In-situ quantification of air leakage in a heat pump dryer under realistic operating conditions

초록

Air leakage from internal circulation pathways is an insufficiently resolved source of energy loss in heat pump clothes dryers (HPCDs). Existing leakage quantification methods are mainly based on pressurization tests under non-operational or quasi-static conditions, limiting their applicability to realistic dryer operation involving active airflow, drum rotation, and evolving pressure fields. In this study, an in-situ CO2 tracer-gas method was developed to quantify air leakage in a household HPCD under operating conditions. Local sampling locations were selected using internal pressure mapping, and probe suction flow rates were optimized by CFD to achieve sampling efficiencies above 96% while limiting disturbance to the native flow field. Leakage was measured under 0, 5, and 12 kg laundry loads using localized sampling and independently validated by global chamber sampling. The total leakage obtained from localized measurements agreed with global measurements within approximately 8%, confirming the representativeness of the location-specific approach. The rear drum seal was the dominant leakage pathway, while internal leakage sources accounted for approximately 70% of total leakage. A passive 7.5 cm2 bypass installed upstream of the drum inlet reduced drum surface pressure from approximately 4–7 Pa to −2 to +2 Pa and decreased total leakage from about 120 g to 45 g, corresponding to a 65–70% reduction. These findings show that dryer leakage is governed by local pressure distributions and structural pathways. The proposed method provides a practical framework for operation-resolved leakage diagnosis and pressure-based mitigation in energy-efficient dryer design.

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