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Motor Cooling
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
Due to the recent developments in nanotechnology, a new class of heat transfer fluid called nanofluid has attracted considerable attention from researchers and engineers. A nanofluid is a solid–liquid mixture produced by dispersing nanoparticles in a liquid (usually water, ethylene glycol, or minerals oil) to display enhanced heat transfer due to the combination of convection and conduction and additional energy transfer by particle dynamics and collision [11.93]. The studies of nanofluids with phase change have shown that the presence of nanoparticles in liquid can enhance critical heat flux (CHF) in boiling heat transfer. The mechanism of the CHF enhancement is attributed to the deposition of nanoparticles on the boiling surfaces with foamed porous layers [11.94].
Renewable Energy Sources and Water Management
Published in Barney L. Capehart, William J. Kennedy, Wayne C. Turner, Guide to Energy Management, 2020
Barney L. Capehart, William J. Kennedy, Wayne C. Turner
A need for temperatures of 120°C or higher usually requires a concentrating collector. The surface of a concentrating collector must be highly reflective, enabling concentration of the sun’s rays on the heat absorption device. The heat transfer fluid can be a liquid or gas. A concentrating collector is usually also a tracking collector in order to keep the sun’s rays focussed on a small surface. A typical design for a parabolic trough-type, tracking collector is shown in Figure 15-6. The collector can track in an east to west direction to follow the daily sun, in a north to south direction to follow the seasons, or both. Concentrating collectors that accurately track the sun’s position are more efficient than those that do not track the sun’s position as well.
Hybrid Nanofluids
Published in S. Harikrishnan, A.D. Dhass, Thermal Transport Characteristics of Phase Change Materials and Nanofluids, 2023
NP suspensions of Al2O3 (10–20 nm) and SiO2 (40–50 nm) were tested for thermal conductivity in pure methanol at 293.15°C. Al2O3 and SiO2 showed a 10.74% and 14.29% increase above base fluid at 0.5 vol%, respectively. SiC NPs dispersed in nanofluids with water content of 0–1 vol% have been observed. An inverse relationship between conductivity and particle size was shown to be noticeable in the nanofluid at 0.1 vol% of NPs, according to this study. In order to determine the heat conductivity of a fluid, KD2-Pro thermal analyzers are utilized. However, single NP dispersion in the base fluids has a number of limitations that need to be considered. The most critical issue was the thermal system’s inability to operate properly due to nanofluids being clogged in the flow channels as they transit through the device. Because NPs damage the flow channel walls, their performance is also affected by this corrosive effect. Different conventional fluids are mixed with hybrid NPs to create these hybrid nanofluids, which can then be used in a variety of ways. Because of their exceptional thermal properties, hybrid nanofluids have attracted a lot of attention as a thermal/working fluid. Water, ethylene glycol, oil mixes, and ethylene/water combinations are the most commonly employed fluids for the synthesis of hybrid nanofluids. Nanofluids are stable when the particle size is kept below 100 nm, which is crucial for the synthesis of hybrid nanoparticles. Nanofluids as a heat transfer fluid, however, are only in the early stages of research based on simulation, and at present, people are focusing on understanding deeply the changes introduced in thermophysical properties and improving fluid heat transfer characteristics after the inclusion of nanoparticles. These synergistic nanofluids are employed in cooling and heating systems. The absorber plate’s heat is immediately transferred to the circulating fluid, increasing the PV/T system’s efficiency and performance. For cooling photovoltaic panels, water or air circulates to increase the efficiency of the solar cell. Due to their better thermal behavior, nanofluids are increasingly used to substitute working fluids in PV cells to further improve the cooling effect. With their higher thermal conductivity, nanofluids can more effectively replace base fluids and increase system performance[6–11].
