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Wyświetlanie 1-15 z 27
Tytuł:
Numerical analysis of the steam flow field in shell and tube heat exchanger
Autorzy:
Bartoszewicz, J.
Bogusławski, L.
Powiązania:
https://bibliotekanauki.pl/articles/240429.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat transfer
heat exchanger
shell and tube heat exchanger
przenikanie ciepła
wymiennik ciepła
wymiennik płaszczowo-rurowy
Opis:
In the paper, the results of numerical simulations of the steam flow in a shell and tube heat exchanger are presented. The efficiency of different models of turbulence was tested. In numerical calculations the following turbulence models were used: k-ε, RNG k-ε, Wilcox k-ω, Chen-Kim k-ε, and Lam-Bremhorst k-ε. Numerical analysis of the steam flow was carried out assuming that the flow at the inlet section of the heat exchanger were divided into three parts. The angle of steam flow at inlet section was determined individually in order to obtain the best configuration of entry vanes and hence improve the heat exchanger construction. Results of numerical studies were verified experimentally for a real heat exchanger. The modification of the inlet flow direction according to theoretical considerations causes the increase of thermal power of a heat exchanger of about 14%.
Źródło:
Archives of Thermodynamics; 2016, 37, 2; 107-120
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling of the impact of construction solutions on operating parameters of the internal heat exchanger with refrigerant R744
Autorzy:
Janus, Jakub
Skotniczy, Przemysław Jan
Richert, Maria
Powiązania:
https://bibliotekanauki.pl/articles/240370.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchanger
internal heat exchanger
cooling efficiency
numerical fluid mechanics
wymiennik ciepła
wewnętrzny wymiennik ciepła
efektywność chłodzenia
numeryczna mechanika płynów
Opis:
Work on increasing the efficiency of heat exchangers used in car air conditioning systems may lead to a partial change in the construction of refrigeration systems. One of such changes is the use of smaller gas coolers, which directly translates into a reduction in the production costs of the entire system. The article presents the use of computational fluid dynamics methods to simulate the impact of changing the shape of an internal heat exchanger on the cooling efficiency with R744 as the refrigerant. Internal heat exchangers with different geometry of the outer channels were subjected to numerical analysis. The obtained results of calculations show temperature changes in inner and outer channels on the length of the heat exchanger.
Źródło:
Archives of Thermodynamics; 2019, 40, 1; 145-160
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The influence of a radiated heat exchanger surface on heat transfer
Autorzy:
Morel, S.
Powiązania:
https://bibliotekanauki.pl/articles/240062.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchanger
reciprocal emissivity coefficient
wymiennik ciepła
współczynnik emisyjności
Opis:
The experiment leads to establish the influence of radiated surface development heat exchangers on the values of heat flux transferred with water flowing through the exchangers and placed in electric furnace chamber. The values of emissivity coefficients are given for the investigated metal and ceramic coatings. Analytical calculations have been made for the effect of the heating medium (flame) – uncoated wall and then heating medium (flame) – coated wall reciprocal emissivity coefficients. Analysis of the values of exchanged heat flux were also realized. Based on the measurement results for the base coating properties, these most suitable for spraying the walls of furnaces and heat exchangers were selected, and determined by the intensification of heat exchange effect. These coatings were used to spray the walls of a laboratory waste-heat boiler, and then measurements of fluxes of heat absorbed by the cooling water flowing through the boiler tubes covered with different type coatings were made. Laboratory tests and calculations were also confirmed by the results of full-scale operation on the metallurgical equipment.
Źródło:
Archives of Thermodynamics; 2015, 36, 3; 161-174
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fluid flow consideration in fin-tube heat exchanger optimization
Autorzy:
Wais, P.
Powiązania:
https://bibliotekanauki.pl/articles/240200.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
CFD
przepływ płynu
wymiennik optymalizacji
Exchanger optimization
Fin profile
fluid flow
Opis:
The optimization of finned tube heat exchanger is presented focusing on different fluid velocities and the consideration of aerodynamic configuration of the fin. It is reasonable to expect an influence of fin profile on the fluid streamline direction. In the cross-flow heat exchanger, the air streams are not heated and cooled evenly. The fin and tube geometry affects the flow direction and influences temperature changes. The heat transfer conditions are modified by changing the distribution of fluid mass flow. The fin profile impact also depends on the air velocity value. Three-dimensional models are developed to find heat transfer characteristics between a finned tube and the air for different air velocities and fin shapes. Mass flow weighted average temperatures of air volume flow rate are calculated in the outlet section and compared for different fin/tube shapes in order to optimize heat transfer between the fin material and air during the air flow in the cross flow heat exchanger.
