Wyniki wyszukiwania - BazTech

1

Heat transfer improvement using additive manufacturing technologies: a review

Byiringiro J., Chaanaoui M., Halimi M., Vaudreuil S.

Archives of Materials Science and Engineering

|

2023

|

Vol. 123, nr 1

30--41

EN

Purpose: To provide a comprehensive review of additive manufacturing use in heat transfer improvement and to carry out the economic feasibility of additive manufacturing compared to conventional manufacturing. Heat transfer improvement is particularly interesting for different industrial sectors due to its economic, practical, and environmental benefits. Three heat transfer improvement techniques are used: active, passive, and compound. Design/methodology/approach: According to numerous studies on heat transfer enhancement devices, most configurations with strong heat transfer performance are geometrically complex. Thus, those configurations cannot be easily manufactured using conventional manufacturing. With additive manufacturing, almost any configuration can be manufactured, with the added benefit that the produced parts’ surface characteristics can enhance heat transfer. It can, however, lead to a significant pressure drop increase that will reduce the overall performance. In the given article, a comparison of the capital cost of a 100 MW parabolic trough power plant has been carried out, considering two types of solar receivers; the first is manufactured using conventional methods, and the second uses additive manufacturing. The heat transfer of the new receiver configuration is investigated using computational fluid dynamics through ANYS Fluent. Findings: Although the cost of additive manufacturing machines and materials is high compared to conventional manufacturing, the outcome revealed that the gain in efficiency when using additive-manufactured receivers leads to a reduction in the number of receiver tubes and the number of solar collectors needed in the solar field It implies a considerable reduction of parabolic trough collector plant capital cost, which is 20.7%. It can, therefore, be concluded that, even if initial setup expenses are higher, additive manufacturing could be more cost- effective than traditional manufacturing. Practical implications: With the reduction of the parabolic trough collector plant capital cost, the levelized cost of electricity will eventually be reduced, which will play a role in increasing the use of solar thermal energy. Originality/value: No review studies discuss the manufacturing potential and cost- effectiveness potential of additive manufacturing when producing heat transfer improvement equipment, especially when producing long pieces. In addition, the paper uses a novel receiver configuration to investigate the economic aspect.

2

Flow and heat transfer characteristics of a novel airfoil-based tube with dimples

Pei Houju, Liu Meinan, Yang Kaijie, Zhimao Li, Liu Chao

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2022

|

Vol. 70, nr 4

art. no. e141984

EN

The performance of a novel airfoil-based tube with dimples is numerically studied in the present work. The effect of Reynolds number Re, dimples number N, relative depth H/D, and cross-distribution angle α on flow and heat transfer characteristics are discussed for Re in the range between 7,753 and 21,736. The velocity contour, temperature contour, and local streamlines are also presented to get an insight into the heat transfer enhancement mechanisms. The results show that both the velocity magnitude and flow direction change, and fluid dynamic vortexes are generated around the dimples, which intensify the flow mixing and interrupt the boundary layer, resulting in a better heat transfer performance accompanied by a certain pressure loss compared with the plain tube. The Nusselt number Nu of the airfoil-based tube increases with the increase of dimples number, relative depth, and Reynolds numbers, but the effect of cross-distribution angle can be ignored. Under geometric parameters considered, the airfoil-based tube with N = 6, H/D = 0.1, α = 0° and Re = 7,753 can obtain the largest average PEC value 1.23. Further, the empirical formulas for Nusselt number Nu and friction factor f are fitted in terms of dimple number N, relative depth H/D, and Reynolds number Re, respectively, with the errors within ± 5%. It is found that the airfoil-based tube with dimples has a good comprehensive performance.

