watermaking


vargata

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hi guys. i really find this mechanism strange and now that in an other topic tee brewing came up i cant stand to share my  wider thoughts on watermaking:

atm you melt water for a long time and boil it quickly. effects:
you have to melt the snow anyway but after that... you go straight to boil it as it wont take much extra time

turn the melting/boiling times around and make melting happen quickly and boiling takes long time. effects:
you still have to melt the snow anyway but after that... you can choose
a: to waste a long time on boiling
b: take your chance and drink the dirty water
c: use purification tablet if you have as it would take much less time

imo melting time should decreased radically while boiling time should be increased radically, even more than the melting time was decreased.

also should change the way purification tablets work:
you have dirty water on 100% and a tablet, mix them: start to "decay" into clean water on 0%. the same mechanism could be used as meet decaying, instead of decreasing it should increase its cleanliness.

also as in an other topic somebody noted: brewing teas or coffees comes with boiling water so it would be logical that it can be safely done either with clean or dirty water.

any thoughts or opinions please feel free to add :)

thanks

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I am probably wrong but as far as the energy requirements are concerned it looks like the time taken to melt one litre of water (one kilogram) from snow should not be too dissimilar to then raising the temperature to boiling point.

Assume the snow is at -20°C.

The specific heat of ice from -20°C to 0°C is around 2kJ/kg/°C so this warming will take around 40kJ.

To transform the snow at 0°C into water at 0°C will require adding the latent heat of fusion (or melting) which for ice is around 334kJ/kg.

Total energy cost to melt the snow would be 374kJ.

The specific heat of water is around 4.2kJ/kg/°C so boiling the water from 0°C should take 420kJ.

However calculating time requirements looks to be much trickier - at least for snow - as it will depend on things like how effectively heat can be transferred to the snow.

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The main change I'd like to see regarding melting and boiling times is the effect of the heat of the fire. Right now I don't think it makes any difference how hot the fire is, which feels a bit odd.

I once did a stupid with the Riken furnace, where I got the temperature up to 2°C below the required forging temperature before running out of coal. I was left with an 8 hour, very hot fire that I couldn't do much with. I was pretty annoyed, but I spent the time making potable water so as not to make it an entire waste. What occurred to me then was that the snow ought to be melting a hell of a lot quicker in such a heat, as should the water be boiling. But it wasn't noticeably different in terms of time from using a 20°C open campfire.

But I do agree with the general premise of this thread in that water purification tabs feel a bit redundant in the current state of play, because it's so easy and resource-cheap to just boil any non-potable water you've made from snow, thus rarely posing a need to use them.

(or ever ever to risk drinking non-potable water )

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3 minutes ago, cekivi said:

Great ideas. I've often wondered if boiling/melting times would be addressed if and when the new cooking mechanics are added. It does seem odd that a fire hot enough to melt iron still takes 20 minutes to melt 1L of snow :)

It wasn't hot enough to melt iron...

grrrrrrrrrr.

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5 minutes ago, Pillock said:

It wasn't hot enough to melt iron...

grrrrrrrrrr.

Sigh. Would "sufficiently hot to render the metals to be forged malleable enough to be shaped with hand tools" be more appropriate? ;)

Considering that you don't have an anvil, file, bellows, etc. the "forging" we do in the game is so abstracted that it may as well be melting the iron :)

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Just now, cekivi said:

Sigh. Would "sufficiently hot to render the metals to be forged malleable enough to be shaped with hand tools" be more appropriate? ;)

Considering that you don't have an anvil, file, bellows, etc. the "forging" we do in the game is so abstracted that it may as well be melting the iron :)

Sorry, I wasn't being pedantic about the realism (for a change).

I just meant, my fire wasn't hot enough to use the forge... by 2°C

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20 hours ago, mystifeid said:

However calculating time requirements looks to be much trickier - at least for snow - as it will depend on things like how effectively heat can be transferred to the snow.

exactly this makes the huge difference. in the case of loose snow you can literally warm all the snow crystals in the very same moment while in the case of ice or water you can only warm it through the surface. for boiling water you warm only the bottom of the pot and the rest of the water slowly takes it through the circulation but in the meantime radiates a lot of that heat into the environment on the not heated surfaces...

