HumCooler: Heat Exchangers
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Heat exchangers are vital to getting useful work out of the HumCooler.
Although they tend to be trickier to build than stacks, they're much
more common devices than stacks, and basic prototypes should be
available off the shelf. (We hope.)
Unlike stacks, heat exchangers should be made of material that
conducts heat very well. Copper is the first choice, and excellent
for ambient temperature and cold-end heat exchangers. For the hot-end
heat exchanger, nickel is more popular because it doesn't oxidize like
copper at high temperatures.
Most heat exchangers are stacks of thin plates or fins, with liquid
running through a network of pipes to transfer the heat. [LIST
COMMERCIAL VENDORS HERE]
This figure is copied from Swift, p. 216 figure 8.9.
Most commercial heat exchangers use electric pumps to circulate the
coolant. We are seeking ways to build a HumCooler that does not
require electricity. One possibility is a
heat pipe,
which can transfer heat quickly and efficiently by evaporating a
working fluid at the source end, and condensing it at the sink end.
How practical this would be remains to be seen.
More references to heat pipe vendors that may be useful:
There is one critical dimension of the heat exchangers in a HumCooler,
the gas displacement length, which is how far a packet of gas
moves during one cycle of oscillation. The heat exchanger's thickness
(in the direction of gas motion in the resonator) should be about
equal to the gas displacement length, for maximum efficiency in
thermal transfer. [DIAGRAM AND EXPLANATION HERE]
This page maintained by
Wil Howitt
Last updated 21 June 2003