Abstract: For a specific outdoor unit model experiencing abnormal noise at the 6th harmonic frequency during heating operation, subjective evaluation indicated failure. Through quasi-steady-state compressor frequency sweep testing, along with modal and modal strain energy analysis of the compressor piping system, it was determined that the 6th harmonic exceedance was caused by structural resonance of the liquid receiver. An optimized solution involving reinforcement of the liquid receiver welded bracket was proposed to enhance connection stiffness and natural frequency. Experimental testing demonstrated that the optimized solution achieved a 19 dB reduction in peak noise level at the 6th harmonic compared to the original design. The abnormal noise was eliminated, and subjective evaluation results were favorable.

Key words: Compressor, Receiver, 6th order frequency, Welded bracket