Źródło:
Archives of Thermodynamics; 2010, 31, 3; 87-104
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical study of flow maldistribution in plate heat exchangers used for evaporation process
Autorzy:
Pluszka, Paweł
Brenk, Arkadiusz Patryk
Malecha, Ziemowit Miłosz
Powiązania:
https://bibliotekanauki.pl/articles/240610.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
plate heat exchanger
flow maldistribution
evaporation
openFOAM
płytowy wymiennik ciepła
zły rozkład przepływu
Opis:
Geometry of plate heat exchangers (PHE) is characterized by a complex net of narrow channels. It enhances turbulence and results in better heat transfer performance. Theoretically, larger number of channels (plates) should proportionally increase the PHE heat power capacity. In practice a nonuniform massflow distribution in consecutive flow channels can significantly deteriorate the overall heat exchange performance. The flow maldistribution is one of the most commonly reported exploitation problems and is present in PHE with and without phase-change flows. The presented paper investigates numerically a flow pattern in PHE with evaporation of R410A refrigerant. Various sizes of PHE are considered. The paper introduces a robust methodology to transform the complicated geometry of a real 3D PHE to its 2D representation. It results in orders of magnitude faster calculations and allows for fast evaluation of different geometrical changes of PHE and their effect on flow maldistribution.
Źródło:
Archives of Thermodynamics; 2019, 40, 3; 57-82
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of nanofluid concentration on two-phase thermosyphon heat exchanger performance
Autorzy:
Cieśliński, J. T.
Powiązania:
https://bibliotekanauki.pl/articles/240904.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
two-phase thermosyphon
heat exchanger
nanofluid
Wilson method
termosyfon dwufazowy
wymiennik ciepła
metoda Wilsona
Opis:
An approach – relaying on application of nanofluid as a working fluid, to improve performance of the two-phase thermosyphon heat exchanger (TPTHEx) has been proposed. The prototype heat exchanger consists of two horizontal cylindrical vessels connected by two risers and a downcomer. Tube bundles placed in the lower and upper cylinders work as an evaporator and a condenser, respectively. Distilled water and nanofluid water-Al2O3 solution were used as working fluids. Nanoparticles were tested at the concentration of 0.01% and 0.1% by weight. A modified Peclet equation and Wilson method were used to estimate the overall heat transfer coefficient of the tested TPTHEx. The obtained results indicate better performance of the TPTHEx with nanofluids as working fluid compared to distilled water, independent of nanoparticle concentration tested. However, increase in nanoparticle concentration results in overall heat transfer coefficient decrease of the TPTHEx examined. It has been observed that, independent of nanoparticle concentration tested, decrease in operating pressure results in evaporation heat transfer coefficient increase.
Źródło:
Archives of Thermodynamics; 2016, 37, 2; 23-40
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of scale deposits on the internal surfaces of the tubes on the superheater operation
Autorzy:
Trojan, M.
Taler, J.
Powiązania:
https://bibliotekanauki.pl/articles/240190.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
steam superheater
scale deposit
heat exchanger
numerical model
ogrzewacz pary
wymiennik ciepła
model numeryczny
Opis:
A mathematical model of the steam superheater exchanger with distributed parameters has been developed. Scale deposits were assumed to be present on the internal tube surfaces. It was assumed that the inner tube surfaces are covered by a thin layer of scale deposits. The finite volume method was used to solve partial differential equations describing flue gas, tube wall and steam temperature. The developed modeling technique can especially be used for modeling tube heat exchangers when detail information on the tube wall temperature distribution is needed. The numerical model of the superheater developed in the paper can be used for modeling of the superheaters with complex flow arrangement accounting scales on the internal tube surfaces. Using the model proposed the detailed steam, wall and flue gas temperature distribution over the entire superheater can be determined. The steam pressure distribution along its path flow and the total heat transfer rate can also be obtained. The calculations showed that the presence of scale on the internal surfaces of the tubes cause the steam temperature decrease and the heat flow rate transferred from the flue gas to the steam. Scale deposits on the inner surfaces of the tubes cause the tube wall temperature growth and can lead to premature wear of tubes due to overheating.
