• Journal of Biosystems Engineering
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• v.41 no.1
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• pp.43-50
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• 2016

Purpose: The present study is aimed at examining the drying characteristics of sea tangle through a combination of microwave and far-infrared drying experiment and finding the optimal drying conditions. Methods: Sea tangle was cleaned and cut into fine pieces (5mm) before they were subjected to combinational drying by microwave and far-infrared ray. The amount of specimen per drying is 2 kg. The finely cut pieces of sea tangle were preheated in a microwave dryer for three different lengths of time (10, 15, and 20 min). Subsequently, they were dried using a far-infrared dryer at tow temperatures ($90^{\circ}C$ and $100^{\circ}C$) at an air velocity of 0.8 m/s until the final moisture content reduced to 10%. Results: Sea tangle dried under the condition of 20 min of preheating in the microwave dryer and drying at $100^{\circ}C$ by the far-infrared dryer. Of the drying models verified in this study, the logarithmic model showed high accuracy with the coefficient of determination $R^2>0.7825$ and RMSE<0.1095. The rehydration ratio of sea tangle was the highest (12.87 g water/g dry matter) under the condition of 15 min of preheating in the microwave dryer and drying at $100^{\circ}C$ by the far-infrared dryer. The energy consumption for the combination of microwave and far-infrared drying was the lowest (4.78 kJ/kg water) under the condition of 20 min of preheating in the microwave dryer and drying at $100^{\circ}C$ by the far-infrared dryer. Conclusions: Considering the drying time, discoloration during drying, rehydration ratio, and energy consumption for the drying of sea tangle, the optimal drying conditions for high-quality sea tangle are 15 min of preheating in a microwave dryer and drying at $100^{\circ}C$ by a far-infrared dryer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.424-432
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• 2018

We herein analyze and study the shielding effectiveness characteristic of an open conveyor-belt-type microwave dryer that is widely used in industry. In particular, the electromagnetic wave leakage problem of the open-type conveyor belt dryer using a general-purpose 2.45-GHz magnetron was improved by applying the corrugated rectangular waveguide. We conducted the electromagnetic simulation of the optimal shielding effectiveness characteristic with regard to the proposed waveguide structure to analyze the attenuation characteristics of the corrugated rectangular waveguide. To verify the shielding effectiveness characteristic of the fabricated corrugated rectangular waveguide by IEEE standard 299, we achieved the shielding effectiveness of more than 30 dB in the practical microwave dryer with the proposed corrugated rectangular waveguide.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.1
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• pp.60-65
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• 2008

Chemical properties of barley leaf were investigated using different drying methods. Moisture contents of barley leaf were 75.22%, 7.54%, 2.57%, 6.74% and 8.91% for samples dried using raw, hot-air dryer, freeze dryer, shade dryer, vacuum freeze dryer and microwave dryer, respectively. Mineral contents were high Ca, Mg, Na, P, and K in barley leaf regardless of drying methods. Organic acid contents were oxalic acid, acetic acid, citric acid and fumaric acid with no differences between drying methods. Contents of vitamin C were 142.56 mg%, 629.23 mg%, 598.48 mg%, 657.62 mg% and 724.34 mg% for samples using raw, hot-air dryer, freeze dryer, shade dryer, vacuum freeze dryer and microwave dryer, respectively. Chlorophyll contents of barley leaf dried by hot-air dryer and shade dryer were higher than in that of freeze dryer and microwaves dryer. b-values were lower in freeze dryer than in that of other dried methods.

