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1

Enhancement of heat transfer in helical coil heat exchangers using nano-fluids

Parveez Malik, Hanief Mohammad

Chemical and Process Engineering

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2022

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Vol. 43, nr 2

279--283

EN

Investigation for heat transfer behaviour of Al2O3 and CuO nano-fluid in helical coil heat exchangers was carried out in this study. The thermo-physical properties of the fluids have temperature dependent nature. The main emphasis was to depict the influence of nano-particle concentration by volume on the characteristics of temperature, rate of heat transfer and heat transfer coefficients (convective). In order to enhance efficiency, density and thermal conductivity are considered to be the most important variables. In comparison to water and for equal flow rate, the rate of heat transfer of nano-fluid increases conspicuously. Efficiency of the helical coil heat exchanger increased by 38.80%.

2

Effect of chemical reaction on mixed convective nanofluid flow on a vertical plate with uniform heat and mass fluxes

Mondal H., Goqo S. P., Sibanda P., De P.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 2

329--342

EN

The purpose of this paper is to consider a two dimensional free convective flow of a nanofluid due to the combined effects of thermal and mass diffusion in the presence of a chemical reaction of first order. The objective of the present investigation is to analyze the free convective flow in the presence of prescribed wall heat flux and mass flux condition. The governing equations of the linear momentum, energy equation and concentration are obtained in a dimensionless form by introducing a suitable group of similarity transformations. The transformed coupled non-linear ordinary differential equations are solved numerically by using appropriate boundary conditions for the various values of physical parameters. Computations are performed for a wide range of values of the various governing flow parameters of the velocity, temperature and species concentration profiles and results are presented graphically. Numerical results for the skin friction coefficient and local Nusselt number are also presented and analyzed in detail. The obtained results are compared with previously published work and are found to be in excellent agreement. The results are a very useful source of information for researchers on the subject of a free convective flow of a nanofluid. This paper illustrates chemical reaction effects on free convective flow of a nanofluid from a vertical plate with uniform heat and mass fluxes.

3

Physical properties improvement of the diesel engine lubricant oil reinforced nanomaterials

Hadi N. J., Al-Hussain R. K. A.

Journal of Mechanical and Energy Engineering

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2018

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Vol. 2, No 3

233--244

EN

This research focuses on the effect of nanomaterials on the physical properties of a local Iraqi lubricant oil (20W-50), which is widely used in diesel engines. The concentrations of 0.001, 0.2 and 0.5 wt% of Al2O3 NPs and CNT are dispersed in the oil with the help of a suitable surfactant using a magnetic stirrer and a sonication process. The density, surface tension, dynamic viscosity, kinematic viscosity, flash point, fire point, pour point, thermal conductivity, thermal images, wear and the coefficient of friction of the oil with and without nanomaterials are tested. The results were shown that the higher concentrations of NPs, the better properties for the engine oil. The density for Al2O3 nanooil indicates a small change at 0.001 and 0.2 wt%, and a decrease at 0.5 wt% ratio. Also, the density of CNT oil shows a slight change at 0.001and then decreasing at 0.2 and 0.5 ratios. In addition, the surface tension of both nanooils are increased. The dynamic viscosity slightly change with an addition of the NPs especially at 20°C and 30°C. Also, there is a convergence in the viscosity values between base and nanooils at 40°C and 50°C. Also, the dynamic viscosity indicates shear thickening behavior at low shear rate, while in the high shear rate the viscosity attempts to be more stable. The kinematic viscosity increases with an increased concentration of the NPs at 40°C and 100°C for both nanooils. The flash and fire point are increasing for both nanooils and Al2O3 nanooil indicates a lower pour point than that of CNT oil. CNT oil indicates higher dissipating heat friction and thermal conductivity than that of Al2O3 nanooil. Thermal images are supported by thermal conductivity and flash point behavior, while the tribology tests are compatible with viscosity behavior. A significant reduction in the coefficient of friction and wear loss is produced for both nanooils.

4

The influence of chemical composition of nanofluids on dimensional changes of hardened constructional steel

Gęstwa W.

