Talk:Countercurrent exchange

Error in CoCurrent Exchange section
I believe that this article contains an error. It says, speaking of cocurrent exchange, that

"It can't achieve more than 50%, because at that point, equilibrium is reached, and the gradient declines to zero."

The article never mentions any assumption that the two flows are equal, so for instance you could have 1 lb/hr of water at 100°F heating 100 lbs/hr of water at 50°F and both streams could end up near 50.5°F. I'm going to change the article.


 * I corrected the article extensively. I think that concurrent behavior is now clear. Perhaps I should mention that the example (entry levels of 60° and 20° ending up at around 40° works the same with Fahrenheit and Celsius.פשוט pashute ♫ (talk) 09:52, 10 July 2011 (UTC)

Split a diagram?
Would it be good idea (and does anyone know how) to split the figure here and have one figure per exchange type? —Preceding unsigned comment added by Jhbdel (talk • contribs) 22:42, 16 December 2008 (UTC)
 * Would be easy to do in a graphics-editor. However, would need some tweaking or careful control of whitespace/margins (i.e., not crop them both). One of the nice features of this image is the alignment of the two processes. DMacks (talk) 22:47, 16 December 2008 (UTC)


 * Good point. What I'm actually trying to create is a visual expression of the fact that the two processes are discussed in separate paragraphs.  Maybe this is obvious enough given the formatting constraints.--Jhbdel (talk) 22:55, 17 December 2008 (UTC)


 * I hope my extensive edit of the article clears that point.פשוט pashute ♫ (talk) 09:52, 10 July 2011 (UTC)

Merge with Heat exchanger
Although this page discusses an important phenomenon, I think that the content belongs on the 'heat exchange' page, where the accompanying theory would give the material a firmer base. The biological examples are nice, but lack citations and diagrams. There are assumptions in the discussion that need to be made much clearer, eg assumption that both fluids have same capacity rate. The topic is also of key importants in thermal energy systems engineering and mechanical engineering in general, not just chemical engineering. Jdpipe (talk) 13:22, 12 November 2009 (UTC)


 * No. The countercurrent exchange is not restricted to heat. פשוט pashute ♫ (talk) 09:52, 10 July 2011 (UTC)

Furnace (kiln) How?!
After thinking it over, I found that a better explanation is needed for understanding how the furnace (Anagama Kiln) and other high concentration systems work.

The theory explained in the article (and which I rephrased shows that the maximum output of a counter-current exchange system can only be slightly LOWER than the original input heat. So how does the kiln reach high temperatures. The answer is probably exactly that. The fire heat is at high temperature but low energy (not enough to heat the full amount of material to that temperature in a short while, otherwise it would be an explosion and not a fire). So using the CCHE (counter current heat exchange), slowly the heat is built up, always starting at the highest temperature of the fire itself, while the internal recycling with the counter-exchange mechanism, leaves the heat inside, to continuously build up. This calls for a separate drawing!

3000° input ->
 * System boundary | hottest in kiln (receiving external heat) 250   <--  less hot 230  <--  coldest (heated from last batch) 220
 * System boundary | recycled back 250 --> a bit hotter (original heat lost to opposing stream 231)   --> almost coldest 221

Later: 3000° input ->
 * System boundary | hottest in kiln (receiving external heat) 1250   <--  less hot 1230  <--  coldest (heated from last batch) 1220
 * System boundary | recycled back 1250 --> a bit hotter (original heat lost to opposing stream 1231)   --> almost coldest 1221

This will continue till 3000.

