# Talk:Mass balance

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## Mass balance models

I noticed through a Google search that someone had put up a request for Mass balance models. Rather than moving my contribution mass balance I made a redirect since I think that mass balance is a better term than mass balance models, I'll try to explain why: The term model can be interpreted in many, many ways, so many that the term has almost lost its meaning. What I as a chemical engineer do (in this field) is to write down mass balances (and energy balances) for my systems. In doing that I have to make simplifications and assumptions, i.e. the mass balance is a model of reality, not reality itself. Once I have my balances for mass and energy I translate that into a computer model, either a standalone computer program, or as a routine that can be used inside another program. From a more philosophical point of view, everything we experience is a model, since we have no (?) way of knowing for sure that anything exist.

So, to put it short, I rather see a mass balance entry in the wikipedia than a mass balance models entry. Saittam 12 Aug 2005

• I keep doing newbie mistakes and fail to see them directly. Unfortunately I have to give less attention to wikipedia for a while so I leave things as they are Saittam 11.30 17 Aug 2005 (CET)

## Mathematical statement of conservation of mass

Can someone provide a mathematical statement of the conservation of mass, in the form of partial derivatives or some kind of governing equation? Maybe what I'm looking for is a continuity/conservation type of equation. Problem is, I don't know what I don't know! User 202.156.6.54 January 1, 2006

I've added a link to Continuity equation but hesitate to add much in the Mass balance article: I haven't looked to closely, but I think the following equation is still lacking in wikipedia:

${\displaystyle {\partial C_{A} \over \partial t}+v\nabla C_{A}=D_{AB}\nabla ^{2}C_{A}+R_{A}}$

which relates the derivative of substance A (${\displaystyle {\partial C_{A} \over \partial t}}$) with the convection (${\displaystyle v\nabla C_{A}}$), the diffusion of substance A in substance B (${\displaystyle D_{AB}\nabla ^{2}C_{A}}$) and the reaction rate at which substance A is produced (${\displaystyle R_{A}}$). I hesitate, not because I think it shouldn't be in wikipedia somewhere, but because I don't know where to put it. If the equation above is to be included, I think it would be only proper to explain what it means, e.g. how to interprete it in different coordinate systems e.g. the cylindrical

${\displaystyle {\partial C_{A} \over \partial t}+v_{r}{\partial C_{A} \over \partial r}+v_{\theta }{1 \over r}{\partial C_{A} \over \partial \theta }+v_{\phi }{1 \over r\sin \theta }{\partial C_{A} \over \partial \phi }=D_{AB}\left({1 \over r^{2}}{\partial \over \partial r}\left(r^{2}{\partial C_{A} \over \partial r}\right)+{1 \over r^{2}\sin \theta }{\partial \over \partial \theta }\left(\sin \theta {\partial C_{A} \over \partial \theta }\right)+{1 \over r^{2}\sin ^{2}\theta }{\partial ^{2}C_{A} \over \partial \phi ^{2}}\right)+R_{A}}$

one might then continue to explain different simplifications, e.g. steady-state, no convection, etc. How to make this into a wikipedia entry rather than a wikibook entry is somewhat beyond my imagination though… Saittam Jan 3, 2006 19:14 CET

If you really want a mathematical statement, then a mass balance is a Taylor expansion of mass ignoring all higher orders than the first order derivative (with respect to time) of mass. (Saittam (talk) 21:46, 17 March 2010 (UTC))

## The use of material balance in Petroleum Engineering

In Petroleum Engineering, the term "Material Balance" represents Volume Balance. It primarily used to estimate volume of Hydrocarbon in-place in the subsurface reservoir. 203.146.126.2 07:05, 18 May 2007 (UTC)

That should come as no surprise. It simply follows from the basic concept of mass balance. If density remains constant a volume balance is analogous to a material balance. The same is true for energy balances which commonly are heat balances rather than balances of the sum of all forms of energy. BTW, I wont be doing much with this entry, but I wish good luck to anyone who has the energy to try to improve the article User:Saittam 15:00, 13 Aug 2007

Think this article should relate to information on the CSTR itself not modelling work related to the CSTR. I wanted to have something that described the anaerobic CSTR with diagrams of the digester design instead. Think this article should be renamed and or moved with a new article on CSTRs completed--Alex 10:23, 22 October 2007 (UTC)

I think this article requires information on mass balance as a concept, as well as its importance in an engineering context. I don't think that the article should be on CSTR modelling nor CSTRs themselves. For modelling and details surely this information should go under the CSTR article. User A1 14:11, 22 October 2007 (UTC)

I think that mass balances is a better term (I've never heard of mass balance modeling) and that it is an independent subject from CSTRs. However, CSTRs are based off of ideas that come from a mass balance. —Preceding unsigned comment added by Jlhbullfrog (talkcontribs) 23:43, 10 January 2008 (UTC)

Not immediately obvious, but the two previous responses indicate that they do not support merging mass balance and CSTR. I likewise cannot see any good reason to merge them. I will take down the banner. I also agree that "mass balance" need not involve any chemical reaction at all. The article focus at present is skewed. —DIV (128.250.80.15 (talk) 02:12, 2 May 2008 (UTC)

Mass Balance is a much wider reaching topic than its application to CSTRs. I would oppose the merger, but inclusion of a paragraph discussing its application to CSTRs with a main article link to CSTRs would be good.Thewellman (talk) 05:35, 1 July 2011 (UTC)

## rA = r − 1 − r1 seems to be wrong, if I'm not misstaken

If aA+bB->cC+dD then rA = a*r − 1 − a*r1 —Preceding unsigned comment added by 129.16.49.113 (talk) 13:35, 18 December 2008 (UTC)

## Ice sheets, probably wrong and to short to be helpful, deleted

The ice sheet example makes a lot of hidden assumptions and is probably wrong. Some of them are:

• I would be suprised if the ice is transported only top-bottom. I would assume a mixed mode transport.
• The snow will surely be compacted under 3km. It is also ice not snow, is it?
• These two alone would make it a mixed-flow, non constant volume thing, which cannot be handled like this.

LGreiner (talk) 12:16, 17 April 2013 (UTC) Afterthought: It may be useful to link to this place Glacier mass balance but it is rather disembugiation, really. LGreiner (talk) 16:37, 17 April 2013 (UTC)

## Assessment for WikiProject Engineering

There is a lot of good information here, but this article is devoid of reference citations. It shouldn't be difficult to pull reference citations from Perry's or any mass transfer text. Some more line diagrams would also help. I'm on a once-through pass of unassessed articles at the moment, but I hope to be back if no-one else picks it up first.Thewellman (talk) 05:35, 1 July 2011 (UTC)