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This paper presents a numerical investigation on a heat transfer enhancement by using a computational fluid dynamics software. The heat transfer enhancement is implemented by inserting twisted tape into a heat exchanger tube. The twisted tapes with twist ratios of 4, 6 and 8 were modified with alternate axis. The pitch of the twisted tape having the rotation direction such as clockwise and counterclockwise are connected with 90º connection angle. Water is selected as working fluid and turbulent flow condition corresponding to Reynolds number ranging from 5000 to 29000 are considered in the study. The heat exchanger tube is under constant heat flux of 50 kW/m2. Numerical analysis results prove that the use of twisted tape improves thermal performance compared to smooth tube. As the twist ratio increased, the heat transfer performance and the friction loss penalty decreased. Overall results are determined with thermohydraulic performance criteria (THP). The highest THP value is obtained as 1.21 for the tube inserted with the twisted tape which has the twist ratio of 4 and alternate axis between the twist pitches at Reynolds number of 5913

Natural fibres are highly desirable in composites as they are renewable, biodegradable, and cost-effective. They are also abundant in nature with many different types available all over the world. However, despite their advantages, key challenges such as poor fibre-matrix interfacial bonding and moisture absorption limit their widespread adoption in more sophisticated applications. This article provides an overview of natural fibres, including classifications, types, properties, advantages, and disadvantages, with a subsequent review of recent studies, focusing on fibre-matrix selection, treatment methods, and characterization to better understand the current situation. It is apparent from these studies that water absorption is a significant challenge due to the inherent hydrophilic nature of natural fibres as even after treatments like mercerization and silane were applied, substantial amounts of absorption were observed. The effects of powder fillers also vary, with beneficial effects up to a certain proportion, beyond which they became detrimental.