Still water droplet evaporation rate (help using Maxwell's formula please)

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Discussion Overview

The discussion revolves around the evaporation rate of water droplets, particularly in the context of anhydrobiosis in certain organisms. Participants explore Maxwell's formula and its application to calculate the initial evaporation rate of droplets, considering factors such as temperature, diameter, and solute concentration.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant describes the biological context of anhydrobiosis and the role of trehalose in protecting organisms from freezing and dehydration, expressing a desire to understand Maxwell's formula for evaporation rates.
  • Another participant suggests a different form of Maxwell's formula, referencing a specific equation from a source, and emphasizes the importance of understanding units in the context of the formula.
  • A participant expresses gratitude for the new information and acknowledges the need to revisit their understanding of the relevant equations, particularly the distinction between circumference and surface area.
  • Another participant mentions reviewing literature by Seaver and Fuchs, noting that Seaver's work focuses on smaller droplets and confirms that larger droplets align with Maxwell's predictions, while Fuchs provides a more accessible approach to the equations involved.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the application of Maxwell's formula, and there are multiple competing views regarding the best approach to understanding and applying the formula for evaporation rates.

Contextual Notes

Participants express uncertainty about the correct units and the dissociation coefficient in Maxwell's formula, indicating that there may be missing assumptions or dependencies on specific conditions that have not been fully resolved.

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So I've observed the animal I am studying dry it's self (a survival mechanism called anhydrobiosis) to avoid freezing (laseration by ice crystals). Life forms given time produce a number of protectants in order to survive. Trehalose a sugar is produced to 2-4%. This will act as an antifreeze to aprox minus 4 C. Additionally Trehalose appears to act as a water substitute protecting structures from failing due to dehydration. Protein molecules deprived of water will fold into new incompatible structures collapsing the house of cards that is life. I am trying to write a paper for publication and I want to master this equation ( I = 4 Pi D R (c1-c2)). I have spent day's trying but still do not have a clear idea. Examples I have found use it as a reference point and mostly a starting point to add variables ( velocity and heat flows ) formulated with advanced calculus most of all fail because the added variables are unstable in nature and then the next researcher starts again with Maxwell. You get a sense of the genius of Maxwell by leaving the obvious ( velocity and heat) out. I am not a genius and am unable to read around the advanced calculus content of these journal articles. I just want a sense of the maximum evap rate as a percent of drop mass. One could also call it initial evap rate. My drops (the organism) temperature, diameter and concentration of solutes will immediately change with the evaporation. My biggest problem with the formula has to be with the dissociation coefficient. I have read "the quantity of gas traveling one cm through one cm x cm. Then I'll see 1 m x 1m so in that case is the travel distance a meter or still one cm through orifice of area x. Not mentioned is the units of the quantity ( example grams, moles etc ). I saw something like D = 0.022 + (0.134 c1-c2). Density effects D. D for water is different than for methane etc. I think it's different for different temperatures. I want to carefully get the correct D, conserve my units so the final answer makes sense and is correct. I don't want to be forced to print a retraction. Most of the work that I could find using this rarer Maxwell formula is for metereology and some evaporator uses, spray use or to explain other phenomonom like sailors being pelted with dry salt crystals while at sea.
 
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I googled this topic: See https://www.tandfonline.com/doi/pdf/10.1080/02786828408959006
Equation (3) is a better form of Maxwell's formula. The effusion rate (number per second per unit area) ## R=\frac{n \bar{v}}{4} ## is a well-known result that can be derived with some calculus.(##n ## is the concentration=number of particles per unit volume). I don't know that you have your units right in the OP, but again see equation (3). The ## 4 \pi R^2 ## in that formula is the surface area of the droplet. (3) makes complete sense.:welcome:
 
Charles Link said:
I googled this topic: See https://www.tandfonline.com/doi/pdf/10.1080/02786828408959006
Equation (3) is a better form of Maxwell's formula. The effusion rate (number per second per unit area) ## R=\frac{n \bar{v}}{4} ## is a well-known result that can be derived with some calculus.(##n ## is the concentration=number of particles per unit volume). I don't know that you have your units right in the OP, but again see equation (3). The ## 4 \pi R^2 ## in that formula is the surface area of the droplet. (3) makes complete sense.:welcome:
Thank you ever so much. It will take me time (as probably days) to digest and use the new search terms to learn what I can on my own before asking for more help. Thanks again. I was mistified why circumference and not surface area was in my equation.
 
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I looked at the Seaver (1983). I wish I could understand it fully (or even partially). I forgot calculus it came easily and went just as easily (40 years ago). Seaver though is developing a formula for drops smaller than 2 microns and Seaver confirms any drop larger is Maxwellian (ie yields best correlation to experimental data). Taking your lead of Seaver's equation (3) I am reading Fuchs (1959) rendition that in part is available on Google books and I'll see where it takes me. Fuch's is good about symbols and in conserving units and actually provides a Maxwell gas law combo equation that will let me input my partial pressures without the risk of deriving the wrong equation on my own. Algebra I am still sound on and Fuchs first chapter is Algebraic.
 
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