[jeff5may]

I believe the near-future improvements in residential HVAC will come in the form of variable-capacity inverter compressors (like the mini-split units use) as well as the split-evaporator designs (like the ejector-split design in the prius). The stacked-compressor idea was pretty much put to death by Hallowell and the Acadia units. Although not a bad idea on paper, very few refrigeration engineers will want to go out on a limb after the miserable failure of the Acadia units. Like the hyper-heat units by Mitsubishi, they favored raw BTU output at low temps over high COP.

For us hacking types, the stacked compressor design remains a good source for experimentation, especially with air-source units. With water-source units, inverter technology and digital controls have much room for improvement to fully realize the energy that can be saved.

In college courses, especially at the university level, speculation does not always balance correctly with reality. The professors intentionally say things in class to lead you down a path of failure, just to see how sharp you may be. In some courses, the ability to sniff out the BS early on is the only thing that allows some to pass while others fail. In their minds, this prepares the students for the chaos they will regularly have to sort out as engineers or scientists or lawyers or executives or whatever. Some of these ideas are ancient in nature and have already been disproved or revised to match reality. The lesson learned is not to believe everything you hear, to think critically before wasting time needlessly chasing your tail. Many brilliant people drop straight out of school for this very reason. In their minds, they would rather just get on with their own progress than sit through years of endless lectures that may or may not be useful to them in the future.