| MadSci Network: Engineering |
Don. Your indoor evaporation rate requst is a little different from my experience. I was interested in outdoor cooling tower performance that required background environmental evaporation information to generate a general model for power plants. A review of the internet sites shows that there are no really good calculations to estimate the information you request. The emperical data collected over several years to get seasonal and daily variations, is about the most accurate. The time requirements to perform a full pan evaluation may be overkill for your needs, but if the interior environmental conditions are relatively stable, it may not take as long to generate a useable evaporation coefficient. A very complete reference to the Penman-Monteith equation is described in chapter 4 of the ACE Hydrology Handbook, published in 1996. It also shows the physical dimensions of a "type A" pan. Link: http://www.fao.org/doc rep/X0490E/x0490e08.htm Another web site written by the authors of the above chapter has many other links and state-by-state contact people who are knowledgeable in evaporation studies. Link: http://snow.ag.uidaho.edu/Classes/Hydrology/Reference_Materials/Ref _ET.html There is a high-school introduction to determining pan evaporation information at: http://vgc.sr i.com/projects/worldwatcher/gcv/Evap1.htm Sorry that I cannot give you a simple equation to estimate evaporation, but the process changes rate instant-by-instant as the local conditons change. The data must take into account the local air currents plus all the other criteria you mentioned. The emperical method takes some time to generate a reliable seasonal ET factor, but it will give you the best long- term model.
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