{"id":21059,"date":"2019-02-13T17:01:33","date_gmt":"2019-02-13T17:01:33","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=21059"},"modified":"2023-02-28T09:15:14","modified_gmt":"2023-02-28T09:15:14","slug":"heat-exchanger-heat-transfer-coefficient-u-factor","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/heat-transfer\/heat-exchangers\/heat-exchanger-heat-transfer-coefficient-u-factor\/","title":{"rendered":"Heat Exchanger – Heat Transfer Coefficient – U-Factor"},"content":{"rendered":"
<\/a>A heat exchanger<\/strong> typically involves two flowing fluids separated by a solid wall. Many of the heat transfer processes encountered in the industry involve composite systems and even involve a combination of both conduction<\/a> and convection<\/a>. Heat is first transferred from the hot fluid to the wall by convection, through the wall by conduction, and then to the cold fluid again by convection.<\/p>\n It is often convenient to work with an overall heat transfer coefficient<\/a>, <\/strong>known as a U-factor <\/strong>with these composite systems. The U-factor is defined by an expression analogous to Newton\u2019s law of cooling<\/strong>:<\/p>\n <\/a><\/p>\n <\/a>The overall heat transfer coefficient, U,<\/strong> is related to the total thermal resistance<\/a> and depends on the geometry of the problem. For example, heat transfer<\/a> in a steam generator<\/a> involves convection from the bulk of the reactor coolant to the steam generator inner tube surface, conduction through the tube wall, and convection (boiling) from the outer tube surface to the secondary side fluid.<\/p>\n In cases of combined heat transfer for a heat exchanger, there are two values for h. The convective heat transfer coefficient (h) for the fluid film inside the tubes and a convective heat transfer coefficient for the fluid film outside the tubes. The tube wall\u2019s thermal conductivity<\/a> (k) and thickness (\u0394x) must also be accounted for.<\/p>\n