3

A review on active techniques in microchannel heat sink for miniaturization problem in electronic industry

Bhandari Prabhakar, Singh Jarnail, Kumar Kaushal, Ranakoti Lalit

Acta Innovations

|

2022

|

no. 45

45--54

EN

With continuous miniaturization of modern electronic components, the need of better cooling devices also keeps on increasing. The improper thermal management of these devices not only hampers the efficiency but can also cause permanent damage. Among various techniques, microchannel heat sink has shown most favourable performance. To further enhance the performance, two techniques i.e., active and passive are used. In passive technique, no external power source is required like heat sink design alteration and working fluid modification. External power source is necessary for heat transfer augmentation in the microchannel heat sink when using the active approach. Due to compact size of microchannel, active techniques are not used more often. However, the present work highlights the different active technique used in microchannel i.e., Electrostatic forces, flow pulsation, magnetic field, acoustic effects, and vibration active techniques. Above mentioned techniques have been analysed in detail.

4

Evaluation of thermal performance factor for solar air heaters with artificially roughened channels

Siddique Waseem, Raheem Aneeq, Aqeel Muhammad, Qayyum Sualeh, Salamen Tareq, Waheed Khalid, Qureshi Kamran

Archive of Mechanical Engineering

|

2021

|

LXVIII, nr 2

195--225

EN

Heat transfer augmentation has become the utmost industrial desire. Turbulence promoters seems to be a better option for better heat transfer but at the expense of enormous pressure drop. In the current study, experimental optimization of heat transfer and pressure drop in various configurations of ribbed and corrugated surfaces on the bottom wall of the Solar Air Heater channel, having aspect ratio of 26:5 was performed. The results were evaluated in terms of enhancement in heat transfer (Nu/Nu s), friction factor ratio (f/f s) and thermal performance factor ( η). Three different cases and nine configurations with a pitch to rib/corrugation height ratio of 4.0 were studied. Case A consists of a smooth, continuous square rib, inline and staggered broken ribs. Case B comprises 30°, 45°, 60° and 90° trapezoidal corrugated geometries while Case C is the comparison of smooth, wavy corrugated and the best configurations of cases A and B. The results show that rectangular duct with staggered broken ribs and trapezoidal corrugation at 45° are the best configurations for case A and B, respectively. The 45° corrugated configuration is the best one amongst all, with values of 1.53, 1.5 and 1.33% for Nu/Nu s, f/f s and η respectively.

5

Enhancement of convective heat transfer in a parabolic trough collector using vibrations - an introductory numerical analysis

Grzywnowicz Krzysztof, Bartela Łukasz, Remiorz Leszek, Stanek Bartosz

Journal of Power Technologies

|

2020

|

Vol. 100, nr 4

291--300

EN

Energy generation systems based on renewable energy sources (RES) are rapidly gaining ground in the global power and heatmarket. Most of these systems are well-suited to distributed energy solutions, including distributed heat production. Individual users and local low-power plants can use solar thermal devices for the purpose of providing domestic hot water, heating and cooling. Nevertheless, the variability of solar irradiance can make it difficult to harvest energy efficiently all year round. Therefore, from the point of view of improving the overall, year-averaged operational parameters of a solar thermal device it isparamount to maximize the heat acquired from it at times ofhigh radiation flux. This paper discusses computational research on enhancing convective heat transfer in the absorber of a parabolic trough collector (PTC), through inducing vibrations of an immersed flat plate. The investigation identifies the influence of different amplitudes and frequencies of oscillatory motion on the absorber’s parameters, compares them with the construction of a classical absorber and considers flow turbulization. The results indicate there is only a limited application of vibrations to enhance operational parameters of solar thermal absorbers, with the best results obtained for thermal fluidflows of below 0.1 dms.

6

Heat transfer enhancement from a heated plate with hemispherical convex dimples by forced convection along with a cross flow jet impingement

Patro P., Garnayak S.

International Journal of Applied Mechanics and Engineering

|

2020

|

Vol. 25, no. 1

127--141

EN

In the present study, heat transfer from a small three dimensional rectangular channel due to turbulent jet impinging from a nozzle normal to the main flow at the inlet has been investigated. Hemispherical convex dimples are attached to the bottom plate from where heat transfer calculations are to be performed. Numerical simulations were performed using the finite volume method with […] turbulence model. The duct and nozzle Reynolds number are varied in the range of […], respectively. Different nozzle positions (X/D = 10.57, 12.88, 15.19) along the axial direction of the rectangular duct have been considered. It has been found that higher heat transfer is observed at X/D = 10.57 as compared to the other positions. The heat transfer enhancements with and without cross-flow effects have also been compared. It has been shown that the heat transfer rate with cross-flow is found to be much higher than that without crossflow. Also, the effect of dimples on the heated surface on heat transfer was investigated. The heat transfer is found to be greater in the presence of a dimpled surface than a plane surface.

