refrigeration subsystem (ARS) and compression refrigeration subsystem (CRS) operated as high-
temperature and low-temperature circuits respectively, and were combined to form a cascade refrigeration
system. The two circuits were connected to each other through a cascade heat exchanger (CHEX), which
acted as an evaporator for the ARS and a condenser for the CRS. The low-temperature portion of the
external heat source and the exhaust vapor of the TUR provided heating loads for the absorption
subsystem in GHEX and the reboiler (REB), respectively. The TUR provided the power required by the
compressor (COMP) in the CRS. External power was not required, but a mid-temperature heat source for
the new system was required. Therefore, this system could be used as a stand-alone unit for refrigeration
at low temperatures.
A typical two-stage NH3/H2O refrigeration system was selected as the reference system in this study,
as shown in Fig. 1(b) [7]. The two-stage system is obtained by adding a low-pressure branch containing
one low-pressure evaporator, one low-pressure absorber, two heat exchangers, two throttling devices, and
one pump to a conventional single-stage NH3/H2O absorption refrigeration system.