Numerical investigation of modified conical cavity receiver with different heat transfer fluids

ABSTRACT

The parabolic dish system is viable for meeting high-temperature requirements by harnessing solar energy. The receiver has a significant impact on the thermal efficiency of the solar parabolic dish system. Historically, the cavity receiver (CR) has been preferred over other receivers due to its reduced heat loss. Over the past two decades, numerous CR geometries have been developed in an effort to further improve thermal performance. The influence of several heat transfer fluids, including water, thermal oil, thermal oil/Al2O3 nanofluid, and thermal oil/MWCNT nanofluid, was investigated in this research using a three-dimensional numerical simulation on a modified conical cavity receiver (MCCR). Heat transfer fluids are considered to flow through copper tubes in a MCCR. The temperature contours, the inlet and outlet temperatures were numerically predicted. The experimental results were used to validate the numerical conclusions for the outlet temperature of the heat transfer fluid (water). According to the numerical results, Al2O3/thermal oil nanofluid attained the maximum exit temperatures (83.8°C to 95.1°C) and exergy efficiency (7.68%). The average thermal efficiency of systems with working fluids MWCNT/Thermal oil, Thermal oil, and Al2O3/Thermal oil was found to be 15.3%, 21.8%, and 28.2% greater than water, respectively. For the given solar radiation, the thermal oil/Al2O3 nanofluid achieved the highest average thermal efficiency of 59%. Whereas the average thermal efficiency of thermal oil and thermal oil/MWCNT was found to be 56%, and 53%, respectively. In addition, a correlation for the Nusselt number was developed in terms of the Prandtl number and the Reynolds number.

KEYWORDS:

• Parabolic dish
• cavity receiver
• modified conical
• CSP
• SPDC
• heat transfer fluid

Nomenclature

k	=	thermal conductivity (W/mK)
T	=	Temperature (K)
Cp	=	constant pressure specific heat capacity (kJ/kgK)
h	=	convection heat transfer factor (W/m2K)
Q	=	heat transfer per unit area (W/m2)
A	=	area (m2)
Ib	=	direct beam radiation (W/m2)
Cg	=	geometric concentration ratio
$\dot{m}$	=	rate of mass flow (kg/s)
As	=	Area of surface (m2)
t	=	time (s)
Ts	=	Temperature at surface (K)
v	=	velocity (m/s)
p	=	pressure (Pa)
u	=	velocity (m/s) (vector)
Greek symbols	=
ρ	=	density (kg/m3)
ε	=	emissivity
ϕp	=	volume fraction of nanoparticle
η	=	efficiency
σ	=	Stefan-Boltzmann number (5.67 × 10−8 W/m2K4)
τ	=	viscous stress (Pa) (tensor)
q	=	heat flux (W/m2) (vector)
S	=	strain rate (vector)
F	=	volume force (N/m2) (vector)
Subscripts and superscripts	=
f	=	fluid
s	=	solar
c	=	concentrator
r	=	receiver
opt	=	optical
u	=	useful
out	=	outlet fluid
in	=	inlet fluid
rad	=	radiation
conv	=	convection
atm	=	atmosphere
th	=	thermal

Acknowledgements

The authors would like to express their gratitude to the National Institute of Technology Puducherry for their invaluable support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Arjun Singh K

Arjun Singh K is doing PhD in the Solar Energy Laboratory, Department of Mechanical Engineering, National Institute of Technology Puducherry, Karaikal, India. He is working on concentrated solar power for the past two and a half years.

Guna Muthuvairavan

Guna Muthuvairavan is doing PhD in the Solar Energy Laboratory, Department of Mechanical Engineering, National Institute of Technology Puducherry, Karaikal, India. He is working on solar thermal for the past one and a half years

Sendhil Kumar Natarajan

Sendhil Kumar Natarajan is working as an Assistant Professor & Head, Department of Mechanical Engineering, National Institute of Technology Puducherry, Karaikal, India. He has 17 years’ experience of teaching and research. He has expertise in Solar Thermal, Concentrating Photovoltaic, Integration of High-Temperature Solar Thermal and CPV, Heat Transfer and Fluid Flow, Jet Ejectors, Waste Frying Oils, Fuel Cells