Net Isosteric Heat Research Articles

Optimization of the drying of <i>Moringa oleifera</i> leaves by determination of thermophysical parameters

Moringa oleifera leaves are increasingly used as a dietary supplement. The present study deals with the estimation of its thermophysical properties. It is based on the Clausius-Clayperon and Gibbs-Helmholtz equations. This study required knowledge of the sorption isotherms obtained by the static gravimetric method in the relative humidity range of 5.4 to 97% and the temperatures of 30, 35, 45 and 55 °C. The BET models (1938), Smith (1947), Henderson (1952), Iglesias (1981) and GAB (1985) are used for the smoothing of the experimental points. The isotherms obtained are of type II and characterized by a sigmoid shape. The theoretical curves of GAB and Smith show a better similarity with the experimental curves. The monolayer moisture content (Xm) is 8.54/7.62% at 30 °C; 7.0/5.52% at 35 °C; 6.74/ 5.41% at 45 °C and 5.45/4.65% at 55°C respectively for the GAB and BET models. The net isosteric heat ( qst ) and desorption differential entropy ( ΔS ) tend towards zero for very high moisture contents. The activation energy of desorption of the Moringa oleifera leaves in the temperature range tested is -13.1010 kJ/mol. Isokinetic temperature ( Tβ ) and the average harmonic temperature ( Thm ) are respectively 314.172 K and 314.459 K while the free energy ( ΔGβ ) is 308.18 J/mole. © 2017 International Formulae Group. All rights reserved. Keywords: Desorption isotherm, Modelization, Isosteric heat, Differential Entropy, Activation energy

Effect of anti-caking agents on moisture sorption isotherms of palmyra-palm jaggery granules

Jaggery granules, prepared from palmyra-palm syrup, were mixed with five levels (0.5 to 2 %w/w) of anti-caking agents [tri calcium phosphate, (TCP) or corn starch (CS)] and their moisture sorption isotherms were determined without or with addition of anticaking agents by the static equilibrium method using saturated salt solutions at four temperatures of 25, 35 and 45°C. The moisture sorption isotherms for this granular jaggery samples are Type-III isotherms and the effect of temperature on equilibrium moisture content (EMC) values upto a water activity values of 0.3 to 0.5 show no significant effect. Among two moisture sorption isotherms (MSI) models tested with the experimental data for this high sugar food, GAB model was found to be the best fit followed by Iglesias and Chirife model. The monolayer moisture content (M 0 ) of the granular jaggery samples varied from a minimum of 4.195% (d.b.) for the granulated jaggery without anticaking agent at 45°C to a maximum of 7.303% (d.b.) for granulated jaggery with TCP and 9.178% (d.b.) for granulated jaggery with corn starch @ 2.0% at a temperature of 25°C. A decreasing trend for both Mo and C values but increasing trend for K was obtained with the increase in temperature. The monolayer moisture content of jaggery granules with addition of TCP or CS has been found to posses good correlation with temperature. The net isosteric heat of sorption (q st ) of jaggery granules without addition of anti-caking agents, decreased exponentially from 29.132 to 4.833 kJ mol -1 with the increase in moisture content from 2.5 to 15% (d.b.). It was also observed that, net isosteric heat of sorption was found to be higher for the jaggery granules without addition of anti-caking agents as compared to samples with addition of anti-caking agents.

Isosteric heat of water adsorption and desorption in homoionic alkaline-earth montmorillonites

The aim of the present work is to study by means of thermodynamic measurements and Infrared spectroscopy, the effect of the interlayer cations on the adsorption–desorption of water in the case of a montmorillonite exchanged with alkaline-earth metals. For the first time, the net isosteric heat of water adsorption and desorption is determined from isotherms recorded at three temperatures. The net isosteric heat is a very useful parameter for getting more insights into the sorption mechanism since it provides information about the sorption energy evolution which can be complementary to that obtained from structural or gravimetric measurements. The homoionic montmorillonite samples are prepared from purification and cationic exchanged in aqueous solution of the raw material, i.e. the reference SWy-2 Wyoming material. XRD at the dry state and elemental chemical analysis confirm that the treatment does not deteriorate the clay structure and yield the expected homoionic composition. The sorption isotherms measured at various temperatures show that the nature of the interlayer, i.e. exchangeable, cation changes the adsorbed/desorbed amount of water molecules for a given water relative pressure. The total amount of water adsorbed at PP∘ = 0.5 follows the cation sequence Ca ∼ Mg>Ba while the sorption isosteric heats follow a slightly different sequence, i.e. Ca > Mg>Ba. This discrepancy between the adsorption and desorption heat is due to the higher irreversibility of water sorption process in the Ca exchanged montmorillonite. Finally, analysis of the IR spectra recorded at room temperature and under a primary vacuum reveals that the amount of adsorbed water follows the same sequence as that of the isosteric heat of adsorption and shows the coexistence of liquid-like and solid-like water confined in the interlayer space.

