Dehydration of Red Beet Root (Beta vulgaris) by Hot Air Drying: Process Optimization and Mathematical Modeling

S. V. Gokhale,S. S. Lele 한국식품과학회 2011 Food Science and Biotechnology Vol.20 No.4

Convective hot air drying was optimized with the objective of maximum color retention of red beet. The process was mathematically modelled as a function of hot air temperature, batch time, and moisture. New semitheoretical model was tested with experimental data (50 to 120^oC) and was found better than 9 other reported models. Estimated effective moisture diffusivity was 3.01×10^−9 to 7.21×10^−7 m^2/s and it obeyed Arrhenius’s equation. Color and rehydration ratio were used to assess the quality of beet powder. An unusual trend of color minima was also observed;which was attributed to the physical phenomena of surface moisture. The final color of beet was temperature dependent and maximum color retention was achieved at lowest drying temperature. Best drying condition required sequential reduction in temperature (120 to 50ºC) resulting in good color retention. This reduced batch time to 4 h compared to 6 h batch of conventional isothermal drying at 50ºC.

온도에 따른 암석시편의 건조무게 특이점 분석

김석주 한국지반환경공학회 2023 한국지반환경공학회논문집 Vol.24 No.9

The Korean Industrial Standards (KS F) have a various regulations for measuring the weight of dried soil and rock. However, if the dried weight is measured in air after drying at 110±5°C or 105±5°C, a weight singularity occurs, in which the weight decreases and then increases as the measurement time continues. In this study, basaltic rock from Ulleung Island was oven dried at 40 to 110°C. The weight was measured on an electronic scale with a sensitivity of 0.0001g (0.1mg) to find weight singularities. A method to easily determine the dry weight using the weight singularities was presented. As a result of analyses of the singularity of rock specimen according to temperature, the singularities were appeared in the temperature range of 40 to 110°C, and the weight of the singularity was smaller as the heating temperature increased. In particular, the weight singularity duration appeared, and the duration of the singularity was shorter as the heating temperature increased. The results of the convection measurement experiment showed that the cause of the singularity is the convection phenomenon caused by the contact of the heated rock with the air. The weight decrease of oven dried rock occurs when the effect of convection is dominant over the effect of air moisture absorption. Conversely, the weight increase of rock occurs when the effect of air moisture absorption is dominant over the effect of convection. 한국산업표준(KS F)에는 건조된 흙과 암석의 무게를 측정하는 다양한 규정들이 있다. 그러나, 110±5°C 또는 105±5°C로 건조 후 공기 중에서 건조무게를 측정하면 측정시간이 지속됨에 따라 무게가 감소 후 증가하는 무게 특이점이 나타난다. 본 연구에서는 울릉도 현무암질 암석을 40~110°C로 노건조 하였고, 0.0001g(0.1mg) 감도의 전자저울에 무게를 측정하여 무게 특이점을 찾았고, 나타난 무게 특이점을 이용하여 건조무게를 쉽게 결정할 수 있는 방법을 제시하였다. 온도에 따른 암석시편의 특이점을 다양하게 분석한 결과, 특이점은 40~110°C의 온도구간에서 모두 나타났고 가열온도가 높을수록 특이점의 무게가 작게 나타났다. 특별히, 무게 특이점이 지속되는 현상이 나타났고, 가열온도가 높을수록 특이점의 지속시간이 짧게 나타났다. 대류측정 실험의 결과에 의하면 특이점의 발생 원인은 가열된 암석이 공기와의 접촉에 의해 발생된 대류현상이 원인이라는 것을 알 수 있었다. 노건조된 암석의 무게 감소는 대류발생으로 인한 영향이 공기 중 수분 흡수의 영향보다 우세할 때 발생된다. 반대로 암석의 무게 증가는 공기 중 수분 흡수의 영향이 대류발생으로 인한 영향보다 우세할 때 발생된다.

NATURAL CONVECTION HEAT TRANSFER CHARACTERISTICS IN A CANISTER WITH HORIZONTAL INSTALLATION OF DUAL PURPOSE CASK FOR SPENT NUCLEAR FUEL

Lee, Dong-Gyu,Park, Jea-Ho,Lee, Yong-Hoon,Baeg, Chang-Yeal,Kim, Hyung-Jin Korean Nuclear Society 2013 Nuclear Engineering and Technology Vol.45 No.7

