One way of measuring the thermal conductivity of a material is to sandwich an electric thermofoil heater between two identical rectangular samples of the material and to heavily insulate the four outer edges, as shown in Fig. P1-56. Thermocouples attached to the inner and outer surfaces of the samples record the temperatures. During an experiment, two 0.5-cm-thick samples 10?cm × 10?cm in size are used. When steady operation is reached, the heater is observed to draw 25 W of electric power, and the temperature of each sample is observed to drop from 82°C at the inner surface to 74°C at the outer surface. Determine the thermal conductivity of the material at the average temperature.


The thermal conductivity of a material is to be determined by ensuring one-dimensional heat conduction, and by measuring temperatures when steady operating conditions are reached.

Assumptions 1 Steady operating conditions exist since the temperature readings do not change with time. 2 Heat losses through the lateral surfaces of the apparatus are negligible since those surfaces are well-insulated, and thus the entire heat generated by the heater is conducted through the samples. 3 The apparatus possesses thermal symmetry

Analysis For each sample we have



Trades & Technology

You might also like to view...

Lameness in a forelimb is indicated by ____.

A. the crop drops B. the tail swishing when the horse is asked to move C. the horse coughing while it moves from a trot to a canter D. a nod of the head when weight is placed on the sound limb

Trades & Technology

La letra I en la Figura 2 indica un(a) _____.



a. cumbrera
b. puntal
c. falso tirante
d. soporte superior vertical

Trades & Technology

The four basic types of SAE are exploratory, _____ research/experimentation, and placement

a. CDE c. FFA b. proficiency d. entrepreneurship

Trades & Technology

This is the opening inside the chimney that allows the smoke and combustion gases to pass from the firebox away from the structure:

A. chimney liner B. flue C. chimney anchors D. chimney cap E. chimney hood

Trades & Technology