Question

During air cooling of oranges, grapefruit, and tangelos, the heat transfer coefficient for combined convection, radiation, and evaporation for air velocities of 0.11<V< 0.33 m/s is determined experimentally and is expressed as h=5.05 kairRe13/D, where the diameter Dis 0.1 m. Oranges are cooled by refrigerated air at 5°C and 1 atm at a velocity of 0.3 m/s. Given: The thermal conductivity of the orange is given to be k = 0.50 W/m-°C. The thermal conductivity and the kinematic viscosity of air at the film temperature of (T, + Too)/2) = (15+5)/2 = 10°C are k = 0.02439 W/m.°C, v =1.426 x 10-5 m2/s. 4. value 3.00 points Required information Determine the value of the initial temperature gradient inside the orange at the surface. (Round the final answer to the nearest whole number.) The value of the initial temperature gradient at the orange surface is °C/m.

Answer 1

Film temperature Tf = Tsttcc 15+5 loc From table at loc Thermal Condoctivity of air Kair= 0.0244W/mok Dynamic viscosity of air U 1.426 x 10 105 mils Reynold's number Rez Vxo 0-3 Y 0.07 1.426x105 1472-65 convective coefficient Å 13 h 5.0 5x Kaire Ré 13 5.05x0.6244 x (1472-65 ) 0007 h=20.03 W/mk Surface Area TD Txoioi => 0.015 4 m Scanned by TapScanner

Initial temperature gradient acond alcony -> - Kx/&T dr h (Ts-Tic) 8=R lot ४४ 20.03 (15-5) 8=R 0.5 Control dr -400.6 °C/m 8=R Scanned by TapScanner