I have never heard of someone doing what you are talking about. Having the thermal expansion valve alone would be hard enough to do inside the computer, much less have the equipment for the rest of the cycle. There is no way to control the pressure necessary for R-134 to be effective on the scale required for computers. That said, you might be able to get it done, but it would be so expensive, it just isn't practical. Standard water cooling works because you don't have raise and lower the pressure for the cooling cycle like you do with R-134. So water cooling doesn't require a compressor or thermal expansion valve.