Machinery's Handbook, 31st Edition
WINDCHILL AND VELOCITY 2875 Windchill Temperature.— Windchill temperature is a measure of the combined cool ing effect of wind and temperature. The formula below is used for calculating windchill by the National Weather Service (NWS) in the United States: . . . . F T V T V 35 74 0 6215 35 75 04275 Windchill Temperature 0.16 ° = + − + ^ ^ h h 0.16 where T = air temperature in ° F V = wind speed in miles per hour (mph) measured at NWS standard height, 33 feet The formula calculates the chilling effect of wind on the human body at 5 feet above the ground and assumes no influence caused by sunlight (that is, as if the temperature and wind speed measurements were made at night in clear sky conditions). Windchill temperature is only defined for temperatures at or below 50 degrees F and wind speeds above 3 mph. Bright sunshine may increase the windchill temperature by 10 to 18 degrees F. Wind Velocity to Pressure V P V P V P 5 0.1 35 4.9 65 16.9 10 0.4 40 6.4 70 19.6 15 0.9 45 8.1 75 22.5 20 1.6 50 10.0 80 25.6 25 2.5 55 12.1 100 40.0 30 3.6 60 14.4 The formula is P = 0.004 V 2 where V = wind velocity, mph; P = pressure, lbs/sq ft. Phonetic Alphabet A Alfa J Juliett S Sierra 1 One B Bravo K Kilo T Tango 2 Two C Charlie L Lima U Uniform 3 Three D Delta M Mike V Victor 4 Four E Echo N November W Whiskey 5 Five F Foxtrot O Oscar X X-Ray 6 Six G Golf P Papa Y Yankee 7 Seven H Hotel Q Quebec Z Zulu 8 Eight I India R Romeo 0 Zero 9 Nine Daylight Savings Time.— The Congress of the United States of America extended Day light Savings Time (DST) by about a month, effective from 2007. Before 2007, DST began at 2:00 AM on the first Sunday in April and ended at 2:00 AM on the last Sunday in October. Beginning 2007, DST begins at 2:00 AM on the second Sunday in March and ends at 2:00 AM on the first Sunday in November. Bel.— The bel is the fundamental division of a logarithmic scale for expressing the ratio of two amounts of power. The number of bels denoting such a ratio is the logarithm to the base 10 of this ratio. Thus, if P 1 and P 2 are two amounts of power, and N the number of bels denoting their ratio, then log N p p bels . The decibel is one-tenth of a bel and is commonly abbreviated as db. This unit is used extensively in the measurement of sound volume in telephone and radio transmission and reception, and in noise measurements of various kinds. 2 1 =
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