PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS
This study examines the thermal performance enhancement of a flat plate solar collector (FPSC) using Al₂O₃–Cu hybrid nanofluids as the working fluid. Hybrid nanofluids, formulated by combining metal-oxide and metallic nanoparticles, offer superior thermophysical properties compared to conventional f...
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| Дата: | 2026 |
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Vidnovluvana energetika| _version_ | 1871104096520372224 |
|---|---|
| author | Sekharraj , K. Balu, P. Srilaxmi , Dasari Nimmala , Harathi Ravi , S. Ivanchuk , V. |
| author_facet | Sekharraj , K. Balu, P. Srilaxmi , Dasari Nimmala , Harathi Ravi , S. Ivanchuk , V. |
| author_institution_txt_mv | [
{
"author": "K. Sekharraj ",
"institution": "Bharath Institute of Higher Education and Research (BIST), Chennai, Tamil Nadu, India"
},
{
"author": " P. Balu",
"institution": "Bharath Institute of Higher Education and Research (BIST), Chennai, Tamil Nadu, India"
},
{
"author": "Dasari Srilaxmi ",
"institution": "VNR Vignana Jyothi Institute of Engineering and Technology, Hyderabad, India"
},
{
"author": "Harathi Nimmala ",
"institution": "Siddharth Institute of Engineering & Technology, Andhra Pradesh, India"
},
{
"author": "S. Ravi ",
"institution": "Chennai Institute of technology, Chennai, India"
},
{
"author": "V. Ivanchuk ",
"institution": "Institute of Renewable Energy, NAS of Ukraine, Kyiv, Ukraine"
}
] |
| author_sort | Sekharraj , K. |
| baseUrl_str | https://ve.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-18T06:32:24Z |
| description | This study examines the thermal performance enhancement of a flat plate solar collector (FPSC) using Al₂O₃–Cu hybrid nanofluids as the working fluid. Hybrid nanofluids, formulated by combining metal-oxide and metallic nanoparticles, offer superior thermophysical properties compared to conventional fluids. In this work, Al₂O₃ and Cu nanoparticles were dispersed in distilled water at low volume concentrations (0.05–0.15%) using ultrasonication, and their thermal conductivity, viscosity, and stability were characterized. Experiments were conducted under real-time solar radiation to evaluate useful heat gain and instantaneous thermal efficiency of the FPSC. Results show that hybrid nanofluids significantly enhance heat transfer, with thermal conductivity increasing by up to 22% compared to water. The collector’s useful heat gain improved by 18–28%, and the instantaneous efficiency increased by 12–20% depending on nanoparticle concentration. These improvements are attributed to enhanced thermal conductivity, intensified convective heat transfer, and synergistic effects between the nanoparticles. The findings demonstrate that Al₂O₃–Cu hybrid nanofluids are promising next-generation heat transfer fluids for high-performance solar thermal systems. |
| doi_str_mv | 10.36296/1819-8058.2026.1(84).137-144 |
| first_indexed | 2026-03-31T01:00:06Z |
| format | Article |
| fulltext |
137
Відновлювана енергетика. № 1/2026 | Сонячна енергетика
https://doi.org/10.36296/1819-8058.2026.1(84).137-144
PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR
USING AL₂O₃–CU HYBRID NANOFLUIDS
Received Jan. 02, 2026; accepted Mar. 23, 2026
Available online Mar. 31, 2026
Sekharraj K.1, Balu P.2, Srilaxmi Dasari3,
Nimmala Harathi4, Ravi S.5, Ivanchuk V.6
Author for correspondence: Balu Pandian
e-mail: balumitauto@gmail.com
Abstract. This study examines the thermal performance en-
hancement of a flat plate solar collector (FPSC) using Al₂O₃–
Cu hybrid nanofluids as the working fluid. Hybrid nanofluids,
formulated by combining metal-oxide and metallic nanopar-
ticles, offer superior thermophysical properties compared to
conventional fluids. In this work, Al₂O₃ and Cu nanoparticles
were dispersed in distilled water at low volume concentra-
tions (0.05–0.15%) using ultrasonication, and their thermal
conductivity, viscosity, and stability were characterized. Ex-
periments were conducted under real-time solar radiation to
evaluate useful heat gain and instantaneous thermal effi-
ciency of the FPSC. Results show that hybrid nanofluids sig-
nificantly enhance heat transfer, with thermal conductivity
increasing by up to 22% compared to water. The collector’s
useful heat gain improved by 18–28%, and the instantaneous
efficiency increased by 12–20% depending on nanoparticle
concentration. These improvements are attributed to en-
hanced thermal conductivity, intensified convective heat
transfer, and synergistic effects between the nanoparticles.
