Nano-coolants for thermal enhancement in heat exchangers: A review of prospects, challenges and applications

Abstract

The demand for efficient thermal systems has driven significant interest in nano-coolants due to their superior thermal properties as alternatives to traditional coolants like water, ethylene glycol (EG), synthetic oils (polyalphaolefins), and refrigerants (R134a, R410A). These coolants face operational and environmental challenges, including low heat transfer capacity, corrosion, toxicity and ecological effects that limit their efficiency under ideal conditions because of their poor thermophysical properties, which hinder their deployment. This review provides a comprehensive analysis of the prospects, challenges and applications of nano-coolants in various heat exchanger systems. Nanoparticles such as Al O ZnO, Fe O SiO and CNTs are evaluated for their ability to enhance thermal conductivity, stability and heat transfer performance, with key factors influencing thermal enhancement, including size, shape, concentration and preparation methods, being critically examined. The study highlights applications across different heat exchanger configurations, including shell and tube, plate, double pipe, microchannel and spiral heat exchangers, which are evaluated through experimental and numerical results. Performance metrics such as Nusselt number, Reynolds number, heat transfer coefficient and overall heat transfer coefficient are discussed. In addition, the review addresses technical challenges, including agglomeration sedimentation, toxicity, increased viscosity and environmental impact, hindering widespread adoption. Furthermore, it outlines emerging prospects, including life cycle assessment, integration with renewablelar energy and the use of artificial intelligence and machine learning for predictive modeling and optimization, offering sustainable pathways for deployment and system miniaturization. The review demonstrates that, despite challenges, nano-coolants can effectively and efficiently enhance thermal exchange, impacting heat exchanger designs across variouthermophysical properties, which hinder their deployment. This review provides a comprehensive analysis of the prospects, challenges and applications of nano-coolants in various heat exchanger systems. Nanoparticles such as Al O ZnO, Fe O SiO and CNTs are evaluated for their ability to enhance thermal conductivity, stability and heat transfer performance, with key factors influencing thermal enhancement, including size, shape, concentration and preparation methods, being critically examined. The study highlights applications across different heat exchanger configurations, including shell and tube, plate, double pipe, microchannel and spiral heat exchangers, which are evaluated through experimental and numerical results. Performance metrics such as Nusselt number, Reynolds number, heat transfer coefficient and overall heat transfer coefficient are discussed. In addition, the review addresses technical challenges, including agglomeration sedimentation, toxicity, increased viscosity and environmental impact, hindering widespread adoption. Furthermore, it outlines emerging prospects, including life cycle assessment, integration with renewablelar energy and the use of artificial intelligence and machine learning for predictive modeling and optimization, offering sustainable pathways for deployment and system miniaturization. The review demonstrates that, despite challenges, nano-coolants can effectively and efficiently enhance thermal exchange, impacting heat exchanger designs across various