Supervised by : Dr. mohammad fahim Eng. Yousef ali Yaqoub bader ali.
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Transcript of Supervised by : Dr. mohammad fahim Eng. Yousef ali Yaqoub bader ali.
Supervised by:
Dr. mohammad fahimEng. Yousef ali
Yaqoub bader ali
agenda
Heat exchanger design
Alkylation reactor design
Pump design
Heat exchanger design
Heat exchanger are component that allow the transfer of heat from one fluid to another fluid without direct contact between them.
The heat is transferred from the hot fluid to the metal isolating the two fluids and then to the cooler fluid.
Types of heat exchanger
Shell and tube heat exchangerFloating head heat exchanger type:
:Heat loadQh = Mh Cp (T1-T2)
where: Qh = heat load in the hot side (KW)
Mh = mass flowrate of hot fluid (Kg/h) Cp = heat capacity of hot fluid
(kJ/kgoC) T1 = inlet temperature (oC)
T2 =outlet temperatue (oC)
Log mean temperature:∆Tlm =(T1-t2)-(T2-t1) / ln((T1-t2)/(T2-t1))
where: ∆Tlm = log mean temperature differace
T1 = inlet shell side fluid temoerature (oC)
T2 = outlet shell side fluid temerature (oC)
t1 = inlet tube side temoerature (oC)
t2 = outlet tube side temerature (oC)
Temperature correction factor Ft:
Take one shell pass ; two tube or more even tube pass.
∆Tm = Ft ∆Tlm
where: ∆Tm = true temperature difference Ft = the temperature correction
factor ∆Tlm = log mean temperature differace
Heat transfer area
A= Q / U ∆Tm
where: A = provisional area (m2) Q = heat load (kW) U = overall heat transfer coefficient
(W/m2 oC)U is assumed
Bundle diameter: Ds = Db + Bundle diametrical clearance
(from fig.).
Db = (do)*( Nt / K1)^ (1/n1)
Where: Db =bundle diameter (mm)
do = outer diameter (mm)
Nt : number of tubes K1 & n1 are constantAssume inner , outside diameters of the
tubes
Tube layout
•Take triangular pitch Pt=1.25d0
•take No. passes for tubes = 8
:Inside coefficient hi
i^0.2)ut^0.8)/(d *0.02t)(1.35 *(4200 hi
*/
sec//
25.0
#/
#
2
DensityPassArea
FlowRateuvelocity
areatoncrossPasstubespassArea
dareaSectioncross
sesAssumedPas
tubesPassTubes
ubeareaOfOneT
totalAreatubes
LdubeAreaOfOneT
t
i
o
Types of baffles:
•Type: single segmental.
• Choose baffle spacing (Lb)= (Ds/5)
Shell side coefficient
hs = kf * jh *Re *Pr^(1/3) / de
Where:
de=equivalent diameter.jh=heat transfer factor.
Over all heat transfer coefficient:
Where: Uo: overall heat transfer coefficient hi: inside heat transfer coefficient ho: outside heat transfer coefficient do: outer diameter di: inner diameter Kw: wall thermal conductivity
ii
o
w
i
oo
oo hd
d
k
ddd
hU
1
2
ln11
Pressure drop (tube side):ΔPt = Np [ 8jf (L/di)(µ/µw)^(-m) +2.5 ] ρut²/2
where : ΔPt = tube side pressur drop (N/m²)(pa)
Np = number of tube side passes
ut = tube side velosity (m/s) L = length of one tube
Pressure drop (shell side):ΔPs = 8jf (Ds/de)(L/Lb)( ρus^2/2)(µ/µw)^(-
0.14)
where : L : tube length Lb : baffle spacing
Thickness calculation:
t =(Pri/(SEJ-0.6P))+Cc where: t = shell thichness (in) P = Maximum allowable internal pressure
(psig)ri = internal raduis of shell before allowance
corrosion is added (in)EJ = efficincy of joients S = working stress (psi)Cc = allowance for corrosin (in)
Reactor design• Chemical reactors are vessels designed to contain
chemical reactions.
Batch• No flow of material in or out of reactor• Changes with time
Continuous• Flow in and out of reactor• Continuous Stirred Tank Reactor (CSTR)• Plug Flow Reactor (PFR)• Steady State Operation
Fixed bed catalytic rector design
•Main reaction:
C6H6 + C2H4 → C6H5CH2CH3
•Liquid phase alkylation of benzene to ethylbenzne (exothermic reaction).
•Limiting reactant:
Ethylene
Fixed bed catalytic rector design
Design equation:
Rate law:
Concentration:
)1/( KcCckrCarA
)(0 xCC iAi
0A
A
F
r
dW
dx
Fixed bed catalytic rector design
The change in the number of moles per mole of A reacted is:
0A
Ai
y
y
Fixed bed catalytic rector design
Volume of cylindrical part of reactor:
Length and diameter of cylindrical part of reactor:
(assume L/D)
bulk
catWcolumnV
)1()(
LDV 2
4
Fixed bed catalytic rector designVolume of spherical head:
V= (4/3)*( )*(Л D/2)³
Total volume of the reactor:
V (total)= Volume of spherical head + Volume of cylindrical part of reactor
Fixed bed catalytic rector design
Assume space between two bed.Height of the reactor:
H= length of cylindrical part of reactor +(2*space between bed)
Area of the reactor:
A=V (total)/H
Fixed bed catalytic rector designReactor thickness:
t =(Pri/(SEJ-0.6P))+Cc where: t = shell thickness (in) P = Maximum allowable internal pressure (psig) ri = internal radius of shell before allowance
corrosion is added (in)EJ = efficiency of joints S = working stress (psi)
Cc = allowance for corrosion (in)
Pump designPump is a device that move fluid from low level to high level.
Pump designActual head of pump :
g
ppha
12
P1 (Initial pressure)P2 (Final pressure).ρ is the density.g (Gravity).ha is the head of pump.
Pump designWater horse power:
550a
f
QhP
Q (volumetric rate).Pf is the water horse power (hp).
Pump designOverall efficiency :
BHP
WHP
WHP is the horse power (hp). BHP is the brake horse power (hp)