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H4zardousMoose t1_j3srwee wrote

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

I'd definitely be interested in the link because I'd imagine it wholly depends on the container, in which you keep the ice-water mixture. A well insulating container, with a small surface area for the water would probably be worse than having the ice in a sieve over the sink. Where as a wide metal bowl should be better. What matters is how much energy from the surrounding air can be transferred into the ice. Water is a great thermal conductor, so I don't see how it could insulate the ice. If you add energy to a mixture of water and ice it will always melt ice. That's why a mixture of water and ice is always at the melting point (given the energy transfer isn't too fast and there is some agitation).

Anyways that's what I'd expect from the experiments I remember from my physics classes.

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Acceptable_Tower_609 t1_j3t65mi wrote

It will be interesting to find out if the size of the tin bowl is going to be practical. But my bet would be on the free standing ice. Air convection is so much faster than water.

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Ambitious_Jelly8783 t1_j3t2qfn wrote

If you keep the water, all things equal, the water will protect the ice. The melted water will keep at 0*C, protecting the ice, where the air will be warmer, so if no water the air will apply a higher temp to the surface.

Water requires a lot of energy to change degrees. It is actually not a great conductor. Now if you have warm water, same reasonkng applies as it has lots of energy so it'll melt it very quickly.

Someone do the experiment and share it.

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raptir1 t1_j3tugsn wrote

> Water requires a lot of energy to change degrees.

Not compared to the amount of energy it takes to melt ice. Melting ice takes nearly 80 times as much energy as it takes to warm water 1C.

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ubik2 t1_j3t7k8m wrote

At some point, the extra surface area of the water/air interface means more heat is transferred from the ice cube to the air. If the surface area is small, the more important factor is that it slows the transfer from the ice.

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H4zardousMoose t1_j3xyimx wrote

I think you are conflating thermal conductivity (how well thermal energy propagates through a material, measured in W/kg*K) and thermal capacity (how much energy a given amount of a material can hold, usually measured in J/kg*K).

Water has high values in both btw. So it takes a lot of energy to heat up and cool down, but it also exchanges energy quickly within itself and to it's surroundings.

Now instinctively I thought that water would have a higher thermal conductivity than ice, because Iglus insulate so well. But snow isn't ice (crazy I know:D) and it turns out ice has about a 4 times higher thermal conductivity than water at 0°C.

Therefore: If you cover the ice in a thin layer of water, this should slow down the melting. But if you put the ice into a decent sized container with water, where the total surface area of the mixture becomes more than 4x larger than the surface area of the ice it should speed up the melting process. This effect should also increase the further along the melting process you are, since the surface area of the ice will decrease (less of it left), where as the surface area of the mixture remains mostly equal (ice has a bit less density I know, but small effect).

So I learnt something: Solids generally conduct heat better than liquids. But the original point, where it depends on the container and it's conductive surface area still mostly remains valid.

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