Lowering Freeze Point in Black & Gray Tanks

[rockfordroo]

Originally Posted by emeth

I am much encouraged, so, the only thing that wind-chill would adversely affect our winter stay, is the higher usage of propane.

Here's average and record temps for Ellensburg:

https://en.wikipedia.org/wiki/Ellensburg,_Washington

Looks like average is in the teens, but record lows in the -20's to -30's. So you might want/need to be prepared.

Also, here's a windchill chart, because you'll be out in the weather at some point:

NWS Windchill Information and Chart

[Jmkjr72]

Originally Posted by rockfordroo

That will be true for a pan of water, which evaporates. It won't be true for a pipe (or tank) filled with water that can't evaporate. Evaporation is what causes wind chill.

Why do concrete truck drivers leave there hot water run in the winter when driving down the road(you do know they heat there water to about 200 Deg in the winter right)

How come the pipes that sit extend from the cab of the drill rig i used to run Would freeze even though the tank was heated when driving down the road even with the pipes wrapped with heat tape and pipe wrap. It couldn't have been anything to do with the fact that they were exposed to 70 mph winds when driving down the highway

[rockfordroo]

Originally Posted by Jmkjr72

Why do concrete truck drivers leave there hot water run in the winter when driving down the road(you do know they heat there water to about 200 Deg in the winter right)

How come the pipes that sit extend from the cab of the drill rig i used to run Would freeze even though the tank was heated when driving down the road even with the pipes wrapped with heat tape and pipe wrap. It couldn't have been anything to do with the fact that they were exposed to 70 mph winds when driving down the highway

Your correct - basically a radiator. I got a bit carried away by "wind chill." Wind chill can remove heat faster, but can't make it "colder." So while wind chill may make YOU feel colder than the actual temperature, it won't make the pipe any colder.

My bad.

[emeth]

Originally Posted by Jmkjr72

Why do concrete truck drivers leave there hot water run in the winter when driving down the road(you do know they heat there water to about 200 Deg in the winter right)

How come the pipes that sit extend from the cab of the drill rig i used to run Would freeze even though the tank was heated when driving down the road even with the pipes wrapped with heat tape and pipe wrap. It couldn't have been anything to do with the fact that they were exposed to 70 mph winds when driving down the highway

So, just what physics are at work here and how can we adapt this knowledge for the average RV'r that is about to go through this winter?

Can we safely say that, 'wind-chill' can have an effect on winterized, (heat tape and tank heaters)?

Perhaps a better type of heat tape, enclosing the H2O standpipe or salt in the black and gray tanks?

[rockfordroo]

I guess I'll try it one more time (Jmkjr72 keep me honest).

Wind chill is considered to be the "effect" of wind on human flesh, caused by evaporation, which removes heat. So at a given real temperature, increasing the wind increases the evaporation rate and therefore makes human flesh feel like it's colder, or what I should say, the wind causes the same effect on that flesh as a colder temperature without the wind. So wind chill is a "feeling" related to human flesh. The flesh temperature isn't really at the wind chill temperature; it just "thinks" it is.

With respect to stuff not human (i.e., campers), anything where the outside temperature is colder than the thing we care about (say a water tank) will lose heat (BTU's/hr) at some rate. With no wind, it's (essentially) by conduction from the tank wall to the air around it. If that heat loss is made up for by something, say a tank heater, the water won't freeze. But if not, then it will freeze, at some point. Now putting wind past the tank changes the heat transfer from conduction to convection, which is more efficient than conduction in this case. So this will increase the heat loss rate; this is why the radiator on your car works better when the car is moving.

Insulation simply slows down the rate of heat loss. If you have enough insulation, it will slow the heat loss rate down below whatever heat addition rate the component might have. In case of a tank, heat inputs come from warmer water added to the tank, and any warm air that may be blown around the tank by, say your furnace, and possibly heat conduction from the floor of your trailer to the top of the tank. If you have a tank heater, that will also do it. So insulating the tank can keep it from freezing for normal night time temperature dips, but may not be adequate for long-term low temperatures. [If you take an insulated cooler, put a bottle of soda in it, and take it outside below freezing and leave there for a day or so, you will find the soda bottle frozen, because even though it's insulated, there's no source of internal heat to offset the external heat loss.]

Now, if you have a situation where evaporation is also taking place, the act of evaporating removes even MORE heat than if there's no wind. So an open tank will freeze somewhat faster than an closed one in the same wind conditions. But since we don't really have open systems like that, it's sort of a moot point for campers. This is what I had been trying to say in Post #18, but did a lousy job.

