What value does introducing this equation bring to us?
A meaningful metric that removes advertising hype.
A way to isolate sub-system components one a time to determine their overall impact on the total cooling. (change fan speeds and see a quantitative change, big or small, in the number)
A way to compare different radiators objectively.
A way to fine-tune your cooling solution with better TIM, measuring the effectiveness of de-lidding, etc.
What does a snapshot in time tell us about cooling capacity?
The short answer is a number that indicates how well your cooling solution is working at that moment. Bigger numbers are better, of course.
How much harder is your system working in the summer vs the winter? Compare your data over time by noting the changes in room temperature.
Results can be all over the map due to all of the variables not accounted for, right? What if I had the same hardware but better tim or block? Does this really show its potential? Or the current state only?
Now you're starting to get it, I think. Yes! Change ONE THING in your system, under same load same room temp, and you can observe how the INDIVIDUAL DIFFERENCE is better or worse than the prior one. I think you are thinking there needs to be a "TIM variable" and a "cold plate variable," but the beauty of it is, the COLLECTIVE effectiveness or ineffectiveness shows up in the OUTPUT TEMPERATURE. So every component of your cooling solution IS in the equation!
Better TIM = higher score than before.
Better cold plate = higher score.
So you can isolate and run your own tests and then put the best of ALL OF THEM in and have an even better system.
If you're still not sure about it, consider this.
My condenser with all that copper is so good, that whether I run 1 fan on it or 4, it won't change my HRQ number by more than 5%.
That means the CONDENSER is doing a bulk of the work at 200-205 watts.
If I ever get more cores/hotter chips, I know the fans will be contributing more once the system shows much more than the 200 watt being used.