AFDASC

Project code: PN-III-P4-ID-PCE-2020-0353

Contract number: ID 241/2021

Financing institution:

Executive Agency for Higher Education, Research, Development and Innovation Funding, Romania

Unitatea Executiva pentru Finantarea Invatamantului Superior a Cercetarii, Dezvoltarii si Inovarii (UEFISCDI)

Financing program: EXPLORATORY RESEARCH PROJECTS

Project coordinator: Transilvania University of Brasov, Romania -Prof.dr.habil.ing. Gabriela HUMINIC

Project duration: 36 months: 01.04.2021 - 31.03.2024

Abstract:

Hybrid nanofluids (HNFs) are a new method of improving convective heat transfer. These are working fluids made by adding complex nanoparticles or by mixing two or more different solid particles in the base fluid (water, ethylene glycol, oil).

One of the most useful applications of hybrid nanofluids is their use in direct absorption solar collectors (DASCs), where the sunlight is absorbed directly by the nanofluid. Because most conventional working fluids (eg water and ethylene glycol) have low absorption coefficients, it follows that the addition of nanoparticles to conventional fluids has the effect of improving both the optical properties and the efficiency of solar collectors.

Due to their improved thermal and optical properties, HNFs can be used in various solar energy applications, being an attractive solution for improving overall thermal efficiency.

Objectives

The aim of the project is to develop new hybrid solar nanofluids with improved thermal and optical properties that lead to increased DASC performance.

O1. Development of novel hybrid nanofluids with optimized compositions (particle types, size and distribution, and loadings) and appropriate thermophysical and optical properties.

O2. Development of experimental techniques to characterize of the thermo-physical properties (thermal conductivity, viscosity, density, surface tension) and stability.

O3. Analytical modeling and experimental investigation on optical properties (transmittance, and extinction coefficients) of HNfs.

O4. Experimental study on solar energy absorption performance and photothermal conversion efficiency of HNfs.

O5. Development of hybrid nanofluids with large thermal and optical properties enhancements. 

O6. Experimental investigation of the performance characteristics of a residential-type direct absorption solar collector using HNfs.

Team members

Project leader: Prof. dr. habil. ing. Gabriela HUMINIC https://www.scopus.com/authid/detail.uri?authorId=24491895600

Members:

Prof. dr. habil. ing. Angel HUMINIC  https://www.scopus.com/authid/detail.uri?authorId=24492157400

Dr. fiz. Florian DUMITRACHE https://www.scopus.com/authid/detail.uri?authorId=8299140500

Dr. chim. Claudiu FLEACĂ https://www.scopus.com/authid/detail.uri?authorId=7801361494

Ing. Alexandru VĂRDARU https://www.scopus.com/authid/detail.uri?authorId=57359326500

Ing. Anda DUDĂU

Activities carried out during the implementation period (April 2021-March 2024)