7

Experimental investigation and characteristics of multiwalled carbon nanotube aqua nanofluids from a flat plate heater surface in a pool

Vasudevan D., Senthil Kumar D., Murugesan A., Vijayakumar C.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2020

|

Vol. 68, nr 3

547--554

EN

In this experimental investigation, the critical heat flux (CHF) of aqua-based multiwalled carbon nanotube (MWCNT) nanofluids at three different volumetric concentrations 0.2%, 0.6%, and 0.8% were prepared, and the test results were compared with deionized water. Different characterization techniques, including X-ray diffraction, scanning electron microscopy and Fourier transform infrared, were used to estimate the size, surface morphology, agglomeration size and chemical nature of MWCNT. The thermal conductivity and viscosity of the MWCNT at three different volumetric concentrations was measured at a different temperature, and results were compared with deionized water. Although, MWCNT-deionized water nanofluid showed superior performance in heat transfer coefficient as compared to the base fluid. However, the results proved that the critical heat flux is increased with an increase in concentrations of nanofluids.

8

Vibration-Assisted Laser Surface Texturing and Electromachining for the Intensification of Boiling Heat Transfer in a Minichannel

Piasecka M., Strąk K., Grabas B.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 4

1983--1990

EN

The paper describes applications of the vibration-assisted laser surface texturing and spark erosion process as methods of modifying properties and structures of metal surfaces. Practical aspects of the use of produced surfaces in the heat exchanger with a minichannel have been described. Compared with smooth surfaces, developed metal surfaces obtained by vibration-assisted laser surface texturing and electromachining show more effective heat transfer. The local heat transfer coefficient for the saturated boiling region obtained for developed surfaces had the values significantly higher than those obtained for the smooth plate at the same heat flux. The experimental results are presented as the heated plate temperature (obtained from infrared thermography) and relationships between the heat transfer coefficient and the distance along the length of the minichannel for the saturated boiling region.

9

Nanofluid flow and heat transfer in boundary layers at small nanoparticle volume fraction: Zero nanoparticle flux at solid wall

Liu J. T. C., Fuller M. E., Wu K. L., Czulak A., Kithes A. G., Felten C. J.

Archives of Mechanics

|

2017

|

Vol. 69, nr 1

75--100

EN

The continuum formulation is applied to the developing boundary layer problem, which approximates the entrance region of nanofluid flow in micro channels or tubes. The thermophysical properties are expressed as “equations of state” as functions of the local nanofluid volume fraction. Based on experimental utilization of nanofluid prevalently at small volume fraction of nanoparticles, a simple perturbation procedure is used to expand dependent variables in ascending powers of the volume fraction. The zeroth order problems are the Blasius velocity boundary layer and the Pohlhausen thermal boundary layer. These are accompanied by the volume fraction diffusion equation. In detailed applications, the boundary condition of zero-volume flux at a solid wall is specified and yields an “insulated wall” solution of constant volume fraction. Two property cases are calculated as comparisons: one is the use of mixture properties for the nanofluid density and heat capacity and the transport properties prevalently used in the literature attributed to Einstein and to Maxwell. Results for alumina are compared to experiments. The theory underestimates the experimental results. This leads to the second comparison, between “conventional” properties and those obtained from molecular dynamics computations available for gold-water nanofluids. The latter properties considerably increased the heat transfer enhancement relative to “conventional” properties and heat transfer enhancement is comparable to the enhanced skin friction rise. To fully appreciate the potential of nanofluids and heat transfer enhancement, further molecular dynamics computations of properties of nanofluids, including transport properties, accompanied by careful laboratory experiments on velocity and temperature profiles are suggested.

10

Electrohydrodynamic technique of condensation enhancement

Lackowski M., Przybyliński T., Karwacki J.

