11.8 A chromel-alumel thermocouple junction, which can be approximated with a sphere, has an effective diameter of 1 mm. It is used to measure the temperature of a gas flow with an effective heat-transfer coefficient of 500 W/m²-°C. (a) Determine the time constant of this thermocouple. (b) If the gas temperature suddenly increases by 100°C, how long will it take the thermo- couple to attain a temperature rise within 1% of the gas temperature rise? (c) Find the answer to the previous questions if the diameter of the bead is doubled. (Assume that the heat-transfer coefficient remains the same.)

11.8 A chromel-alumel thermocouple junction, which can be approximated with a sphere, has an effective diameter of 1 mm. It is used to measure the temperature of a gas flow with an effective heat-transfer coefficient of 500 W/m²-°C. (a) Determine the time constant of this thermocouple. (b) If the gas temperature suddenly increases by 100°C, how long will it take the thermo- couple to attain a temperature rise within 1% of the gas temperature rise? (c) Find the answer to the previous questions if the diameter of the bead is doubled. (Assume that the heat-transfer coefficient remains the same.)

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter10: Heat Exchangers

Section: Chapter Questions

Problem 10.51P

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