In this study far infrared vacuum drying kinetics and change of color quality parameters of apple... more In this study far infrared vacuum drying kinetics and change of color quality parameters of apple slices were analyzed. The experimental data set of drying kinetics was obtained on the experimental set-up designed to imitate an industrial far infrared vacuum dryer. For approximation of the experimental data with regard to the moisture ratio four well known thin-layers drying models from scientific and engineering literature and new developed model of Mitrevski et al., were used. The performed statistical analyzes show that the model of Mitrevski et al., has the best statistical performance than well-known thin-layer drying models. The estimated values of moisture diffusivity of apple obtained from this study are within the range from 2.80?10?11 to 1.70?10?10 m2/s. A negative effect on the total color change of far infrared vacuum dried apple slices was observed with in-creasing of temperature of infrared heaters and vacuum pressure.
Agricultural activity employs an estimated 1.3 billion workers worldwide, which is half of the wo... more Agricultural activity employs an estimated 1.3 billion workers worldwide, which is half of the world's labour force. In terms of fatalities, injuries and work-related ill-health, it is one of the four most hazardous sectors of activity (along with construction, transportation and storage and manufacturing). According to International Labour Organization (ILO) estimates, at least 170000 agricultural workers are dying each year. In this paper, the statistical indicators concerning non-fatal and fatal accidents at work in agriculture, forestry and fishing activity and an incidence rate in the Member State of the European Union (EU-27) and in the R.N. Macedonia during 2017÷2021 were presented. The performed statistical analysis shows that the number of non-fatal and fatal accidents at work in agriculture, forestry and fishing activity in EU-27, in 2020 was decreased in comparison with 2017. In the R.N. Macedonia in 2021, there was a decrease in the number of non-fatal accidents at w...
In this study, the drying kinetics of apple (control, blanching and blanching in 1% potassium met... more In this study, the drying kinetics of apple (control, blanching and blanching in 1% potassium meta bisulphate) in a tunnel dryer was studied at 50, 60, and 70°C air temperatures. The drying of apple slices occurred in a falling rate period. It was found that treated apple slices dried faster. Six thin layer-drying models were fitted to the experimental moisture ratio. Among the mathematical models evaluated, the logarithmic model satisfactorily described the drying behaviour of apple slices with high r2 values. The effective moisture diffusivity (Deff) of apple slices increased as the drying air temperature increased. The Deff values were higher for the treated samples than for the control.
Numerous mathematical models for approximation of sorption data of food and agriculture materials... more Numerous mathematical models for approximation of sorption data of food and agriculture materials are available in the referent scientific and engineering literature. Depending on the number of parameters included in the model for approximation of moisture sorption data, the models may be one, two, three, four, five or more parametric. Also the sorption models may be included or not the temperature as a parameter into the equation. The objectives of the presented article was a review of one hundred seventy-two sorption no temperature dependent sorption isotherm models which used to for approximation equilibrium moisture data of food materials. For statistics evaluation of those models the equilibrium moisture data of quince were used. The value on coefficient of determination the root mean squared error, the mean relative deviation and graphical evaluation of the residual randomness were the main assessment criterions for statistical evaluation of the sorption isotherms model. Based...
In this paper the lamella heat exchangers were presented. They are used for water and air as oper... more In this paper the lamella heat exchangers were presented. They are used for water and air as operating mediums, and can be differentiated by the shape of the ribs. The one has sinuous type of ribs, while the other one has flat lamella ribs. Better heat transfer can give the exchanger with higher values of coefficient r and factor j a. A comparison between both types of heat exchangers is made with reference to air velocity in the minimum flow cross-section and Reynolds' number. ARTICLE HISTORY
Drying of food materials is a complex process of simultaneous heat and mass transfer within dried... more Drying of food materials is a complex process of simultaneous heat and mass transfer within dried material and from its surface to the surroundings, caused by a number of transport mechanisms. There are several different methods of describing the complex simultaneous heat and moisture transport processes within drying material. Thin-layer drying models are important tools in mathematical modeling of drying processes. In scientific literature generally for evaluation of thin-layer models, that use approximation of experimental drying data, the values of the coefficient of determination (R2), correlation coefficient (r), reduced chi-square, root mean square error (RMSE), and mean bias error (MBE) are the most common criteria to select the best model. In this paper one approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. Fresh banana were used in this study. The experimental data set of thin-layer drying kinetics of banana slices at fou...
