Heat Transfer Handbook part 91 pptx

TEMA has made some attempt to anticipate temperature differences by classifying fouling factors according to various process services.. In any event, fouling factors which are, in realit

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TABLE 11.6 Fouling Resistances of Various Gas, Vapor, and Liquid Streams

Liquid water streams Crude oil refinery streams Artificial spray pond water 1.75–3.5 Temperature ≈ 120°C 3.5–7 Boiler blowdown water 3.5–5.3 Temperature ≈ 120–180°C 5.25–7 Brackish water 3.5–5.3 Temperature ≈ 180–230°C 7–9 Closed-cycle condensate 0.9–1.75 Temperature> 230°C 9–10.5 Closed-loop treated water 1.75 Petroleum streams

Engine jacket water 1.75 Liquefied petroleum gases 1.75–3 River water 3.5–5.3 Natural gasolene 1.75–3.5

Treated boiler feedwater 0.9 Process liquid streams Treated cooling tower water 1.75–3.5 Bottom products 1.75–3.5 Industrial liquid streams Caustic solutions 3.5 Ammonia (oil bearing) 5.25 DEA solutions 3.5

Industrial organic fluids 1.75–3.5 Crude and vacuum liquids

Cracking and coking unit streams Light distillates and gas oil 3.5–5.3

Heavy coker gas oil 7–9 Vacuum tower bottoms 17.6 Heavy cycle oil 5.3–7 Industrial gas or vapor streams

Light-end processing streams Exhaust steam (oil bearing) 2.6–3.5 Absorption oils 3.5–5.3 Natural gas flue gas 9 Alkylation trace acid streams 3.5 Refrigerant (oil bearing) 3.5 Overhead gas 1.75 Steam (non-oil bearing) 9 Overhead liquid products 1.75

Overhead vapors 1.75 Reboiler streams 3–5.5 Chemical process streams

Natural gas 1.75–3.5

Stable overhead products 1.75

Source: Adapted from Chenoweth (1988).

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to specify a fouling factor for a particular process stream along with some range ofappropriate temperature differences TEMA has made some attempt to anticipate temperature differences by classifying fouling factors according to various process services The result is inexact, as there is much latitude in establishing a process

service In any event, fouling factors which are, in reality, fouling resistances are

given by TEMA and may be specified by other standards

Chenoweth (1990) provided a summary of the fouling resistances for various gas, vapor, and liquid streams A partial list ofhis fouling factors is given in Table 11.6

NOMENCLATURE

Roman Letter Symbols

Abp crossflow area for bypass, m2

cold-side flow area, m2

A CL centerline flow area, m2

Awt crossflow area for bypass, m2

separation or splitter plate thickness, m

distance between separation plates, m mean flow channel gap, m

capacity rate, W/K

coefficient, dimensionless

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C mc cold-side matrix wall capacity rate, W/K

C mh hot-side matrix wall capacity rate, W/K

C1 difference between shell inside diameter and outer tube limit, m

¯C c cold-side heat capacitance, W/kg· K

¯C h hot-side heat capacitance, W/kg· K

¯C m matrix material heat capacitance, W/kg· K

¯C mc cold-side matrix material heat capacitance, W/kg· K

¯C mh hot-side matrix material heat capacitance, W/kg· K

C∗ capacity rate ratio, dimensionless

c c contraction coefficient, dimensionless

counterflow coefficient, dimensionless

c m specific heat ofrotor, J/kg· K

c p specific heat at constant pressure, J/kg· K

c pc cold-fluid specific heat at constant pressure, J/kg· K

c ph hot-fluid specific heat at constant pressure, J/kg· K

parameter defined where used

D e equivalent diameter ofbypass lane, m

D o outer tube limit diameter, m

d o tube diameter (outside diameter), m

F logarithmic mean temperature difference correction factor,

dimensionless

F C crossflow tube fraction, dimensionless

F T transitional correction factor, dimensionless

F w fraction ofnumber oftubes in one window, dimensionless

mass velocity, kg/m2· s

Gch channel mass velocity, kg/m2· s

g c proportionality factor in Newton’s second law, dimensionless

h heat transfer coefficient, W/m2· K

h c cold-side heat transfer coefficient, W/m2· K

h dc cold-side fouling heat transfer coefficient, W/m2· K

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h dh hot-side fouling heat transfer coefficient, W/m2· K

