Peculiarities of temperature fields formation in vapor channels of thermosyphons with heat carriers boiling at low temperatures

We conducted experiments on specially developed setup consisting of evaporation, transport and condensation parts. Heat was supplied to the evaporation part by the heating element which was supplied with voltage and alternating current from a single-phase transformer. Temperatures in the characteristic sections of each part were recorded by thermocouples. Junctions of thermocouples were mounted on the axis of symmetry in the liquid layer, at the lower boundary, in the middle part, and at the upper boundary of the vapor channel. To minimize the influence of the random factors (ambient air movement, operation of ventilation system, room temperature, etc.), we placed thermosyphon in a glass box. We used N-pentane as a heat carrier, and the filling ratio of the thermosyphon is equal to 4%

Critical heat flux density in diphasic thermosyphons

The paper presents an analysis of known dependencies for determining the critical heat flux density in diphasic thermosyphons. The critical heat flux density for the created experimental model of thermosyphon were calculated on the basis of the theoretical contributions of 1) the occurrence of a “flooding” regime in a thermosyphon characterized by a disturbance of the hydrodynamic stability of the phase interface and the entrainment of the liquid phase by the gas flow; 2) the mutual influence of gravitational forces and surface tension; 3) S.S. Kutateladze hydrodynamic theory of the heat transfer crisis during boiling. It is found that the existing theoretical contributions which can be used to calculate the critical heat flux density and subsequently determine the minimum filling ratio of a thermosyphon are conditionally applicable

Experimental Investigation of the Contact Angle at Wetting the Non-ferrous Metals

Experimental dependences on the effect of the drop volume from the contact angle under the conditions of the static three-phase contact line formation during wetting the non-ferrous metals (aluminium, magnalium, copper and brass) are presented in the work. The surface of the substrates was investigated by modern equipment (profilometer "Micro Measure 3D station" and microscope TM-3000). The drop was placed on the surface by the precision electronic single-channel pipette (Thermo scientific). Shadow method was used to obtain the drop profile; symmetry of the drop was controlled by Schlieren method. The comparison of the methods used to determine the contact angle on the image of the drop profile was executed. It was established that in spite of influencing the friction and gravity forces the structure of metal surfaces affects greatly the value of the contact angle

An experimental study of the influence of a thermosyphon filling ratio on a temperature distribution in characteristic points along the vapor channel height

Results of experimental studies of heat transfer in a thermosyphon illustrating the influence of the filling ratio and the heat load on the temperature distribution in the vapor channel, evaporation and condensation zones are presented. The thermosyphon was made of copper and was 161 mm high with side walls 1.5 mm thick, bottom cover 2 mm thick, an internal dimmer of the evaporation part of 54 mm and an internal diameter of the vapor channel of 39.2 mm. Based on the results of experimental studies, temperature dependences were established in the characteristic cross sections of the thermosyphon on the heat flux value supplied to the bottom cover. In addition, a well-appearing thermosyphon self-regulation property has been found – the growth of the heat load in the evaporation zone in the range from 1940 to 7685 W/m{2} does not lead to a decrease in the heat removal intensity from the heat-release region

Critical heat flux density in diphasic thermosyphons

The paper presents an analysis of known dependencies for determining the critical heat flux density in diphasic thermosyphons. The critical heat flux density for the created experimental model of thermosyphon were calculated on the basis of the theoretical contributions of 1) the occurrence of a “flooding” regime in a thermosyphon characterized by a disturbance of the hydrodynamic stability of the phase interface and the entrainment of the liquid phase by the gas flow; 2) the mutual influence of gravitational forces and surface tension; 3) S.S. Kutateladze hydrodynamic theory of the heat transfer crisis during boiling. It is found that the existing theoretical contributions which can be used to calculate the critical heat flux density and subsequently determine the minimum filling ratio of a thermosyphon are conditionally applicable

Experimental Research of Wetting and Drop Evaporation Processes on a Heated Substrate as a Method for Research Skills Development for Heat and Power Engineering Students

The article considers a method used for student research competency development during the course “Process energy sources for industrial facilities” in Tomsk Polytechnic University. The experiment is based on shadow and Schlieren optical methods for observing the water drop evaporation on the solid surface. Using the images obtained by plane-parallel light during the evaporation process and Drop Shape analyses software, students are to determine the drop's geometric parameters. After the experiment and results processing, they are required to determine the evaporation stages, study effects of surface roughness and temperature factors on characteristics of drop spreading (contact angle and diameter)

