Conversion from Liters per second to Cubic millimeters per minute

Information about the Liter per second (L/s)

The litre per second is a unit of volumetric flow rate equal to one litre passing a point every second. Its symbol is L/s. It is the unit of pumps, drains and ventilation — the scale at which a flow is large enough to be a design problem but small enough to belong to a single building.

A litre per second is a substantial stream. A kitchen tap fully open delivers about a fifth of it, a bath fills at roughly a third, and a fire hose runs at ten to twenty times as much. In visual terms it is a jet about as thick as a thumb moving briskly, and it would fill a domestic bath in about two minutes.

Building services are specified in this unit throughout Europe. Ventilation rates are given as litres per second per person — around eight to ten in an office, more in a room where people cook or exercise — and a designer multiplies that figure by the number of occupants to size the fans and the ductwork. The same unit describes rainwater drainage, where a roof's area and the local rainfall intensity together determine the flow a downpipe must carry.

Pumps are rated the same way. A domestic circulating pump moves a fraction of a litre per second, a borehole pump a few, and a large sewage pump hundreds. Because the power a pump needs is the flow multiplied by the pressure it must overcome, this figure sits at the centre of every pump calculation.

For gases the unit describes compressors and blowers, though there the volume depends on pressure and temperature and so must be stated at defined conditions. A compressor rated at fifty litres per second of free air is measured with the air at atmospheric pressure, and the same machine moving compressed air is shifting a far smaller volume.

A litre per second is a thousandth of a cubic metre per second, which is why hydrologists and building engineers rarely use the same unit even when they are describing the same water. A river carrying a cubic metre per second is carrying a thousand litres per second, and both figures are correct.

One litre per second equals 1,000 millilitres per second, 60 litres per minute, or about 0.0353 cubic feet per second.

Information about the Cubic millimeter per minute (mm³/min)

The cubic millimetre per minute is a unit of volumetric flow rate equal to one cubic millimetre passing a point every minute. Its symbol is mm³/min. It measures flows so slight that a whole minute yields a volume the size of a coarse grain of salt, and it exists because a great deal of precision engineering happens at exactly that pace.

Electrical-discharge machining is the classic user. A wire eroder cutting hardened tool steel removes 20 to 100 cubic millimetres per minute, and a sinker eroder finishing a mould cavity may remove less than one. The rate is the whole economics of the process: a die that takes eight hours to cut cannot be quoted like one that takes eight minutes, and the removal rate is what separates them.

Grinding and honing are described the same way when the tolerance is tight. A creep-feed grinder roughing a turbine blade root runs at hundreds of cubic millimetres per minute per millimetre of wheel width, but a final spark-out pass approaches zero by design, because the last few micrometres must come off without heating the workpiece.

Adhesive and solder-paste dispensing lives here too. A dot of adhesive on a circuit board is a fraction of a cubic millimetre, and a dispensing valve laying a bead is programmed by rate so the bead stays the same width as the head speeds up and slows down around corners. Underfill, conformal coating and potting are all specified in this unit or its microlitre twin.

Biology and medicine borrow it for slow perfusion. Organ-on-a-chip devices, microdialysis probes and slow-release implants move fluid at single-digit cubic millimetres per minute, and cerebrospinal-fluid production in an adult is about 350 to 500 millilitres a day, which is roughly 250 to 350 cubic millimetres per minute — a useful reminder that the body itself works at this scale.

Sixty cubic millimetres per minute is one cubic millimetre per second, and a million is one litre. Put together, that means a flow of one cubic millimetre per minute would need almost two years to fill a one-litre bottle.

One cubic millimetre per minute equals 0.001 millilitres per minute, about 0.01667 cubic millimetres per second, or one microlitre per minute.