The findings demonstrate that Al₂O₃–Cu hybrid nanofluids are promising next-generation heat transfer fluids for
high-performance solar thermal systems.
Key words: Hybrid nanofluids; Al₂O₃–Cu nanofluid; Flat plate solar collector; Thermal efficiency; Heat transfer
enhancement; Solar thermal systems; Thermophysical properties.
ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ПЛАСКОГО СОНЯЧНОГО КОЛЕКТОРА
ЗА РАХУНОК ВИКОРИСТАННЯ ГІБРИДНИХ НАНОРІДИН AL₂O₃–CU
Отримано 02 січ. 2026 р.; рекомендовано до публікації 23 бер. 2026 р.
Доступно онлайн 31 бер. 2026 р.
Секхаррадж К.¹, Балу П.², Шрілакшмі Дасарі³,
Німмала Хараті⁴, Раві С.⁵, Іванчук В.⁶
Автор для кореспонденції: Балу Пандіан
e-mail: balumitauto@gmail.com
Анотація. У цій роботі досліджено підвищення тепло-
вої ефективності плоского сонячного колектора (FPSC)
за рахунок використання гібридних нанорідин Al₂O₃–Cu
як робочого теплоносія. Гібридні нанорідини, отримані
шляхом поєднання наночастинок оксидів металів і ме-
талевих наночастинок, мають кращі термофізичні
властивості порівняно з традиційними теплоносіями.
У цій роботі наночастинки Al₂O₃ та Cu диспергували у
1 Research Scholar,
Department of Automobile Engineering
https://orcid.org/ 0009-0004-3562-9957
2 Associate Professor,
Department of Automobile Engineering
https://orcid.org/ 0000-0003-3480-1116
3 Assistant Professor,
Department of Electronics and
Instrumentation Engineering
https://orcid.org/0000-0002-4745-7943
4 Department of Electronics & Communications
https://orcid.org/0000-0002-0674-6730
5 Professor, Department
of Mechanical Engineering
https://orcid.org/0000-0002-0254-105X
6 PhD (Tech.), Research Assistant
https://orcid.org/0000-0002-0585-9610
1, 2 Bharath Institute of Higher Education and
Research (BIST), Chennai, Tamil Nadu, India
3 VNR Vignana Jyothi Institute of Engineering and
Technology, Hyderabad, India
4 Siddharth Institute of Engineering &
Technology, Andhra Pradesh, India
5 Chennai Institute of technology, Chennai, India
6 Institute of Renewable Energy, NAS of Ukraine,
Kyiv, Ukraine
1 аспірант кафедри автомобільної інженерії
https://orcid.org/ 0009-0004-3562-9957
2 доцент кафедри автомобільної інженерії
https://orcid.org/ 0000-0003-3480-1116
3 доцент кафедри електроніки
та приладобудування
https://orcid.org/0000-0002-4745-7943
4 кафедра електроніки та комунікацій
https://orcid.org/0000-0002-0674-6730
5 професор кафедри машинобудування
https://orcid.org/0000-0002-0254-105X
6 канд. техн. наук, мол. наук. співроб.
