THERMAL PERFORMANCE IMPROVEMENT OF FLAT … · Nano fluid is the fluid with solid-liquid mix or suspensions formed by dissolving minute metallic or nonmetallic Nano particles in base

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 7, July 2017, pp. 627–635, Article ID: IJMET_08_07_070

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

THERMAL PERFORMANCE IMPROVEMENT

OF FLAT PLATE SOLAR COLLECTOR USING

NANO FLUIDS

Malleboyena Mastanaiah

Research Scholar, Department of Mechanical Engineering,

JNTUA, Anantapuramu, A.P, India

Prof. K. Hemachandra Reddy

Professor, Department of Mechanical Engineering,

JNTUCEA, Anantapuramu, A.P, India

Dr. V. Krishna Reddy

Professor, Department of Mechanical Engineering,

KITS, Markapur, A.P, India

ABSTRACT

Extracting thermal energy from solar flat plate collectors is the simplest way than

others. Collector performance depends upon the absorber material, radiation

intensity, tracking system, working fluid characteristics etc. Properties of working

substance plays a vital role that effects the collector efficiency and overall

performance. An attempt has been made to utilize nano fluid as working substance in

this work to increase the heat transfer from absorber to working fluid. These fluids

contains metallic and non-metallic particles like CuO, Aluminum, aluminum oxides

having higher thermal conductivity than water. The outlet temperatures, Thermal and

collector efficiencies for different nano fluid flow rates against time and reduced

temperature parameter were studied. Effect of nano particle Concentrations with base

fluid was also examined and found increase in efficiency of the solar system to certain

limit and supplementing the nano particles beyond the limit does not increase the

efficiency.

Key words: Nano fluid, Thermal conductivity, Copper oxide, Collector efficiency.

Cite this Article: Malleboyena Mastanaiah, Prof. K. Hemachandra Reddy and

Dr. V. Krishna Reddy. Thermal Performance Improvement of Flat Plate Solar Collector

using Nano Fluids. International Journal of Mechanical Engineering and Technology,

8(7), 2017, pp. 627–635.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

Thermal Performance Improvement of Flat Plate Solar Collector using Nano Fluids


1. INTRODUCTION

Many encouraging facts on solar energy, solar systems play a vital role in converting solar

energy into heat or electrical energy. Solar thermal applications improved heat transfer

techniques leads to better performance of the system. Among many possible heat transfer

improvement techniques, usage of Nano fluids as working fluids is also an effective approach.

Many works related to nano fluids usage in solar collector systems are in progress in the areas

of water heaters, cooling systems, solar cells, solar stills, absorption refrigeration systems etc.

Solar collectors in collecting thermal energy considered legendary based on the

characteristics of heat transfer fluid and their construction Solar flat plate collectors are

generally in water heating applications and the efficiencies are in the range of 65 - 70% which

are very high than direct energy conversion systems having 15-17% efficiency.

Nano fluid is the fluid with solid-liquid mix or suspensions formed by dissolving minute

metallic or nonmetallic Nano particles in base fluids. Nano particles size (generally less than

100nm) gives them the ability to intermingle with base liquids at the molecular level. The

metallic or nonmetallic Nano particles could cause the changes in heat transfer and transport

properties of the base fluid. These fluids are the new generation heat transfer fluids for

diversified applications in industrial and automotive industries as these are having excellent

thermal performance. Higher thermal conductivity & radiative characteristics of Nano

particles caused to be Nano fluids as promising working fluids in solar collector system [9].

2. LITERATURE

Y. Tian et al.[1] made a comprehensive review on different solar collectors and available

thermal energy storage techniques. In their review they have considered different studies of

collector design criteria and different materials which can store sensible, latent and chemical

energies. Number of heat transfer enhancement possibilities are discussed by incorporating

more thermal conductive materials and cascading techniques. Solar flat plate collector

performance was analyzed by P.W.Ingle et al. [2] using CFD by simulating the collector with

respect to different operating parameters. Unstructured grid using ICEM is adopted for better

analysis. Small deviations are observed from simulated results to measured values and this

may be due to the imperfectness during experimentation

Titan C Paul et al[3] have utilized the advantage of usage of ionic liquids in solar thermal

collectors and made several experiments to find the thermo physical properties of ionic liquids

under different temperatures. The changes in ionic liquid properties such as viscosity, heat

capacity, density and thermal conductivities are well studied and its suitability to use as

working substances in solar applications. Several works on performance assessment of solar

thermal collectors using Nano fluids as working fluids were reviewed by Navid Bozorgan et

al [4] .Comprehensive information on the usage of Nano fluids as the effective heat transfer

fluids, was given by authors. Shailja Kandwal [5] worked on parabolic collector with nano

fluid (water with Cuo) & Cuo-glycol based fluids and also with ethylene glycol and water.

