Parametric optimization of a stamped longitudinal vortex generator inside a circular tube of a solar water heater at low Reynolds numbers

Author(s)

Silva, Felipe A. S. ^[1] ; Junior, Luis ^[1] ; Silva, Jose ^[1] ; Kambampati, Sandilya ^[2] ; Salviano, Leandro ^[1]

Affiliation

^[1] Sao Paulo State Univ, Sao Paulo - Brazil

^[2] Univ Calif San Diego, San Diego, CA 92103 - USA

• Document type: Journal article
• Source: SN APPLIED SCIENCES; v. 3, n. 8 AUG 2021.
• Web of Science Citations: 0

Abstract

Solar Water Heater (SWH) has low efficiency and the performance of this type of device needs to be improved to provide useful and ecological sources of energy. The passive techniques of augmentation heat transfer are an effective strategy to increase the convective heat transfer coefficient without external equipment. In this way, recent investigations have been done to study the potential applications of different inserts including wire coils, vortex generators, and twisted tapes for several solar thermal applications. However, few researchers have investigated inserts in SWH which is useful in many sectors where the working fluid operates at moderate temperatures. The longitudinal vortex generators (LVG) have been applied to promote heat transfer enhancement with a low/moderate pressure drop penalty. Therefore, the present work investigated optimal geometric parameters of LVG to enhance the heat transfer for a SWH at low Reynolds number and laminar flow, using a 3D periodical numerical simulation based on the Finite Volume Method coupled to the Genetic Algorithm optimization method (NSGA-II). The LVG was stamped over a flat plate inserted inside a smooth tube operating under a typical residential application corresponding to Reynolds numbers of 300, 600, and 900. The geometric parameters of LGV were submitted to the optimization procedure which can find traditional LVG such as rectangular-winglet and delta-winglet or a mix of them. The results showed that the application of LGVs to enhance heat transfer is an effective passive technique. The different optimal shapes of the LVG for all Reynolds numbers evaluated improved more than 50% of heat transfer. The highest augmentation heat transfer of 62% is found for the Reynolds number 900. However, the best thermo-hydraulic efficiency value is found for the Reynolds number of 600 in which the heat transfer intensification represents 55% of the pressure drop penalty. (AU)

• FAPESP's process: 17/00608-0 - Longitudinal vortex generators applied to enhancement of heat transfer on flat-plate solar collector
• Grantee: Felipe Augusto Santos da Silva
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 16/14620-9 - Enhancement of heat transfer on flat-plate solar collector applied to water heating with active recirculation system by passive technique
• Grantee: Leandro Oliveira Salviano
• Support Opportunities: Regular Research Grants