Forced spreading over superhydrophobic and copper surfaces

Dynamic spreading over superhydrophobic and copper surfaces was studied experimentally under the condition of contact line movement with speed greater than 1 mm/sec. Three modes of spreading of distilled water drop over copper surfaces with sufficient typical roughness (0.591, 5.190 and 6.210 μM) were detected. The first one is drop formation when the contact line speed and dynamic contact angle increase sharply. The second mode is spreading of a drop, which is characterized by a monotonic decrease in the contact line speed and dynamic contact angle. The third one is a formation of an equilibrium contact angle at a constant wetted area (the contact line speed tends to zero, and spreading of a drop occurs as long as the driving force is greater than zero). Some features in spreading were detected on superhydrophobic surface with parameter roughness of 0.751μm compared to other substrates. During drop formation after sharp increase in the contact line speed and dynamic contact angle, there is a mode which is accompanied by a decrease in the contact line speed and monotonic increase in the advancing dynamic contact angle

Checklist of longicorn beetles (Coleoptera, Cerambycidae) of Omsk Region (Russia)

An annotated check-list of the longicorn beetles of Omsk Region is given. The list based on literature data and collecting materials of authors. 41 species are new to the fauna of Omsk Region

Complex microwave processing of high-ash brown coal in relation to the energy and metallurgical industries

Relevance. The need of the Tomsk region for valuable energy resources obtained from local low-grade resources to develop iron ore deposits available in the region and cover energy needs. Aim. To study gaseous and solid products obtained from low-grade brown coal of the Talovsky deposit (Tomsk region) under microwave pyrolysis conditions in relation to the energy and metallurgical industries. Objects. Brown coal of the Talovsky deposit (Tomsk region). Methods. Certified SS methods to determine thermal characteristics and elemental composition of coal organic and mineral parts, the "transmission-reflection" method for measuring imaginary (ε'') and real (ε') components of the complex dielectric permittivity, physical experiment, gas analysis, Brunauer–Emmett–Teller method for measuring texture characteristics. Results. Brown coal of the Talovsky deposit has high values of moisture and ash contents for operating conditions, which leads to a low calorific value. Such characteristics make it possible to classify coal as a low-grade fuel, which indicates the inexpediency of its use as a raw material for the energy and metallurgical industries. Thermal processing by means of microwave pyrolysis makes it possible to obtain a high-calorie (heat of combustion over 21 MJ/m3) and environmentally friendly (hydrogen content over 29%) gaseous fuel from the low-grade brown coal of the Talovsky deposit. The resulting solid carbonaceous residue has an ash content of over 48%, which required its chemical treatment in a solution of HF and HCl. As a result of the solid carbonaceous residue treatment, its ash content decreased by more than 38%, the sulfur content – by more than 1.5 times. According to its characteristics, the resulting product corresponds to the currently available carbonaceous products – semi-coke, coke and carbon reducing agent for ferroalloy production

External Economic Balance of the Russian Federation

Daná práce se zabývá posouzením vnější ekonomické rovnováhy Ruské federace v období 2000-2016. Je rozdělena na tři základní části. V první části jsou obsazeny základní teoretické poznatky týkající se struktury platební bilance, mezinárodní investiční pozice a zahraniční zadluženosti. Ostatní části jsou praktické. V druhé kapitole je zanalyzován vývoj platební bilance, mezinárodní investiční pozice a zahraniční zadluženosti Ruska za sledované období, vysvětleny příčiny daného vývoje. Poslední část je pak zaměřena na kritické zhodnocení vnější ekonomické rovnováhy Ruska s použitím řady kritérií a znalostí získaných z analýzy statistických výkazů v předchozí kapitole.This thesis deals with the assessment of the external economic balance of the Russian Federation for the period 2000-2016. It is divided into three basic parts. The first part contains basic theoretical knowledge on the structure of balance of payments, international investment position and external debt. The other parts are practical. The second chapter analyzes the development of the Russian's balance of payments, international investment position and external debt over the monitored period, explaining the reasons for such development. The last part is focused on the critical assessment of Russia's external economic balance using a number of criteria and knowledge gained from the analysis of the statistical statements in the previous chapter