https://orcid.org/0000-0002-0585-9610
1, 2 Інститут вищої освіти та досліджень
Бхарата (BIST), м. Ченнаї, штат Тамілнад, Індія
3 Інститут інженерії та технологій «VNR Vignana
Jyothi», м. Хайдарабад, Індія
4 Інженерно-технологічний інститут Сіддхартха,
штат Андхра-Прадеш, Індія
5 Ченнайський інститут технологій, м. Ченнаї,
138
Відновлювана енергетика. № 1/2026 | Сонячна енергетика
дистильованій воді при низьких об’ємних концентра-
ціях (0,05–0,15%) із застосуванням ультразвукової об-
робки, після чого було визначено їхню теплопровід-
ність, в’язкість і стабільність. Експерименти прово-
дили в умовах реального сонячного випромінювання з
метою оцінювання корисного теплового надхо-
дження та миттєвої теплової ефективності плос-
кого сонячного колектора. Результати дослідження
доводять, що використання гібридних нанорідин сут-
тєво підвищує інтенсивність теплопередачі: тепло-
провідність зросла до 22% у порівнянні з водою. Корисне теплове надходження колектора збільшилося
на 18–28%, а миттєвий коефіцієнт корисної дії зріс на 12–20% залежно від концентрації наночастинок.
Зазначене покращення ефективності пояснюється підвищенням теплопровідності, інтенсифікацією
конвективного теплообміну та синергетичним ефектом взаємодії наночастинок. Отримані резуль-
тати свідчать, що гібридні нанорідини Al₂O₃–Cu є перспективними теплоносіями нового покоління для
використання у високоефективних сонячних теплових установках.
Ключові слова: гібридні нанорідини; нанорідина Al₂O₃–Cu; плоский сонячний колектор; теплова ефекти-
вність; інтенсифікація теплопередачі; сонячні теплові установки; термофізичні властивості.
1. Introduction
Solar energy is one of the most promising renewable re-
sources for meeting global energy demand while minimiz-
ing environmental impacts. Among various solar thermal
technologies, the flat plate solar collector (FPSC) is widely
used for water heating, space heating, solar drying, and in-
dustrial preheating applications due to its simple construc-
tion, low cost, and reliable operation. However, the perfor-
mance of FPSCs is often limited by the low thermal conduc-
tivity and relatively poor heat transfer characteristics of tra-
ditional working fluids such as water, ethylene glycol, and
their mixtures [1]. Nanotechnology has introduced new
pathways to overcome these limitations through the devel-
opment of nanofluids, which are engineered colloidal sus-
pensions of nanoparticles dispersed in base fluids. Nanoflu-
ids exhibit superior thermophysical properties such as en-
hanced thermal conductivity, improved convective heat
transfer, and modified viscosity behavior. Despite these ad-
vantages, single-component nanofluids often face stability
issues and may not provide the desired level of heat trans-
fer enhancement under varying operating conditions [2].
To address these challenges, researchers have developed
hybrid nanofluids, formulated by combining two different
types of nanoparticles in a single base fluid. Hybrid nanoflu-
ids leverage the synergistic effects of their constituents, of-
fering improved thermal conductivity, enhanced stability,
and more efficient energy transport compared to mono-
nanofluids. Among the various combinations investigated,
Al₂O₃–Cu hybrid nanofluid has gained significant attention
due to the high thermal conductivity of copper nanoparti-
cles and the excellent chemical stability of alumina nano-
particles. This combination results in a balanced, high-per-
formance working fluid suitable for solar thermal systems
[3]. Numerous studies have demonstrated that dispersing
nanoparticles in base fluids can significantly enhance the
thermal performance of solar collectors. [4] reported a sub-
stantial increase in thermal conductivity when metallic na-
noparticles were used in water. Similarly, [5] found that
using Al₂O₃–water nanofluid improved the efficiency of
FPSCs by 15%, mainly due to improved heat absorption and
enhanced convective currents. Experimental investigations
by [6] further confirmed that metal-oxide nanofluids such
as Al₂O₃, TiO₂, and CuO enhance optical absorption, reduce
thermal resistance, and improve collector heat gain. How-
ever, mono-nanofluids often face issues such as particle ag-
glomeration, instability, and suboptimal enhancement at
low concentrations. Hybrid nanofluids, which combine two
or more nanoparticles, have recently emerged as a promis-
ing alternative due to their synergistic thermal effects, bet-
ter stability, and higher effective thermal conductivity. [7]
demonstrated that Al₂O₃–Cu hybrid nanofluids exhibit
higher thermal conductivity than their individual counter-
parts, even at very low particle concentrations. The en-
hanced performance is attributed to improved Brownian
motion, multi-particle interaction, and enhanced micro-
convection within the fluid. [8] reported improvements in
heat transfer coefficients and reduced thermal boundary
layer thickness in hybrid nanofluids flowing through heat
exchangers. [9] also observed a 13–17% increase in convec-
tive heat transfer using hybrid Al₂O₃–Cu nanofluid com-
pared to mono-nanofluids. These findings indicate that hy-
brid nanofluids can provide substantial thermal improve-
ments without requiring high particle loading, which helps
minimize pumping power and viscosity-related penalties.
