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Post by GTCGreg on Jan 21, 2017 14:11:32 GMT
SD, you are absolutely right that moving air will transfer heat faster than still air. But there is one flaw in your analogy. There has to be heat to transfer. If your CPU was the same temperature as the surrounding air, I don't care how big a fan you would put on the CPU, there would be no additional heat transfer, because there is no heat to transfer. And a car sitting all night with the engine off also has no heat to transfer.
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Post by kharnynb on Jan 21, 2017 16:50:10 GMT
while wind chill cannot make an inanimate object colder than the actual temperature, it can affect operation of for example an engine. this is why we have front grill blockers for when it goes below -20 C here in finland, because it reduces efficiency and causes more wear on the car.
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Post by GTCGreg on Jan 21, 2017 19:27:57 GMT
while wind chill cannot make an inanimate object colder than the actual temperature, it can affect operation of for example an engine. this is why we have front grill blockers for when it goes below -20 C here in finland, because it reduces efficiency and causes more wear on the car. Do your cooling systems not have thermostats?
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Post by the light works on Jan 21, 2017 19:47:16 GMT
while wind chill cannot make an inanimate object colder than the actual temperature, it can affect operation of for example an engine. this is why we have front grill blockers for when it goes below -20 C here in finland, because it reduces efficiency and causes more wear on the car. Do your cooling systems not have thermostats? typically you want the engine to run a bit above the thermostat temperature. its only purpose is to help the car to get above "way too cold to run efficiently" as quickly as possible.
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Post by GTCGreg on Jan 21, 2017 22:36:52 GMT
I want the engine to run at the temperature it was designed to run at. That's usually the temperature that the thermostat is designed to open at. Blocking airflow will only make the engine run hotter than it's supposed to. I don't see any benefit in that.
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Post by kharnynb on Jan 21, 2017 22:40:29 GMT
sealing off the "passive" airflow from the front grill is needed once it gets that cold.
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Post by GTCGreg on Jan 21, 2017 22:45:18 GMT
sealing off the "passive" airflow from the front grill is needed once it gets that cold. It shouldn't be if the thermostat is operating properly. I think that's a carryover from the old days when cars did not have good cooling systems. It gets as cold is -30 F here and I've never had to do that.
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Post by the light works on Jan 21, 2017 23:00:07 GMT
sealing off the "passive" airflow from the front grill is needed once it gets that cold. It shouldn't be if the thermostat is operating properly. I think that's a carryover from the old days when cars did not have good cooling systems. It gets as cold is -30 F here and I've never had to do that. and below 20F, my truck always runs a bit on the cool side.
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Post by GTCGreg on Jan 22, 2017 0:18:55 GMT
It shouldn't be if the thermostat is operating properly. I think that's a carryover from the old days when cars did not have good cooling systems. It gets as cold is -30 F here and I've never had to do that. and below 20F, my truck always runs a bit on the cool side. Sounds like you may have a bad stat then. When I first got my wrangler, the engine temperature would never go above 130º on a cold day. I figured the thermostat was bad and got a new one. When I went to replace it, I found the problem. The old thermostat wasn't seated properly and was allowing coolant to flow around it. After properly installing the new stat, the engine always runs at exactly 210º, summer and winter, which is what the new thermostat is set at.
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Post by the light works on Jan 22, 2017 0:48:38 GMT
and below 20F, my truck always runs a bit on the cool side. Sounds like you may have a bad stat then. When I first got my wrangler, the engine temperature would never go above 130º on a cold day. I figured the thermostat was bad and got a new one. When I went to replace it, I found the problem. The old thermostat wasn't seated properly and was allowing coolant to flow around it. After properly installing the new stat, the engine always runs at exactly 210º, summer and winter, which is what the new thermostat is set at. I have a diesel.
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Post by GTCGreg on Jan 22, 2017 1:28:31 GMT
Sounds like you may have a bad stat then. When I first got my wrangler, the engine temperature would never go above 130º on a cold day. I figured the thermostat was bad and got a new one. When I went to replace it, I found the problem. The old thermostat wasn't seated properly and was allowing coolant to flow around it. After properly installing the new stat, the engine always runs at exactly 210º, summer and winter, which is what the new thermostat is set at. I have a diesel. Diesels just don't produce the heat that a gas engine does. I know that on some diesel ambulances, we have to add auxiliary fuel fired heaters to adequately heat the patient box in cold climates. We just can't get enough heat from the engine.
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Post by the light works on Jan 22, 2017 1:46:32 GMT
Diesels just don't produce the heat that a gas engine does. I know that on some diesel ambulances, we have to add auxiliary fuel fired heaters to adequately heat the patient box in cold climates. We just can't get enough heat from the engine. price of efficiency.
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Post by GTCGreg on Jan 22, 2017 1:55:45 GMT
Diesels just don't produce the heat that a gas engine does. I know that on some diesel ambulances, we have to add auxiliary fuel fired heaters to adequately heat the patient box in cold climates. We just can't get enough heat from the engine. price of efficiency. Any idea what the normal operating temperature is supposed to be?
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Post by the light works on Jan 22, 2017 2:03:27 GMT
Any idea what the normal operating temperature is supposed to be? based on public fora, it appears they tend to average around 190-200, if you are working them hard in warm weather. running easy, it appears they will drop to 180.
