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Evaporation Rate Calculation: 4300/5200 Meters

Evaporation Rate

It is calculated on the K4300 as well as on the K5200. The formula used is:

E = 5.275([Tc + 17.778]2.5 – Rh[Ta +17.778]2.5)(Ws + 4.02336) * 10-6


E = evaporation rate in kg/m2/h

Tc = Temperature of Concrete in C

Ta = Ambient Temperature in C

Ws = Wind Speed in km/h

Rh = relative humidity in percent / 100. Example 40% = .4

This formula is derived from Estimating Evaporation Rates to Prevent Plastic Shrinkage Cracking but has been modified slightly to solve an issue that faced the Kestrel developers when this measurement was initially developed 1. The result yields the same answer as the Imperial formula's converted to metric.

1 See supporting documents 'Re: Evaporation Rate.txt' and 'K4 concrete equation 20070604.xls' for explanation and validation of this formula.
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