Przegląd Elektrotechniczny

|

2016

|

R. 92, nr 8

92--94

EN

This paper concentrates on condensation heat transfer augmentation by means of active condensate drainage in strong electric field. The electrohydrodynamic (EHD) technique is suitable for dielectric media used in refrigeration, ORC cycles and heat pump devices. In presented experiment, a condenser with condensation on the outer surfaces of horizontal tubes was investigated. The electric field was generated between each tube and two rods placed externally. The electric field influences the draining of the liquid (condensate) film from the tubes surface. Presented in this paper experimental research of a tubes bundle with a rod electrode for each tube have not been published in the literature so far.

PL

Niniejsza praca skupia się na intensyfikacji procesu wnikania ciepła podczas kondensacji, poprzez poprawę spływu skroplin wskutek przyłożenia silnego pola elektrycznego. Taka elektrohydrodynamiczna (EHD) metoda jest odpowiednia dla dielektrycznych czynników roboczych stosowanych w chłodnictwie, obiegach ORC i w pompach ciepła. W omawianym eksperymencie badano kondensację na zewnętrznych powierzchniach pęczka poziomych rur, wchodzących w skład skraplacza. Pole elektryczne przykładano pomiędzy każdą z rur a parą elektrod prętowych, umieszczonych w pobliżu zewnętrznej powierzchni rury. Pole elektryczne wpływa na spływ filmu cieczy (kondensatu) tworzącego się na powierzchni rury. Zaprezentowane w pracy wyniki eksperymentalne dla pęczka rur, z elektrodami prętowymi przy każdej z nich, są unikalne i nie były dotychczas publikowane.

11

Zastosowanie teksturowania laserowo-wibracyjnego do intensyfikacji procesu wrzenia w przepływie przez minikanał o przekroju prostokątnym

Strąk K., Piasecka M., Grabas B.

Mechanik

|

2016

|

R. 89, nr 12

1831--1835

PL

Przedstawiono efektywność wymiany ciepła podczas wrzenia płynu chłodniczego przepływającego przez pionowy minikanał, asymetrycznie ogrzewany powierzchnią rozwiniętą teksturowaniem laserowo-wibracyjnym. Analizy efektywności wymiany ciepła dokonano na podstawie lokalnych współczynników przejmowania ciepła na styku powierzchnia grzejna–płyn. Zastosowanie powierzchni grzejnej rozwiniętej teksturowaniem laserowo-wibracyjnym wspomogło osiągnięcie efektywniejszej wymiany ciepła podczas wrzenia nasyconego w porównaniu z powierzchnią gładką, gdyż uzyskano wyższe wartości współczynników przejmowania ciepła.

EN

This chapter discusses the efficiency of flow boiling heat transfer for a fluid flowing through a vertical minichannel heated asymmetrically with a surface enhanced by vibrationassisted laser texturing. The study of the heat transfer efficiency involved analysing the local values of the heat transfer coefficients at the interface between the heated surface and the fluid. The use of an enhanced surface produced by vibration-assisted laser texturing contributed to more efficient saturated flow boiling heat transfer than that observed for a smooth surface because higher values of the heat transfer coefficients were obtained.

12

Numeryczna analiza możliwości zwiększenia efektywności grzewczej pompy ciepła, poprzez modyfikację skraplacza

Muszyński T., Meller M.

Chłodnictwo : organ Naczelnej Organizacji Technicznej

|

2016

|

R. 51, nr 5

5--9

PL

W niniejszej pracy określono charakterystykę prostego modelu wymiennika ciepła bazującego no skraplaczu powietrznej pompy ciepła. Jest to helikoidalny rekuperator typu rura w rurze. Zaproponowano i poddano analizie numerycznej dwie metody intensyfikacji wymiany ciepła i zestawiono wyniki z modelem porównawczym. Zastosowane rozwiązania zwiększające strumień wymienianego ciepła spowodowały wzrost odbieranego przez wodę strumienia ciepła nawet o30% w przypadku wysokich prędkosci przepływu, lecz zwiększają jedocześnie pracę pompowania czynnika nawet o 50%. Dodatkowo porównano nakład materiałowy proponowanych rozwiązań.

