This preview shows page 1. Sign up to view the full content.
Unformatted text preview: 277 A 2kW resistance heater wire with a specified surface temperature is used to boil water. The center temperature of the wire is to be determined. Assumptions 1 Heat transfer is steady since there is no change with time. 2 Heat transfer is onedimensional since there is thermal symmetry about the center line and no change in the axial direction. 3 Thermal conductivity is constant. 4 Heat generation in the heater is uniform. 110 C r D Properties The thermal conductivity is given to be k = 20 W/m C. Analysis The resistance heater converts electric energy into heat at a rate of 2 kW. The rate of heat generation per unit volume of the wire is 3 8 2 2 wire W/m 10 455 . 1 m) (0.7 m) 0025 . ( W 2000 = = = = L r Q V Q g o gen gen & & & The center temperature of the wire is then determined from Eq. 271 to be C 121.4 = + = + = C) W/m. 20 ( 4 m) 0025 . )( W/m 10 455 . 1 ( C 110 4 2 3 8 2 k r g T T o s o & 240...
View
Full
Document
This note was uploaded on 01/14/2012 for the course PHY 4803 taught by Professor Dr.danielarenas during the Fall '10 term at UNF.
 Fall '10
 Dr.DanielArenas
 Thermodynamics, Resistance, Energy, Mass, Heat

Click to edit the document details