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lamimartin

DIY block heater for 450 CDI 2005

33 posts in this topic

I could not afford an iPad. My oldest son has my computer at his house to purge it of diseases (virus season you know). That is why I had to borrow one of my younger son's devices...I wish I had one though. :huh:

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Thanks for making my point guys. If ambient temperature is -30, and your local wind chill is a nominal -40, you're still only dealing with a -30 degree engine.Carl

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Windchill is relevant anytime the temperature of the object is over ambient temperature. The windchill factor varies with how much warmer the object is, the listed listed in weather reports is for a typical human body, for an object just barely over ambient the windchill factor is much smaller.

All to do with carrying heat away, blowing on hot coffee temporarily increases the windchill.

Evaporative cooling is different (the soaking wet factor).

And being in a garage even unheated will make a big difference, a small heater will be much more effective than if parked in the wind.

"Wind chill" -- the actual term -- is only relevant to human skin, causing a "felt" temperature. AccuWeather.com uses a modification of the North American standard formula, which results in what they call a "Real Feel" temperature, but again, just like the National Weather Service and Environment Canada's official wind chill index, it is only relevant to human skin. So while the wind can accelerate cooling of an inanimate object, it can NOT cause an inanimate object's temperature to drop lower than ambient. It also doesn't affect the air temperature in adjacent areas; if the wind doesn't directly reach a surface, there will be no accelerated cooling of that surface. The smart's engine is relatively well shielded from the wind from almost every direction; unless you remove the rear panels and point the back of the car into the wind, there won't be any accelerated cooling of the engine caused by the wind.

It's fairly common to confuse accelerated cooling with wind chill, but they are not interchangeable. And neither has any real effect on the temperature of a parked fortwo's engine.

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The human body loses heat largely by evaporation and convection.[1][2] The rate of heat loss by a surface depends on the wind speed above that surface: the faster the wind speed, the more readily the surface cools. For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity.

And

The first wind chill formulae and tables were developed by Paul Allman Siple and Charles Passel working in the Antarctic before the Second World War, and were made available by the National Weather Service by the 1970s. It was based on the cooling rate of a small plastic bottle as its contents turned to ice while suspended in the wind on the expedition hut roof, at the same level as the anemometer. The so-called Windchill Index provided a pretty good indication of the severity of the weather.

From Wikipedia.

The wind chill INDEX or FACTOR as used by weather forecasters has evolved from that, but wind chill itself is a well accepted alternate for accelerated cooling. Accelerated cooling refers more to liquids as a means of cooling the object, at least according to google search results. Windchill is a subset of the broader term accelerated cooling. Wind chill (or windchill, both are in common usage) is the correct term to discuss accelerated cooling by the effects of natural wind.

And since the pan heaters in this discussion are mounted on the pan at the bottom of the engine wind chill is very much a factor.

Sorry to be a bit pedantic, but it is the, or at least a correct term, and it will affect the warming of an engine prior to starting by means of a heater of any sort. Not the temperature it cools to, of course. That's ambient. We're not talking about the temperature before you plug it in.

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Well, we'll have to agree to disagree on the semantics, because according to the very page you quoted, neither the NWS nor Environment Canada agree with you. The accurate use of the term is specifically an apparent, or "felt" (or "equivalent") temperature that is below the ambient temperature. Because an inanimate object cannot "feel" this equivalent temperature, it is incorrect to state that an engine will cool faster at an announced "wind chill factor." In other words, you can state that the wind will have an effect on cooling a surface (or slowing its heating), but it has nothing to do with the wind chill factor (or index). Another common mistake is assigning a unit (or a degree sign) to the index. That said, the surface has to face said wind directly in order to experience accelerated cooling. "The exposure to wind depends on the surroundings and wind speeds can vary widely depending on exposure and obstructions to wind flow."

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What's to disagree?

I already said "The wind chill INDEX or FACTOR as used by weather forecasters has evolved from that, but wind chill itself is a well accepted alternate for accelerated cooling."

Plain old wind chill is a well accepted term in common usage, with a different meaning altogether, and does well apply to cooling or warming rates of inanimate objects.

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Back here in the real world, Lillian just left for downtown. Still air temperature of -24.8 according to the home weather station, wind chill temperature of -32 calculated by the same instrument. Pepper started with a couple of cycles of the glow plugs. Wind chill could have been anything. Pick a number. -40? Its irrelevant. As far as the car is concerned the temp is still -24.8.Carl

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