Search
Filters
total: 1731
filtered: 1440
displaying 1000 best results Help
Search results for: loop heat pipe
-
Combined Heat & Power Generating Systems
PublicationSteam 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.
-
Parametric study of fluid flow and heat transfer over louvered fins of air heat pump evaporator
PublicationTwo-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...
-
Augmented speed control scheme of dual induction motors with mutual flux angle control loop
PublicationThis paper proposes an augmented speed control scheme of dual induction motors fed by a five-leg voltage source inverter (VSI) with a common/shared-leg. An additional control loop is proposed here and based on the mutual flux angle – the difference between flux angular positions of the IMs. The main purpose of this research is to minimize the energy losses in the common inverter leg by controlling the mutual flux angle, at equal...
-
Heat exchange enhancement of jet impingement cooling with the novel humped-cone heat sink
PublicationJet 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...
-
Experimental study of flow boiling pressure drop and heat transfer of R1233zd(E) at moderate and high saturation temperatures
PublicationThe 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...
-
Miniaturized Dual-Band SIW-Based Bandpass Filters Using Open-Loop Ring Resonators
PublicationThis article presents two novel architectures of dual-band substrate integrated waveguide (SIW) bandpass filters (BPFs). Initially, two identical open-loop ring resonators (OLRRs) are coupled face-to-face on the top of the SIW cavity to realize a dual-band single-pole BPF. To obtain two-pole dual-band characteristics, two OLRRs resonant units are assembled horizontally within the top metal layer of the SIW, which is a technique...
-
Analytical solution of non-stationary heat conduction problem for two sliding layers with time-dependent friction conditions
PublicationIn this article we conduct an overview of various types of thermal contact conditions at the sliding interface. We formulate a problem of non-stationary heat conduction in two sliding layers with generalized thermal contact conditions allowing for dependence of the heat-generation coefficient and contact heat transfer coefficient on time. We then derive an analytical solution of the problem by constructing a special coordinate...
-
Compensation of supply current harmonics, reactive power, and unbalanced load current balance in the closed-loop control of a shunt active power filter
PublicationThis paper presents the compensation tasks performed by a shunt active power filter, including compensation of harmonic currents, reactive power, and an unbalanced load current. The paper demonstrates novel control of the shunt active power filter in a closed-loop system. The control algorithm was verified by performing simulations and compared the simulated results with those obtained in an open-loop control system. All simulations...
-
A new construction of shell-and-tube heat exchanger with impinging jets and minichannels technologies for heat recovery from gases – experimental analysis
PublicationA 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...
-
Two-phase optimizing approach to design assessments of long distance heat transportation for CHP systems
PublicationCogeneration or Combined Heat and Power (CHP) for power plants is a method of putting to use waste heat which would be otherwise released to the environment. This allows the increase in thermodynamic efficiency of the plant and can be a source of environmental friendly heat for District Heating (DH). In the paper CHP for Nuclear Power Plant (NPP) is analyzed with the focus on heat transportation. A method for effectivity and feasibility...
-
The Laser Processing of the Stainless-Steel Surface Layer of a Heat Exchanger Membrane in Order to Enhance Its Heat Transfer Coefficient
PublicationResearch on temperature regulation is essential for ensuring thermal comfort and optimizing machine performance. Effective cooling systems are critical in industrial processes and everyday electronic devices in order to prevent overheating. Laser-modified heat exchangers can enhance heat dissipation without increasing weight, addressing the need for energy-efficient solutions in the market. The main aim of this experimental research...
-
Mechanical-Level Hardware-In-The-Loop and Simulation in Validation Testing of Prototype Tower Crane Drives
PublicationIn this paper, the static and dynamic simulations, and mechanical-level Hardware-In-the-Loop (MHIL) laboratory testing methodology of prototype drive systems with energy-saving permanent-magnet electric motors, intended for use in modern construction cranes is proposed and described. This research was aimed at designing and constructing a new type of tower crane by Krupiński Cranes Company. The described research stage was necessary...
-
Utilisation of waste heat from the power plant by use of the ORC aided with bleed steam and extra source of heat
PublicationUtilization 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....
