A method for determining the stability of nanofluids.

Abstract

The invention relates to a method for determining the stability of nanofluids. In this method, the stability of nanofluids is determined quickly and easily by measuring the change in the color of the nanofluid due to the deposition of nanoparticles using a color spectrophotometer. This approach can evaluate the stability of nanofluids containing all types of nanoparticles and reduces costs by shortening the testing time.

Description

1 TARIFF A METHOD FOR DETERMINING NANOFLUID STABILITY Technical Field to Which the Invention Relates 5 The invention relates to a method for determining the stability of nanofluids. The invention... In this method, the color of nanofluids changes due to the precipitation of nanoparticles. The resulting change is measured with a color spectrophotometer to determine the stability of the nanofluid. This method is used to identify all types of nanoparticles. It can determine the stability of nanofluids and reduce the cost by 10% by shortening the testing time. It lowers it. State of the Art Nanofluids are nanoscopic fluids that exist within base fluids (such as water, oil, and ethylene glycol). Advanced thermal 15 obtained by dispersing particles of a certain size (1-100 nm in diameter) They are conductive fluids. These nanoparticles are metal oxides, metals, carbides, Nanofluids can be made from nanotubes, graphene, and other nanomaterials. Thanks to its thermal and physical properties, it can heat up to a higher temperature compared to traditional fluids. They offer transmission performance [1]. Nanofluids possess several important properties compared to basic fluids. The 20 most prominent are: Its main feature is enhanced thermal conductivity. The addition of nano-sized particles improves heat conductivity. It provides more efficient heat management by accelerating heat transfer. Furthermore, nanofluids... Their viscosity and density can also vary, affecting their flow and pumpability characteristics. This can affect stability, meaning the homogeneous distribution of nanoparticles within the fluid. Maintaining this level of performance is critical for long-term performance. 25 Nanofluids have a wide range of applications. In heat exchangers, in electronic cooling systems, solar energy systems, automotive in the industry, in engine coolants and biomedical devices They are used to increase energy efficiency thanks to their high thermal conductivity. They have potential. Especially in the fields of microelectronics and nanotechnology. 30 They are considered high-performance cooling solutions. 2 Among the most commonly used nanofluids is water-based alumina (Al₂O₃). nanofluids, copper (Cu) nanofluids and titanium dioxide (TiO₂) Nanofluids stand out. Alumina (Al₂O₃) nanofluids have high thermal conductivity. and due to their chemical stability, they are used in microelectronic cooling systems and solar energy. It is used in energy applications. Copper (Cu) nanofluids are high-performance metals. Thanks to its thermal conductivity, it is used in high-performance applications such as heat exchangers and engine cooling systems. It is effective in high-performance applications. Titanium dioxide (TiO₂) Nanofluids, with their high refractive index and chemical stability, are photocatalytic. It is widely used in applications and solar energy systems. Carbon-based Nanofluids, especially those containing carbon nanotubes (CNTs) and graphene oxide, are among the 10 most common types of nanofluids. Nanofluids offer high thermal conductivity and mechanical strength. Carbon Nanotubes improve heat transfer properties, while graphene oxide nanofluids These nanofluids are used in electronic cooling and energy storage systems. It makes significant contributions to energy saving and environmental sustainability. Nanofluidic stability refers to the homogeneous and stable positioning of nanoparticles within the base fluid. It refers to the ability to remain dispersed in this manner. A stable nanofluid can remain stable for a long time. performs its function without showing precipitation or agglomeration (clumping) throughout. It must be able to protect. This behavior of nanoparticles in liquid is characteristic of nanofluidics. many thermophysical properties such as viscosity, density and thermal / heat conductivity It directly affects it. Among the factors affecting nanofluid stability are 20 nanoparticle concentration, particle size and shape, surface modifications, pH The levels involved include ionic strength and temperature. Surface modifications of nanoparticles It can help it to better match and disperse with the base fluid. Additionally, The chemical composition of the base fluid and the presence of additives can also affect stability. Stability of nanofluids: Mechanical-ultrasonic mixing, surfactant use 25 or by adjusting the pH of the base fluid. However, over time the fluid Nanofluid stability deteriorates due to the settling of particles within it. Nanofluids after preparation and / or determination of their stability at certain intervals is required. Sedimentation method for determining the stability of nanofluids, zeta 30 potential measurement method, UV Vis spectroscopy method, dynamic light scattering spectrometry method (DLS) and scanning / transmission electron microscopy measurement The method (SEM, TEM) is used [2]. The sedimentation method is simple but lengthy. 