Is it cooler hanging ice packs from a fishnet bag or in a thermal lunch-bag?

[DynV]

Summary: I think I found the solution at the end of the post, posting in case someone has a better idea.

I plan on going shopping somewhere a bit distant because my local supermarkets dropped the majority of store brands. I suspect the whole trip will take 90-120 mins. I have a deep freezer, ice packs, multiple thermal bags (I keep forgetting to bring some and buy new ones), thermal lunch-bags and a fishnet bag.

I'm wondering which would keep the ice packs cooler, either

1. leaving them in lunch-bags overnight then leaving them at the bottom of the thermal bags, or
2. rigging the fishnet bag so they stay mid-air in the thermal bags?

Thank you kindly for your help

I was reviewing my post and I think I found the solution: I could hang the lunch-bags so the majority of the time they wouldn't touch the thermal bags.

 

[Arjan82]

So, I presume you want to hang the bags to prevent conductive cooling. But do mind that hanging them will allow for a convective air stream to develop. So I'm not sure it makes that much of a difference.

I also presume you think that thermal bags are better at dealing with radiative cooling than with conductive cooling, which could be true, I don't know. But better still may be to grab some blanket, wrap the ice packs in them and snug those in the thermal bags (blankets not only keep warm things warm, but also cool things cool ). This way you have less conductive heating and don't allow for a convective current to start.

 

[DynV]

hang the bags to prevent conductive cooling

indeed

I'm not too sure what convective current is, but it sounds like cold vanishing in the air, which as soon as I open the bags to put food it, warmer air will rush into expel it. I'm fine with a blanket, I can put it in a bag and beside the size it's light.

 

[Arjan82]

I'm not too sure what convective current is, but it sounds like cold vanishing in the air, which as soon as I open the bags to put food it, warmer air will rush into expel it.

Not exactly. The phenomenon is called 'natural convection'. Even with the bags closed an air current establishes that carries heat from the ice pack to the walls. Air near the ice pack cools off, so the density increases and this air sinks. This air needs to be replaced by the warmer air above. The cold air heats up again when moving along the sides of the bag and therefore rises again (density decreases). So air is continuously carrying away cold from the ice pack to the sides of the bag.