[christofoo]

I was thinking about my calculation a few weeks ago and it occurred to me that heat is lost to the exhaust as well as the radiator. Air passing through the radiator is (probably) only heated to 180-200F or so, but the exhaust is at about 1000F when it exits the engine compartment, so it's significant. I worked the exhaust heat out to about 22% of the ICE thermal load, and I updated my spreadsheet to reflect that. I edited my first post with the new attachment.

Also, I'm pretty sure the number I used for ICE thermodynamic efficiency, 22%, is lower than I'd expect under climbing conditions. I think 28% is more likely, at least for economy cars, considering low throttle losses during climbing.

Net result; most of my suggested grille openings have gone down by almost 50%. I edited my original table accordingly.

Originally Posted by christofoo

...

• Sustained 5% grade climb at 65MPH, 3,000 lbs gross weight, 120F ambient, 15MPH tailwind, 5,000ft elev., 2kW AC: 167in^2 (4.5in^2/hp) 89in^2
• Sustained 5% grade climb at 65MPH, 3,000 lbs gross weight, 120F ambient, 0 tailwind, 5,000ft elev., 2kW AC: 141in^2 (3.5in^2/hp) 81in^2
• Sustained 5% grade climb at 65MPH, 3,000 lbs gross weight, 100F ambient, 0 tailwind, 0ft elev., 1.5kW AC: 96in^2 (2.2in^2/hp) 56in^2
• Sustained 3% grade climb at 65MPH, 2,500 lbs gross weight, 100F ambient, 0 tailwind, 0ft elev., 1.5kW AC: 66in^2 (2.3in^2/hp) 38in^2
• 0% grade, "loaded sedan" at 75MPH, 100F ambient, 0 tailwind, 5,000ft elev., 0kW AC: 48in^2 (2.2in^2/hp) 32in^2
• 0% grade, "loaded sedan" at 75MPH, 40F ambient, 0 tailwind, 5,000ft elev., 0kW AC: 30in^2 (1.3in^2/hp) 20in^2
• 0% grade, "aerocivic" at 70MPH, 40F ambient, 0 tailwind, 0ft elev., 0kW AC: 15in^2 (1.1in^2/hp) 10in^2

...