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Wyniki wyszukiwania dla: hyperbolic heat conduction
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Management of low-temperature heat source by ORC aided by additional heat source
PublikacjaIn the paper presented is a concept to utilize waste heat from the power plant with the aid of the low-temperature ORC cycle. The ORC system is heated from two heat sources, the first one being the flow rate of waste heat obtained from the exhaust gases. Subsequently, the working fluid in the cycle is additionally heated by the condensing steam from the low pressure turbine extraction points increasing in such way the level of...
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Heat transfer in plate heat exchanger channels: experimental validation of selected correlation equations
PublikacjaThis study is focused on experimental investigation of selected type of brazed plate heat exchanger. The Wilson approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The...
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Heat transfer in plate heat exchanger channels: experimental validation of selected correlation equations
PublikacjaThis study is focused on experimental investigation of selected type of brazed plate heat exchanger. The Wilson approach was applied in order to estimate heat transfer coefficients for the PHEx passages. The main aim of the paper was to experimentally check ability of several correlations published in the literature to predict heat transfer coefficients by comparison experimentally obtained data with appropriate predictions. The...
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Management of low-temperature heat source by ORC aided by additional heat source
PublikacjaThe presented work is aimed at utilisation of waste heat in the manner to produce electricity in ORC installation. Therefore the precondition of the study was to use the waste heat available in the form of a stream of hot water at 90°C. Such low enthalpy heat source is rather insufficient to produce a good quality vapour to feed the ORC turbine. That was the incentive to search for the ways of increasing the temperature of the...
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Heat Turbomachinery
Kursy OnlinePodstawowe informacje dotyczące obiegów cieplnych siłowni z turbinami parowymi i gazowymi. Główne elementy siłowni turbinowych. Zagadnienia przepływowe maszyn wirnikowych. Teoria stopni turbinowych. Część przepływowa turbin.
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Heat Turbomachinery
Kursy OnlinePodstawowe informacje dotyczące obiegów cieplnych siłowni z turbinami parowymi i gazowymi. Główne elementy siłowni turbinowych. Zagadnienia przepływowe maszyn wirnikowych. Teoria stopni turbinowych. Część przepływowa turbin.
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Heat Turbomachinery
Kursy Online -
Heat Turbomachinery
Kursy Online1. Steam turbine cycles. 2. Gas turbine cycles. 3. Combined gas-steam cycles. 4. Flows in nozzles. 5. Theory of turbine stages. 6. Multistage turbines. 7. Examples of turbine design.
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Heat Turbomachinery
Kursy OnlineZasady realizacji obiegów energetycznych. Obieg Carnota: grafy obiegu i przepływu ciepła. Porównanie sprawności obiegu parowego, gazowegi i kombinowanego. Obieg Joulea Braytona. Obieg Clausiusa Rankinea. Metody carnotyzacji obiegów. Obieg parowo gazowy. Wpływ nieodwracalności procesów na sprawność obiegu. Sprawność elektrowni. Funkcje zasadniczych elementów konstrukcyjnych turbin parowych i gazowych. Zasada działania stopnia turbiny....
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Heat turbomachinery
Kursy Online1. Steam turbine cycles. 2. Gas turbine cycles. 3. Combined gas-steam cycles. 4. Flows in nozzles. 5. Theory of turbine stages. 6. Multistage turbines. 7. Examples of turbine design.
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An facile Fortran-95 algorithm to simulate complex instabilities in three-dimensional hyperbolic systems
Dane BadawczeIt is well know that the simulation of fractional systems is a difficult task from all points of view. In particular, the computer implementation of numerical algorithms to simulate fractional systems of partial differential equations in three dimensions is a hard task which has no been solved satisfactorily. Here, we provide a Fortran-95 code to solve...
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Natural convective heat transfer from isothermal cuboids
PublikacjaThe paper presents results of theoretical and experimental investigations of the convective heat transfer from isothermal cuboid. The analytical solution was performed taking into account complete boundary layer length and the manner of its propagation around isothermal cuboid. It arises at horizontal bottom surface and grows on vertical lateral surface of the block. After changing its direction, the boundary layer occurs above...
