Temperature rise as K?
Temperature rise as K?
(OP)
Dear users,
In several places of the heating sections of Euro (EN) standards, there are several tables showing 'temperature rise as K'. For example: "During normal operation, the temperature rise of the applience's walls shall not exceed 140 K". What does 'temperature rise as 140 K' mean?
Thanks!
In several places of the heating sections of Euro (EN) standards, there are several tables showing 'temperature rise as K'. For example: "During normal operation, the temperature rise of the applience's walls shall not exceed 140 K". What does 'temperature rise as 140 K' mean?
Thanks!






RE: Temperature rise as K?
K-stands for Kelvin.
Degrees Kelvin is same as Degrees Centigrade (hope you are familiar with).
This is intended as a mark of paying respect to the great scientist Dr. Kelvin.
RE: Temperature rise as K?
Thanks but 140 K means -133 (minus!!) C !
What I dont understand is: I need to find out the change in the surface temp of the appliance (starting the test at 20C room temp) and a value as -133 C doesnt make a sense...
I need to know how to use those values (140 K is applied as how)?
Thanks again..
RE: Temperature rise as K?
RE: Temperature rise as K?
Dear GTstartup,
Thanks, but,
So, in simple words (so a non-engineer naive like myself (just the designer) can understand
If the limit rise is 140 K on that wall, and if we are starting from room temp of lets say 20 C, what is the max F or C allowed on that part?
Thanks..
RE: Temperature rise as K?
temp. rise = 140 degree Kelvin
Final temp limit of appliance = 20+140 = 160 degree C
thanks
RE: Temperature rise as K?
T1 = 20 degrees C = 20 + 273 = 293 degrees K
delta K = 140 degrees K
T2 = 293 + 140 = 433 degrees K = 433 - 273 = 160 degrees C
Crystal!
RE: Temperature rise as K?
20 C = 20 + 273.15 = 293.15K
140K rise allowed = 293.15 + 140K = 433.15K
433.15K= 160C
So in terms of rise or differential 140 K = 140 C
(more or less the same as Burnt's but I had typed it already
;)
RE: Temperature rise as K?
I have news for technical geeks, you don't really impress people by confusing them with your technical jargons.
The rise should be mentioned in the same units as the normal temperature is being specified or implied. If you want to honor someone, there are other means. If anything, we need fewer temperature indicating symbols and baselines, not more.
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
RE: Temperature rise as K?
I think the answer is not to demand of the world that all temperature rises to be specified in your own personal preferred system of units, but to apply a small degree of critical thinking before you plug and chug.
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RE: Temperature rise as K?
When computing ideal gas law-related formulas, the Kelvin temperature scale is used. You have to convert all temperatures to degrees K and then proceed in the calculation.
epete,
It's not a matter of demanding things out of preferrence, it's required by the formula you are using.
If others believe the answer offered is wrong, just say it is so, and offer a better answer! No problem here.
RE: Temperature rise as K?
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RE: Temperature rise as K?
K has nothing to do with the absolute zero. It is a measure just like feet or pounds. It is without a fixed reference while C and F both have fixed references.
The reason K is used is to avoid expressing differences in a unit that has a fixed reference. Difference and absolute value only make sense if the reference is zero. If it isn't, like the example mentioned by the OP, then confusion pops up.
It is unfortunate that the misconception that K is referenced to absolute zero has gained such popularity. It was never intended to be like that.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Temperature rise as K?
Try forecasting weather in K. If that is not acceptable than why use it where it is really not necessary? Does using K in temp rise clarifies anything more than if it were in C or F?
It anything, it raises a few eyebrows.
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
Pete, I wasn't quite sure what you were trying say. I can read your post in two different ways.
RE: Temperature rise as K?
I hold the opposite view regarding Celcius: the Kelvin unit is one of the seven base units of the SI system, and should be the preferred unit of temperature used in technical descriptions. I accept the use of Celcius where the public are involved, but the public appear relate everything to the weight of a jumbo jet these days (at least on Discovery Channel) so they're probably not the best place to make the decision.
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If we learn from our mistakes I'm getting a great education!
RE: Temperature rise as K?