Moisture sorption isotherms and thermodynamic properties of bovine leather

This study was aimed at the determination of bovine leather moisture sorption characteristics using a static gravimetric method at 30, 40, 50, 60 and 70 °C. The curves exhibit type II behaviour according to the BET classification. The sorption isotherms fitting by seven equations shows that GAB model is able to reproduce the equilibrium moisture content evolution with water activity for moisture range varying from 0.02 to 0.83 kg/kg d.b (0.9898 < R2 < 0.999). The sorption isotherms exhibit hysteresis effect. Additionally, sorption isotherms data were used to determine the thermodynamic properties such as isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy. Net isosteric heat of sorption and differential entropy were evaluated through direct use of moisture isotherms by applying the Clausius–Clapeyron equation and used to investigate the enthalpy-entropy compensation theory. Both sorption enthalpy and entropy for desorption increase to a maximum with increasing moisture content, and then decrease sharply with rising moisture content. Adsorption enthalpy decreases with increasing moisture content. Whereas, adsorption entropy increases smoothly with increasing moisture content to a maximum of 6.29 J/K.mol. Spreading pressure increases with rising water activity. The net integral enthalpy seemed to decrease and then increase to become asymptotic. The net integral entropy decreased with moisture content increase.

A new method to determine the water activity and the net isosteric heats of sorption for low moisture foods at elevated temperatures

In recent years, research studies have shown that the thermal resistance of foodborne pathogens in the low moisture foods is greatly influenced by the water activity (aw) at temperatures relevant to thermal treatments for pathogen control. Yet, there has been a lack of an effective method for accurate measurement of aw at those temperatures. Thus, the main aim of this study was to evaluate a new method for measuring aw of food samples at elevated temperatures. An improved thermal cell with a relative humidity and temperature sensor was used to measure the aw of the three different food samples, namely, organic wheat flour, almond flour, and non-fat milk powder, over the temperature range between 20 and 80°C. For a constant moisture content, the aw data was used to estimate the net isosteric heat of sorption (qst). The qst values were then used in the Clausius Clapeyron equation (CCE) equation to estimate the moisture sorption isotherm for all test food samples at different temperatures. For all the tested samples of any fixed moisture content, aw value generally increased with the temperature. The energy for sorption decreased with increasing moisture content. With the experimentally determined qst value, CCE describes well about the changes in aw of the food samples between 20 and 80°C. This study presents a method to obtain aw of a food sample for a specific moisture content at different temperatures which could be extended to obtain qst values for different moisture contents and hence, the moisture sorption isotherm of a food sample at different temperatures.

Kinetics of water vapor adsorption by vacuum-dried jujube powder

Water vapor adsorption kinetics of vacuum-dried jujube powder were investigated in temperature and relative humidity ranges of 10 to 40℃ and 32 to 75%, respectively. Water vapor was initially adsorbed rapidly and then reached equilibrium condition slowly. Reaction rate constant for water vapor adsorption of vacuum-dried jujube powder increased with an increase in temperature. The temperature dependency of water activity followed the Clausius-Clapeyron equation. The net isosteric heat of sorption increased with an increase in water activity. Good straight lines were obtained with plotting of 1/(m-m0) vs. 1/t. It was found that water vapor adsorption kinetics of vacuum-dried jujube powder was accurately described by a simple empirical model, and temperature dependency of the reaction rate constant followed the Arrhenius-type equation. The activation energy ranged from 50.90 to 56.00 kJ/mol depending on relative humidity. Arrhenius kinetic parameters (Ea and k0) for water vapor adsorption by vacuum-dried jujube powder showed an effect between the parameters with the isokinetic temperature of 302.51 K. The information on water vapor adsorption kinetics of vacuum-dried jujube powder can be used to establish the optimum condition for storage and processing of jujube.

