Impact of Titanium Oxide-Based (TiO₂) Nanofluid on Parabolic Trough Solar Concentrating Collector

Abstract

Parabolic trough solar concentrating collector (PTSC) system is proficient in all solar applications such as power generation, steam, water heating, and air heating. This work was conceded for the study of nanofluids which are nascent fluid that has given away the growth in the thermal properties over the past decade. Nanofluids have made great potential in the field of nanotechnology for thermal engineers. The present work investigates the effects of variation of titanium oxide nanoparticles concentration on the efficiency of a nanofluid-based parabolic trough solar concentrating collector with the usage of high-reflective mirror trough. Nanofluids blend primarily the base fluid (water, in this study) with the nanoparticles of the size micro or millimeter and display characteristic features than that of conservative fluids employed. At 110 lph mass flow rate, the percentage change in overall thermal efficiency was found to be increasing with increase in concentration of nanoparticle, i.e., 42.5% at 0.01% of TiO₂, 59.17% at 0.1% of TiO₂, and 62.28% at 0.15% of TiO₂ in comparison to the water. On the other hand, with an increase in mass flow rate (i.e., 160 lph), the percentage variation in overall thermal efficiency was found to be 26.47%, 41.06%, and 66.37% at 0.01%, 0.1%, and 0.15% of TiO₂ nanoparticles, respectively, when it is compared to the water being used as working fluid. The study indicated that the overall performance of the PTSC improves with an enhancement of mass flow rate and nanoparticle concentration.

Appendix A

Calculations of thermophysical properties and performance evaluation parameters of solar collector: To study the properties of nanofluid and performance of nanofluid using parabolic trough solar collector, following relations are used:

Thermal conductivity: Chandrasekar et al. [18] expressed thermal conductivity as follows:

$$\frac{{K_{nf} }}{{K_{dw} }} = \left[ {\frac{{Q_{nf} }}{{Q_{dw} }}} \right]^{1.358} \left[ {\frac{{C_{pnf} }}{{C_{pdw} }}} \right]^{ - 0.023} \left[ {\frac{{\mu_{dw} }}{{\mu_{nf} }}} \right]^{0.126}$$

(2)

Viscosity: Viscosity of nanofluid is calculated by involving the following equation [19]:

$$\mu_{nf} = \frac{{\mu_{dw} }}{{(1 - \varphi_{p} )^{2.5} }}$$

(3)

Density: It is also calculated by relating the following equation [19]:

$$\rho_{nf} = \left( {1 - \varphi_{p} } \right)\rho_{dw} + \varphi_{p} \rho_{p}$$

(4)

Specific heat: Specific heat also calculated by relating the following equation [19]:

$$C_{eff} = \left[ {\left( {1 - p} \right)_{f} C_{f\;eff} } \right]$$

(5)

Useful heat gain: It is calculated under steady-state condition from the following relation:

$$Q_{u} = {}_{eff}C_{eff} \left( {T_{0} - T_{i} } \right)$$

(6)

Thermal efficiency: The hourly efficiency of the PTSC under steady-state conditions can be obtained from following equation:

$$\eta_{th} = \frac{{m_{eff} c_{pnf} \left( {T_{o} - T_{i} } \right)}}{{A_{{{\text{aper}}}} G_{B} }}$$

(7)

Overall thermal efficiency: The overall thermal efficiency under the steady-state conditions is calculated as:

$$\eta = F_{R} \left( {\tau \alpha } \right) - F_{R} U_{L} \left( {\frac{{T_{i} - T_{a} }}{{G_{B} }}} \right)$$

(8)