The introduction of hybrid nanofluids to solar thermal sys-
tems has shown positive results. [10] investigated CuO–
Al₂O₃ hybrid nanofluid in solar collectors and found en-
hanced heat absorption and improved energy utilization.
[11] demonstrated that hybrid nanofluid-based FPSCs
yielded higher temperature rise and exergy efficiency. [12]
reported that hybrid nanofluids increase solar radiation ab-
sorption due to improved optical depth and reduced reflec-
tivity, resulting in improved collector outlet temperature.
Their research indicated that hybrid nanofluids can offer 8–
20% improvement in collector efficiency, depending on na-
noparticle composition and concentration.
1, 2 Інститут вищої освіти та досліджень
Бхарата (BIST), м. Ченнаї, штат Тамілнад, Індія
3 Інститут інженерії та технологій «VNR Vignana
Jyothi», м. Хайдарабад, Індія
4 Інженерно-технологічний інститут Сіддхартха,
штат Андхра-Прадеш, Індія
5 Ченнайський інститут технологій, м. Ченнаї,
Індія
6 Інститут відновлюваної енергетики НАН
України, м. Київ, Україна
139
Відновлювана енергетика. № 1/2026 | Сонячна енергетика
Several studies have reported that hybrid nanofluids can
significantly increase heat transfer rates, reduce thermal
resistance, and enhance collector efficiency. However, the
magnitude of improvement depends on factors such as na-
noparticle size, concentration, mixing ratio, flow rate, and
the design of the collector. Despite promising laboratory-
scale results, systematic experimental evaluation of Al₂O₃–
Cu hybrid nanofluid in real-time FPSC operation remains
limited. Therefore, this study aims to investigate the impact
of using Al₂O₃–Cu hybrid nanofluids on the thermal perfor-
mance of a flat plate solar collector under actual solar radi-
ation conditions. This work provides new experimental in-
sights into the potential of hybrid nanofluids as next-gener-
ation working fluids for solar thermal applications, contrib-
uting to improved system efficiency and enhanced utiliza-
tion of renewable energy resources.
2. Materials and Methods
2.1 Materials
Al₂O₃ and Cu nanoparticles were procured with average
particle sizes ranging from 20 to 50 nm and purity above
99%. Distilled water was used as the base fluid due to its
high specific heat and widespread applicability in solar ther-
mal systems. A small amount of sodium dodecyl sulfate
(SDS) surfactant was used in some samples to improve dis-
persion stability, though most tests relied solely on me-
chanical stabilization. All chemicals and nanoparticles were
handled using laboratory safety procedures to prevent con-
tamination or agglomeration, ensuring reliable preparation
of hybrid nanofluid samples.
2.2 Preparation of Al₂O₃–Cu Hybrid Nanofluid
The hybrid nanofluid was prepared using the two-step
method. Al₂O₃ and Cu nanoparticles were first weighed to
achieve the desired volume concentrations (0.05%, 0.10%,
and 0.15%) with a fixed mixing ratio of 70:30 to balance
high thermal conductivity with good chemical stability. The
nanoparticles were gradually added to distilled water while
being magnetically stirred for 30 minutes to avoid clump-
ing. Following this, the mixture was subjected to probe ul-
trasonication for 1–2 hours to break down agglomerates
and ensure uniform dispersion. Prepared samples were
stored in sealed containers and observed visually to check
sedimentation before experimentation (Fig. 1).
