# Heat Conduction Along a Composite Bar

Topics: Heat, Heat transfer, Thermal conductivity Pages: 4 (1106 words) Published: February 20, 2013
Heat Conduction along a Composite Bar
Objective
To study the conduction of heat along a composite bar and evaluate the overall heat transfer coefficient. Theory
Thermal conduction is the mode of heat transfer which occurs in a material by virtue of a temperature gradient within it. A solid is chosen for the demonstration of pure conduction since both liquids and gasses exhibit excessive convective heat transfer. In a practical situation, heat conduction occurs in three detentions, a complexity which often requires extensive computation to analyse. In the laboratory, a single dimensional approach is required to demonstrate the basic law that relates rate of heat flow to temperature gradient and area. For steady flow along the bar, the heat flow through successive slabs is the same for reasons of continuity. Hence, from Fourier’s law QA=kHTHS-THIXH=kSTHI-TCIXS=kCTCI-TCSXC(1)

We may write Eq (1) as
QA=U(THS-TCS)(2)
Where,
1Q=XHkH+XSkS+XCkC(3)
U is overall heat transfer coefficient for the composite wall and IUis the overall resistance to the heat flow.

Apparatus

Figure 1: Front view of calibration unit and transformer

Figure 2: Front view of the test unit

The heat conduction apparatus shown in Figure 1&2 consist of two electricity heated module mounted on a bench support frame. One module contains a cylindrical metal bar arrangement for a variety of linear conduction experiments while the other consists of a disc for radial profile studies. Both test section are equipped with an array of temperature gradient. The instrumentation provided permits accurate measurements of temperature and electrical power supplied to the heater. Fast response temperature probes, with a resolution of 0.1°C, give direct digital readout in °C. The power control circuit provides a continuously variable electrical output of 0-80 Watts nominal (at nominal supply voltage) with direct digital readout having a resolution of 0.1W. The test modules...