Conversion from 5 Milliliters per second to Cubic feet per hour

Information about the Milliliter per second (mL/s)

The millilitre per second is a unit of volumetric flow rate equal to one millilitre of fluid passing a point every second. Its symbol is mL/s. Since a millilitre is a cubic centimetre, the unit is identical to the cubic centimetre per second, and the two names are used interchangeably depending on whether the fluid is thought of as a liquid or as a volume of space.

Volumetric flow rate is a volume divided by a time, so it has the dimensions of length cubed per second. That makes it convertible to any other flow unit by a single multiplication, and it also means that a flow rate multiplied by a duration gives the total volume delivered — the arithmetic that underlies every dosing calculation and every water bill.

A millilitre per second is a small but visible flow. A tap dripping steadily produces perhaps a tenth of this; a thin stream from a partly opened tap is a few millilitres per second; a garden hose at full flow is several hundred. In household terms it is the rate at which a teaspoon fills in about five seconds.

The unit belongs to the laboratory and to small machinery. Peristaltic pumps, dosing systems, fuel injectors and analytical instruments all work in this range, and their specifications are written in millilitres per second when the process is fast and in millilitres per minute when it is slow. Where a pump must deliver a precise quantity, the rate and the running time together define the dose.

Human physiology gives useful comparisons. Resting cardiac output is about eighty millilitres per second, urine production averages under a fiftieth of that, and saliva production is around a hundredth. The flow through a single capillary is far smaller still and is measured in cubic millimetres per hour.

Converting to the SI base unit requires care with the powers of ten. One millilitre per second is a millionth of a cubic metre per second, because a millilitre is a millionth of a cubic metre. That factor of a million between the practical unit and the base unit is why flow rates are almost never quoted in cubic metres per second outside hydrology and heavy engineering.

One millilitre per second equals 0.001 litres per second, 60 millilitres per minute, or about 0.0000353 cubic feet per second.

Information about the Cubic foot per hour (ft³/h)

The cubic foot per hour is a unit of volumetric flow rate equal to one cubic foot passing a point every hour. Its symbol is ft³/h, and in the gas trades it is abbreviated CFH. It is the unit of fuel gas supply throughout North America, where every appliance and every pipe is sized by it.

Natural gas is billed and metered in cubic feet, so the hourly rate is what a gas fitter works with. A domestic furnace consumes 80 to 150 cubic feet per hour, a water heater 40, a cooking range 65, and a whole house at design conditions perhaps 250. A residential meter is rated at 250 CFH and the service pipe at rather more.

Pipe sizing tables are built entirely around this unit. Given a length of pipe, a diameter and an allowable pressure drop, the table returns a capacity in cubic feet per hour, and the fitter compares it against the sum of the appliance ratings on that branch. Undersize the pipe and the burners starve when everything runs at once; oversize it and the material cost rises for no benefit.

The unit converts easily into heat. Natural gas carries roughly 1,000 British thermal units per cubic foot, so a rate in cubic feet per hour is very nearly the same number in thousands of British thermal units per hour. An appliance rated 100,000 British thermal units per hour therefore burns about 100 cubic feet per hour, which is why the two figures appear together on every rating plate.

Propane behaves differently and is worth stating separately. It carries about 2,500 British thermal units per cubic foot, so the same appliance needs less than half the volumetric flow, and a pipe sized for natural gas is generously large for propane. Confusing the two is a classic and dangerous error in the trade.

Beyond fuel gas, the unit describes slow air and gas flows in imperial practice: purge lines, instrument air, small blowers and laboratory gas supplies. Sixty cubic feet per hour is one cubic foot per minute, and 35.31 cubic feet per hour is one cubic metre per hour.

One cubic foot per hour equals about 0.02832 cubic metres per hour, about 28.32 litres per hour, or about 0.01667 cubic feet per minute.