BACKGROUND: I am an electrical engineer working mostly in test engineering. About 20 year ago, I was tasked with designing an electrical test load, which itself used fans and large heatsinks to remove heat from the test item ( a 10 KW 3-phase generator from a U.S. miliary jet ). I did ask for advice on heatsinks from co-workers who were mechanical engineers. Although we did use bare aluminum heatsinks, I never thought at the time to ask if a black-anodized radiator would be more efficient. Would the difference be $$1%$$ or $$2%$$, or $$15%$$?