What does Bronkhorst mean by ln/min or ls/min?

A 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. Normal conditions (ln/min): 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. Standard conditions (ls/min): here the reference conditions are based on 20 °C instead of 0 °C. Please be aware of this difference, because mixing up these reference conditions causes an error of 7%!

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I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.