Filtry
wszystkich: 1405
wyświetlamy 1000 najlepszych wyników Pomoc
Wyniki wyszukiwania dla: UNDERGROUND HEAT EXCHANGER
-
Jeffreys heat conduction in coupled semispaces subjected to interfacial heating
PublikacjaA Jeffreys heat conduction problem for coupled semispaces subjected to the action of an interfacial heat source was defined. An analytical solution of the problem was derived for a polynomial specific power of the heat source using the Laplace transform approach. The asymptotic and parametric analysis was performed for different ratios of thermal conductivities , thermal diffusivities , thermal relaxation times and coefficients...
-
Heat transfer and heat exchangers
Kursy OnlineOmówienie głównych mechanizmów i praw przenoszenia ciepła. Przykłady rozwiązywania zagadnień z przewodzenia ciepła, konwekcji i radiacji. Podstawy teorii rekuperatorów. Przykłady obliczania pół powierzchni rekuperatorów.
-
Modelling of heat transfer in supercritical pressure recuperators
PublikacjaIn 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...
-
Natural convective heat transfer from isothermalconic
PublikacjaTheoretical considerations on convective heat transfer from isothermal upward conicalsurfaces have been presented. The physical model of this phenomenon consists of an isothermalcone of inclination angle (φ) between the cone generating line (X) and the radius (R) of the cone base. The angle is a parameter of conical surface which varied from (φ = 0−circular horizontal plate) to (φ = π/2—vertical cylinder) . Onthe basis of Navier–Stokes...
-
Selected prtoblems of heat ans mass transfer
Kursy OnlineThew lecture presentes advanced topics in heat ans mass transfer
-
Possibilities of heat transfer augmentation in heat exchangers with minichannels for marine applications
PublikacjaIn the paper, new trends in development of microchannel heat exchangers are presented. The exchangers developed in this way can be applied in marine applications. Main attention was focused on heat exchangers design with reduced size of passages namely based on microchannels. In our opinion future development of high power heat exchangers will be based on networks micro heat exchangers.
-
Evaluating the influence of radiative heat flux on convective heat transfer from a vertical plate in air using an improved heating plate
PublikacjaThis article examines the influence of radiative heat flux on the accuracy of the results of free convective heat transfer in air. In order to carry out these tests, based on the experience gained during the operation of a plate heated on one side, compensated by a reverse heat loss flux counter-heater, a unique double-sided heating sandwich plate was designed and built, consisting of three thin epoxy resin plates reinforced with...
-
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
Czasopisma -
Comparison of heat transfer from single- and double-sided heated horizontal plate under free convection in air with constant heat flux condition
PublikacjaThis paper presents the results of an experimental and numerical study of convective heat transfer from a newly designed double-sided heated horizontal plate in air. To ensure equal heat transfer from both surfaces, the plate was equipped with two independently supplied electric heaters and resistance thermometers on each side. Minimizing the plate's thickness reduced lateral heat loss and improved measurement accuracy. The study...
-
Concentrations of monoaromatic hydrocarbons in the air of the underground car park and individual garages attached to residential buildings
PublikacjaThe paper describes the characteristics of a two-level underground car park and three individual garages attached to residential buildings, differing by the resident utilization habits, located in North Poland (Tri-City agglomeration area). The strategy of collecting the analyte samples from air in mentioned enclosed areas, concerning the determination of benzene, toluene, ethylbenzene, o-xylene and p,m-xylenes (BTEX) concentrations...
-
Numerical Study of Turbulent Flow and Heat Transfer of Nanofluids in Pipes
PublikacjaIn 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...
-
Perfect thermal contact of hyperbolic conduction semispaces with an interfacial heat source
PublikacjaThe problem of thermal contact between two bodies with a heat source at their interface presents great scientific and practical interest. On the time scale of a nanosecond or shorter, heat propagation should be considered in the form of thermal waves of finite speeds. This study investigated the thermal behaviour of hyperbolic conduction semispaces in perfect thermal contact subjected to the action of an interfacial heat source....
-
Effect of Flow Normalization in Micro-Pin-Finned Heat Sink: Numerical Study
PublikacjaThe micro-pin-fin heat sink (MPFHS) is widely employed for the heat transfer enhancement of microchannel heat sinks. In the current paper, the effect of flow normalization on the thermohydraulic performance of micro-pin-finned heat sinks is studied numerically. Two geometries of MPFHSs, the conventional design micro-pin-fin heat sink (CD-MPFHS) with a uniform-width micro pin fin and the proposed design micro-pin-fin heat sink (PD-MPFHS)...
-
Empirical Relationship Describing Total Convective and Radiative Heat Loss in Buildings
PublikacjaOn the basis of theoretical considerations of convective-radiative heat transfer, a relationship was developed enabling the total convective and radiative heat flux QC+R emitted from any object at tw and its surroundings at t∞ to be calculated from known values of the surface temperature of such an object, i.e., the known temperature difference Δt=tw - t∞ and average air temperature Tav. This relationship is applied to thermal...
