This document provide a explaination, description of nomenclatures in the given formula list. Since some variables can be used differently for each course, this will help make sure that you totally understand what each variable really meant.
Thermal resistances:
𝐿 𝑟 1
𝑅= ln ( 2 ) 𝑅=
𝑟1 ℎ𝐴
𝑘𝐴 𝑅=
2𝜋𝑘𝐿
Dimensionless terms:
relative thickness
of the two 𝑐𝑝 𝜇 𝑣 momentum diffusivity
=> 𝜌𝑢 𝐿 &ℎ𝐿 significant length dimension that
is in the
boundary -
>
𝑃𝑟 = = 𝑅𝑒 = 𝑁𝑢 = direction of growth/thickness
layers in connection
𝑘 𝛼 Thermal diffusivity
- 𝜇 k ↳ Diameter of Cylinde
𝜇
where 𝑣 = 𝜌 and 𝛼 = 𝜌𝑐
𝑘 ↑ ratio of convection conduction b
x =
dynamic viscosity to
length of plate
𝑝
Colburn equation: heat traster system
I
Both and mass in the
𝑁𝑢 = 0.023 𝑅𝑒 0.8 𝑃𝑟 0.333
Range of application: 𝑅𝑒 > 10,000, 0.7 < 𝑃𝑟 < 160 , 𝐷𝐿 > 60 , smooth pipes
Calculate Nu
Dittus-Boelter equation: Use for
heating or
cooling applications
to find "h" 𝑁𝑢 = 0.023 𝑅𝑒 0.8 𝑃𝑟 𝑛
where 𝑛 =0.4 for heating, 0.3 for cooling.
Range of application: 𝑅𝑒 > 10,000, 0.7 < 𝑃𝑟 < 160 , 𝐷𝐿 > 60 , smooth pipes.
Sieder and Tate equation: Take viscosity into account Cuse when Hoid's viscosity change significantly with terp (
&
𝜇𝑏 0.14 My =
dynamic viscosity of bullo frid cinside the
pipe)
𝑁𝑢𝑚 = 0.027 𝑅𝑒𝐿0.8 𝑃𝑟 0.333
(𝜇 ) Mw =
dynamic viscosity of fluid near the wall Con outer surface of the pipel
𝑤
Range of application: 𝑅𝑒 > 10,000, 0.7 < 𝑃𝑟 < 16,700 , 𝐷𝐿 > 60 , smooth pipes
Heat transfer with phase change: Meg at Tsat
= Film condensation & properties at To
,
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