Environment Heat Index Calculation – Lab Report Example

Environment Heat Index calculation Heat index is an excellent measure of humidity and temperature because it takes both the factors into consideration. In order to measure heat index, it is important to know Wet Bulb Global temperature (WBGT). WBGT estimates the maximum number of hours for people working outside (Duarray 5) and has the following three measurements: Globe temperature, air temperature and Wet bulb temperature.
For outdoor and indoor conditions with no solar WBGT is given by:
WBGT = 0.3 GT + 0.7 NWB (1)
Also, for outdoors with a solar loss
WBGT = 0.1 DB + 0.2 GT + 0.7 WB (2)
Where, DB=Dry bulb temperature, GT= Globe temperature and NWB= natural wet bulb temperature
On the other hand, relative humidity that is also a good estimate for heat index can be obtained from the following formulae
RH = 100% x (E/Es) (3)
“Where, E = E0 x exp [(L/Rv) x {(1/T0) - (1/Td)}], Es = E0 x exp [(L/Rv) x {(1/T0) - (1/T)}]
Where E0 = 0.611 kPa, (L/Rv) = 5423 K, T0 = 273 K (Kelvin)” (Duarray 5)
Finally, dew point is also another significant estimate and is given by
“Td = T - ((100 - RH)/5.)” (4) (Duarray 5)
Where Td and T are the dew point temperature and observed temperature respectively.
Finally, Environment Heat Index Calculation is given by
  “HI = -42.379 + 2.04901523*T + 10.14333127*RH - .22475541*T*RH - .00683783*T*T - .05481717*RH*RH + .00122874*T*T*RH + .00085282*T*RH*RH .00000199*T*T*RH*RH” (Durray 5)
Where, T = temperature (o F), RH= % relative humidity and HI = heat index.
Objectives
I. Estimate WGBTin and WGBTout
II. Calculate the relative humidity
III. To estimate the dewpoint
Materials and Instruments
Three thermometers (Globe, Wet and Dry)
Steel bag
Distilled water
Stand
Methodology
All the materials were set up and reading taken
Initial measurements A
Wet= 14.5, Globe= 22 and Dry= 19
Final reading after 10 minutes
Wet= 14.7, Globe = 21.4 and Dry = 20.8
Results
Analogue reading
Wet= 14, Globe = 21.4 and Dry = 20.8
Digital reading
Wet= 13.8, Globe = 23.7 and Dry = 20.8
Conclusion
For WBGT indoors
WBGT = 0.3 GT + 0.7 NWB
= (0.3 *23.7) + (0.7 *13.8) = 16.77
WBGT outdoor
WBGT = 0.1 DB + 0.2 GT + 0.7 WB
= (0.1 *20.8) + (0.2*23.7) + (0.7*13.8) =16.48
The WBGT (in door) is 16.77 which can be categorized as low risk level, though risk level still exist while the WBGT (outdoor) is 16.48, this can also be classified as low. For this reason, the workers who are working under this conditions are not exposed to harsh weather. The values that were used to calculate the WBGT were obtained from the digital reading because they had high precision.

Work Cited
Duarray, James. Environmental Science. , 2013. Print.