• Introduction

• A condenser is a type of heat exchanger in which vapors are transferred into liquid state by removing the latent heat with the help of a coolant such as water.

• Condensers may be classified into two main types:1. Those in which the coolant and condensing vapor

are brought into direct contact.2. Those in which the coolant and condensate stream

are separated by a solid surface, usually a tube wall

Different types of the Condenser

1. Double pipe and multiple pipe 2. Plate Condensers3. Air-Cooled Condensers4. Compact Condensers5. Shell & tube type

DESIGN CALCULATIONS FOR CONDENSER

• Inlet temperature of the process stream ‘T1’ = 45 oC• Outlet temperature of the process stream ‘T2’ = 45 oC• Inlet temperature of the water ‘t1’ = 25 0C• Outlet temperature of the water ‘t2’ = 40 oC• Mass flow rate of the process stream ‘m’ = 8060 Kg/hr• Enthalpy of Vapors of Process Stream = 1940 KJ/Kg

Removed ‘λ1’

T2 = 45 oC

t1= 25 oC t2 = 40oC

T1 = 45 oC

Condenser

Heat Load: Q = m (λ1)

Q = 4343 KW

Mass flow rate of cooling water

ΔtC

Qm

p

= 68.9 Kg/sec

Log Mean Temperature Difference

LMTD = (t2-t1)/ log (t2/t1) LMTD = 14.4oC

Cp = 4.2 KJ / Kg.K

Assumed Calculations

Assumed Value of Overall Coefficient ‘UD’ = 1000 W/m 2C

True Mean Temperature Difference

Dimensionless Temperature Ratios R R = (T1-T2) / (t2-t1) = (45-45) / (40-25) = 0 S S = (t2-t1) / (T1-t1) = (40-25)/ (45-25) = 0.75

From Literature the value of Ft is 1

tm = Ft x LMTD = 1 x 14.4 = 14.4 oC

Heat Transfer Area

= 301 m 2

Surface Area of single tube = 3.14 x 19 x 4.88 / 1000 = 0.292 m 2 No. of tubes = 301/.292 = 1030 Pitch ‘Pt’ = 1.25 19.05= 23.8 mm

ΔtU

QA

D

Tube Bundle Diameter Db = d0 (Nt/K1)1/n1

= 19 (1030/0.158)1/2.263

= 920 mm

No. of tubes in centre row Nr = Db / Pt = 920 / 23.8 = 39Shell Side Calculations

Estimate tube wall temperature Tw

Assume condensing coefficient of 4250 W/m2C (from literature) Mean Temperature Shell side =( 45+45) / 2 = 45 oC Tube side = (25+40) / 2 = 32.5 oC (45-Tw) x 4250 = (45-25) x 1000 Tw = 40.3 oC

Physical Properties

Viscosity of the liquid ‘µL’ = 0.8 mNs/m2

Density of liquid ‘ρL’ = 993 Kg/m3

Thermal conductivity ‘kL’ = 0.571 W/m C Average M. Wt. of Vapors = 42.8 Density of vapor = 29 x 273 x 1/(22.4 x 1 x (273+42)) = 1.12 Kg / m3 Condensate loading on a horizontal tube ’Ѓh’ = m / L x Nt = 8060 / 3600 x (4.88 x 1030) = 4.45 x 10-3 Kg/m s # of tubes in the vertical row ’Nr’ = 2/3 x 39 = 26 mm Heat transfer coefficient in condensation

‘h0’ = 0.95 x kL ( ρL x (ρL – ρv ) g / (µL x Ѓh)1/3 x Nr-1/6

= 4396.0 W/m2оC• As our assumed value is correct so no need to correct the

wall temperature

Tube Side Calculations

Tube cross sectional area = 3.14 / 4 x (19 x 10-3)2 x 1030 / 4

= 0.073 m2

Density of water at 30 0C = 993 kg/m3 Tube velocity = m / (ρH2O x At )

= 68.9 / (993 x 0.073) = 0.95m/s Film heat transfer coefficient inside a tube ‘hi’ = 4200(1.35+0.02 x t) Vt0.8 / di

. 0 2

= 4809.67 W/m2 0C From Literature take fouling factor as 6000 W/m2 0C Thermal Conductivity of the tube wall material

‘Kw’ = 50 W/m0C

Overall Coefficient

1/U0 = 1/ho + 1/hod + (d0 ln(d0/di))/2kw +d0/di x 1/hid +d0/di x 1/hi

= 0.001 U0 = 1100.29 W/m2 0C

So assumed value is correct

Shell Side Pressure Drop

For pull through floating head with 45% cut baffles From literature clearance = 88 mm Shell internal diameter ‘Ds’ = Db+88

= 1008 mm Cross flow area ‘As’ = m2

A= 0.205 m2

Mass Velocity Gt = m / As

= 8060 / (3600 x 0.205) = 10.92 Kg/s m2

Equivalent diameter ‘de’ = 1.27 (Pt2 -0.785d0

2) / d0 = 19 mm Viscosity of vapors ‘’ = 0.009 mNs/m2

Reynold’s No. Re = de Gt / = 19 x 10-3 x 10.92 /0.009 x 10-3 Re = 23053

From literature jf = 0.029

By neglecting the viscosity correction factor

Where Ds = dia of shell L = Length of tubes lB = baffle spacing So = 765 N/m2 = 0.765 Kpa

= 0.109 Psi

Tube side pressure drop Viscosity of water ‘µ’ = 0.9 x 10-3 Ns/m2

Re = Vt ρ di /µ = 0.95 x 993 x 16.56 x 10-3 / 0.6 x 10-3

= 26036 From literature jf = 0.0039

Where Np = No. of tube passes

So ∆Pt = 4119.8 N/m2

= 4.119Kpa = 0.59 psi Acceptable

hio = hi I.D/O.D

hio = 4165.2 W/m2 0C

Clean Overall Coefficient:

= 2138.7 W/m2 0C

Design Overall Coefficient Calculated

dirt factor Rd = 0.0005

D

D

UU

UUR

C

Cd

oio

oioC hh

hhU

SPECIFICATION SHEET CONDENSERIdentification: Item condenserNo. Required = 8

Function: Condense vapors by removing the latent heat of vaporization

Operation: Continuous

Type: 1-4 Horizontal Condenser Shell side condensationHeat Duty = 4343 KW

Tube Side:Fluid handled: Cold WaterFlow rate = 68.9 Kg/secPressure = 14.7 psiaTemperature = 25 oC to 40 oC

Tubes: 0.75 in. Dia.1030 tubes each 16 ft long4 passes23.8 mm triangular pitchPressure Drop = 0.59 psi

Shell Side:Fluid handled = SteamFlow rate = 8060 Kg/hrPressure = 10 KPaTemperature = 45 oC to 45 oC

Shell: 39 in. dia. 1 passesBaffles spacing = 3.5 in.Pressure drop =0.109 psi

Utilities: Cold water

Ud assumed = 1000 W/m 2C Ud calculated =1100.97 W/m 2C

Rd = 0.0005

References

• Chemical Engineering DesignVolume 6 by Coulson &v Richardson’s

• Process Heat Transferby D.Q. Kern

• Plant Design & Economics for Chemical Engineers5th Edition by Max S. Peters, Klaus D. Timmerhaus, Ronald E. West

• Perry’s Chemical Engineers’ Handbookby Robert H. Perry, Don. W. Green