Subject: Re: Departure from Nucleate Boiling
From: -wshill-@world.std.com (Wayne S. Hill)
Date: Sun, 19 Jan 1997 16:02:06 GMT
On 18 Jan 1997 14:35:22 GMT, John M Verhage said...
>
>I am a stationary engineer in New Jersey preparing for a gold seal
>engineers license exam and I am looking to get a better understanding
>than I have found on how DNB relates to the operation or circulation in
>a boiler. I am not sure what would cause the "high heat flux" which
>would cause DNB in the tubes of a boiler. If someone could help with
>this I would greatly appreciate it.
Send me mail if the following doesn't make sense:
The heat flux needn't be elevated: this can happen with just a slight
loss of flow. If there's a marginal drop in flow rate in one tube (all
of the other tubes OK), the point at which boiling begins in that tube
advances toward the tube inlet. There's a higher pressure drop
associated with vapor flow than liquid flow, and this tube now is more
filled with vapor flow. Despite the reduced flow, the pressure drop
actually increases, further slowing the flow. Assuming the flow
stabilizes at some reduced flow (rather than going into pressure drop/
flow rate oscillations or density wave oscillations, which further
complicate the story), this tube now boils the liquid more thoroughly
than its neighbors. Depending on things like the heat flux, fluid
pressure, tube length, etc., there could be a point along the tube where
all of the liquid is in the form of droplets, rather than a liquid film
on the tube wall, and the wall dries out. This is called DNB, dryout,
and sometimes burnout (for high temperature boilers where the tubes can
actually melt if they dry out).
Note that this can occur in one tube within a boiler, and could possibly
come and go depending on the history and dynamics of the rest of the
boiler and attached equipment. The classic way of stabilizing a
multitube boiler to prevent this (and also the oscillation problems) is
to introduce a pressure drop (orifice or other restriction) in the
entrance of each tube. If this pressure drop is large enough, the
marginal increase in vapor pressure drop with reduced flow is less than
the reduction in pressure drop from the orifice, so the flow is stable.
Hope this helps.
-Wayne
_______________________________________________________________________
Dr. Wayne S. Hill wshill@world.std.com
Foster-Miller, Inc. ***Disclaimed*** 617-684-4228
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Subject: Re: Departure from Nucleate Boiling
From: klingener@aol.com
Date: 19 Jan 1997 18:23:28 GMT
In article <01bc054c$9797e9a0$45775ecf@john.ix.netcom.com>, "John M
Verhage" writes:
>I am not sure what would cause the "high heat flux" which would
>cause DNB in the tubes of a boiler. If someone could help with this I
would
>greatly appreciate it.
I'm sure that departure from nucleate boiling (DNB) appears in a state
exam because of its importance in heat transfer in nuclear reactors. DNB
is THE underlying thermal issue in the design and operation of nukes.
Nucleate boiling (NB) is called nucleate boiling because the transition
from liquid to vapor occurs at fixed sites (nucleii) on the boiler tube
wall on the cold side. NB is the intermediate mode between liquid phase
heat transfer and bulk boiling. Because of the high local turbulence that
is characteristic of NB, the heat transfer coefficients are very high, and
as a result there is great incentive to operate boilers and nukes in that
range.
That edge of the envelope can be a ragged and unstable one with serpents
beyond. The transition from NB to bulk boiling, usually marked by DNB,
brings with it a giant increase in the flow resistance for a given mass
flow rate - a giant decrease in the mass flow rate given a fixed pressure
drop and a giant decrease in the rate that heat can be removed from that
section. Not a disaster in an ordinary boiler that has flue gas or hot
process fluid on the hot side. There, you get tube wall temperatures that
rise to the local temperature of the hot fluid and maybe some flow
oscillations. In a nuke though, you have a fixed rate of heat generation
due to fissioning of the fuel. When you go past DNB to bulk boiling, you
choke off the flow to that section of the reactor, you stop removing heat
from it, and the temperatures go up essentially beyond practical limit -
local fuel cladding failure. What happens next depends.
I think that's why it's on the exam.
