{"id":505,"date":"2021-05-30T01:20:31","date_gmt":"2021-05-30T05:20:31","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/thermo1\/chapter\/what-is-thermodynamics-about\/"},"modified":"2022-08-02T17:57:57","modified_gmt":"2022-08-02T21:57:57","slug":"what-is-thermodynamics-about","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/thermo1\/chapter\/what-is-thermodynamics-about\/","title":{"raw":"1.1 What is thermodynamics about?","rendered":"1.1 What is thermodynamics about?"},"content":{"raw":"
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You probably have this experience; when you rub your hands quickly for a few minutes, your hands will start to feel warmer. How is this common phenomenon related to thermodynamics? Well, when you rub your hands quickly, your muscles do [pb_glossary id=\"721\"]work[\/pb_glossary]. This work is then converted to [pb_glossary id=\"722\"]heat[\/pb_glossary]; therefore, you feel warmer.\u00a0 Heat and work are two forms of energy. Work can be converted to heat, as seen in this daily example. However, can heat be converted to work? Can we use heat to produce work?<\/p>\r\n \r\n

[pb_glossary id=\"556\"]Heat engine[\/pb_glossary] is a device that produces work continuously by absorbing heat from a high-temperature heat source and rejecting the waste heat to a low-temperature heat sink. Since the 17th<\/sup> century, various heat engines were invented in an attempt to harness work from heat. Figure 1.1.1<\/a> illustrates Watt\u2019s engine invented by Scottish engineer James Watt in the late 18th<\/sup> century. Watt\u2019s engine is one of the <\/span>most <\/span>successful <\/span>early heat engine<\/span>s<\/span>. Its <\/span>main components are a boiler (not shown in the figure) and a condenser, each connecting to a piston-cylinder device. The two valves, V<\/em> and V<\/em>\u2019<\/em>, control the flow of steam into and out of the cylinder. <\/span>When valve <\/span>V<\/em> opens, valve <\/span>V<\/em>\u2019<\/em> remains closed. S<\/span>team <\/span>from<\/span> the<\/span> boiler enters the <\/span>cylinder, pushing the piston up until it reaches the top of the cylinder. <\/span>Then valve <\/span>V<\/em>\u2019<\/em> open<\/span>s<\/span>,<\/span> and valve <\/span>V<\/em> close<\/span>s<\/span>. The <\/span>steam <\/span>in the cylinder escapes to the condenser and is <\/span>condensed<\/span>, <\/span>creating <\/span>a <\/span>vacuum in the <\/span>cylinder. Consequently, the piston move<\/span>s<\/span> downward under <\/span>atmospheric pressure<\/span>. <\/span>The reciprocating motion of the piston drives the <\/span>pivoting <\/span>beam <\/span>DEF<\/em>, which then powers <\/span>the <\/span>pump <\/span>chained to the beam. Watt's engine demonstrates how heat is converted to work. This conversion relies on the phase change of a working fluid, e.g., water, in the Watt's engine. The boiler in the Watt's engine is the heat source, where the hot steam is generated; and the condenser is the heat sink, where the hot steam is cooled and condensed to liquid water. All heat engines need a working fluid circulating in a specially-arranged set of equipment, which operates between a high-temperature heat source and a low-temperature heat sink. <\/span>Figure 1.1.2<\/a> is a schematic drawing of a heat engine. <\/a> The yellow circle represents the heat engine consisting of a set of equipment.\r\n<\/span><\/p>\r\n \r\n\r\n<\/div>\r\n

\r\n\r\n \r\n\r\n[caption id=\"attachment_756\" align=\"aligncenter\" width=\"255\"]\"James<\/a> Figure 1.1.1<\/strong> <\/a> Watt's heat engine<\/em>[\/caption]\r\n\r\n \r\n\r\n[caption id=\"attachment_444\" align=\"aligncenter\" width=\"300\"]\"A<\/a> Figure 1.1.2<\/strong> Schematic drawing of a heat engine<\/em>[\/caption]\r\n

By examining Figure 1.1.2<\/a>, you might notice that a certain amount of heat is not converted to work. It is true that not<\/em> all<\/em> of the <\/em>heat from a heat source\u00a0<\/em><\/strong>can be converted to useful work<\/em>!\u00a0<\/em><\/strong> Heat engines and their underlying principles are governed by the two fundamental laws of thermodynamics, the first and second laws of thermodynamics. We will briefly introduce the two laws here and will provide detailed explanations in Chapters 4-6.<\/p>\r\n\r\n