humans have faced the challenge of maintaining body heat in cold environments; consequently, the design an‎d production of thermally insulating clothing have become a fundamental necessity for life in cold climates. Winter jackets reduce heat loss primarily by trapping air within their structure, an‎d bird down, owing to its favorable insulation-to-weight ratio, is among the most efficient insulating materials used in such garments. Despite its widespread application, the thermal behavior of down-filled systems is influenced by a combination of structural an‎d environmental factors, the systematic investigation of which is essential for improving product design an‎d performance. In this study, the thermal perfor-mance of winter jacket assemblies containing down an‎d feathers was investigated with the aim of ana-lyzing the influence of key parameters an‎d developing a quantitative understan‎ding of heat transfer mechanisms. Experimental eva‎luations were conducted using a skin model simulator, a Togmeter, an‎d numerical modeling performed in the COMSOL Multiphysics environment. Samples were analyzed under controlled conditions while varying critical parameters, including mass per unit area, down-to-feather ratio, shell fabric type, stitch spacing, an‎d moisture condition (dry an‎d wet states). The results indicated that increasing mass per unit area did not lead to a statistically significant difference in ther-mal conductivity, with effective thermal conductivity values ranging from 0.0398 to 0.0417 W·m⁻¹·K⁻¹. However, increasing mass per unit area led to greater thickness an‎d, consequently, higher thermal re-sistance, which ranged from 0.371 to 1.067 m²·K·W⁻¹. Analysis of different down an‎d feather ratios revealed that a higher down percentage alone does not guarantee superior thermal performance; fill power must also be considered. Increasing the down content from 60% to 80% did not produce a sig-nificant improvement in thermal performance, as all samples exhibited similar fill power values below 500 in³·oz⁻¹. The shell fabric type was found to have a more pronounced effect on thermal performance at lower mass per unit area. Furthermore, testing under wet conditions resulted in a reduction in assem-bly thickness an‎d a noticeable increase in thermal conductivity; however, after drying an‎d homogeni-zation, the initial thermal properties were largely restored. A comparison between experimental data an‎d numerical simulations demonstrated that the proposed model can predict the thermal behavior of the samples with acceptable accuracy, with discrepancies remaining within engineering tolerance lim-its. Overall, the findings indicate that the thermal performance of down-filled winter jackets is opti-mized by achieving an appropriate balance among mass per unit area, down quality, shell fabric char-acteristics, an‎d stitch geometry. For low mass per unit area, closer stitch spacing (7–10 cm) combined with a higher down percentage is recommended, whereas for higher mass per unit area, stitch spacing between 13 an‎d 20 cm is more effective. Additionally, when the down-an‎d-feather content exceeds 175 g·m⁻², the rate of increase in thermal resistance diminishes.

افسانه ولي پوري , عبدالكريم حسيني

فاطمه حقيقت

پرهام سلطاني , مهدي حجازي