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Flow distribution and heat transfer in minigap and minichannel heat exchangers during flow boiling
PublikacjaThe topic of boiling heat transfer in miniscale geometries has focused the ever increasing interest of researchers in recent years. However, most of the works are related to mini- and microchannels and much less to minigaps. Meanwhile, minigaps allow for more comprehensive experimental studies, i.e. flow visualisations due to the flat, two-dimensional configuration of the flow. The results of the experimental investigations of...
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A simplified energy dissipation based model of heat transfer for post-dryout flow boiling
Publikacjamodel for post dryout mist flow heat transfer is presented based on considerations of energy dissipation in the flow. The model is an extension of authors own model developed earlier for saturated and subcooled flow boiling. In the former version of the model the heat transfer coefficient for the liquid singlephase convection as a reference was used, due to the lack of the appropriate model for heat transfer coefficient for the...
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Numerical method of bicharacteristics for quasilinear hyperbolic functional differential systems
PublikacjaPraca dotyczy numerycznej aproksymacji rozwiązań zagadnień początkowo brzegowych dla układów quasiliniowych równań różniczkowo funkcyjnych pierwszego rzędu. Stosuje się metodę różnicową typu Eulera. Siatka otrzymywana jest za pomocą numerycznego rozwiązywania równań różniczkowo funkcyjnych bicharakterystyk.Stabilność schematu różnicowego jest dowodzona metodą porównawczą. O danych funkcjach zakłada się, że spełniają nieliniowe...
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Influence of metallic porous microlayer on pressure drop and heat transfer of stainless steel plate heat exchanger
PublikacjaThe experimental analysis of passive heat transfer intensification in the case of plate heat exchanger has been carried out. On the heat transfer surface of heat exchanger the metallic porous layer was created. The experiment was accomplished in two stages. In the first stage the commercial stainless steel gasketed plate heat exchanger was investigated, while in the second one – the identical heat exchanger but with the modified...
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Experimental study and comparison with predictive methods for flow boiling heat transfer coefficient of HFE7000
PublikacjaThis article describes an experimental study of flow boiling of HFE7000 inside a smooth vertical channel. The investigation has been carried out in a circular stainless-steel tube with an inner diameter of 2.3 mm. The data have been collected for the applied heat fluxes q ranging from 61 to 205 kW/m2, the mass flux G ranging from 214 to 1006 kg/(m2 s), the saturation temperature Tsat ranging from 30 to 54 °C and the full range...
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A new hyperbolic-polynomial higher-order elasticity theory for mechanics of thick FGM beams with imperfection in the material composition
PublikacjaA drawback to the material composition of thick functionally graded materials (FGM) beams is checked out in this research in conjunction with a novel hyperbolic‐polynomial higher‐order elasticity beam theory (HPET). The proposed beam model consists of a novel shape function for the distribution of shear stress deformation in the transverse coordinate. The beam theory also incorporates the stretching effect to present an indirect...
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Influence of metallic porous microlayer on pressure drop and heat transfer of stainless steel plate heat exchanger
PublikacjaThe experimental analysis of passive heat transfer intensification in the case of plate heat exchanger has been carried out. The metallic porous layer was created on the heat transfer surface of analyzed unit. The experiment was accomplished in two stages. In the first stage the commercial stainless steel gasketed plate heat exchanger was investigated, while in the second one – the identical heat exchanger but with the modified...
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Dariusz Mikielewicz prof. dr hab. inż.
OsobyDariusz Mikielewicz – urodził się 6 lutego 1967 roku w Gdańsku, w 1985r. zdał pomyślnie egzaminy wstępne na Wydział Budowy Maszyn Politechniki Gdańskiej, który ukończył z wynikiem bardzo dobrym w 1990 roku na specjalności Maszyny i Urządzenia Energetyczne. Zainteresowania pracą naukową skłoniły go do podjęcia badań na University of Manchester na wydziale mechanicznym i energetyki jądrowej (Mechanical and Nuclear Engineering Department)...
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Experimental study on single phase operation of microjet augmented heat exchanger with enhanced heat transfer surface
PublikacjaThe article presents experimental investigations on a prototype heat exchanger. Presented research is focused on combined active and passive enhancement techniques of surface modification and microjet impingement. The results were compared to reference plate heat exchanger without microjet impingement. The Wilson plot method was applied to determine the heat transfer coefficients in the single phase operation. The heat exchanger...