Źródło:
Archives of Thermodynamics; 2013, 34, 4; 73-91
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mathematical model of a plate fin heat exchanger operating under solid oxide fuel cell working conditions
Autorzy:
Kupecki, J.
Badyda, K.
Powiązania:
https://bibliotekanauki.pl/articles/240703.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
plate fin
heat exchanger
micro-CHP
SOFC
modeling
płytka
wymiennik ciepła
mikro CHP
modelowanie
Opis:
Heat exchangers of different types find application in power systems based on solid oxide fuel cells (SOFC). Compact plate fin heat exchangers are typically found to perfectly fit systems with power output under 5 kWel. Micro-combined heat and power (micro-CHP) units with solid oxide fuel cells can exhibit high electrical and overall efficiencies, exceeding 85%, respectively. These values can be achieved only when high thermal integration of a system is assured. Selection and sizing of heat exchangers play a crucial role and should be done with caution. Moreover, performance of heat exchangers under variable operating conditions can strongly influence efficiency of the complete system. For that reason, it becomes important to develop high fidelity mathematical models allowing evaluation of heat exchangers under modified operating conditions, in high temperature regimes. Prediction of pressure and temperatures drops at the exit of cold and hot sides are important for system-level studies. Paper presents dedicated mathematical model used for evaluation of a plate fin heat exchanger, operating as a part of micro-CHP unit with solid oxide fuel cells.
Źródło:
Archives of Thermodynamics; 2013, 34, 4; 3-21
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal-hydraulic issues of flow boiling and condensation in organic Rankine cycle heat exchangers
Autorzy:
Mikielewicz, J.
Mikielewicz, D.
Powiązania:
https://bibliotekanauki.pl/articles/240039.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
dynamika wymienników ciepła
stabilizacja przepływu
wymiennik ciepła
dynamics of heat exchangers
flow stability
heat exchangers
Opis:
In the paper presented are the issues related to the design and operation of micro heat exchangers, where phase changes can occur, applicable to the domestic micro combined heat and power (CHP) unit. Analysed is the stability of the two-phase .ow in such unit. A simple hydraulic model presented in the paper enables for the stability analysis of the system and analysis of disturbance propagation caused by a jump change of the flow rate. Equations of the system dynamics as well as properties of the working fluid are strongly non-linear. A proposed model can be applicable in designing the system of flow control in micro heat exchangers operating in the considered CHP unit.
Źródło:
Archives of Thermodynamics; 2012, 33, 1; 41-66
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of resisdence time measurements on heat exchangers for the determination of dispersive Peclet numbers
Autorzy:
Roetzel, W.
Na Ranong, C.
Powiązania:
https://bibliotekanauki.pl/articles/240480.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchanger
dispersion model
transient tracer experiment
evaluation method
wymiennik ciepła
model dyspersji
metoda oceny
Opis:
The recently developed special unity Mach number dispersion model prescribes the corrections to heat transfer coefficients which are simple functions of the dispersive Peclet numbers. They can be determined through the residence time measurements. An evaluation method is described in which the measured input and response concentration profiles are numerically Laplace transformed and evaluated in the frequency domain. A characteristic mean Peclet number is defined. The method is also applied to the parabolic dispersion model and the cascade model. A calculated example of a tube bundle with maldistribution and backflow demonstrates the suitability of the evaluation method.
Źródło:
Archives of Thermodynamics; 2014, 35, 2; 103-115
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Recuperator with microjet technology as a proposal for heat recovery from low-temperature sources
Autorzy:
Wajs, J.
Mikielewicz, D.
Fornalik-Wajs, E.
Bajor, M.
Powiązania:
https://bibliotekanauki.pl/articles/240624.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchanger
microjet technology
heat recovery
Wilson plot method
wymiennik ciepła
odzysk ciepła
metoda Wilsona
Opis:
A tendency to increase the importance of so-called dispersed generation, based on the local energy sources and the working systems utilizing both the fossil fuels and the renewable energy resources is observed nowadays. Generation of electricity on industrial or domestic scale together with production of heat can be obtained for example through employment of the ORC systems. It is mentioned in the EU directive 2012/27/EU for cogenerative production of heat and electricity. For such systems the crucial points are connected with the heat exchangers, which should be small in size but be able to transfer high heat fluxes. In presented paper the prototype microjet heat exchanger dedicated for heat recovery systems is introduced. Its novel construction is described together with the systematical experimental analysis of heat transfer and flow characteristics. Reported results showed high values of the overall heat transfer coefficient and slight increase in the pressure drop. The results of microjet heat exchanger were compared with the results of commercially available compact plate heat exchanger.
