In our first Mk VB beta test, the simple coil of 20' of 3/8" stainless tubing in a ice water bath, with 25# of dry ice in the bottom, dropped the tank pressure 100 psi lower than the original Mk V, upgraded to include an identical Gast/Promax recovery system, and which was running along side it.
The current experiment will pass the N2 from a Dewar through a short counter flow heat exchanger for butane injection, so that the butane in the tank can be kept warmer to facilitate faster pumping.
As many of ya'll know, a counter flow heat exchanger has a tube within a tube and usually passes coolant through the outer tube and product through the inner.
Our system also passes that and additional N2 through 50' of 3/8" stainless tubing in a tank of alcohol, which has two more 3/8" heat exchanger coils. One for the diaphragm pump and one for the final recovery pump.
Finally the N2 is routed through a 3/8" coil wrapped around the storage tank, in its ice bath.
Liquid N2 is at 77K/-196C/-320F and releases its heat of vaporization of 5.56 kJ/Mol x -1 when it turns to vapor.[/Q]
Woah, you really went balls to the wall there chilling everything in sight. Wrapping the coil around the tank is an interesting choice. I figured you would be able to conduct more heat away from the tank by submerging it in a dry ice/iso slurry because of surface area exposed....but I guess if its chilled before the run starts you may have something there. I'm a little naive as to your tank pressure goals.