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Evaluation of a variable suction gas heat exchanger in a liquid chiller system using carbon dioxide as refrigerant


A prototype refrigerated seawater (RSW) system using carbon dioxide (CO2) as the refrigerant in a transcritcal process has been designed, built and tested experimentally. The system was equipped with a variable capacity suction gas heat exchanger (SGHX) which allowed operation at optimal
evaporator refrigerant charge. A simulation program for finding the optimum SGHX capacity at different
operating conditions has been developed and used.
Steady state experiments were done in both cooling and combined cooling / water heating mode at discharge pressures between 50-90 bar and cooling water temperatures between 10-25°C. Measured cooling capacities at steady state varied between 17-38 kW depending on the ambient cooling water
temperature. Highest cooling capacity was measured at 10°C cooling water temperature and 70 bar discharge pressure. The optimum coefficient of performance (COP) was measured at 60-70 bar discharge pressure for cooling water temperatures below 20°C and 80 bar above.
In hot water heating mode water temperature of 80°C was achieved without problems but with low efficiency due to a gas cooler not designed for this operation.
This work indicate that a variable capacity SGHX concept appears not to be beneficial with cooling water temperatures below 25°C, but could have a potential at higher temperatures.
Generally, the prototype CO2 liquid chiller system worked stable and well.


Academic article




  • Inge Håvard Rekstad
  • Trygve Magne Eikevik
  • Sondre Sætrang
  • Yves Ladam


  • Norwegian University of Science and Technology
  • Unknown
  • SINTEF Energy Research



Published in

Science et technique du froid



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