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GATE ME 2021 || Heat-Transfer quiz 2 (App update required to attempt this test)
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Question 1
The value of Biot number is very small (<0.01) when __________.
Question 2
A body cools from 90 °C to 80°C in 5 minutes. Under the same external conditions to cool from 80 °C to 70 °C the body will take __________.
Question 3
Consider the following statements regarding fins:
(A). A fin is more effective if Biot number is less than one.
(B). A fin is less effective if Biot number is less than one.
(C). Fin will act as an insulation for a surface if h > mk.
(D). fin will enhance heat transfer if h > mk.
Which of the following statements are correct _________?
Question 4
A rectangular very long fin 20 × 5 × 2 cm3 is attached to the body of an automobile engine of 320° C temperature & surrounding temperature 30° C. If the convective heat transfer coefficient of surrounding air to 
conductivity of material of fin is 
Then the temperature gradient at the base of fin in (k/cm).
conductivity of material of fin is Then the temperature gradient at the base of fin in (k/cm).Question 5
A 1 cm diameter, 30 cm long fin made of aluminum (k = 237 W/moC) is attached to a surface at 80oC. The surface is exposed to ambient air at 22oC with heat transfer coefficient of 11 W/m2 °C. If the fin can be assumed as infinitely long, its efficiency is ___________.
Question 6
A steel ball of 10 mm diameter at 1000 K is required to be cooled to 350 K by immersing it in a water environment at 300 K. The convective heat transfer coefficient is 1000 W/m2‐K. Thermal conductivity of steel is 40 W/m-K. The time constant for the cooling process τ is 16 s. The time required (in s) to reach the final temperature is __________.
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Sep 2ESE & GATE ME
