The refrigeration system modeled in this work was
based on a prototype, which is under construction in the
Mechanical Engineering Department of the Federal
University of Minas Gerais-Brazil, supported ®nancially
by the Foundation for the Research Support of State of
Minas Gerais-FAPEMIG. The plant was designed to
operate with the R134a and is composed of an open
speed-controlled compressor, a manual expansion valve,
an evaporator, a condenser and a subcooller. The con-
denser is made up of two concentric copper tubes. The
refrigerant ¯ows inside the internal tube and water ¯ows
in the annular space in the opposite direction. The eva-
porator is composed of an external shell and three
internal copper tubes. The refrigerant ¯ows inside the
three internal tubes and the secondary ¯uid, a blend of
water and ethylene glycol, ¯ows into the external shell in
the opposite direction.