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Thermodynamic and geometrical characteristics of mixed convection heat transfer in the shell and coil tube heat exchanger with baffles
PublikacjaThe article presents passive heat transfer enhancement method in the form of baffles to increase the energy efficiency of the shell coil heat exchanger. Conducted literature review shows that, despite numer- ous studies, there is little work on the intensification of heat transfer at the shell side. Most of the work focuses on the impact of geometrical parameters of the coil itself. This article successfully proves that it is possible...
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Experimental investigations on heat transfer enhancement in shell coil heat exchanger with VARIABLE Baffles GEOMETRY
PublikacjaThe paper presents the possibility of using passive intensification of heat transfer in the form of baffles to increase the energy efficiency of the shell and coil heat exchanger. The experiment was carried out by using a modular coil heat exchanger in the form of an electric heater. Water was used as a working fluid with constant thermal-flow parameters at the inlet of the module. It should be noted that experiments were made...
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High-temperature heat pumps – new devices for heat recovery and production of technological steam
PublikacjaIn the paper, the original high temperature compressor based heat pump with a dry working fluid, i.e. the one in which the slope of saturated vapour line is positive, was presented. The objective of the paper is to investigate the possibility of preparation of technological steam with tempperature 120 C from the waste heat resource at temperature of 50 C. Single comppression cycles as well as cascade systems have been considered...
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Combined Heat & Power Generating Systems
PublikacjaSteam cycles in combined heat and power plants. Efficiency of combined heat and power systems. Characteristics of steam-turbine CHP plants. Choice of equipment in CHP generating systems. Economic effects of combined heat and power production. Costs and energy produced CHP generating systems. Future development trends in CHP generating systems.
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Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator
PublikacjaTwo-dimensional numerical investigations of the fluid flow and heat transfer have been carried out for the laminar flow of the louvered fin-plate heat exchanger, designed to work as an air-source heat pump evap- orator. The transferred heat and the pressure drop predicted by simulation have been compared with the corresponding experimental data taken from the literature. Two dimensional analyses of the louvered fins with varying...
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Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness
PublikacjaThe shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil,centrifugal force is acting on the moving fluid due to the curvature of thetube results in the development. It has been long recognized that the...
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Implicit difference methods for infinite systems of hyperbolic functional differential equations
PublikacjaPraca dotyczy klasycznych rozwiązań problemów początkowo brzegowych dla nieskończonych układów nieliniowych równań rózniczkowo funkcyjnych. Skonstruowane są dwa typy schematów różnicowych. Pokazujemy, ze rozwiązania rozważanego zagadnienia różniczkowego można przybliżyć przy pomocy rozwiązań nieskończonych układów równań różnicowych. W drugiej części pracy udowadniamy, że również rozwiązania skończonych układów równań różnicowych...
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Differential difference inequalities related to hyperbolic functional differential systems and applications
PublikacjaZagadnienie początkowo brzegowe dla ukadów quasiliniowych równań różniczkowo funkcyjnych przeksztacane jest w układ równań różniczkowych zwyczajnych poprzez dyskretyzację względem zmiennej przestrzennej. Podane są warunki wystarczające dla zbieżności metody prostych. Otrzymany układ równań różniczkowo funkcyjnych zwyczajnych jest rozwiązywany uwikłaną metodą różnicową. Zbieżność schematu różnicowego jest dowodzona metodą porównawczą....
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Caratheodory solutions to hyperbolic functional differential systems with state dependent delays
PublikacjaMetodą bicharakterystyk i metodą nierówności całkowych dowodzi się istnienia uogólnionych rozwiązań układów równań różniczkowo-funkcyjnych cząstkowych z odchylonym argumentem zależnym od funkcji niewiadomej.
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Experimental and Computational Fluid Dynamics Studies on Straight and U-Bend Double Tube Heat Exchangers with Active and Passive Enhancement Methods
PublikacjaIn this work, the authors wanted to demonstrate the possibility to increase the heat transfer efficiency by using simple wire coil inserts to create turbulent flow in the boundary layer as well as air blowing into the annulus of the pipe. Experimental investigations were carried out for four heat exchanger constructions, i.e., plain double tube, turbulized double tube, plain U-bend double tube, U-tube with turbulator, plain double...