-
Numerical aspects of improvement of the unsteady pipe flow equations
PublicationW pracy dokonano analizy zaproponowanych w ostatnich latach metod opisu oporów ruchu w przepływie nieustalonym w przewodach pod ciśnieniem. Wykazano,że modyfikacja współczynnika oporów liniowych nie może zapewnić pozytywnych efektów oraz ,że poprawa wyników wykazywana przez autorów modyfikacji wynika z błędu dyfuzji numerycznej generowanej przez metodę rozwiązania.
-
Multimode tapered optical light pipe for illumination systems
Publication -
Method of earth fault loop impedance measurement without nuisance tripping of RCDs in 3-phase low-voltage circuits
PublicationVerification of electrical safety in low-voltage power systems includes the measurement of earth fault loop impedance. This measurement is performed to verify the effectiveness of protection against indirect contact. The widespread classic methods and meters use a relatively high value of the measuring current (5–20) A, so that they are a source of nuisance tripping of residual current devices (RCDs). The meters dedicated to circuits...
-
Co-simulation strategy of transient CFD and heat transfer in building thermal envelope based on calibrated heat transfer coefficients
PublicationThe 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...
-
Heat Transfer During Pool Boiling of Water, Methanol and R141b on Porous Coated Horizontal Tube Bundles
PublicationThis 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,...
-
New trends in development of micro heat exchangers for ORC's
PublicationIn 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...
-
Heat transfer of two-interacting microjets
PublicationThe 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.
-
Cattaneo–Christov heat flow model for copper–water nanofluid heat transfer under Marangoni convection and slip conditions
PublicationThis report is devoted to the study of the flow of MHD nanofluids through a vertical porous plate with a temperature-dependent surface tension using the Cattaneo–Christov heat flow model. The energy equation was formulated using the Cattaneo–Christov heat flux model instead of Fourier’s law of heat conduction. The Tiwari–Das model was used to take into account the concentration of nanoparticles when constructing the momentum equation....
-
A New Approach for the Mitigating of Flow Maldistribution in Parallel Microchannel Heat Sink
PublicationThe 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...
-
Analytical model with non-adiabatic effects for pressure drop and heat transfer during boiling and condensation flows in conventional channels and minichannels
PublicationIn 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...
-
Possibility of thermal imaging use in studies of natural convection heat transfer on the example of an isothermal vertical plate.
PublicationA 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...
-
An experimental investigation on the effect of new continuous core-baffle geometry on the mixed convection heat transfer in shell and coil heat exchanger
PublicationIn 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...
-
An oscillation-based built-in test scheme with AGC loop.
PublicationPrzedstawiono oscylacyjny tester wbudowany (OBIT) do testowania części analogowej elektronicznego układu mieszanego sygnałowo zmontowanego na pakiecie. W celu zwiększenia współczynnika pokrycia uszkodzeń, w testerze zastosowano pomiary w dziedzinie czasu i częstotliwości. Omówiono wybrane aspekty implementacji testera, w szczególności problem transformacji układu testowanego w oscylator. Przeprowadzono analizę stanu ustalonego...
-
Hardware-in-the-loop simulation of the synchronization process of power generators
PublicationPrzedstawiono nowoczesne urządzenia do badań synchronizatorów automatycznych w warunkach laboratoryjnych. Szczególną uwagę poświęcono systemowi wizualizacji tych urządzeń )przy ich pomocymożliwa jest ciągła kontrola, sterowanie i wizualizacja procesem synchronizacji w systemie elektroenergetycznym.
-
Influence of control loop on torsional vibrations of rotating machinery.
PublicationRozpatrywano wpływ pętli regulacyjnej silnika diesla na dynamikę układu napędowego okrętowego. Porównano obliczenia numeryczne z badaniami eksperymentalnymi. Stwierdzono duży wpływ pętli regulacyjnej silnika diesla na dynamikę układu. W obliczeniach numerycznych skoncentrowano się na drganiach skrętnych układu napędowego okrętowego. Analizowano wpływ sztywności skrętnej sprzęgła elastycznego na amplitudy momentów skrętnych...
-
Green function diagonal for a class of heat equations
PublicationA construction of the heat kernel diagonal is considered as element of generalized zeta function theory, which gradient at the origin defines determinant of a differential operator in a technique for regularizing quadratic path integral. Some classes of explicit expressions of the Green function in the case of finite-gap potential coefficient of the heat equation are constructed. An algorithm and program for Mathematica are presented...