Efficiencies with all four fluids were compared under various concentrations & mass flow

rates. Water with Cuo substance produces maximum efficiency among four working fluids

and the results are also validated by CFD model results and found good agreement between

two results. Different heat transfer fluids (HTFs) used in solar thermal applications was

exploited by Umish Srivastva et al. [7]They made a review on the works used various HTFs

for low, medium and high temperature applications. They concluded hydrocarbon oils be the

promising fluid for majority high temperature applications among others and molten salts and

metals are also have their significance in particular applications.

Xie et al. [8] investigated on the alumina suspension thermal conductivity for different

base fluids. Effect of thermal conductivity with volume fraction by both experimental and

Malleboyena Mastanaiah, Prof. K. Hemachandra Reddy and Dr. V. Krishna Reddy


theoretical studies. Bharot vishal kumar G et al [6] exploited the usage of nano fluids as

working fluid in solar parabolic tube collectors instead of water. They observed the exhibition

of good thermal properties by both metallic and non-metallic nano materials and by using

these substances, collector performance was improved. Authors worked with Copper oxide

and Aluminium oxide and observed improvement in instantaneous efficiency of collector.

This paper is aimed to study the improvement in heat transfer, collector efficiency by

using CuO +water with different concentrations and flow rates on a solar flat plate collector.

3. METHODOLOGY

Solar flat plate collector performance is estimate by using Nano fluid (Cu O+ Water) as

working fluid with different concentrations of 0.01%, 0.05% and 0.1% for different flow rates

0.028, 0.036 and 0.045 Kg/sec. Solar collector outlet temperatures, thermal efficiency and

instantaneous efficiencies are estimated and simulation studies are also done for the collector

under same conditions. Tests were conducted for different solar intensities and obtained

results from experiments and simulation studies are also compared.

4. RESULTS & DISCUSSIONS

The results were noted by running the CuO + water as working fluid with different flow rates

and different CuO concentrations on May 21st of 2016 from morning 9:30 AM to 2:30 PM.

The following graphs shows the thermal and instantaneous efficiencies under different

conditions.

The following figures 1, 2 and 3 illustrate the increase in working fluid temperature with

solar flux and fluid flow rate. The test was conducted for the flow rates of 0.028, 0.036 and

0.045 kg/sec from morning 9:30 AM to 2:30 PM. It was observed that solar intensity

increases up to afternoon 1:00 PM and decreases later on. In the morning the percentage of

increase in solar intensity is more than in afternoon. The same conditions are simulated

through CFD and found very good coincidence with smaller deviation percentages of the

order 5-9%. Higher outlet temperatures were notice with simulation results than experimental

one due to higher convection losses in actual conditions. The maximum amount of solar flux

observed in figure 1, 2 and 3 was noticed to be 875.05, 886.27 and 862.97 W/m2 respectively.

Figure 4.1 Variation in solar intensity and temperature

with time for Cuo-H2O based Nanofluid (0.01%

concentration) at volume flow rate of 0.028 kg/sec

Figure 4.2 Variation in solar intensity and temperature

with time for Cuo-H2O based Nanofluid (0.01%




The figures 4, 5 and 6 demonstrates the change of Nano fluid temperature with increase in

flow rate and solar intensity. Experiments and simulations through CFD were done for the

flow rates of 0.028, 0.036 and 0.045 kg/sec from morning 9:30 AM to 2:30PM for 0.05 %

Nano fluid concentration. Similar trends were observed as in the previous case i.e. for 0.01 %

concentration, solar intensity rises from 9:30 am to 12:30 pm and subsequently it goes on

declining. It was observed that in the morning, the percentage of increase in solar intensity is

more than in afternoon. Maximum temperatures obtained with increase in Nano particle

concentration and the same was validated with simulated results.

Fig. 5 & 6 shows the effect of flow rate for the same above conditions as in Fig.4 and

observed the outlet temperature increase with increase in fluid flow rate. Simulated results

also showed similar trends and higher values than experimental values of the order 5-9%,

because of more convectional losses in experiments.