In this paper the critical activities for health and safety at work during working operations for... more In this paper the critical activities for health and safety at work during working operations for assembly/disassembly of parts under pressure were detected. After that protective measures during loading, unloading and transportation of elements at height and protective measures during working at height were discussed. Thermal power plant (TPP) Bitola is the largest electricity producer in the Republic of Macedonia with installed capacity of 3x225 MW, which provides 80 % of the total energy production in the Republic of Macedonia, with average annual production 4.200 GWh. Rehabilitation and performance improvement for TPP Bitola are provided to modernization and revitalization of turbines, generators and automation, revitalization and modernization of the boilers with NOx emissions reduction and revitalization of cooling towers, and revitalization for SOx, dust and particle emission reduction. Taking this into account in this paper some safety measures at work during the execution o...
a free-access multidisciplinary publication of the Faculty of Engineering Hunedoara 1. Abstract: ... more a free-access multidisciplinary publication of the Faculty of Engineering Hunedoara 1. Abstract: In this paper, some of the statistical indicators which refer to serious and fatal accidents at work in the European Union (EU-28) and in the Republic Macedonia are presented. The performed statistical analysis shows that the number of serious and fatal accidents at work in EU-28 and in the Republic Macedonia, in 2012 was decreased in comparison with 2008. Nevertheless, the Republic of Macedonia has high incidence rate for fatal accidents at work compared to highly develop European countries. The activities of public administration and defense, construction, manufacturing, transportation and storage sector and the activities of households as employers are the economic sectors in which it is possible to prevent injuries caused by serious accidents at work. Тhe activities of households as employers, construction sector, transportation and storage sector and agriculture, forestry and fishin...
This model explains the heat flow in a confined space with transparent walls (glass or plastic). ... more This model explains the heat flow in a confined space with transparent walls (glass or plastic). A software is used to analyze the behavior of transparent walls coated with "LLumar" film. This film has many advantages, but in this paper, we will focus on energy savings. Energy savings give quick return on investment and are considered a smart investment. Energy-saving LLumar film can increase performance of almost every window system, significantly reducing energy consumption and requirements. Professional energy audits have shown that buildings with LLumar film can achieve annual energy savings of up to 15%, blocks 99% of harmful UV rays and improves comfort by reducing heat and glare. Regardless of whether it is residential, commercial or glass house space as described in this paper, LLumar the world's leading brand of architectural film for decades improves the well-known buildings around the world with proven results. LLumar films will greatly increase energy effic...
In this paper the experimental results of far-infrared vacuum drying of apple slices were present... more In this paper the experimental results of far-infrared vacuum drying of apple slices were presented. The investigation of far-infrared vacuum drying processes was conducted on the experimental setup that was designed to imitate industrial batch dryer. Apple slices were dried at various vacuum pressures and temperatures of heaters which were kept constant during the single experiments. Five well known thin layer drying models from scientific literature were used to approximate the experimental data of drying kinetics in terms of moisture ratio. For each model and data set, the statistical performance index and chi-squared value were calculated and models were ranked afterwards. The performed statistical analysis shows that the model of Aghbashlo gives the best results for approximation of experimental drying data of apple slices. ARTICLE HISTORY
The moisture adsorption isotherms of pear were determined at 15 °C, 30 °C, and 45i°C using the st... more The moisture adsorption isotherms of pear were determined at 15 °C, 30 °C, and 45i°C using the standard static gravimetric method over a range of water activity from 0.112 to 0.920. The experimental data were fitted with isotherm equations recommended in ASAE Standard D245.5. In order to find which equation gives the best results, large number of numerical experiments were performed. After that, several statistical criteria proposed in scientific literature for estimation and selec-tion of the best sorption isotherm equations were used. For each equation and ex-perimental data set, the average performance index was calculated and models were ranked afterwards. After that, some statistical rejection criteria were checked (D'Agostino-Pearson test of normality, single-sample run test and significance and precision of the model parameters). The performed statistical analysis shows that the Guggenheim-Anderson-de Boer equation has the highest value of average per-formance index, but...