Journal of Achievements in Materials and Manufacturing Engineering

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2017

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Vol. 85, nr 1

5--11

EN

Purpose: The possibility definition of utilization of the quenching from the nanofluids group is to the hardened of elements created from constructional steels. The definition of influence size of nanofluids on the dimension changes of the element created from low carbon constructional steel is also the important aspect of this work. Design/methodology/approach: Methodology used during investigations enclosed two areas. First area enclosed the investigation of quenching mediums propriety in the support about the English method, which permitted estimate of their warmth receipt ability in the support about cooling curved in the arrangement the temperature – the time or the cooling speed. Second area enclosed the investigations of the hardened element which let define dimension changes and hardness on the transverse section. The formed structure was also estimated on the cross section in the support about the light microscope. Findings: of this article is show the possibility obtainment of minimum dimension changes the element of the cooled in nanofluids near the retained of hardness and structure on the level which was got in the quenching mediums until now used for the studied material. The summery up the use of quenching mediums of the nanofluids group at the base of distilled water, ammoniac water and Al2O3 nanoparticles causes decrease of dimension changes near keep on the same of hardness of hardened elements from constructional steel. Research limitations/implications: Research limitations result from the quantity of the quenching mediums used in the investigations which one can use as the point of the reference for nanofluids. This arose from initial investigations over this aspect, which is the dimension change of elements. It should also use real the parts of machines or tool in farther investigations. Practical implications: of results presented in this article, we will get in the range of the construction projecting of steel elements, where should consider technological surpluses for this element and material proprieties which has to which meet. For full utilization in the practice, however you should conduct additional investigations still both in the laboratory scale, how and industrial. Originality/value: Originality of this article is the performance of the influence of quenching mediums from the group nanofluids on the dimension changes of hardened steel elements.

5

Measurement of temperature-dependent viscosity and thermal conductivity of alumina and titania thermal oil nanofluids

Cieśliński J. T., Ronewicz K., Smoleń S.

Archives of Thermodynamics

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2015

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Vol. 36, no. 4

35--47

EN

In this study the results of simultaneous measurements of dynamic viscosity, thermal conductivity, electrical conductivity and pH of two nanofluids, i.e., thermal oil/Al2O3 and thermal oil/TiO2 are presented. Thermal oil is selected as a base liquid because of possible application in ORC systems as an intermediate heating agent. Nanoparticles were tested at the concentration of 0.1%, 1%, and 5% by weight within temperature range from 20°C to 60°C. Measurement devices were carefully calibrated by comparison obtained results for pure base liquid (thermal oil) with manufacturer’s data. The results obtained for tested nanofluids were compared with predictions made by use of existing models for liquid/solid particles mixtures.

6

Investigations on heat and momentum transfer in CuO-water nanofluid

Dzido G., Drzazga M., Lemanowicz M., Gierczycki A. T.

Archives of Thermodynamics

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2015

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Vol. 36, no. 2

49--59

EN

This paper presents results of investigations on the application of CuO-water nanofluids for intensification of convective heat transfer. Performance of nanofluids with 2.2 and 4.0 vol.% CuO NPs (nanoparticles) content were examined with regard to heat transfer coefficient and pressure losses in case of turbulent flow in a tube. Negligible impact of examined nanofluid on heat transfer improvement was found. Moreover, measured pressure losses significantly exceeded those determined for primary base liquid. The observations showed that application of nanofluid for heat transfer intensification with a relatively high solid load in the examined flow range is rather controversial.

7

Experimental investigation of heat transfer characteristics of nanofluid using parallel flow, counter flow and shell and tube heat exhanger

Dharmalingam R., Sivagnanaprabhu K. K., Yogaraja J., Gunasekaran S., Mohan R.

