Afghan Energy, Chemical & Mining Industries resource for Renewable Energies, Irrigation & Sustainable Industries. |
Formula's and other Scientific StuffTo Calculate the Net Energy in Small Hydro Applications An easy formula for figuring the net energy in a falling stream of water is the head multiplied by volume in usgpm divided by 3960 = horsepower multiplied by .746 (convert hp to kW) and then multiplied by 60% ( turbine, generator and waterline losses etc). e.g. (200 feet head times 300 usgpm = 60,000 divided by 3960 = 15.15 hp multiplied by .746 = 11.3 gross kW multiplied by 60% efficiency = 6.78 net kW. Losses are attributed to 80% turbine efficiency, 85% generator efficiency, and 10% friction losses in the penstock. (e.g. .8 x .85 x .9 = 61.2%) The same formula expressed in a metric equivalent would
be Flow (Q expressed in Liters/sec) x H (expressed as Head in Meters) x
net losses (factor of 6, {60% efficiency}, depending upon
exact losses) To Calculate the water flow in CFS over a Suppressed Weir To calculate the discharge flow of water over a
suppressed weir, the following formula is a good approximation. e.g. 3.33 x 8 feet wide x 2 feet discharge over weir = 3.33 x 8 x 2.828 = 75.38 CFS or 2nd e.g. 3.33 x 6 feet wide x 8 inches overflow = 3.33 x 6 x .64952 (square root of .75 x.75 x .75) = 12.97 CFS Note: The water level must be measured a good 3-4 feet before the discharge weir, and there should be a clear drop of the water into a lower pool of water to be fairly accurate. Rules Relative to the Circle To find Circumference: Multiply diameter by 3.1416, or divide diameter by 0.3183 To Find Diameter: Multiply circumference by 0.3183, or divide circumference by 3.1416 To Find Radius: Divide diameter by 2, or multiply circumference by 0.15915, or divide circumference by 6.23318 To Find Area: Multiply circumference by 1/4 of the diameter, or multiply the square of the diameter by 0.07958, or multiply the square of 1/2 diameter (radius) by 3.1416 To Find Surface of a Sphere: Multiply the diameter by the circumference, or multiply the square of the diameter by 3.1416, or multiply 4 times the square of radius by 3.1416 To find the Volume of a Sphere: 4/3 pi
r3 e.g. A four foot balloon= 4 x 3.1415927 x 2 x 2 x 2
= 33.51 cubic
ft To Find the Curvature of the Earth: Take the radius
of the earth squared, plus the distance you are measuring Metric Conversion
Tables When you know
Multiply by
To Find
Symbol Imperial Length Metric
Inches
2.54
centimeters
cm
centimeters
.39216
Inches Area
Square Inches
6.45
Square Centimeters
cm2 Mass
Ounces (avoir.)
28.35
Grams
g
Fluid Ounces
28.41
Milliliters
ml
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