HW # 5 /Tutorial # 5 WRF Chapter 19; WWWR Chapter 20 ID ... · , flows through a 2.5 cm diameter copper tube that is 0.61m long, with a mean velocity of 0.05 m/s. The oil enters at

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 15 Feb. – 19 Feb., 2021.

• By either volunteer or class list.

• Homework # 5 (Self practice).

• WRF#19.4; WRF#19.24; WRF#19.25

• ID# 7.24, 7.35.

• Correction: #20.42: Table: Unit for Cp should be corrected from J/kg-K to kJ/kg-K.

Convective Heat Transfer

Correlations

Natural Convection

Horizontal Plates

McAdam’s Correlations: Hot surface facing up or cold surface surfacing down

H

C

H

C

Horizontal Cylinders

g

In each of the correlations to follow the temperature of the hotter of

the two large surfaces is designed in T1, and the cooler surface is at

temperature T2.

Fluid properties are evaluated at the film temperature,

Tf = (T1 + T2) / 2.

Convective heat flux is expressed as

q

A= h(T1 - T2)

Example 1

H

H

Initial Guess T = 385K, Resulting T=381.1K 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 0.61m long,

with a mean velocity of 0.05 m/s. The oil enters at 295K. Steam

condenses on the outside tube surface with an effective heat transfer

coefficient of 11400 W/m2-K. Find the rate of heat transfer to

the oil.

Ro

RiRc

Rc << Ro, Ri295K

Example 2

Ro

Ri

=(295+305)/2

Rc

Rc << Ro, Ri295K

305K?

=373-(373-300)*[98.1/(98.1+11400)]

=372.3K

Example 3

Forced Convection For External

FlowFlow 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