Page 1 Introduction • Convection The process of heat transfer between a solid surface & the fluid in motion. • Natural Fluid moves due to density diff. caused by HT between solid & liquid. • Forced Fluid motion is imparted by external means. i.e. pump,fan,slope etc. Page 2 Introduction • Convection The process of heat transfer between a solid surface & the fluid in motion. • Natural Fluid moves due to density diff. caused by HT between solid & liquid. • Forced Fluid motion is imparted by external means. i.e. pump,fan,slope etc. Mechanism of Forced Convection • Convection heat transfer is complicated since it involves fluid motion & heat conduction. • The fluid motion enhances heat transfer. • The rate of convection heat transfer is expressed by New ton’ s law of cooling: Page 3 Introduction • Convection The process of heat transfer between a solid surface & the fluid in motion. • Natural Fluid moves due to density diff. caused by HT between solid & liquid. • Forced Fluid motion is imparted by external means. i.e. pump,fan,slope etc. Mechanism of Forced Convection • Convection heat transfer is complicated since it involves fluid motion & heat conduction. • The fluid motion enhances heat transfer. • The rate of convection heat transfer is expressed by New ton’ s law of cooling: • The convective heat transfer coefficient h strongly depends on the fluid properties and roughness of the solid surface, and the type of the fluid flow. Page 4 Introduction • Convection The process of heat transfer between a solid surface & the fluid in motion. • Natural Fluid moves due to density diff. caused by HT between solid & liquid. • Forced Fluid motion is imparted by external means. i.e. pump,fan,slope etc. Mechanism of Forced Convection • Convection heat transfer is complicated since it involves fluid motion & heat conduction. • The fluid motion enhances heat transfer. • The rate of convection heat transfer is expressed by New ton’ s law of cooling: • The convective heat transfer coefficient h strongly depends on the fluid properties and roughness of the solid surface, and the type of the fluid flow. fig. Forced convection • It is assumed that the velocity of the fluid is zero at the wall, this assumption is called no-slip condition. Page 5 Introduction • Convection The process of heat transfer between a solid surface & the fluid in motion. • Natural Fluid moves due to density diff. caused by HT between solid & liquid. • Forced Fluid motion is imparted by external means. i.e. pump,fan,slope etc. Mechanism of Forced Convection • Convection heat transfer is complicated since it involves fluid motion & heat conduction. • The fluid motion enhances heat transfer. • The rate of convection heat transfer is expressed by New ton’ s law of cooling: • The convective heat transfer coefficient h strongly depends on the fluid properties and roughness of the solid surface, and the type of the fluid flow. fig. Forced convection • It is assumed that the velocity of the fluid is zero at the wall, this assumption is called no-slip condition. • As a result, the heat transfer from the solid surface to the fluid layer adjacent to the surface is by pure conduction, since the fluid is motionless. • Thus h in general, varies along the flow direction. • The mean or average convection heat transfer coefficient for a surface is determined by (properly) averaging the local heat transfer coefficient over the entire surface.Read More

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