Chebyshev spectral approach to an exponentially space-based heat generating single-phase nanofluid flowing on an elongated sheet with angled magnetic field
Published in Numerical Heat Transfer, Part B: Fundamentals, 2023
MD. Shamshuddin, T. M. Agbaje, K. K. Asogwa, G. Makanda
A revolutionary heat transfer fluid termed as “nanofluid” has emerged because of scientific and nanotechnology advancements. Nanofluids are made up of nonmetallic or metallic nanometer sized particles (less than 100 nanometer) dispersed in various traditional fluids. There has been an explosion of study and invention utilizing amazing uses of nanofluids in industries including electrical cooling, solar energy, power generation, water heaters, biomedical, among others, over the previous few decades. The idea of nanofluids was suggested by Choi [1] at the NAL (National Argon Laboratory). The effective thermal conductivity of nanotube-in-oil suspensions is measured and proposes the usual thermal behavior which testifies the highest thermal conductivity [2]. The nanofluid is a suitable coolant and its excellent thermal properties contribute to the high heat transfer of the radiator. Arora and Gupta [3] investigated the hydrothermal performance of nanofluids in flat tube automobile radiators. Murshed and de Castro [4] evaluated the studies and improvement of conduction and convection warmth switch traits of ethylene glycol-primarily based totally nanofluids. The results demonstrated that those nanofluids own significantly better thermal conductivity and convective warmth switch traits as compared to their base fluids that is ethylene glycol and its aqua mixture. Further relevant literature is found in Refs. [5–9].
Hybrid photovoltaic–thermal system for simultaneous generation of power and hot water utilising mobiltherm as heat transfer fluid
Published in International Journal of Sustainable Energy, 2021
Sudhansu Sekhar Das, Pramod Kumar, Sarbjot Singh Sandhu
The desired thermo-physical property of a heat transfer fluid includes high thermal conductivity, low viscosity and high heat capacity. Apart, it should also possess high boiling point, low melting point and low vapour pressure (Cordaro, Rubin, and Bradshaw 2013; Pacio and Wetzel 2013). Several thermal oils, namely Syltherm XLT, Marlotherm SH, Syltherm 800, Santotherm 59, Santotherm LT, Marlotherm X and Therminol D12, were concluded to be thermally stable up to higher temperatures (Ouagued, Khellaf, and Loukarfi 2013). Apparently too low and high temperatures can affect the thermal performance of any fluid. The fluid should be tested for its efficient operating range of temperatures prior to its application. The selection of any particular heat transfer fluid has to be in line with the objectives to be attained. Mobiltherm was adopted as the heat transfer fluid in this research as specific heat and thermal conductivity of the fluid are conducive for adequate heat transfer.
Entropy generation optimization in an unsteady hybrid nanofluid flow between two rotating disks: a numerical bioconvection model
Published in Waves in Random and Complex Media, 2022
A. Mahesh, C. S. K. Raju, M. Jayachandra Babu, B. Madhusudhana Rao, S. V. K. Varma, B. C. Prasannakumara
Nanofluids have been developed as a novel type of heat transfer fluid that may be used in lieu of conventional fluids in industrial operations. Due to their tiny size, they can considerably reduce erosion and corrosion. They are used in a variety of applications, including refrigeration, heat exchangers, and electronic device cooling. The rheology of alumina and silver nanoparticles across an exponentially expanding convective wall with a heat source/sink was given by Abrar and Awais [43]. With Joule heating and thermal radiation, Abrar et al. [44] described how entropy grows during ferrofluid peristaltic movement. They discovered that increasing the Joule heating parameter raises the temperature of the fluid. In a ciliated flexible horizontal (inclined) tube with a heat source, Abrar et al. [45–47] investigated the entropy production analysis of various nanofluid flows. They found that with increasing nanoparticle concentration, the entropy number rises. Qayyum et al. [48] scrutinized an unsteady squeezing flow of a nanofluid in a rotating channel on a lower permeable stretching wall. The nanomaterial (CNTs) movement was explored quantitatively by Qureshi et al. [49]. It is discovered that there was an enrichment in fluid temperature due to the heat source parameter. Several researchers [50–52] examined the effects of heat-generating parameters on various nanofluid flows at various boundary conditions. Hybrid nanofluid is a variant of mono nanofluid that contains several nanoparticles. Thus, hybrid fluids have superior heat transport characteristics than mono nanofluids. These find use in a variety of applications, including solar collectors and military equipment. Aly and Pop [53–55] examined the water-based hybrid nanofluid flow over a permeable stretching/shrinking sheet with different boundary conditions. Later, various researchers [56–58] conducted different studies including two-dimensional incompressible hybrid nanofluid jet flow with power law vertical velocity and the heat transfer with radiation.