3 It is a nanofluid stability determination method that is ongoing. In this method, the prepared Nanofluid is filled into a graded tube, and the particles settle over time. This is done by measuring the volume or quantity of a substance. Zeta potential measurement. In this method, nanoparticles are formed between nanoparticles suspended in a nanofluid. The stability of the nanofluid is determined by measuring its electrical repulsive potential. UV Vis 5 In spectroscopy, the stability of the nanofluid is determined using a UV Vis light beam. by directing it onto the nanofluid, the amount of light passing through the nanofluid The stability of the nanofluid is determined by measurement. The DLS method assesses the stability of the nanofluid in relation to light. scattered from nanoparticles within the nanofluid after being directed onto it It is determined by measuring the intensity and variation of light. In the TEM / SEM method, 10 Stability of nanofluid, images of particles precipitated within the nanofluid. It is carried out by examination. Although sedimentation testing is simple and practical, its lengthy nature means that not everyone... It has disadvantages such as not being suitable for nanofluid types and low accuracy. Furthermore, it is insufficient for determining the stability of very light or dark nanofluids. 15 It remains. The zeta potential measurement method is particularly useful for materials containing metallic nanoparticles. It is suitable for nanofluids, but not for all types of nanofluids. It is expensive. Similarly, the DLS method offers high precision and detailed information. However, it requires complex sample preparation and expensive equipment. UV-Vis Spectroscopy and dynamic light scattering spectrometry methods, low 20 in determining the stability of nanofluids containing high concentrations of nanoparticles TEM / SEM methods may be insufficient for determining the stability of nanofluids. These methods are used, but the dried samples must be carefully prepared. It is costly, and there may be difficulties in analyzing non-metallic nanoparticles, and Not suitable for every nanofluid. 25 The limitations and inadequacies of the solutions in the current technology, the difficulty of the methods used, It requires a long time, has low precision and cost, and also all Due to reasons such as its unsuitability for nanofluids, nanofluids An improvement in the methodology for determining determination has become necessary. 30 4 Brief Description and Objectives of the Invention The invention describes the relationship between the reference fluid and the fluid at time t=tn (t: time, n: hours). Color spectrophotometer of the change in color of the nanofluid. Measurement using [method name] and determination of nanofluid stability based on the resulting color difference. It is related to the method of doing it. 5 One aim of the invention is to provide a fast and easy method for determining the stability of nanofluids. The aim is to obtain it. Therefore, its use as an analytical instrument in the method in question. from a practical and fast (measurement time: 1 second) color spectrophotometer It is used in this method. In addition, for example, drying and processing of metal is done using this method. It does not require complex and time-consuming additional processing steps such as coating. 10 Additionally, the invention includes a high-precision nanofluidic stability determination method. This is the aim. Unlike methods that rely on human senses, such as sedimentation. The invention easily reveals color differences that are imperceptible to the human eye. Stability can be determined by measurement. Another aim of the invention is to determine the stability of all nanofluids. The aim is to obtain a usable method for determining the stability of nanofluids. Since the method is based on determining color differences, it is found in nanofluids. It is not affected by nanoparticle type, size, or concentration. Nanofluid Even if it contains nanoparticles at the lowest level (1 ppm), there is a change in the color of the nanofluid. A change occurs. This change in color is observed with a photometric resolution of 0.01%. This can be easily determined with a color spectrophotometer, and the overall color difference A value greater than 0.1 indicates a clear difference between the colors. Therefore, the method that is the subject of this invention ensures the stability of all nanofluids. It can be easily used in the determination process. Another aim of the invention is to develop a low-cost method for determining nanofluid stability. 