As described in part one, Thermal Conductivity is determined under steady state conditions by calculating the thermal resistance of a given material component. Thermal conductivity is, however; not the sole variable determining its value. In this experiment, a simple set-up will be used to determine the effect which component length has on heat flow and temperature difference on said component. This concept plays quite an important role in various industries such as the insulation industry
The goal of this experiment is to demonstrate the effect which varying length has on the thermal resistance of a given component. This will ultimately provide insight into the variables involved in heat flow and thermal resistance.
In a laboratory setting, Thermal Conductivity is derived by first calculating thermal resistance. From this thermal conductivity can be determine, however; if thermal conductivity is known, one can calculate the length of a given sample as well given its surface area.
Heat Flow Equation Q = ΔT / RΘ
This experiment will vary the bolded constant via different samples.
The design of this experiment is to observe the differences in temperature between components with varying length thus surface area, temperature difference and thermal conductivity must remain the same. It may be completed with non-metal samples, however; once again one may run the risk of a lengthy test time. In light of this metals are recommended and a table of various suitable metals can be found below.
|Material||Thermal Conductivity (W/m-K)||Pricing||Location of Purchase|
|Copper||397.48||~12$ for 10’||Amazon|
|Aluminum||225.94||~15$ for 32’||Amazon|
|Brass||~117.14||~6$ for 24’||Amazon|
|Material||Price||Location of Purchase|
|Wiring (Same Diameter, 1.1m)
|Between 5-10$ each, 15-30$ total.||Amazon|
|Beaker x2 (50ml)||3$||Indigo Instruments|
As with part 1, the temperature difference can be identified by one of two ways: the degree of melted candle at the tip of the wire or the temperature difference between wire tips and tails. The wire with the highest degree of melted candles at its tip is consider to have the most the smallest temperature difference. Should the experiment have occurred without problem, the shortest wire will have the highest degree of melted candle and the lowest temperature difference between tail and tip.
It is to no surprise that the shortest wire will transfer the most heat across itself. Thermal Resistance is dependent on Length, Thermal Conductivity and Surface area. As length decreases so does Thermal Resistance and if the heat flow remained the same (as it should) the temperature difference must also decrease. The analogy of a road can be employed in this case. In order to reach from point A to point B, you have to travel along a road. The shorter the road the faster you will reach your destination, however; double that road and you require twice the time to make that journey. This concept as stated before plays an important role in the insulation industry. Instead of having a thin piece of insulation separating the inside of house from the outside, the insulation is thick. This slows the progression of heat from the inside out or the outside in and can save a lot of money.
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