## TABLE OF CONTENTS - OHM'S LAW FOR FLUIDS

Page 1- How to calculate flow using Ohm's Law for Water
- Pressure Drop = GPM squared times Resistance
- HOW TO SIMPLIFY WATER CIRCUITS
- RESISTANCES IN SERIES
- RESISTANCES IN PARALLEL
- PUMPS AND PRESSURE SOURCES

NOTE - Ohm's Law is not as useful working with closed loops which have individual pressure sources

Page 2- RESISTANCE VALUES FOR 100 FEET OF COMMON HOSE
- RESISTANCE VALUES FOR COMMON NOZZLES
- Formula for Calculating Nozzle Resistance
- Two different ways to think of nozzle pressure
- EXAMPLE 1 Pump at 65 psi, 200 feet of 1-1/2 inch hose, 5/8 inch smoothbore

- EXAMPLE 2a Calculate flow in gpm for one 2 inch hose feeding two smaller handlines
- STEP 1 Add the hose resistance and the nozzle resistance together to give an equivlent
- STEP 2 Add the hose resistance and the nozzle resistance together to give an equivalent
- STEP 3 Convert the two equivalent resistances from Step 1 and Step 2 (they are in )
- STEP 4 Add the resistance calculated in Step 3 to the resistance of the 2 inch hose
- STEP 5 Solve for flow

- EXAMPLE 2b Calculate the flow in in the individual hoses.
- SOLUTION We have just found the total flow (219.8 gpm) and we know that all FLOW DIVIDES between two parallel resistances based on how the resistances

- EXAMPLE 2c Calculate the pressure at each nozzle and at the wye.
- SOLUTION We're going to do this three different ways, just for practice. None of them are hard.

THE EASIEST WAY - Use EK's Friction Loss and Nozzle Flow Calculator. We already know the ... - Chart Step 1 - Find the pressure at the wye. Draw a line between the 2 inch hose mark and ...
- Chart Step 2 - Find the pressure at the 5/8 smoothbore, which we already know is flowing ...
- Chart Step 3 - Find the pressure at the 7/8 smoothbore, which we already know is flowing ...
- NOW - Let's do it with numbers. We know the flow, so it's easy to work out the pressures.
- Numbers Step 1 - Find the pressure at the wye. The pressure drop in the 2 inch hose equals ...
- Numbers Step 2 - Find the pressure at the 7/8 nozzle. The pressure outside the nozzle, in the ...
- Numbers Step 3 - Find the pressure at the 5/8 nozzle. The pressure outside the nozzle, in the ...
- The nozzle pressures could also be found by calculating the friction losses in the hoses ...
- FINALLY - Let's find the pressure at the wye and at the two nozzles without using the flow.
- Ohm's Law Step 1 - Find the pressure at the wye. We need 3 things: the pump pressure, ...

- How Pressure Divides (General Case)
- In fact, this same thing works for any number of resistances in series - the pressure across ...
- The interesting point is that you don't need to know the flow to see how the pressure divides.
- Next, we'll work out nozzle pressures, using the pressure at the wye as our "total pressure" ...

- Talking about Power (Without Numbers)
- POWER - Power is the rate at which energy is generated or used, in terms of Energy per Unit ...
- Three common ways to describe Power are foot-pounds per second, Horsepower and Watts.
- HP = gpm x psi / 1714.55
- This is the basic formula - if you know the gpm and the psi, just go ahead ...
- Let's look at crimps in a hoseline. Do they matter?
- For a given amount of flow, the pump must supply a certain amount ...
- But, and this is important, when the pump pressure goes up 20 percent, then for the same flow, the horsepower also goes up 20 percent.

- HORSEPOWER CALCULATIONS USING FLUID WATTS.
- THE BASICS
- For example, a pump which adds 90 psi to a flow of 125 gpm requires 6.56 horsepower to ...
- The HP formula given above is basic, but it's not always the easiest formula to use.
- The trick is to work with fluid watts, where 1 Fluid Watt equals 1 gpm pressurized by 1 psi ...
- 1714.55 fluid watts equals one horsepower
- Other Formulas
- Fluid Watts = Gpm x Psi

- THE VIRTUAL NOZZLE and Bernoulli's Equation
- The Frictionless Pump and Hose
- TRASH PUMP Part 1, with warts - something is missing. What is it?
- In our model, the pump is the pressure head, and the virtual nozzle is the size of the hole.
- The value of the virtual nozzle depends only on its diameter, and is the same as the resistance ...
- Virtual Nozzle Resistance Values for 3 Common Hose Sizes

- Portable Pond Fill Times with and without a Hose Crimp
- Power Calculations for the Pond Fill Example including at the Virtual Nozzle ...

- Calculating the Velocity Head using Ohm's Law
- Bernoulli's Equation and related topics
- Centrifugal Pumps
- Nozzles
- Pitot Tubes
- Hydrant Loading

**FUTURE ARTICLES**scheduled for the Fall - Winter 2011