Does the thermometer calculate wind-chill?

[GIT-R-DONE]

I concur with DLENO. No matter how hard the wind blows, the temperature will stay the same, if it didn't, my thermometer would be doing double duty all the time.

 

[DLeno]

NC_Mog is correct -- in the case of a clear night with no wind, and for exposed surfaces (like a car roof). In this case, black body radiation has a noticable effect in that it is indeed possible for an exposed surface to cool itself to a temperature slightly below that of the surrounding air. But thats only possible for the "no wind" situation, and for surfaces that are unprotected (i. e. radiate into 'nothing'). frost doesn't usually form on engines



I think this temperature difference (between a car body and the air, due to black body radiation) is mitigated by thermal heat transfer in that the air surrounding the car body surface will tend to warm it back up. so there will be some equilibrium acheived between the cooling effect of black body radiation (energy leaving the surface independant of the air) and the warming affect of the air itself (energy being put back into the surface from the air molecules arround it). When there is zero wind (i. e. perfectly still night), such temperature differences are possible and do explain why an exposed surface can be cooler than the air, and why frost can form when the air temp is slightly above freezing. When there is wind, however, the effect of black body radiation is swamped, and the actual temperature difference between the car roof and the surrounding air is very small. Note that the reason frost doesn't form when there is wind is really two fold: (1) the presence of wind lowers the frost point temperature, and (2) the presence of wind swamps out the effect of black body radiation so that surfaces can't really achieve a lower temperature than the air anyway.



so since we're talking about the effect of wind upon a cooling engine and upon the thermometer temp sensor, I don't think black body radiation represents any practical consequence to the accuracy of the truck's temp sensor, or upon in the starting temperature of the engine in the morning .



now then, suppose you park the the truck outside on a clear, still night. Is it possible for the temp sensor or the engine itself to be cooler than the outside air? I don't have any equations in my back pocket but suspect that other nearby objects (i. e. bumper, radiator, the inside of the hood, etc), which are also radiating energy, will tend to aborb and reflect energy radiating from the things of interest, such that it would be highly unlikely, in my opinion, for anything under the hood to actully become cooler than the outside air. ever see frost on the engine block? don't laugh -- that would have to occur if the engine actually did acheive a temperature at or below the frost point -- whether the hood was over it or not. The reason that "protected" things don't attract frost is not because they are shielded from falling frost-- its because they can't acheive the required surface temperature to condense the humidity out of the air.