Technical Equations

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 solute Liters 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 solute kg of solution

=

mg         Liters of water

 

Flow

C_V factor

Q =	CV      (G/ΔP)1/2

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

 

Heating and Cooling

Cooling capacity of chillers

Btu/hr =

ΔT (°F) x Specific heat of fluid flow 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 - 1 log 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)
P_O = standard air pressure (mm Hg)
D = absolute humidity (g/m³)
e = water steam pressure (mm Hg)
D_S = absolute humidity in saturation (g/m³)
e_S = 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 =

Volts Ohms

=

Watts Volts

= √

Watts Ohms

Ohms

Ohms =

Volts     Amperes

=

Volts2 Watts

=

Watts     Amperes2

Watts

Watts = Volts x Amperes = Amperes2 x Ohms =

Volts2 Ohms

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