{"id":1580,"date":"2016-03-09T19:20:55","date_gmt":"2016-03-09T19:20:55","guid":{"rendered":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/?p=1580"},"modified":"2016-03-09T19:20:55","modified_gmt":"2016-03-09T19:20:55","slug":"energy-transfer-by-heatworkand-massenergy-transfer-by-work","status":"publish","type":"post","link":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/energy-transfer-by-heatworkand-massenergy-transfer-by-work\/","title":{"rendered":"ENERGY TRANSFER BY HEAT,WORK,AND MASS:ENERGY TRANSFER BY WORK"},"content":{"rendered":"<div class=\"sovvj6a0dbe7188339\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '61e5902552e2353963d8d2f1bd1f4a8f',\n\t\t'format' : 'iframe',\n\t\t'height' : 250,\n\t\t'width' : 300,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/61e5902552e2353963d8d2f1bd1f4a8f\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.sovvj6a0dbe7188339 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.sovvj6a0dbe7188339 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.sovvj6a0dbe7188339 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.sovvj6a0dbe7188339 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.sovvj6a0dbe7188339 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<p align=\"justify\"><font size=\"5\"><b>ENERG<\/b><b>Y TRANSFER BY WORK<\/b><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">Work, like heat, is an energy interaction between a system and its surroundings. As mentioned earlier, energy can cross the boundary of a closed system in the form of heat or work. Therefore, <i>i<\/i><i>f the energy crossing the boundary of a closed system is not heat, it must be work<\/i>. Heat is easy to recognize: Its driving force is a temperature difference between the system and its surroundings. Then we can simply say that an energy interaction that is not caused by a temperature difference between a system and its surroundings is work. More specifically, <i>work is the energy transfer associated with a force acting through a distance<\/i>. A rising piston, a rotating shaft, and an electric wire crossing the system boundaries are all associated with work interactions.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">Work is also a form of energy transferred like heat and, therefore, has energy units such as kJ. The work done during a process between states 1 and 2 is denoted by <i>W<\/i>12, or simply <i>W<\/i>. The work done <i>pe<\/i><i>r unit mass <\/i>of a system is denoted by <i>w <\/i>and is expressed as<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0205.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0205\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0205\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0205_thumb.jpg\" width=\"186\" height=\"313\"><\/a><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">The work done <i>per unit time <\/i>is called <b>power <\/b>and is denoted <i>W <\/i>(Fig. 4\u20138). The <\/font><font size=\"5\">unit of power is kJ\/s, or kW.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">Heat and work are <i>directional quantities<\/i>, and thus the complete description of a heat or work interaction requires the specification of both the <i>magnitude <\/i>and <i>direction<\/i>. One way of doing that is to adopt a sign convention. The gen- erally accepted <b>formal sign convention <\/b>for heat and work interactions is as follows: <i>heat transfer to a system and work done by a system are positive; heat transfer from a system and work done on a system are negative<\/i>. Another way is to use the subscripts <i>in <\/i>and <i>out <\/i>to indicate direction (Fig. 4\u20139). For ex<\/font><font size=\"5\">ample, a work input of 5 kJ can be expressed as <i>W<\/i>in = 5 kJ, while a heat loss of 3 kJ can be expressed as <i>Q<\/i>out = 3 kJ. When the direction of a heat or work interaction is not known, we can simply <i>assum<\/i><i>e <\/i>a direction for the interaction (using the subscript <i>in <\/i>or <i>out<\/i>) and solve for it. A positive result indicates the assumed direction is right. A negative result, on the other hand, indicates that the direction of the interaction is the opposite of the assumed direction. This is just like assuming a direction for an unknown force when solving a statics problem, and reversing the direction when a negative result is obtained for the <\/font><font size=\"5\">The relationships among <i>w<\/i>, <i>W<\/i>, and <i>W<\/i>.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">force. We will use this <i>intuitiv<\/i><i>e approach <\/i>in this book as it eliminates the need to adopt a formal sign convention and the need to carefully assign negative values to some interactions.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">Note that a quantity that is transferred to or from a system during an inter- action is not a property since the amount of such a quantity depends on more than just the state of the system. Heat and work are <i>ene<\/i><i>r<\/i><i>g<\/i><i>y transfer mecha- nisms <\/i>between a system and its surroundings, and there are many similarities between them:<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><b>1. <\/b>Both are recognized at the boundaries of a system as they cross the boundaries. That is, both heat and work are <i>boundary <\/i>phenomena.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><b>2. <\/b>Systems possess energy, but not heat or work.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><b>3. <\/b>Both are associated with a <i>p<\/i><i>r<\/i><i>ocess<\/i><i>, <\/i>not a state. Unlike properties, heat or work has no meaning at a state.<\/font> <\/p><div class=\"xmuwf6a0dbe71885a8\" ><script type=\"text\/javascript\">\n\tatOptions = {\n\t\t'key' : '0c1eb4c533eaedb7b996f49a5a4983a9',\n\t\t'format' : 'iframe',\n\t\t'height' : 300,\n\t\t'width' : 160,\n\t\t'params' : {}\n\t};\n<\/script>\n<script type=\"text\/javascript\" src=\"\/\/www.highperformanceformat.com\/0c1eb4c533eaedb7b996f49a5a4983a9\/invoke.js\"><\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.xmuwf6a0dbe71885a8 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.xmuwf6a0dbe71885a8 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.xmuwf6a0dbe71885a8 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.xmuwf6a0dbe71885a8 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.xmuwf6a0dbe71885a8 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<div class=\"jrngj6a0dbe7188459\" ><script async src=\"https:\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-0778475562755157\"\n     crossorigin=\"anonymous\"><\/script>\n<!