Figure 4.5 Variation in solar intensity and temperature with time for Cuo-H2O based Nanofluid (0.05%


Figure 4.6. Variation in solar intensity and temperature with time for Cuo-H2O based Nanofluid

(0.05% concentration) at volume flow rate of 0.045 kg/sec

Figure 4.3 Variation in solar intensity and

temperature with time for Cuo-H2O based

Nanofluid (0.01% concentration) at volume flow

rate of 0.045 kg/sec







The figures 4.7, 4.8 and 9 illustrate the increase in working fluid temperature with solar

flux and fluid flow rate. The test was conducted for the flow rates of 0.028, 0.036 and 0.045

kg/sec from morning 9:30 AM to 2:30 PM. It was observed that solar intensity increases up to

afternoon 1:00 PM and decreases later on. In the morning the percentage of increase in solar

intensity is more than in afternoon. The same conditions are simulated through CFD and

found very good coincidence with smaller deviation percentages of the order 6-10 %. Higher

outlet temperatures were notice with simulation results than experimental one due to higher

convection losses in actual conditions.









Figure 4.9 Variation in solar intensity and temperature with time for Cuo-H2O based Nanofluid

Figure 4.10 Heat flux Vs Water outlet temperature at

different flow rates



Highest temperatures for the flow rates of 0.028 kg/sec, 0.036 kg/sec and 0.045 kg/sec are

observed as 345.2, 346.38 and 347.21K respectively. However slight increase in temperatures

are observed with simulated results because of minimum losses are assumed in model than

experimental results. The maximum amount of solar flux observed in above was noticed to be

864.16, 877.95 and 864.46 W/m2 respectively.

Results obtained from simulation studies with CFD are compared with experimental

values and noticed both results are in good agreement as shown in fig 10. A slight higher

values are observed with model run and it is because of higher convective and conduction

losses with experiments. The below graph illustrates the both results for fluid inlet

temperature of 302.99 K and for flow rates of 0.028 and 0.056 kg/Sec.

The Figures 11-13 illustrates the change in thermal efficiency with reduced temperature

parameter i.e. (Ti-Ta)/IT at different fluid flow rates (0.028, 0.036 and 0.045 kg/sec). Highest

thermal efficiency was noticed at the highest flow rate of 0.045 kg/sec because of maximum

useful gain and minimum convection losses.

The Fig 11 shows the variation in thermal efficiency with reduced temperature by taking

nano fluid as working fluid (0.01% of CuO in base fluid water), for the same flow rate and

other test conditions 0.01% of CuO +Water showing higher efficiency than water, it is

because of higher thermal conductivity and specific heat of CuO that enhances the heat

absorption hence thermal efficiency.

The increase in maximum and minimum collecting efficiency with CuO +Water is 12.4%

and 6.6% respectively. It is also observed that with increase in flow rate of nano fluids in

tubes also increases the outlet temperatures of the fluid and thermal efficiency also increases.

Thermal efficiency variation for 0.05% concentration of CuO+H2O also shows the similar

trend as in 0.01% concentration that the efficiency of solar flat plate collector increases with

mass flow rate and decreases with the increase in reduced temperature at any particular solar

irradiation. The highest thermal efficiency at 0.05% concentration was 7.882, 7.982 and

8.08235 observed at 0.028, 0.036 and 0.045 kg/sec.

With Nano particles size of 20 nm and mass flow rates of 0.028 to 0.045 kg/sec, highest

efficiency was observed for 0.045 kg/sec and thermal efficiency increased with decrease in

reduced temperature as shown in Fig 13. CuO concentration of 0.1% in base fluid shows

maximum collector thermal efficiency when compared with the fluid concentrations of 0.05%

and 0.01%. Fig. 14 shows with increasing concentration, thermal efficiency also increases and

decreases with reduced temperature parameter.

Figure 4.11 Variation in thermal efficiency with (Ti-Ta)/IT

for Cuo-H2O based Nanofluid (0.01% concentration) at

different volume flow rates for 300 collector tilt

Figure 4.12 Variation in thermal efficiency with (Ti-

Ta)/IT for Cuo-H2O based Nanofluid (0.05%

concentration) at different volume flow rates for 300

collector tilt



Variation in instantaneous efficiency with time from morning 8:00 AM to 4:00 PM for

different concentrations of Cuo-H2O based Nano fluid at different flow rates and were

represented in figures 15 to 17. From Fig.15-17 shows the deviation of instantaneous

efficiency for CuO + water at collector optimum inclination (38.130) and different mass flow

rates. Results are drawn for optimum collector tilt as it shows maximum performance. From

the above figures it was experienced that that at a flow rate of 0.045 kg/sec CuO gives highest

instantaneous efficiency.