-
A simplified energy dissipation based model of heat transfer for subcooled flow boiling
PublikacjaIn the paper a model is presented based on energetic considerations for subcooled flow boiling heat transfer. The model is the extension of authors own model developed earlier for saturated flow boiling and condensation. In the former version of the model we used the heat transfer coefficient for the liquid single-phase as a reference level, due to the lack of the appropriate model for heat transfer coefficient for the subcooled...
-
Recent advances of selected passive heat transfer intensification methods for phase change material-based latent heat energy storage units: A review
PublikacjaThe following article overviews recent studies regarding heat transfer enhancement methods, explicitly focusing on fins and coils utilization, in phase change material-based latent heat thermal energy storage systems. It discusses the influence of various geometrical and material parameters on the melting and solidification processes, as well as the orientation of the heat transfer surface within the storage tank. Additionally,...
-
Experiment-Based Study of Heat Dissipation from the Power Cable in a Casing Pipe
PublikacjaThe paper deals with the important challenges in terms of electricity transmission by means of underground cable lines. The power cable’s performance is characterized by an ampacity that represents its maximum electric current-carrying capacity. The ampacity of power cables depends on their ability to diffuse the heat generated by the current flow into the environment. In the performed research, the analysis of the efficiency of...
-
Model studies to identify input parameters of an algorithm controlling electric supply/consumption process by underground iron ore enterprises
PublikacjaPurpose is the development of the research format of a mathematical model to select and assess input parameters of an algorithm controlling distribution of electric energy flows in the monitoring structure of electricity supply/ consumption by using equipment of mining enterprises engaged in underground iron ore raw materials extraction. Methods. The analytical research involved a theory of random processes adapted to the real...
-
Study of Soil Temperature and Moisture Changes in a Physical Model of an Underground Cable Line
PublikacjaThe ampacity of power cables is highly dependent on the thermal resistivity of the soil in which they are laid. The lower it is, the higher this ampacity. The thermal resistivity of the soil decreases as its moisture increases. Therefore, it is preferable that the soil around the cables has high moisture. Unfortunately, the heat generated in heavily loaded cables causes the migration of moisture from the surrounding soil, which...
-
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...
-
Hyperbolic heat conduction at a microscopic sliding contact with account of adhesion-deformational heat generation and wear
PublikacjaDifferent non-Fourier models were proposed to simulate temperatures in materials subjected to extremely fast thermal disturbances, when the speed of heat propagation should be concerned. The present study investigated temperature and heat balance at a microscopic sliding contact during a single frictional interaction based on the Cattaneo-Vernotte hyperbolic heat conduction equation. Two fundamental features of friction, namely,...
-
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...
-
Underground Water Level Prediction in Remote Sensing Images Using Improved Hydro Index Value with Ensemble Classifier
PublikacjaThe economic sustainability of aquifers across the world relies on accurate and rapid estimates of groundwater storage changes, but this becomes difficult due to the absence of insitu groundwater surveys in most areas. By closing the water balance, hydrologic remote sensing measures offer a possible method for quantifying changes in groundwater storage. However, it is uncertain to what extent remote sensing data can provide an...
-
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...
-
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.
-
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.
-
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.
-
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....
-
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.
-
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...
-
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...
-
The identification of operational cycles in the monitoring systems of underground vehicles
Publikacja -
Measurement methods for assessing insulation condition of underground pipelines
PublikacjaThe paper discusses the most frequently applied measurement methods for assessing the quality of external insulation along pipelines and detecting defect locations in the protective coating. The quality of coating along a given pipeline section under investigation is assessed by determining unitary resistance of the coating, which is calculated on the basis of measurement results obtained along a pipeline subjected to cathodic...
-
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)...
-
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...
-
World of Mining - Surface and Underground
Czasopisma -
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.
-
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...
-
Quality Evaluation of Speech Transmission via Two-way BPL-PLC Voice Communication System in an Underground Mine
PublikacjaIn order to design a stable and reliable voice communication system, it is essential to know how many resources are necessary for conveying quality content. These parameters may include objective quality of service (QoS) metrics, such as: available bandwidth, bit error rate (BER), delay, latency as well as subjective quality of experience (QoE) related to user expectations. QoE is expressed as clarity of speech and the ability...
-
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...
-
Analytical solution of non-stationary heat conduction problem for two sliding layers with time-dependent friction conditions
PublikacjaIn 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...
-
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....
-
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...
-
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,...
-
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...
-
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.
-
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.
-
Cattaneo–Christov heat flow model for copper–water nanofluid heat transfer under Marangoni convection and slip conditions
PublikacjaThis 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
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...