Modelling of the 1D Convective Heat Exchange between Logs Subjected to Freezing and to Subsequent Defrosting and the Surrounding Environment/ Egydimenziós konvektív hővezetés modellezése fagyott és normál állapotú rönk és környezte között

Open access

Abstract

A 1D mathematical model for the computation of the temperature on the surface of cylindrical logs, tsr, and the non-stationary temperature distribution along the radiuses of logs subjected to freezing and subsequent defrosting at convective exponentially changing boundary conditions has been suggested. The model includes mathematical descriptions of the thermal conductivity in radial direction, λr, the effective specific heat capacity, ce, and the density, ρ, of the non-frozen and frozen wood, and also of the heat transfer coefficient between the surrounding air environment and the radial direction of horizontally situated logs, αr. With the help of the model, computations have been carried out for the determination of αr, tsr, λsr, and 1D temperature distribution along the radiuses of beech logs with diameters of 0.24 m, initial temperature 20 °C, and moisture content 0.4 kg·kg-1, 0.8 kg·kg-1, and 1.2 kg·kg-1, during their freezing at -20 °C, and during subsequent thawing at 20 °C.

Kivonat

Célunk egy 1D matematikai modell létrehozása volt, amely kiszámítja a hengeres farönk felületi hőmérsékletét, tsr, és a rönk sugara menti hőmérséklet-eloszlást egy olyan hengeres farönkön, amelyet lefagyasztottak majd kiolvasztottak exponenciálisan változó hőátadási körülmények között. A modell magában foglalja a sugárirányú hővezetési tényező, lr, az effektiv specifikus fajhő ce, és a sűrűség ρ matematikai leírását nem-fagyott és fagyott állapotú faanyag esetében. Tartalmazza továbbá az αr radiális irányú hőátadási tényezőt a környező levegő és a vízszintesen fekvő rönk között. A modell segítségével számítások történtek az αr, a tsr, és a λsr, valamint az 1D hőmérsékleteloszlás meghatározására 0,24 m átmérőjű bükk rönknél a sugár mentén a következő feltételek mellett: kezdeti hőmérséklet 20 °C, a nedvességtartalom értékei 0,4 kg·kg-1, 0,8 kg·kg-1 és 1,2 kg·kg-1, a-20 °C-os fagyasztás során és az ezt követő felolvasztás folyamán 20°C-ig.

References

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Acta Silvatica et Lignaria Hungarica

The Journal of University of West Hungary

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CiteScore 2016: 0.50

SCImago Journal Rank (SJR) 2016: 0.241
Source Normalized Impact per Paper (SNIP) 2016: 0.460

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