W pracy, do oceny czystości powierzchni, zastosowano dwie metody

Mass;Masa [g]Moisture vaporization;Odparowanie wilgoci [kgm -2 s -1 ]Temperature;Temperatura [°C]Gulnara GRDZELISHVILI, Pavel HOFFMANFig. 8. The rate of moisture vaporization by calculation and by experimental dataRys. 8. Szybkość parowania wilgoci uzyskana na podstawie danych teoretycznychi danych doświadczalnychExperimental data are particularly given in nomenclature andpart of them is presented in table 1 and on figure 9 and 10.Table 1. Some experimental data and the deviations of moisture vaporizationTabela 1. Dane doświadczalne i odchylenia parowania wilgociTm=(Tm1+ Tm2)/2 (K) Δ Tm= Tm– Ta0 301 0 –10 312.6 11.6 11.9320 318 17 7.4230 321.25 20.25 0.1840 324.23 23.23 10.9450 328.1 27.1 13.7760 331.8 30.8 21.1170 336 35 25.3780 340.1 39.1 19.0290 344.5 43.5 19.05100 350.3 49.3 8.93The average rate of moisture vaporization n w ex (kgm –2 s –1 )was defined for every 10 minutes sections from 6 to 105minutes of IR drying experiment, that data are shown byfigure 9.The changes of sample diameter D and thickness H wasdetermined experimentally too.4,03,53,02,52,01,51,00,50,00,00070,00060,00050,00040,00030,00020,00010by experimental databy calculation0 20 40 60 80 100 120Time [min];Czas [min]0 20 40 60 80 100 120Time [min];Czas [min]Fig. 9. Drying curve of an apple sample with the initial weight 3.7 g and thefinal moisture content 17.1%pobrano z www.ips.wm.tu.koszalin.plRys. 9. Krzywa suszenia próbki jabłka z początkową masą 3,7 g i końcowąwilgotnością rzędu 17,1%9080706050403020100Fig. 10. Average material temperatures and temperature differences betweenair and materialRys. 10. Średnie temperatury materiału i różnice temperatur pomiędzypowietrzem i materiałemThe deviations of the calculated average rate of moisturevaporization from the experimentally determined averagerate of moisture vaporization were established accordingto the equation 7 and are presented in table 1.The deviation of the calculated average rate of moisturevaporization from the experimentally determined averagerate according to equation 7 is shown in table 1. Certaindeviation of the calculated data (defined by equation 5)from the experimental ones (defined by equation 6) couldbe explained by the complexity of determining the exactvalues of the radiation density of the IR lamp (due to unevendistribution of the radiation on the irradiated surface),of the absorptivity and of the samples sizes (because theyare constantly changeable). Therefore in all cases it is betterto calculate the rate of moisture vaporization in successivelysmall sections of drying.Conclusions0 20 40 60 80 100 120Time [min];Czas [min]The infrared–convective drying of apple slices is quite effective.The test of the effect of blanching confirms that the dryingtime of blanched apple slices is much shorter than forunblanched raw materials slices. Decrease of air velocity reducesthe drying time. The lower air temperature makes theduration of drying longer.The rehydration ratio was found higher for blanched driedsamples. The maximum of water uptake ability was 3.96 forblanched apple samples and it was equal to 3.46 forunblanched dried slices on the average. The lower final moisturecontent influenced the faster restoration at the beginningof rehydration process.Results of calculation of the rate of moisture vaporizationseem to be in a reasonable agreement with experimental data.AcknowledgementsWe wish to thank for the support from grant SGS2012 at ČVUTin Prague (SGS12/057/OHK2/1T/12) and the research programMŠMT ČR (6840770035), which enabled us to make anexperimental verification the drying hypothesis.t mΔT16 Inżynieria Przetwórstwa Spożywczego 1/4–2013(5)