Archive of Mechanical Engineering

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2015

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Vol. LXII, nr 4

509--522

EN

Cooling is indispensable for maintaining the desired performance and reliability over a very huge variety of products like electronic devices, computer, automobiles, high power laser system etc. Apart from the heat load amplification and heat fluxes caused by many industrial products, cooling is one of the major technical challenges encountered by the industries like manufacturing sectors, transportation, microelectronics, etc. Normally water, ethylene glycol and oil are being used as the fluid to carry away the heat in these devices. The development of nanofluid generally shows a better heat transfer characteristics than the water. This research work summarizes the experimental study of the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and 1% Al2O3 (volume concentration) nanoparticle flowing in a parallel flow, counter flow and shell and tube heat exchanger under laminar flow conditions. The Al2O3 nanoparticles of about 50 nm diameter are used in this work. Three different mass flow rates have been selected and the experiments have been conducted and their results are reported. This result portrays that the overall heat transfer coefficient and dimensionless Nusselt number of nanofluid is slightly higher than that of the base liquid at same mass flow rate at same inlet temperature. From the experimental result it is clear that the overall heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate. It shows that whenever mass flow rate increases, the overall heat transfer coefficient along with Nusselt number eventually increases irrespective of flow direction. It was also found that during the increase in mass flow rate LMTD value ultimately decreases irrespective of flow direction. However, shell and tube heat exchanger provides better heat transfer characteristics than parallel and counter flow heat exchanger due to multi pass flow of nanofluid. The overall heat transfer coefficient, Nusselt number and logarithmic mean temperature difference of the water and Al2O3 /water nanofluid are also studied and the results are plotted graphically.

PL

Chłodzenie jest niezbędne dla właściwego funkcjonowania i niezawodności różnorodnych produktów, jak urządzenia elektroniczne, komputery, samochody, systemy laserowe wielkiej mocy, itp. W sytuacji wzrostu obciążenia cieplnego i strumieni ciepła wytwarzanych przez urządzenia przemysłowe, chłodzenie jest jednym z najważniejszych wyzwań występujących w różnych gałęziach przemysłu, transporcie, mikroelektronice, itp. Płynami, które zwykle są używane do odprowadzania ciepła z tych urządzeń są woda, glikol etylenowy i oleje. Nanopłyny, opracowane w ostatnim czasie, wykazują generalnie lepsze charakterystyki przewodnictwa cieplnego niż woda. Przedstawiona praca stanowi podsumowanie badań doświadczalnych nad wymuszonym, konwekcyjnym odprowadzaniem ciepła i charakterystykami przepływu nanopłynu składającego się z wody i cząsteczek Al2O3 (w 1% stężeniu objętościowym) w warunkach laminarnego przepływu współprądowego i przeciwprądowego w płaszczowych i rurowych wymiennikach ciepła. W przedstawionych badaniach użyto cząstek Al2O3 o średnicy ok. 50 nm. Wybrano trzy różne prędkości przepływu masy, opisano wyniki eksperymentów. Wyniki te wskazują, że całkowity współczynnik odprowadzania ciepła i bezwymiarowa liczba Nusselta nanopłynu są, przy tej samej prędkości przepływu masy i temperaturze na wlocie, nieznacznie wyższe, niż dla samego płynu bazowego. Z wyników doświadczalnych wynika, że całkowity współczynnik odprowadzania ciepła wzrasta wraz z prędkością przepływu masy. Pokazano, że gdy wzrasta prędkość przepływu masy, całkowity współczynnik odprowadzania ciepła wraz z bezwymiarową liczbą Nusselta ostatecznie wzrastają, niezależnie od kierunku przepływu. Stwierdzono także, że ze wzrostem prędkości przepływu masy wartość LMTD (średniej logarytmicznej różnicy temperatur) ostatecznie maleje, niezależnie od kierunku przepływu. Niemniej, płaszczowe i rurowe wymienniki ciepła zapewniają lepsze charakterystyki odprowadzania ciepła niż wymienniki z przepływem współprądowym i przeciwprądowym, co wynika z wielostrumieniowego przepływu nanopłynu. Badano także całkowity współczynnik odprowadzania ciepła, bezwymiarową liczbę Nusselta i średnią logarytmiczną różnicę temperatur dla wody i nanopłynu złożonego z wody i Al2O3, a wyniki przedstawiono w formie graficznej.

8

Magneto convection in a layer of nanofluid with soret effect

Chand R., Rana G. C.