• International Journal of Industrial Entomology and Biomaterials
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• v.42 no.1
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• pp.14-20
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• 2021

Mulberry was dried with low temperature vacuum dryer using microwave. The nutritional compositions of microwave-dried mulberry including proximate composition, sugar content, mineral content, total phenolic, flavonoids, and anthocyanin, beta-carotene, vitamin C, and amino acid composition were measured. Sugar contents of mulberry were 42.6 mg/100g (Cheongilppong) and 43.27 mg/100g dw (Gwasang No. 2). The main components of mulberry sugars were fructose and glucose. Mineral analysis showed that K, P, Ca, and Mg were abundant regardless of mulberry cultivars.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.876-877
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• 2013

기존 식품건조 공정방법인 냉동보관, 자연건조에 의한 건조방식은 상품의 품질을 저하시켜 경쟁력이 낮고, 열풍건조 등 자동화된 건조공정의 경우에도 열에 의한 건조대상물의 탈색 및 변형 등의 특성변화로 인하여 고부가가치 상품의 제조하기 어려움의 한계로 인한 보관 및 상품성 저하 문제점 대두되고 있다. 따라서 이러한 문제점들을 해결하기 위하여 마이크로웨이브 건조기술 도입을 통한 건조방식 개선이 필요하다. 마이크로웨이브 건조기술은 표면 가열방식의 기존 건조방식에 비해 가열대상 물질의 표면 손상이 적고 전력효율이 우수하다는 특징으로 인하여 건조분야에서 점차 해당 건조기술이 확대되고 있다. 본 논문에서는 마이크로웨이브 건조에서 공정관리 요소들의 상태를 실시간으로 수집하고 이를 기반으로 숙련자의 작업공정 환경을 습득하여 데이터 베이스화하여 자동화된 작업공정을 제공하기 위한 모니터링 제어시스템을 제안하였다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2010.04a
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• pp.174-174
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• 2010

• Journal of Biosystems Engineering
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• v.37 no.6
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• pp.385-397
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• 2012

Purpose: Drying characteristics of sawdust was studied under batch mode using lab scale microwave dryer. The objective of this study was to investigate the effect of material load and microwave output power on drying characteristics of sawdust. Methods: Material load and microwave output power were varied from 23 to 186 g and 530 to 370 W respectively. Different kinetic models were tested to fit the drying rates of sawdust. Similarly, the activation energy was calculated by employing the Arrhenius equation. Results: The drying efficiency increased considerably, whereas the specific energy consumption significantly decreased with increase in material load and microwave output power. The cumulative energy efficiency increased by 9%, and the specific energy consumption decreased by 8% when the material load was increased from 23 to 186 g. The effective diffusivity increased with decrease in material load and increase in microwave output power. The previously published model gave the best fit for data points with $R^2$ and RMSE values of 0.999 and 0.01, respectively. Conclusions: The data obtained from this study could be used as a basis for modeling of large scale industrial microwave dryers for the pellet production.

• Journal of the Korean Wood Science and Technology
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• v.29 no.4
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• pp.25-32
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• 2001

A microwave vacuum (MW/V) dryer was developed for drying short roundwoods, from which woodcraft souvenirs in Korean market are mostly made, and which were hardly dried without defects in a conventional kiln. It consisted of three 1.5 kW magnetrons of 2,450 MHz, a vacuum pump, a load cell of 100 kg and a cavity of $580{\times}580{\times}1,360\;mm^3$. A computer program was developed to switch on or off the magnetrons according to drying schedules, those were based on microwave injection time or the average of wood temperatures. To evaluate the new MW/V dryer the roundwood specimens of rigida pine, poplar and birch were dried. Their log diameters and lengths ranged from 125 to 25 em and from 25 to 50 cm, respectively. In spite of the presence of minor drying defects, the MW/V drying is found to be an effective method for drying short roundwoods. Wooden turneries made of red alder and ash logs were also MW/V dried from green to 4%MC without any degradation. The rates of the MW/V drying were examined for three different lengths of poplar logs.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1999.12a
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• pp.421-427
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• 1999

• Journal of the Korean Wood Science and Technology
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• v.37 no.4
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• pp.349-356
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• 2009

Logs with average diameters of 20~30 cm were dried with microwave to investigate microwave drying characteristic of log and determine the optimal drying conditions. Microwave dryer with output of 20 kW was controlled with respect to the temperature of log during drying. Japanese red pine logs with average diameter of 281.9 mm were dried safely by microwave to below moisture content of 20% within 48 hours. Chinese toon logs showed serious surface checks during microwave drying. Higher drying rates were found with higher initial moisture content.