## Solution for Engineering Heat Transfer 2nd Edition Chapter 6, Problem 1

by William S. Janna
196 Solutions 12 Chapters 16000 Studied ISBN: 9780849321269 5 (1)

# Chapter 6, Problem Example 1 : Example 6.1 A flat-plate solar collector...

Example 6.1

A flat-plate solar collector contains a number of copper tubes that are painted black to enhance the absorptance of thermal radiation from the sun. Consider one such copper tube that is 1/2 standard type M and is 3 m long. It conveys ethylene glycol at a volume flow rate of 3.25 x lo-" m Vs. The liquid enters the tube at a (bulk) temperature of 20°C. Determine the fluid outlet temperature and the tube-wall temperature at the outlet. Take the incident heat flux to be 2 200 W/m2.

## Step-By-Step Solution

Example 6.1

Solution

The heat flux is incident only on the upper surface of the tube. However, because of various effects such as reflection to the tube from the bottom of the collector, assuming a uniform heat flux over the entire tube is not too bad an approximation. Ethylene glycol or an ethylene glycol-water mix is often used as a working fluid because of its low freezing point.