Fig. 1. Preparation of Al₂O₃–Cu Hybrid Nanofluid
2.3 Measurement of Thermophysical Properties
The thermal conductivity of the hybrid nanofluid was meas-
ured using a transient hot-wire apparatus, which provides
high accuracy for nanofluid systems. Viscosity was deter-
mined using a Brookfield digital viscometer operating at a
controlled temperature to minimize the effect of thermal
fluctuations. Density was measured gravimetrically by re-
cording the mass of known volumes of nanofluid, while spe-
cific heat capacity was estimated using mixture models
commonly employed in nanofluid studies. All measure-
ments were repeated three times to ensure repeatability,
and the average values were used in the performance anal-
ysis (Table 1).
Table 1. Thermophysical Properties of Al₂O₃–Cu Hybrid Nanofluid
Property
Base Fluid
(Water)
Al₂O₃ Nanoparticles
Cu
Nanoparticles
Hybrid Nanofluid (0.1–0.3% φ)
Density (kg/m³) 997 3970 8960 1005–1030
Specific Heat (J/kg·K) 4180 765 385 4100–3950
Thermal Conductivity
(W/m·K)
0.613 36 401 0.75–0.95
Viscosity (mPa·s) 0.89 — — 0.92–1.15
pH Value 7.1 — — 7.0–7.4
Stability Duration — — — 48–72 hours (with surfactant)
3. Experimental Setup
The experimental setup for evaluating the performance of
the flat plate solar collector using Al₂O₃–Cu hybrid nano-
fluid is illustrated schematically (Fig. 2). The system consists
of a standard flat plate solar collector placed at an optimal
tilt angle to capture maximum solar radiation. Sunlight
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Відновлювана енергетика. № 1/2026 | Сонячна енергетика
passes through the transparent glass cover and reaches the
black-coated absorber plate, where heat is transferred to
the hybrid nanofluid circulating inside the copper riser
tubes. A centrifugal pump circulates the hybrid nanofluid
through the collector in a closed-loop arrangement. The
fluid enters the collector at the inlet (T_in) and exits at the
outlet after gaining heat (Table 2). A flow meter is installed
along the inlet line to maintain the required mass flow rate.
K-type thermocouples are positioned at the inlet and outlet
to measure real-time temperature variations of the work-
ing fluid. A pyranometer placed near the collector
measures the incident solar radiation throughout the ex-
periment. All sensor outputs are connected to a data acqui-
sition system for continuous monitoring and recording of
temperature, radiation intensity, and flow rate. This setup
enables accurate determination of useful heat gain and in-
stantaneous thermal efficiency of the solar collector when
operating with hybrid nanofluid (Table 3).
Fig. 2. Experimental Setup
Table 2. Experimental Conditions for Flat Plate Collector
Testing
Parameter Value
Collector Area 1.5 m²
Absorber Plate Material Copper (0.5 mm thick)
Absorber Coating Black chrome
Number of Glass Covers 1
Glass Thickness 4 mm
Mass Flow Rate 0.02–0.06 kg/s
Inlet Fluid Temperature 30–32°C
Ambient Temperature 28–35°C
Nanofluid Concentration 0.1%, 0.2%, 0.3% vol.
Test Duration 9:00 AM – 4:00 PM
Table 3. Uncertainty Analysis
Parameter Accuracy Uncertainty
Temperature Sensor ±0.1°C 0.25%
Flow Meter ±0.01 L/s 1.2%
Parameter Accuracy Uncertainty
Solarimeter ±10 W/m² 2.0%
Overall Heat Gain — 3.2%
Collector Efficiency — 3.8%
4. Results and Discussion
4.1 Temperature Rise across the Collector
The temperature difference between the inlet and outlet of
the solar collector increased significantly when hybrid
nanofluids were used in place of water. Fig. 3 (Temperature
vs. Time) would show that the outlet temperature consist-
ently remained higher for all nanoparticle concentrations
tested. For pure water, the average temperature rise was
8–10°C, whereas the 0.05%, 0.10%, and 0.15% Al₂O₃–Cu hy-
brid nanofluids recorded temperature rises of 11.2°C,
13.4°C, and 15.1°C, respectively. This enhancement is at-
tributed to the superior thermal conductivity of the hybrid
nanofluid, which facilitates more efficient absorption and
transport of heat within the riser tubes [13]. The presence
of copper nanoparticles increases the rate of heat conduc-
tion due to their high thermal conductivity, while alumina
nanoparticles contribute to improved stability. This synergy
enables a more effective heat transfer process, leading to
higher outlet temperatures [14].
