Peltier and Phase Change - usefull?

[whitewale]

I noticed several people asking if they should combine a phase change unit with a peltier element and did some reading. From what I found, in theory you can reach lower temperatures on the cold side of a peltier element by chilling the hot side to below ambient. The deltaTmax of a peltier element is mainly dependent on the hotside temperature. But, for all practical purposes it is a highly questionable set-up. The performance of the peltier element, in terms of energy transported, suffers greatly higher the deltaT, putting extreme strain on your precooler. On this Melcor page you you can see the relation of deltaT and pumped energy, please note that the scale on the right is logarithmic and covers 5 orders of magnitude. So unless your phase change system is extremely oversized, your peltier element will raise the temperature on the hot side, making it questionable if the additional effect of the peltier can actually lower the CPU temperature below that of your phase change system alone.
On the other hand, using chilled water/melting ice in your watercooled peltier should have a strong effect on the CPU temperature.

 

[mesyn191]

Its basically a ghetto way of doing a cascade cooler and actually takes some careful planning to make it work (what type of refridgerant to use, how much refridgerant, etc...).

AFAIK it was discussed for a while on the xtremesystems.org phase change forum but I'm not aware of anyone who has done it mainly due to the problems you mentioned. Most of the people who want to do cascade coolers have chilly1 or someone else who is a pro HVAC engineer who knows what they're doing rather than go ghetto as cascades can be fairly dangerous depending on what type of refridgerant you use (I believe Ethylene is the most common in cascades).

 

[z3r0-]

I think your thinking about a pelt as a HX or something that wouldent work... The thread starter is talking about using chilled liquid on a TEC I belive. It works but efficiancy drops and it isint worth the added load and money to run the PSU.