HeatTransfer-I-Section-10

The distance between the ends is 40 cm determine the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: os θ i dA j dAi ȹ ∫∫ ȹ ȹ πR 2 ȹ Ⱥ Fij Ai = F ji A j € € € Fij is the view factor which defines the amount of radia%on leaving surface i which is intercepted by surface j. 26 Radia%on Heat Transfer •  View Factors can be calculated from the view factor integral or computed numerically. •  In most cases we use a catalog of view factor formulas or graphical representa%ons of the results. •  Only in advanced analysis do we calculate the view factors using this formula. •  We also u%lize view factor algebra to help deduce view factors for most systems. •  In most cases once a few view factors are known, we can solve for the rest using simple analysis. 27 Radia%on Heat Transfer •  View Factor Algebra: –  Two important rela%onships we use in determining view factors is the reciprocity property and the summa%on rule. Ai Fij = A j F ji Reciprocity N ∑F ij =1 Summation j=1 –  In general if we have N surfaces in an enclosure, we require N2 view factors. As a minimum N(N ­1)/2 view factors are € required. The remaining factors can be deduced using the above formulas. –  If a surface “sees itself”, i.e. concave, then Fii >0. Otherwise for flat or convex surfaces Fii = 0. 28 Radia%on Heat Transfer •  View Factors: 29 Radia%on Heat Transfer •  View Factors: 30 Radia%on Heat Transfer •  View Factors: 31 Radia%on Heat Transfer •  View Factors: 32 Example 3 •  A simple conical enclosure is the result of two parallel disks of diameter 10 cm and 25 cm which are connected with a third surface to form an enclosed system. The dista...
View Full Document

This document was uploaded on 02/14/2014 for the course ENGR 6901a at Memorial University.

Ask a homework question - tutors are online