Figure 4.13 Variation in thermal efficiency with (Ti-

Ta)/IT for Cuo-H2O based Nanofluid (0.1% conc) at

different volume flow rates for 300 collector tilt

Figure 4.14 Variation in Thermal efficiency with (Ti-

Ta)/IT for CuO-H2O based Nanofluid for different

concentrations at volume flow rate of 0.045 kg/sec

Figure 4.15 Variation in instantaneous efficiency with

time for Cuo-H2O based Nanofluid (0.01%

concentration) at different volume flow rates








time for Cuo-H2O based Nanofluid for different

concentrations at volume flow rate of 0.045 kg/sec



Highest performance is observed at 0.1 concentration of CuO Nano fluid. Instantaneous

efficiency of the solar collector at 2:00PM for all the working fluid flow rates and even higher

efficiencies are possible with higher dispersion Nano fluids. Simulation and Experiments

proved that flat plate collector system performance increases with the usage of Nano fluids.

Fig.18 shows with increasing concentration, Instantaneous efficiency also increases with

time in a day from 8:00 AM to 2:00 PM and later on decreases.

5. CONCLUSIONS

Many theoretical and experimental works shows the improvement in solar thermal energy

collection system performance with the usage of Nano fluids as working fluids. This work

was taken up with an objective of improving performance of solar collector system by using CuO-H2O based Nano fluids and experiments were carried out on solar flat plate collector.

Experiments are carried out for different fluid flow rates and for different CuO concentrations in

base fluid H2O. The obtained results are also confirmed with the simulation results of CFD

software. From this work it was noticed that fluid outlet temperatures are continuously

increases with time in a day and percentage of increase increases up to 2:00 PM and later on

decreases. As the concentration of Nano particles increases the heat absorption capacity also

increases hence fluid outlet temperature and system efficiency increases as Nano particles

having higher thermal conductivity. However increase of particle concentration beyond

certain limit does not increase the system efficiency. Highest temperatures for the flow rates

of 0.028 kg/sec, 0.036 kg/sec and 0.045 kg/sec are observed as 345.2, 346.38 and 347.21K

respectively. However slight increase in temperatures are observed with simulated results

because of minimum losses are assumed in model than experimental results.

REFERENCES

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thermal applications” Applied Energy 104 (2013) Pages 538–553.

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flat plate collector” International Journal of Emerging Technology and Advanced

Engineering, Volume 3, Issue 4, April 2013, Pages 337-342, ISSN: 2250-459.

[3] Titan C. Paul et al. “Thermal performance of ionic liquids for solar thermal applications”

Experimental Thermal and Fluid Science 59 (2014), Pages 88–95, 0894-1777

[4] Navid Bozorgan and Maryam Shafahi, “ Performance evaluation of Nano fluids in solar

energy: a review of the recent literature” Micro and Nano Systems Letters “ a springer

open journal” (2015) 3:5, Pages 1-15

[5] Shailja Kandwal, “An experimental investigation into Nano fluids based parabolic solar

collector”Master’s thesis (2015), Department of mechanical engineering, Thapar

University, Patiyala.

[6] Barot Vishalkumar G and K.D Panchal, “ Nano fluid : A Tool to Increase the Efficiency

of Solar Collector” International Journal of Innovations in Engineering and Technology,

Volume 5, Issue 2, April 2015, Pages 350-355, ISSN: 2319-1058

[7] Umish Srivastva1 et al. “Recent Developments in Heat Transfer Fluids Used for Solar

Thermal Energy Applications” Fundamentals of Renewable Energy and Applications,

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[8] Xie. H., Wang. J., Xi. T., Liu. Y., Ai. F. and Wu, Q. (2002). “Thermal conductivity

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[9] Mohsen Sheikholeslami Davood Domairry Ganji, “ A book on Applications of Nano fluid

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THERMAL PERFORMANCE IMPROVEMENT OF FLAT … · Nano fluid is the fluid with solid-liquid mix or suspensions formed by dissolving minute metallic or nonmetallic Nano particles in base