Tony D Posted June 9, 2014 Share Posted June 9, 2014 "So are you saying that 85F in the desert is hotter than 85F in New Hampshire?" In fact, if you read what I said, that is EXACTLY what I'm saying! People don't quantify things properly. On several of my cross country trips I was confounded why I experienced problems in SoCal at 75 mph on an 85 degree day, but had no problem in the Midwest doing 100+ mph for two hours on end a cross Iowa in 103F ambients. Looking back at my copilot's logs, my son had an Omega Rotary Thermocouple Switch, and was tasked with taking readings every so often. I had thermocouples plastered all over the car running to his switch and digital display. He dutifully logged them... As I said, the revelation of the thermal layer existing in the first 36" above the Tarmac surface of the roadway was shocking. At 8AM climbing Baker Grade with an Ambient Temperature of 85F, the radiator inlet air temperature was 130-145F. On the return leg, at 4PM on the same stretch of road at 82F, the airflow was closer to 150-155! I experienced temperatures in excess of 160F! Across Iowa, at 2 in the afternoon, doing 100mph, with a 103F ambient, WITH THE A/C ON and the car running 175, the interior 70F, the cooling airflow was only 103F! Extensive reading and consultation revealed the presence of aerosolised water present in the Eastern Midwest severely filters UV Radiation, resulting in less temperature rise off the pavement. I noticed this phenomenon all throughout the Eastern Seaboard, and a cross the Great Plains, and to some extent in parts of Texas. Those temps on the roadway started soaring when the sky turned deep, deep blue and not that pale blue so common in summertime back in Michigan. Yeah, it's 85 out. But it's not ambient that is running through the radiator! It's a superheated layer of air...leading my to wonder if that cooling slot for the radiator should be as high as possible in the front of the car to get the coolest air ducted into the radiator. Like I said, the way I drive, likely you will not encounter it unless you enter an endurance event. I literally ran a tank of gas out of the car one evening leaving St. Louis running 4750rpm in top gear...could go no faster maximum horsepower absorbed by aerodynamic drag. Stopped for gas, and 20 minutes later, was back up going 3500 rpms for another tank of gas. Stopped for gas, and did it again. I learned driving at night, everything runs cooler, even if the ambient doesn't change all that much! Quote Link to comment Share on other sites More sharing options...
ozconnection Posted June 9, 2014 Share Posted June 9, 2014 That's very interesting and thought provoking. Good story Tony. Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 10, 2014 Author Share Posted June 10, 2014 So what you are saying is that in very dry conditions there is more radiant heat absorbed into the air from the tarmac, raising the ambient air temperature. In more humid regions, less of that tarmac heat radiates into the air. This reduces the air temperature crossing the radiator. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 10, 2014 Share Posted June 10, 2014 (edited) No, I'm saying the heat source is filtered keeping the heat available to radiate lower, resulting in lower temperatures. The Atmospheric guys who I talked to related the transmission of UV directly to the absence of Aerosols in the upper atmosphere. It is independent of humidity at the ground level as I understood it. They explained the diffusion of the suns rays in the upper atmosphere by water droplets filters the UV to a great extent not experienced out West. They were the ones who drew my attention to the "deep blue sky" compared to what I was accustomed to seeing in Michigan as I grew up...more Chevy LUV "Sky Blue" than the deep DARK blue you get without the aerosols. Maybe Hawaii gets similar thermal phenomenon... There is a thermal layer above the Tarmac. You can measure the gradients with a fast-acting thermocouple. Thermocouples placed in the shaded cowl inlet area (air inlet to cabin for the heater blower apparatus) will usually read the lowest-near Ambient, the leading edge of the hood will generally have a reading lower than one on the bumper, which is lower than one on the valence... But they all will usually be lower than cabin air inlet, or a sensor duct taped to your 6' CB Whip Antenna bolted to the back bumper. I believe if you shot it with a thermal imaging camera you might be able to see it. The examples I cited of Baker and Iowa were my "Eureka" moment that got me looking into "why" it existed. 85 ambient and 120 into the radiator, 100 ambient and 103 into the radiator. There is no doubt in the desert southwest the thermal layer is far hotter than most places back East. Seeing the temperature within 10 degrees of ambient during the daytime was just not something I'd experienced until Iowa as we were driving at night, in inclement weather, etc. To that point. When the sun came out, that's when it got interesting. I have not seen 160F thermal layering at the 24" sensor height like driving Route 66 into Holoman one year, anywhere East of the Mississippi, in fact, East of the Rocky Mountains (Only as far North as I80) I rarely saw anything over 110F on a 105 day. It was within 10-15 degrees of ambient in most cases. In the Holoman drive, I think it was over 40 degrees warmer (it may have only been 100 or 105F Ambient, but it was 160F air in the radiator sensor!) -- that was 2% RH. The "Dry Heat" everybody talks about...not a cloud in the sky, and dark, deep blue skies. I think on Okinawa there were similar conditions...but never checked. Just got my IR gun here in PI to do further testing, but we're coming into rainy season now so not till next May for those test results. Edited June 10, 2014 by Tony D Quote Link to comment Share on other sites More sharing options...
