Nanofluids represent a cutting-edge frontier in heat transfer technology, offering enhanced thermal properties that revolutionize various industries. At Thermtest, we recognize the immense potential of these specialized fluids and have developed advanced measurement solutions to accurately characterize their thermal conductivity. Our Versatile Measurement Platform (MP-V), equipped with the innovative THW-L200 sensor, stands at the forefront of nanofluid analysis, providing precise and reliable measurements even for electrically conductive samples. This application sheet delves into the world of nanofluids, their industrial importance, and how Thermtest’s evolving intelligence empowers researchers and engineers to unlock their full potential.
Nanofluids (NF) are a specialized class of heat transfer fluids. These fluids are composed of nanoparticles (typically 1-100nm in size) suspended in a base fluid such as water, ethylene glycol, or oil. Nanoparticles (NP) come in many different shapes and sizes and are used to enhance the base fluids thermal conductivity and heat transfer characteristics. Particle type, size, shape, and concentration all play important roles in altering the thermal properties of the base fluid.
Nanofluids play a significant role in enhancing thermal management in battery systems, particularly for electric vehicles (EVs). Nanofluids exhibit higher thermal conductivity than conventional coolants which inherently increases the fluids overall heat transfer coefficient leading to more efficient heat transfer from the battery cell to the cooling fluid. As a result, NFs significantly reduce battery temperature, improving temperature uniformity and energy efficiency. Due to their enhanced thermal properties nanofluids can achieve the same cooling effect at a lower flow rate compared to conventional coolants. This leads to reduced pumping power and allows for the design of more compact and lightweight battery systems, which is beneficial for EVs where space and weight are critical factors.
Efficient heat transfer is crucial for battery performance and safety in all industries. Proper thermal management not only improves overall battery performance, but also prevents overheating which can lead to thermal runaway. Thermal runaway is a dangerous chain reacting that can occur inside the battery causing fires and potential explosions. Batteries typically operate at optimal temperatures of 15-35°C. Efficient heat transfer assists in maintaining this ideal temperature, which slows the degradation process improving the battery lifespan. Better heat transfer enables faster charging rates without the risk of damage from excessive heat generation. By ensuring efficient heat transfer, battery systems can achieve better performance, longer lifespans, and significantly improved safety profiles, all of which are critical for the widespread adoption of electric vehicles and large-scale energy storage solutions.
The use of nanofluids in automotive cooling systems has increased significantly over the years. The addition of nanoparticles to base fluid increases the overall heat transfer coefficient, leading to better efficiency in radiators and other heat exchangers. The base fluids improved efficiency allows for better cooling at lower flow rates, leading to more compact cooling system designs. By improving heat dissipation, NFs help maintain optimal engine temperatures leading to better fuel efficiency, reduced emissions, and overall improved system efficiency.
NFs show significant potential in enhancing the performance and efficiency of Heating, Ventilation, and Air Conditioning (HVAC) systems. Improved thermal conductivity of the fluid leads to more efficient heat transfer in HVAC systems. This improvement allows HVAC systems to maintain desired temperatures with less energy consumption. Research by Okonkwo et al., demonstrates the energy consumption of HVAC units is reduced by roughly 20% when using nanofluids due to their superior thermal properties. This not only contributes to lowering operational costs, but also contributes to reducing environmental impact. Like automotive cooling systems, the use of NFs allows for more compact sleek designs and better overall performance of the HVAC system.
Nanofluids show strong potential for use as heat transfer fluids on earth and in space too. NFs offer significant improvements to thermal management, efficiency, and performance which are all crucial factors to travel outside the earth’s atmosphere. Nanofluids superior heat transfer properties help maintain optimal operating temperatures of critical systems in spacecrafts such as engines and avionics. These properties also help extend the lifespan of various aerospace components by preventing overheating and reducing thermal stress. Improving the thermal management capabilities in these spacecrafts using NFs, leads to more efficient cooling systems, better fuel efficiency, and more compact and lightweight designs which are crucial to evolving space travel.
Thermtest’s Versatile Measurement Platform (MP-V) is designed to test the absolute thermal conductivity, thermal diffusivity, specific heat, and thermal effusivity of solids, liquids, pastes, and powders. The MP-V features a powerful combination of transient plane source (TPS, ISO 22007-2) and transient hot-wire (THW, ASTM D7896-19) methods with a variety of compatible sensors.
The Transient Hot Wire (THW-L200) sensor is one of the many sensors offered with the MP-V. The THW-L200 sensor provides simple yet accurate measurements of liquids and phase change materials (PCMs) from 0.01 to 2 W/m·K via the transient hot wire method. The sensor is electrically connected to a power supply and sensing circuit. A current passes through the sensor and increases the temperature, which is recorded over time. The heat generated is then diffused into the sample at a rate dependent on the thermal transport characteristics of the material.
In the past, measuring nanofluids with the THW method has been a challenge due to the electrical properties of the fluid. Nanoparticles not only increase a base fluids thermal conductivity but frequently also increase the fluids electrical conductivity. The current carried in an electrically conductive fluid can interfere with the electrical signals used in the THW method, leading to inaccurate measurements or signal noise. Depending on the composition, many electrically conductive fluids can have chemical reactions with the wire probe, altering its properties or degrading it over time.
Thermtest’s THW-L200 sensor has accessories designed to help remove the barriers from measuring with electrically conductive fluids like nanofluids. The available PEEK bucket for testing aids in reducing electrical interference and polarization effects that might otherwise be present with the standard steel bucket. Epoxy coatings are also available with Thermtest’s THW sensors to prevent reactions of the fluid with the wire material, that may cause corrosion and damage.
To demonstrate the powerful capabilities of Thermtest’s THW-L200 sensor, a 20mL sample of brine was measured using the MP-V. While brine is not a nanofluid, it is electrically conductive. Though it does not contain nanoparticles like typical nanofluids, brines varying concentrations of salt can simulate the conductivity changes that occur in nanofluids with different particle loadings.
The sample was added to the PEEK bucket, and the sensor was then inserted into the solution. Optimal parameters were determined using the detect current setting to achieve appropriate temperature rise and accurate, repeatable results. Three measurements were run at ambient temperature with a delay of ten minutes between each test. Optimal heating power of 300mW was determined via the detected current setting.
The results were in good agreement with the stated accuracy and repeatability of the THW-L200 sensor (1-2%). The average of the three tests gave a thermal conductivity result of 0.575 W/mK with a relative standard deviation of 0.06%, which is within 0.5% of the expected literature value (0.571 W/mK).
Thermtest’s commitment to evolving intelligence and empowering understanding is exemplified in our approach to nanofluid measurement. The MP-V with THW-L200 sensor is continually overcoming traditional challenges associated with electrically conductive fluids. By providing accurate, repeatable results and raw data, we enable our customers to gain true insight into the thermal properties of nanofluids. As nanofluids continue to transform industries from automotive cooling to space exploration, Thermtest remains dedicated to advancing measurement methods and delivering innovative solutions. Our passion for thermal conductivity and unwavering commitment to accuracy position us as the apex provider in this rapidly evolving field, empowering you to push the boundaries of heat transfer technology with confidence.
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