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Post by silverdragon on Jan 22, 2017 10:07:40 GMT
SD, you are absolutely right that moving air will transfer heat faster than still air. But there is one flaw in your analogy. There has to be heat to transfer. If your CPU was the same temperature as the surrounding air, I don't care how big a fan you would put on the CPU, there would be no additional heat transfer, because there is no heat to transfer. And a car sitting all night with the engine off also has no heat to transfer. I have a car cooler powered by the Fag-Lighter, its a solid aluminium with fins either side block with a fan on the outside on the top of a normal cool box, yet, it works, to 10degC difference to the outside [of the box] air... Yeah ok, so maybe that takes some time, but having proved it works, it will also keep things cool for longer as well. Therefore, I suggest testing to explain to even me just how the hell that is working of your saying its cant work?.. We also have fans that turn off when not needed these days, to prevent freezing the block of the radiator. There are now cars that can shut the front grille a little at speed [or on the cold] with internal flaps automatically for the same thing. Og yeah, we have them... but all they do is protect the engine block fro over-chill... if you have ever been in artic conditions on an ice road, the extra chill of -20, -30, -40 downwards on an engine can play havoc with radiators, the engine doesnt need to be "that cold", and the ambient temp of the engine bay is enough thanks... But see what I have said above, if the fans dont need to be on, modern cars and trucks will turn them off, but that is dependant on two things, one is a sensor that is on and off, and the other is a electric motor... However I did see one that depended on the viscosity of an oil bath clutch system that as we know changes with heat?.. You have to NOT have a fan belt permanent linkage as well. Having a belt that drives other things is fine, but you have to have and electric fan... my car is electric fan, and it makes a hell of a din if it gets too hot and it goes second-speed... thats typically when I have to reverse down the lane after a long drive.. [..I do that as its only a single lane and I cant turn round on my drive..] Typically engine blocks work warm, cooling systems are water, so getting them above 160degC is super-heated steam time, hence the common problem of overheated engines and radiator caps getting into low earth orbit of you dont open them carefully?.. And also the problem of anti-freeze and "Summer coolant", you need to be watching what it is and the range of the chemicals you use, as typically antifreeze on its own will boil off in the summer if its "that" chemical. But large trucks built to stay cool in American summer, or even Mediterranean summer, the radiator grille is built to handle that, and in winter, its common to close off part of that grille, you keep an eye on the temp gauge and alter how much by stopping and opening or closing off more of the grille. Than on steep hills, you open up fully to breathe.... Think of a trip starting in deep south say Florida where the snow-birds go for winter, and ending up on Alaskan Oil fields, thats a hell of a difference in cooling needs.
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Post by GTCGreg on Jan 22, 2017 14:37:44 GMT
Everything you are talking about in the above post, including your glove box cooler, has a heat source in it. We are talking about an inanimate object with NO HEAT SOURCE. That makes a big difference in this wind chill discussion.
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Post by silverdragon on Jan 23, 2017 8:56:29 GMT
Everything you are talking about in the above post, including your glove box cooler, has a heat source in it. We are talking about an inanimate object with NO HEAT SOURCE. That makes a big difference in this wind chill discussion. So a hot vehicle just been used ..... [This we know...] The ideal of wind chill is that it "feels" colder than the ambient temp because of a cold wind. A vehicle left to stand in a non moving environment, a "still" day, no wind, compared to a vehicle in a -2o to ambient 30mph wind, the discussion I believed was as to which would "freeze up" quicker... The plausibility is that the one in the wind will cool down quicker both inside and out. However, there is also the possibility that the now cold car may have cooled to the temp of the wind, rather than the ambient temp, because of the coolness of the wind cooling it. possible experiments..[some I have already done] It all very well to say stick a thermistor in the wind and measure how cold the wind is, but that is just measuring the wind chill... the wind is moving over the temp sensor. What you have to do is "trap" the wind, say in a barn with two doors one at either end, open for a while to cool to the wind temp, and then once it has stopped moving, measure that now "ambient" temp inside the barn. That alone will tell you when compared to the moving wind speed what the difference between the two is if there be any?.. One of those is similar to something I did in early days of HVAC monitoring when this idea of wind chill was "new" to us, we reduced that to a "postbox" size. We also measured wind speed as well as temp. It was noted that measuring the average wind speed over the last couple of hours could be used to predict the effect of having "wind chill" on the building, so we ceased using that wind "trap" device and just left the outside temp sensor in a shielded from the sun position to collect data for a "degree/day" calculation (average temp for the day) In conclusion, temp sensors suffer sun strike that has the same effect as wind chill in polar opposite temp spikes. Possible science behind that...[simplified so this trucker can understand it as well as others?..] The wind is containing water that is condensing on the surface. [or colliding with that surface..] However, the wind is pushing at that condensing water and forcing it to evaporate. The water has to absorb some temp from "somewhere" to evaporate, so is sucking the heat out of whatever it is attached to.
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Post by GTCGreg on Jan 23, 2017 14:23:50 GMT
The rate of temperature change of warmer objects, water evaporation, wind colder than the ambient temperature, solar heating, yes, all of these these will be affected by wind speed. But this isn't what I would define as "wind chill."
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Post by silverdragon on Jan 24, 2017 7:27:18 GMT
Should the definition of wind chill be any object "cooling" faster in a wind than it would without it?.
That is the test?.
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Post by GTCGreg on Jan 24, 2017 14:32:30 GMT
Should the definition of wind chill be any object "cooling" faster in a wind than it would without it?. That is the test?. No. Wind chill is the effect on an object without a change in temperature. If the actual temperature is changing, that's not wind chill.
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