{"id":1451,"date":"2021-07-14T14:42:12","date_gmt":"2021-07-14T18:42:12","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/thermo1\/chapter\/4-2-heat-transfer-across-a-boundary\/"},"modified":"2022-08-03T18:21:23","modified_gmt":"2022-08-03T22:21:23","slug":"4-2-heat-transfer-across-a-boundary","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/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":"
\r\n\r\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>.\r\n\r\n \r\n\r\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\r\n\r\n<\/div>\r\n
\r\n

[latex]{}_{1}Q_{2}=\\displaystyle\\int_{1}^{2}{\\delta Q}[\/latex]<\/p>\r\n \r\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>\r\n \r\n\r\nSpecific heat transfer refers to the amount of heat transfer per unit mass of a substance. It is defined as \r\n<\/strong>\r\n

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

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

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

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

\r\n

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

\r\n\r\n[h5p id=\"32\"]\r\n\r\n<\/div>\r\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
\n