Projektovanje i optimizacija rashladnih postrojenja u prehrambenoj industriji

U svim oblastima prehrambene industrije primenjuju se rashladna postrojenja. Rashladna postrojenja su kompleksni i skupi termoenergetski sistemi, pa je stoga bitno za svakog prehrambenog tehnologa da razume osnovne principe rada ovih uredaja, a takode i da bude sposaban da projektuje rashladno postrojenje i da na osnovu kapaciteta postrojenja izabere opremu koja ce biti efikasna da zadovolji zahtevane tehnološke parametre, a sa druge strane da bude i ekonomski prihvatljiva. Kurs ce obuhvatiti teoretska i prakticna iskustva o principima rada rashladnih postrojenja, kao i najnovije trendove u ovoj oblasti. Polaznici ce proširiti saznanja o materijalnim i energetskim bilansima u rashladnim postrojenjima, opremi koja se upotrebljava u rashladnim postrojenjima, vrstama izolacionih materijala, automatizaciji opreme u rashladnim postrojenjima, kondicioniranju vazduha u rashladnim sistemima i nacinima zamrzavanja pojedinih prehrambenih proizvoda

Modeling of thermoelectric module operation in inhomogeneous transient temperature field using finite element method

This paper is the result of research and operation modeling of the new systems for cooling of cutting tools based on thermoelectric module. A copper inlay with thermoelectric module on the back side was added to a standard turning tool for metal processing. For modeling and simulating the operation of thermoelectric module, finite element method was used as a method for successful solving the problems of inhomogeneous transient temperature field on the cutting tip of lathe knives. Developed mathematical model is implemented in the software package PAK-T through which numerical results are obtained. Experimental research was done in different conditions of thermoelectric module operation. Cooling of the hot module side was done by a heat exchanger based on fluid using automatic temperature regulator. After the calculation is done, numerical results are in good agreement with experimental. It can be concluded that developed mathe-matical model can be used successfully for modeling of cooling of cutting tools

Wear resistance of layers hard faced by the high-alloyed filler metal

The objective of this work was to determine the wear resistance of layers hard faced by the high-alloyed filler metal, with or without the austenite inter-layer, on parts that operate at different sliding speeds in conditions without lubrication. The samples were hard faced with the filler metal E 10-UM-60-C with high content of C, Cr and W. Used filler metal belongs into group of alloys aimed for reparatory hard facing of parts damaged by abrasive and erosive wear and it is characterized by high hardness and wear resistance. In experiments, the sliding speed and the normal loading were varied and the wear scar was monitored, based on which the volume of the worn material was calculated analytically. The contact duration time was monitored over the sliding path of 300 mm. The most intensive wear was established for the loading force of 100 N and the sliding speed of 1 m.s-1, though the significant wear was also noticed in conditions of the small loading and speed of 0.25 m.s-1, which was even greater that at larger speeds.

Wear resistance of layers hard faced by the high-alloyed filler metal

The objective of this work was to determine the wear resistance of layers hard faced by the high-alloyed filler metal, with or without the austenite inter-layer, on parts that operate at different sliding speeds in conditions without lubrication. The samples were hard faced with the filler metal E 10-UM-60-C with high content of C, Cr and W. Used filler metal belongs into group of alloys aimed for reparatory hard facing of parts damaged by abrasive and erosive wear and it is characterized by high hardness and wear resistance. In experiments, the sliding speed and the normal loading were varied and the wear scar was monitored, based on which the volume of the worn material was calculated analytically. The contact duration time was monitored over the sliding path of 300 mm. The most intensive wear was established for the loading force of 100 N and the sliding speed of 1 m.s-1, though the significant wear was also noticed in conditions of the small loading and speed of 0.25 m.s-1, which was even greater that at larger speeds.

