# Repeat Prob. 685 for an air-flow velocity of 10 m/s. Data from problem 85 A metallic airfoil of elliptical cross

## Question:

Repeat Prob. 6–85 for an air-flow velocity of 10 m/s.

**Data from problem 85**

A metallic airfoil of elliptical cross section has a mass of 50 kg, surface area of 12 m^{2}, and a specific heat of 0.50 kJ/kg · K. The airfoil is subjected to air flow at 1 atm, 25°C, and 5 m/s along its 3-m-long side. The average temperature of the airfoil is observed to drop from 160°C to 150°C within 2 min of cooling. Assuming the surface temperature of the airfoil to be equal to its average temperature and using momentum-heat transfer analogy, determine the average friction coefficient of the airfoil surface.

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**Related Book For**

## Heat And Mass Transfer Fundamentals And Applications

**ISBN:** 9780073398181

5th Edition

**Authors:** Yunus Cengel, Afshin Ghajar

**Question Details**

Chapter #

**6**- FUNDAMENTALS OF CONVECTIONSection: Problems

Problem: 86

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