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FLORIDA STATE UNIVERSITY / FAMU-FSU
COLLEGE OF ENGINEERING
CONCLUSION
Testing
- After testing the heat exchanger, the
results showed that there are definitely areas where improvements are needed.
Since there was a time constraint some of these areas could have been explored
in more detail and solutions found, but since there was not, further testing is
suggested. The areas where more testing and problem solving should be done are
listed below. However, the heat exchanger proved to be successful and
beneficial.
- The heat exchanger is beneficial for a
couple of reasons. One is because it could save on average just shy of 0.11
cents a load. This means about $32 a year based on 300 loads per year done in a
house hold and around $315 a lifetime based upon a lifetime of a dryer to be 10
years. Another reason is if someone were to use the heat exchanger on their
dryer it would also help global warming by reducing not only the CO2 emitted
into the air but the water vapor as well.
Ways to maximize efficiency
- Most modern dryers now have relative
humidity sensors. This means that they can detect when the moisture in the air
is being reduced. Dryers equipped with a heat exchanger would need a moisture
sensor. In addition, most dyers use residual heat to dry the clothes at the end
of the cycle. The idea is that at this point, enough moisture has been removed
so the clothes are almost dry. The higher temperature air is not required.
Dryers with a heat exchanger should be calibrated to take into account the fact
that the temperature will drop slower because of the heat exchanger. This means
that the dryer with the heat exchanger can enter this energy saving period
earlier and stay there longer.
Installation
- The heat exchanger should be installed
after the fan. This is to insure, that additional blockage is not created when lint
builds up in the heat exchanger. On existing dryers the higher air flow
velocity values are seen after the fan. The exhaust air velocity will be
reduced as it passes through the heat exchanger, so the higher velocity values
seen after the fan are needed to keep the lint moving out of the system.
Other Recommendations
- Future designs of the heat exchanger may
be rectangular. Instead of having to clean the heat exchanger by opening the top,
it would be better to have it open from the side. The heat exchanger should
still be six by six to maintain the same air flow through the exchanger. This
is important because if the size of the outside shell of the heat exchanger is
reduced then the air flow through the heat exchanger will be reduced. If it is
reduced too much, the effectiveness of the heat exchanger will drop. Lint will
build up in the system more frequently. If this occurs it could be a potential
fire hazard.
Proposed rectangular design which would fit
better into the back of a dryer and be easier
to clean with a side door held shut via clamps.
FAMU-FSU