h h hot-side heat transfer coefficient, W/m2· K

h i inside heat transfer coefficient, W/m2· K

h io inside heat transfer coefficient referred to outside surface,

W/m2· K

h iη annulus heat transfer coefficient corrected for the weighted fin

efficiency, W/m2· K

h o annulus heat transfer coefficient including the effect of

fouling, W/m2· K

I modified Bessel function of the first kind, dimensionless

J B correction factor for bundle bypass, dimensionless

J C correction factor for baffle cut, dimensionless

J L correction factor for baffle leakage, dimensionless

J R correction factor for temperature gradient, dimensionless

j h heat transfer parameter, dimensionless

k m thermal conductivity ofmetal, W/m· K

tube length, m length ofplate, m

Lbi baffle spacing at inlet, m

Lbo baffle spacing at outlet, m

L∗

i baffle spacing parameter, dimensionless

L∗

o baffle spacing parameter, dimensionless

LMTD logarithmic mean temperature difference, K

fin performance factor, m−1

˙m b bypass path mass flow rate, kg/s

˙m c cold-fluid mass flow rate, kg/s

crossflow path mass flow rate, kg/s

˙m cr total crossflow mass flow rate, kg/s

˙m h hot-fluid mass flow rate, kg/s

˙m l leakage path mass flow rate, kg/s

˙m s shell-to-baffle leakage path mass flow rate, kg/s

˙m T total mass flow rate, kg/s

˙m t tube-to-baffle leakage path mass flow rate, kg/s

N cc group oflength terms, dimensionless

Ncf number of transfer units for counter flow, dimensionless

N CL number oftubes on shell centerline, dimensionless

N cw number oftubes crossed in one window, dimensionless

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N ss number ofsealing strip pairs, dimensionless

Ntu number ofheat transfer units, dimensionless

Ntu,c number ofheat transfer units based on cold side,

dimensionless

Ntu,o overall number ofheat transfer units, dimensionless

n b flow resistance ofbypass path, N· s/m2· kg

n c number oftubes crossed, dimensionless

flow resistance ofcrossflow path, N· s/m2· kg

n cr flow resistance oftotal crossflow path, N· s/m2· kg

n cw number oftubes crossed in one window, dimensionless

n i number offins on inside, dimensionless

n o number offins on outside, dimensionless

number ofin-line pass partitions, dimensionless

n s flow resistance ofshell-to-baffle leakage path, N· s/m2· kg

n t flow resistance oftube-to-baffle leakage path, N· s/m2· kg

number oftubes, dimensionless

ntw number oftubes in one window, dimensionless

n w flow resistance ofwindow path, N· s/m2· kg

n we exit space window flow resistance, N· s/m2· kg

n1 number ofstacks, side 1 ofheat exchanger, dimensionless

n2 number ofstacks, side 2 ofheat exchanger, dimensionless

Nud Nusselt number based on diameter, dimensionless

Nuch channel Nusselt number, dimensionless

P cold-side effectiveness, dimensionless

perimeter ofpassage, m pressure, N/m2or Pa

P W1 wetted perimeter for one channel, m

∆P AB pressure loss fromA to B, N/m2or Pa

∆P b bypass path pressure loss, N/m2or Pa

∆P c crossflow path pressure loss, N/m2or Pa

∆Pch channel pressure loss, N/m2or Pa

∆P cr total crossflow path pressure loss, N/m2or Pa

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∆P e end-space pressure loss, N/m2or Pa