EN

The article presents, the characteristics of a simple model of heat exchanger based on the air condenser of the air source heat pump. This is a simple helicoidal recuperator, tube-in-tube type. Authors proposed and subjected to numerical analysis two methods to enhance the heat transfer. Obtained results are compared with reference model. Applied intensification to increased heat flux by 30% at high flow rate but increased the pressure drops up to 50%. In addition, material cost of proposed modifications is presented.

13

Heat transfer enhancement in natural convection in micropolar nanofluids

Rup K., Nering K.

Archives of Mechanics

|

2016

|

Vol. 68, nr 4

327--344

EN

In this work an analysis of momentum, angular momentum and heat transfer during unsteady natural convection in micropolar nanofluids is presented. Selected nanofluids treated as single phase fluids, contain small particles. In particular, two ethylene glycol-based nanofluids were analyzed. The volume fraction of these solutions was 6%, 3.5% and 0.6%. The first ethylene glycol solution contained Al2O3 nanoparticles (d = 38.4 nm), and the second ethylene glycol solution contained Cu nanoparticles (d = 10 nm).

14

Application of the method of fundamental solutions to the analysis of fully developed laminar flow and heat transfer

Mrozek K., Mierzwiczak M.

Journal of Theoretical and Applied Mechanics

|

2015

|

Vol. 53 nr 3

505--518

EN

In this study, fully developed laminar flow and heat transfer in an internally longitudinally finned tube are investigated through application of the meshless method. The flow is assumed to be both hydrodynamically and thermally developed, with a uniform outside-the-wall temperature. The governing equations have been solved numerically by means of the method of fundamental solutions in combination with the method of particular solutions to obtain the velocity and temperature distributions. The advantage of the proposed approach is that it does not require mesh generation on the considered domain or its boundary, but uses only a cloud of arbitrarily located nodes. The results, comprising the friction factor as well as the Nusselt number, are presented for varied length values and fin numbers, as well as the thermal conductivity ratio between the tube and the flowing fluid. The results show that the heat transfer improves significantly if more fins are used.

15

Zastosowanie metod elektrohydrodynamicznych do intensyfikacji wymiany ciepła w skraplaczach płaszczowo-rurowych

Butrymowicz D., Karwacki J., Trela M., Śmierciew K.

Chłodnictwo : organ Naczelnej Organizacji Technicznej

|

2014

|

R. 49, nr 8

2--8

PL

W artykule przedstawiono głównie kierunki badań efektywnych elektrohydrydynamicznych metod intensyfikacji wymiany ciepła w skraplaczach urządzeń chłodniczych. Zwrócono uwagę na możliwość znacznego podwyższenia COP drogą poprawy wymiany ciepła. Zwrócono też uwagę na szczególnie ważny problem właściwej geometrii elektrod dla skraplaczy płaszczowo-rurowych.

EN

The general directions of possibile heat transfer enhancement elektro-hydrodynamic techniques in refrigeration condensers are presented. Attention has been paid to possibile improvement of COP due to heat transferimprovement. Appropriate geometry and configuration of the drainage electrodes for the shell-and-tube condensers has been discussed.

16

Unsteady natural convection in micropolar nanofluids

Rup K., Nering K.

Archives of Thermodynamics

|

2014

|

Vol. 35, no. 3

155--170

EN

This paper presents the analysis of momentum, angular momentum and heat transfer during unsteady natural convection in micropolar nanofluids. Selected nanofluids treated as single phase fluids contain small particles with diameter size 10-38.4 nm. In particular three water-based nanofluids were analyzed. Volume fraction of these solutions was 6%. The first of the analyzed nanofluids contained TiO2 nanoparticles, the second one contained Al2O3 nanoparticles, and the third one the Cu nanoparticles.

17

Condensation enhancement by means of electrohydrodynamic techniques

Butrymowicz D., Karwacki J., Trela M.

