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If a black plastic part is let under the sun in a tropical area, what temperature could it reach?
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Justin Bowen
If a black plastic part is let under the sun in a tropical area, what temperature could it reach?
On earth the temperature would reach around 100 C but in space with no heat conduction paths, it will get to 150C (like satellites do) because as they get hotter, the object will re-radiate the heat more as it gets hotter. The other answers are good and basically correct but experience is the answer here. If the air is moving or if the object is in a glass box or sitting on a rock or a steel deck of a ship changes the answer a lot. I get burned with a hot seat belt belt buckle on a hot day in the sun and that means it was 90+C. Touch temperature (safe hot) is 50 C.
On earth the temperature would reach around 100 C but in space with no heat conduction paths, it will get to 150C (like satellites do) because as they get hotter, the object will re-radiate the heat more as it gets hotter. The other answers are good and basically correct but experience is the answer here. If the air is moving or if the object is in a glass box or sitting on a rock or a steel deck of a ship changes the answer a lot. I get burned with a hot seat belt belt buckle on a hot day in the sun and that means it was 90+C. Touch temperature (safe hot) is 50 C.
As mentioned, a lot of factors come into play. Where on the earth is a big difference, at the absolute outmost of the equator the radiation from the sun is noticeably higher.
The answer would look somethin like
Temp = {Qradiation + Qconduction (ground) + Qconvection (air)} … The signs of these variables are important, and can change over time.
since you mentioned it was a black body the coefficient for the radiation should be 1 (or as close to one as we want to make it in this thought experiment). Since these power sources aren't necessarily finite (in our terms… Sunlight per day) it would also depend on how long your interested in leaving the plastic, or just the theoretical max, let's assume the sun never goes away.
At a certain point the above equation will balance, the surplus of energy from the sun will be equaled by the energy leaving the plastic because it is much hotter than the surface it rests on and the air that is flowing over it (as mentioned previously, wind speed and humidity could make a huge difference in cooling!)
rough guess, I think an estimate of ~1kw/m^2 is used for quick radiation input from the sun (at hotter areas calcs show 1.37, but since we are simplifying, ballpark of 1kw works… Also since it's a 4th order equation, changing from 1000 to 1370 wont be a huge difference to temperature). Ignoring all other inputs (because we assume the ground and air will be lower temperature than our plastic, if nothing else, they surely will be at max temperature) for simplicity it looks like the max temperature would be ~90C (Qrad=5.6703E-8*Tmax^4)
Remember though that humans are terrible thermometers. A 90C piece of plastic might feel similar to a 65C piece of (more conductive material… Some metal). All we feel is energy change, which in term raises or lowers the temperature of the body part touching the item.
As mentioned, a lot of factors come into play. Where on the earth is a big difference, at the absolute outmost of the equator the radiation from the sun is noticeably higher.
The answer would look somethin like
Temp = {Qradiation + Qconduction (ground) + Qconvection (air)} … The signs of these variables are important, and can change over time.
since you mentioned it was a black body the coefficient for the radiation should be 1 (or as close to one as we want to make it in this thought experiment). Since these power sources aren't necessarily finite (in our terms… Sunlight per day) it would also depend on how long your interested in leaving the plastic, or just the theoretical max, let's assume the sun never goes away.
At a certain point the above equation will balance, the surplus of energy from the sun will be equaled by the energy leaving the plastic because it is much hotter than the surface it rests on and the air that is flowing over it (as mentioned previously, wind speed and humidity could make a huge difference in cooling!)
rough guess, I think an estimate of ~1kw/m^2 is used for quick radiation input from the sun (at hotter areas calcs show 1.37, but since we are simplifying, ballpark of 1kw works… Also since it's a 4th order equation, changing from 1000 to 1370 wont be a huge difference to temperature). Ignoring all other inputs (because we assume the ground and air will be lower temperature than our plastic, if nothing else, they surely will be at max temperature) for simplicity it looks like the max temperature would be ~90C (Qrad=5.6703E-8*Tmax^4)
Remember though that humans are terrible thermometers. A 90C piece of plastic might feel similar to a 65C piece of (more conductive material… Some metal). All we feel is energy change, which in term raises or lowers the temperature of the body part touching the item.
