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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:
Mathematical modelling of tube heat exchangers with complex flow arrangement
Autorzy:
Taler, D.
Trojan, M.
Taler, J.
Powiązania:
https://bibliotekanauki.pl/articles/185235.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
wymiennik ciepła
przepływ
modelowanie
heat tube exchanger
modelling
complex flow
Opis:
General principles of mathematical modelling of transient heat transfer in cross-flow tube heat exchangers with complex flow arrangements which allow a simulation of multipass heat exchangers with many tube rows are presented. First, a system of differential equations for the transient temperature of both fluids and the tube wall with appropriate boundary and initial conditions is formulated. Two methods for modelling heat exchangers are developed using the finite difference method and finite volume method. A numerical model of multipass steam superheater with twelve passes is presented. The calculation results are compared with the experimental data.
Źródło:
Chemical and Process Engineering; 2011, 32, 1; 7-19
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
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:
Prediction of a cross-flow heat exchanger performance in media flow maldistribution conditions
Prognozowanie efektywności pracy krzyżowoprądowego wymiennika ciepła w warunkach niejednorodnego przepływu czynników
Autorzy:
Bury, T.
Składzień, J.
Powiązania:
https://bibliotekanauki.pl/articles/172859.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
krzyżowoprądowy wymiennik ciepła
analiza termodynamiczna
HEWES
cross-flow heat exchanger
thermodynamical analysis
Opis:
The paper deals with numerical thermodynamic analyses of cross-flow finned tube heat exchangers of the gas-liquid type. The authors postulate that some improvement of the heat exchanger performance may be achieved by applying a special ribbing structure - fitted to certain media flow conditions. First, the measurements have been carried out in order to determine the air inflow non-uniformity and next an own computer code HEWES has been used for numerical simulations in order to evaluate the impact of the measured non-uniformity on the exchangers' efficiency for the heat exchangers with unified ribbing structure. The numerical simulations have been repeated for heat exchangers with special ribbing structures - determined on the basis of experimental results. Results confirm the hypothesis - some increase in the total heat flow rate may be observed for the considered heat exchanger.
Praca dotyczy termodynamicznej analizy krzyżowoprądowego, ożebrowanego wymiennika ciepła typu gaz-ciecz. Autorzy weryfikowali hipotezę zakładającą możliwość uzyskania poprawy efektywności działania urządzenia w wyniku zastosowania specjalnej, dostosowanej do warunków przepływu czynników, struktury ożebrowania. W pierwszej kolejności wykonane zostały pomiary określające zakres i postać niejednorodnego dopływu powietrza do analizowanego wymiennika ciepła, a następnie wykorzystano własny kod komputerowy HEWES do oceny wpływu tej niejednorodności na wydajność cieplną wymiennika. Obliczenia te dotyczyły wymiennika ciepła z jednorodnym ożebrowaniem. Symulacje numeryczne zostały następnie powtórzone dla przypadku wymiennika ze specjalną strukturą ożebrowania, która została dobrana dla wyznaczonych eksperymentalnie warunków dopływu powietrza. Uzyskane rezultaty potwierdzają postawioną na wstępie hipotezę - widoczny jest pewien wzrost wartości strumienia ciepła przekazywanego w wymienniku.
Źródło:
Archiwum Energetyki; 2011, 41, 3-4; 65-76
0066-684X
Pojawia się w:
Archiwum Energetyki
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Effect of Structure on Thermal Power of Cast-iron Heat Exchangers
Autorzy:
Mróz, M.
Orłowicz, A. W.
Tupaj, M.
Jacek-Burek, M.
Radoń, M.
Kawiński, M.
Powiązania:
https://bibliotekanauki.pl/articles/382256.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat exchanger
gray cast iron
thermal power
wymiennik ciepła
żeliwo szare
ciepło
Opis:
The objective of the study reported in this paper was to determine the effect of structure on thermal power of cast-iron heat exchangers which in this case were furnace chambers constituting the main component of household fireplace-based heating systems and known commonly as fireplace inserts. For the purpose of relevant tests, plate-shaped castings were prepared of gray iron with flake graphite in pearlitic matrix (the material used to date typically for fireplace inserts) as well as similar castings of gray cast iron with vermicular graphite in pearlitic, ferritic-pearlitic, and ferritic matrix. For all the cast iron variants of different structures (graphite precipitate shapes and matrix type), calorimetric measurements were carried out consisting in determining the heat power which is quantity representing the rate of heat transfer to the ambient environment. It has been found that the value of the observed heat power was affected by both the shape of graphite precipitates and the type of alloy matrix. Higher thermal power values characterize plate castings of gray iron with vermicular graphite compared to plates cast of the flake graphite gray iron. In case of plates made of gray cast iron with vermicular graphite, the highest values of thermal power were observed for castings made of iron with ferritic matrix.
Źródło:
Archives of Foundry Engineering; 2020, 20, 1; 27-30
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
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:
Methodology of heat transfer and flow resistance measurement for matrices of rotating regenerative heat exchangers
Autorzy:
Butrymowicz, D.
Karwacki, J.
Kwidziński, R.
Śmierciew, K.
Gagan, J.
Przybyliński, T.
Skiepko, T.
Łapin, M.
Powiązania:
https://bibliotekanauki.pl/articles/185740.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
heat transfer
single blow technique
rotating heat exchanger
regenerator
przenikania ciepła
wymiennik ciepła
Opis:
The theoretical basis for the indirect measurement approach of mean heat transfer coefficient for the packed bed based on the modified single blow technique was presented and discussed in the paper. The methodology of this measurement approach dedicated to the matrix of the rotating regenerative gas heater was discussed in detail. The testing stand consisted of a dedicated experimental tunnel with auxiliary equipment and a measurement system are presented. Selected experimental results are presented and discussed for selected types of matrices of regenerative air preheaters for the wide range of Reynolds number of gas. The agreement between the theoretically predicted and measured temperature profiles was demonstrated. The exemplary dimensionless relationships between Colburn heat transfer factor, Darcy flow resistance factor and Reynolds number were presented for the investigated matrices of the regenerative gas heater.
Źródło:
Chemical and Process Engineering; 2016, 37, 3; 341-358
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
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
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