Archives of Thermodynamics

|

2014

|

Vol. 35, no. 4

3--27

EN

Short state-of-the-art on the enhancement of condensation heat transfer techniques by means of condensate drainage is presented in this paper. The electrohydrodynamic (EHD) technique is suitable for dielectric media used in refrigeration, organic Rankine cycles and heat pump devices. The electric field is commonly generated in the case of horizontal tubes by means of a rod-type electrode or mesh electrodes. Authors proposed two geometries in the presented own experimental investigations. The first one was an electrode placed just beneath the tube bottom and the second one consisted of a horizontal finned tube with a double electrode placed beneath the tube. The experimental investigations of these two configurations for condensation of refrigerant R-123 have been accomplished. The obtained results confirmed that the application of the EHD technique for the investigated tube and electrode arrangement caused significant increase in heat transfer coefficient. The condensation enhancement depends both on the geometry of the electrode system and on the applied voltage.

18

Numerical simulation of heat transfer and two-phase flow in a novel heat pipe cold plate

Ma Z., Yao S.

Archives of Thermodynamics

|

2009

|

Vol. 30, no. 1

45-62

EN

To solve high heat flux cooling problems in case of modern electronic appliances, a novel heat pipe cold plate is designed and developed. The heat pipe cold plate is uniquely-different from normal thermosyphons, in which the acetone-aluminum heat pipe construction is composed of eight vertical heat pipe branches with their upper ends and lower ends connected with each other by two horizontal heat pipe branches, respectively, which make the working vapour and liquid flow smooth within the internal flow space of the heat pipe cold plate. In this paper, based on previous experimental and theoretical studies, a mathematical model for numerical simulations of the vapour-liquid two-phase flow and heat transfer phenomena in the heat pipe cold plate is presented. Two-fluid-model is employed to describe flow characteristics and phase interaction between vapour and liquid phases. Differential equations are solved by finite volume method and IPSA algorithm is employed to consider the vapour-liquid coupling effect. Effects of the total heating power and the cooling water flow rate on wall temperature distribution and two-phase flow heat transfer characteristics are numerically simulated. Computation results well agree with experimental results. The novel heat pipe cold plate possesses excellent heat transfer characteristics and temperature uniformity performance; it can provide a much better cooling solution for multi-heat-source and high heat-flux cooling problems than forced-convection cooling techniques. Also, numerical solution established and realized in this paper can be used as a reference.

19

Study of heat transfer mechanism from the rib-roughened heated plate to the flowing air

Jarosiński W., Fodemski T.

Archives of Thermodynamics

|

2003

|

Vol. 24, no 3

31-54

EN

The paper presents an investigation of heat transfer mechanism from a rib-roughened plate to the flowing air, based on the measurements taken in a special small-size wind tunnel with a rectangular cross section flow channel. The heated ribbed wall was located at the channel bottom. The air flow, caused by a suction fan, was steady or pulsating ( the Reynolds number varied from 1000 to 11300). Advanced measurement techniques were used, such as schlieren video film, PIV and hot wire thermoanemometry (for simultaneous measurements of instantaneous velocity and temperature). They allowed to analyze the movement of vortices structure and to evaluate the coherence values of instantaneous temperature records made in the chosen points of the air flow.

20

Heat transfer characteristics of water in a vertical small diameter tube at sub-atmospheric pressure

Chowdhury F., Kaminaga F.

Archives of Thermodynamics

|

2002

|

Vol. 23, no 3

43-57

EN

Boiling heat transfer characteristics of water has been experimentally and analytically examined in a vertical small diameter tube, D = 1.45 mm, L = 100 mm at sub-atmospheric pressures of 5, 11, and 22 kPa under natural circulation condition. Distinct S-shape boiling curves with three different slopes: a slope similar to pool boiling at a low heat flux, a negative slope at a medium heat flux and a slope smaller than that of pool boiling at a high heat flux, have been observed. Comparing the experimental vapour flux with the predicted one, the flow regime might have been annular within our experimental range. Pool boiling correlation of Stephan- Abdelsalam and a boiling correlation of Imura, et al. developed for a thermosyphon correlated well the measured data at low and medium heat flux regions. In the region of high heat flux a large boiling heat transfer enhancement is indicated in the form of S-shape curves. Predictions of heat transfer coefficient by conduction through the thin liguid film gave good results in the region of high heat flux.