Automotive AC System Induced Refrigerant Hiss and Gurgle 2013-01-1890

Traditional IC engine powered vehicles readily mask the lower amplitude transients like hiss, clicks and slight tones. However, due to the popularity and expected increase in number of hybrid and electrically driven automobiles all around the world, all the OEMs are concerned about the vehicle interior quietness and sound quality. Refrigerant system induced hiss/gurgle is quite normal phenomenon but its excessive levels and frequent occurrences can be objectionable to demanding customers. Introduction of new environmentally friendly refrigerants (HFO-1234yf), A/C compressors with built-in oil separation (reduced damping in evaporator), and use of IHX with coupled suction and liquid lines, may lead to increased refrigerant system induced hiss and gurgle.

Operation of typical A/C system generates steady-state and transient noises that consist of audible tones and high frequency hiss. A/C system usage is seasonal and operation controlled by the customer, hence the noise (if present) is readily perceived and flagged as a concern. This paper focuses on diagnostics of refrigerant system induced noise sources and spectral characteristics. A systematic approach is used to quantify and identify the paths of the refrigerant system induced hiss/gurgle propagation at the component, subsystem and vehicle levels. Also discussed are the most cost-effective counter-measures and guidelines for its suppression.