>This picture was made by the Energy Education team.</ref>]]
<onlyinclude>The '''thermal efficiency''' of a [[heat engine]] is the amount of useful work an engine can do based on the amount of heat input.</onlyinclude> The thermal efficiency is represented by the symbol <m>\eta</m>, and given by the equation

<center><m>\eta=\frac{W}{Q_H}</m></center>

Where:

<m>W</m> is the useful work and

<m>Q_H</m> is the total heat energy input from the hot source.</onlyinclude><ref>TPUB Engine Mechanics. (April 4, 2015). ''Thermal Efficiency'' [Online]. Available: http://enginemechanics.tpub.com/14075/css/14075_141.htm</ref>

Heat engines often operate at around 30% to 50% efficiency, due to practical limitations. It is impossible for heat engines to achieve 100% thermal efficiency (<m>\eta = 1</m>) according to the [[Second law of thermodynamics]]. This is impossible because some [[waste heat]] is always produced produced in a heat engine, shown in Figure 1 by the <m>Q_L</m> term. Although complete efficiency in a heat engine is impossible, there are many ways to [[Waste heat#Harnessing waste heat|increase a system's overall efficiency]].

===An Example===
If 200 [[joule]]s of [[thermal energy]] as heat is input (<m>Q_H</m>), and the engine does 80 J of work (<m>W</m>), then the efficiency is 80J/200J, which is 40% efficient.

This same result can be gained by measuring the waste heat of the engine. For example, if 200 J is put into the engine, and observe 120 J of waste heat, then 80 J of work must have been done, giving 40% efficiency.

==Carnot Efficiency==
:''[[Carnot efficiency|main article]]''
There is a maximum attainable efficiency of a heat engine which was derived by physicist Sadi Carnot. Following laws of thermodynamics the equation for this turns out to be

<center><m>\eta_{max}=1 - \frac{T_L}{T_H}</m></center>

Where

<m>T_L</m> is the temperature of the cold 'sink'
and

<m>T_H</m> is the temperature of the heat reservoir.

This describes the efficiency of an idealized engine, which in reality is impossible to achieve.<ref>Hyperphysics, ''Carnot Cycle'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html</ref> From this equation, the lower the sink temperature <m>T_L</m> or the higher the source temperature <m>T_H</m>, the more work is available from the heat engine. The energy for work comes from a decrease in the total energy of the fluid used in the system. Therefore the greater the temperature change, the greater this decrease in the fluid and thus the greater energy available to do work is.<ref>R. A. Hinrichs and M. Kleinbach, "Heat and Work," in ''Energy: Its Use and the Environment'', 4th ed. Toronto, Ont. Canada: Thomson Brooks/Cole, 2006, ch.4, sec.E, pp.115</ref>

''Click [[Heat engine|here]] to learn about how a heat engine works.''

''For thermal efficiency of car engines, click [[fuel efficiency|here]].''

==References==
{{reflist}}
[[Category:Uploaded]]