تعيين منحني هاي همدما و سينتيك جذب و دفع رطوبت يونجه

چكيده انگليسي :

Determination of Isotherm Curves and Sorption and Desorption Moisture Kinetic of Alfalfa Mohsen Ghasemi Info ghasemi@yahoo com April 28 2010 Department of Farm Machinery Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors A A Masoumi masoumi@cc iut ac ir and M sadeghi sadeghimor@cc iut ac ir Abstract Alfalfa Medicago Sativa is the queen of forage plants Leaves contain two third of the protein and 75 percent of the total digestible nutrients TDN in alfalfa hay Harvesting the maximum amount of the leaves is a profitable way to produce alfalfa hay To prevent losses particularly the leaves during alfalfa baling under high temperature and low relative humidity conditions it seems rewetting moved and dried alfalfa rows could increase moisture content and hence reduces the losses in alfalfa baling The objective of this research was to obtain adsorption and desorption characteristics of alfalfa leaves and stems The adsorption and desorption moisture content of alfalfa leaves and stems were determined using the dynamic gravimetric method Determination was made within a range of water activity of 0 11 to 0 84 It is necessary to use at least three temperatures for the safety of the estimations based on the experimental results These experiments were conducted at three different temperatures of 30 40 and 50 C Seven saturated salts used to provide relative humilities Data from the experiments were analyzed using non linear regression techniques in Microsoft Excel software The SAS and MSTATC softwares were used for data analysis In this study the effects of relative humidity and temperature on sorption and desorption equilibrium moisture content EMC of the alfalfa components leaves and stems were investigated The experiments were conducted using split plot experiment using a completely randomized design with three replications The mean comparison was performed using least significant difference LSD Several theoretical semi theoretical and empirical models have been proposed and used by researchers for fitting EMC data Four mathematical models consisting of Oswin Halsey Henderson and Chung pfost were used to fit the experimental data All the models were compared according to three statistical parameters i e adjusted R square R2 standard error of the estimates SEE and mean relative error MRE For selection of the best of four models the model with the least SEE and MRE and the highest R2 were chosen Results indicated that the effect of relative humidity temperature and alfalfa components as well as their interactions on sorption and desorption equilibrium moisture content were significant P 0 01 The isotherm curves were sigmoid in shape which conformed to type II classification characteristic of most biological tissues The sorption and desorption capacity of the leaves and stems decreased with an increase in temperature at constant relative humidity The hystersis effect was not distinctly observed in the range of temperature tested The Halsey equation was found to be a good model for moisture sorption of leaves and stems at 30 and 40 C while the Chung pfost model was a good one for moisture sorption of the leaves and stems at 50 C The Halsey model was a good model for desorption of leaves at three temperatures and for stems at 30 C and 40 C However the Henderson model was a good model for moisture desorption of stems at 50 C Keywords Alfalfa equilibrium moisture content relative humidity adsorption desorption isotherm curve

قاسمي، محسن

تعيين منحني هاي همدما و سينتيك جذب و دفع رطوبت يونجه

محتواي رطوبت تعادلي , رطوبت نسبي , منحني همدما