-
Turbulence model evaluation for numerical modelling of turbulent flow and heat transfer of nanofluids
PublicationIn this work, Nusselt number and friction factor are calculated numerically for turbulent pipe flow (Reynolds number between 6000 and 12000) with constant heat flux boundary condition using nanofluids. The nanofluid is modelled with the single-phase approach and the simulation results are compared with experimental data. Ethylene glycol and water, 60:40 EG/W mass ratio, as base fluid and SiO2 nanoparticles are used as nanofluid...
-
A review of phase change materials and heat enhancement methodologies
PublicationPhase change materials (PCMs) are an efficient alternative to store and release heat at a specific range of temperature. Here PCMs and heat enhancement methodologies for PCM storage are reviewed. A short overview of PCMs and their applications is presented in addition to the progress during the last 10 years. Heat enhancement techniques, that is, extended surfaces, multiple and composite PCMs, and encapsulation techniques, are...
-
Thermal-Hydraulic Studies on the Shell-and-Tube Heat Exchanger with Minijets
PublicationIn this paper a patented design of a heat exchanger with minijets, with a cylindrical construction is presented. It is followed by the results of its systematic experimental investigations in the single-phase convection heat transfer mode. Based on these results, validation of selected correlations (coming from the literature) describing the Nusselt number was carried out. An assessment of the heat exchange intensification level...
-
The improvement of axial bearing capacity of open-end pipe piles
PublicationZaproponowano sposób zwiększania nośności osiowej pali rurowych z otwartym dnem za pomocą wewnętrznych pierścieni. Przedstawiono wyniki badań w skali naturalnej i badań modelowych. Przeprowadzono analizę teoretyczną zjawiska metodą analityczną i numeryczną. Badania i analizy potwierdziły skuteczność proponowanego rozwiązania technicznego.
-
Optimization of Quantitative Analysis of Biofilm Cell from Pipe Materials
Publication -
A Study on the Residual Stress of Seam Pipe Cutting and Girth Welding
Publication -
Hydraulic transients analysis in pipe networks by the method of characteristics (MOC)
PublicationW pracy przedstawiono wyniki badań eksperymentalnych i analizy numerycznej zjawiska przepływów nieustalonych w przewodach pojedynczych oraz symulacji numerycznych w sieci pierścieniowej. Model matematyczny stanowi układ dwóch równań różniczkowych cząstkowych typu hiperbolicznego, które rozwiązano za pomocą metody charakterystyk. Badania eksperymentalne przeprowadzono na modelu w skali laboratoryjnej. Uzyskano dobrą zgodność obliczeń...
-
Water hammer analysis in pipe networks by the method of characteristics (MOC).
PublicationZastosowano w pracy metodę charakterystyk do analizy zjawiska uderzenia hydraulicznego w sieci wodociągowej pierścieniowej.
-
Theoretical consideration of free convective heat transfer from a round isothermal plate slightly inclined from the vertical
PublicationA semi-analytical solution of simplified Navier-Stokes and Fourier-Kirchhoff equations describing free convective heat transfer from a round isothermal surface slightly inclined from the vertical is presented. The solution is based on the assumption, typical for natural convection, that the velocity component normal to the surface is negligibly small in comparison to the tangential one. Next we neglect the nonlinear inertia force...
-
Numerical model for thin liquid film with evaporation and condensation on solid surfaces in systems with conjugated heat transfer
PublicationCondensation and evaporation processes from wetted surfaces are of utmost importance in many technological or industrial applications. In many devices such as home-appliances and air conditioning systems just to name a few, condensation and evaporation processes greatly impact their performance and energy efficiency; The physics of these processes is quite complex, involving conjugate heat transfer among solid–liquid film-gaseous...
-
Size and mass minimization of capacitor bank in a power converter DC line of DC drive with closed loop control system with PWM and current limitation
PublicationPaper deals with evaluation equations for power filter of AC-DC power converter which allows to provide size and mass minimization of capacitor bank in DC drive closed loop systems with PWM and current limitation. Reliability of provided equations is proved by simulation in MATLAB/Simulink
-
Modelling of heat transfer in supercritical pressure recuperators
PublicationIn the paper presented is analysis of convective flow heat transfer at supercritical pressure in channels of heat exchanger working in the thermodynamic cycle. The modelling is based on the division of the flow into three regions, namely the heavy fluid, a two phase flow consisting of the heavy and light fluids and finally the light fluid flow. Modelling is concentrated on the region of simultaneous flow of two fluids divided into...