Moisture sorption isotherm of microencapsulated extra virgin olive oil by spray drying

Adsorption isotherms, at 4, 25 and 60 °C for microencapsulated extra virgin olive oil powder (MEVOP) prepared by rotor–stator homogenization (RSH) and ultrasonic homogenization (UH) methods before spray drying, were obtained using standard static gravimetric method. The sorption isotherms exhibited type III (J shape) behaviour. The sorption isotherms of MEVOP depended on temperature, chemical composition of particle surface and particle size of samples. The equilibrium moisture contents (EMC) decreased with increasing temperature. The sorption isotherm of MEVOP obtained with UH shifted up compared to that obtained with RSH because of the smaller particle size of MEVOP obtained with UH. The Guggenheim–Anderson–de Boer (GAB) model was the best fitting the experimental sorption data. Monolayer moisture contents of MEVOP were in the range of 0.036–0.079 kg H2O per kg d.s. All K values of MEVOP were higher than 0.89. C values of MEVOP obtained with RSH and UH method varied in range of 7.17–13.86 and 8.42–27.76, respectively. Net isosteric heat of sorption was evaluated using the Clausius–Clapeyron equation and differential entropy decreased with increasing moisture content. Gibbs-free energy decreased with increasing equilibrium moisture content. The spreading pressure increased with the rise in water activity for all temperatures.

Moisture sorption isotherm characteristics and Taguchi analysis of rice bran extraction parameters

AbstractThis work determined the moisture sorption isotherm of rice bran and investigated the effects of the pre‐treatment method, solvent type, solid–liquid ratio and soaping temperature on extract yield, total phenolic content, 2,2‐diphenyl‐1‐picrylhydrazyl radical‐scavenging activity assay and 2,2′‐azino‐bis antioxidant capacity assay of rice bran extract. The Taguchi method and L9 (34) orthogonal array were employed in this study. The sorption isotherms of rice bran showed a sigmoidal pattern and displayed type II of van der Waals adsorption. Adsorption and desorption data on rice bran were best fitted using the Henderson model among the six models tested at three temperatures. The net isosteric heat of desorption was higher than the net isosteric heat of adsorption. Based on the analysis of the signal‐to‐noise ratio, solvent selection effected the largest contribution to the overall performance. Confirmation experiments showed that the optimal combination that contained the four quality attributes was appropriate (error margin &lt;5%) and reproducible. © 2016 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Sorption behavior, thermodynamic properties and storage stability of ready-to-eat Elephant Foot Yam (Amorphophallus spp.) product: physic-chemical properties, minerals, total dietary fiber and phenolic content of stored product

The effect of osmotic dehydration in sucrose solution followed by convective dehydration on sorption isotherms and storage stability of elephant foot yam was evaluated in the present work. The equilibrium moisture content of un-treated (Hot-air-dried) and pre-treated (Osmo-air-dried) samples were determined by static gravimetric method at different temperatures (20, 30, 40, and 50 °C) and relative humidities (11–90 %). The curves obtained for sorption can be considered as type-II according to Brunauer–Emmett–Teller (BET) classification. The higher values of net-isosteric heat of sorption and heat of vaporization was observed for un-treated samples. i.e. 6.82–14.79 and 2978.28–3548.68 kJ/kmol as compared to pre-treated samples. i.e. 6.72–14.09 and 2858.33–3315.85 kJ/kmol, respectively and decreased with increase in moisture content. The experimental data revealed that enthalpy–entropy compensation theory was satisfactorily applicable to the moisture sorption behavior of the un-treated and pre-treated EFY samples. Mineral contents of fresh EFY product viz. magnesium, potassium and calcium were 190 ± 1.0, 515 ± 2.5 and 214 ± 2.08 mg/100g, respectively. After 6 months of storage change in minerals was not significant, whereas significant increase in dietary fiber (15.95 ± 0.76−19.68 ± 0.45 g/100g) and slight but significant reduction in phenolic content (49.97 ± 0.76–46.81 ± 0.60 mgGAE/g extract) was observed.

