This app was designed for:

Mechanical Engineers,
Testing and Balancing Technicians,
HVAC designers and Field Technicians,
Plant Mechanical Departments,
Building Managers and Mechanics,
Operating Engineers,
Students, or anyone else who has an interest in the effects of changing the speed of a fan in a fixed system.

Initial inputs are, motor rpm, fan sheave pitch diameter, fan rpm, motor horsepower, brake horsepower, static pressure, motor and fan shaft center-to-center distance, cfm, and fan critical shaft speed. Once they are entered using an intuitive calculator like keyboard, the iPhone is rotated to the landscape mode where the motor sheave pitch diameter is incremented or decremented, simultaneously yielding new values for brake horsepower, static pressure, fan rpm, belt pitch length, and cfm. There are warnings if the brake horsepower exceeds the motor horsepower, or if the fan RPM exceeds the critical shaft speed of the fan.

Fanlaws gives the user the ability to answer questions such as:
How much air can I get from this fan using the current motor?
Can I reduce the motor size for greater efficiency and still have the desired CFM?
What sheave size do I need to increase the air volume to X CFM?
What new belt size will I need? Will the static pressure be too great?

Fanlaws lets the user play - what if ? - all day long while visually watching multiple values change as the motor sheave size is incremented and decremented.
It is an essential tool for anyone designing or working on fan systems.

-Also-
consider getting
(Refrigerants PressTemp HVACR)
It's another great tool for the refrigeration tech.

For more information and a video tutorial visit http://www.fanlawsapp.com