The aim of the project is to develop new working fluids with improved thermo-physical and optical properties to be used in direct absorption solar collectors (DASC) in order to improve their performance. In the first stage of the project, parametric studies were carried out to optimize the synthesis process of NPs (iron oxide, composite iron-based core and carbon shell, slightly non-stoichiometric titanium dioxide) by laser pyrolysis relative to their morpho-structural properties, stoichiometric control and magnetic properties (iron-based NPs). Dilute suspensions of Ag NPs with rGO (reduced graphene oxide) were prepared, as well as more concentrated suspensions of Ag NPs (by reduction with NaBH4 in the presence of CMCNa) in which each of the 3 types of synthesized NPs were dispersed by laser pyrolysis. A preparation procedure of such aqueous or mixed aqueous-ethylene glycol suspensions stabilized with CMCNa based on these types of NPs at various concentrations was implemented. EDS, SEM, TEM and XPS analyzes were carried out for the stabilized nanostructures and DLS measurements of the hybrid nanofluids. The new hybrid suspensions of Ag NPs with rGO, Fe₂O₃, Fe@C and TiO₂-x in water, as well as in water-ethylene glycol mixture, were characterized from a thermophysical point of view. Thermophysical properties, especially thermal conductivity, have a significant role in determining the overall performance of nanofluids as working fluids in solar collectors. Thus, experimental studies were carried out for the thermal conductivity and dynamic viscosity of the new hybrid nanofluids at different mass concentrations of nanoparticles and temperatures. Finally, property-parameter correlations were proposed for each type of suspension (thermal conductivity – temperature – concentration of nanoparticles and dynamic viscosity – temperature – concentration of nanoparticles). In the second stage of the project, experimental studies were carried out on the physical (surface tension and density) and optical (transmittance, absorbance and extinction coefficient) properties of hybrid suspensions of Ag NPs with rGO, Fe₂O₃, Fe@C and TiO₂-x in water, as well as in water-ethylene glycol mixture, at different mass concentrations of nanoparticles and temperatures. For each type of suspension, property-parameter correlations were proposed (surface tension-concentration-temperature, density-concentration-temperature). Also, the effects of the optical path and the nanoparticle concentration on the transmittance and absorbance of the base fluids and hybrid nanofluids were studied. Beer-Lambert's law was used to analytically evaluate the extinction coefficient of nanofluids with different particle mass concentrations. Using a solar simulator, the performance of hybrid nanofluids was determined for use in a DASC system. The results indicated that the nanofluids proposed for the study can be used in direct absorption solar collectors under a short solar irradiation time and at a low illumination intensity. In the third stage of the project, two direct absorption solar collectors from laminated glass were designed and build, and their testing facility was also made. The solar collectors were tested with water-ethylene glycol mixture (1:1) and with Ag and rGO nanoparticles dispersed in water-ethylene glycol with a mass concentration of 0.1%. The testing of the two prototypes was carried out in parallel at different flow rates 0.5, 0.8, 1.0 and 1.5 l/min and inlet temperatures, 20 and 30, during August-October, according to the EN-12975-2 standard. The prepared suspension (5 liters) of AgNPs+rGO was found to be very stable over time without sedimentation or agglomeration under repeated exposure to the Sun. The results of the study show a new class of working fluids that can be used to achieve high thermal conversion efficiency, which are more stable and can generate significant energy savings. In the fourth stage of the project, a correlation was established for the average Nusselt number, valid both for the solar collector with water and ethylene glycol, as well as for the one that uses Ag nanoparticles and reduced graphene oxide as working fluid (Ag NPs+rGO ) dispersed in the mixture of water and ethylene glycol, which takes into account the ratio Dh/L and the angle of inclination of the solar collector in relation to the horizontal.

 The solar collectors designed, built and tested within this project constitute a new technology for converting solar energy into thermal energy. The obtained results indicate a new class of working fluids that can be used to obtain high thermal conversion efficiency, which are stable and which can generate important energy savings.

Results:

2021:  Articles published in ISI journals:

1. Huminic A., Huminic G., Fleaca C., Dumitrache F., Morjan I.,  Influence of solid surface, temperature and concentration on contact angle of water-FeC nanofluid, International Communications in Heat and Mass Transfer, 2021, 128, 105650, FI: 5.683 (Q1).

2. Huminic G., Huminic A., Thermophysical properties of NH₃/IL+ carbon nanomaterial solutions, Nanomaterials, 2021, 11(10), 2612, FI: 5.076 (Q1).

 2022: 

Articles published in ISI journals:

1. Vărdaru, A., Huminic, G., Huminic, A., Fleaca, C., Dumitrache, F., Morjan, I., Synthesis, Characterization and thermal conductivity of water based graphene oxide–silicon hybrid nanofluids: An experimental approach, Alexandria Engineering Journal, 2022, 61(12), 12111–12122, FI: 6.626 (Q1).