∆P f friction pressure loss, N/m2or Pa

∆P l leakage path pressure loss, N/m2or Pa

∆P n1 pressure loss at inlet nozzle, N/m2or Pa

∆P n2 pressure loss at outlet nozzle, N/m2or Pa

∆Pport port pressure loss, N/m2or Pa

∆P s shell-to-baffle path pressure loss, N/m2or Pa

∆P t turn pressure loss, N/m2or Pa

tube-to-baffle path pressure loss, N/m2or Pa

∆P w window pressure loss, N/m2or Pa

p porosity ofmatrix surface, dimensionless

Prw Prandtl number based on wall thermal properties,

dimensionless

tube pitch correction factor, dimensionless

thermal resistance, K/W

R c cold-side thermal resistance, K/W

R dc cold-side fouling thermal resistance, K/W

R dh hot-side fouling thermal resistance, K/W

R h hot-side thermal resistance, K/W

R io sum ofinternal resistances referred to the outside ofthe inner

pipe, K/W

R is sum ofinternal resistances referred to gross outside surface, K/W

r a area ratio, defined where used, dimensionless

r b area ratio, defined where used, dimensionless

r c area ratio, defined where used, dimensionless

r di inside fouling resistance, m2· K/W

r dio inside fouling resistance referred to tube outside, m2· K/W

r do outside fouling resistance, m2· K/W

r io inside film resistance referred to tube outside, m2· K/W

r mo pipe wall resistance referred to tube outside, m2· K/W

r o annulus film resistance referred to tube outside, m2· K/W

r oη annulus thermal resistance corrected for fouling, m2· K/W

r o refers to outside or annulus resistance with fouling, m2· K/W

r oη refers to outside or annulus resistance with fouling corrected

for overall efficiency, m2· K/W

Rec crossflow Reynolds number, dimensionless

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Red Reynolds number based on diameter, dimensionless

S annulus surface per unit length, m2/m

S b base or prime surface area, m2

S bi inside base surface area, m2

S bo outside base surface area, m2

S c cold side surface area, m2

S f i inside finned surface area, m2

S f o outside surface area, m2

S i inside surface area, m2

S m metal or matrix surface area, m2

S surface area per unit length of tube, m2/m

T mc cold-side matrix temperature, K

T mh hot-side matrix temperature, K

T2 outlet hot-fluid temperature, K

t1 inlet cold-fluid temperature, K

t2 outlet cold-fluid temperature, K

U overall heat transfer coefficient, W/m2· K

U c overall heat transfer coefficient referred to cold fluid,

W/m2· K

U h overall heat transfer coefficient referred to hot fluid, W/m2· K

width ofplate, m

Z parameter used in multistream arrangements, dimensionless

pass partition width, m

fin root width, m

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Greek Letter Symbols

ratio oftotal area on one side ofthe exchanger to the total volume on both sides ofan exchanger, m2/m3

packing density, m2/m3

ratio oftotal area on to the total volume on one side ofan exchanger, m2/m3

chevron angle, deg

γ correction factor for multipass arrangements, dimensionless

parameter defined where used, dimensionless

δf i inside fin thickness, m

δf o outside fin thickness, m

δov height ofbaffle overlap region, m

δsb shell-to-baffle spacing, m

δts tube-to-shell gap thickness, m

ηc cold-side fin efficiency, dimensionless

ηf i inside fin efficiency, dimensionless

ηf o outside fin efficiency, dimensionless

ηh hot-side fin efficiency, dimensionless

ηov overall efficiency, dimensionless

ηov,c cold-side overall efficiency, dimensionless

ηov,h hot-side overall efficiency, dimensionless

ηov,i inner or inside efficiency, dimensionless

ηov,o outer or outside efficiency, dimensionless

θm true temperature difference, K

θ1 angle between the horizontal and the point on the baffle edge

on the baffle cut, rad

θ3 twice the angle between the vertical and the intersection ofthe

baffle edge and the outer tube limit, rad

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 ratio oftransverse to longitudinal tube spacing, dimensionless

σ ratio of free flow area to frontal area, dimensionless

τdc cold-side dwell time, s

Φ parameter, defined where used, dimensionless

φ viscosity correction factor, dimensionless

φc cold-side face angle in a regenerator, rad

φh hot-side face angle in a regenerator, rad

φsh shield face angle in a regenerator, rad

φt total face angle in a regenerator, rad

correction factor, dimensionless

Subscripts

particular area ratio base or prime surface baffle

bulk temperature

crossflow tube fraction

centerline flow area

baffle cut cold fluid crossflow number oftubes crossed particular area ratio crossflow path

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diagonal dirt or fouling

dio inside fouling condition referred to outside

equivalent

flow

hot fluid hydraulic

mo metal condition referred to outside

outer tube limit

width ofbypass divider lane number ofpass partitions number ofbypass divider lanes

surface

shell-to-baffle spacing