{"id":2490,"date":"2016-03-14T14:44:46","date_gmt":"2016-03-14T14:44:46","guid":{"rendered":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/?p=2490"},"modified":"2016-03-14T14:44:46","modified_gmt":"2016-03-14T14:44:46","slug":"power-and-refriger-a-tion-cyclesrefrigerators-and-heat-pumps","status":"publish","type":"post","link":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/power-and-refriger-a-tion-cyclesrefrigerators-and-heat-pumps\/","title":{"rendered":"POWER AND REFRIGER A TION CYCLES:REFRIGERATORS AND HEAT PUMPS"},"content":{"rendered":"<div class=\"glyoz6a0dbe5be44ba\" ><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.glyoz6a0dbe5be44ba {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.glyoz6a0dbe5be44ba {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.glyoz6a0dbe5be44ba {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.glyoz6a0dbe5be44ba {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.glyoz6a0dbe5be44ba {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<p align=\"justify\"><font size=\"5\">\u25a0 <b>REFRIGER<\/b><b>A<\/b><b>TOR<\/b><b>S AND HEAT PUMPS<\/b><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">We all know from experience that heat flows in the direction of decreasing temperature, that is, from high-temperature regions to low-temperature ones. This heat transfer process occurs in nature without requiring any devices. The reverse process, however, cannot occur by itself. The transfer of heat from a low-temperature region to a high-temperature one requires special devices called <b>r<\/b><b>efrigerators.<\/b><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">Refrigerators are cyclic devices, and the working fluids used in the refrigeration cycles are called <b>r<\/b><b>efrigerants<\/b><b>. <\/b>A refrigerator is shown schematically in Fig. 8\u201351<i>a<\/i>. Here <i>Q<\/i><i>L <\/i>is the magnitude of the heat removed from the refrigerated space at temperature <i>T<\/i><i>L<\/i>, <i>Q<\/i><i>H <\/i>is the magnitude of the heat rejected to the warm space at temperature <i>T<\/i><i>H<\/i>, and <i>W<\/i>net, in is the net work input to the refrigerator. As discussed before, <i>Q<\/i><i>L <\/i>and <i>Q<\/i><i>H <\/i>represent magnitudes and thus are positive quantities.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">Another device that transfers heat from a low-temperature medium to a high-temperature one is the <b>hea<\/b><b>t pump. <\/b>Refrigerators and heat pumps are essentially the same devices; they differ in their objectives only. The objective of a refrigerator is to maintain the refrigerated space at a low temperature by removing heat from it. Discharging this heat to a higher-temperature medium is merely a necessary part of the operation, not the purpose. The objective of<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/POWER-AND-REFRIGERATION-CYCLES-0359.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=\"POWER AND REFRIGERATION CYCLES-0359\" border=\"0\" alt=\"POWER AND REFRIGERATION CYCLES-0359\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/POWER-AND-REFRIGERATION-CYCLES-0359_thumb.jpg\" width=\"524\" height=\"257\"><\/a><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">a heat pump, however, is to maintain a heated space at a high temperature. This is accomplished by absorbing heat from a low-temperature source, such as well water or cold outside air in winter, and supplying this heat to a warmer medium such as a house (Fig. 8\u201351<i>b<\/i>).<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">The performance of refrigerators and heat pumps is expressed in terms of the <b>coefficient of performance <\/b>(COP), which was defined as<\/font> <\/p><div class=\"ediow6a0dbe5be469a\" ><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.ediow6a0dbe5be469a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.ediow6a0dbe5be469a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.ediow6a0dbe5be469a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.ediow6a0dbe5be469a {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.ediow6a0dbe5be469a {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n<div class=\"sfqlv6a0dbe5be45a4\" ><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.sfqlv6a0dbe5be45a4 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 993px) and (max-width: 1200px) {\r\n.sfqlv6a0dbe5be45a4 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 769px) and (max-width: 992px) {\r\n.sfqlv6a0dbe5be45a4 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (min-width: 768px) and (max-width: 768px) {\r\n.sfqlv6a0dbe5be45a4 {\r\ndisplay: block;\r\n}\r\n}\r\n@media screen and (max-width: 767px) {\r\n.sfqlv6a0dbe5be45a4 {\r\ndisplay: block;\r\n}\r\n}\r\n<\/style>\r\n\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/POWER-AND-REFRIGERATION-CYCLES-0360.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=\"POWER AND REFRIGERATION CYCLES-0360\" border=\"0\" alt=\"POWER AND REFRIGERATION CYCLES-0360\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/POWER-AND-REFRIGERATION-CYCLES-0360_thumb.jpg\" width=\"356\" height=\"133\"><\/a><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">for fixed values of <i>Q<\/i><i>L <\/i>and <i>Q<\/i><i>H<\/i>. This relation implies that COPHP &gt; 1 since COPR is a positive quantity. That is, a heat pump will function, at worst, as a resistance heater, supplying as much energy to the house as it consumes. In reality, however, part of <i>Q<\/i><i>H <\/i>is lost to the outside air through piping and other devices, and COPHP may drop below unity when the outside air temperature is too low. When this happens, the system normally switches to the fuel (natural gas, propane, oil, etc.) or resistance-heating mode.<\/font> <\/p>\n<p align=\"justify\"><font size=\"5\">The <i>coolin<\/i><i>g capacity <\/i>of a refrigeration system\u2014that is, the rate of heat removal from the refrigerated space\u2014is often expressed in terms of <b>ton<\/b><b>s of refrigeration. <\/b>The capacity of a refrigeration system that can freeze 1 ton (2000 lbm) of liquid water at 0\u00b0C (32\u00b0F) into ice at 0\u00b0C in 24 h is said to be 1 ton. One ton of refrigeration is equivalent to 211 kJ\/min or 200 Btu\/min. The cooling load of a typical 200-m2 residence is in the 3-ton (10-kW) range. <\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/POWER-AND-REFRIGERATION-CYCLES-0361.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=\"POWER AND REFRIGERATION CYCLES-0361\" border=\"0\" alt=\"POWER AND REFRIGERATION CYCLES-0361\" src=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-content\/uploads\/2016\/03\/POWER-AND-REFRIGERATION-CYCLES-0361_thumb.jpg\" width=\"459\" height=\"279\"><\/a><\/font> <\/p>\n<p align=\"justify\">\n<p align=\"justify\"><font size=\"5\"><i><\/i><\/font> <\/p>\n<p align=\"justify\"><font size=\"5\"><\/font><\/p>\n<p align=\"justify\"><font size=\"5\"><\/font><\/p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u25a0 REFRIGERATORS AND HEAT PUMPS We all know from experience that heat flows in the direction of decreasing temperature, that is, from high-temperature regions to low-temperature ones. This heat transfer process occurs in nature without requiring any devices. The reverse process, however, cannot occur by itself. The transfer of heat from a low-temperature region to [&hellip;]<br \/><a href=\"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/power-and-refriger-a-tion-cyclesrefrigerators-and-heat-pumps\/\" 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\/2490"}],"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=2490"}],"version-history":[{"count":1,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/posts\/2490\/revisions"}],"predecessor-version":[{"id":2491,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/posts\/2490\/revisions\/2491"}],"wp:attachment":[{"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/media?parent=2490"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/categories?post=2490"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/machineryequipmentonline.com\/hydraulics-and-pneumatics\/wp-json\/wp\/v2\/tags?post=2490"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}