Environmental Engineering Reference
In-Depth Information
is operating with ozone-depleting CFCs. Therefore, no matter what type of refrigerant is in
use, it needs careful handling to avoid leaks and venting. Following are some actions to pre-
vent refrigerant leaks into the atmosphere suggested by the Alliance for Responsible
Atmospheric Policy (ARAP):
Use only technicians with training in refrigerant handling when servicing refrigeration
equipment.
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Develop a preventive maintenance plans that includes periodic inspections of tubes carry-
ing refrigerant.
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Monitor systems for refrigerant leaks.
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Minimize the number of connections of tubes carrying refrigerant.
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Size the equipment to match the refrigeration load thus minimizing the amount of refriger-
ant used in the equipment.
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Recover, recycle, and reclaim all refrigerants (ARAP, n.d.).
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Potential technologies for refrigerated transport
Absorption cycles using waste heat from truck engines
As seen in Chapter 11, absorption refrigeration is a viable alternative to traditional compres-
sion refrigeration when waste heat is available. Diesel trucks have a thermal efficiency of
around 40 percent, so considering that the heating value of diesel is 35.4 MJ/L, about 21 MJ/L
of diesel burned are dumped into the atmosphere that could be used in an absorption refrig-
eration system for a tractor trailer (Tassou et al., 2008). An additional benefit of using absorp-
tion refrigeration is the elimination of HFCs and HCFCs and replacement by more benign
refrigerants (see Chapter 8).
Koehler et al. (1997) developed and tested an absorption refrigeration prototype suitable
for a truck trailer that was run by the exhaust gases of a diesel engine. The system had a cool-
ing capacity of around 5 kW and a coefficient of performance of 0.27. Through simulations
they found that the heat generated by the truck's engine is enough to run a refrigeration system
on highways, but the heat would be insufficient in city driving (Koehler et al., 1997).
Solar photovoltaic
Working independently, the University of Southampton in the United Kingdom and Sandia
National Laboratories in the United States developed prototypes of refrigerated semi-
trailers powered by solar photovoltaic (PV) energy. The systems have a PV array mounted
on the trailer roof, an inverter to convert the direct current into alternate current, and a
compressor run by an electric motor (Bahaj, 2000; Bergeron, 2001). These are some of the
findings:
The area on top of the trailer can be enough to mount panels and produce enough electric-
ity to run the refrigeration system most of time.
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Better insulation, such as vacuum panel insulation, in the trailers would help to reduce
refrigeration needs by decreasing the thermal load through heat gain.
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Auxiliary power systems are necessary to operate at night or during cloudy days.
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From an economical standpoint, the solar system can be competitive depending on the
price of diesel.
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Operation in sunny cooler climates has more favorable return on the investment.
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