Model of microwave drying drying heat transfer process in yellow peach

On the basis of Fick diffusion model and conduction model, considering the effects of heat and moisture diffusion, direct evaporation of water and internal heat source, the internal mass and heat transfer model of microwave drying yellow peach was obtained. The model is simulated by explicit finite difference method, and the calculated values are basically consistent with the measured values.

Key words: 

microwave drying equipment

 yellow peach, model

In the past, most of the mass and heat transfer models used Fick diffusion law and transfer equation directly in the study of drying of agricultural materials. In the model, the effects of temperature gradient on water diffusion and evaporation on temperature change are neglected, and the mass and heat parameters are assumed to be constant. These will lead to great limitations in model and simulation conclusions.

Microwave drying of fruits and vegetables is very fast, and its mechanism is different from that of hot air drying. There are moisture vapor diffusion and heat-humidity effects in drying materials, but no such mass-heat model has been reported. In this paper, a mathematical model for microwave drying of internal heat transfer in yellow peach is established and numerical simulation is carried out.

microwave drying of yellow peach 

Microwave drying characteristics and better technology of potato chips

Absrtact: The orthogonal experiment of microwave drying potato chips was carried out, and the water loss and power consumption characteristics of microwave drying potato chips were obtained. Regression analysis was carried out and the equation of microwave drying potato chips was obtained, which was better fitted by equation. The quadratic orthogonal regression experiment of the factor index was carried out, and the significance of the factors of the regression equation of each index on the index was obtained. The comprehensive optimization of the parameters was carried out, and the better combination of the parameters was put forward.

Key words:

  microwave drying equipment

; potato; characteristics; better technology

Preface

Microwave drying is mainly based on the penetration characteristics of microwave. Microwave is a kind of electromagnetic wave, which can produce high frequency electromagnetic field. Polar molecules in dielectric materials change their polar orientation with the frequency of electromagnetic field, which makes molecules vibrate back and forth and generates friction heat. At this time, the field energy of electromagnetic field is transformed into heat energy, which makes the medium temperature rise continuously and has better drying effect. Using microwave technology to dry agricultural products is one of the developing trends in the future.

microwave drying potato equipment

Experimental study on microwave drying of longan

Absrtact: In order to explore the new technology of microwave drying longan, fixed power microwave drying experiments of longan under different heating and intermittent time combinations were carried out by using microwave drying equipment and self-developed computer on-line testing system.

microwave drying equipment 

The results showed that the microwave drying process of longan could be divided into three stages: acceleration, constant speed and deceleration drying. Most of the water loss process of longan was in the constant speed stage. Within 2.7-5 hours, the fresh longan fruit could be dried to the moisture content below 20%(w.b.) and the satisfactory drying quality was obtained. The microwave heating time had the greatest influence on drying speed. The effect of batch time is limited by heating time. In the later stage of drying, the heating time should be shortened to control the temperature rise of materials and avoid excessive drying. The regression equation based on experimental data can be used to describe the process of two-stage microwave batch drying of longan.

Key words: microwave drying longan; intermittent heating

Longan is a special fruit in southern China, which is rich in nutrients and has high economic value. However, longan has multiple tissues of shell, pulp and stone, and its pulp has high sugar content and high moisture content. Therefore, it is difficult to dry the whole fruit with shell. At present, the drying methods are mostly baking and hot air. It takes 6 to 9 days for drying method, 14 to 24 hours for continuous drying in tunnel drying room with 90 C hot air, and 6 days for Tunnel Greenhouse drying device with air collector. Long drying time, high energy consumption and unstable drying quality are the main problems in longan drying.

microwave drying longan 

Effects of different drying methods on rehydration and quality of carrot

Absrtact: Rehydration experiments were carried out on dried carrot products obtained by hot air drying, microwave drying equipment and combination of hot air drying and microwave drying. The effects of different drying methods and combination of different parameters on rehydration and sensory quality of dried carrot products were analyzed.