---------------------------------------------
Fred Klingener
Brock Engineering PC, Roxbury CT
klingener@aol.com
---------------------------------------------
Subject: Re: MET vs ME
From: ssillato@freenet.columbus.oh.us (S Sillato)
Date: 19 Jan 1997 14:51:46 -0500
Paul Segal (PC_gle@msn.com) wrote:
: I am an MET major at Southern Tech, in Marietta GA. As a fourth
: quarter senior I'm becoming increasingly curious about the working
: relationship between MET's and ME's. I'm aware that the MET was
: initially established to bridge the gap between design engineers and
: "the shop floor", but I can't help feeling that some ME's must feel
: somewhat resentful of MET's working in similar positions despite the
: relatively shallow MET curriculum (I also attended GA Tech for a
: while, so I'm quite familiar with the disparity between the two
: programs). In short, do MET's get a hard time from ME's?
As a ME graduate of Tech(1974) I can tell you what the prevailing attitude
was then. Southern Tech was a place where many Ga. Tech students wound up
who could not or WOULD not hack the math at G.T. 35 quarter hours of Calc. is
pretty daunting. If you are looking for a job in a high tech research
area where highy theoretical background is necessary, then you pretty much
have to go for the ME. In just about every other job I've been involved
with, a practical background is much more useful.
Now, concerning the original question. Do MET's get a hard time from
ME's? Only from those that are insecure, ignorant or just plain stupid.
people you shouldn't care about anyway. I've learned a lot in my career
from many types. Two that come to mind that were influential: one an MS
in physics and one a 2 year tech grad who now holds the title of Senior
Development Scientist. Like the man said, "it ain't the piece of paper
that counts, but what you do with it."
Regards,
--
Steve Sillato NYC, LV, GBW & ALCo fan
"Nothing in fine print is ever good news."
Subject: CFP: Applied Statistics Conference.
From: isexiem@leonis.nus.sg (Xie Min)
Date: 20 Jan 1997 04:27:09 GMT
********************************************************************
* *
* ANNOUNCEMENT & CALL FOR PAPERS *
* *
* Fourth International Applied Statistics in Industry Conference *
* *
********************************************************************
June 2-4, 1997, Kansas City, Missouri, USA
at the Ritz-Carlton,
Tel (816) 756-1500; Fax (816)531-1483
Keynote speech: "QUALITY: COMMITMENT PLUS TECHNICAL MASTERY"
by: J Stuart Hunter
Dr Stu Hunter will contrast the emphasis and
organization that presently exists on behalf
of Quality with what is also required technically,
and outline what is reasonably NEW in statistics
applied to the problems of Quality - with advice
for better education in this field.
Organized by the International Statistical Applications Institute,
the International Applied Statistics in Industry (IASI) conference
series is dedicated to the dissemination of information related to
the applications of statistical methods to industrial situations -
management, manufacturing, transactions, training, research, etc.
This conference is focused heavily toward the industrial statistics
practitioner, but will include presentations of interest to persons
with all levels of expertise.
TOPICS OF INTEREST
Based on our experience with past ISAI conferences, the 1997
ISAI conference will have Design of Experiments (DOE) topics followed
closely in emphasis by various estabilished as well as non-traditional
Statistical Process Control (SPC) applications. The ISAI conference
also actively seeks to expose industrial practitioners to categorical,
spatial, directional, and other statistical methods which are gaining
more recognition recently in industry.
CASE STUDIES FROM INDUSTRY ARE PARTICULARLY WELCOME.
POST-CONFERENCE TUTORIAL
J. Stuart Hunter will be presenting a post-conference tutorial
June 4-6, 1997 on industrial statistical methods. This
tutorial will include an overview of traditional Shewhartian
SPC methods, focus on methods for non-stationary processes
including the EWMA, and introduce ARIMA as well as
Multivariate SPC methods. Additional information about this
tutorial can be found at the end of this announcement.
Tutorial registration fee will be US $1,495 per person.