Uticaj termičkog tretmana na higijenski kvalitet mleka

In the conducted study, the influence of the pasteurization and sterilization regime on the hygienic quality of raw and thermally treated milk was analyzed. Tests were conducted in the dairy "MEGGLE Srbija, doo" in Kragujevac. The following methods of thermal treatment were applied: short-term HTST pasteurization of raw milk at 75ºC, high HTST pasteurization of raw milk at 95ºC and flow-through UHT sterilization at 139ºC of previously pasteurized milk at 75ºC. The efficiency of thermal treatments on the hygienic quality of milk was determined by the following microbiological analyzes: by determining the total number of bacteria by the indirect method by Koch and by the internal analysis method applied in the dairy "MEGGLE Srbija, doo". Based on the tests carried out, a significant reduction in the number of bacteria after the pasteurization process of milk samples and their complete inhibition after the sterilization process was determined.U sprovedenom ispitivanju analiziran je uticaj režima pasterizacije i sterilizacije na higijenski kvalitetet sirovog i termički tretiranog mleka. Ispitivanja su obavljena u mlekari „MEGGLE Srbija, d.o.o.“ u Kragujevcu. Primenjene su sledeće metode termičke obrade: kratkotrajna HTST pasterizacija sirovog mleka na 75ºC, visoka HTST pasterizacija sirovog mleka na 95ºC i protočna UHT sterilizacija na 139ºC prethodno pasterizovanog mleka na 75ºC. Efikasnost termičkih tretmana na higijenski kvalitet mleka utvrđivana je sledećim mikrobiološkim analizama: određivanjem ukupnog broja bakterija indirektnom metodom po Koch-u i metodom interne analize koja se primenjuje u mlekari „MEGGLE Srbija, d.o.o.“. Na osnovu obavljenih ispitivanja ustanovljena je značajna redukcija broja bakterija nakon procesa pasterizacije uzoraka mleka i njihova potpuna inhibicija nakon procesa sterilizacije

A novel framework for fluid/structure interaction in rapid subjectspecific simulations of blood flow in coronary artery bifurcations

Background/Aim. Practical difficulties, particularly long model development time, have limited the types and applicability of computational fluid dynamics simulations in numerical modeling of blood flow in serial manner. In these simulations, the most revealing flow parameters are the endothelial shear stress distribution and oscillatory shear index. The aim of this study was analyze their role in the diagnosis of the occurrence and prognosis of plaque development in coronary artery bifurcations. Methods. We developed a novel modeling technique for rapid cardiovascular hemodynamic simulations taking into account interactions between fluid domain (blood) and solid domain (artery wall). Two numerical models that represent the observed subdomains of an arbitrary patient-specific coronary artery bifurcation were created using multi-slice computed tomography (MSCT) coronagraphy and ultrasound measurements of blood velocity. Coronary flow using an in-house finite element solver PAK-FS was solved. Results. Overall behavior of coronary artery bifurcation during one cardiac cycle is described by: velocity, pressure, endothelial shear stress, oscillatory shear index, stress in arterial wall and nodal displacements. The places where (a) endothelial shear stress is less than 1.5, and (b) oscillatory shear index is very small (close or equal to 0) are prone to plaque genesis. Conclusion. Finite element simulation of fluid-structure interaction was used to investigate patient-specific flow dynamics and wall mechanics at coronary artery bifurcations. Simulation model revealed that lateral walls of the main branch and lateral walls distal to the carina are exposed to low endothelial shear stress which is a predilection site for development of atherosclerosis. This conclusion is confirmed by the low values of oscillatory shear index in those places

Spirulina Phycobiliproteins as Food Components and Complements

Spirulina has a documented history of use as a food for more than 1000 years, and has been in production as a dietary supplement for 40 years. Among many of Spirulina bioactive components, blue protein C-phycocyanin and its linear tetrapyrrole chromophore phycocyanobilin occupy a special place due to broad possibilities for application in various areas of food technology. The subject of this chapter is up-to-date food applications of these Spirulina components, with a focus on their use as food colorants, additives, nutriceuticals, and dietary supplements. Their other actual and future food application possibilities will also be briefly presented and discussed