Fog Chiller - Part 3
The Enclosure
The copper coils will take heat energy from the fog traveling
through the heat exchanger. In addition to this action, by cooling
the metal duct material, we can further extract heat from the hot fog.
The best, or at least easiest, way to lower the temperature of the
metal duct is to surround it with something cold. Since I'll be
pumping ice water through the coils, It would make sense to
submerge the entire heat exchanger assembly into the ice water.
The Box
I built a box that will become the enclosurefor this fog chiller. Nothing fancy, just six
pieces of plywood. (including the lid)
I used 3/4" cdx plywood. It's strong, and
it's relatively inexpensive. The wood will be
sealed against any possible water infiltration,
and a paint job will improve it's appearance,
so in my opinion, 3/4" cdx plywood is
the material of choice.
Parts - cut list
Base.... ...........3/4"th. x 22"w. x 39"l. (1)
Side A......3/4"th. x 12"w. x 40 1/2"l. (2)
Side B............3/4"th. x 12"w. x 22"l. (2)
Lid.......3/4"th. x 23 1/2"w. x 40 1/2"l. (1)
These measurements are based on the dimensions of my finished
heat exchanger. These will allow for roughly 3" clearance on all sides.
These measurements are also based on "butt joinery" where the
boards are attached face to edge without any additional joints.
Finally, these measurements are based on the provision that
3/4" sheathing (CDX, BC, P.T., Marine plywood, etc.)
will be used during the construction process.
This box was built with common tools - a "skil" saw, a cordless drill,
and measuring / marking tools. While specialized cabinet-making
machinery would simplify this part of the project greatly,
no special tools are necessary. Double check your measurements
during layout, and use a straight edge guide when making your cuts.
Check for length and square often.
The pieces are assembled with wood glueand course thread screws. When driving
screws into the edge grain of plywood,
(which technically isn't grain at all...)
pre-drill holes for the screws.
Failure to do so will usually result in nasty
splits, or stripped threads. Be careful to
avoid over-tightening screws in plywood.
It is easiest to assemble the carcase dry, disassemble, apply the glue, then re-assemble.
Check everything for square, and wait patiently for the glue to dry.
Drill holes through the wallthat will accommodate the heat exchanger.
4" holes are easily made using a hole saw,
but could be made using a jigsaw or
rotary cutting tool (roto-zip, etc.)
Drill a hole for the pump's power cord,
and another to receive a drain pipe.
This chiller will be pretty heavy when
full of water, so a drain might be a necessity.
Wood will absorb water.I chose to seal the carcass inside and out with
a 2-part epoxy resin material. Once cured this
product is completely water proof.
The temperature inside the box will be lower
than the temperature of the outside air,
so I sealed the outer surfaces of the box
to combat any condensation that will occur.
2 coats will guarantee complete coverage.
Place the heat exchanger inside the box and determine the length
of the inlet and outlet pipe(s). Be sure to leave a small gap between
the heat exchanger and the pipe. This will be necessary when installing
the heat exchanger between two fixed lengths of pipe.
The photos above show the p.v.c. inlet and outlet.
The inlet (left) is installed flush with the outer plywood wall
The outlet (right) uses the "bell" end of the pipe. Using this will
allow me to attach lengths of similar pipe to direct the fog as needed.
The photo at leftshows the heat exchanger sitting
on riser blocks made of scrap
aluminum square stock.
This will allow more cold water to
surround the exchanger.
Also, it provides a place to
"anchor" the exchanger to the box.
The photo at right shows the clampsthat will be used to secure the
heat exchanger within the box.
Regular stainless steel band clamps
will hold the exchanger in place.
The (light duty) rubber pipe-to-pipe
clamps will attach the exchanger to the
inlet and outlet pipes while
providing a water tight seal.
The photos above show the project near completion. I installed swivel casters on the
outlet end of the cabinet. These will help during transit and storage, and will
be out of way while the chiller is in use. Hardware (hinges, latches, etc.) have
been installed. The permanent joints were sealed and allowed to cure.
I chose to carpet the outside of the chiller.
This was a decision based solely on preference, and
has nothing to do with the performance of the fog chiller.
December 7, 2002
This photo (right) shows fog passingthrough the chiller "warm," that is,
without any water or ice in the box.
This shows a blast of fog
approx. one second in duration.
Due to excessive wind, we had to take
the experiment inside the workshop
for further testing.
This photo (left) shows the fog passing through
the chiller half - filled with ice and water.
The chiller effectively lowers the temperature
of the fog below that of the room - which
was 58 degrees this morning. (entirely too
cold for Florida...)
This photo shows the fog exiting the chiller AFTER the fog is actually
produced. While the fogger is running, the cool fog projects three
or four feet, then falls to the floor and spreads.
Above are photos of the fog lit with two different gel-colored lamps.
Back-lit tombstone (left).
Front-lit tombstone (center).
Lamps, as seen through chilled fog (right).
The chilled fog looks great in "normal" light, but experimenting with
different lighting angles and colors will surely prove even more amazing.