-- 300x600 hydraulics-and-pneumatics -->\n<ins class=\"adsbygoogle\"\n     style=\"display:inline-block;width:300px;height:600px\"\n     data-ad-client=\"ca-pub-0778475562755157\"\n     data-ad-slot=\"3735577695\"><\/ins>\n<script>\n     (adsbygoogle = window.adsbygoogle || []).push({});\n<\/script><\/div><style type=\"text\/css\">\r\n@media screen and (min-width: 1201px) {\r\n.jrngj6a0dbe7188459 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.jrngj6a0dbe7188459 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.jrngj6a0dbe7188459 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.jrngj6a0dbe7188459 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.jrngj6a0dbe7188459 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n\n<p align=\"justify\"><font size=\"5\"><b>4. <\/b>Both are <i>pat<\/i><i>h functions <\/i>(i.e., their magnitudes depend on the path followed during a process as well as the end states).<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><b>Pat<\/b><b>h functions <\/b>have <b>inexac<\/b><b>t differentials <\/b>designated by the symbol d. There- fore, a differential amount of heat or work is represented by d<i>Q <\/i>or d<i>W<\/i>, respectively, instead of <i>d<\/i><i>Q <\/i>or <i>d<\/i><i>W<\/i><i>. <\/i>Properties, however, are <b>poin<\/b><b>t functions <\/b>(i.e., they depend on the state only, and not on how a system reaches that state), and they have <b>exac<\/b><b>t differentials <\/b>designated by the symbol <i>d. <\/i>A small change in volume, for example, is represented by <i>dV<\/i>, and the total volume change during a process between states 1 and 2 is<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0206.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0206\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0206\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0206_thumb.jpg\" width=\"125\" height=\"36\"><\/a><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">That is, the volume change during process 1\u20132 is always the volume at state 2 minus the volume at state 1, regardless of the path followed (Fig. 4\u201310). The total work done during process 1\u20132, however, is<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0207.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0207\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0207\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0207_thumb.jpg\" width=\"177\" height=\"37\"><\/a><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">That is, the total work is obtained by following the process path and adding the differential amounts of work (d<i>W<\/i>) done along the way. The integral of d<i>W is not W<\/i>2 &#8211; <i>W<\/i>1 (i.e., the work at state 2 minus work at state 1), which is meaningless since work is not a property and systems do not possess work at a state.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0208.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0208\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0208\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0208_thumb.jpg\" width=\"145\" height=\"484\"><\/a><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0209.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0209\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0209\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0209_thumb.jpg\" width=\"366\" height=\"478\"><\/a><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0210.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0210\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0210\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0210_thumb.jpg\" width=\"386\" height=\"304\"><\/a><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><strong>Electrical Work<\/strong><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">It was pointed out in Example 4\u20133 that electrons crossing the system bound<\/font><font size=\"5\">ary do electrical work on the system. In an electric field, electrons in a wire move under the effect of electromotive forces, doing work. When <i>N <\/i>coulombs of electrical charge move through a potential difference <i>V<\/i>, the electrical work done is<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0211.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0211\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0211\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0211_thumb.jpg\" width=\"133\" height=\"484\"><\/a><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0212.jpg\"><img decoding=\"async\" loading=\"lazy\" style=\"background-image: none; border-bottom: 0px; border-left: 0px; margin: 0px auto; padding-left: 0px; padding-right: 0px; display: block; float: none; border-top: 0px; border-right: 0px; padding-top: 0px\" title=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0212\" border=\"0\" alt=\"ENERGY TRANSFER BY HEAT,WORK,AND MASS-0212\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/ENERGY-TRANSFER-BY-HEATWORKAND-MASS-0212_thumb.jpg\" width=\"349\" height=\"199\"><\/a><\/font> <\/p>\n<p align=\"justify\">\n<p align=\"justify\"><i><font size=\"5\"><\/font><\/i><\/p>\n","protected":false},"excerpt":{"rendered":"<p>ENERGY TRANSFER BY WORK Work, like heat, is an energy interaction between a system and its surroundings. As mentioned earlier, energy can cross the boundary of a closed system in the form of heat or work. Therefore, if the energy crossing the boundary of a closed system is not heat, it must be work. Heat [&hellip;]<br \/><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/energy-transfer-by-heatworkand-massenergy-transfer-by-work\/\" class=\"more-link\" >Continue reading&#8230;<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/posts\/1580"}],"collection":[{"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/comments?post=1580"}],"version-history":[{"count":1,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/posts\/1580\/revisions"}],"predecessor-version":[{"id":1581,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/posts\/1580\/revisions\/1581"}],"wp:attachment":[{"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/media?parent=1580"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/categories?post=1580"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/tags?post=1580"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}