In this paper, the results of comparative analysis between transcendental and cyclometric sorptio... more In this paper, the results of comparative analysis between transcendental and cyclometric sorption isotherm models are presented. In order to find which model gives the best results, some numerical experiments were made. The experimental data set for equilibrium moisture content and the water activity for apple, pear, kiwi and banana at two different temperatures were used from the scientific literature. For each model and data set, several statistical parameters were calculated and models were ranked afterwards. The performed comparative analysis shows that the cyclometric models in many cases have higher values of the coefficient of determination, and lower values of the root mean squared error and the mean relative deviation than transcendental the isotherm models. All these results show that the cyclometric sorption isotherm models give the best overall fit to experimental data. After choosing the best transcendental and cyclometric model with the high value of statistical perfo...
In this paper, a new approach for selection of a thin-layer drying model based on serial statisti... more In this paper, a new approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. The experimental data set of thin-layer drying kinetics of apple slices at five different drying air temperatures (40, 60, 80, 100 and 120 C) and three drying air velocities (1, 2 and 3 ms-1) were obtained on the experimental setup, designed to imitate an industrial convective dryer. The drying data were fitted with twenty-three published thin-layer drying models (Lewis, Page, Modified Page, Henderson and Pabis, Modified Henderson and Pabis, Logarithmic(Asymptotic), Two term, Two term exponential, Midilli, Diffusion approach, Wang and Singh, Weibull, Aghbashlo, Verma., Grigorias, Parabolic, Hll, Demir, Logarithmic,Logistic, Vega-Lemus, Jena-Das and Alibas). In order to find which model gives the best results, some numerical experiments were made. For each model and data set, the performance index was calculated and models were ranked afterwards. After that, sev...
This paper describes the experimental results on the drying of the potato slices by infrared radi... more This paper describes the experimental results on the drying of the potato slices by infrared radiation under vacuum condition. The investigation of vacuum far-infrared drying processes was conducted on the experimental set-up that is designed to imitate industrial batch dryer. The experimental conditions have been chosen such that heaters’ temperature and vacuum chambers’ pressure have been in the range used on the industrial dryer. Potato slices were dried at various vacuum pressures (20, 40, 60 and 80 kPa) and temperatures (120, 140, 160, 180 and 200 C) which were kept constant during the single experiments. Based on experimental drying data, it was found that the drying time decreased with an increase of temperature of heaters and the decrease in the chamber pressure. It was also concluded that the influence of the temperature in vacuum chamber has more significant effect on reducing of the drying time than the vacuum pressure. Ten well known thin layer drying models from scienti...
In this paper the drying kinetics of far-infrared vacuum drying of some vegetables and fruits are... more In this paper the drying kinetics of far-infrared vacuum drying of some vegetables and fruits are presented. The experimental data of drying kinetics were obtained on experimental drying setup designed to imitate industrial dryer. Two well-known thin layer drying models from scientific literature were used to approximate the experimental data of drying kinetics in terms of moisture ratio. The performed statistical analysis shows that the model of Aghbashlo gives the best results for approximation of experimental drying data. ARTICLE HISTORY Received: 25.06.2017. Accepted: 11.08.2017. Available: 30.09.2017.
In this paper, a new approach for selection of a thin-layer drying model based on serial statisti... more In this paper, a new approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. The experimental data set of thin-layer drying kinetics of apple slices at five different drying air temperatures (40, 60, 80, 100 and 120 o C) and three drying air velocities (1, 2 and 3 ms -1 ) were obtained on the experimental setup, designed to imitate an industrial convective dryer. The drying data were fitted with twenty-three published thin-layer drying models (Lewis, Page, Modified Page, Henderson and Pabis, Modified Henderson and Pabis, Logarithmic(Asymptotic), Two term, Two term exponential, Midilli, Diffusion approach, Wang and Singh, Weibull, Aghbashlo, Verma., Grigorias, Parabolic, Hll, Demir, Logarithmic,Logistic, Vega-Lemus, Jena-Das and Alibas). In order to find which model gives the best results, some numerical experiments were made. For each model and data set, the performance index was calculated and models were ranked afterwards. After that,...