25 The aim is to obtain it. The method described in the invention does not require the use of standard samples. The absence of such devices and the use of low-cost equipment reduce the cost of this method. It lowers it. 30 5 Explanation of the Figures Figure 1. Flowchart of the nanofluid stability determination method. Figure 2. Nanofluid at the initial stage of preparation when the nanofluid is used as the reference fluid. If selected, the overall color difference determined at different times is relative to the nanofluid. change 5 Figure 3. At different times, when the base fluid is selected as the reference fluid. The variation of the determined overall color difference according to the nanofluid. Detailed Description of the Invention The invention explores how the change in color of nanofluids over time can be studied in terms of color. This relates to a method for determining the stability of nanofluids by measuring them with a spectrophotometer. Color spectrophotometers can numerically express colors and color differences. is being done. International Commission on Lighting (CIE: Commission internationale) The basic colors in the three-dimensional L*a*b* color scale developed by (de l'éclairage). It is expressed with negative and positive numerical values. The L* value is 15 between 0-100. changing (L*=0 black and L*=100 white) and the lightness / darkness of the color This shows positive a* values ​​in red and negative a* values ​​in green. Similarly, positive b* values ​​are shown in yellow, and negative b* values ​​are shown in yellow. It shows the color blue. In this method, the reference is first used in the color measuring device. 20 in which (base) fluid (fluid without nanoparticles) or nanofluid is prepared The initial L*a*b* color values ​​are measured. Then, after being left to stand for a while... The L*a*b* values ​​of the nanofluid are measured and compared to a reference fluid or the nanofluid. The overall color difference ∆E is calculated based on the color values ​​at the moment of initial preparation (equation). 1). ∆E ∆L∗ ∆a∗ ∆b∗ (Equation 1) 25 Here, ∆L∗ is where the base fluid or nanofluid that does not contain nanoparticles is prepared. the difference in thickness / viscosity between the initial sample and the nanofluid after it has been left to stand for a while. The difference lies in the sample size at the initial stage when ∆a∗ and ∆b∗ are prepared for the base fluid or nanofluid. These are the color differences between a nanofluid that has been left to stand for a while and the nanofluid itself. Color differences The following equations 2, 3, and 4 are used for calculation. 30 ∆L∗ L∗ L∗ (equation 2) 6 ∆a∗ a∗ a∗ (equation 3) ∆b∗ b∗ b∗ (equation 4) In these equations, the superscript 1 represents a nanofluid that has been left to stand for a certain period (t=tn), and the superscript 0 represents... reference fluid (the base fluid or the state of the nanofluid at the initial stage of preparation) It specifies the sample. 5 Nanoparticles that are initially suspended in the nanofluid change over time The precipitation causes a change in the color of the nanofluid. The rate of change in the color of the nanofluid is related to the sedimentation rate of its nanoparticles. It is proportional. This allows the color change of the nanofluid to occur at specific time intervals. The stability of the nanofluid is determined with high accuracy using a color measuring device. It is determined. It is a method for determining the stability of nanofluids, and its characteristic feature is; a. the color value of the reference fluid according to the L*a*b* color scale Measurement using a spectrophotometer, b. Color 15 of the nanofluid according to the L*a*b* color scale at times t=t1, t=t2, t=tn. measuring the value with a color spectrophotometer, c. The color values ​​obtained in process step b are compared with the color values ​​obtained in process step a. Calculating the difference (∆E) between the color value and the color value using the following equations: ∆E ∆L∗ ∆a∗ ∆b∗ ∆L∗ L∗ L∗ 20 ∆a∗ a∗ a∗ ∆b∗ b∗ b∗ a*: corresponds to the red (positive) – green (negative) color range in the color coordinate. incoming axis value, b*: corresponds to the yellow (positive) – blue (negative) color range in the color coordinate. incoming axis value, ∆E: color difference, ∆L*: corresponds to the range between two colors: black (L*=0) – white (L*=100). The difference between the axis values, ∆a*: 30 corresponding to the color interval between two colors: red (positive) – green (negative). The difference between the incoming axis values, 7 ∆b*: corresponds to the color interval between two colors: yellow (positive) – blue (negative). The difference between the incoming axis values, Superscript 1: Nanofluid held until time t=tn, Superscript 0: reference fluid sample. d. If the base fluid is chosen as t=t∞, then the base fluid with a ∆E value greater than 40 is base 5. When the fluid type is selected as t=t0, nanofluids with a ∆E value less than 5 The process of definitively appointing someone involves the necessary steps. Method in an application of the invention: a. The color value of the prepared fluid at the initial moment (t=t0) according to the L*a*b* color scale is 10. Measurement using a color spectrophotometer, b. Color of the nanofluid according to the L*a*b* color scale at times t=t1, t=t2, t=tn. measuring the value with a color spectrophotometer, c. The color values ​​obtained in