2. Huminic, G., Huminic, A., Heat and mass transfer characteristics of the NH3/IL + GNPs solution, Journal of Molecular Liquids, 2022, 348, 118073, FI: 6.633 (Q1).

3. Chereches, M., Vărdaru, A., Huminic, G., Chereches, E.I., Minea, A.A., Huminic, A. Thermal conductivity of stabilized PEG 400 based nanofluids: An experimental approach, International Communications in Heat and Mass Transfer, 2022, 130, 105798, FI: 6.782 (Q1).

4. Huminic, G., Vărdaru, A., Huminic, A., Fleaca, C., Dumitrache, F., Morjan, I., Water-Based Graphene Oxide–Silicon Hybrid Nanofluids—Experimental and Theoretical Approach International Journal of Molecular Sciences, 2022, 23(6), 3056, FI: 6.208 (Q1).

Conferences ISI indexed : 

1. Vărdaru, A., Huminic, G., Huminic, A., Thermal conductivity of Ag-rGO/water hybrid nanofluids: An experimental approach, ACME 2022, IOP Conf. Series: Materials Science and Engineering 1262 (2022) 012086.

Book chapters:

1. Huminic, G., Huminic, A., Minea, A.A., Heat and mass transfer characteristics of magnetic nanofluids, capitol in “Nanofluids and Mass Transfer”, 2022, pp. 133–187, Elsevier, ISBN 978-012823996-4, doi: 10.1016/B978-0-12-823996-4.00006-9.

2. Minea, A.A., Huminic, A., Huminic, G., Conjugate heat and mass transfer in nanofluids, capitol in “Nanofluids and Mass Transfer”, 2022, pp. 189–215, Elsevier, ISBN 978-012823996-4, doi: 10.1016/B978-0-12-823996-4.00005-7.

2023: 

Articles published in ISI journals:

1.      Huminic, G., Huminic, A., Vărdaru, A., Fleaca, C., Dumitrache, F., Morjan, I., Surface tension of Ag NPs-rGO based hybrid nanofluids, Journal of Molecular Liquids 390 (2023) 123002, FI: 6.0.

 2.  Vărdaru, A., Huminic, G., Huminic, A., Fleaca, C., Dumitrache, F., Morjan, I., Aqueous hybrid nanofluids containing silver-reduced graphene oxide for improving thermo-physical properties, Diamond & Related Materials 132 (2023) 109688, FI: 4.1.

Conferences ISI indexed : 

1. Vărdaru, A., Huminic, G., Huminic, A., Study of hybrid nanofluids used in direct absorption solar collectors, 2023, IOP Conf. Series: Materials Science and Engineering 1290 (2023) 012003.

2. Dumitrache, F., Fleaca, C., Huminic, G., Huminic, A., Gavrila-Florescu, L., Goncearenco, E., Banici, A.-M., Morjan, I.P., Lungu, I., Tanasa E., High yield C- SiC composite nanoparticles synthesized by laser pyrolysis and their application for thermal transfer as aqueous nanofluids, E-MRS 2023 Spring Meeting, Strasbourg – Franta.

2024: 

Articles published in ISI journals:

1. Huminic, G., Huminic, A., Vărdaru, A., Dumitrache, F., Fleaca, C., Experimental investigation on Ag NPs-rGO -water/ethylene-glycol hybrid nanofluids used in solar applications, Diamond & Related Materials 143 (2024) 110851, FI=4.1.

2. Huminic, G., Huminic, A., Capabilities of advanced heat transfer fluids on the performance of flat plate solar collector, Energy Reports 11 (2024) 1945–1958, FI=5.2.

3. Yalçın, G., Huminic, G., Huminic, A., Panchal, H., Dalkılıç, A.S., Investigation on effect of surfactants on the viscosity of graphite water based nanofluids, Journal of Molecular Liquids 398 (2024) 124197 FI=6.0.

Contact:

Gabriela HUMINIC