# Talk:Flash evaporation

## Extensive re-write

The article seemed to be focused only on the flash evaporation of a multi-component liquid and it did not discuss the evaporation of a single-component liquid at all. Also, some of the wording was confusing. Hence, I did an extensive re-write. I will complete the multi-component section with the next day or so. - mbeychok 05:11, 7 April 2006 (UTC)

I just finished the complete revision and expansion of this article. - mbeychok 07:34, 8 April 2006 (UTC)

## Confused

Is the fact that flash evaporators are isentropic true for both multi-component systems as well as single? What are some properties of all flash evaporators? 143.246.14.19 (talk) 18:07, 13 April 2010 (UTC)PhysicsStudent

Glad you brought this up, because I erred in stating that the flash evaporation of a single-component liquid is isentropic. An adiabatic process is isentropic only if the process is reversible. I have corrected the article to state that the flash evaporation of a single-component liquid is isenthalpic. answer you In any event, the equation given for a single-component liquid is correct. mbeychok (talk) 22:11, 14 April 2010 (UTC)
Now that I have checked the article history, I see that I originally wrote that flash evaporation of a single-component liquid was isenthalpic. The change to isentropic was made by an unregistered user on March 23, 2009. So the error was not mine after all. mbeychok (talk) 22:35, 14 April 2010 (UTC)
Whew, that's a relief... — Preceding unsigned comment added by 192.158.48.17 (talk) 12:42, 29 January 2015 (UTC)

## Derivation of Flash Evaporation Single Component & Definition of X

Mass Balance of initial and final liquid and vapour

${\displaystyle m_{i}=m_{f}}$
${\displaystyle m_{l,i}=m_{v,f}+m_{l,f}}$

${\displaystyle m_{l,i}h_{l,i}=m_{v,f}h_{v,f}+m_{l,f}h_{l,f}}$
${\displaystyle (m_{v,f}+m_{l,f})h_{l,i}=m_{v,f}h_{v,f}+m_{l,f}h_{l,f}}$
${\displaystyle m_{l,f}h_{l,i}+m_{v,f}h_{l,i}=m_{v,f}h_{v,f}+m_{l,f}h_{l,f}}$
${\displaystyle m_{l,f}h_{l,i}-m_{l,f}h_{l,f}=m_{v,f}h_{v,f}-m_{v,f}h_{l,i}}$
${\displaystyle m_{l,f}(h_{l,i}-h_{l,f})=m_{v,f}(h_{v,f}-h_{l,i})}$
${\displaystyle {\frac {(h_{l,i}-h_{l,f})}{(h_{v,f}-h_{l,i})}}={\frac {m_{v,f}}{m_{l,f}}}}$

or in articles original notation

${\displaystyle {\frac {m_{v,f}}{m_{l,f}}}={\frac {H_{u}^{L}-H_{d}^{L}}{H_{d}^{V}-H_{u}^{L}}}}$

The current article also suggests (from definition X = weight fraction vaporized) that X = m_vap ÷ m_total, where m_total = m_vap+m_liq, which is is the same definition as vapor quality. From the derivation, X should be defined as the 'ratio' of vaporised mass to remaining liquid.

${\displaystyle X={\frac {m_{v,f}}{m_{l,f}}}}$ — Preceding unsigned comment added by RedHotIceCube (talkcontribs) 14:15, 22 October 2015 (UTC)