process step b are compared with the color values ​​obtained in process step a. Calculating the difference (∆E) between the color value and the color value using the following equations, 15 ∆E ∆L∗ ∆a∗ ∆b∗ ∆L∗ L∗ L∗ ∆a∗ a∗ a∗ ∆b∗ b∗ b∗ a*: corresponds to the red (positive) – green (negative) color range in the color coordinate. incoming axis value, b*: corresponds to the yellow (positive) – blue (negative) color range in the color coordinate. incoming axis value, ∆E: color difference, ∆L*: 25 corresponding to the interval between two colors: black (L*=0) – white (L*=100). The difference between the axis values, ∆a*: corresponds to the color interval between two colors: red (positive) – green (negative). The difference between the incoming axis values, ∆b*: corresponds to the color interval between two colors: yellow (positive) – blue (negative). The difference between the incoming axis values ​​is 30 Superscript 1: Nanofluid held until time t=tn, Superscript 0: reference fluid sample, 8 d. Stable determination of nanofluids with ∆E values ​​less than 5. It includes the steps involved in the process. With the settling of nanoparticles within the nanofluid over time A change in the color of the nanofluid occurs. This change in color is 5 The overall color difference increases over time compared to the nanofluid at time t0. Initially... The overall color difference between the nanofluid prepared at (t=t0) and the nanofluid at t=tn. The smaller the differences, the more stable the nanofluid. This situation applies to nanofluids. that the nanoparticles inside still maintain their suspended position or This shows that nanoparticles settle at a slow rate. 10 Another application of the invention is the method: a. Color of the base fluid (t=t∞) that does not contain nanoparticles, according to the L*a*b* color scale. measuring the value with a color spectrophotometer, b. The color value of the nanofluid at times t=t1, t=t2, t=tn. Measurement with a spectrophotometer, 15 c. The color values ​​obtained in process step b are compared with the color values ​​obtained in process step a. Calculating the difference (∆E) between the color value and the color value using the following equations: ∆E ∆L∗ ∆a∗ ∆b∗ ∆L∗ L∗ L∗ ∆a∗ a∗ a∗ 20 ∆b∗ b∗ b∗ a*: corresponds to the red (positive) – green (negative) color range in the color coordinate. incoming axis value, b*: corresponds to the yellow (positive) – blue (negative) color range in the color coordinate. incoming axis value, 25 ∆E: color difference, ∆L*: corresponds to the range between two colors: black (L*=0) – white (L*=100). The difference between the axis values, ∆a*: corresponds to the color interval between two colors: red (positive) – green (negative). The difference between the incoming axis values ​​is 30 9 ∆b*: corresponds to the color interval between two colors: yellow (positive) – blue (negative). The difference between the incoming axis values, Superscript 1: Nanofluid held until time t=tn, Superscript 0: reference fluid sample, d. Stable determination of nanofluids with ∆E values ​​greater than 40 5 It includes the steps involved in the process. If the color value of the nanofluid measured at different times (t=tn) is the same as that of the nanoparticle If the color value of the base fluid (t=t∞) is compared with the color value of the fluid that does not contain it, these two fluids The greater the overall color difference between them, the more stable the nanofluid is. 10 This situation indicates that the nanoparticles within the nanofluid are still in suspension. This indicates that the nanoparticles either remained or settled at a slow rate. With the settling of nanoparticles within the nanofluid over time The color of the nanofluid is undergoing a change towards that of the base fluid, and over time these two colors will change. The overall color difference between the fluids is decreasing. 15 In nanofluid stability determination, a reference fluid that does not contain nanoparticles is used. If the base fluid (t=t∞) is chosen, the nanofluid with a ∆E value greater than 40 is stable. It is accepted as such. If used as a reference fluid in nanofluid stability determination. If the initial state of the nanofluid at the time of preparation (t=t0) is considered, then the ∆E value is less than 5. The smaller the nanofluid, the more stable it is. 20 The overall color differences between the two samples are plotted on a graph to analyze the nanofluid. The change in its stability over time is clearly visible (Figure 2, Figure 3). 10 References 1- Ali, ARI, Salam, B. A review on nanofluid: preparation, stability, thermophysical properties, heat transfer characteristics and application. SN Appl. Sci. 2, 1636 (2020). https: / / doi.org / 10.1007 / s42452-020-03427-1 2- Setia, H., Gupta, R., & Wanchoo, RK (2013). Stability of nanofluids. 5 Materials Science Forum, 757, 139–149. https: / / doi.org / 10.4028 / www.scientific.net / msf.757.139

Claims

