The H2C Cooling System
Dell's answer to heat problems in the XPS 710 H2C is the H2Ceramic cooling system (aka H2C or Hot-to-Cold). While many computer system manufacturers have used conventional water cooling solutions in their high-end machines, Dell has created their own hybrid of the water cooling and thermoelectric cooling methods.
Dell's H2C is a totally self-contained two-stage liquid/TEC hybrid cooling system. Dell has tried to combine the best qualities of water cooling and thermoelectric cooling into a single compact, safe and low maintenance cooling solution. To create the H2C system, Dell combined a very compact water cooling system with two TECs and integrated them into a plastic housing small enough to fit into the XPS 700 series case.
Like conventional water cooling systems, the H2C system uses a closed circuit of liquid (water mixed with coolant in this case) to shift heat away from the processor to a secondary cooling area where the heat can be removed from the system. A metal "cold plate" (ie. water block) is attached to the CPU where it absorbs the heat it generates. A pump continuously moves cool liquid to the cold plate and through the rest of the system. As the liquid moves through the cold plate, it takes heat away with it, cooling down the cold plate. The newly heated liquid is then pumped to a fluid-to-air heat exchanger (ie. radiator) where most of the heat from the cold plate is removed from the liquid. A 120mm fan pulls ambient room air through the heat exchanger, cooling it in the process.
At this point, the mostly cooled liquid then moves on to a Dell custom-designed thermoelectric heat exchanger. The TEC heat exchanger is essentially a water block sandwiched between two heatsink-cooled TEC units. As the liquid passes through, the two TECs use the Peltier effect to cool the water block, and therefore cooling the liquid within. Large heatsinks attached to the TECs soak up the heat they generate and are cooled by the same 120mm fan that cools the fluid-to-air heat exchanger. Finally, the cooled liquid gets pumped back to the cold plate to repeat the process.
As we mentioned earlier, TEC devices often suffer from condensation problems because the cold side of the TEC plate often gets cold enough to reach sub-zero temperatures. Dell dealt with this problem in their H2C unit by connecting the TECs to a combination of controller circuitry and system level firmware that keeps them from becoming too cold. The fan and pump are also thermally regulated so that the entire system doesn't cool the liquid lower than about 20 degrees Celsius, which is the average ambient room temperature. To help thwart evaporation, Dell used tubing made of a special low-permeation material. Dell claims the system can go seven years without the need for maintenance of any kind.
Dell claims their H2C system can cool an Intel QX6700 processor overclocked to 3.2GHz to 9 degrees Celsius lower than the standard air cooler used in XPS 710 systems not equipped with the H2C system. Dell also claims the H2C system is more effective than a conventional water cooling system and we tend to believe them. Unless augmented by some other process, the laws of thermodynamics prevent conventional water cooling from lowering the temperature further than whatever the ambient temperature happens to be since the water is itself, cooled by the air. Even the best water cooling setups can only cool to within a couple of degrees of the ambient temperature. Thanks to the dual TEC setup, the H2C system should be much more robust.
Unsatisfied with statistics and specifications, we put the H2C system to the test. First we measured the CPU's temperature (while factory overclocked to 3.2GHz) to be about 40C under load when the ambient room temperature was a comfortable 22C. Then we changed into T-shirts and artificially increased the ambient temperature to about 30C with a space heater. We recorded the CPU's temperature to be 44C under load, only a 4 degree increase despite the 8 degree increase in ambient temperature. Finally, we put on parkas and opened the window to allow the -18C air from outside to enter the room. When the room's temperature had stabilized at a chilly 10C, we ran the test again and measured the temperature to be 25C under load. So what does all that mean?
While our test was far from scientific, it should give a good idea of how the H2C system stacks up. The fact that the CPU temperature did not rise proportionally with the ambient temperature demonstrates the effectiveness of the H2C's design. Remember that the CPU is a toasty quad-core QX6700, with a TDP (Thermal Design Power) of 130 watts at its stock frequency of 2.66GHz, factory overclocked to 3.2GHz. These are pretty impressive results.