There are a number of uses of hot water in buildings including showers,
tubs, sinks, dishwashers and clothes washers. In virtually all of these
cleaning applications, the wastewater retains a significant portion of its
initial heat energy - energy that could be recovered and re-used.
Estimates by the U.S. Department of Energy (DOE) indicate that the
equivalent of 235 billion kWh worth of hot water is discarded annually
through drains, and a large portion of this energy is in fact recoverable.
In cases where wastewater generation is in sync with the need for hot
water (e.g. a shower), a non-regenerative, straightforward heat exchanger
such as the GFX coil is an ideal solution.
Showering can account for nearly 80% of the annual water-heating bill for
families that wash clothes in cold water and take showers instead of
baths. Therefore, a drain heat recovery system such as the GFX coil
(rated at 50% DHR-efficiency) can lower water-heating costs by 40%.
How it works:
This straightforward design is a vertical heat exchanger that extracts
heat out of drainwater (usually warm) and applies this heat for preheating
the cold water entering the building. The GFX is installed into a section
of available, vertical drain line in a dwelling. The design (see right)
consists of a 3 or 4-inch central copper pipe (carries the warm
wastewater) with 1/2-in or 3/4-in copper coils wound around the central
pipe. Heat is transferred from the wastewater passing through the large,
central pipe to cold water simultaneously moving upward through the coils
on the outside of the pipe. The coils are flattened a little where they
touch the pipe and solder-bonded to the pipe to improve heat transfer.
The key to this patented device was the observation by the inventor that
wastewater clings in a flim-like fashion to the inside wall of the pipe as
it undergoes gravity flow in the open drain, and this greatly improves the
effectiveness of heat transfer from the falling drainwater to the copper
coils that wind around the pipe.
There are a number of uses of hot water in buildings including showers,
tubs, sinks, dishwashers and clothes washers. In virtually all of these
cleaning applications, the wastewater retains a significant portion of its
initial heat energy - energy that could be recovered and re-used.
Estimates by the U.S. Department of Energy (DOE) indicate that the
equivalent of 235 billion kWh worth of hot water is discarded annually
through drains, and a large portion of this energy is in fact recoverable.
In cases where wastewater generation is in sync with the need for hot
water (e.g. a shower), a non-regenerative, straightforward heat exchanger
such as the GFX coil is an ideal solution.
This straightforward design is a vertical heat exchanger that extracts
heat out of drainwater (usually warm) and applies this heat for preheating
the cold water entering the building. The GFX is installed into a section
of available, vertical drain line in a dwelling. The design (see right)
consists of a 3 or 4-inch central copper pipe (carries the warm
wastewater) with 1/2-in or 3/4-in copper coils wound around the central
pipe. Heat is transferred from the wastewater passing through the large,
central pipe to cold water simultaneously moving upward through the coils
on the outside of the pipe. The coils are flattened a little where they
touch the pipe and solder-bonded to the pipe to improve heat transfer.
The key to this patented device was the observation by the inventor that
wastewater clings in a flim-like fashion to the inside wall of the pipe as
it undergoes gravity flow in the open drain, and this greatly improves the
effectiveness of heat transfer from the falling drainwater to the copper
coils that wind around the pipe.