• 한국식품저장유통학회지
• /
• 제2권1호
• /
• pp.155-161
• /
• 1995

We examined the drying characteristics and the drying rate model equation of garlic(allium sativum L.) using computer aided convective drying. The drying chanacteristic curve of garlic divided into constant rate drying period and 2 stage of falling rate drying period. The drying rate was fairly affected by hot air temperatures during the total drying period, but air flow rates has nearly no effect on the drying rate except initial drying period. Of the several model equation, r2 values of page model equation was the highest, and the estimated drying profiles were comparatively coincided with the observed drying profiles. Page model equation was suitable to predict the drying rate and moisture content during drying of sliced garlic.

• Journal of Biosystems Engineering
• /
• 제14권4호
• /
• pp.262-271
• /
• 1989

Red pepper is one of the most important agricultural products in Korea. Generally, raw red pepper is dried after harvest and the dried red pepper is powdered. Washing process is necessary to produce clean powder before powdering process. This study, therefore, was performed to analyze the drying characteristics of the rewetted red pepper and the energy utility during hot-air-convective and infrared-radiant drying. Drying effectiveness, De, was defined for the analysis of energy utility in this study, and its value was determined according to the energy source. Infrared-radiant drying was more favorable than convective drying according to drying effectiveness. But the temperature variation was appeared between the radiant surface and opposite surface of red pepper in infrared-radiant drying.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 추계학술대회논문집
• /
• pp.145-150
• /
• 2009

In this study, characteristics of microwave and convective drying are studied by using a multiphase porous media model. Temperature and moisture profiles for hot-air convective heating and microwave heating of 1-D porous media with varying time and space are numerically investigated. This result shows the microwave drying method is more effective than the convective drying method. Comparing to convective drying, microwave drying can increase temperature and evaporation rate significantly since microwave generates internal heat and increases internal pressure, which results in moisture movement toward the surface on which moisture is vaporized.

• Journal of the Korean Wood Science and Technology
• /
• 제32권1호
• /
• pp.45-51
• /
• 2004

본 연구는 두께 24 mm 뉴질랜드산 라디아타 소나무 단판의 마이크로파-열풍 복합 건조특성을 파악하기 위하여 수행되었다. 단판을 100℃ 열풍과 복합한 마이크로파 건조한 결과 함수율 160%에서 0%까지 건조하는데 7.5분이 소요되었다. 이 건조속도는 100℃ 열풍만으로 건조한 경우에 비하여 약 3배 정도 높은 수준이었다. 그러나 과도한 마이크로파 출력이 가해지면 탄흔이 남는 문제가 발생하였다. 그러므로 최적의 건조조건을 결정하기 위해서는 다양한 규격과 수종의 단판에 대한 마이크로파 건조특성의 파악이 요구됨을 알 수 있었다.

• 농업과학연구
• /
• 제47권3호
• /
• pp.519-532
• /
• 2020

Because lotus root has a short shelf life, the quality easily deteriorates. Thus, the harvested lotus roots are processed into a variety of products. Drying is one of the simplest food preservation methods, which can increase food stability. However, the convective drying method takes a long time and requires high energy consumption. Combination drying methods have emerged to overcome the limitations of the convective drying method. This study investigated the drying characteristics of lotus root and determined the optimal drying model of lotus root depending on the microwave and hot-air combination drying conditions. The lotus root slices (5 mm in thickness and 40 mm in diameter) were dried by different drying conditions that were combined with three microwave power levels (50, 100, and 150 W) and two hot air temperatures (50 and 60℃) at a velocity of 5 m·s^-1. Eight drying models were tested to evaluate the fit to the experimental drying data, and the effective moisture diffusion (D_eff) values of the lotus root slices dried by combination drying were estimated. The combination drying time of the lotus root was significantly reduced with the high air temperature and microwave power. The effective moisture diffusion (D_eff) of lotus root was more affected by the air temperature than microwave power intensity. Logarithmic model was most suitable to describe the drying curve of lotus root in the microwave-hot air combination drying method.

• Preventive Nutrition and Food Science
• /
• 제13권3호
• /
• pp.225-230
• /
• 2008

Onion slices were dehydrated in a single layer at drying air temperatures ranging from $50{\sim}70^{\circ}C$ in a laboratory scale convective hot-air dryer at an air velocity of 0.66 m/s. The effect of drying air temperature on the drying kinetic characteristics were determined. It was found that onion slices would dry within $210{\sim}460\;min$ under these drying conditions. Moisture transfer during dehydration was described by applying the Fick's diffusion model and the effective diffusivity changed between $1.345{\times}10^{-8}$ and $2.658{\times}10^{-8}\;m^2/s$. A non-linear regression procedure was used to fit 9 thin layer drying models available in the literature to the experimental drying curves. The Logarithmic model provided a better fit to the experimental drying data as compared to other models. Temperature dependency of the effective diffusivity during the hot-air drying process obeyed the Arrhenius relationship with estimated activation energy being 31.36 kJ/mol. The effect of the drying air temperature on the drying model constants and coefficients were also determined.

• International Journal of Advanced Culture Technology
• /
• 제3권2호
• /
• pp.138-143
• /
• 2015

This paper was aimed to study the drying kinetics of coffee and to investigate the thin-layer drying kinetics of coffee by using a convective air dryer. The coffee was dried for the temperatures of 40, 50 and $60^{\circ}C$ with relative humidity in the range of 14-25% the airflow rate fixed at 1 m/s. According to the experiment result, the drying rate curve showed that drying process took place only in the falling rate period. Seven thin layer drying models (Newton, Page, Henderson and Pabis, Logarithmic, Wang and Singh, Two terms, Modified Henderson and Pabis) were fitted to the experimental moisture content data. The Two-trem model was found to be a better model for describing the characteristics of coffee for the temperatures of 40, 50 and $60^{\circ}C$. The effective moisture diffusivity of coffee increased when the drying temperature increased. The value was in the range of $4.5028{\times}10^{-11}$ to $6.4803{\times}10^{-11}m^2/s$.

• Journal of Biosystems Engineering
• /
• 제41권4호
• /
• pp.389-395
• /
• 2016

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.

• 한국식품저장유통학회지
• /
• 제4권1호
• /
• pp.69-75
• /
• 1997

Peony is a medicinal herb which have utilized widely as chineses medicine. The paeoniflorin is the predominant component In peony root, monoterpene glucoside containing pinane structure. The effective components were extracted with the cold water from the intact peony roots, and effectively extracted with 70% ethanol from the dry powder of peony roots. The changes of paeoniflorin contents were investigated during the drying process of peony roots and processing of peony extract by the heat-treatment. Air-drying was the best condition for the preservation of paeoniflorin content among the drying processes of peony roots. But convective drying at 6$0^{\circ}C$ was recommended for the drying process of peony roots in large scale. The paeoniflorin in peony extracts was not destroyed by the treatment at 6$0^{\circ}C$ and 8$0^{\circ}C$ for 5 hrs, but destroyed 30%, 28% and 40% of paeoniflorin by treatment at 10$0^{\circ}C$ for 5 hrs, 115$^{\circ}C$ and 121$^{\circ}C$ for 10 minutes, respectively. The paeoniflorin was continueously extracted for 4 hrs from the dry pieces of peony roots(0.5$\times$0.5$\times$0.5cm) in boiling water but destroyed gradually after 4 hrs at 10$0^{\circ}C$. Paeoniflorins in 70% ethanol extracts of peony root were not destroyed at all in the process of concentration to dry powder at 60"C on vacuum.cuum.