The present review paper aims to document the latest developments on the applications of nanofluids as working fluid in parabolic trough collectors (PTCs). The influence of many factors such as nanoparticles and base fluid type as well as volume fraction and size of nanoparticles on the performance of PTCs has been investigated. The reviewed studies were mainly categorized into three different types of experimental, modeling (semi-analytical), and computational fluid dynamics (CFD). The main focus was to evaluate the effect of nanofluids on thermal efficiency, entropy generation, heat transfer coefficient enhancement, as well as pressure drop in PTCs. It was revealed that nanofluids not only enhance (in most of the cases) the thermal efficiency, convection heat transfer coefficient, and exergy efficiency of the system but also can decrease the entropy generation of the system. The only drawback in application of nanofluids in PTCs was found to be pressure drop increase that can be controlled by optimization in nanoparticles volume fraction and mass flow rate.

Application of Nanofluids in Thermal Performance Enhancement of Parabolic Trough Solar Collector: State-of-the-Art

Recent advancement in the natural fiber polymer composites: A comprehensive review

Solar energy is a clean, abundant and easily accessible form of renewable energy. Its intermittent and dynamic nature makes thermal energy storage (TES) systems highly valuable for many applications. Latent heat storage (LHS) using phase change materials (PCMs) is particularly well suited for solar domestic hot water (SDHW) applications as it offers high storage density and heat transfer at near-constant temperature. This article reviews TES technologies for solar water heating systems with a particular focus on techniques for integrating PCM into these systems. These techniques include integrated PCM storage vessels, integrated PCM solar collectors, and integrated a PCM unit inside the solar hot water circuit. It is found that the integrated PCM storage vessel is the most widely applied technique in SDHW systems using PCMs. The latent heat storage unit configuration and heat transfer mechanisms are further reviewed. Furthermore, this review presents recent findings on the performance comparison between conventional SDHW systems and SDHW systems containing PCMs and the long term performance of SDHW system using PCMs are discussed. This review highlights the need for further research in several areas including performance evaluation of different integration techniques, numerical model for system optimization, and long-term performance of solar domestic hot water systems featuring PCMs.

Solar domestic hot water systems using latent heat energy storage medium: A review

Increasing energy demand calls for the implementation of proper thermal energy storage which is one of the most important components of solar energy conversion systems. Phase change material based latent heat energy storage systems have emerged as a promising option to effectively store thermal energy. Generally, paraffin wax is used as the most common phase change material for low to medium temperature storage applications because it has a large latent heat and low cost besides being stable, nontoxic and non-corrosive. The performance of paraffin wax based latent heat energy storage systems (LHESS) is limited by its poor thermal conductivity. In this paper, the previous experimental and theoretical research studies on LHESS using paraffin wax as phase change material with different performance enhancement techniques are reviewed. Further, research works related to dispersing different kind of nanoparticles in paraffin wax for the enhancement of its thermal conductivity are comprehensively reviewed with respect to synthesis, characterization and thermophysical properties of the nanoenhanced phase change material.

A review on thermal conductivity enhancement of paraffinwax as latent heat energy storage material

The increasing global environmental concerns and awareness of renewable green resources is continuously expanding the demand for eco-friendly, sustainable and biodegradable natural fibre reinforced composites (NFRCs). Natural fibres already occupy an important place in the composite industry due to their excellent physicochemical and mechanical properties. Natural fibres are biodegradable, biocompatible, eco-friendly and created from renewable resources. Therefore, they are extensively used in place of expensive and non-renewable synthetic fibres, such as glass fibre, carbon fibre and aramid fibre, in many applications. Additionally, the NFRCs are used in automobile, aerospace, personal protective clothing, sports and medical industries as alternatives to the petroleum-based materials. To that end, in the last few decades numerous studies have been carried out on the natural fibre reinforced composites to address the problems associated with the reinforcement fibres, polymer matrix materials and composite fabrication techniques in particular. There are still some drawbacks to the natural fibre reinforced composites (NFRCs)—for example, poor interfacial adhesion between the fibre and the polymer matrix, and poor mechanical properties of the NFRCs due to the hydrophilic nature of the natural fibres. An up-to-date holistic review facilitates a clear understanding of the behaviour of the composites along with the constituent materials. This article intends to review the research carried out on the natural fibre reinforced composites over the last few decades. Furthermore, up-to-date encyclopaedic information about the properties of the NFRCs, major challenges and potential measures to overcome those challenges along with their prospective applications have been exclusively illustrated in this review work. Natural fibres are created from plant, animal and mineral-based sources. The plant-based cellulosic natural fibres are more economical than those of the animal-based fibres. Besides, these pose no health issues, unlike mineral-based fibres. Hence, in this review, the NFRCs fabricated with the plant-based cellulosic fibres are the main focus.

https://www.mdpi.com/2079-6412/10/10/973/pdf

Plant-Based Natural Fibre Reinforced Composites: A Review on Fabrication, Properties and Applications

Usage of composites with natural fiber reinforcement is drastically increasing in recent times because of their low density, biodegradable nature, and low cost. However, natural fibers have certain...

Mechanical, morphological, and thermogravimetric analysis of alkali-treated Cordia-Dichotoma natural fiber composites

Nowadays, research attention on composite materials accentuates where not only was their unique attributes agglomerated-alleviated weight and density, elevated impact and specific strengths, but al...

Impact of Alkali Treatment on Characterization of Tapsi (Sterculia Urens) Natural Bark Fiber Reinforced Polymer Composites

Abundantly available solar energy utilization for domestic and industrial applications is hindered because of its intermittent nature. The thermal energy storage (TES) system using both sensible and latent heat has many advan- tages like large heat storage capacity in a unit volume and its isothermal behavior during the charging and discharging processes. Because of these advantages, in recent years, a lot of research work has been going on to overcome problems like low heat transfer the rates between heat transfer fluid and phase change material (PCM) in both charging and discharging processes of the PCM-based TES system. In the present experimental investigation results of a combined sensible and latent heat TES system integrated with a varying (solar) heat source is presented. Investigations are carried out in the TES system for different phase change materials (paraffin and Stearic acid) by varying HTF flow rates and for various sizes of spherical capsules (68, 58, and 38 mm in diameter). Experiments are performed in both charging and discharging processes. The results show that the 38 mm diameter spherical capsule shows better performance compared to spherical capsules of other sizes.

Experimental Studies on Phase Change Material-Based Thermal Energy Storage System for Solar Water Heating Applications

The effect of granite powder on mechanical, structural and water absorption characteristics of alkali treated cordia dichotoma fiber reinforced polyester composite

The possible usage of natural fiber reinforced composites (NFC) for various industrial applications is being explored. In the present work, mechanical and wear behavior of three different NFCs were...

R. Meenakshi Reddy

Papers

Mechanical, morphological, and thermogravimetric analysis of alkali-treated Cordia-Dichotoma natural fiber composites

Impact of Alkali Treatment on Characterization of Tapsi (Sterculia Urens) Natural Bark Fiber Reinforced Polymer Composites

Experimental Studies on Phase Change Material-Based Thermal Energy Storage System for Solar Water Heating Applications

The effect of granite powder on mechanical, structural and water absorption characteristics of alkali treated cordia dichotoma fiber reinforced polyester composite

Evaluation of Mechanical and Wear Performances of Natural Fiber Reinforced Epoxy Composites