Post on 07-Mar-2018
transcript
Process Heat GroupMajor Challenges
Lecture 222.033/22.33 Nuclear Engineering Design Project
September 14, 2011
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 1
The Three Challenge Problems
Heat exchanger (Hx) design Heat transport Heat storage (if necessary)
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 2
http:22.033/22.33
First, Some Nomenclature
Sensible heating temperature change .
Q = m c p T Latent heating phase change
. Q = m h fg
Bond energy storage enthalpy of chemical reactions
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 3
http:22.033/22.33
Where Do We Find Them?
Courtesy of the Generation IV International Forum. Used with permission.
Source: http://www.gen-4.org/Technology/systems/gfr.htm
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 4
http://www.gen-4.org/Technology/systems/gfr.htmhttp:22.033/22.33
Heat Exchangers Fundamental Parameters
Hx effectiveness () Measures how
much heat is transferred compared to how much is possible
=1 is ideal, but American Institute of Physics. All rights reserved. This content is excluded from ourCreative Commons license. For more information, see http://ocw.mit.edu/fairuse. practically
Source: Dean Bartlett. The Fundamentals of Heat Exchangers The Industrial Physicist, AIP, p. 20 (1996) impossible (big Hx)
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 5
http:22.033/22.33http://ocw.mit.edu/fairuse
Heat Exchangers Fundamental Parameters
Diagram of heat exchanger removed due to copyright restrictions. See lecture video for details.
***Source: Ramesh K. Shah, Dusan P. Sekulic. Fundamentals of Heat Exchanger Design. John Wiley & Sons, Inc. p. 102 (2003).
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 6
http:22.033/22.33
Heat Exchangers Fundamental Parameters
Q = UAFTlm Q = Heat transfer rate (W)U = Thermal conductance (W/m2K)A = Heat transfer area (m2)Tlm = Log mean temperature difference (K)
F = Factor (for flow configuration)
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 7
http:22.033/22.33
Heat Exchangers Log Mean Temperature Difference (LMTD)
( TH TC ) T = lm ln
TH TC
LMTD is a good measure of the effectiveness of simlar heatexchangers of different designs
Often, LMTD (counter flow) > LMTD (parallel flow)
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 8
http:22.033/22.33
Heat Exchangers Finding Key Parameters
Figure 1 A big, complicated heatexchanger chart
Source: Wolverine Tube Heat Transfer Data Book, p. 93 (2001), accessed at
http://www.wlv.com/products/databook /ch2_5.pdf
Courtesy of Wolverine Tube, Inc. Used with permission.
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 9
http://www.wlv.com/products/databook/ch2_5.pdfhttp://www.wlv.com/products/databook/ch2_5.pdfhttp:22.033/22.33
Heat Exchangers Fundamental Parameters
For all flow configurations
Hx is balanced when C* = 1
NTU = Number of Transfer Units John Wiley & Sons, Inc. All rights reserved. This content is excluded from our CreativeCommons license. For more information, see http://ocw.mit.edu/fairuse.
***Source: Ramesh K. Shah, Dusan P. Sekulic. Fundamentals of Heat Exchanger Design. John Wiley & Sons, Inc. p. 116, 118-119 (2003).
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 10
http://ocw.mit.edu/fairusehttp:22.033/22.33
Hx Flow Types
***After Ramesh K. Shah & Dusan P. Sekulic. Fundamentals of Heat Exchanger Design. John Wiley & Sons, Inc. (2003).
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 11
Heat Exchanger Classification by Flow Arrangement
Parallel counter-flow
m-shell passesn-tube passes
Fluid 1 m passesFluid 2 n passesSplit-flow Divided-flowCross-
counter-flowCross-
parallel-flowCompound
flow
Extended surface Shell-and-tube Plate
Counter-flow Parallel-flow Cross-flow Split-flow Divided-flow
Single-pass Multi-pass
Image by MIT OpenCourseWare.