On earth the temperature would reach around 100 C but in space with no heat conduction paths, it will get to 150C (like satellites do) because as they get hotter, the object will re-radiate the heat more as it gets hotter. The other answers are good and basically correct but experience is the answer here. If the air is moving or if the object is in a glass box or sitting on a rock or a steel deck of a ship changes the answer a lot. I get burned with a hot seat belt belt buckle on a hot day in the sun and that means it was 90+C. Touch temperature (safe hot) is 50 C.
On earth the temperature would reach around 100 C but in space with no heat conduction paths, it will get to 150C (like satellites do) because as they get hotter, the object will re-radiate the heat more as it gets hotter. The other answers are good and basically correct but experience is the answer here. If the air is moving or if the object is in a glass box or sitting on a rock or a steel deck of a ship changes the answer a lot. I get burned with a hot seat belt belt buckle on a hot day in the sun and that means it was 90+C. Touch temperature (safe hot) is 50 C.
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As mentioned, a lot of factors come into play. Where on the earth is a big difference, at the absolute outmost of the equator the radiation from the sun is noticeably higher.
The answer would look somethin like
Temp = {Qradiation + Qconduction (ground) + Qconvection (air)} … The signs of these variables are important, and can change over time.
since you mentioned it was a black body the coefficient for the radiation should be 1 (or as close to one as we want to make it in this thought experiment). Since these power sources aren't necessarily finite (in our terms… Sunlight per day) it would also depend on how long your interested in leaving the plastic, or just the theoretical max, let's assume the sun never goes away.
At a certain point the above equation will balance, the surplus of energy from the sun will be equaled by the energy leaving the plastic because it is much hotter than the surface it rests on and the air that is flowing over it (as mentioned previously, wind speed and humidity could make a huge difference in cooling!)
rough guess, I think an estimate of ~1kw/m^2 is used for quick radiation input from the sun (at hotter areas calcs show 1.37, but since we are simplifying, ballpark of 1kw works… Also since it's a 4th order equation, changing from 1000 to 1370 wont be a huge difference to temperature). Ignoring all other inputs (because we assume the ground and air will be lower temperature than our plastic, if nothing else, they surely will be at max temperature) for simplicity it looks like the max temperature would be ~90C (Qrad=5.6703E-8*Tmax^4)
Remember though that humans are terrible thermometers. A 90C piece of plastic might feel similar to a 65C piece of (more conductive material… Some metal). All we feel is energy change, which in term raises or lowers the temperature of the body part touching the item.
As mentioned, a lot of factors come into play. Where on the earth is a big difference, at the absolute outmost of the equator the radiation from the sun is noticeably higher.
The answer would look somethin like
Temp = {Qradiation + Qconduction (ground) + Qconvection (air)} … The signs of these variables are important, and can change over time.
since you mentioned it was a black body the coefficient for the radiation should be 1 (or as close to one as we want to make it in this thought experiment). Since these power sources aren't necessarily finite (in our terms… Sunlight per day) it would also depend on how long your interested in leaving the plastic, or just the theoretical max, let's assume the sun never goes away.
At a certain point the above equation will balance, the surplus of energy from the sun will be equaled by the energy leaving the plastic because it is much hotter than the surface it rests on and the air that is flowing over it (as mentioned previously, wind speed and humidity could make a huge difference in cooling!)
rough guess, I think an estimate of ~1kw/m^2 is used for quick radiation input from the sun (at hotter areas calcs show 1.37, but since we are simplifying, ballpark of 1kw works… Also since it's a 4th order equation, changing from 1000 to 1370 wont be a huge difference to temperature). Ignoring all other inputs (because we assume the ground and air will be lower temperature than our plastic, if nothing else, they surely will be at max temperature) for simplicity it looks like the max temperature would be ~90C (Qrad=5.6703E-8*Tmax^4)
Remember though that humans are terrible thermometers. A 90C piece of plastic might feel similar to a 65C piece of (more conductive material… Some metal). All we feel is energy change, which in term raises or lowers the temperature of the body part touching the item.
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