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Heat exchange enhancement of jet impingement cooling with the novel humped-cone heat sink
PublikacjaJet impingement cooling technology is applicable to control temperature of devices, where very high heat flux is generated within a small area. This paper is about the improvement of the jet impingement cooling efficiency by the heat sink geometry modification. Two reference cases were sourced from the literature – flat heat sink and modified one with cone in the jet stagnation region. Such a change improves cooling capability...
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Experimental investigation of heat transfer enhancement in straight and U-bend double-pipe heat exchanger with wire insert
PublikacjaIn this paper, the possibility of heat transfer enhancement in the U-bend exchanger was presented. Experimental research has been carried out for four individual heat exchanger constructions i.e. plain tube in tube, turbulized tube in tube, plain U-bend and U-bend with turbulator. Also, heat transfer experiments for various boundary conditions were performed to obtain reference values. In case of U-bend exchanger with and without...
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Experimental study of flow boiling pressure drop and heat transfer of R1233zd(E) at moderate and high saturation temperatures
PublikacjaThe paper presents the results of experimental study of flow boiling of R1233zd(E) in minichannel at moderate and high saturation temperatures. The heat transfer coefficient and pressure drop were measured for flow boiling in a stainless steel tube with 2 mm inside diameter and a length of 300 mm. Experiment has been conducted for saturation temperatures ranging from 83 to 145 °C which corresponds to values of reduced pressures...
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A new construction of shell-and-tube heat exchanger with impinging jets and minichannels technologies for heat recovery from gases – experimental analysis
PublikacjaA dynamic development of technologies allowing waste heat utilization is observed in a correspondence with a pro-ecological approach of the zero waste idea. Such approach becomes the most demanding in the area of low-temperature was heat sources, especially gaseous media. Till now, they were usually not utilized due to unfavorable thermal conditions and high costs. Therefore, the zero waste approach directs research on techniques...
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Utilisation of waste heat from the power plant by use of the ORC aided with bleed steam and extra source of heat
PublikacjaUtilization of waste heat recovered from the exhaust gases of the power generation unit by means of ORC (organic Rankine cycles) installation is considered. The waste heat is available in the form of a stream of hot water having temperature of 90 stC in the amount of 200 MWt. To increase evaporation temperaturę of ORC working fluid the heat of steam from the extraction points from the low-pressure part of steam turbine is used....
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Co-simulation strategy of transient CFD and heat transfer in building thermal envelope based on calibrated heat transfer coefficients
PublikacjaThe paper presents a strategy to develop a fully transient numerical model of a heat transfer in building, using a transient CFD model of indoor air and a thermal envelope model, running in a co-simulation. The strategy relies on the utilization of RANS with a high-Re turbulence model and a wall function, which enables to use a coarse computational mesh limiting the computational time. Since wall functions give invalid heat transfer...
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Heat Turbomachinery 2023_24
Kursy OnlineBasics of thermodynamical cycles. Elements of turbine power plants. Fluid problems in turbomachinery. Theory of turbine stages. Turbine flow parts.
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Heat Transfer During Pool Boiling of Water, Methanol and R141b on Porous Coated Horizontal Tube Bundles
PublikacjaThis paper presents the results of experimental investigation of water, methanol and R141b refrigerant boiling on horizontal porous coated tube bundles supposed to represent a flooded-type evaporator. Experiments were carried out for a bundle of 19 tubes in triangular layout for two pitch-to-diameter ratio values – 1.7 and 2.0 – in atmospheric and sub-atmospheric pressure conditions. Average heat transfer coefficients – both local,...
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New trends in development of micro heat exchangers for ORC's
PublikacjaIn the paper, new trends in development of micro heat exchangers for CHP are presented. Main attention is concentrated on the question, how channels size and thermal development lenght affect the heat transfer. New types of micro heat exchangers developed at the Institute of Fluid-Flow Machinery PAS and the methoda of their design are presented. The new experimental testing methods of the micro-channel heat exchangers, new algorithms...
