A thermocouple, with a spherical junction diameter of 0.5 mm, is used for measuring the temperature of hot air flow in a circular duct. The convection heat transfer coefficient of the air flow can be related with the diameter (D) of the spherical junction and the average air flow velocity (V) as h = 2.2(V/D)0.5, where D, h, and V are in m, W/m2?K and m/s, respectively. The properties of the thermocouple junction are k = 35 W/m?K, r = 8500 kg/m3, and cp = 320 J/kg?K. Determine the minimum air flow velocity that the thermocouple can be used, if the maximum response time of the thermocouple to register 99 percent of the initial temperature difference is 5 s.

A thermocouple, with a spherical junction diameter of 0.5 mm, is used for measuring the temperature of hot air flow in a circular duct. The convection heat transfer coefficient of the air flow can be related with the diameter (D) of the spherical junction and the average air flow velocity (V) as h = 2.2(V/D)0.5, where D, h, and V are in m, W/m2?K and m/s, respectively. The properties of the thermocouple junction are k = 35 W/m?K, r = 8500 kg/m3, and cp = 320 J/kg?K. Determine the minimum air flow velocity that the thermocouple can be used, if the maximum response time of the thermocouple to register 99 percent of the initial temperature difference is 5 s.

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter19: Temperature, Thermal Expansion And Gas Laws

Section: Chapter Questions

Problem 40PQ: On a hot summer day, the density of air at atmospheric pressure at 35.0C is 1.1455 kg/m3. a. What is...

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