Acta Mechanica et Automatica

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2015

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Vol. 9, no. 2

63--69

EN

Double diffusive convection in a horizontal layer of nanofluid in the presence of uniform vertical magnetic field with Soret effect is investigated for more realistic boundary conditions. The flux of volume fraction of nanoparticles is taken to be zero on the isothermal boundaries. The normal mode method is used to find linear stability analysis for the fluid layer. Oscillatory convection is ruled out because of the absence of the two opposing buoyancy forces. Graphs have been plotted to find the effects of various parameters on the stationary convection and it is found that magnetic field, solutal Rayleigh number and nanofluid Lewis number stabilizes fluid layer, while Soret effect, Lewis number, modified diffusivity ratio and nanoparticle Rayleigh number destabilize the fluid layer.

9

Wpływ nanocząstek na właściwości nanopłynów chłodniczych oraz intensywność wymiany ciepła

Charun H., Dutkowski K., Marciniak L.

Chłodnictwo : organ Naczelnej Organizacji Technicznej

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2014

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R. 49, nr 3

2--6

PL

W artykule przedstawiono przegląd aktualnego stanu wiedzy w zakresie właściwości nanopłynów chłodniczych. Analiza dotyczy zarówno wpływu nanocząstek na właściwości termodynamiczne nanopłynów chłodniczych, jak i na intensywność wymiany ciepła. Na podstawie wyników badań rożnych autorów stwierdzono, że wzrost stężenia nanocząstek zawieszonych w cieczy bazowej - czynniku chłodniczym - wpływa znacząco na wzrost wymiany ciepła. Podane przykłady wskazują na wzrost wartości współczynnika przejmowania (wnikania) ciepła nanopłynów chłodniczych w warunkach ich wrzenia w objętości jak i w przepływie. Podkreślono konieczność prowadzenia dalszych intensywnych badań eksperymentalnych i teoretycznych z nanopłynami chłodniczymi.

EN

An overview of the current state of knowledge on nanorefrigerant properties in this article is presented. The analysis applies the impact of nanoparticles on the thermodynamic properties of nanorefrigerant and their influence on heat transfer intensity. Based on the results of various authors it was found that the increase in the concentration of nanoparticles suspended in a base liquid - refrigerant - increase significantly the heat transfer. Presented examples pointed the increase of the nanorefrigerant heat transfer coefficient under their pool boiling and flow boiling. The need for further intensive experimental and theoretical research on nanorefrigerants properties is stressed.

10

Pool boiling of nanofluids on rough and porous coated tubes: experimental and correlation

Cieśliński J. T., Kaczmarczyk T. Z.

Archives of Thermodynamics

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2014

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Vol. 35, no. 2

3--20

EN

The paper deals with pool boiling of water-Al2O3 and water-Cu nanofluids on rough and porous coated horizontal tubes. Commercially available stainless steel tubes having 10 mm outside diameter and 0.6 mm wall thickness were used to fabricate the test heater. The tube surface was roughed with emery paper 360 or polished with abrasive compound. Aluminium porous coatings of 0.15 mm thick with porosity of about 40% were produced by plasma spraying. The experiments were conducted under different absolute operating pressures, i.e., 200, 100, and 10 kPa. Nanoparticles were tested at the concentration of 0.01, 0.1, and 1% by weight. Ultrasonic vibration was used in order to stabilize the dispersion of the nanoparticles. It was observed that independent of operating pressure and roughness of the stainless steel tubes addition of even small amount of nanoparticles augments heat transfer in comparison to boiling of distilled water. Contrary to rough tubes boiling heat transfer coefficient of tested nanofluids on porous coated tubes was lower compared to that for distilled water while boiling on porous coated tubes. A correlation equation for prediction of the average heat transfer coefficient during boiling of nanofluids on smooth, rough and porous coated tubes is proposed. The correlation includes all tested variables in dimensionless form and is valid for low heat flux, i.e., below 100 kW/m2.

11

Numerical simulation of nanofluid flow in a small diameter pipe

Lemanowicz M., Dzido G., Gierczycki A., Witkowski M., Drzazga M.

