Vol.:(0123456789) Iranian Journal of Science and Technology, Transactions of Mechanical Engineering https://doi.org/10.1007/s40997-024-00772-z REVIEW PAPER A Review on Hybrid Nanofluids: Preparation Methods, Thermo Physical Properties and Applications Javvadi Eswara Manikanta 1  · Chetan Nikhare 2  · Naveen Kumar Gurajala 3  · Nitin Ambhore 4  · R. Raj Mohan 5 Received: 2 January 2024 / Accepted: 28 April 2024 © The Author(s), under exclusive licence to Shiraz University 2024 Abstract The adoption of hybrid fluids in machining processes offers multiple benefits, including improved heat dissipation, enhanced lubrication, extended tool life, better surface quality, and reduced environmental impact. These advantages make hybrid fluids an attractive choice for modern machining applications, where efficiency, performance, and sustainability are paramount. A hybrid nanofluid consists of two or more different types of nanoparticles in the base fluid. The primary goal of creating a hybrid nanofluid is to enhance thermal conductivity and heat transfer properties when combined than when employed separately as a standard mono-nanofluid. This paper reports various hybrid nanofluids used in the machining industries. Also, hybridization can make hybrid nanofluids extremely effective at improving heat transfer, surface roughness, and tool life. This study provides an overview of the thermophysical characteristics of hybrid nanofluids and preparation techniques. Keywords Hybrid nanofluid · Thermal conductivity · Heat transfer · Viscosity · Density 1 Introduction The diffusion of tiny particles (below 100 nm) in a liquid is known as a Nanofluid (Shafi and Charoo 2021). According to previous research, when nanoparticles are dispersed in a medium like water, mineral oil, or engine oil, the high heat extraction capacity greatly improves the thermos physical properties and rheological properties. Enhancing heat trans- fer and lowering energy use are major research priorities (Kursus et al. 2022; Ma et al. 2022). One way to enhance the heat transfer process is by adding materials with strong thermal conductivity to the base fluid. Through the use of extremely tiny suspended solid particle matter in the fluid, researchers have worked hard to increase heat transmission over the years (Atashafrooz et al. 2023; Amiri Delouei et al. 2022). Hybrid nanofluid have a wide range of applications across various industries due to their unique combination of base fluids and dispersed nanoparticles. These mainly include machining industries, cooling systems, biomedical, energy storage etc. Figure 1 shows use of nanofluid for vari- ous application. However, these fluids had several issues, including the particle swarm effect, channel path clogging, transmission device erosion, a decrease in pressure loss, and sedimenta- tion. Particle settling created sludge deposits, increased ther- mal resistance, and increased thermal resistance in addition to decreasing the fluid's capacity to transmit heat effectively (Atashafrooz et al. 2023; Amiri Delouei et al. 2022). Dong et al. (2013) investigated nano-copper particle conductivity and discovered that the addition of less than 1% concentration of copper nanoparticles increased con- ductivity for ethylene glycol and oil. Alumina and copper oxide nanofluid based on ethylene glycol and water were examined for their thermal conductivity at various volume concentrations and temperatures. Ethylene glycol and water * Nitin Ambhore nitin.ambhore@viit.ac.in Chetan Nikhare cpn10@psu.edu 1 Department of Mechanical Engineering, Shri Vishnu Engineering College for Women, Bhimavaram 534202, India 2 Department of Mechanical Engineering, The Behrend College, The Pennsylvania State University, Erie 16563, USA 3 Department of Mechanical Engineering, CMR College of Engineering & Technology, Hyderabad, Telangana 501401, India 4 Department of Mechanical Engineering, Vishwakarma Institute of Information Technology, SPPU, Pune 411048, India 5 School of Mechanical Engineering, SASTRA Deemed to be University, Thanjavur 613401, India