Example 4.13. A thermocouple junction is in the form of 8 mm diameter sphere. Properties ofmaterial are:40 W/M2°C.= 8000 kg/m³; k = 40 W/m°C and hThis junction is initially at 40°C and inserted in a stream of hot air at 300°C. Find:%3D420 J/kg°C; pC =(i) Time constant of the thermocouple;(ii) The thermocouple is taken out from the hot air after 10 seconds and kept in still air at30°C. Assuming the heat transfer coefficient in air 10 W/M²°C, find the temperature attainedby the junction 20 seconds after removing from hot air.(P.U.)

Given d=8 mm, cp=420J/kg.K ρ=8000kg/m3K=40 W/m.Kh=40W/m2Need to determine the time constant of…

Example 4.13. A thermocouple junction is in the form of 8 mm diameter sphere. Properties of material are: C = 420 J/kg°C; p = 8000 kg/m2; k = 40 W/m°C and h = 40 W/m2°C. %3D This junction is initially at 40°C and inserted in a stream of hot air at 300°C. Find: (i) Time constant of the thermocouple; (ii) The thermocouple is taken out from the hot air after 10 seconds and kept in still air at 30°C. Assuming the heat transfer coefficient in air 10 W/m2° C, find the temperature attained by the junction 20 seconds after removing from hot air. (P.U.)

Example 4.13. A thermocouple junction is in the form of 8 mm diameter sphere. Properties of material are: C = 420 J/kg°C; p = 8000 kg/m2; k = 40 W/m°C and h = 40 W/m2°C. %3D This junction is initially at 40°C and inserted in a stream of hot air at 300°C. Find: (i) Time constant of the thermocouple; (ii) The thermocouple is taken out from the hot air after 10 seconds and kept in still air at 30°C. Assuming the heat transfer coefficient in air 10 W/m2° C, find the temperature attained by the junction 20 seconds after removing from hot air. (P.U.)

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Question

Example 4.13. A thermocouple junction is in the form of 8 mm diameter sphere. Properties of
material are:
40 W/M2°C.
= 8000 kg/m³; k = 40 W/m°C and h
This junction is initially at 40°C and inserted in a stream of hot air at 300°C. Find:
%3D
420 J/kg°C; p
C =
(i) Time constant of the thermocouple;
(ii) The thermocouple is taken out from the hot air after 10 seconds and kept in still air at
30°C. Assuming the heat transfer coefficient in air 10 W/M²°C, find the temperature attained
by the junction 20 seconds after removing from hot air.
(P.U.)

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