|
All of these equations are based on measurements in °F. The
equations have been tested and they work perfectly. To utilize an
equation, copy and paste it into a text editor such as Microsoft
Notepad, which comes with every version of Windows. Make sure that
Format>Word Wrap is not active. Next, copy the equation (Edit>Select
All>Edit>Copy) from the text editor and paste into a spreadsheet
program such as Microsoft Excel. Finally, in the spreadsheet use
Edit>Replace to replace the temperature or humidity names, such as
DB or WB, with the cell names for the cells that contain the actual
measurements, such as A1 or C3. All equations were tested using this
method, and they worked perfectly.
**********************************************
To convert Dry Bulb temperature (DB) and
Wet Bulb temperature (WB) measured with
a sling psychrometer into WBGT:
WBGT=
((((DB+WB)/2)-10.068)/0.8636)
This equation is based on unpublished data generated by the author.
**********************************************
Relative Humidity (RH) based on Dry Bulb (DB) and Wet Bulb (WB)
Temperatures:
RH= 100 * ((Exp(((16.78 * ((WB - 32) * 5 /
9)) - 116.9) / (((WB - 32) * 5 / 9) + 237.3))) - ((101.325) * (((DB
- 32) * 5 / 9) - ((WB - 32) * 5 / 9)) * ((0.00066) * (1 + (0.00115 *
((WB - 32) * 5 / 9)))))) / (Exp(((16.78 * ((DB - 32) * 5 / 9)) -
116.9) / (((DB - 32) * 5 / 9) + 237.3)))
**********************************************
Equations describing Kulka and Kenney's criteria are as follows:
Maximum compensable Relative Humidity (RH) for a given Dry Bulb
temperature (DB):
Full Uniform:
RH =
(-75620+(3455*(DB))+(-59.15*(DB^2))+(0.45*(DB^3))+(-0.001284*(DB^4)))+22.80698
For Full Uniform except for short instead of padded pants:
RH =
(-0.0523*(DB^2)+(7.2018*DB)-170.42
For T-shirt and shorts:
RH=
(-3.9611*DB)+442.06
**********************************************
This equation was derived from the author's own data, with
publication as listed
in the References section.
WBGT = Estimated Playing Field Wet Bulb Globe Temperature, HI = Heat
Index at a
nearby airport.
WBGT=
(HI*0.4876)+39.986
Accuracy for this equation is ± 2°F (that is, 1 Standard deviation =
2°F). Unfortunately, this equation is only
accurate within a fairly narrow temperature range, and should not be
in general use. The Airport Data-based calculators using Relative
Humidity or Dew Point Temperature are much more reliable. If for
some reason you want to use the Airport Heat Index to WBGT
Calculator in spite of these shortcomings,
here is the link.
**********************************************
This is the equation for conversion of Dry Bulb Temp (T) in °F
and Relative Humidity (RH) as a whole number
(that is, RH=76, not RH=76%) into Wet Bulb Temperature (WB) in °F,
including a correction factor to bring the calculation result into
very close agreement with standard calculators:
WB=((((((0.00066*100)*((T-32)*(5/9)))+(4098*(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3)))))/((116.9+237.3*LN(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3))))))/(16.78-LN(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3))))))+237.3)^2*(116.9+237.3*LN(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3))))))/(16.78-LN(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3))))))))/((0.00066*100)+(4098*(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3)))))/((116.9+237.3*LN(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3))))))/(16.78-LN(((RH/100)*(0.611*EXP(17.27*((T-32)*(5/9))/(((T-32)*(5/9))+237.3))))))+237.3)^2)))*1.8)+32)-(1/(0.0423*(2.71828182845904^(0.0786*RH))))
**********************************************
This is the equation for conversion of Dry Bulb Temp (T) in °F and
Dew Point Temp
(DP) in °F to Wet Bulb Temp in °F:
WB= ((((((((0.00066 * 101.3) * ((DB - 32)
* 5 / 9)) + (((4098 * (0.6108 * (2.7182 ^ ((17.27 * ((DP - 32) * 5 /
9)) / (((DP - 32) * 5 / 9) + 237.3))))) / ((((DP - 32) * 5 / 9) +
237.3) ^ 2)) * ((DP - 32) * 5 / 9))) / ((0.00066 * 101.3) + ((4098 *
(0.6108 * (2.7182 ^ ((17.27 * ((DP - 32) * 5 / 9)) / (((DP - 32) * 5
/ 9) + 237.3))))) / ((((DP - 32) * 5 / 9) + 237.3) ^ 2))))) -
((0.0819 * (((DB - 32) * 5 / 9) - ((DP - 32) * 5 / 9))) - 0.5718)) *
1.8) + 32)
This equation result
is adjusted using a difference matrix procedure, and provides WB
results that are in very close agreement with standard calculators.
(Details available upon request.)
**********************************************
The US NWS Heat Index (HI) is based on a table constructed by
Steadman and
published in 1979. It is only intended to be used at Dry Bulb
temperatures above
70°F, and the equation listed below defaults to
Dry Bulb temperature=Heat Index for temperatures below 70°F. After many requests, the NWS published an equation that
describes this
table. This equation works best at Dry Bulb temperatures above
80°F. DB = Dry
Bulb temp in °F, RH = Relative Humidity (e.g., RH = 64% would be
64).
Heat
Index=IF(DB<70,DB,16.923+((1.85212*10^-1)*DB)+(5.37941*RH)-((1.00254*10^-1)*DB*RH)+((9.41695*10^-3)*DB^2)+((7.28898*10^-3)*RH^2)+((3.45372*10^-4)*DB^2*RH)-((8.14971*10^-4)*DB*RH^2)+((1.02102*10^-5)*DB^2*RH^2)-((3.8646*10^-5)*DB^3)+((2.91583*10^-5)*RH^3)+((1.42721*10^-6)*DB^3*RH)+((1.97483*10^-7)*DB*RH^3)-((2.18429*10^-8)*DB^3*RH^2)+((8.43296*10^-10)*DB^2*RH^3)-((4.81975*10^-11)*DB^3*RH^3))
Here is the link to a NWS
Heat Index Calculator.
**********************************************
Contact
Us
|