OK folks, let me have it!

[emeth]

Originally Posted by rockfordroo

I guess I'll try it one more time (Jmkjr72 keep me honest). OK folks, let me have it!

Let me relate a story when I was a bit younger.

Ice fishing on Lake Champlain; ambient temp was -25 F. wind-chill brought the temp down, on the lake to -60 F. The ice we augured through was 3' thick.

By the time we got the shanty over the hole, the ice was again about 6" thick.

Believe me we used a lot more wood in that shanty wood stove to keep that temp at a comfortable +80 F.

You may be correct, however, I believe that everything works harder when the wind blows.

I believe that anything the RV'er can do,(insulation, heat tape, tank heaters, salt and even fabric softener), will help.

[tomrob1161]

Are you in the RV? If so, your tank heaters and furnace should take care of the cold weather you are talking about. As said in previous post, skirting or bales of hay will help as well.

[bpadamson]

Some folks in cold weather do not leave their freshwater hose hooked up. They fill the freshwater tank and use their onboard pump. One less thing to winterize, just use it, drain it and roll the hose up and put it in a heated area.
Have fun!

[rockfordroo]

Originally Posted by bpadamson

Some folks in cold weather do not leave their freshwater hose hooked up. They fill the freshwater tank and use their onboard pump. One less thing to winterize, just use it, drain it and roll the hose up and put it in a heated area.
Have fun!

Or get a heated one. This one's by Camco:

[B D HOWie]

Or make your own.

Much cheaper and helps protect pressure regulator as you can extend pipe heat tape and insulation to include it.
Obviously this does not do anything to help the black or gray tanks (OP's original question) unless you put the heat tape around them. lol
Paul

[ben31]

Originally Posted by rockfordroo

I guess I'll try it one more time (Jmkjr72 keep me honest).

Wind chill is considered to be the "effect" of wind on human flesh, caused by evaporation, which removes heat. So at a given real temperature, increasing the wind increases the evaporation rate and therefore makes human flesh feel like it's colder, or what I should say, the wind causes the same effect on that flesh as a colder temperature without the wind. So wind chill is a "feeling" related to human flesh. The flesh temperature isn't really at the wind chill temperature; it just "thinks" it is.

With respect to stuff not human (i.e., campers), anything where the outside temperature is colder than the thing we care about (say a water tank) will lose heat (BTU's/hr) at some rate. With no wind, it's (essentially) by conduction from the tank wall to the air around it. If that heat loss is made up for by something, say a tank heater, the water won't freeze. But if not, then it will freeze, at some point. Now putting wind past the tank changes the heat transfer from conduction to convection, which is more efficient than conduction in this case. So this will increase the heat loss rate; this is why the radiator on your car works better when the car is moving.

Insulation simply slows down the rate of heat loss. If you have enough insulation, it will slow the heat loss rate down below whatever heat addition rate the component might have. In case of a tank, heat inputs come from warmer water added to the tank, and any warm air that may be blown around the tank by, say your furnace, and possibly heat conduction from the floor of your trailer to the top of the tank. If you have a tank heater, that will also do it. So insulating the tank can keep it from freezing for normal night time temperature dips, but may not be adequate for long-term low temperatures. [If you take an insulated cooler, put a bottle of soda in it, and take it outside below freezing and leave there for a day or so, you will find the soda bottle frozen, because even though it's insulated, there's no source of internal heat to offset the external heat loss.]

Now, if you have a situation where evaporation is also taking place, the act of evaporating removes even MORE heat than if there's no wind. So an open tank will freeze somewhat faster than an closed one in the same wind conditions. But since we don't really have open systems like that, it's sort of a moot point for campers. This is what I had been trying to say in Post #18, but did a lousy job.

OK folks, let me have it!

You are completely correct. Science!

[TheWolfPaq82]

Originally Posted by Jmkjr72

Why do concrete truck drivers leave there hot water run in the winter when driving down the road(you do know they heat there water to about 200 Deg in the winter right)

How come the pipes that sit extend from the cab of the drill rig i used to run Would freeze even though the tank was heated when driving down the road even with the pipes wrapped with heat tape and pipe wrap. It couldn't have been anything to do with the fact that they were exposed to 70 mph winds when driving down the highway

Geotech for years, never had a rig with heated tanks or tape wrapped pipes.

[Jmkjr72]

Originally Posted by TheWolfPaq82

Geotech for years, never had a rig with heated tanks or tape wrapped pipes.

So was I I built the system myself got sick of dealing with frozen water tankn I thing like a tank full of 180 deg water in the winter for mud rotary