Turbulent flow analysis of a flattened tube in- plane curved solar collector using Titanium oxide nanofluid

  • A. SacithraEmail author
  • A. Manivannan


The present study deals with the experimental investigation on the performance of a solar water heater consisting of a flattened tube absorber with a spiral configuration. The analysis is carried out by using water and Titanium oxide nanofluid of 0.1% concentration as the working fluid adopting forced circulation for various flow rates of 0.05 kg/s, 0.066 kg/s, 0.083 kg/s. The effect of mass flow rate on the flatness of the tube and spiral configuration of the absorber is investigated. The outlet fluid temperature, instantaneous efficiency, Reynolds number, Nusselt number, and heat transfer coefficient, friction factor, and Dean number are the parameters considered in this analysis. The results show that there is a significant increase in heat transfer coefficient of 22% for TiO2 (φ = 0.1) nanofluid compared to water. The results indicate that the instantaneous efficiency increases by 7.5% for TiO2 nanofluid. The highest outlet temperature of 67 °C was obtained for a mass flow rate of 0.066 kg/s. The removal energy parameter FRUL increases by 20% and the absorbed energy parameter FR(τα) increases by 5% for TiO2 nanofluid comparing with water. The values of the Nusselt number, friction factor and dean number obtained experimentally are compared with numerical correlation and the deviation is found to be within ±3% to ±8%. The Dean number is calculated for different curvature ratio of κ1 = 0.141, κ2 = 0.070 and κ3 = 0.047.Increase dean number of 18% with increase in curvature ratio is found.


Flattened tube Nanofluid Heat transfer Reynolds number Nusselt number 



Heat transfer surface m2


Collector tilt factor degree


Specific heat of Fluid kJ/kgK


Dean Number dimensionless


Hydraulic Diameter of tube m


Friction factor


Wind Factor W/m2oC


mean-plate temperature factor oC


Incident solar radiation W/m2


Heat transfer coefficient W/m2oC


Convective heat transfer coefficient W/m2oC


Thermal conductivity W/mK


Thermal conductivity of insulation W/mK


Length of the absorber tube m

\( \dot{\mathrm{m}} \)

Mass flow rate of water kg


Number of glazing


Nusselt number Dimensionless


Pressure drop kPa


Prandtl number Dimensionless


Useful heat gain W


Reynolds number Dimensionless


Radius of curvature m


Ambient temperature °C


Fluid inlet temperature °C


Fluid Outlet temperature °C


Mean absorber plate temperature °C


Loss coefficient W/m2oC


Thickness of insulation m

Greek symbols


Dynamic viscosity Ns/m2


Tilt angle degree


Thickness of absorber plate m


Density kg/m2


Nanoparticles volume concentration %


Collector efficiency %


Transmittance-absorptance product


Emittance of plate


Emittance of glass cover


Stefan-Boltzmann constant - 5.67*108 W/m2K4



Base fluid




Compliance with ethical standards

Conflict of interest

On behalf of all authors, the corresponding author states that there is no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringRegional Campus of Anna UniversityTirunelveliIndia

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