Could anyone comment on this, and tell me if my understanding is correct? פשוט pashute ♫ (talk) 09:52, 10 July 2011 (UTC)

Missing image of closed circuit bio-system counter current exchange
Can someone please supply an image of the closed circuit exchange in bio-systems? (I may do it myself if I get time)
 * Heart
 * _|_hot_101°F___^
 * _v_____________|100°F
 * _|warm_51°F___^
 * _v____________|_50°F
 * _|cool__6°F___^
 * _v____________|___5°F
 * _|cold__5°F___^
 * _v____________|___5°F Nothing lost to ground
 * ========================= Ground 5°F ===========
 * _|cold__5°F___^
 * _v____________|___5°F Nothing lost to ground
 * ========================= Ground 5°F ===========

If I have the time I'll do it myself. (SVG with Inkscape or an image with google docs draw).פשוט pashute ♫ (talk) 09:52, 10 July 2011 (UTC)


 * Done פשוט pashute ♫ (talk) 09:08, 25 July 2011 (UTC)

Seabird high concentration - How?
After I finished rephrasing the entry, I found that I don't truly understand the seabird salt extracting gland.

How is high concentration of brine done, using only a counter-exchange. According to the explanations in the theory section, you can only interchange two flows. How do you cause one flow to reach a higher concentration than the original one. Or am I missing something? פשוט pashute ♫ (talk) 09:52, 10 July 2011 (UTC)
 * OK! Reading the source given (Avian osmoregulation explains it:
 * I'll soon fix the entry.
 * a. Salt enters the blood plasma, so it is initially at a high concentration (but less than the sea water)
 * b. Osmosis causes the extra-cellular fluid volume to rise while lowering the salt concentration.
 * c. A section of the salt gland further raises the blood plasma concentration of salt in a small area of the salt gland, by Active transport (moving the salt against its concentration gradient, using energy from ATP breakdown).
 * d. In order to preserve the high concentration in the gland, blood plasma entering the gland and exiting it, is passed through a counter current exchange circuit, so that the high concentration of salt in plasma leaving the gland is returned to it in the incoming plasma, thus preserving the high concentration in the gland without losing it to the blood system, while allowing the concentration to build-up in the gland by active transport. פשוט pashute ♫ (talk) 08:41, 14 July 2011 (UTC)

Top/Bottom Confusion
The section "Countercurrent flow - almost full transfer" refers to a diagram with a "top" and a "bottom" pipe, but the diagram shows a spiral having no clear top or bottom element. Somebody please fix the text or provide a better diagram. 69.130.242.120 (talk) 04:41, 22 November 2013 (UTC)


 * I corrected the text and example. Added diagram from above - the diagram is now shown a second time in the article, for clarity.פשוט pashute ♫ (talk) 09:03, 5 December 2013 (UTC)

Multiplication
This page has come on a lot since I last visited, but I am concerned about the accuracy of this expression,
 * A countercurrent multiplier is a system where fluid flows in a loop so that the entrance and exit are at similar low concentration of a dissolved substance but at the tip of the loop there is a very high concentration of that substance.

Urea and creatinine levels for example are much higher at the end of the loop than before it, that seems to be the whole purpose of the renal loop, concentrating waste products without losing valuable electrolytes and water. A better description might begin,
 * A countercurrent multiplier is a system where fluid flows in a loop in which active transport generates a high solute concentration gradient near its tip.

The curious property of the loop is of course that the gradient is generated by the efflux limb not the influx. Happy to help with this, but I think this section particularly is not very clear and could be improved to make it easier to grasp the central mechanism.Cpsoper (talk) 13:25, 20 April 2014 (UTC)


 * It seems to me that the current explanation is a leftover in error by myself, when I thought that various countercurrent systems had the same properties, and was not aware of the difference between countercurrent loops (which are what is described in the explanation you quoted) vs. countercurrent multiplication which is exactly what you described in your corrected annotation. (counter-current loops are a special case of counter-current exchange, not so counter-current multiplication). I'll update the information correctly, now. פשוט pashute ♫ (talk) 11:10, 9 May 2014 (UTC)


 * Correction. After re-reading my own explanation written some years ago, it seems that counter current multiplication in its original medical term was originally depicting the loop of Henle COMPLETE mechanism. I made that clear, and showed that in engineering today the term has shifted to mean only the gradual pumping. פשוט pashute ♫ (talk) 11:46, 9 May 2014 (UTC)

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