http:22.033/22.33
Parallel Flow vs. Counterflow
See http://www.engineeringtoolbox.com/arithmetic-logarithmic-mean-temperature-d_436.html
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 12
tpi
tsi
tpo
tso
Parallel-flow
tpi
tsi
tpotso
Counter-flow
tito
ti
to
Tem
per
ature
Tem
per
ature
Image by MIT OpenCourseWare.
http://www.engineeringtoolbox.com/arithmetic-logarithmic-mean-temperature-d_436.htmlhttp:22.033/22.33
Hx Flow Configurations
After Ramesh K. Shah, Dusan P. Sekulic. Fundamentals of Heat Exchanger Design. John Wiley & Sons, Inc. (2003).
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 13
Tubular Extended surface Regenerative
Heat Exchanger Classification by Construction
Double-pipe Pipe coilsShell-and-tube Spiral tube
Plate-type
PHE Plate coilSpiral Printed circuit
Gasketed Welded Brazed
Plate-fin Tube-fin
Cross flow to tubes
Parallel flow to tubes
Ordinaryseparating
wall
Heat-pipewall
Rotary
Fixed-matrix
Rotating hoods
Image by MIT OpenCourseWare.
http:22.033/22.33
Hx Flow Configurations - Tubular
Source: Wikimedia Commons
Courtesy of Wikipedia User:H Padleckas. Used with permission. Courtesy of Harlan Bengtson. Used with permission.
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 14
http:22.033/22.33
Hx Flow Configurations Plate Plate (brazed) type Spiral type
Alfa Biz Limited. All rights reserved. This content is excluded from our CreativeCommons license. For more information, see http://ocw.mit.edu/fairuse.
Source: http://www.alfa-biz.com/Gasketed-Plate-Heat-Exchanger.asp Source: http://www.hiwtc.com/photo/products/16/02/14/21470.jpg
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 15
Jooshgostar Equipments Manufacturing Company (JEMCO). All rightsreserved. This content is excluded from our Creative Commons license.For more information, see http://ocw.mit.edu/fairuse.
http://www.alfa-biz.com/Gasketed-Plate-Heat-Exchanger.asphttp://www.hiwtc.com/photo/products/16/02/14/21470.jpghttp://ocw.mit.edu/fairusehttp://ocw.mit.edu/fairuse
Hx Heat Transfer Mechanisms
Other design parameters should largely determine this choice
After Ramesh K. Shah, Dusan P. Sekulic. Fundamentals of Heat Exchanger Design. John Wiley & Sons, Inc. (2003).
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 16
Heat Exchanger Classification by Heat Transfer Mechanism
Single-phase convectionon both sides
Single-phase convectionon one side, two-phaseconvection on other side
Combined convection andradiative heat transfer
Two-phase convection on both sides
Image by MIT OpenCourseWare.
http:22.033/22.33
Heat Exchangers - Questions
What type to use?What working fluids?What geometry? Flow considerations? Laminar or
turbulent? Where is the tradeoff between cost & performance? Materials concerns? See also: T. Kuppan. Heat exchanger design handbook.
and Som, Introduction To Heat Transfer.
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 17
http:22.033/22.33
Heat Transport
Main problem: Get process heat from the reactor to the hydrogen & biofuels plants
How? Must consider: Temperatures Losses Flow rates Flow transients
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 18
http:22.033/22.33
Heat Transport Long Distance
How to model it? Thermal resistances FEM Loop analysis
How to pump it? Forced? Gravity? Distance from Rx to H2, biofuel plant is one
of the most important parameters
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 19
http:22.033/22.33
Heat Transport - Questions
What are the constraints? (TH-Rx ) , TC-H2, TC-bioHow far does the heat have to go? Where to take the heat from? How to transport it? How to model it? What/where are losses? Should some of it be stored...
MIT Dept. of Nuclear Science and Engineering Dr. Michael P. Short, 2011 22.033/22.33 Nuclear Design Course Page 20
http:22.033/22.33