A full-sized model for the horizontally oriented metal cask containing 21 spent fuel assemblies has been considered to evaluate the internal natural convection behavior within a dry shield canister (DSC) filled with helium as a working fluid. A variety of two-dimensional CFD numerical investigations using a turbulent model have been performed to evaluate the heat transfer characteristics and the velocity distribution of natural convection inside the canister. The present numerical solutions for a range of Rayleigh number values ($3{\times}10^6{\sim}3{\times}10^7$) and a working fluid of air are further validated by comparing with the experimental data from previous work, and they agreed well with the experimental results. The predicted temperature field has indicated that the peak temperature is located in the second basket from the top along the vertical center line by effects of the natural convection. As the Rayleigh number increases, the convective heat transfer is dominant and the heat transfer due to the local circulation becomes stronger. The heat transfer characteristics show that the Nusselt numbers corresponding to $1.5{\times}10^6$ < Ra < $1.0{\times}10^7$ are proportional to 0.5 power of the Rayleigh number, while the Nusselt numbers for $1.0{\times}10^7$ < Ra < $8.0{\times}10^7$ are proportional to 0.27 power of the Rayleigh number. These results agreed well with the trends of the experimental data for Ra > $1.0{\times}10^7$.

Natural Convection Heat Transfer Characteristics in a Canister with Horizontal Installation of Dual Purpose Cask for Spent Nuclear Fuel

이동규,박제호,이용훈,백창열,김형진 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.7

A full-sized model for the horizontally oriented metal cask containing 21 spent fuel assemblies has been considered toevaluate the internal natural convection behavior within a dry shield canister (DSC) filled with helium as a working fluid. Avariety of two-dimensional CFD numerical investigations using a turbulent model have been performed to evaluate the heattransfer characteristics and the velocity distribution of natural convection inside the canister. The present numerical solutionsfor a range of Rayleigh number values (3×106~3×107) and a working fluid of air are further validated by comparing with theexperimental data from previous work, and they agreed well with the experimental results. The predicted temperature field has indicated that the peak temperature is located in the second basket from the top alongthe vertical center line by effects of the natural convection. As the Rayleigh number increases, the convective heat transfer isdominant and the heat transfer due to the local circulation becomes stronger. The heat transfer characteristics show that theNusselt numbers corresponding to 1.5×106 < Ra < 1.0×107 are proportional to 0.5 power of the Rayleigh number, while theNusselt numbers for 1.0×107 < Ra < 8.0×107 are proportional to 0.27 power of the Rayleigh number. These results agreedwell with the trends of the experimental data for Ra>1.0×107.

Microstructural, biochemical and drying characteristics of dehydrated ‘Sunectwentyone’ nectarines as affected by sodium metabisulphite

Loriane A. Yanclo,Gunnar Sigge,Zinash A. Belay,Feroza October,Oluwafemi J. Caleb 한국식품과학회 2022 Food Science and Biotechnology Vol.31 No.3

Nectarine fruit is highly perishable due to its high moisture content (89%) and susceptibility to decay. Continuous degradation in quality attributes due to physi- ological responses and ripening result ultimately in post- harvest losses. Drying of fruit offers the possibility to minimize losses and add value to fresh produce. Thus, this study evaluated the impacts of sodium metabisulphite (SMB; 10 g/kg) and characterized the influence of hot air (50 C) drying on the kinetics, fruit tissue microstructure, and the physicochemical properties of dried’Sunectwentyone’ nectarines (Super star). Out of the nine mathematical models, Logarithmic and Henderson, and Pabis models were the most suitable to predict the drying behaviour of sliced nectarines (R2 = 0.94). Based on the microstructural analysis, prolonged drying led to higher tissue displacement/disruption in dehydrated nectarine sli- ces. Results showed that SMB treatment was more effec- tive in maintaining both the freshness and the color of ’Sunectwentyone’ nectarine than the untreated.

Drying Characteristics of Agricultural Products under Different Drying Methods: A Review

Lee, Seung Hyun,Park, Jeong Gil,Lee, Dong Young,Kandpal, Lalit Mohan,Cho, Byoung-Kwan,Hong, Soon-jung,Jun, Soojin Korean Society for Agricultural Machinery 2016 바이오시스템공학 Vol.41 No.4

Purpose: Drying is one of the most widely used methods for preserving agricultural products or food. The main purpose of drying agricultural products is to reduce their water content for minimizing microbial spoilage and deterioration reaction during storage. Methods: Although numerous drying methods are successfully applied to dehydrate various agricultural products with little drying time, the final quality of dried samples in terms of appearance and shape cannot be guaranteed. Therefore, based on published literature, this review was conducted to study the drying characteristics of various agricultural products when different drying methods were applied. Results: An increase in the drying power of sources-for example, increase in hot air temperature or velocity, infrared or microwave power-and the combination of drying power levels can reduce the drying time of various agricultural products. In addition, energy efficiency in drying significantly relies on the compositions of the dried samples and drying conditions. Conclusions: The drying power source is the key factor to control entire drying process of different samples and final product quality. In addition, an appropriate drying method should be selected depending on the compositions of the agricultural products.

