Talk:Psychrometrics

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Contents 1 Does anyone know the relationship between <dewpoint,dry temp> and wetbulb? 2 Dew Point Formulas 3 Mollier diagram 4 Inappropriate editorialization 5 Sections on dry- and wet-bulb temperatures seem redundant

[edit] Does anyone know the relationship between <dewpoint,dry temp> and wetbulb?

I've looked around the net and there seems to be a lack of formulae. Looking at the graph the wet bulb temps appear to be a constant gradient intersecting the saturation curve but how is this derived? njh 10:16, 11 January 2006 (UTC)

See Arden_Buck_Equation and references therein. The relationship is not a matter of definition, but relates to the physics of water and air. So the curve involved has to be measured. ArthurOgawa 00:08, 23 September 2007 (UTC)

[edit] Dew Point Formulas

This calculation is trickier than it looks. The standard source is the ASHRAE Handbook: Fundamentals. Look in Chapter 6, Psychrometrics, under Numerical Calculations of Moist Air Properties, to find what you are looking for. Most libraries should have a copy in the reference section. Note that it's published in English and metric editions. Tex 16:15, 20 February 2006 (UTC)

Not in Australia :-(. I can probably deduce it from the Clausius-Clapeyron relation though. Thanksnjh 20:54, 20 February 2006 (UTC)

The relevant chapter can be downloaded from the ASHRAE website as a PDF file, for a fee which is greater than nominal but not outrageous. I think it is USD 50. Tex 23:39, 20 February 2006 (UTC)

[edit] Mollier diagram

This external link [1] shows the relation between the Mollier diagram and the Psychrometric chart. 57.66.65.38 10:25, 11 April 2006 (UTC)

This is a little confusing because in fact several different thermodynamic diagrams are known as "Mollier diagrams". The most common is the enthalpy-entropy, or hs diagram. Probably the next most common is the pressure-enthalpy, or ph diagram. In fact I have never heard the enthalpy-composition diagram, as discussed here, called a Mollier diagram, but apparently it can be. Old Mollier must have really been working hard in those days! Tex 15:12, 11 April 2006 (UTC)

See Richard Mollier. Any diagram using enthalpy as one of its axes can be called a Mollier diagram, by decree of some physicists at a conference in 1923. ArthurOgawa 00:42, 23 September 2007 (UTC)

[edit] Inappropriate editorialization

Under the heading Psychrometric Chart, Relative Humidity, Rkinch added

The notion that air "holds" moisture, or that moisture dissolves in dry air and saturates the solution at some proportion, is an erroneous (although widespread) concept.

Frankly, I do not see Rkinch's point. In what way is the condensation of water out of, say, air not a manifestation of the saturation of a solution? I propose removing this language as a gratuitous editorialization (the claim is neither supported nor explained). Or, a reference to an explanation should be added. ArthurOgawa 00:42, 23 September 2007 (UTC)

[edit] Sections on dry- and wet-bulb temperatures seem redundant

The text below the chart already discusses the concepts of dry- and wet-bulb temperatures. Wiki articles exist for both concepts, and the text below the chart links to those articles.

I tried to fix the wet-bulb temperature section some, but it became too much of a time sink to correct it and to coordinate with the information provided beneath the chart and in the existing wet-bulb temperature article.

The discussion here about a wet-bulb thermometer is somewhat misleading. Will a moist wick on the bulb of a thermometer always cause its reading to drop? No. And if does drop, it won't drop below a limiting value.

Why evaporation causes cooling isn't explained. And this article doesn't seem like the place to explain that. -Ac44ck (talk) 03:44, 25 March 2008 (UTC)