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terjeboe OP t1_j3st09r wrote

Reply to comment by VT_Squire in Will water ice melt faster if allowed to drain, or remain in the meltwater? by terjeboe

However, the water and air may not be at the same temperature, no? Ambient may be say 20C and the melt water will not be much more than 0C.

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VT_Squire t1_j3syxzc wrote

>However, the water and air may not be at the same temperature, no?

That's exactly what I am getting at.

Thermal-conductivity is like a speed-limit, so to speak.

Degree for degree, you'd need roughly 11,000 times as much air exposure as you'd need water to melt both cubes in the same amount of time.

Double the temp of the air, you still need 5,500 times as much air... and so on.

At that point, it's not about what melts ice faster, it's about how much assistance you need to give the air to compensate for the fact that water is better at it.

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BuildANavy t1_j3tneoc wrote

You're making a big assumption that there is a significant heat source transferring heat to the water other than through the air. Otherwise in both cases you still rely on heat transfer from the air, it's just that in one case it has to heat up the water first. In a typical experimental setup this might be from a bowl sat on a countertop at ambient temperature or something, but if the bowl had a very low thermal mass and was supported by very thin members then the draining setup could easily melt the ice quicker.

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dnkushne t1_j3v1px8 wrote

This is not right still. Both the air and water will primarily transfer heat by convection. Thermal conductivity is the measure of heat transfer within the same substance, not between two substances.

Assuming room temperature air (i belive this is the OPs intention) earlier comments are right about how the melt water will remain cold and thus have mich slower heat transfer from the ice to the water, thus slower melt.

Your missing that heat transfer is a function of the delta T (difference in temp between two susbtances) times a resistance value (convection primarily here)

Also belive this is confirmed by ice in cooler during camping. Ice and drinks stay colder if you don't drain the water.

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VT_Squire t1_j3v81lr wrote

I'll put it to you this way by stealing an example straight from stack exchange.

Place a cocktail stick through an ice cube and lay it on top of a glass filled right to the top with (room temperature) water. The submerged half will melt quicker than that on top.

So what if we dial "room temp" down to 33 degrees? Same answer. What if we dial it up to 200 degrees? Same answer.

Air is an AWFUL medium for temperature to transfer. It'll take an hour to cool down a warm beer in the fridge. But it's like maybe 12 minutes submerged in water at the same temp as your fridge.

In a cooler you want the maximum of cold thermal mass but the minimum of heat transfer. THATS why draining a cooler makes the ice melt faster. You're literally allowing the ingress of warm air while actively displacing the cold thermal mass. It's got very little to do with wet vs dry like OP is getting at.

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