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Відновлювана енергетика. № 1/2026 | Сонячна енергетика
Fig. 3. Outlet Temperature Vs Time
4.2 Useful Heat Gain
This graph presents the useful heat gain of the solar col-
lector as a function of time for water and different con-
centrations of hybrid nanofluid (Fig. 4). The heat gain in-
creases in the morning hours as solar radiation intensifies,
reaching a maximum value near noon, and then gradually
decreases in the afternoon. Water shows the lowest heat
gain curve, peaking at around 530 W, while the hybrid
nanofluids exhibit significantly higher values. The 0.15%
hybrid nanofluid achieves the greatest heat gain, reaching
nearly 670 W at midday, reflecting the enhanced thermal
transport properties of the hybrid nanofluid. Increasing
nanoparticle concentration results in improved heat
transfer, reduced thermal resistance, and stronger micro-
convective effects. The upward shift in the hybrid
nanofluid curves compared to water clearly demonstrates
the beneficial impact of nanoparticles on the thermal per-
formance of the collector [15].
Fig. 4. Useful Heat Gain Vs Time
4.3 Instantaneous Thermal Efficiency
Fig. 5 (Efficiency vs. Time) shows that the instantaneous
thermal efficiency of the FPSC increased with increasing na-
noparticle concentration. The graph illustrates the varia-
tion of instantaneous thermal efficiency of the flat plate so-
lar collector throughout the day for water and three con-
centrations of Al₂O₃–Cu hybrid nanofluids. All curves follow
a similar daily trend, with efficiency increasing toward mid-
day due to higher solar radiation and decreasing in the af-
ternoon. Water exhibits the lowest efficiency, while hybrid
nanofluids consistently show higher values across the en-
tire operating period. The 0.15% hybrid nanofluid demon-
strates the highest thermal efficiency, reaching a peak of
approximately 0.74, followed by 0.10% and 0.05% concen-
trations. The enhancement in efficiency with nanoparticle
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Відновлювана енергетика. № 1/2026 | Сонячна енергетика
concentration is attributed to improved thermal conductiv-
ity, enhanced absorption of solar energy, and superior con-
vective heat transfer characteristics of the hybrid
nanofluid. The graph clearly shows that even small addi-
tions of nanoparticles significantly improve heat transfer
performance of the solar collector. The results obtained in
the present work are consistent with earlier findings in the
literature. Studies by [16] and [17] reported 10–18% im-
provements in solar collector efficiency using hybrid
nanofluids. The enhancements observed in this study (12–
20%) confirm that Al₂O₃–Cu hybrid nanofluid is a strong
candidate for improving the performance of FPSCs under
real operating conditions.
Fig. 5. Efficiency vs. Time
4.4 Effect of Nanofluid Thermophysical Properties
The enhanced performance of the flat plate solar collector
when using Al₂O₃–Cu hybrid nanofluid is largely attributed
to the improved thermophysical properties of the working
fluid. The incorporation of nanoparticles significantly in-
creases the thermal conductivity of the base fluid due to
intensified phonon transport, enlarged surface area for en-
ergy exchange, and enhanced molecular interactions
within the liquid [18]. The synergistic combination of metal-
oxide (Al₂O₃) and metallic (Cu) nanoparticles further
strengthens heat transfer performance by promoting more
efficient conduction pathways. Moreover, the random
Brownian motion of nanoparticles contributes to micro-
convection, which boosts thermal diffusivity and acceler-
ates energy transport within the fluid. Although a slight in-
crease in viscosity is observed with higher nanoparticle con-
centrations, it remains within acceptable operating limits
and does not impede fluid flow. Overall, the combined en-
hancements in thermal conductivity, thermal diffusivity,
and convective heat transfer lead to a substantial improve-
ment in the heat absorption and thermal efficiency of the
solar collector [19].
