Ask HN: Would taking an iced coffee outside make your hand warmer or colder?
3 comments
The ice coffee would freeze.
If your hand is ~90 degrees from body heat, then holding an iced drink will make it colder. The air temperature will also make your hand colder.
If the answer was warmer, where is the energy coming from?
Warmer or colder compared to what? Holding nothing? Holding a liquid also at air temperature? You gotta clarify the scenario more to get a good answer. Also our perception of temperature is terrible, we can only really tell differences and how fast we are loosing or gaining heat.
When you are holding something, you are transferring heat via conduction, which is generally much faster than radiation or convection. You also transfer heat to the nearby air, heating it up. As the air gets closer to your body temperature, you loose less heat, as most heat transference is a function of temperature difference. If something like a jacket keeps the warm air close to your body, then you feel warm. If something like wind moves the warm air away, then you will will feel cold, this is the source of wind chill. But either way, you don't transfer as much heat to air as you would a solid or liquid.
To answer your question, it will probably make you colder because you are going to transfer heat faster to a solid than the air in most cases. Even if its slightly warmer than the ambient air temperature, its much colder than you. There might be an edge case where windchill is extreme enough that shelter from the wind by touching the drink may be warmer. Also the drink itself will stay colder longer than compared to a hot day, as it will also be transferring heat to the air.
This is also related to why being wet and cold is much more dangerous than just cold. Cold water acts as a heat wick that transfers heat out of your body, and then to the air. Unlike your skin, it doesn't have a barrier to the air and will radiate heat to the air faster, also your body will waste energy heating up the water without any benefit.
When you are holding something, you are transferring heat via conduction, which is generally much faster than radiation or convection. You also transfer heat to the nearby air, heating it up. As the air gets closer to your body temperature, you loose less heat, as most heat transference is a function of temperature difference. If something like a jacket keeps the warm air close to your body, then you feel warm. If something like wind moves the warm air away, then you will will feel cold, this is the source of wind chill. But either way, you don't transfer as much heat to air as you would a solid or liquid.
To answer your question, it will probably make you colder because you are going to transfer heat faster to a solid than the air in most cases. Even if its slightly warmer than the ambient air temperature, its much colder than you. There might be an edge case where windchill is extreme enough that shelter from the wind by touching the drink may be warmer. Also the drink itself will stay colder longer than compared to a hot day, as it will also be transferring heat to the air.
This is also related to why being wet and cold is much more dangerous than just cold. Cold water acts as a heat wick that transfers heat out of your body, and then to the air. Unlike your skin, it doesn't have a barrier to the air and will radiate heat to the air faster, also your body will waste energy heating up the water without any benefit.
I mean warmer or colder compared to holding nothing.
Probably colder then. Even though its a warmer temperature than the air, you are going to transfer heat faster by touching a solid than air. Faster heat transference is perceived as cold. Similar to how a stone floor will feel colder than a wood floor of the same temperature, because the stone absorbs heat faster than wood. Remember you aren't feeling how hot or cold something is. You feel your skins temperature right next to it.
Would this make your hand holding the iced coffee cup warmer or colder?