microwave drying equipment

The results showed that the rehydration performance and sensory quality of dried carrot products obtained by different drying methods were significantly different. Reducing hot air temperature, shortening hot air drying time and reducing microwave heating power could improve the rehydration and quality of dried carrot products. Hot air temperature and hot air drying of combined hot air and microwave drying could improve the rehydration and quality of dried carrot products. When the moisture content and microwave power of the finished material are 65 C, 50 W and 170W respectively, the dry products have ideal sensory properties.

microwave drying carrot

Experimental study on microwave drying of Litchi

In order to explore the new technology of litchi microwave drying, a systematic experiment of litchi microwave drying was carried out by using a self-mademicrowave drying equipment test system. The water loss characteristics of litchi microwave drying were tested and analyzed. The distribution law of temperature in litchi pulp during drying process was found out. The influence of drying conditions on drying process was analyzed. The mathematical model of litchi microwave thin layer drying was established.

microwave drying equipment

Keywords: microwave drying litchi, drying characteristics

Introduction

Litchi is a kind of high-quality and high-yield subtropical fruit with high economic value. Its fruit ripens in high temperature and humidity season. It should be treated in time after harvesting. Besides fresh food and preservation, a large number of dried fruits are produced. However, litchi drying is different from other fruits drying. Its pulp has high sugar content, high moisture content and is dry. Multi-structure structure structure, moisture migration after harvesting and heat transfer in drying process are complex, at the same time, it is not sliced with shell drying. Drying is in the state of internal control, and it is more difficult to dry .

microwave drying litchi

Microwave drying characteristics of rice and its thermal model injection

There are two stages in grain drying process under microwave drying. The drying power is 0.2W/g or below 0.2W/ g, the germination rate is high, and the waist burst rate is low. The fatty acid content of dried storage is lower than that of hot air. A moisture and heat transfer model for microwave drying of cereals was established, and the coefficient of moisture diffusivity was determined.

microwave drying equipment

Keywords: microwave drying model for rice drying

Preface

Different from hot air and other drying methods, microwave drying has broad application prospects because of the uniform diffusion of moisture on the inner surface and the fast drying speed caused by the direct heating of materials after absorbing microwave energy. After harvest, the rice needs to be dried and stored safely. The drying method and reasonable process are very important. Up to now, little research has been done on microwave drying of rice, and the drying characteristics are not clear yet. In this paper, the microwave drying characteristics of paddy were studied, and a mass-heat model was established to provide reference for further research and production application.

microwave drying of rice

Experimental study on microwave drying technology of chive

Abstract: microwave drying equipment is used to dry fresh shallot in order to obtain high-quality dried chive. Through single factor and orthogonal test, the effects of quality, stacking thickness and microwave power on sensory quality and rehydration rate of dried onion were analyzed in order to find out the optimum drying process parameters. The results showed that under the conditions of microwave power of 2 000 W, stacking thickness of 25 mm and mass of 130 g, the quality of dried onion was the best.

microwave drying equipment

Key words: chive microwave drying; process optimization; rehydration rate; sensory quality

Introduction

Onion is a kind of onion plant with aromatic odor growing in central Asia. It is a necessary ingredient and condiment in various convenient foods and dishes. Onion has a good physiological effect in human body. It is not only beneficial to digestion of intestine and stomach, but also has antipyretic effect. Allium foliage is the key part of photosynthesis and the main food eaten by chive. However, it is not easy to store for a long time because of its high water content, yellow leaves and decay. Even if it is kept fresh in a fresh-keeping cabinet, it is difficult to keep it for a long time. In order to solve the problem of fresh preservation of chive, freeze-drying is the most efficient method. Although freeze-drying technology solves the problem that onion is perishable and not easy to be preserved for a long time, this drying technology has high investment cost and is not easy to be widely popularized.

chive microwave drying