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5 hours ago, vargata said:

exactly this makes the huge difference. in the case of loose snow you can literally warm all the snow crystals in the very same moment while in the case of ice or water you can only warm it through the surface. for boiling water you warm only the bottom of the pot and the rest of the water slowly takes it through the circulation but in the meantime radiates a lot of that heat into the environment on the not heated surfaces...

Actually I think you'll find that as long as a temperature gradient exists, convection in water can be a much more efficient method of heat transfer than conduction (and any radiative heat loss from the water would likely add negligible time to boiling the water). See:

https://www.atmos.washington.edu/~durrand/demos/convection_conduction.htm

And I'm not quite sure how one kilogram of snow would all start to warm at the same time as conduction from the pot would heat the snow at the bottom first.

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12 hours ago, mystifeid said:

Actually I think you'll find that as long as a temperature gradient exists, convection in water can be a much more efficient method of heat transfer than conduction (and any radiative heat loss from the water would likely add negligible time to boiling the water). See:

https://www.atmos.washington.edu/~durrand/demos/convection_conduction.htm

And I'm not quite sure how one kilogram of snow would all start to warm at the same time as conduction from the pot would heat the snow at the bottom first.

because the snow crystals are not forming solid block in lose snow, the hot air and the radiated heat can reach a lot of crystals in the same time. its the same with freezing. put out in the cold a pot of water and watch the paint drying (i mean the water freezing) or spill it and watch it instafreeze. you can find videos about it on youtube. same in space. if you put a solid warm stuff in space on the dark side of a planet it will not freeze insta, actually it will cool down quite slowly but spill some water and watch it instafreeze. its because the surface of tiny drops and crystals added together is incomparably bigger than the surface of the pot. but if you dont believe me, try it in practice. scrape some ice from the fridge (dont take a block of ice, thats not like show) and watch how quick it melts...

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8 hours ago, vargata said:

because the snow crystals are not forming solid block in lose snow, the hot air and the radiated heat can reach a lot of crystals in the same time. its the same with freezing. put out in the cold a pot of water and watch the paint drying (i mean the water freezing) or spill it and watch it instafreeze. you can find videos about it on youtube. same in space. if you put a solid warm stuff in space on the dark side of a planet it will not freeze insta, actually it will cool down quite slowly but spill some water and watch it instafreeze. its because the surface of tiny drops and crystals added together is incomparably bigger than the surface of the pot. but if you dont believe me, try it in practice. scrape some ice from the fridge (dont take a block of ice, thats not like show) and watch how quick it melts...

Since I have the opposite problem with temperature I'm having to learn this as I go along but why does the snow look like it is melting down (and why does the narrator keep repeating this phrase) in this video?

Why does he warn not to add too much snow?

How much warm air and radiant heat is coming from the water in the bottom of the pot?

What is melting the snow that is actually in the water at the bottom?

If warm convective air and radiant heat can efficiently melt a lot of snow all at once, how is it possible to dry boil a pot (and put a hole in it)?

Another video (with a bigger fire) warning not to heat too much snow :


If nine litres of snow have to be added a handful at a time to produce one litre of water, it actually looks like this process is going to take significantly longer than I originally expected.

Anyway, there are a lot of people on this site with a better understanding of thermodynamics than me and who doubtless do this regularly, so I'll leave further discussion of how snow melts in a pot to them.

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There's so many factors at play here it's hard to say definitively which way is best but if I was out and about I'd probably just pack the pot as tight as I could with snow and throw the pot on the fire. What your video guy is referring to is the downside that snow is also a good insulator. So, if your heat source is hot enough you could potentially boil the pot dry before the upper layers have a chance to melt down and fill the bottom. The other downside of melting snow is radiant heat is a far less efficient way to transfer heat than conduction. Once the snow starts melting it would be easier to melt more snow since liquid/solid is better at direct heat transfer than air/solid.