Drying Characteristics of Agricultural Products under Different Drying Methods: A Review

( Seung Hyun Lee ),( Jeong Gil Park ),( Dong Young Lee ),( Lalit Mohan Kandpal ),( Byoung-kwan Cho ),( Soon-jung Hong ),( Soojin Jun ) 한국농업기계학회 2016 바이오시스템공학 Vol.41 No.4

Purpose: Drying is one of the most widely used methods for preserving agricultural products or food. The main purpose of drying agricultural products is to reduce their water content for minimizing microbial spoilage and deterioration reaction during storage. Methods: Although numerous drying methods are successfully applied to dehydrate various agricultural products with little drying time, the final quality of dried samples in terms of appearance and shape cannot be guaranteed. Therefore, based on published literature, this review was conducted to study the drying characteristics of various agricultural products when different drying methods were applied. Results: An increase in the drying power of sources-for example, increase in hot air temperature or velocity, infrared or microwave power-and the combination of drying power levels can reduce the drying time of various agricultural products. In addition, energy efficiency in drying significantly relies on the compositions of the dried samples and drying conditions. Conclusions: The drying power source is the key factor to control entire drying process of different samples and final product quality. In addition, an appropriate drying method should be selected depending on the compositions of the agricultural products.

대류 건조 방식을 통한 액상 계면 활성제의 건조 특성 분석 및 입자성 물질과의 비교

심재우(Jaewoo Sim),오상현(Sanghyun Oh),박기호(Kiho Park),김동립(Dongrip Kim),김성일(Sungil Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

In this study, experiment of convection drying method was conducted to analysis the drying characteristics liquid material(i.e., surfactant) and compared with drying characteristics of particle material(i.e., carrot). The surfactant having the initial moisture content of 69% was used to carry out the drying experiment and the drying air temperature was setted the 110 and 130°C. For both surfactant and carrot, the equilibrium moisture content decreased as the drying air temperature increased. In the case of surfactant, the time required to reach the equilibrium moisture content decreased by 44.4% as the drying air temperature increased, but the time difference was insignificant in the case of carrots. The average drying rate in the falling rate drying period increased with the drying air temperature increased for both surfactant and carrot. Constant rate drying period were found during the drying process of surfactant and carrots at 130°C and 80°C respectively, but the constant rate drying period were not found during the drying process of surfactant and carrots at 110°C and 90°C respectively.

ANN Modeling of Drying Kinetics for Molded Pulp Product during Convective and Microwave Drying Process

Lingbo Kong1,Ziliang Zhang,Yang Song,Junzhong Chen 한국펄프·종이공학회 2023 펄프.종이기술 Vol.55 No.4

With the purpose of improving molded pulp product (MPP) drying process, the present work investigated the microwave drying performance of MPP under the power level of 500 W and compared that with the convective drying method. The drying kinetics, the effective moisture diffusivity, and the energy consumption of the two drying methods were evaluated respectively. It was found that the drying time was shortened from 22.0 min for convective drying to 16.0 min for microwave drying due to 27% of drying rate enhancement, and the effective moisture diffusivity was increased from 3.01×10-10 to 4.49×10-10 m2/s. Additionally, 88% of energy consumption could be saved in the microwave drying process. An artificial neural network (ANN) was employed to predict the moisture removing kinetics of MPP. The results revealed that the ANN modeling could be used to predict the drying kinetics of MPP effectively and then determine the moisture content in the drying process.

Numerical analysis of convective drying of a moving moist object

Kim, Donghyun,Son, Gihun,Kim, Sungil Elsevier 2016 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.99 No.-

<P><B>Abstract</B></P> <P>Convective drying of a moving moist object is investigated numerically solving the conservation equations of mass, momentum, energy and air moisture concentration based on a <I>k</I>– ∊ turbulence model in the external region of the object as well as the conservation equations of energy and object moisture concentration in the internal region. The external and internal conservation equations are coupled to the heat and mass transfer conditions on the object surface including the effects of evaporation and water activity. The numerical results show that the analogy between heat and mass transfer for the convective drying is valid only when the object temperature is close to the equilibrium temperature. The simple analytical formulations developed for the total drying rate are found to compare well with the numerical results. The effects of object velocity and thickness and the wall heat flux on the drying rate are quantified.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Complete numerical analysis is conducted for convective drying of a moving moist object. </LI> <LI> Analytical formulations are presented for evaluation of the total drying rate. </LI> <LI> The object flow rate is an important parameter to determine the drying rate. </LI> <LI> The optimum condition of object flow rate increases with the wall heat flux. </LI> </UL> </P>