Design of Refrigerated Railcar for Addis Ababa – Djibouti Railway
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Date
2015-05
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Addis Ababa University
Abstract
Refrigerated railroad cars, known as reefers, are railroad rolling stock designed to carry
perishable freight at specific temperatures. They are insulated boxcars that keep the cargo at a
regulated temperature. As soon as railway bulk freight transportation has emerged and railroad
cars had the capability to keep a load cold, the potential growth of the meat, vegetables, fruits
and brewery industries became nearly unlimited. In this thesis, a current technology and
achievement of a cold-room system on transportation system especially in a railroad car was
investigated. A refrigerated railroad car with electric powered integrated R134A vapor
compression refrigeration system needs to be designed for local manufacturing. The refrigerated
railroad car with internal dimensions (17.72 * 2.66 * 2.52) has to be able to preserve and
transport a maximum charge of 60000kg of chilled/frozen meat or 42000 kg of chilled vegetables
in 24 hours (1 day) to the next mode of transportation, sea transport to Middle East Market. The
meat to be frozen and transported enters the refrigerated rail car already frozen to a
temperature of about -10°C. Also the meat and vegetables to be chilled and transported enters
the car at a temperature of about 2°C and 3°C respectively. The frozen meat leaves the
refrigerated railcar and transferred to the refrigerated ship or reefer container at -18°C.
A pre-fabricated outer facing with an injected polyurethane is used as an insulation system for
the car envelop design and the thermal heat resistance of walls, ceiling and floor is calculated
with standard wall thickness. In this design of car envelop the refrigerating space and air
circulation is determined for obtaining the optimum air velocity inside the refrigerated railcar.
In these design work we use condensing temperature 48°C. Average summertime temperature of
AYSHA is 38°C, so there is an average margin of 10°C. For our design purpose we will assume
an ambient temperature of 40°C. With these parameters we made cooling load calculations
analytically and using computer program and the total cooling load is found to be approximately
19 kW. We use this amount refrigeration capacity for the design process like system component
selection and sizing. And finally using the refrigerated railcar envelope and selected
refrigerating equipment the most appropriate system configuration has been made.
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Keywords
Thermodynamic cycles, heat transfer, transport refrigeration