Anonymous
Anonymous asked in Science & MathematicsPhysics · 2 months ago

# Since the normal human body temperature is 37C(98.6F), why do human start to feel hot when the air temperature is only 30C(86F)?

Also

Why does the water temperature of the shower need to be as high as like 42C(108F), or else it will make the human body feel cold??

30C(86F) air temperature makes human body feel hot

but 30C(86F) water temperature for the shower or the pool makes human body feel cold

how to explain this

Relevance
• Steven
Lv 7
2 months ago

Your body generates waste heat all the time so your environment has to be cooler for the heat to be dissipated. At 30C, depending on your clothing, the temperature differential is too small to prevent you overheating. If you were completely insulated, your own heat would kill you. Water conducts heat much better than air and if you were completely submerged in 42C water, you would soon overheat. Even hot tubs do not completely cover your body. Large animals overheat easily. Elephant ears are used to keep them cool. Whales require the water to keep them cool.

https://en.wikipedia.org/wiki/Thermoregulation_in_...

• 2 months ago

Thermal comfort is a result of temperature and % Relative Humidity. If the temperature is 86 degrees and the RH is less than ~40% one will feel cool.

In a Shower, water carries heat away from the body and will feel cool/cold if it is less than ~ 106 degrees F.

• D g
Lv 7
2 months ago

98.6 degs is internal temperature

it is like a light bulb .. at the center of a box  ..

as you move farther from  the bulb the heat gets cooler

larger the surface the faster the heat loss

so when you are in the shower  the water  evaporates from your  whole body surface cooling it down

• Dixon
Lv 7
2 months ago

It's basically because air is a moderately good insulator which means it doesn't draw heat away from the skin as quickly as say, a metal or indeed water.

Consider picking up a metal block, a polystyrene block a wood block or putting your hand in water that has been resting and is at room temperature, all versus just your hand in air. The point to note is that all these things are at room temperature but feel different degrees of cold to you because you are warmer than all of them but you transfer heat to them at different rates depending on their physical properties.

Then when you consider flowing air or water this changes the rate at which heat is transferred because there isn't a static local region that is accomodating to the skin temperature - consider the heat loss when riding on a motorbike compared to stationary in medium air temperature.

Showers are complex because the water itself looses heat to the air and it is flowing over our bodies. Also at any one moment, much of our body is just wet and in the ambient air. So even tho shower water may be set to a high temperature, it is not like being fully immersed in water of that temperature.

We are most comfortable when our surroundings are maybe 10 to 15 Celsius cooler than body temperature but not far far cooler.

• 2 months ago

The normal core temperature of the human body is around 37°C, and skin temperature can be a few degrees cooler than that, so when you immerse your body into hotter water or air, heat is transferred to it.

The difference between how hot the water feels compared to the air, at the same temperature, is determined by how this heat is transferred.

"A human body in 38°C air will absorb heat from its surroundings, including the air itself, as well as radiant heat from sunlight, and from other surroundings like nearby buildings," she says.

If we get too hot we sweat.

"Sweating is a very efficient way of cooling because you're giving off water molecules which can take with them huge amounts of energy, especially when they're evaporating into water vapour,"

This is due to water's uniquely high heat capacity. Water molecules are held together with strong hydrogen bonds so water can absorb huge amounts of heat without increasing in temperature very much.

Water in your sweat sucks the heat out of you and cools your skin temperature by several degrees so the air temperature 'feels hot' in comparison.

But when we immerse our bodies in water at 38°C, the difference in temperature between our skin and the environment is smaller.

This is partly because evaporation of sweat is less efficient when you are immersed in water, and you are exposed to less heat from indirect sources such as sunlight.

Hence, water doesn't feel as hot as dry air at the same temperature.