NVH Challenges with Introduction of new Refrigerant HFO-1234yf

Paper #:
  • 2017-01-0172

  • 2017-03-28
Due to regulations related to global warming, the auto industry is transitioning to the use of a new refrigerant R1234yf in many markets/regions. This transition to the new refrigerant was considered to be a minor development effort with main focus on improved sealing, improving cooling capacity with adding content such as Internal Heat Exchanger (IHX) to recoup the lower cooling efficiency of R1234yf compared to R134a. There were no redesigns of major refrigerant system components expected with the introduction of R1234yf. The actual implementation of this refrigerant has proven to be more challenging due to several NVH issues. Some of the challenges related to NVH are driven by the differences in refrigerant characteristics – mass flow rate, velocity of sound in refrigerant. Also, the material compatibility issues between the refrigerant, oil and different hoses have restricted the usage to a limited number of compatible hose types which are not optimized for NVH, which has prompted the industry to re-developing hoses for improved NVH performance. From a HVAC (air handling case) standpoint, the transition to the new refrigerant was supposed to be transparent, but due to several factors mentioned above, the damping treatment and isolation design of the evaporator (heat exchanger) had to be re-designed to improve NVH.
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