{"id":112,"date":"2021-07-14T14:42:12","date_gmt":"2021-07-14T14:42:12","guid":{"rendered":"https:\/\/libraryresources.nse.org.ng\/thermo1\/chapter\/4-2-heat-transfer-across-a-boundary\/"},"modified":"2026-03-16T13:55:36","modified_gmt":"2026-03-16T13:55:36","slug":"4-2-heat-transfer-across-a-boundary","status":"publish","type":"chapter","link":"https:\/\/libraryresources.nse.org.ng\/thermo1\/chapter\/4-2-heat-transfer-across-a-boundary\/","title":{"raw":"4.2 Heat transfer across a boundary","rendered":"4.2 Heat transfer across a boundary"},"content":{"raw":"
\n\nThe total energy stored in a system may change when energy is transferred into or out of the system. For a closed system, the energy transfer is achieved via two mechanisms: heat and work, as illustrated in Figure 1.2.3<\/a>.\n\n \n\nHeat transfer takes place when a temperature difference exists between a system and its surroundings. As heat transfer must cross the system boundary, it is a boundary phenomenon<\/em>. The heat transfer between two states during a process can be written as\n\n<\/div>\n
\n

[latex]{}_{1}Q_{2}=\\displaystyle\\int_{1}^{2}{\\delta Q}[\/latex]<\/p>\n \n

Different from internal energy, heat transfer is NOT a state function. It is a path function because the amount of heat that is absorbed or rejected by a substance in a process depends not only on the initial and final states, but also on the process path. Although heat transfer is NOT a property of a system, it has a significant effect on the changes of properties of the system in a process.<\/p>\n \n\nSpecific heat transfer refers to the amount of heat transfer per unit mass of a substance. It is defined as \n<\/strong>\n

[latex]q=\\displaystyle\\frac{Q}{m}[\/latex]<\/p>\nwhere\n

[latex]m[\/latex]: mass of a system, in kg<\/p>\n

[latex]Q[\/latex]: amount of heat transfer in a process, in kJ<\/p>\n

[latex]q[\/latex]: amount of specific heat transfer in a process, in kJ\/kg<\/p>\n \n\n<\/div>\n

\n

Practice Problems<\/p>\n\n<\/header>\n

\n\nThe original version of this chapter contained H5P content. You may want to remove or replace this element.\n\n<\/div>\n<\/div>","rendered":"
\n

The total energy stored in a system may change when energy is transferred into or out of the system. For a closed system, the energy transfer is achieved via two mechanisms: heat and work, as illustrated in Figure 1.2.3<\/a>.<\/p>\n

 <\/p>\n

Heat transfer takes place when a temperature difference exists between a system and its surroundings. As heat transfer must cross the system boundary, it is a boundary phenomenon<\/em>. The heat transfer between two states during a process can be written as<\/p>\n<\/div>\n

\n

[latex]{}_{1}Q_{2}=\\displaystyle\\int_{1}^{2}{\\delta Q}[\/latex]<\/p>\n

 <\/p>\n

Different from internal energy, heat transfer is NOT a state function. It is a path function because the amount of heat that is absorbed or rejected by a substance in a process depends not only on the initial and final states, but also on the process path. Although heat transfer is NOT a property of a system, it has a significant effect on the changes of properties of the system in a process.<\/p>\n

 <\/p>\n

Specific heat transfer refers to the amount of heat transfer per unit mass of a substance. It is defined as
\n<\/strong><\/p>\n

[latex]q=\\displaystyle\\frac{Q}{m}[\/latex]<\/p>\n

where<\/p>\n

[latex]m[\/latex]: mass of a system, in kg<\/p>\n

[latex]Q[\/latex]: amount of heat transfer in a process, in kJ<\/p>\n

[latex]q[\/latex]: amount of specific heat transfer in a process, in kJ\/kg<\/p>\n

 <\/p>\n<\/div>\n

\n
\n

Practice Problems<\/p>\n<\/header>\n

\n

The original version of this chapter contained H5P content. You may want to remove or replace this element.<\/p>\n<\/div>\n<\/div>\n","protected":false},"author":1,"menu_order":3,"template":"","meta":{"pb_show_title":"","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-112","chapter","type-chapter","status-publish","hentry"],"part":104,"_links":{"self":[{"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/pressbooks\/v2\/chapters\/112","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/wp\/v2\/users\/1"}],"version-history":[{"count":1,"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/pressbooks\/v2\/chapters\/112\/revisions"}],"predecessor-version":[{"id":113,"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/pressbooks\/v2\/chapters\/112\/revisions\/113"}],"part":[{"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/pressbooks\/v2\/parts\/104"}],"metadata":[{"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/pressbooks\/v2\/chapters\/112\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/wp\/v2\/media?parent=112"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/pressbooks\/v2\/chapter-type?post=112"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/wp\/v2\/contributor?post=112"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/libraryresources.nse.org.ng\/thermo1\/wp-json\/wp\/v2\/license?post=112"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}