## Re: flow rate unit

Posted by Richard O'Leary (82.34.69.28) on 23:23:42 28/03/05

In Reply to: Re: flow rate unit posted by Gordon England

WHAT IS MASS? WHAT IS ln OR mln?
Imagine you have a cylinder of 1 litre, which is closed by means of a moveable piston of egligible weight.
This cylinder contains 1 litre of air at ambient pressure, approx. 1 bar. The weight of this volume of air at 0 °C is 1.293 g, this is the mass. When we move the piston half way to the bottom of the cylinder, then the contained volume of air is only 1⁄2 litre, the pressure is approx. 2 bar, but the mass is unchanged, 1.293 g; nothing has been added, or left out.

Following this example, mass flow should actually be expressed in units of weight such as g/h, mg/s, etc.
Most users, however, think and work in units of volume. No problem, provided conditions are agreed upon, under which the mass is converted to volume.
A temperature of 0 °C and a pressure of 1,013 bar are selected, and these reference conditions are indicated by the underlying letter 'n' in the unit of volume used.
The direct thermal mass flow measurement method is always based on these reference conditions unless otherwise requested. There are cases, for instance, where the reference conditions are based on 20 °C instead of 0 °C. If this difference is not considered, then there is an error of 7%!

It is worth noting that there is commonly a reversal between EUROPE & USA for the meanings of 's' (standard) and 'n' (normal).

Europe: 'n' = Volume at 0 (zero) Degrees Celsius and 1013.25 mBar
Europe 's' = Volume at 20 (twenty) Degrees Celsius and 1013.25 mBarp

There is a very useful (and free to use) online tool with which conversions between different reference conditions can be calculated.p
It is called FLUIDAT.

Surface Engineering Forum

Surface Engineering Message Board Archive

Surface Engineering Message Board Archive Index

Search Message Boards Archives

www.gordonengland.co.uk

Custom Search

### Post A Message!

Please go to the new Surface Engineering Forum as this old message board is a read only archive. Please copy and paste relevant information or link to the page if you wish to reactivate a thread on the new forum.

Telephone: +44 (0)1252 405186

Thermal Spray Processes:

Combustion Wire Thermal Spray Process

Combustion Powder Thermal Spray Process

Arc Wire Thermal Spray Process

Plasma Thermal Spray Process

HVOF Thermal Spray Process

Detonation Thermal Spray Process

Plasma Flame Theory

Cold Spray Coating Process

Wear and Use of Thermal Spray Coatings

Corrosion and Use of Thermal Spray Coatings

Glossary of Thermal Spray and Surface Engineering Terms

Image Directory for Thermal Spray Coatings

Plasma Gas Flow Information

Plasma Gas Flow Correction Calculator

Contact Form

Links to other interesting sites related to thermal spray and surface engineering

Periodic Table of the Elements

SI Units

Calculators for Conversion between Units of Measurement

Hardness Testing

Surface Engineering Message Board Archive

Surface Engineering Message Board Archive Index

Search This Site

Photography Gallery2

Photography Gallery3