Moisture Sorption Isotherm of Underutilized Culinary Banana Flour and Its Antioxidant Stability during Storage

The moisture sorption isotherm of vacuum dried culinary banana flour was studied using standard static-gravimetric technique at five different temperatures (25–45C). There was a gradual increase in equilibrium moisture content (EMC) between 0.1 and 0.65 water activities (aw), and EMC increased beyond 0.65 aw led to type II isotherm of sigmoidal characteristics. The effect of temperature on EMC was not significant at P > 0.05. Among the seven models fitted, Peleg model showed the highest coefficient of determination (R2) with lower values of relative deviations (Rd < 10%) and fulfilled the necessary criteria desired for the model and best fitted. The net isosteric heat of sorption (qst) determined from the equilibrium sorption data using Clausius–Clapeyron equation showed the decreasing trend of qst with increasing EMC. Additionally, the antioxidant and polyphenols stability of culinary banana flour monitored at 25C showed minor degradation up to 120 days without affecting its bioactive properties. Practical Applications The nutritionally rich culinary banana (kachkal) of Assam, India having immense regional importance is yet to gain much attention and fall under the category of underutilized crop. We focused to utilize this underutilized crop for the benefit of society in terms of nutrients, functionality and healthy diet. The sorption isotherms of culinary banana flour obtained in the present study could provide essential information on designing, optimization and prediction of drying processes, storage conditions and selecting appropriate packaging materials. This study will be useful for low moisture food industry where culinary banana could promote as high value-added flour.

Effect of Sodium and Its Substitution with Potassium on Desorption and Thermodynamic Properties of Cheddar Cheese

Desorption isotherm of full sodium Cheddar cheese (FSCC) and low sodium Cheddar cheese (LSCC) was obtained at 5C and 10C using a static gravimetric method. Both cheeses desorption isotherms show Type II of the five general types of sorption isotherms due to the presence of casein as a major constituent and also due to the presence of salts. Desorption curves in both cases indicate that increase in temperature results in decrease in equilibrium moisture content. Several models were tested of which BET and GAB model were best fitted to the experimental data in the water activity range of 0.11–0.98. The porosity of FSCC and LSCC showed general increasing trend with increase in temperature and moisture content. Net isosteric heat of desorption was evaluated by Clausius–Clapeyron equations to provide an understanding of the properties of water and energy requirements associated with the desorption behavior. Practical Applications The results may be utilized for predicting water activity values of low sodium Cheddar cheese (LSCC) at different temperature and moisture content. Properties calculated viz., equilibrium moisture content, monolayer moisture content, and many others may find application in representing the state of water present in LSCC at different temperatures for revealing physico-chemical and microbiological changes.

Thermodynamic properties of the water sorption isotherms of wood of limba (Terminalia superba Engl. & Diels), obeche (Triplochiton scleroxylon K. Schum.), radiata pine (Pinus radiata D. Don) and chestnut (Castanea sativa Mill.)

The sorption isotherms of limba (Terminalia superba Engl. & Diels), obeche (Triplochiton scleroxylon K. Schum.), radiata pine (Pinus radiata D. Don) and chestnut (Castanea sativa Mill.), were plotted at 15°C, 35°C and 50°C. The curves were fitted using the Guggenheim-Anderson-de Boer (GAB) model. The thermodynamic properties (net isosteric heat of sorption, total heat of wetting, differential entropy and spreading pressure) were determined from the isotherms to define the energy associated with the sorption processes. Net isosteric heat of sorption was obtained using the Clausius-Clapeyron equation and showed a negative relation with moisture content. Differential entropy showed the same behaviour. These two parameters were higher in desorption than in adsorption. Total heat of wetting was also higher in desorption than in adsorption and higher in chestnut than in the other species. The enthalpy-entropy theory was validated as there was a good linear fit between net isosteric heat of sorption and differential entropy, and the isokinetic temperatures were different from the harmonic mean temperature. Using the enthalpy-entropy theory, it was possible to conclude that the adsorption and desorption processes were enthalpy driven and spontaneous. Spreading pressure increased as water activity increased. The variation of spreading pressure with temperature depends on the species type.