It is true that the lowest possible temperature is 0 K above absolute zero. But, unfortunately, the three last words are often dropped. Hence the misconception that absolute zero is 0 K.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Temperature rise as K?
Dear Users!
Thanks a lot for all the attention! Anyway, I am attaching 2 jpegs; first one is from CSA. Then I will post onother message with the jpeg from EN60335-1.
It is very easy to find the answer in CSA's doc: Item 1 says: "At any point on or within a supply terminal box, the max temp is 60C." Thats it!
What is the answer for the EN 60335-1??? "xxx K?" What is the max temp allowed as C?
Thanks!
RE: Temperature rise as K?
... and here is the jpeg from EN60335-1 !
RE: Temperature rise as K?
... and here is the second table from EN60335-1, attached...
RE: Temperature rise as K?
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If we learn from our mistakes I'm getting a great education!
RE: Temperature rise as K?
If the ambient temperature is indicated in C (or F) there is not sense in indicating the rise in K. There was no confusion over using C or F for decades, why mess with it.
Keep the K for scientific journals and conversion tables. Normal applications do not need it.
Perhaps there would be no issues, if we say the floor to floor to height is 15 feet and the building should be 50 meters tall, the tile sizes 12"X 30 cm....
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
That is just a datapoint to counter the IEC reference. As I said above, it seems to me somewhat pointless to argue about which unit someone happens to think is better... with a very small amount of thinking we should be able to cope with whatever units the temperature rise is specified in.
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RE: Temperature rise as K?
I would give that reference much greater credibility if it was published by a nation which doesn't stubbornly cling to a modified Imperial measurement system...
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If we learn from our mistakes I'm getting a great education!
RE: Temperature rise as K?
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RE: Temperature rise as K?
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
Thanks a lot for all the valuable effort and data.
Best regards...
RE: Temperature rise as K?
I am pretty sure that 0 K is absolute zero. That is how we define what absolute zero is.
RE: Temperature rise as K?
I like ElectricPete's answer. Since we can't all agree on common units then we need to be able to deal with what is given.
RE: Temperature rise as K?
The definition says nothing about a reference temperature. It is exactly the same thing as the definition of the metre - it is defined as a fraction of the earth's quadrant. But that does not mean that is neccessarily has to start at the North Pole (or Equator).
Re: "If that's not true then there are a lot of people doing it wrong" Yes. But most people think it is right - remember the saying "Ten thousand flies cant be wrong - eat sh-t" Same thing here.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Temperature rise as K?
Why would they pick a rather inconvenient number like 273.16 if it was for some purpose other than to place the zero point of the Kelvin scale at absolute zero?
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If we learn from our mistakes I'm getting a great education!
RE: Temperature rise as K?
It is a unit. Not part of a scale.
I do not say that it isn't based on the absolute zero - it just doesn't start there. It starts nowhere. That is why it has been chosen for temperature deltas. C and F are for temperatures as such. But not for differences. It is about scientific prnciples.
Why is this so dificult to understand?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Temperature rise as K?
RE: Temperature rise as K?
I do believe you are mistaken. In my thermodynamics and aerospace classes way back when, it was defined as 0degK=absolute zero. See:
http://en.wikipedia.org/wiki/Kelvin
I don't think that has changed since the mid-seventies.
EEJaime
RE: Temperature rise as K?
I think we understand perfectly well the difference between a unit and a scale. Kelvin can be used in both ways as you say: as a unit/increment (the first sentence below) and as a temperature scale (the third sentence below):
http://en.wikipedia.org/wiki/Kelvin
But it should be noted that Celcius can be used in the same way as either a scale (first sentence below) or an increment (second sentence below)
http://en.wikipedia.org/wiki/Celcius
If Wikipedia is not a solid reference, please consider this reference: "Applied Dimensional Analysis and Modeling" by Thomas Szirtes and P. Rózsa
It is a book that delves into the restructuring of problems into dimensionless variables, guessing the solution to an analytic problem by unit analysis, etc. Chapter 3 is a detailed discussion of unit systems in use. The authors presumably know just a little bit about units. (*)
On Page 287 they analyze a thermal growth problem using a difference in temperatures. And what unit is used for the delta-T? Degrees C. See for yourself.
http://
(* they are Canadian – does that make a difference?)