In this study far infrared vacuum drying kinetics and change of color quality parameters of apple... more In this study far infrared vacuum drying kinetics and change of color quality parameters of apple slices were analyzed. The experimental data set of drying kinetics was obtained on the experimental set-up designed to imitate an industrial far infrared vacuum dryer. For approximation of the experimental data with regard to the moisture ratio four well known thin-layers drying models from scientific and engineering literature and new developed model of Mitrevski et al., were used. The performed statistical analyzes show that the model of Mitrevski et al., has the best statistical performance than well-known thin-layer drying models. The estimated values of moisture diffusivity of apple obtained from this study are within the range from 2.80?10?11 to 1.70?10?10 m2/s. A negative effect on the total color change of far infrared vacuum dried apple slices was observed with in-creasing of temperature of infrared heaters and vacuum pressure.
Agricultural activity employs an estimated 1.3 billion workers worldwide, which is half of the wo... more Agricultural activity employs an estimated 1.3 billion workers worldwide, which is half of the world's labour force. In terms of fatalities, injuries and work-related ill-health, it is one of the four most hazardous sectors of activity (along with construction, transportation and storage and manufacturing). According to International Labour Organization (ILO) estimates, at least 170000 agricultural workers are dying each year. In this paper, the statistical indicators concerning non-fatal and fatal accidents at work in agriculture, forestry and fishing activity and an incidence rate in the Member State of the European Union (EU-27) and in the R.N. Macedonia during 2017÷2021 were presented. The performed statistical analysis shows that the number of non-fatal and fatal accidents at work in agriculture, forestry and fishing activity in EU-27, in 2020 was decreased in comparison with 2017. In the R.N. Macedonia in 2021, there was a decrease in the number of non-fatal accidents at w...
In this study, the drying kinetics of apple (control, blanching and blanching in 1% potassium met... more In this study, the drying kinetics of apple (control, blanching and blanching in 1% potassium meta bisulphate) in a tunnel dryer was studied at 50, 60, and 70°C air temperatures. The drying of apple slices occurred in a falling rate period. It was found that treated apple slices dried faster. Six thin layer-drying models were fitted to the experimental moisture ratio. Among the mathematical models evaluated, the logarithmic model satisfactorily described the drying behaviour of apple slices with high r2 values. The effective moisture diffusivity (Deff) of apple slices increased as the drying air temperature increased. The Deff values were higher for the treated samples than for the control.
Numerous mathematical models for approximation of sorption data of food and agriculture materials... more Numerous mathematical models for approximation of sorption data of food and agriculture materials are available in the referent scientific and engineering literature. Depending on the number of parameters included in the model for approximation of moisture sorption data, the models may be one, two, three, four, five or more parametric. Also the sorption models may be included or not the temperature as a parameter into the equation. The objectives of the presented article was a review of one hundred seventy-two sorption no temperature dependent sorption isotherm models which used to for approximation equilibrium moisture data of food materials. For statistics evaluation of those models the equilibrium moisture data of quince were used. The value on coefficient of determination the root mean squared error, the mean relative deviation and graphical evaluation of the residual randomness were the main assessment criterions for statistical evaluation of the sorption isotherms model. Based...
In this paper the lamella heat exchangers were presented. They are used for water and air as oper... more In this paper the lamella heat exchangers were presented. They are used for water and air as operating mediums, and can be differentiated by the shape of the ribs. The one has sinuous type of ribs, while the other one has flat lamella ribs. Better heat transfer can give the exchanger with higher values of coefficient r and factor j a. A comparison between both types of heat exchangers is made with reference to air velocity in the minimum flow cross-section and Reynolds' number. ARTICLE HISTORY
Drying of food materials is a complex process of simultaneous heat and mass transfer within dried... more Drying of food materials is a complex process of simultaneous heat and mass transfer within dried material and from its surface to the surroundings, caused by a number of transport mechanisms. There are several different methods of describing the complex simultaneous heat and moisture transport processes within drying material. Thin-layer drying models are important tools in mathematical modeling of drying processes. In scientific literature generally for evaluation of thin-layer models, that use approximation of experimental drying data, the values of the coefficient of determination (R2), correlation coefficient (r), reduced chi-square, root mean square error (RMSE), and mean bias error (MBE) are the most common criteria to select the best model. In this paper one approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. Fresh banana were used in this study. The experimental data set of thin-layer drying kinetics of banana slices at fou...
