Cubic inches per minute (in³/min) to Imperial Gallons per Second (imp-gal/s) conversion

What is the cubic inch per minute?

What is Cubic Inches per Minute?

Cubic inches per minute (in³/min or CFM) is a unit of measure for volume flow rate. It represents the volume of a substance (typically a gas or liquid) that flows through a given area per minute, with the volume measured in cubic inches. It's a common unit in engineering and manufacturing, especially in the United States.

Understanding Cubic Inches and Volume Flow Rate

Cubic Inches

A cubic inch is a unit of volume equal to the volume of a cube with sides one inch long. It's part of the imperial system of measurement.

Volume Flow Rate

Volume flow rate, generally denoted as $Q$, is the volume of fluid which passes per unit time. The SI unit for volume flow rate is cubic meters per second ($m^3/s$).

Formation of Cubic Inches per Minute

Cubic inches per minute is formed by combining a unit of volume (cubic inches) with a unit of time (minutes). This describes how many cubic inches of a substance pass a specific point or through a specific area in one minute.

$$Q = \frac{V}{t}$$

Where:

• $Q$ = Volume flow rate (in³/min)
• $V$ = Volume (in³)
• $t$ = Time (min)

Applications and Examples

Cubic inches per minute is used across various industries. Here are some real-world examples:

• Automotive: Measuring the air intake of an engine or the flow rate of fuel injectors. For instance, a fuel injector might have a flow rate of 100 in³/min.
• HVAC (Heating, Ventilation, and Air Conditioning): Specifying the airflow capacity of fans and blowers. A small bathroom fan might move air at a rate of 50 in³/min.
• Pneumatics: Determining the flow rate of compressed air in pneumatic systems. An air compressor might deliver 500 in³/min of air.
• Manufacturing: Measuring the flow of liquids in industrial processes, such as coolant flow in machining operations. A coolant pump might have a flow rate of 200 in³/min.
• 3D Printing: When using liquid resins.

Conversions and Related Units

It's important to understand how cubic inches per minute relates to other units of flow rate:

• Cubic Feet per Minute (CFM): 1 CFM = 1728 in³/min
• Liters per Minute (LPM): 1 in³/min ≈ 0.01639 LPM
• Gallons per Minute (GPM): 1 GPM ≈ 231 in³/min

Interesting Facts

While there's no specific law directly associated with cubic inches per minute itself, the underlying principles of fluid dynamics that govern volume flow rate are described by fundamental laws such as the Navier-Stokes equations. These equations, developed in the 19th century, describe the motion of viscous fluids and are essential for understanding fluid flow in a wide range of applications. For more information you can read about it in the following Navier-Stokes Equations page from NASA.

What is the Imperial Gallon per Second?

The Imperial gallon per second (imp-gal/s) is a unit of volumetric flow rate, expressing the volume of liquid passing a point each second measured in Imperial (UK) gallons. It appears in British and Commonwealth engineering contexts such as pump ratings, water supply, and fuel handling.

Definition

One Imperial gallon per second equals one Imperial gallon of volume flowing every second. Since the Imperial gallon is defined as exactly 4.54609 litres, the flow rate converts directly to litres per second:

$$1\ \text{imp-gal/s} = 4.54609\ \text{l/s}$$

The Imperial gallon is fixed by definition as 4.54609 L exactly (originally the volume of 10 pounds of water). This makes it noticeably larger than the US liquid gallon of 3.785411784 L, so an Imperial gallon per second delivers about 20% more volume than a US gallon per second.

Origin and History

The Imperial gallon was established by the British Weights and Measures Act of 1824, defined as the volume of ten pounds of distilled water at 62 °F. In 1985 the UK redefined it in metric terms as exactly 4.54609 litres. As a rate unit, gallons per second and the more common gallons per minute grew out of the need to specify pump and pipe throughput during the industrial era.

Law and Notable Facts

The Imperial gallon remains a legally recognised unit in the United Kingdom, though the litre is the primary trading unit under metrication. It is distinct from the US gallon: the Imperial gallon (4.54609 L) is roughly 20% larger than the US liquid gallon (3.785 L), so flow figures quoted in "gallons" must always specify which system. A flow of 1 imp-gal/s corresponds to 60 Imperial gallons per minute or 3,600 per hour.

Real-World Examples and Conversions

• A flow of 1 imp-gal/s equals 4.54609 L/s, or about 272.77 litres per minute.
• A typical domestic garden hose delivers well under 1 imp-gal/s; a rate of 1 imp-gal/s (≈16,366 L/h) is closer to a small industrial or firefighting pump.
• 1 imp-gal/s ≈ 1.20095 US gallons per second, reflecting the larger Imperial gallon.
• 1 imp-gal/s ≈ 0.00454609 cubic metres per second, useful when comparing against SI pump specifications.