Railways Technical Ability Vibration Analysis Question Bank Vibration Analysis

  • question_answer Two long parallel surfaces, each of emissivity 0.7, are maintained at different temperatures and accordingly have radiation exchange between them. It is desired to reduce 75% of this radiant heat transfer by inserting thin parallel shields of equal emissivity (0.7) on both sides. What would be the number of shields?

    A) 1                                 

    B) 2

    C) 3                                 

    D) 4

    Correct Answer: B

    Solution :

    Heat transfer with shields \[=\left( \frac{1}{n+1} \right)\times \] Heat transfer without shields Where n = number of shields \[\frac{1}{n+1}=\frac{1}{4}\] Or n=3

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