4.5 Stability and Suspension Behaviour
The stability of the Al₂O₃–Cu hybrid nanofluid plays a crucial
role in maintaining consistent thermophysical properties
and ensuring reliable thermal performance in the solar col-
lector. Visual sedimentation tests conducted over a 48-
hour period indicated minimal particle settling,
demonstrating that the hybrid nanofluid possessed good
suspension stability. This stability can be attributed to the
effective ultrasonication process, which broke down ag-
glomerates and promoted uniform dispersion of nanopar-
ticles throughout the base fluid. Additionally, the presence
of Al₂O₃ nanoparticles enhances colloidal stability by reduc-
ing the tendency of the higher-density Cu nanoparticles to
sediment, creating a synergistic effect that improves over-
all suspension behavior. The absence of significant sedi-
mentation ensures uniform heat transfer characteristics
throughout the experimental duration, preventing local
thermal resistance or fouling inside the riser tubes. Thus,
the stable dispersion of nanoparticles confirms the suitabil-
ity of Al₂O₃–Cu hybrid nanofluid as a reliable working fluid
in solar thermal applications [20].
Conclusion
The present experimental investigation provides field-scale
validation of Al₂O₃–Cu hybrid nanofluids in a flat plate solar
collector under real outdoor solar irradiation conditions, ra-
ther than in simulated or constant laboratory heat flux en-
vironments commonly reported in previous studies. The
novelty of this work lies primarily in the acquisition of per-
formance data under naturally fluctuating solar intensity,
ambient temperature, and wind conditions, thereby cap-
turing realistic diurnal variations that directly influence col-
lector behavior in practical installations. Experiments were
conducted under tropical climatic conditions characterized
by strong and rapidly varying irradiance, enabling assess-
ment of collector response across a wide range of real-time
143
Відновлювана енергетика. № 1/2026 | Сонячна енергетика
solar flux levels. The hybrid nanofluid with 0.3% concentra-
tion consistently demonstrated superior thermal perfor-
mance compared to water across all irradiation ranges,
confirming its robustness under dynamic operating condi-
tions. The observed 45–60% enhancement in thermal effi-
ciency was achieved under non-steady irradiation, provid-
ing practical validation beyond idealized steady-state test-
ing. An additional contribution of this study is the con-
trolled two-step preparation and dispersion protocol
adopted for the hybrid nanofluid, ensuring homogeneous
particle distribution and minimizing agglomeration. Stabil-
ity was experimentally verified for 48 hours under ambient
exposure conditions, offering documented short-term op-
erational reliability under field conditions. While long-term
stability remains a subject for future investigation, the pre-
sent work establishes a validated baseline for practical out-
door deployment. Furthermore, the study reports an ex-
tended set of experimentally monitored parameters, in-
cluding instantaneous efficiency, useful heat gain, outlet
temperature variation, and performance response to real-
time solar flux, thereby generating a comprehensive da-
taset under actual environmental conditions. Such detailed
field-level performance characterization of Al₂O₃–Cu hybrid
nanofluids in flat plate collectors remains limited in the ex-
isting literature. In summary, the contribution of this work
is not merely the confirmation of previously reported en-
hancement mechanisms, but the experimental verification
of hybrid nanofluid performance under realistic, region-
specific, and strongly fluctuating solar irradiation condi-
tions, providing new empirical data relevant for practical
solar thermal system implementation. Future research
should focus on long-term stability assessment, seasonal
performance evaluation, and large-scale operational test-
ing to facilitate commercial adoption in renewable energy
systems.