Water Sorption Isotherms and Air Drying Kinetics ofFucus vesiculosusBrown Seaweed

Water sorption isotherms at 5, 25, 45 and 65C and air drying kinetics at 35, 50, 60 and 75C of Fucus vesiculosus seaweed were determined. Water desorption and adsorption isotherms were modeled using Halsey model. Monolayer moisture content, evaluated by means of BET model, decreased with increasing temperature. Thermodynamic properties (net isosteric heat, net equilibrium heat, differential and integral entropy) were also evaluated. Page model was used to fit seaweed drying kinetics in deep bed configuration. Seaweed mainly shrank at high moisture content during the induction and constant drying rate periods. The critical moisture content rose linearly with drying temperature (from 1.8 to 2.5 kg water (d.b.)−1). Diffusional model, assuming semi-infinite cylinder geometry, was employed for the drying kinetics modeling during the falling drying rate period for thin layer configuration. The corresponding effective coefficients of water diffusion rose with increasing temperature from 1.0 up to 2.8 × 10−10 m2/s. Practical Applications Fucus vesiculosus is a seasonal and edible brown seaweed with different food and nonfood uses. In the next years, it is expected due to its phytochemical properties that the consumption will increase strongly. It is a perishable product due to its high water activity and solar drying is the most common method of preservation. However, important losses of material and poor quality of dried seaweed are usually found. The use of a tray dryer with controlled conditions can be a good alternative to explore for this seaweed. The evaluation of water sorption isotherms allows the determination of optimal moisture content for seaweed preservation and thermal properties useful for dryer design. Experimental drying kinetics employing warm air and modeling using empirical and theoretical equations are useful to establish appropriate drying operation conditions and to understand the water transfer mechanisms from seaweed to air.

Thermodynamic properties of moisture adsorption in tef (eragrostis tef) seed

The moisture adsorption isotherms of tef (Eragrostis tef) seeds were studied under temperature and relative humidity ranges of 10–40 °C and 15–90%, respectively. The equilibrium moisture content (EMC) decreased with increase in temperature and increased with increase in relative humidity significantly (p < 0.05). The adsorption isotherms exhibited sigmoid shape (type II) which is common for most biological and food materials. The GAB and Peleg models best described the moisture adsorption characteristics of tef seeds resulting in high R2 (0.99), low mean relative percentage deviation, E (<5%) and Root Mean Square Error (RMSE) values with random distribution of residuals. The thermodynamic properties determined in this study were net isosteric heat, differential entropy, spreading pressure, net integral enthalpy and net integral entropy. The net isosteric heats and the differential entropy decreased exponentially with increase in moisture content. The spreading pressure increased with increase in water activity. The net integral enthalpy decreased with increase in moisture content whereas the net integral entropy increased with increase in moisture content and remained negative in value.

Comparative moisture sorption isotherms, modelling and isosteric heat of sorption of controlled and irradiated Moroccan rosemary leaves

In this paper, we studied and compared water sorption isotherms of irradiated and non-irradiated (controlled) rosemary leaves at three temperatures: 30, 40 and 50°C, using the standard static gravimetric method. This method consists on the use of different salts solutions, over a range of water activity from 0.05 to 0.9.The sorption isotherms of all samples were conceived to be typical type II sigmoid. These isotherms have been fitted using four different sorption equations (modified Oswin, Enderby, Peleg, and LESPAM), Enderby model was proved to be the most suitable for describing the sorption curves for controlled and irradiated rosemary leaves.The experimental data curves allows us to calculate the value of the optimal water activity as for the conservation of controlled and irradiated rosemary leaves.Respectively, the net isosteric heat of sorption of our samples was computed from the predicted sorption data by applying the integrated form of the Clausius–Clapeyron equation.

Moisture Sorption Characteristics of Dehydrated Watermelon (Citrullus lanatusThunb)Pomace Wastes

The moisture adsorption isotherms of watermelon pomace (“Namdhari” and “Sugar baby”) dehydrated in fluidized bed and cabinet dryer were obtained over a range of water activities and temperature varying from 0.113 to 0.920 at 20–50C, respectively. The adsorption power of dehydrated watermelon pomace waste decreased with increase in temperature at constant water activity. The moisture sorption isotherms of DWPW were sigmoid in nature. Chung and Pfost was the most efficient model among Type I models for both cultivars with coefficient of determination (R2) of 0.973–0.990, standard error (SE) of 0.082–0.096 and scattered residual plots. Among Type II models, Modified Henderson model gave best results with R2 of 0.967–0.982, SE of 0.167–0.234 and scattered residual plots. The variation of net isosteric heat of sorption for DWPW of both cultivars, estimated using the Clausius-Clapeyron equation, was 41.69–0.2 kJ/mol at 3–30% moisture content on dry basis. Practical Applications Watermelon pomace was discarded as waste, which can be used to obtain bioactive compounds. Dehydration is better alternative to increase the shelf life of pomace. The storage life of pomace was dependent on storage temperature and relative humidity (RH). Mathematical modeling was applied to study the moisture adsorption isotherm of watermelon pomace.

