Transcript BASIC HEAT TRANSFER - Armstrong International

®
Basic Heat Transfer Concepts
©2006 Armstrong International, Inc.
Basic Heat Transfer Concepts
TAir
TSteam
Tsteam >>> TAir
And Their Relationships to Heating Coil
Selection
®
“Expect many enjoyable experiences!”
David M. Armstrong
2
Heat Transfer
• Only occurs when there is a temperature
difference
• Flows faster when this difference is higher
• Always flows from high to low temperature
• Is greater with greater surface area
• Some materials transfer heat better than others
®
“Expect many enjoyable experiences!”
David M. Armstrong
3
Heat Flows from High to Low
TAir
TSteam
Tsteam >>> TAir
®
“Expect many enjoyable experiences!”
David M. Armstrong
4
Thermal Conductivity of Common Coil
Materials
Material
Thermal Conductivity
Copper
2724
Aluminum
1536
Steel
314
Cupro-Nickle 90/10
310
Cupro-Nickle 70/30
200
Stainless Steel
108
®
“Expect many enjoyable experiences!”
David M. Armstrong
5
To Get More Heat Transfer From Bare
Tubes . . .
Add Fins to Increase Surface Area
®
“Expect many enjoyable experiences!”
David M. Armstrong
6
Relative Heat Transfer:
Identical Coils w/Different Tube Materials
Tube Material
Relative HT Capacity
Copper
1.00
Aluminum
1.00
Steel
0.98
Stainless Steel
0.95
®
“Expect many enjoyable experiences!”
David M. Armstrong
7
Relative Heat Transfer:
Identical Coils w/Material Combinations*
Tube Material
Fin Material
Relative HT
Capacity
Steel
Copper Keyfin
1.05
Steel
Aluminum Keyfin
1.00
Stainless Steel
Aluminum Keyfin
0.94
Steel
Steel L Fin
0.92
Stainless Steel
Stainless Steel L Fin
0.58
*At 800 FPM, 7FPI & 55 psig
®
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David M. Armstrong
8
Heat Transfer Equation
Q = U x A x LMTD
where
Q = Heat Transfer Rate (BTU/hr)
U = Heat Transfer Coefficient (BTU/hr/ft2/F)
A = Surface Area (ft2)
LMTD = Log Mean Temperature Difference
(b/w the Steam and the Air)
®
“Expect many enjoyable experiences!”
David M. Armstrong
9
Assembly Concepts
®
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David M. Armstrong
10
©2002 Armstrong International, Inc.
Bare Tube Coils
Heat Exchange = U x Surface Area x T
Surface Area 1'' Pipe = 1 Sq Ft / Linear Ft
®
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David M. Armstrong
11
Extended Surface Coils
Fin Element
Plate Fin
Wound Fin
Fin Area >>>>> Tube Area
Tube is Irrelevant in Heat Transfer
®
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David M. Armstrong
12
Coil Construction
1 Inch
4 FPI
7 FPI
4 Tubes in the Face
6 Tubes in the Face
Steam
Conn.
Cond.
Conn.
Finned Tube
Cond.
Header
Steam
Header
1, 2, and 3 Row Coils
®
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David M. Armstrong
13
Casings and Air Baffles
Coil
Casings
Flanges
Casing Depth
Mounting
Holes
Side
Baffle
Header
Baffle
Air
Baffles
®
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David M. Armstrong
14
Coil Casing Types
Turned-Out Flange
Standard Flange for Duct-Mounted
Coils
Turned-In Flange
Used w/ Removable Coils or
Where mounting holes are not
needed & smooth casing face is
wanted
1-1/2”
3/4”
7/16"
Dimensions & Spacing
®
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David M. Armstrong
15
Removable (Drawer) Coils
Bolt Holes
Lifting Lug
Mounting Plate
• Core installed in a casing w/ flanges on 3 sides and a
mounting place on the 4th side
• Coil slides into outer casing like a drawer
®
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David M. Armstrong
16
Coil Configuration
Horizontal Air Flow
Horizontal Tubes
Steam
Condensate
Air
Inlet
Air
Outlet
Vertical Tubes
®
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David M. Armstrong
17
Coil Configuration
Air Outlet Side
Vertical Up Air Flow
Horizontal Tubes
Air Inlet Side
Air Inlet Side
Vertical Down Air Flow
Horizontal Tubes
Air Outlet Side
®
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David M. Armstrong
18
Parallel Multiple Coils
®
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David M. Armstrong
19
Series Multiple Coils
Steam Supply End
Air
Flow
Condensate Return End
®
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David M. Armstrong
20
Multiple Coil Installation
4 Coils in Parallel x 3 Coils in Series
• Common steam supply OK
• 12 Coils Total
• Drain each coil separately
• 12 Traps may discharge to common Header
®
“Expect many enjoyable experiences!”