In this paper the critical activities for health and safety at work during working operations for... more In this paper the critical activities for health and safety at work during working operations for assembly/disassembly of parts under pressure were detected. After that protective measures during loading, unloading and transportation of elements at height and protective measures during working at height were discussed. Thermal power plant (TPP) Bitola is the largest electricity producer in the Republic of Macedonia with installed capacity of 3x225 MW, which provides 80 % of the total energy production in the Republic of Macedonia, with average annual production 4.200 GWh. Rehabilitation and performance improvement for TPP Bitola are provided to modernization and revitalization of turbines, generators and automation, revitalization and modernization of the boilers with NOx emissions reduction and revitalization of cooling towers, and revitalization for SOx, dust and particle emission reduction. Taking this into account in this paper some safety measures at work during the execution o...
a free-access multidisciplinary publication of the Faculty of Engineering Hunedoara 1. Abstract: ... more a free-access multidisciplinary publication of the Faculty of Engineering Hunedoara 1. Abstract: In this paper, some of the statistical indicators which refer to serious and fatal accidents at work in the European Union (EU-28) and in the Republic Macedonia are presented. The performed statistical analysis shows that the number of serious and fatal accidents at work in EU-28 and in the Republic Macedonia, in 2012 was decreased in comparison with 2008. Nevertheless, the Republic of Macedonia has high incidence rate for fatal accidents at work compared to highly develop European countries. The activities of public administration and defense, construction, manufacturing, transportation and storage sector and the activities of households as employers are the economic sectors in which it is possible to prevent injuries caused by serious accidents at work. Тhe activities of households as employers, construction sector, transportation and storage sector and agriculture, forestry and fishin...
This model explains the heat flow in a confined space with transparent walls (glass or plastic). ... more This model explains the heat flow in a confined space with transparent walls (glass or plastic). A software is used to analyze the behavior of transparent walls coated with "LLumar" film. This film has many advantages, but in this paper, we will focus on energy savings. Energy savings give quick return on investment and are considered a smart investment. Energy-saving LLumar film can increase performance of almost every window system, significantly reducing energy consumption and requirements. Professional energy audits have shown that buildings with LLumar film can achieve annual energy savings of up to 15%, blocks 99% of harmful UV rays and improves comfort by reducing heat and glare. Regardless of whether it is residential, commercial or glass house space as described in this paper, LLumar the world's leading brand of architectural film for decades improves the well-known buildings around the world with proven results. LLumar films will greatly increase energy effic...
In this paper the experimental results of far-infrared vacuum drying of apple slices were present... more In this paper the experimental results of far-infrared vacuum drying of apple slices were presented. The investigation of far-infrared vacuum drying processes was conducted on the experimental setup that was designed to imitate industrial batch dryer. Apple slices were dried at various vacuum pressures and temperatures of heaters which were kept constant during the single experiments. Five well known thin layer drying models from scientific literature were used to approximate the experimental data of drying kinetics in terms of moisture ratio. For each model and data set, the statistical performance index and chi-squared value were calculated and models were ranked afterwards. The performed statistical analysis shows that the model of Aghbashlo gives the best results for approximation of experimental drying data of apple slices. ARTICLE HISTORY
The moisture adsorption isotherms of pear were determined at 15 °C, 30 °C, and 45i°C using the st... more The moisture adsorption isotherms of pear were determined at 15 °C, 30 °C, and 45i°C using the standard static gravimetric method over a range of water activity from 0.112 to 0.920. The experimental data were fitted with isotherm equations recommended in ASAE Standard D245.5. In order to find which equation gives the best results, large number of numerical experiments were performed. After that, several statistical criteria proposed in scientific literature for estimation and selec-tion of the best sorption isotherm equations were used. For each equation and ex-perimental data set, the average performance index was calculated and models were ranked afterwards. After that, some statistical rejection criteria were checked (D'Agostino-Pearson test of normality, single-sample run test and significance and precision of the model parameters). The performed statistical analysis shows that the Guggenheim-Anderson-de Boer equation has the highest value of average per-formance index, but...
