Temperature rise as K? 11

[Jakelian]

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!

 

[roydm]

I think we should all change to °Rankine

 

[electricpete]

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.

LOL. But as you point out (and I agree) it is not an irrecoverable error:

anyone 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 then there's

way too much ado about nothing.

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:"

You still do not get it!

It (K) 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 (K) 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?

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

As with the Celsius scale, the same symbol, "°", is used to denote both a point on the temperature scale, with a letter (C, F) indicating which scale is being used (e.g. "Gallium melts at 85.5763 °F"), and to denote a difference between temperatures or an uncertainty of temperature (e.g. "The output of the heat exchanger is hotter by 72 °F" and "Our standard uncertainty is ±5.4 °F").

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[rbulsara]

I like the Rankin idea!

Rafiq Bulsara

http://www.srengineersct.com

 

[electricpete]

The strict definition of the degree kelvin is: "the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The definition was taken by the CGPM in 1967.

The definition says nothing about a reference temperature.

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."

http://books.google.com/books?id=G_...+was+adopted+at+the+16th#v=onepage&q=&f=false

The definition of kelvin for thermodynamic temperature was adopted at the 16th
CGMP (in 1967) as follows: The kelvin is the fraction 1/273.16 of the thermodynamic
temperature of the triple point of water. The triple point of water is, by definition,
that single point in the temperature-versus-pressure coordinate plane at which ice,
water, and steam can coexist in equilibrium (see Fig. 3-5). This point is called a triple
point because at this location (and only at this location) the three curves separating
the three phases (ice, liquid, and vapor) intersect. The curves are the fusion curve A,
the vaporization curve B, and the sublimation curve C (Fig. 3-5). The temperature
at the intersect is defined as 271.16 K (exactly), and the pressure at this point is
measured to be 610.483 pascal.

I think it's pretty clear they are using K as a temperature scale.

The OP asked what the temperature difference expressed in K. He got a valid answer and then protested that 140 K = -133 C.

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 guess we could take your word for it. Or we could look some more for ourselves:

http://books.google.com/books?id=mn...#v=onepage&q=kelvin temperature scale&f=false

absolute zero is the basis for the kelvin temperature scale

http://books.google.com/books?id=Ww...#v=onepage&q=kelvin temperature scale&f=false

The commonly used temperature scale in science is the Kelvin scale; its zero point corresponds to the lowest temperature possible (absolute zero), about –273C

http://books.google.com/books?id=kw...#v=onepage&q=kelvin temperature scale&f=false

In the S.I. System, Kelvin is the standard unit for temperature..... The scale is based on the average kinetic energy per moleducle of a perfect gas. Zero is equal to –273.16C.

http://books.google.com/books?id=Fs...#v=onepage&q=kelvin temperature scale&f=false

The Kelvin temperature scale uses the theoretical absolute zero as its zero point

http://books.google.com/books?id=oS...#v=onepage&q=kelvin temperature scale&f=false

The most common absolute temperature scale used by scientists is the Kelvin temperautre scale... (next page). The Kelving temperature scale has an absolute zero. True comparsions can be made sing the Kelvin scale. A substance at a temeprature of 400 Kelvins contains particles with twice as much kinetic energy as a substance at 200 Kelvins

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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[wolf39]

sunchallenger:

Are you still with us? Is your question answered satisfactorily?

Regards

Wolf

http://WWW.HYDROPOWER-CONSULT.COM

 

[Skogsgurra]

Pete,

"much ado..."

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Jakelian]

Yes Wolf39, I am still around and reading the discussion...

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!

 

[rbulsara]

sunchallanger:

I gave you a star for saying what matters most:

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?

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

 

[electricpete]

I don’t think there is any doubt the original question was answered three times on the first day it was posted.

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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[marks1080]

There is nothing wrong with a side tracked discussion! Thats part of why this forum is here.

I never looked at the kelvin scale from the point of view Skogsgurra has provided. Thanks for the insight!

 

[wolf39]

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

http://WWW.HYDROPOWER-CONSULT.COM

 

[stevenal]

I suggest that IEEE 100 is a better reference for our purpose than Wikipedia:

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

 

[burnt2x]

Like I said, it's not a problem at all!

 

[rbulsara]

IEEE 100 appears to be a retrofit definition.

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

 

[rbulsara]

Here is the link:
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

 

[electricpete]

To summarize my position (as prelude to a long discussion): K, degrees C, and degrees F can ALL be used as EITHER an element of a temperature scale OR as a unit of differential temperature. This stands in contrast to another forum member’s position that C and F are only scales (not units) and therefore cannot be used for differential temperatures .... and that K is only a unit and not a temperature scale.

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

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

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:

“chromaticity….(4) (electric power systems in commercial buildings) The measure of the warmth or coolness of a light source, which is expressed in the Kelvin (K) temperature scale.”

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:

“insulation class …. NEMA Class B. An insulation system (130 C temperature limit including a 40_C ambient or 90C rise)”

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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[marks1080]

I say this jokingly (and also as an engineer)...

... 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.

 

[electricpete]

Hi Mark. In my very first post, I stated anyone can figure out the temperature rise with a little bit of critical thinking regardless of the units.

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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[electricpete]

This will be my last post unless someone else chooses to continue the discussion.

Who is the definitive source for the SI system? The CGPM and CIPM

http://physics.nist.gov/cuu/Units/acronyms.html

CGPM General Conference on Weights and Measures (CGPM, Conférence Générale des Poids et Mesures).
The CGPM is the primary intergovernmental treaty organization responsible for the SI, representing nearly 50 countries. It has the responsibility of ensuring that the SI is widely disseminated and modifying it as necessary so that it reflects the latest advances in science and technology.

CIPM International Committee for Weights and Measures (CIPM, Comité International des Poids et Mesures).
The CIPM comes under the authority of the CGPM. It suggests modifications to the SI to the CGPM for formal adoption. The CIPM may also on its own authority pass clarifying resolutions and recommendations regarding the SI.

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://www.bipm.org/utils/common/pdf/its-90/ITS-90.pdf

Take a look at the last sentence on the first page:

A difference of temperautre may be expressed in kelvins or degrees Celsius

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:

The International Temperautre Scale of 1990 (ITS-90) defines both International Kelvin Temperatures, symbol T90, and International Celsius Temperatures, symbol t90. The relationship between T90 and t90 is the same as that between T and t, i.e.

t90/C = T90/K – 273.15 (2)

The unit of the physical quantity T90 is the kelvin, symbol K, and the unit of the physical quanitty t90 is the degreee Celsius, symbol degC, as is the case for the thermodynamic temperature T and the Celsius temperature t.

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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[rbulsara]

electricpete:

LPS for the hard work!

Rafiq Bulsara

http://www.srengineersct.com