David M. Armstrong
21
Heavy Duty Construction
Min. 0.016” Thick Fins
on 12 Ga. CS 0.109” Thick Tubes
12 Ga. Casing and Baffles
Sch 80 Connections
Sch 40 Headers
250 psig Standard Pressure Rating
®
“Expect many enjoyable experiences!”
David M. Armstrong
22
Heavy Duty Construction
• Header, Connections &
Tubes (wetted parts)
Same Material
• No Galvanic Corrosion
• All Joints Welded
• No Leaks
• Thicker Materials
• Fights Corrosion
®
“Expect many enjoyable experiences!”
David M. Armstrong
23
Model Number Selection
Extended Surface (Fin Tube) Heating
Coils
Which Fin Type?
Standard KeyFin
• Tight joint over wide
temperature range
• Best for dissimilar tube
and fin materials
®
“Expect many enjoyable experiences!”
David M. Armstrong
26
Which Fin Type?
L-Fin
• L-shaped foot tension wound
over knurled tube
• Best for same material tubes &
fins
• Large contact area for high
heat transfer
• Some corrosion protection for
tube
®
“Expect many enjoyable experiences!”
David M. Armstrong
27
Tube Materials
Carbon Steel
Affords both strength & corrosion resistance
Standard
Optional
12 Ga A-214 ERW (1” or 1½” OD)
10 Ga A-214 ERW
10 Ga or 12 Ga A-179 Seamless
Stainless Steel (304L or 316L)
When corrosive steam is present or when ideal piping &
trapping practices cannot be followed
14 Ga (1” OD) & 12 Ga (1½” OD)
®
“Expect many enjoyable experiences!”
David M. Armstrong
28
Fin Materials
Steel Fins stand up against aggressive cleaning
0.024” Thick on 1” OD or 1 1/2” OD Tubes
0.036” Thick on 1 ½” OD Tubes
Aluminum Fins provide the best overall value
0.020” Thick Keyfin on all Tube Sizes
0.030” Thick Keyfin on all Tube Sizes
Stainless Steel Fins fight high external corrosion
0.020” Thick Type 304L & 316L on 1” OD Tubes
Copper Fins provide the best heat transfer
0.016” Thick on All Tube Sizes
®
“Expect many enjoyable experiences!”
David M. Armstrong
29
Conns/Headers/Casing
Headers
Same Material As Tubes With Welded Construction
Connections
Steel: Sch 80 (screwed) or Sch 40 (flanged)
Stainless Steel: Sch 40 (screwed) or Sch 10 (flanged)
Casing
12 Ga. Galvanized Steel or 12 Ga Stainless Steel
®
“Expect many enjoyable experiences!”
David M. Armstrong
30
Coil Type
• Standard (Type S)
• Centifeed (Type C)
• Tendam (Type T)
• Centifeed Tandem (Type P)
®
“Expect many enjoyable experiences!”
David M. Armstrong
31
AIR FLOW
Type S coils are available with
opposite-end connections only
Type C coils are available with
same-end connections only
AIR
FLOW
2-Row Standard Coil
2-Row Centifeed Coil
AIR FLOW
Type T coils have
opposite-end connections
Type P coils have
same-end connections
Armstrong Promise
We provide intelligent system solutions that
improve utility performance, lower energy
consumption, and reduce environmental
emissions . . . while providing an “enjoyable
experience”!
®
“Expect many enjoyable experiences!”
David M. Armstrong
35
®
®
“Expect many enjoyable experiences!”
David M. Armstrong