Inżynieria i Aparatura Chemiczna

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2013

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Nr 6

541--542

PL

Przedstawiono efekty badań dotyczących spadku ciśnienia przy przepływie nanopłynu przez kanał o malej średnicy. Wyniki eksperymentalne porównano z rezultatami symulacji z wykorzystaniem numerycznej mechaniki płynów (CFD). Zbadano przepływ nanocząstek tlenku miedzi zawieszonych w wodzie przez przewód cylindryczny o średnicy 12 mm. W symulacjach wykorzystano zarówno podejście jednofazowe jak i wielofazowe. Wykazano, iż oba sposoby prowadzenia symulacji dały podobne rezultaty.

EN

The research concerning nanofluid pressure drop during flow through a small diameter pipe is presented. Experimental results are compared with the computational fluid dynamics (CFD) simulations. The flow of copper nanoparticles suspended in water through the cylindrical tube of 12 mm diameter was investigated. In simulations single-phase as well as multiphase approaches were employed. It was proven that both ways of simulations gave similar results.

12

Możliwość zastosowania nanopłynów jako nośników ciepła w obiegach chłodniczych i klimatyzacyjnych

Charun H., Dutkowski K., Marciniak L.

Chłodnictwo : organ Naczelnej Organizacji Technicznej

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2013

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R. 48, nr 12

4--10

PL

Przedstawiono aktualny stan wiedzy w zakresie stosowania nanopłynów w układach wymiany ciepła. Nanopłyny dziełu swoim nietypowym właściwościom, zwłaszcza przewodnictwu cieplnemu, są nowym typem nośnika ciepła stanowiącym alternatywę dla klasycznych, dotychczas stosowanych nośników. Opisano metody przygotowania nanopłynów, od których zależą ich właściwości. Szczególną uwagę poświęcono metodom zmierzającym do zapewnienia stabilności nanopłynów na bazie wody, glikolu i czynników chłodniczych. Wykazano, że kontynuowane badania nad właściwościami nanopłynów zmierzają do wyeliminowania ich wad, a w szczególności zmniejszenia tendencji do sedymentacji i agregacji.

EN

The current state of knowledge regarding the use of nanofluid as a working fluid in heat exchangers is presented. Nanofluids due to their unusual properties, especially thermal conductivity, are a new type of heat transfer medium constitutes an alternative to classical media. Methods for nanofluid preparation, on which nanofluid properties depends, are described. Particular attention is given to methods to ensure the stability of water-, glycol- and refrigerant- based nanofluids. It has been shown that continued research on nanofluids characteristics seek to eliminate their disadvantages, in particular, to reduce the sedimentation and aggregation tendency.

13

Określenie efektowności współczynnika przewodnictwa cieplnego nanopłynów a pomocą wzorów analitycznych

Stanek M., Drzazga M., Thullie J.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 6

24-27

PL

W pracy dokonano przeglądu literaturowego istniejących formuł analitycznych dla określenia przewodnictwa cieplnego nanopłynów. Stwierdzono, że pomimo znacznego wysiłku nie udało się uzyskać wzorów ogólnych o zadowalającej dokładności. Uzyskano natomiast szereg wzorów godnych zalecenia dla konkretnych przypadków szczególnych. Słowa kluczowe: współczynnik przewodzenia ciepła, metody obliczeniowe, nanopłyny

EN

The paper presents literature survey on analytical prediction of effective thermal conductivity of nanofluids. It was found that regardless big efforts a general formula of sufficient accuracy was not obtained. However, a number of trusted in specific cases equations were obtained.

14

Charakterystyka przewodnictwa cieplnego nanopłynów zawierających cząstki Al2O3

Bakalarz J., Thullie J., Kurowski Ł., Wiśniowski T., Palica M.

Inżynieria i Aparatura Chemiczna

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2010

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Nr 6

21-23

PL

W pracy przedstawiono formułę do obliczania efektywnego współczynnika przewodzenia ciepła nanopłynów zawierających cząstki A1203 możliwą do wykorzystania przy obliczeniach numerycznych. Zaproponowano również metodę postępowania dla przypadku, gdy wyniki estymacji prowadzą do rezultatu niezgodnego z fizyką procesu.

EN

A dependence for numerical calculations of effective thermal conductivity coefficient of nanofluids containing A1203 particles is presented in the paper. A procedure in case when the estimation leads to results inconsistent with physics of the process is also proposed.