How To Calculate Compressor Capacity

Compressor Capacity Formula:

\[ CFM = Displacement \times RPM \times Volumetric\ Efficiency \]

Capacity (CFM):

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1. What Is Compressor Capacity?

Compressor capacity refers to the volume of air delivered by a compressor per unit time, typically measured in cubic feet per minute (CFM). It represents the actual air output available for pneumatic tools and systems.

2. How Does The Calculator Work?

The calculator uses the compressor capacity formula:

\[ CFM = Displacement \times RPM \times Volumetric\ Efficiency \]

Where:

\( Displacement \) — Theoretical volume displaced per revolution (ft³/rev)
\( RPM \) — Rotational speed of the compressor (revolutions per minute)
\( Volumetric\ Efficiency \) — Ratio of actual to theoretical capacity (unitless)

Explanation: The formula calculates the actual delivered air capacity by accounting for mechanical losses through volumetric efficiency.

3. Importance Of Compressor Capacity Calculation

Details: Accurate capacity calculation is essential for proper compressor selection, system design, ensuring adequate air supply for tools, and optimizing energy efficiency in pneumatic systems.

4. Using The Calculator

Tips: Enter displacement in ft³/rev, RPM in revolutions per minute, and volumetric efficiency as a decimal (e.g., 0.85 for 85%). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is volumetric efficiency?
A: Volumetric efficiency is the ratio of actual air delivered to the theoretical maximum capacity, accounting for factors like clearance volume, leakage, and valve losses.

Q2: What are typical volumetric efficiency values?
A: Reciprocating compressors typically range from 60-90%, rotary screw compressors 85-95%, and centrifugal compressors 80-90%, depending on design and condition.

Q3: Why is CFM important in compressor selection?
A: CFM determines if a compressor can supply enough air for your tools and equipment. Undersized compressors lead to pressure drops and reduced performance.

Q4: How does altitude affect compressor capacity?
A: At higher altitudes, air density decreases, reducing the mass flow rate and effective capacity. Compressors may need to be oversized for high-altitude applications.

Q5: What's the difference between displacement and delivery?
A: Displacement is the theoretical volume the compressor could move, while delivery is the actual air output after accounting for efficiency losses.