Employing a novel crimped-spiral rib inside a triple-tube heat exchanger working with a nanofluid for solar thermal applications: Irreversibility characteristics

This research attempts to study the performance of employing an innovative crimped-spiral rib within a triple pipe heat exchanger (TPHE) operated with an alumina-water nanofluid regarding the second law viewpoint. The numerical analyses are carried out using the two-phase mixture model, and turbulence modeling is done via the Reynolds Stress Model (RSM). The parameters consist of the rib height ratio (0.23, 0.38, and 0.53), crimped intensity (2, 4, 6), rib pitch ratio (0.1, 0.2, and 0.3), and the nanofluid volume fraction (1, 2, and 3%). The nanofluid is the hot fluid flowing inside the intermediate tube, while the two other fluids are water. This paper underlines the lowest energy degradation to design a more efficient TPHE. The outcomes indicate that the idea of utilizing crimped-spiral rib is effective such that the nanofluid's thermal entropy generation reduces about 22.92% using rib with higher crimped intensity because of the stronger swirl stream. The total entropy generation and total exergy destruction decline by the volume fraction increment, rib pitch ratio decrement, and by an increment in either crimped intensity or rib height ratio. The second law efficiency is found to be high for all the cases such that it is greater than 0.6.