Thermodynamics HW Solutions 332

Thermodynamics HW Solutions 332 - Chapter 4 Transient Heat...

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

View Full Document Right Arrow Icon
Chapter 4 Transient Heat Conduction 4-55E The center temperature of oranges is to be lowered to 40 ° F during cooling. The cooling time and if any part of the oranges will freeze during this cooling process are to be determined. Assumptions 1 The oranges are spherical in shape with a radius of r 0 =1.25 in = 0.1042 ft. 2 Heat conduction in the orange is one-dimensional in the radial direction because of the symmetry about the midpoint. 3 The thermal properties of the orange are constant. 4 The heat transfer coefficient is constant and uniform over the entire surface. 5 The Fourier number is τ > 0.2 so that the one-term approximate solutions (or the transient temperature charts) are applicable (this assumption will be verified). Properties The thermal conductivity and thermal diffusivity of oranges are given to be k = 0.26 Btu/h ft ⋅° F and α = 1.4 × 10 -6 ft 2 /s. Analysis First we find the Biot number: Bi Btu / h.ft . F) ft 0.26 Btu / h.ft. C 2 == ° ° = hr k 0 46 125 12 1843 (. (. / ) .
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/19/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.

Ask a homework question - tutors are online