Why polished surfaces are colder?

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Discussion Overview

The discussion centers around the perception of temperature differences between polished and rough concrete floors, specifically why a polished floor feels colder than a rough one, despite being made of the same material.

Discussion Character

  • Conceptual clarification
  • Exploratory

Main Points Raised

  • One participant suggests that the polished floor may have higher heat conductivity, leading to quicker heat loss from the feet.
  • Another participant challenges this idea by considering the contact surface area between the feet and the floor, questioning which surface has a larger contact area and how that affects heat flow.
  • A further explanation is provided regarding thermal contact, noting that smooth surfaces allow for better heat conduction due to closer contact, while rough surfaces only make contact at high points, reducing heat transfer.
  • It is mentioned that pressing harder on a rough surface increases contact but does not change the initial thermal contact situation of smooth surfaces.
  • The role of water in enhancing thermal contact by filling air gaps is also introduced as a factor in heat conduction.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms at play, with some focusing on thermal conductivity and others on contact surface area. The discussion remains unresolved with multiple competing explanations presented.

Contextual Notes

Participants do not reach a consensus on the primary reason for the temperature perception difference, and assumptions regarding heat conductivity and contact area are not fully explored or agreed upon.

Anagnorisis
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Why of two floors made of the same material, the polished one is (at least feels) colder than the rough one.

Just compare two concrete floors, one polished and one unpolished.

Thanks
 
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I would think its just that it feels colder because maybe the polished one has higher heat conductivity, so your feet loses heat more quickly. Thats just my thought.
 
My bet is Sakha is close, but not there yet. Think about contact surface between your feet and the surface. When is it larger - for the polished, or rough surface? How does the heat flow depend on the contact surface?
 
Anagnorisis said:
Why of two floors made of the same material, the polished one is (at least feels) colder than the rough one.

Just compare two concrete floors, one polished and one unpolished.

Thanks

It is due to an effect called thermal contact.

Imagine that you were looking at the interface, the surface between your skin and the floor, with a microscope.
The smooth surfaces would be in close contact and heat would conduct across easily. If the floor were warm it would feel warm, and cold if it were colder than your skin.
But a rough surface would make contact only in spots where the high points met your skin. Very little heat would pass in either direction because it would have to jump the air gap between the high points.
If you pressed harder, it would make no difference when smooth surfaces were in already in good thermal contact, but it would make the rough floor feel colder because some of the high points would be squashed down, increasing the amount of contact between the surfaces.
Or you could spill a little water under your feet to fill the air-gap. Water conducts heat better than the air, and gives a better thermal contact.
 
Thanks. That makes sense.
 

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