20.500.12556/DiRROS-7688 Internal and external moisture transport resistance during non-stationary adsorption of moisture into wood Notranji in zunanji transportni upor v procesu nestacionarne adsorbcije vlage v les The assumption that non-stationary sorption processes associated with wood canbe evaluated by analysis of their transient system response to the disturbance developed is undoubtedly correct. In general it is, in fact, possible to obtain by time analysis of the transient phenomenon - involving the transition into an arbitrary new state of equilibrium - all data required for a credible evaluation of the observed system. Evaluation of moisture movement during drying or moistening requires determination of external moisture transfer resistance from or to wood surfaces, as well as internal resistance. Time-dependent changes in the moisture content of the spruce (Picea abies Karst.) samples of different thickness were monitored gravimetrically, during which the frequency of weighing was in accord with thespeed of moistening. It was assumed that quasi-isothermal sorption processes associated with wood could be evaluated as first order systems. The characteristic time constant ? determines, wholly and uniformly, the time dependence of the sorption process for the relevant sorption range of wood tissue. The connection between the time constant and the thickness of the sample measured in the direction of the material flux is potential, with the power depending solely on the relationship between the external mass transfer convection and internal diffusion resistance. To determine the said resistances or coefficients of mass transfer convection and diffusivity, the experiment must be carried out on samples of varying thickness. It is only in this way that the external mass transfer convection and internal diffusion resistance can be correctly distinguished. Predpostavka, da je možno nestacionarne sorptivne procese, povezane z lesom, ovrednotiti z analizo njihovega časovnega prehodnega sistemskega odziva na nastalo motnjo, je nedvomno pravilna. V splošnem je namreč s časovno analizo prehodnega pojava, gre za prehod v poljubno novo ravnovesno stanje, možno pridobiti vse potrebne podatke za verodostojno vrednotenje opazovanega sistema. Vsak prehod v novo ravnovesno stanje je ne glede na lastnosti opazovanega sistema nestacionaren in kot tak primeren za analizo nestacionarnih pojavov, kot so na primer sorptivni procesi, povezani z lesom. Za analizo sorpcijskih transportnih značilnosti je treba poznati tako notranjidifuzijski kakor tudi zunanji masni prestopni upor. Časovno odvisne spremembe vlažnosti v smrekovih vzorcih (Picea abies Karst.) različnih debelinsmo spremljali gravimetrično, pri čemer je bila pogostnost tehtanja skladna hitrosti navlaževanja, se pravi v začetku največja, z naraščajočo masovzorcev pa se je zmanjševala. Predpostavljeno je bilo, da lahko sorbcijskeprocese, povezane z lesom, vrednotimo kot sisteme prvega reda. Značilna časovna konstanta ? določa časovno odvisnost sorbcijskega procesa za relevantno sorptivno območje lesnega tkiva v celoti in enolično. Zveza med časovno konstanto in debelino vzorca, merjeno v smeri snovnega toka, je potenčna, pri čemer je vrednost potence odvisna zgolj od razmerja med zunanjimprestopnostnim in notranjim difuzijskim uporom. Za določitev omenjenihuporov oziroma koeficientov snovne prestopnosti in difuzivnosti je treba napraviti eksperiment na vzorcih različnih debelin. Samo tako je mogoče korektno ločiti zunanji prestopnostni in notranji difuzijski upor. wood sorption first order system time constant mass transfer diffusivity sorpcija lesa sistem rpvega reda časovna konstanta masna prestopnost difuzivnost true false true Angleški jezik Ni določen Znanstveno delo 2017-07-12 09:18:59 2017-07-12 09:18:59 2022-08-12 14:12:55 0000-00-00 00:00:00 2007 0 0 str. 17-21 Vol. 84 2007 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 630*81(045)=111 0351-3114 URN:NBN:SI:doc-RHJC1AJV 2125222 6206978 RAZ_Bucar_Bojan_i2007.pdf RAZ_Bucar_Bojan_i2007.pdf 1 98AB9413E762DB9402A84C94DD286399 e92fd5c69e41a064d947b04424849f950f33592033cb5c93f3d041a4b909e3a2 22dd856b-17b5-11ed-b6b8-001a4af901a5 20.500.12556/dirros/a7c4725a-fffa-4808-8795-40527f28c772 https://dirros.openscience.si/Dokument.php?lang=slv&id=9553 Gozdarski inštitut Slovenije Acta Silvae et Ligni 0 0 0