The Waxing/Viscosity Bottom Line
The Shadow
I'd tend to agree:
Microcrystalline wax:
is a petroleum based wax that has very different physical properties to paraffin wax. Micro wax is more dense (weighs more), has a different molecular structure (closer packed molecules), is thicker when liquid (higher viscosity), is more flexible (bends easier), has more adhesion factors (is sticky), tougher (scuff resistant), and has a higher melt point than paraffin wax.
Viscosity:
the Ability of wax to resist flow. The viscosity of wax is represented by a number that defines how a particular wax will flow at a certain temperature. The temperature and the viscosity of wax have opposing relationships. The higher the temperature, the lower the viscosity, and the lower the temperature, the higher the viscosity. This means that a hot wax has a low viscosity and will flow much better than a cold wax with a high viscosity.
It's also noteworthy that waxes have a differentiation between their congealing and freezing points and can be "precipitated out" of fuel. A jet fuel's "pour point" is taken to be 4 to 20 degrees below its freeze point. Fuel will not flow at all when it's below its pour-point. However, in contrast to "pourability", once the physical characteristics of a pumped fuel changes towards a higher viscosity, the pumpability of a particular system will very much depend upon whether the fuel is being pushed or pulled (i.e. sucked or blown).
Cavitation damage to pumps and a failure to throughput a programmed volume will be a logical consequence of a much higher viscosity (than allowed for in the system's design flows). Fuel is used as an hydraulic fluid in HP fuel system servo valves and the proper function of these servo-systems is dependent upon the fuel remaining in a design viscosity range.
The rate at which fuel temps decline (and the temp to which it will drop) is a function of:
a. airplane geometry
b. total (TAT) and ambient air temps
c. fuel management
d. exposure time
e. the fuel's initial temperature
(tinyurl.com/6jxpfn)
There's no guarantee that a fuel load will remain anywhere near a uniform temperature throughout its tankage.