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)