Thermal improvement of linear Fresnel solar system utilizing Al2O3-water nanofluid and multi-way twisted tape

• Published in: International journal of thermal sciences Vol. 176; p. 107505
• Main Authors: Sheikholeslami, M., Ebrahimpour, Z.
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01-06-2022
• Subjects: Linear fresnel reflector (LFR); Multi way twisted tape (MWTT); Nanomaterial; Solar energy; SolTrace; Thermal efficiency; SolTrace; Multi way twisted tape (MWTT); Linear fresnel reflector (LFR); Thermal efficiency; Nanomaterial; Solar energy
• ISSN: 1290-0729; 1778-4166
• DOI: 10.1016/j.ijthermalsci.2022.107505

To enhance the thermal treatment of Linear Fresnel Reflector (LFR) unit, multi-way twisted tape (MWTT) was applied in current research. Twelve mirrors and one tube with trapezoidal cavity around it, generates new LFR unit. The operating fluid is Al2O3-water and for predicting the properties, temperature dependent formulas were employed. Finite volume simulations results in finding the distribution of velocity, temperature, entropy generation. Also, thermal performance was measured. The geometrical factors are number of wings (nw), revolution (TR) and width (ER) of tapes. To evaluate the modeling procedure, various examinations with numerical and experimental publications were verified. To extract the distribution of absorb flux, SolTrace and ANSYS FLUET have been utilized and they are in good agreement. The output of SolTrace demonstrates the path of rays and selecting higher number of rays results in higher accuracy. Highest absorb flux occurs in bottom of pipe. As mixing of fluid improves with rise of revolution and width of tapes, Nu increases and augmentation in interaction of fluid with wall enhances the friction factor. Increasing number of wings can enhance the secondary flow. So, stronger impingement with wall can augment the friction factor. Nu enhances with rise of nw about 4.384% when TR = 2, ER = 0.34,V˙ = 19. Augmenting TR makes Nu to increase about 7.135% when nw = 4, ER = 0.1, V˙ = 19. Besides, with selecting higher ER, friction factor augments about 20.019% at TR = 2, nw = 2, V˙ = 6.3. To evaluate the amount of available work of this solar unit, components of entropy generation (Sgen,f, Sgen,h) have been measured. Thermal irreversibility declines with increase of turbulent intensity while friction component increases. Thermal efficiency (ηth) augments with growth of TR, ER and nw while it decreases with enhance of inlet temperature. As Tin rises, ηthreduces about 31.51% when TR = 2, nw = 2, ER = 0.1, V˙ = 19. Inclusion of nano-powders can enhance the useful heat and ηthaugments about 0.153%.
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•Multi way Twisted tape (TT) has been employed in LFR solar system.•Optical performance of suggested design is 73.5%.•The operating fluid is Al2O3-water and temperature dependent formulation was utilized.•Thermal efficiency augments with growth of twisted ration.•As inlet temperature augments, thermal efficiency decreases about 31.51%.