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Theoretical and Experimental Research of the Apricots Drying Process Using High-Frequency Currents

Author: Olga Lupu
Degree:doctor of engineering
Speciality: 05.18.12 - Food industry processes and equipment
Scientific adviser: Andrei Lupaşco
doctor habilitat, professor, Technical University of Moldova
Scientific consultant: Galina Dicusar
Scientific council:


The thesis was presented on the 30 September, 2005
Approved by NCAA on the 22 December, 2005


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apricots, convection, high-frequency currents, electromagnetic field, drying, temperature, voltage


Thesis for the degree of the Doctor of Sciences on specialty 05.18.12. - Processes and apparatuses for the food industry enterprises, Technical University of Moldova, Chisinau, 2005.

The thesis is presented as a manuscript.

There are defended 45 scientific works, including 2 Certificates of Authorship, covering a range of theoretical and experimental investigations aimed at exploring the use of combined power supply– convection and high-frequency currents (HFC) – for the drying of apricots.

There have been determined such electrophysical parameters of apricots as tgδ and έ and their relation to the frequency of the electromagnetic field, temperature and humidity of the raw material. There has been determined the frequency of the electromagnetic field for the heat processing of apricots – 27 MHz.

The kinetics of the apricots drying process has been investigated, in case of convection and combined power supply. The kinetic characteristics of the process have been deduced.

As a result a mathematical model of the drying process has been suggested, it relates the time, temperature, the voltage of the electromagnetic field and the humidity of the raw material.

Taking into account the results of the investigations, it has been concluded that the drying of apricots by means of the combined power supply has to be performed using the following parameters: temperature of 1000С, speed of 0,65 m/s and the voltage of the field of 18000 V/m.

The process has to be performed in 2 steps: the first step when the humidity of the raw material is between 195 % - by means of convection method, the second step – final humidity of 25 % is performed using the combined power supply: HFC + convection.

It has been determined that the intensity of the drying process of apricots by means of combined power supply – convection + HFC – increases more than 1.7 times.

A scheme of the drying installation for the heat processing of apricots be means of HFC has been proposed.