IMPORTANT DATES FOR CONFERENCE REGISTRATION
Before April 15, 1997 : US $ 450.00
Before May 15, 1997 : US $ 475.00
After May 15, 1997 : US $ 495.00
All attendees of the conference must register.
|NOTE: 1. AUTHORS' CONCESSION - An author's conference registration
|fee can be fully credited against the post-conference tutorial
|registration fee. Please register early for this US $1,495 package
|of conference-with-tutorial.
|
| 2. EDUCATION CONCESSION - All high school, college, university,
|and graduate school students, and high school teachers may attend the
|conference for a registration fee of $20. They will not receive the
|proceedings (which can be purchased separately at the conference site)
|and other conference materials. Please state clearly your status when
|you register at this rate.
PAYMENT OF FEES
All payments, in checks and (for those from outside the
U.S.) bankdrafts made payable to "International Statistical
Applications Institute"), are to be forwarded to the address
below. Please state clearly your name, address, phone number
and (if available) fax and e-mail address.
| ISAI
| PO Box 782948
| Wichita, KS 67278-2948
| USA
HOTEL REGISTRATION
Direct with Ritz-Carlton, @ $129 per night single or double.
Tel (816) 756-1500 Fax (816) 531-1483
(Please reserve early as there is a limited number of rooms
available at this preferential rate.)
____________________________________________________________________________
INFORMATION FOR AUTHORS
Those who intend to present a paper at the conference may
contact the Conference Program Chairman, Professor TN Goh,
or the Conference Organization Chairman, Brad Brown (whose
e mail and fax numbers are given at the end of this
announcement - use whichever is more convenient) as soon as
possible, with the following information:
* Title of proposed paper,
Abstract (max. 300 words)
paper classification (see below)
* Name, affiliation, address,
telephone, fax, and e-mail address
* Brief author's biography (max. 300 words)
Authors are requested to classify a paper as follows:
[G]: For the general audience; this includes review papers
[S]: For people with at least a minor in college statistics;
this includes original research papers
[C]: Case studies; emphasis is on application rather than
the underlying theory
Such classification will help conference programming as well
as guide the audience to the right sessions.
*****
Authors please note: Acceptance decisions for abstracts
will be made by the Conference Program Chairman as abstracts
are received. Thus, early submissions have higher probabilities
of acceptance. A $50 presentation deposit is due within one week
of acceptance of abstract. This deposit will be applied to the
conference registration fee. (Authors are encouraged to register
on acceptance of their abstracts so that they do not have to make
payments more than once.)
*****
Format for final full paper:
Camera-ready; maximum 12 pages. (Due to constraints
in the production of conference proceedings, any
material beyond the first 12 pages submitted will
be dropped).
_________________________________________________________________________
IMPORTANT DEADLINES FOR AUTHORS:
ABSTRACTS ARE TO BE SENT NOW to either Brad Brown at the conference
organization office, or T N Goh at the conference program office.
Authors are informed of their abstracts' acceptance as they are
reviewed.
February 15, 1997: All authors to receive confirmation of
their papers on the conference program.
April 1, 1997: Final version of full papers to reach
conference organization office in the U.S.
Papers not received by this date will not be
included in the conference proceedings.
____________________________________________________________________________
| CONFERENCE PROGRAM CHAIRMAN:
|
| Prof T N Goh
| Industrial & Systems Engineering Dept
| National University of Singapore
| Kent Ridge
| Singapore 119260
|
| Fax: (65) 777 1434
| Email: isegohtn@nus.sg
|
|
| CONFERENCE ORGANIZATION CHAIRMAN:
|
| Brad Brown
| P O Box 782948
| Wichita, KS 67278-2948
| USA
|
| Phone: (913) 841 0473
| FAX: (913) 841 2133
| Email: bjbrown@eagle.cc.ukans.edu
The latest version of this announcement can be found on:
http://www.eng.nus.sg/ise/
__________________________________________________________________________
Titles of some accepted presentations:
* Six methods to compute Cpk for non-normal data: a review
and comparison
* A multivariate boxplot-T^2 control chart
* Test limits using correlated measurements
* The role of pure error on normal probability plots
* Using exponentially weighted moving average to monitor
and forecast pollution
* Applying screening, modeling and robust DOE techniques
for process optimization: a practical case study
* Mechanical drive cable DOE case studey using scaled and
measurement data
* Teaching statistics - Industrial realities not between
the textbook covers
...and many others.