z-ya Posted June 10, 2014 Author Share Posted June 10, 2014 (edited) Over my head.... Edited June 10, 2014 by z-ya Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 10, 2014 Share Posted June 10, 2014 The 85's you two are comparing are probably from weather stations in the shade at about 6 feet high or more. Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 10, 2014 Share Posted June 10, 2014 The 85's you two are comparing are probably from weather stations in the shade at about 6 feet high or more. I think you also get a "double whammy" effect since the humid air also has a greater heat capacity and can pull more heat from the radiator. Quote Link to comment Share on other sites More sharing options...
clarkspeed Posted June 11, 2014 Share Posted June 11, 2014 I never knew that phenomena existed or ever thought about it. You would that SAE and automakers would have plenty of data on the subject. As far as cooling, I run a Ford double pass radiator with the oil cooler mounted in front of it. After I sealed off the front, my water temps went to 150 at Daytona on a 95 degree day. I installed another 190 thermostat with 1 hole drilled instead of 2, blocked 1/2 the grill, and got the temps rock steady at 190. I have been taping off the grill to block as much air as possible from going into the box and still keeping the 190, barely. However my oil temps have remained steady this entire time at around 240-250. They seem independent of water temp. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 13, 2014 Share Posted June 13, 2014 There is a reason every manufacturer in the world runs their prototypes up the Baker Grade, through the low country in Death Valley, and in a continuous loop during the hottest parts of summer. Generally oil will lead water slightly. Watch when your oil reaches that temperature, and you should see a correlation between rise of the water as the engine warms. Once stasis is reached between heat input and rejection it will stabilize until something upsets the equilibrium. Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 13, 2014 Share Posted June 13, 2014 (edited) There is a reason every manufacturer in the world runs their prototypes up the Baker Grade, through the low country in Death Valley, and in a continuous loop during the hottest parts of summer. Generally oil will lead water slightly. Watch when your oil reaches that temperature, and you should see a correlation between rise of the water as the engine warms. Once stasis is reached between heat input and rejection it will stabilize until something upsets the equilibrium. Yep. The Las Vegas Strip is another - same dry hot air, and seemingly perpetual bumper to bumper stop and go driving for worst case cooling airflow. That, and the amenities after a loooong day of driving around in the heat (it's less fun than it sounds) are less rustic... ever been to Furnace Creek? Gimme the Bellagio any day! Of course that only works for powertrain and hvac - type testing. Poor brakes guys still have to rough it. Edited June 13, 2014 by TimZ Quote Link to comment Share on other sites More sharing options...
johnc Posted June 13, 2014 Share Posted June 13, 2014 Poor brakes guys still have to rough it Funny! Rode up behind a group of these guys earlier this year in Death Valley. They were on the brakes non-stop coming down into Panamint Valley on the 190. I blasted past them on my Ducatti and stopped at the Panamint Springs Resort for a beer. Then pulled in later, brakes smoking on their 2014 BMWs, which weren't. They sat at the next table and I asked them why they were riding the brakes? Their reply was, "Bremsprufung in der Hitze" which I had to translate on my phone. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 13, 2014 Share Posted June 13, 2014 Oh, the reason they do it is because Afghanistan doesn't have a good testing facility... Quote Link to comment Share on other sites More sharing options...
TimZ Posted June 13, 2014 Share Posted June 13, 2014 Oh, the reason they do it is because Afghanistan doesn't have a good testing facility... No Bellagio there, either... Not even a Circus! Circus! Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 15, 2014 Share Posted June 15, 2014 Give me Dead Goat Soccer on Horseback ANY DAY over David Cassidy. Spamalot is gone, Vegas is dead to me now! Quote Link to comment Share on other sites More sharing options...
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