Composition of Air

COMPOSITION % by volume
N2 Nitrogen 78.03
O2 Oxygen 20.99
A Argon 0.94
CO2 Carbon dioxide 0.03
H2 Hydrogen 0.01
others parts per million
Ne Neon 0.001230
He Helium 0.000400
Kr Krypton 0.000050
Xe Xenon 0.000006

Fourier’s Law


Fourier looked at heat flowing through building  materials, and his experimental results produced ideas such as thermal conductivity, resistance and the thermal transmission co-efficient or u-value. Read the rest of this entry »

Compound Interest


In design work, there is a business side of things that depends on loans and investments.  There is also a business side of things where people invest different amounts for different periods of time in helping you — and you might have to figure out their share of things in the future.

There is also the idea of inflation and cost of living — as you have to design to a cost, a budget, you have to sometimes predict the future costs involved.

This is a small introduction to the basics of compound interest, included here in the hope that it may help. Read the rest of this entry »

Flow Rate Calculations


This is  a technical article on calculations pertaining to volume and mass flow rates of fluids. Read the rest of this entry »

Ventilation Grille Sizing


The aspect ratio is

______   of the grille.

(Total volume flow rate [m3 . s-1]).(100)
______________________________________________= Area (m2)
(No. inlets).( inlet velocity [m . s-1]).( per cent free area)

Fluids Constants


This is a technical reference post that simply lists all the physical constants used in fluid calculations. Read the rest of this entry »