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RE: Temperature rise as K?
That is where the confusion started. It is important to understand the difference between a measure with a reference and a delta measurement. The former has a zero point, be it center of Paris or the triple point of water. The latter does not have a zero point. It just says how long or how long time something takes - or how big a temperature rise is.
That is all there is to it. I do not deny at all that K is sometimes used to express temperature. But then, it should be used with words saying what reference is used. Common usage is absolute zero. But absolute zero is NOT defined as 0 K. The definition is that all molecular movement has stopped. Thermal energy is zero.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Temperature rise as K?
Unless it changed in last 30 years, we were taught the absolute zero happens at 0 K.
Oh and that brilliant definition of meter being some fraction of the earth's quadrant is another example of going overboard with "technical" definitions. For some reason the earth contracts or expands, which it certainly can, all the distance measurement in meters will be wrong!! Don't they have a master meter stick in Paris? or is that the mass of a kg?
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
I think everyone had the point about delta temperatures being differences in temperature before anyone bothered to point that obvious fact out.
I am not getting your point about zero K not being absolute zero... I will have to go back to my graduate studies prof and correct him on this.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Temperature rise as K?
Absolute zero defines 0K, 0K does not define absolute zero.
On the other hand this all way too much ado about nothing. Anybody who can't recognize that a 140K rise is exactly the same thing as a 140C rise needs to go back and brush up on basic units and anybody that would write a standard that has ambient in C and rise in K needs to get their head back into somewhere that the sun might shine.
RE: Temperature rise as K?
RE: Temperature rise as K?
And then there's
Which I cannot particularly argue with. But what remains unresolved is the mantra that there is only one "right" unit and anyone who doesn't agree doesn't "get it:"
The bolded portions in the quote directly above are incorrect. I have established above that K, degrees C, and degrees F can ALL be used as EITHER an element of a temperature scale OR as a unit for differential temperatures. Check out the references I have provided 10 Aug 09 16:37 along with IEEE 1-2000 which references temperature rises in degrees C along with wiki entry for Fahrenheit which states under the heading "Temperatures and intervals" the following:
http://en.wikipedia.org/wiki/Fahrenheit
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RE: Temperature rise as K?
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
If you look at the following link (by those Canadian authors of dimensional analysis book) you will see almost identical discussion to what you have quoted... but KEEP READING and it is clear (allowing for typographical error 271.16K vs 273.16K) that they are using K as a temperature scale since they say that temperature of the triple point of water (which is 0C) is "defined as 271.16K."
ht
I think it's pretty clear they are using K as a temperature scale.
I guess we could take your word for it. Or we could look some more for ourselves:
http://
http://
http://b
http://
http://b
There seem to be a whole lot of references that have it wrong. I couldn't find a single reference that said anyting resembling the fact that K was exclusively to be used as a unit and NOT as a temprature scale (which happens to be absolute). But in the bolded section of the very last quote above, there is something resembling your statement that K can be used for comparsion while C and F cannot, but the context is energy comparison, not temperature comparison. Is it possible you have mixed up the concept of energy comparsion with temperature comparison to come up with your conclusion that K can be used for temperature comparsion while C and F cannot?
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RE: Temperature rise as K?
sunchallenger:
Are you still with us? Is your question answered satisfactorily?
Regards
Wolf
WWW.HYDROPOWER-CONSULT.COM
RE: Temperature rise as K?
"much ado..."
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Temperature rise as K?
I am just a designer for my own project and all those heavy techical arguments do not help me too much. I was just looking for a simple answer, what is the max temp allowed as C?
Therefore, I am basing my decision on the 'direct-to-my-question' answers of dear bashar2008, burnt2x, and GEstartup.
Bottomline:
I will kindly ask my friend who is with me in this project (who actually happens to be one of you guys here) to use the best&fully certified equipment for all areas, and I will also make 'extreme design related changes in cooling', to keep the subject areas in 'basic room temperature'!
This way I will cover myself.
Thanks for your attention!
RE: Temperature rise as K?
