Litres per hour (l/h) to Cubic Millimeters per second (mm³/s) conversion

What is litres per hour?

Litres per hour (L/h) is a common unit for measuring the rate at which a volume of liquid flows. Understanding its meaning and applications can be helpful in various fields.

Understanding Litres per Hour (L/h)

Litres per hour (L/h) is a unit of volume flow rate. It indicates the volume of liquid, measured in litres, that passes a specific point in one hour. In simpler terms, it tells you how many litres of a substance are moving per hour.

Formation of the Unit

The unit is formed by combining two fundamental units:

• Litre (L): A metric unit of volume, defined as the volume of one kilogram of pure water at its maximum density (approximately 4°C).
• Hour (h): A unit of time, equal to 60 minutes or 3600 seconds.

Therefore, 1 L/h means that one litre of a substance flows past a point in one hour.

Formula and Calculation

The flow rate ($Q$) in litres per hour can be calculated using the following formula:

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

Where:

• $Q$ = Flow rate (L/h)
• $V$ = Volume (L)
• $t$ = Time (h)

Real-World Examples

Litres per hour are used in many practical applications.

• Water Usage: A household might use 500 L/h when all taps, showers, and appliances are running at once.
• Medical Infusion: An IV drip might deliver medication at a rate of 0.1 L/h.
• Fuel Consumption: A car might consume 5 L/h of fuel while idling.
• Industrial Processes: A chemical plant might pump reactants at a rate of 2000 L/h into a reactor.
• HVAC System: Condensate from a home air conditioner might drain at a rate of 1 L/h on a humid day.

Interesting Facts and Connections

While there isn't a specific "law" directly associated with litres per hour, the concept of flow rate is central to fluid dynamics, which is governed by laws like the Navier-Stokes equations. These equations describe the motion of viscous fluids and are fundamental in engineering and physics.

Conversion

Often, you might need to convert between L/h and other flow rate units. Here are some common conversions:

• 1 L/h = 0.001 $m^3$/h (cubic meters per hour)
• 1 L/h ≈ 0.264 US gallons per hour

What is Cubic Millimeters per Second?

Cubic millimeters per second ($mm^3/s$) is a unit of volumetric flow rate, indicating the volume of a substance passing through a specific area each second. It's a measure of how much volume flows within a given time frame. This unit is particularly useful when dealing with very small flow rates.

Formation of Cubic Millimeters per Second

The unit $mm^3/s$ is derived from the base units of volume (cubic millimeters) and time (seconds).

• Cubic Millimeter ($mm^3$): A cubic millimeter is a unit of volume, representing a cube with sides that are each one millimeter in length.

• Second (s): The second is the base unit of time in the International System of Units (SI).

Combining these, $mm^3/s$ expresses the volume in cubic millimeters that flows or passes through a point in one second.

Flow Rate Formula

The flow rate ($Q$) can be defined mathematically as:

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

Where:

• $Q$ is the flow rate ($mm^3/s$).
• $V$ is the volume ($mm^3$).
• $t$ is the time (s).

This formula indicates that the flow rate is the volume of fluid passing through a cross-sectional area per unit time.

Applications and Examples

While $mm^3/s$ might seem like a very small unit, it's applicable in several fields:

• Medical Devices: Infusion pumps deliver medication at precisely controlled, often very slow, flow rates. For example, a pump might deliver insulin at a rate of 5 $mm^3/s$.

• Microfluidics: In microfluidic devices, used for lab-on-a-chip applications, reagents flow at very low rates. Reactions can be studied using flow rates of 1 $mm^3/s$.

• 3D Printing: Some high resolution 3D printers using resin operate by very slowly dispensing material. The printer can be said to be pushing out material at 2 $mm^3/s$.

Relevance to Fluid Dynamics

Cubic millimeters per second relates directly to fluid dynamics, particularly in scenarios involving low Reynolds numbers, where flow is laminar and highly controlled. This is essential in applications requiring precision and minimal turbulence. You can learn more about fluid dynamics at Khan Academy's Fluid Mechanics Section.