# Technical Equations

## Technical Equations

Centrifugal Force    Concentration     Flow Heating and Cooling    Humidity
Viscosity     Ohm's Law

Centrifugal Force

Relative centrifugal force

rcf = (11.18 x 10-6) RN

R = rotating radius in cm
N = rotation speed in rpm

Concentration
 Molar (M) = Moles of soluteLiters of solution
 Weight % = Grams of solute x 100%     Grams of solute + grams of solvent
 Volume % = Liters of solute x 100%Liters of solution
 ppm = mg of solutekg of solution = mg        Liters of water

Flow

CV factor

 Q = CV (G/ΔP)1/2

Q = flow rate (GPM)
CV = flow coefficient
G = specific gravity
ΔP = pressure drop (psi)

Heating and Cooling

Cooling capacity of chillers

 Btu/hr = ΔT (°F) x Specific heat of fluidflow rate (GPM)

Specific heat of water = 500 Btu/hr/GPM/°F
Specific heat of oil = 350 Btu/hr/GPM/°F

Heating water in tanks

 kW = Volume (gallons) x ΔT (°F)325 x Heat-up time (hours)

Heating oil in tanks

 kW = Volume (gallons) x ΔT (°F)800 x Heat-up time (hours)

Heating flowing water
kW = Flow (GPM) x ΔT (°F) x 0.16

Humidity

Absolute humidity (as g/m3)

 D = 804        1 + 0.00633t x e   PO
 D = H   100 x 804        1 + 0.00633t x e   PO

Dew point temperature (as °C)

 T = 237.3/7.5 - 1log e - 0.786
 e = H   100 x eS
 eS = 6.1078 x 107.5t/(237.3 + t)

Relative humidity (as % RH)

 RH = e  eS x 100 = D  DS x 100

H = relative humidity (% RH)
PO = standard air pressure (mm Hg)
D = absolute humidity (g/m3)
e = water steam pressure (mm Hg)
DS = absolute humidity in saturation (g/m3)
eS = saturated water steam pressure (mm Hg)
t = temperature (°C)
T = dew point temperature

Viscosity

Absolute viscosity = kinematic viscosity x density

density = units of specific gravity or g/mL
(eg. poise = stokes x g/mL)

Ohm's Law

Volts

 Volts = √Watts x Ohms = Watts  Amperes = Amperes x Ohms

Amperes

 Amperes = VoltsOhms = WattsVolts = √ WattsOhms

Ohms

 Ohms = Volts    Amperes = Volts2Watts = Watts    Amperes2

Watts

 Watts = Volts x Amperes = Amperes2 x Ohms = Volts2Ohms