I gave you a star for saying what matters most:
Trying to get fancy with K is no betterment over C, which most people understand. The specifier could have done a great service had he/she used C instead of K.
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
If Kelvin is for some reason an unfamiliar concept to you – by all means follow the links. But don't bother to read this thread. There is repeated misinformation that was never acknowledged even after proven wrong.
Time to move on to more productive things...
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RE: Temperature rise as K?
I never looked at the kelvin scale from the point of view Skogsgurra has provided. Thanks for the insight!
RE: Temperature rise as K?
sunchallenger:
With trying the Google webside first and typing in "Kelvin" and "Wikipedia" you would have saved us a lot of effort and time. Especially as you still seem to be puzzled over this subject.
Regards
Wolf
WWW.HYDROPOWER-CONSULT.COM
RE: Temperature rise as K?
kelvin (metric practice) Unit of thermodynamic temperature,
it is the fraction 1/273.16 of the thermodynamic temperature
of the triple point of water (adopted by 13th General Conference on Weights and Measures). (QUL) 268-1982s
degree Celsius (metric practice) It is equal to the kelvin and is used in place of the kelvin for expressing Celsius temperature(symbol t) defined by the equation t = T – T0 where T is the thermodynamic temperature and T0 = 273.15 K by definition. (QUL) 268-1982s
RE: Temperature rise as K?
RE: Temperature rise as K?
Centigrade was always there and was nicely divided in 100 between water's freezing and boiling temperatures. It was changed to Celsius in 1948. K's scale of 1/273.15 was selected to fit C scale.
K was adopted in 1967, and to say that C is used in place of K in 1982 is quite interesting.
From US Metric Association:
The degree Celsius (°C) scale was devised by dividing the range of temperature between the freezing and boiling temperatures of pure water at standard atmospheric conditions (sea level pressure) into 100 equal parts. Temperatures on this scale were at one time known as degrees centigrade, however it is no longer correct to use that terminology. [The official name was changed from "centigrade degree" to "Celsius degree" by the 9th General Conference on Weights and Measures (CGPM) in 1948.]
The kelvin (K) temperature scale is an extension of the degree Celsius scale down to absolute zero, a hypothetical temperature characterized by a complete absence of heat energy. Temperatures on this scale are called kelvins, NOT degrees kelvin, kelvin is not capitalized, and the symbol (capital K) stands alone with no degree symbol. [The official name was changed to "kelvin" and symbol "K" by the 13th General Conference on Weights and Measures (CGPM) in 1967.]
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
It even has not so flattering quotes about Fahrenheit scale, not that it really matters to US.
http://lamar.colostate.edu/~hillger/temps.htm
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
Great link above by Rafiq confirms that according the US metric association, K can be used as a scale.
I also think it was good for stevenal to post some excerpts from IEEE 100 and I would like to spend some time (the bulk of this post) talking abouut that. I suspect the reason the IEEE100 definitions were posted is because they don't explicitly state that C can be used as unit or scale and K can be used as unit or scale. But considering there is only one or two sentences per definition, that omission is certainly not a contradiction to my position. And closer inspection will in fact reveal that IEEE100 supports my position (that either K or C can be used as a unit or a scale) based on examination of the definitions themselves and also by examination of useage of those terms in other parts of the document.
First look at the IEEE100 definition for C
Now look at the phrase "It [degree Celsius] is equal to the Kelvin" and ask yourself whether "it" [degree Celsius] is being used as an element of a scale (to indicate temperature) or a unit (such as to indicate differential). It is clearly not being used as a scale because a temperature expressed in Celsius is not the same as a temperature expressed in Kelvin. So it is being used as a unit in the same way we can use C as a unit to express a differential temperature. It is perfect and complete agreement with my position.
Now look at the IEEE100 definition of C and work backward to understand the terminology used in the standard. How is it that we know that the "T" in the above equation "t=T-TO" is an absolute temperature (we already know from our prior knowledge of these relationships, but what word in this particular definition tells us that T is absolute) ? It must be by the use of the phrase "thermodynamic temperature". Thus in the usage of IEEE100, the phrase "thermodynamic temperature" denotes absolute temperature. And where else is that phrase used within IEEE100? In the definition of Kelvin ("unit of thermodynamic temperature" ). But that distinction between absolute and relative temperature would not be important if K were used soley as a unit, and so there is no reason to use the phrase "unit of thermodynamic temperature" if K were used soley as a unit. It is thus clear the authors anticipated K would be used as a scale (in addition to a unit) and they are defining for us that the K scale is a thermodynamic temperature.
