fin/wing tanks freezing

The fix was to put a pint of RV antifreeze in the tail tank. RV antifreeze is propylene glycol and is safe even if you drink a little.

DLB


Dale, My significant other suggested I use White Zin. I countered with Gewurztraminer. Since it is not fit for human consumption, there is no conflict in pulling the dump actuator ;-)

Craig R.

"Craig R." wrote:
The fix was to put a pint of RV antifreeze in the tail tank. RV
antifreeze is propylene glycol and is safe even if you drink a little.

DLB


Dale, My significant other suggested I use White Zin. I countered with
Gewurztraminer. Since it is not fit for human consumption, there is no
conflict in pulling the dump actuator ;-)

Craig R.

Just watch which vintage of wine you're using. In the late 80s there was a
major scandal with various producers of Spättlese spiking the wine with
ethylene glycol. ;-)

Pete

Not having studied thermal dynamics, etc, I have two rookie questions. How does the container material (thin plastic "milk jug" in freezer vs layered fiberglass for tail tank) and the shape of the container (minimal surface area of a milk jug vs long thin tail) effect these calculations? ... also, head space in jug is zip and in tail tank is large....

On Saturday, June 8, 2013 8:04:15 PM UTC-7, Craig R. wrote:
Not having studied thermal dynamics, etc, I have two rookie questions. How does the container material (thin plastic "milk jug" in freezer vs layered fiberglass for tail tank) and the shape of the container (minimal surface area of a milk jug vs long thin tail) effect these calculations? ... also, head space in jug is zip and in tail tank is large....

Having not studied thermodynamics you have saved yourself from a lifetime of boredom (even it if was only an hour a week). To a good approximation, the shape is accounted for in the surface to volume estimate, and the head space is not consequential to heat exchange.

On Saturday, June 8, 2013 8:23:00 PM UTC-7, jfitch wrote:
On Saturday, June 8, 2013 8:04:15 PM UTC-7, Craig R. wrote:

Not having studied thermal dynamics, etc, I have two rookie questions. How does the container material (thin plastic "milk jug" in freezer vs layered fiberglass for tail tank) and the shape of the container (minimal surface area of a milk jug vs long thin tail) effect these calculations? ... also, head space in jug is zip and in tail tank is large....



Having not studied thermodynamics you have saved yourself from a lifetime of boredom (even it if was only an hour a week). To a good approximation, the shape is accounted for in the surface to volume estimate, and the head space is not consequential to heat exchange.

I looked up the effect of various materials on heat transfer and it would appear that 1/4" of foam-composite sandwich roughly halves the heat transmission, extending the time to freeze by roughly double.

The starting temperature of the water doesn't matter that much in the end result (if the end result you are looking for is a solid block of ice). The enthalpy of fusion (turning 32-degree water into 32-degree ice) represents 75-90 percent of the heat transfer versus 10-25 percent to take the water from its starting temperature to 32 degrees.

Again, you would have to be on one of those 16-hour, 25,000 foot Sierra wave flights to worry about frozen-solid ballast tanks - even then I remain a bit skeptical that you'd have a problem. The main risk on a typical summer thermal flight in the 16-18,000' range is from leaking water freezing up on a valve or hinge that you care about. People who have experienced this seem to report pretty consistently that you can break free most of the time. I probably would avoid dumping ballast in freezing conditions if possible.

9B

On Saturday, June 8, 2013 8:50:02 PM UTC-7, wrote:
On Saturday, June 8, 2013 8:23:00 PM UTC-7, jfitch wrote:

On Saturday, June 8, 2013 8:04:15 PM UTC-7, Craig R. wrote:



Not having studied thermal dynamics, etc, I have two rookie questions.. How does the container material (thin plastic "milk jug" in freezer vs layered fiberglass for tail tank) and the shape of the container (minimal surface area of a milk jug vs long thin tail) effect these calculations? ... also, head space in jug is zip and in tail tank is large....







Having not studied thermodynamics you have saved yourself from a lifetime of boredom (even it if was only an hour a week). To a good approximation, the shape is accounted for in the surface to volume estimate, and the head space is not consequential to heat exchange.



I looked up the effect of various materials on heat transfer and it would appear that 1/4" of foam-composite sandwich roughly halves the heat transmission, extending the time to freeze by roughly double.



The starting temperature of the water doesn't matter that much in the end result (if the end result you are looking for is a solid block of ice). The enthalpy of fusion (turning 32-degree water into 32-degree ice) represents 75-90 percent of the heat transfer versus 10-25 percent to take the water from its starting temperature to 32 degrees.



Again, you would have to be on one of those 16-hour, 25,000 foot Sierra wave flights to worry about frozen-solid ballast tanks - even then I remain a bit skeptical that you'd have a problem. The main risk on a typical summer thermal flight in the 16-18,000' range is from leaking water freezing up on a valve or hinge that you care about. People who have experienced this seem to report pretty consistently that you can break free most of the time. I probably would avoid dumping ballast in freezing conditions if possible.



9B

Okay - I put a 2 liter bottle of fresh tap water in my 0-degree freezer with an electronic temperature probe in it. Started at 64 degrees F. Within 1:45 it was at 32 degrees F but totally liquid. After 2:30 it had a thin layer of ice around the inside maybe 1/32" thick that you could easily crack. At around 4:30 it had big chunks of ice in it and the bottle was looking a bit taught, but overall it was still pretty slushy. It's now 6:30 and there is still liquid water in the bottle, the temperature is still 32 degrees F but it's mostly ice. As it froze the freezer came up from 0 degrees to 2 degrees F presumably because of the heat transfer from the state change to solid ice.

I'd say the math works pretty well. If I can find a sleeve of foam core I'll try it again.

9B

How about testing the counter-intuitive experimental finding that warm water freezes quicker than cold (the suggestion is convection currents increase heat transfer).

Mike