Moisture sorption isotherm characteristics of Hemerocallis Fulva and Cymbopogon

AbstractThe moisture sorption isotherms of Hemerocallis Fulva and Cymbopogon are measured by the static gravimetric method at 25, 35, and 45 °C over a water activity range of 0.09 to 0.95 using standard saturated salt solutions. The sorption isotherms of H. fulva and Cymbopogon display type III (J‐shaped) and type II (nearly sigmoid shapes) isotherms. In addition, the adsorption and desorption data of H. fulva and Cymbopogon fit well with the White &amp; Eiring model and the Oswin model, respectively. The Brunauer–Emmett–Teller equation is applied to determine the monolayer moisture content, and the surface area of a monolayer was calculated. The values of the net isosteric heat of sorption are found to increase with decreases in the equilibrium moisture content. Moreover, the net isosteric heat of desorption is higher than that of the adsorption heat. Copyright © 2016 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Spray drying bioactive orange-peel extracts produced by Soxhlet extraction: Use of WPI, antioxidant activity and moisture sorption isotherms

Spray drying of orange peel extracts was performed using a laboratory-scale spray dryer in order to assess the best operating conditions to be used in a subsequent scale-up process. Addition of whey protein isolate (WPI) to the liquid feed enhanced the yield of the process significantly from 30 ± 10% to 63 ± 3%. The moisture sorption isotherms of the powders were also determined at 30 °C, 40 °C and 50 °C and fitted by the Guggenheim-Andersen-de Boer (GAB) equation. The average net isosteric heat of sorption for the powders was determined using the Clausius–Clapeyron equation to be 70.5 kJ/kg. The total phenolic content (TPC) and the free radical scavenging capacity (SC50) of the powders were retained by 95 ± 5% and 95 ± 15%, respectively, during small-scale spray drying at an inlet air temperature of 150 °C and a corresponding outlet temperature of 70 ± 3 °C. Therefore, the best operating conditions for scale-up were suggested to be an inlet air temperature of 150 °C, a maximum allowable outlet temperature of 80 °C and a maximum allowable relative humidity for the exhaust air of 15%, while using a liquid feed containing 7.5% (w/w), dry basis WPI.

Water sorption behaviour of by-products from the rice industry

The adsorption and desorption isotherms of rice flour made from by-products from the rice industry and isolated starch were determined at different temperatures (25, 35, 45 and 55°C) using a static gravimetric method. Several saturated salt solutions were selected to generate different water activities over a range of 0.09–0.91. The obtained isotherms for all systems were of Type II following the BET classification. The observed hysteresis cycles were of Type H3 for all tested systems according IUPAC classification. GAB (R2>0.993, ERMS<3.9%) and Chung-Pfost (R2>0.992, ERMS<3.9%) models nicely fitted all experimental isotherms. The net isosteric sorption heat, calculated by means of Clausius–Clapeyron equation, decreased when moisture content increased. The maximum values of net isosteric sorption heat (kilojoules per mole) were approximately 51 and 58 for rice flour and 34 and 42 for rice starch, for adsorption and desorption processes, respectively, in the range of temperature from 25°C to 55°C.

Triphasic Model of Heat and Moisture Transport with Internal Mass Exchange in Paperboard

Mixture theory is used to derive a triphasic model to describe processes in paperboard consisting of solid fiber, bound water and gas. The gas is viewed as a miscible mix of the two constituents dry air and water vapor. The governing equations are mass conservation laws for bound water, dry air, water vapor, and mixture energy balance. Constitutive relations are found by exploiting the macroscale dissipation inequality. Resulting constitutive equations include Fickian diffusion of water vapor and dry air, Darcian flow for gas and Fourier heat conduction for the mixture. Mass exchange between bound water, and water vapor due to adsorption/desorption is driven by the difference in chemical potential. The interaction function is based on equilibrium considerations for the bound water–water vapor system. From the description of the sorption isotherm, expressions for net isosteric heat and free energy related to water–fiber interaction are derived. The resulting thermodynamically consistent model is used to simulate moisture and heat dynamics for paperboard rolls. Simulation results are presented for a paperboard roll with anisotropic material properties subjected to a change in ambient relative humidity from 50 to 80 %.