-
Heat tint colours on stainless steel and welded joints
PublicationSurface layer condition of stainless steels and welded joints influences strongly their corrosion resistance. This problem seems to be underestimated. This current study explains the phenomenon of heat tint forming on welds, the methods of its removal, inspection procedures after heat tint removing and post weld finishing
-
Thermodynamic and economic analysis of nuclear power unit operating in partial cogeneration mode to produce electricity and district heat
PublicationThis paper presents the methodology of techno-economic analysis for a nuclear unit operating in partial cogeneration mode and its application for the case study: a nuclear power plant planned in Poland. The research objectives were: to propose EPR, AP1000 and ESBWR nuclear condensing-extraction turbine systems modifications required for operation in cogeneration, to determine optimal heat production and heat transport line (HTL)...
-
Application of the Barkhausen effect probe with adjustable m agnetic field direction for stress state determination in the P91 ste el pipe
PublicationThe paper presents the results of application of a novel Barkhausen effect (BE) probe with adjustable magnetizing field direction for the stress level evaluation in ferromagnetic materials. The investigated sample was in a form of a pipe, made of P91 steel that was anisotropic due to the production process. The measurements were performed before and after welding, revealing the influence of welding process on the residual stress...
-
Skalowalne modele fizyczne wybranych typów siłowni wiatrowych w technologii hardware-in-the-loop
PublicationCelem niniejszej rozprawy jest opracowanie adekwatnego programowalnego modelu fizycznego siłowni wiatrowej wykorzystującego urządzenia elektryczne oraz model przetwarzania energii kinetycznej wiatru na energię mechaniczną ruchu obrotowego wirnika generatora. Zaproponowany przez autora model sterowany jest przez regulator prędkości, bazujący jedynie na pomiarach prędkości obrotowej oraz momentu elektromagnetycznego. Monografia stanowi...
-
HIGH TEMPERATURE HEAT PUMPS – PERSPECTIVE HEATING SYSTEMS?
PublicationIn the paper presented are authors own concepts of high temperature compressor heat pumps for the utilisation of medium and low temperature sources of heat. Working fluids for use in high temperature heat pumps are discussed, as well as the criteria for their selection. Analyses are presented for the production of in the upper steam source at 130 °C. One-stage systems and cascade systems were analyzed. An analysis of the coefficient...
-
A device for measuring heat flux on a rocket skin surface
PublicationA novel method for measuring heat flux on a surface is presented. It is an extensive upgrade of currently known heat flux sensors used mostly in civil engineering. As the thermal environment of launchers, especially sounding rocket can have an enormous negative effect on payload, careful considerations have to be taken in the process of preparing insulation. Usually, thermal data provided by the launch vehicle manufacturer is limited...
-
Gas boiler as a heat source for the domestic micro-CHP
PublicationIn the presented analysis a commercially available domestic gas boiler as a heat source for domestic ORC is considered. The applicability of the gas boiler (De Dietrich with thermal power 25 kW) coupled with the laboratory prototype micro ORC setup has experimentally studied. The main aim of the study is to determine the working fluid temperature, attainable heat rates and efficiencies of the whole system. Preliminary investigations...
-
Gas boiler as a heat source for the domestic micro-CHP
PublicationThis analysis considers a commercially available domestic gas boiler as a heat source for a domestic organic Rankine cycle system. An experimental study was made into the applicability of the gas boiler (De Dietrich with thermal power 25 kW) coupled with the laboratory prototype micro ORC setup. The main aim of the study is to determine the working fluid temperature, attainable heat rates and effciencies of the whole system. Preliminary...
-
Nuclear power plant as a source of electrical energy and heat
PublicationIn this paper certain issues concerning usage of nuclear power plants as sources of not only electric power but also thermal energy will be discussed. For such a solution appeals most of all the need to limit harmful emissions of gases (including CO2) and ashes, which come from the process of burning fossil fuels, as well as the raising demand for network heat and chill. Additionally combined heat and power production brings measurable...