Magnetic resonance velocimetry-based diagnosis-modification-validation framework for flow and acoustic improvement in heat pump tumble dryer machine room

Abstract

Complex internal flow passages in heat pump tumble dryers often generate flow separation and secondary motions that degrade flow and thermal performance and increase flow-induced vibration and noise. This study presents a comprehensive diagnosis-modification-validation framework that integrates magnetic resonance velocimetry (MRV), omni-directional integration (ODI), and direct vibro-acoustic measurements. MRV measurements of a 0.4-scale three-dimensional printed reference model identified pronounced separated flow, large-scale secondary flow, recirculation, and elevated turbulent kinetic energy (TKE). Based on this diagnosis, four targeted passive structural modifications were introduced. The modified design exhibited substantially improved flow uniformity, marked suppression of secondary flow and separation, and more than 50% reduction in high-TKE regions. ODI-based reconstruction of the three-dimensional pressure field further demonstrated enhanced pressure recovery in the inlet, mid, and outlet regions. In addition, a surrogate indicator derived from the volumetric mean velocity field was proposed for rapid design screening and was found to correlate well with the reduction ratio of average TKE. Direct vibro-acoustic measurements showed that the flow improvement translated into broadband attenuation of structural vibration and a 3.2 dB reduction in overall radiated noise. These results demonstrate that the proposed framework provides an effective and generalizable experimental methodology for diagnosing and improving complex opaque internal flow systems.