HW 5 Tutorial 5 WRF Chapter 19 WWWR

HW # 5 /Tutorial # 5 WRF Chapter 19; WWWR Chapter 20 ID Chapters 7 -9 • Tutorial # 5 • WRF#19. 3; WRF#19. 8; WWWR #20. 13, ; WRF#19. 23, WWWR#20. 42. • To be discussed during the week 17 Feb. – 21 Feb. , 2020. • By either volunteer or class list. • Homework # 5 (Self practice). • WRF#19. 4; WRF#19. 25 • ID# 7. 24, 7. 35. • Correction: #20. 42: Table: Unit for Cp should be corrected from J/kg-K to k. J/kg-K.

Convective Heat Transfer Correlations

Natural Convection

Horizontal Plates Mc. Adam’s Correlations: Hot surface facing up or cold surface surfacing down H C C H

Horizontal Cylinders g

In each of the correlations to follow the temperature of the hotter of the two large surfaces is designed in T 1, and the cooler surface is at temperature T 2. Fluid properties are evaluated at the film temperature, Tf = (T 1 + T 2) / 2. Convective heat flux is expressed as q = h(T - T ) 1 2 A

Example 1

H H

Initial Guess T = 385 K, Resulting T=381. 1 K Second Iteration

Forced Convection For Internal Flow

Turbulent Flow

Example 2 Hydraulic fluid (MIL-M-5606), in fully developed flow , flows through a 2. 5 cm diameter copper tube that is 0. 61 m long, with a mean velocity of 0. 05 m/s. The oil enters at 295 K. Steam condenses on the outside tube surface with an effective heat transfer coefficient of 11400 W/m 2 -K. Find the rate of heat transfer to the oil. Ro Rc 295 K Ri Rc << Ro, Ri

Ro Example 2 Rc 295 K =(295+305)/2 Ri 305 K? Rc << Ro, Ri

=373 -(373 -300)*[98. 1/(98. 1+11400)] =372. 3 K

Example 3

Forced Convection For External Flow Parallel To Plane Surface

Cylinders In Crossflow

Tube Banks In Crossflow SL : Center-to-center distance between tubes along the direction of flow ST: Center-to-center distance between tubes normal to the direction of flow

Adapted from ID Page 437