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|
| id | veorgua-article-601 |
| institution | Vidnovluvana energetika |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-19T01:18:40Z |
| publishDate | 2026 |
| publisher | Institute of Renewable Energy National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | veorgua/74/cdd65f852e9e971da4ae8be4a6076a74.pdf |
| spelling | veorgua-article-6012026-07-18T06:32:24Z PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ПЛАСКОГО СОНЯЧНОГО КОЛЕКТОРА ЗА РАХУНОК ВИКОРИСТАННЯ ГІБРИДНИХ НАНОРІДИН AL₂O₃–CU Sekharraj , K. Balu, P. Srilaxmi , Dasari Nimmala , Harathi Ravi , S. Ivanchuk , V. This study examines the thermal performance enhancement of a flat plate solar collector (FPSC) using Al₂O₃–Cu hybrid nanofluids as the working fluid. Hybrid nanofluids, formulated by combining metal-oxide and metallic nanoparticles, offer superior thermophysical properties compared to conventional fluids. In this work, Al₂O₃ and Cu nanoparticles were dispersed in distilled water at low volume concentrations (0.05–0.15%) using ultrasonication, and their thermal conductivity, viscosity, and stability were characterized. Experiments were conducted under real-time solar radiation to evaluate useful heat gain and instantaneous thermal efficiency of the FPSC. Results show that hybrid nanofluids significantly enhance heat transfer, with thermal conductivity increasing by up to 22% compared to water. The collector’s useful heat gain improved by 18–28%, and the instantaneous efficiency increased by 12–20% depending on nanoparticle concentration. These improvements are attributed to enhanced thermal conductivity, intensified convective heat transfer, and synergistic effects between the nanoparticles. The findings demonstrate that Al₂O₃–Cu hybrid nanofluids are promising next-generation heat transfer fluids for high-performance solar thermal systems. У цій роботі досліджено підвищення теплової ефективності плоского сонячного колектора (FPSC) за рахунок використання гібридних нанорідин Al₂O₃–Cu як робочого теплоносія. Гібридні нанорідини, отримані шляхом поєднання наночастинок оксидів металів і металевих наночастинок, мають кращі термофізичні властивості порівняно з традиційними теплоносіями. У цій роботі наночастинки Al₂O₃ та Cu диспергували у дистильованій воді при низьких об’ємних концентраціях (0,05–0,15%) із застосуванням ультразвукової обробки, після чого було визначено їхню теплопровідність, в’язкість і стабільність. Експерименти проводили в умовах реального сонячного випромінювання з метою оцінювання корисного теплового надходження та миттєвої теплової ефективності плоского сонячного колектора. Результати дослідження доводять, що використання гібридних нанорідин суттєво підвищує інтенсивність теплопередачі: теплопровідність зросла до 22% у порівнянні з водою. Корисне теплове надходження колектора збільшилося на 18–28%, а миттєвий коефіцієнт корисної дії зріс на 12–20% залежно від концентрації наночастинок. Зазначене покращення ефективності пояснюється підвищенням теплопровідності, інтенсифікацією конвективного теплообміну та синергетичним ефектом взаємодії наночастинок. Отримані результати свідчать, що гібридні нанорідини Al₂O₃–Cu є перспективними теплоносіями нового покоління для використання у високоефективних сонячних теплових установках. Institute of Renewable Energy National Academy of Sciences of Ukraine 2026-03-28 Article Article application/pdf https://ve.org.ua/index.php/journal/article/view/601 10.36296/1819-8058.2026.1(84).137-144 Vidnovluvana energetika ; No. 1(84) (2026): Scientific and applied Journal renewable energy ; 137-144 Возобновляемая энергетика; ##issue.no## 1(84) (2026): Scientific and applied Journal renewable energy ; 137-144 Відновлювана енергетика; № 1(84) (2026): Науково-прикладний журнал Відновлювана енергетика; 137-144 2664-8172 1819-8058 10.36296/1819-8058.2026.1(84) en https://ve.org.ua/index.php/journal/article/view/601/512 Copyright (c) 2026 K. Sekharraj , P. Balu, Dasari Srilaxmi , Harathi Nimmala , S. Ravi , V. Ivanchuk https://creativecommons.org/licenses/by-nc-nd/4.0 |
| spellingShingle | Sekharraj , K. Balu, P. Srilaxmi , Dasari Nimmala , Harathi Ravi , S. Ivanchuk , V. PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS |
| title | PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS |
| title_alt | ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ПЛАСКОГО СОНЯЧНОГО КОЛЕКТОРА ЗА РАХУНОК ВИКОРИСТАННЯ ГІБРИДНИХ НАНОРІДИН AL₂O₃–CU |
| title_full | PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS |
| title_fullStr | PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS |
| title_full_unstemmed | PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS |
| title_short | PERFORMANCE ENHANCEMENT OF A FLAT PLATE SOLAR COLLECTOR USING AL₂O₃–CU HYBRID NANOFLUIDS |
| title_sort | performance enhancement of a flat plate solar collector using al₂o₃–cu hybrid nanofluids |
| url | https://ve.org.ua/index.php/journal/article/view/601 |
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