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  • 2 weeks later...
On 24/02/2017 at 11:55 PM, mystifeid said:

I am probably wrong but as far as the energy requirements are concerned it looks like the time taken to melt one litre of water (one kilogram) from snow should not be too dissimilar to then raising the temperature to boiling point.

Assume the snow is at -20°C.

The specific heat of ice from -20°C to 0°C is around 2kJ/kg/°C so this warming will take around 40kJ.

To transform the snow at 0°C into water at 0°C will require adding the latent heat of fusion (or melting) which for ice is around 334kJ/kg.

Total energy cost to melt the snow would be 374kJ.

The specific heat of water is around 4.2kJ/kg/°C so boiling the water from 0°C should take 420kJ.

However calculating time requirements looks to be much trickier - at least for snow - as it will depend on things like how effectively heat can be transferred to the snow.

Awesome work - saved me typing all that out.

I posted on this subject on the Steam community, but this follows-on nicely from the above...

On top of the energy required for heating and phase-change, snow has several properties that make it very heat-resistant...

1) Loft - snow traps air, just like your down-filled jacket or sleeping bag. This air can be warm or cold and it resists temperature changes (hence, if you have hypothermia and access to a fire, you should strip-off to get heat directly to your body, and not have the loft of your clothing resisting heat ingress).

2) It's white - this is going to be reflective of radiated heat as well as light. Snow blindness and reflective sunburn are both testament to this.

3) Structure - water, left of its own devices, is highly subject to gravity. It slops around and generally pools in low places. Snow doesn't - it has structure and can bridge voids easily (dug-out snow shelters or igloos are perfect examples). This allows snow to stay away from the bottom of your pan (where the heat is).

4) Absorbency - snow is like a sponge; it will soak-up liquid from melted snow, wicking it away from the bottom of your pan.

Combine all of these and you have a substance that is resistant to heat ingress, wicking away what you do manage to melt and, due to it's structure, not falling down, leaving an air-void between the pan bottom and the snow you are trying to melt. It's even possible that the wicked-up water will refreeze. The reflective snow is bouncing back the radiated heat from the pan bottom. This not only makes snow difficult to melt, but with thin aluminium camping pans, it is actually possible to melt the bottom of the pan without melting the snow.

If you know what you are doing, it's easy to avoid this, but it illustrates a point.

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It might make the game easier but in real life you can eat snow.

why not add the ability to eat snow for hydration but your temperature will drop dramatically for a short time and you can become ill from eating it. This would be a last resort.

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The mechanic I would like to see is for those buildings actually above freezing you should be able to put a couple of pots of snow out when you go to sleep and by morning its water.  Mind you probably not much water in this region, I don't think this snow has a high water content.  Which means some of that time is the trudging back and forth to collect more snow.

fyi if you're melting snow it goes quicker if you put a bit of water in your pot to start off - also believe or not you can actually scorch snow (or more specifically whatever garbage is in the snow) its vile and the taste lingers - water helps to prevent that.  

You don't want to put too much snow in a pot because then the water goes down the outside of the pot which may or maynot cause problems with your fire but definately wastes water. There's also the insulation factor from packing snow.  In one of the times I had to melt snow, we got too enthusiastic because we were young, cold and idiotic put in too much snow on too weak of a fire.  It was heart breaking really. :D

 

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Stepping back a bit, I notice that many of these ideas would allow survivors to hydrate themselves more easily. I'm curious if these suggestions are more about adding immersion to the game, or addressing a frustration with the current water gathering system?

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On ‎2017‎-‎03‎-‎11 at 4:28 PM, Lovehandel said:

I think getting water is a little too easy. The problem is you get it by staring at a progress bar. 

 

I believe that if you could sew your socks or clean your rifle while the water melted/boiled the process would matter a lot less.

@Mel Guille I think @Lovehandel has a good description of the current failings with the water gathering system :) 

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