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Heat transfer of two-interacting microjets
PublikacjaThe present paper paid particular attention to the flow and heat transfer performance for two microjets impinging upon the heated surface by means of experimental investigations.
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A New Approach for the Mitigating of Flow Maldistribution in Parallel Microchannel Heat Sink
PublikacjaThe problem of flow maldistribution is very critical in microchannel heat sinks (MCHS). It induces temperature nonuniformity, which may ultimately lead to the breakdown of associated system. In the present communication, a novel approach for the mitigation of flow maldistribution problem in parallel MCHS has been proposed using variable width microchannels. Numerical simulation of copper made parallel MCHS consisting of 25 channels...
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Stability of difference problems generated by hyperbolic first order partial differential systems.
PublikacjaPraca dotyczy numerycznej aproksymacji rozwiązań zagadnień początkowych dla nieliniowych układów równań różniczkowych cząstkowych pierwszego rzędu. Podano konstrukcję układu quasiliniowego równań różnicowych typu Eulera. Wykazano, że przy naturalnych założeniach jest on stabilny. Dowód zbieżności wykorzystuje metody porównawcze.
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Analytical model with non-adiabatic effects for pressure drop and heat transfer during boiling and condensation flows in conventional channels and minichannels
PublikacjaIn the paper a method developed earlier by authors is applied to calculations of pressure drop and heat transfer coefficient for boiling flow and condensation flow with account of non- adiabatic effects for some recent data collected from literature. The first effect, the modification of interface shear stresses in annular flow pattern is considered through incorporation of the so called "blowing parameter". The mechanism of...
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Electronic conduction in (Bi,Pb)-Sr-Ca-Cu-O granular superconductors
PublikacjaMetale i nadprzewodniki granulaste są bardzo ciekawymi materiałami dzięki jednoczesnej obecności oddziaływań kulombowskich, tunelowania elektronów i par Coopera oraz różnych zjawisk związanych z nieuporządkowaniem. W pracy przedstawiono właściwości elektryczne granulastego nadprzewodnika (Bi,Pb)-Sr-Ca-Cu-O otrzymanego wskutek krystalizacji w fazie stałej. Badane materiały mogą być traktowane jako układ granul umieszczonych w matrycy...
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Electronic conduction in (Bi,Pb)–Sr–Ca–Cu–O glass-ceramics
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Electronic conduction in (Bi,Pb)-Sr-Ca-Cu-O glass-ceramics
PublikacjaAmorficzny materiał (Bi,Pb)4Sr3Ca3Cu4Ox wygrzewany w odpowiednich warunkach staje się nieuporządkowanym metalem i nadprzewodnikiem. Przedstawiono model mechanizmu przewodnictwa elektrycznego tych materiałów. Przeprowadzono dyskusję istniejących teorii do opisu badanych materiałów.
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An experimental investigation on the effect of new continuous core-baffle geometry on the mixed convection heat transfer in shell and coil heat exchanger
PublikacjaIn the article, the authors presented the influence of continuous core-baffle geometry at mixed convection heat transfer in shell and coil heat exchanger. Experiments were carried out for a large power range, i.e. from 100W to 1200W and mass flow rates ranging from 0.01 kg/s to 0.025 kg/s. During the experiments, the mass flow rate of cooling water, the temperature of water at the inlet and outlet as well as the wall temperature...
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Possibility of thermal imaging use in studies of natural convection heat transfer on the example of an isothermal vertical plate.
PublikacjaA new method of infrared (IR) camera use in convective heat transfer studies has been presented. Until now, IR cameras were utilized for temperature field visualizations of flat heated surfaces of solid objects only. Because liquids and gasses do not emit radiation in the infrared range of wave lengths, detection of temperature field in the air was conducted with the use of plastic mesh, which, after heating by hot air, emits infrared...
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Heat and mass transport
Kursy OnlineCelem przedmiotu jest przekazanie wiedzy o podstawowych mechanizmach i prawach procesów transportu ciepła i masy, pozwalającej na rozwiązywanie inżynierskich problemów związanych z projektowaniem urządzeń i aparatury wymiany ciepła i masy.