HW # 5 /Tutorial # 5 WWWR Chapter 20 ID Chapters 7-9

Tutorial # 5 WWWR #20.5, 20.12, 20.13, 20.41, 20.42. To be discussed during the week 17 Feb. – 21 Feb., 2014. By either volunteer or class list. Homework # 5 (Self practice). WWWR #20.6, 20.43, 20.45. ID# 7.24, 7.35. Correction: #20.42: Table: Unit for Cp should be corrected from J/kg-K to kJ/kg-K. HW # 5 /Tutorial # 5WWWR Chapter 20ID Chapters 7-9

Convective Heat Transfer Correlations

Natural Convection

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

Horizontal Cylinders g

q A = h(T1 - T2) 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

Example 1

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, 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 Rc Ri 295K Rc << Ro, Ri

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

=373-(373-300)*[98.1/(98.1+11400)] =372.3K

Example 3

Forced Convection For External Flow 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

HW # 5 /Tutorial # 5 WWWR Chapter 20 ID Chapters 7-9

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