Now this last point I will certainly agree is more convoluted than the first, but such is the nature of trying to draw conclusions from a document that does not explicitly address the question. More importantly we don't have to stop with the definitions, we can look at how the terms C and K are used elsewhere in the IEEE100 standard and we find as expected that it is 100% consistent with my position.
There are many IEEE100 usages of Kelvin as a temperature scale. I will quote just one but you can look for yourself to find many others:
Note also the works "Kelvin temperature scale"... that's what I have been saying... Kelvin can be used as a unit or a scale.
And now more directly related to the question at hand:
Above we are using C as a unit for a rise (not as a temperature scale). Again, that's exactly what I've been saying since my very first post.
I notice wikipedia was singled out for comment, but wikipedia was certainly not the only reference that was quoted. There was IEEE-1-2000, there was the dimensional analysis book by those Canadian authors, and there were many other textbook links provided. And now add to that the link by Rafiq.
I think my point is very well supported, but it occurs to me that for someone reading casually this appears to be a question of "dualing standards": The IEC gives rise in K and the IEEE gives rise in C..... so which one do we believe? Well.... that is certainly a contradiction to the position of others who stated K is the only unit for rise. But it is 100% consistent with my position that either C or K (or F) can be used as either a unit (such as for rise) or a scale (for temperature measurement).
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RE: Temperature rise as K?
... this thread is why engineers get a bad rap sometimes.
Do we really need this much information to tell us what temperature is? Did we not all learn this is grade 8 science class? My girlfriend is a physicist and if she read this she would make fun of me.
Its a much simplier than any standard will ever make it out to be. Keep in mind standard agencies often compete against each other when they try to redefine the wheel in order to seem more relavent.
RE: Temperature rise as K?
Then came comments from another forum member suggesting there was only one way to approach the problem (K is the only unit for temperature rise) and that K is not a temperature scale, but only a unit. Those comments have still not been retracted.
That is the context in which my most recent posts appears. Perhaps I have a naive expectation that this may lead others to acknowledge their misinformation. If you thought the purpose of my comments was to explain in simple terms the concepts of K and C scales, then you are mistaken. You will note I have previously directed the original post AWAY from this thread and TO Wikipedia for that very purpose.
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RE: Temperature rise as K?
Who is the definitive source for the SI system? The CGPM and CIPM
http://physics.nist.gov/cuu/Units/acronyms.html
Here is a paper on the ITS-90 (International Temperature Scale of 1990) which was proposed by CIPM and approved by CGPM. Note this paper is published by the CIPM:
http
Take a look at the last sentence on the first page:
That completely debunks the claim that Celsius is not a "unit" (i.e. not suitable for temperature differences).
Now take a look at the first paragraph on the 2nd page:
So International Kelvin temperatures are reported in units of kelvin, and conversion between Kelvin temperature and Celsius temperature is accomplished by equation 2. Review of the remainder of the document and other references makes it clear that ITS-90 is simply a calibration standard to allow calibration of devices reading out in degrees K or degrees C (the triple point of water is only one of many calibration points).
This completely debunks the claim that K is not a temperature scale.
Personally I would really think that at this point the person who created all the confusion in this thread would want to acknowledge his errors. But maybe that's just me.
My case has been proven beyond doubt. I will not make any more posts unless responding to further posts by others in this thread.
Btw Mark I reread your post and realized I misinterpretted it. Sorry for that. I guess you were only suggesting a humorous introspective look at ourselves as engineers on the forum. Not a bad idea. Sorry to all if I have created any negative tone on the forum. I could offer the excuse "he started it". But that doesn't work for my 11 year-old, so I guess it doesn't work here!
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RE: Temperature rise as K?
LPS for the hard work!
Rafiq Bulsara
http://www.srengineersct.com
RE: Temperature rise as K?
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RE: Temperature rise as K?