Results of Kern Method

Basic Kinematic Details

Group No.

Tube Side

Velocity (m/s)

Number of Tubes

Shell Diameter

length STHX

(m)

Ds/L

1

2

3

4

5

Performance Details

Group No.

Number of Tubes

Tube side Re

Shell side Re

Tube side h

(W/m2.K)

Shell side h

(W/m2.K)

1

2

3

4

5

Performance Details

Group No.

Tube side p, Pa

Shell side p, kPa

Uclean Ufouled

1

2

3

4

5

Actual Shell Side Heat Transfer Coefficient :Bell-Delaware Method

P M V SubbaraoProfessor

Mechanical Engineering Department

I I T Delhi

Five corrections to Cross Flow Heat Transfer…..

Shell-side heat transfer coefficient

Where hi is heat transfer coefficient for ideal cross flow past a tube bank.

Jc : Segmental baffle window correction factor Jl : Correction factors for baffle leakage effects for heat transferJb : Correction factors for bundle bypass effects for heat transfer Js : Heat transfer correction for unequal baffle spacing at inlet and/or outlet.Jr : correction factor for adverse temperature gradient in laminar flow

rsblcis JJJJJhh

Heat transfer coefficient for Ideal Cross Flow

14.0

,

32

ws

s

sps

s

m

spsii C

k

S

mCjh

Area for Ideal Cross Flow

Selection of Shell Diameter

A simple but reasonably accurate correlation was developed by Bell’s Group for single pass.

2

278.0

T

ctltubes PCL

DN

CL is tube layout constant , CL =0.87 for 30º and 60º layouts or CL=1.0 for 45º and 90º layouts.

For multipass arrangement, a correction factor ψn must be used to account for the decrease of tube count due to tube pass

2Re33.1

1a

s

a

o

Ti

dP

aj

Where 43

Re14.01 as

aa

2Re33.1

1b

s

b

o

Ti

dP

bf

Where 43

Re14.01 bs

bb

s

outertube

s

ss

d

A

m

Re

Shell-Side Reynolds Number

14.0

,

32

ws

s

sps

s

m

spsii C

k

S

mCjh

Coefficients of Correlations

Baffle Geometry

Segmental baffle window correction factor, Jc

cc FJ 72.055.0

2

sin

3602121 ctlctl

twC FF

Segmental Baffle Cut Geometry

Segmental baffle cut height :Lbch

Recommended segmental baffle cut values

Jl : Correction factors for baffle leakage effects for heat transfer

Ssb is the shell-to-baffle leakage area.

Stb is the tube-to-baffle hole leakage area.

Sm is the cross flow area at the bundle centerline

Shell-to-baffle leakage area

• The shell-to-baffle leakage area within the circle segment occupied by the baffle is calculated as:

Lsb is the diametral leakage clearance between the shell diameter and the baffle diameter, Db .

Tube-to-baffle hole leakage area for one baffle

The total tube-to-baffle leakage area within one baffle is Stb.

Correction factors for bundle bypass effects for heat transfer Jb, and pressure drop Rb

ptlotlsb LDDBS m

bsbp S

SF

Lptl =0 for single pass

Unequal Baffle Spacing

Heat transfer correction for unequal baffle spacing at inlet and/or outlet, Js

n is approximately a constant, found to be 0.6 for laminar flow and 0.333 for turbulent flow.

If L* is larger than 2, it would be considered poor design, especially if combined with low Nb .

In such cases an annular distributor or other measures should be used.

Heat transfer correction factor for adverse temperature gradient in laminar flow

where Nc is the total number of tube rows crossed in the entire heat exchanger:

Shell side Fluid Flow in STHE