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Conversion of platelet incubator refrigeration system to R600a and performance optimization.

Number: pap. 2615

Author(s) : VÍSEK M., ELBEL S., HRNJAK P., et al.

Summary

Platelet incubators are refrigerated laboratory storage devices aimed at preserving platelets in liquid form at close to ambient temperature. Quality and shelf life of the stored platelets strongly depend on the storage temperature uniformity and continuous movement of the platelets provided by an agitator to avoid coagulation. Incubator manufacturers usually provide assurance that temperature uniformity will be within +/-1°C from the set point. Such strict requirement of uniformity is achieved by continuously running a forced convection vapor compression refrigeration system and by balancing excess cooling capacity with a controlled pulse heater located inside the cabinet. Dominant refrigerants currently employed in refrigerated laboratory equipment are HFCs with high GWP. In the future, HFCs will be gradually replaced mostly by flammable natural refrigerants of the ASHRAE A3 group such as R600a (isobutane), R290 (propane) and R170 (ethane) depending on the cooler size and application temperature. Flammable refrigerant charges are limited to 150g or less which in some cases requires complete redesign of the refrigeration circuit. The focus of this study was to convert the refrigeration system of a platelet incubator to hydrocarbon refrigerant. The selected incubator is able to store 32 apheresis bags and based on the required cooling capacity R600a refrigerant was identified as most suitable replacement for R134a. The baseline R134a system performance was experimentally evaluated across the range of ambient temperatures allowed by the manufacturer, from 15°C to 35°C and at 3 different cabinet set points 20°C, 22°C and 27°C. Attention was given to the energy consumption by distinguishing between contributions of individual components (compressor, fans, pulse heater, agitator, condensate tray heater and controller). Temperature uniformity was determined from measurements at 17 locations inside the cabinet over a 24 hour period. Afterwards, the refrigeration system was converted to R600a refrigerant and its performance was optimized by capillary tube size selection, refrigerant charge amount, evaporator fan speed and by replacing the condensate heater with a discharge gas loop. The redesigned machine required only 50g of R600a refrigerant charge, an average 20% lower energy consumption, cabinet temperature uniformity within the required +/-1°C for all tested conditions, and uniformity of +/-0.5°C at 15°C and 25°C ambient temperatures.

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Pages: 10

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Details

  • Original title: Conversion of platelet incubator refrigeration system to R600a and performance optimization.
  • Record ID : 30018915
  • Languages: English
  • Source: 2016 Purdue Conferences. 16th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2016/07/11

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