In this paper, the results of comparative analysis between transcendental and cyclometric sorptio... more In this paper, the results of comparative analysis between transcendental and cyclometric sorption isotherm models are presented. In order to find which model gives the best results, some numerical experiments were made. The experimental data set for equilibrium moisture content and the water activity for apple, pear, kiwi and banana at two different temperatures were used from the scientific literature. For each model and data set, several statistical parameters were calculated and models were ranked afterwards. The performed comparative analysis shows that the cyclometric models in many cases have higher values of the coefficient of determination, and lower values of the root mean squared error and the mean relative deviation than transcendental the isotherm models. All these results show that the cyclometric sorption isotherm models give the best overall fit to experimental data. After choosing the best transcendental and cyclometric model with the high value of statistical perfo...
In this paper, a new approach for selection of a thin-layer drying model based on serial statisti... more In this paper, a new approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. The experimental data set of thin-layer drying kinetics of apple slices at five different drying air temperatures (40, 60, 80, 100 and 120 C) and three drying air velocities (1, 2 and 3 ms-1) were obtained on the experimental setup, designed to imitate an industrial convective dryer. The drying data were fitted with twenty-three published thin-layer drying models (Lewis, Page, Modified Page, Henderson and Pabis, Modified Henderson and Pabis, Logarithmic(Asymptotic), Two term, Two term exponential, Midilli, Diffusion approach, Wang and Singh, Weibull, Aghbashlo, Verma., Grigorias, Parabolic, Hll, Demir, Logarithmic,Logistic, Vega-Lemus, Jena-Das and Alibas). In order to find which model gives the best results, some numerical experiments were made. For each model and data set, the performance index was calculated and models were ranked afterwards. After that, sev...
This paper describes the experimental results on the drying of the potato slices by infrared radi... more This paper describes the experimental results on the drying of the potato slices by infrared radiation under vacuum condition. The investigation of vacuum far-infrared drying processes was conducted on the experimental set-up that is designed to imitate industrial batch dryer. The experimental conditions have been chosen such that heaters’ temperature and vacuum chambers’ pressure have been in the range used on the industrial dryer. Potato slices were dried at various vacuum pressures (20, 40, 60 and 80 kPa) and temperatures (120, 140, 160, 180 and 200 C) which were kept constant during the single experiments. Based on experimental drying data, it was found that the drying time decreased with an increase of temperature of heaters and the decrease in the chamber pressure. It was also concluded that the influence of the temperature in vacuum chamber has more significant effect on reducing of the drying time than the vacuum pressure. Ten well known thin layer drying models from scienti...
In this paper the drying kinetics of far-infrared vacuum drying of some vegetables and fruits are... more In this paper the drying kinetics of far-infrared vacuum drying of some vegetables and fruits are presented. The experimental data of drying kinetics were obtained on experimental drying setup designed to imitate industrial dryer. Two well-known thin layer drying models from scientific literature were used to approximate the experimental data of drying kinetics in terms of moisture ratio. The performed statistical analysis shows that the model of Aghbashlo gives the best results for approximation of experimental drying data. ARTICLE HISTORY Received: 25.06.2017. Accepted: 11.08.2017. Available: 30.09.2017.
In this paper, a new approach for selection of a thin-layer drying model based on serial statisti... more In this paper, a new approach for selection of a thin-layer drying model based on serial statistical criteria was proposed. The experimental data set of thin-layer drying kinetics of apple slices at five different drying air temperatures (40, 60, 80, 100 and 120 o C) and three drying air velocities (1, 2 and 3 ms -1 ) were obtained on the experimental setup, designed to imitate an industrial convective dryer. The drying data were fitted with twenty-three published thin-layer drying models (Lewis, Page, Modified Page, Henderson and Pabis, Modified Henderson and Pabis, Logarithmic(Asymptotic), Two term, Two term exponential, Midilli, Diffusion approach, Wang and Singh, Weibull, Aghbashlo, Verma., Grigorias, Parabolic, Hll, Demir, Logarithmic,Logistic, Vega-Lemus, Jena-Das and Alibas). In order to find which model gives the best results, some numerical experiments were made. For each model and data set, the performance index was calculated and models were ranked afterwards. After that,...
Uploads
Papers by Vangelce Mitrevski