Źródło:
Archives of Thermodynamics; 2015, 36, 4; 49-64
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of temperature oscillation experiment for the determination of heat transfer coefficient and dispersive Peclet number
Autorzy:
Roetzel, W.
Na Ranong, C.
Powiązania:
https://bibliotekanauki.pl/articles/240047.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchanger
temperature oscillation experiment
evaluation method
dispersion model
wymiennik ciepła
metoda oceny
dyspersja
model
Opis:
An evaluation method is developed for temperature oscillation experiments in heat exchangers. The unity Mach number dispersion model is applied. For the consideration of lateral wall heat conduction an effective wall thickness is introduced together with a wall heat transfer coefficient. The evaluation method may also be applied to single blow experiments with pulse signals. A sensitivity analysis describes and discusses the accuracy of different evaluation procedures.
Źródło:
Archives of Thermodynamics; 2018, 39, 1; 91-110
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation method of single blow experiment for the determination of heat transfer coefficient and dispersive Peclet number
Autorzy:
Roetzel, W.
Na Ranong, C.
Powiązania:
https://bibliotekanauki.pl/articles/240735.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchanger
single blow experiment
evaluation method
dispersion model
wymiennik ciepła
eksperyment
metoda oceny
model dyspersji
Opis:
An evaluation method is developed for single blow experiments with liquids on heat exchangers. The method is based on the unity Mach number dispersion model. The evaluation of one experiment yields merely one equation for the two unknowns, the number of transfer units and the dispersive Peclet number. Calculations on an example confirm that one single blow test alone cannot provide reliable values of the unknowns. A second test with a liquid of differing heat capacity is required, or a tracer experiment for the measurement of the Peclet number. A modified method is developed for gases. One experiment yields the effective number of transfer units and approximate values of the two unknowns. The numerical evaluation of calculated experiments demonstrates the applicability of the evaluation methods.
Źródło:
Archives of Thermodynamics; 2015, 36, 4; 3-24
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On numerical modelling of heat transfer and fluid flow in a scraped surface heat exchanger
Autorzy:
Błasiak, P.
Gnutek, Z.
Powiązania:
https://bibliotekanauki.pl/articles/240070.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
scraped surface heat exchanger
nusselt number
thermal boundary layer
wymiennik ciepła
liczby Nusselta
termiczna warstwa przyścienna
Opis:
Steady state two-dimensional numerical simulation of laminar heat transfer and fluid flow in a scraped surface heat exchanger (SSHE) is presented. Typical SSHE consists of a stator, rotating shaft and scraping blades. Due to symmetry only a quarter of the heat exchanger is modelled. Governing equations for transport of mass, momentum and energy are discretised and solved with the use of commercial CFD code. The results are presented in a nondimensional form for velocity, pressure and temperature distributions. Local and averaged Nusselt number along the stator wall are calculated and depicted in graphs. It was found that the thirty fold increase of the cReynolds number, leads to heat transfer enhancement rate by three times.
Źródło:
Archives of Thermodynamics; 2014, 35, 3; 251-264
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analytical 1D models of the wall thermal resistance of rectangular minichannels applied in heat exchangers
Autorzy:
Rybiński, W.
Mikielewicz, J.
Powiązania:
https://bibliotekanauki.pl/articles/240475.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
minichannel heat exchanger
wall thermal resistance
rectangular minichannel
minikanał
wymiennik ciepła
izolacja termiczna ścian
minikanał prostokątny
Opis:
The paper presents four 1-dimensional models of thermal resistance of walls in a heat exchanger with rectangular minichannels. The first model is the simplest one, with a single wall separating two fluids. The second model of the so called equivalent wall takes into account total volume of intermediate walls between layers of minichannels and of side walls of minichannels. The next two more complicated models take separately into account thermal resistance of these walls. In these two models side walls are treated as fins. The results of models comparison are presented. It is shown that thermal resistance may be neglected for metal walls but it should be taken into account for the walls made of plastics. For the case of non-neglected wall thermal resistance the optimum wall thickness was derived. Minichannel heat exchangers made of plastic are larger than those built of metal, but are significantly cheaper. It makes possible to use of such exchangers in inexpensive microscale ORC installations.
Źródło:
Archives of Thermodynamics; 2016, 37, 3; 63-78
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 27

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