hw5soln

hw5soln - Solution Homework #5 Problem No. 1 A Pt Pt/13% Rd...

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Solution Homework #5 Problem No. 1 A Pt – Pt/13% Rd (type R) bare-junction thermocouple has an approximately spherical junction with a diameter of 0.3 mm. It is used to measure the temperature of gases in a combustion tunnel. When the flame is ignited, it produces an approximate step increase of the gas temperature of 900 K. The average heat-transfer coefficient on the surface of the thermocouple is 500 W/m 2 -ºC. The gas temperature before ignition is 300 K. Platinum has a density of 21,450 kg/m 3 and a specific heat of 134 J/kg-K. (a) Find the time constant of the thermocouple. (b) After how much time and how many time constants will the measurement error be less than 1% of the final temperature change? (c) If the same thermocouple is used in an aqueous environment in which the heat transfer coefficient is 6000 W/m 2 -ºC what will be the thermocouple time constant? (d) Plot the thermocouple response versus time for both cases. (on the same plot) solution:
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hw5soln - Solution Homework #5 Problem No. 1 A Pt Pt/13% Rd...

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