radial t profile across wall separating hot & cold fluids 1

Radial T Profile Across Wall Separating Hot & Cold Fluids

1

D i

D o

T i

T c

T o

T h T w h

T w c

e n d v ie wo f s lic e

( in c lu d in go u te r s h e ll)

r

r i r o r

resi

stan

ce #

1

resi

stan

ce #

2

resi

stan

ce #

3

dL

o b liq u e v ie wo f s lic e o f in n e rp ip e w a ll

Sieder-Tate Equation(hi for turbulent flow inside pipes)

Nu Re Pr

1/30.8 0.14

0.023 pi ii i i i

i i i iwN N N

ch D GD

k k

Di

G

i i

Q mG v

S S

Shell-and-Tube Hxer

Example:* A steel mill needs to cool 3,000 gal/hr of a dilute acid from 200F to 130F using 5,000 gal/hr of 80F river water. A shell-and-tube heat exchanger is available (see description below). Determine if this heat exchanger is sufficient for this task.

Description of available heat exchanger:

type: 1-2

tubes: 158 1-inch, 14BWG stainless tubes, 16 ft long, stacked in 1¼ inch square pitch

baffles: 25% with 6 inch pitch

shell: 20 inch inside diameter, mild steel

* Shell&tube hxer example.mcd

Hxer Example Problem

BWG = Babcock & Wilcox Gauge

Example:* A steel mill needs to cool 3,000 gal/hr of a dilute acid from 200F to 130F using 5,000 gal/hr of 80F river water. A shell-and-tube heat exchanger is available (see description below). Determine if this heat exchanger is sufficient for this task.

Description of available heat exchanger:

type: 1-2

tubes: 158 1-inch, 14BWG stainless tubes, 16 ft long, stacked in 1¼ inch square pitch

baffles: 25% with 6 inch pitch

shell: 20 inch inside diameter, mild steel

* Shell&tube hxer example.mcd

Hxer Example Problem

Tube Pitch

Tube Pitch: the Dimension

Example:* A steel mill needs to cool 3,000 gal/hr of a dilute acid from 200F to 130F using 5,000 gal/hr of 80F river water. A shell-and-tube heat exchanger is available (see description below). Determine if this heat exchanger is sufficient for this task.

Description of available heat exchanger:

type: 1-2

tubes: 158 1-inch, 14BWG stainless tubes, 16 ft long, stacked in 1¼ inch square pitch

baffles: 25% with 6 inch pitch

shell: 20 inch inside diameter, mild steel

* Shell&tube hxer example.mcd

Hxer Example Problem

Baffle Pitch, P

sh e ll- s id e f lo w

tu b es id e

f lo w

P b a ff le s

tu b e sh e e ts

Baffle Plate & Baffle Window(25% Baffle Window)

Ds

end view side view

baffle window

25%baffleplate

Ds

4

holesfortubes

e b cG G G 2Kg

[ ]m s

bb

mG

S

c

c

mG

S

Effective Mass Velocity

2 2

area of blue region

4 4s o

b b bD D

S f N

Flow Area in Baffle Window

1 oc s

DS PD

p

total area = PDs

length of unit cell = p (tube pitch)

length which is open = p-Do

fraction open = (p-Do)/p = 1 - Do/p

Flow Area for Cross Flow

end viewside view

p

P

widestrow of

tubes

area forcross-flow(shaded yellow)

DsDo

Multipass Construction

sh e ll- s id e f lo w

tu b es id e

f lo w

P b a ff le s

tu b e sh e e ts

sh e ll- s id e f lo w

tu b es id e

f lo w

tu b e sh e e tssh e ll- s id e f lo w

tu b es id e

f lo w

tu b e sh e e ts

1 shell pass

1 tube pass

1 shell pass

2 tube passes

2 shell passes

2 tube passes

1-1 Hxer

1-2 Hxer

2-2 Hxer