11 REQUESTS 1. It is a method for determining the stability of nanofluids, and its characteristic is; a. the color value of the reference fluid according to the L*a*b* color scale Measurement with a spectrophotometer, 5 b. Color scale L*a*b* of the nanofluid at times t=t1, t=t2, t=tn Measuring the color value using a color spectrophotometer. c. The color values ​​obtained in process step b are obtained in process step a. The difference (∆E) between the obtained color value and the resulting color value is expressed by the following equations: calculation, 10 ∆E ∆L∗ ∆a∗ ∆b∗ ∆L∗ L∗ L∗ ∆a∗ a∗ a∗ ∆b∗ b∗ b∗ Here, L*: color coordinates black (L*=0) – white (L*=100) 15 The axis value corresponding to the range, a*: red (positive) – green (negative) color in the color coordinate. The axis value corresponding to the range, b*: yellow (positive) – blue (negative) color in the color coordinate. The axis value corresponding to the range is 20 ∆E: color difference, ∆L*: the range between two colors: black (L*=0) – white (L*=100) The difference between the corresponding axis values, ∆a*: red (positive) – green (negative) color between two colors The difference between the axis values ​​corresponding to the range is 25 ∆b*: yellow (positive) – blue (negative) color between two colors The difference between the axis values ​​corresponding to the range, Superscript 1: Nanofluid held until time t=tn, Superscript 0: reference fluid sample, d. If the base fluid is chosen as t=t∞, then the ∆E value is greater than 40, 30 When the base fluid is chosen as t=t0, the ∆E value is less than 5. Stable determination of nanofluids It includes the steps of the process. 12 2. A method for determining the stability of nanofluids according to claim 1. feature; a. the reference fluid is defined as the initial state of the prepared fluid (t=t0). If selected, the base fluid's color will belong to the L*a*b* color scale. The value is measured using a color spectrophotometer, 5 b. Color scale L*a*b* of the nanofluid at times t=t1, t=t2, t=tn Measuring the color value using a color spectrophotometer. c. The color values ​​obtained in process step b are obtained in process step a. The difference (∆E) between the obtained color value and the resulting color value is expressed by the following equations: calculation, 10 ∆E ∆L∗ ∆a∗ ∆b∗ ∆L∗ L∗ L∗ ∆a∗ a∗ a∗ ∆b∗ b∗ b∗ Here, L*: color coordinates black (L*=0) – white (L*=100) 15 The axis value corresponding to the range, a*: red (positive) – green (negative) color in the color coordinate. The axis value corresponding to the range, b*: yellow (positive) – blue (negative) color in the color coordinate. The axis value corresponding to the range is 20 ∆E: color difference, ∆L*: the range between two colors: black (L*=0) – white (L*=100) The difference between the corresponding axis values, ∆a*: red (positive) – green (negative) color between two colors The difference between the axis values ​​corresponding to the range is 25 ∆b*: yellow (positive) – blue (negative) color between two colors The difference between the axis values ​​corresponding to the range, Superscript 1: Nanofluid held until time t=tn, Superscript 0: reference fluid sample, d. Stable determination of nanofluids with ∆E values ​​less than 5 30 to be done It includes the steps of the process. 13 3. A method for determining the stability of nanofluids according to claim 1. feature; a. reference fluid base fluid without nanoparticles (t=t∞) If selected as such, the base fluid's color will belong to the L*a*b* color scale. The value is measured using a color spectrophotometer, 5 b. The color value of the nanofluid at times t=t1, t=t2, t=tn. Measurement using a spectrophotometer, c. The color values ​​obtained in process step b are obtained in process step a. The difference (∆E) between the obtained color value and the resulting color value is expressed by the following equations: calculation, 10 ∆E ∆L∗ ∆a∗ ∆b∗ ∆L∗ L∗ L∗ ∆a∗ a∗ a∗ ∆b∗ b∗ b∗ Here, L*: color coordinates black (L*=0) – white (L*=100) 15 The axis value corresponding to the range, a*: red (positive) – green (negative) color in the color coordinate. The axis value corresponding to the range, b*: yellow (positive) – blue (negative) color in the color coordinate. The axis value corresponding to the range is 20 ∆E: color difference, ∆L*: the range between two colors: black (L*=0) – white (L*=100) The difference between the corresponding axis values, ∆a*: red (positive) – green (negative) color between two colors The difference between the axis values ​​corresponding to the range is 25 ∆b*: yellow (positive) – blue (negative) color between two colors The difference between the axis values ​​corresponding to the range, Superscript 1: Nanofluid held until time t=tn, Superscript 0: reference fluid sample, e. Stable determination of nanofluids with ∆E values ​​greater than 40 30 to be done It includes the steps of the process. 14 4. A method for determining nanofluid stability according to claim 1. Its characteristic is that the reference fluid is a base fluid (t=t∞) that does not contain nanoparticles. It is the fact that.

5. A method for determining the stability of nanofluids according to claim 1. The characteristic is that the reference fluid is in its state at the initial moment of nanofluid preparation (t=t0). It is the fact that.

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