Preparation method of MgO nanofluid coolant

Abstract

This invention discloses a method for preparing MgO nanofluid coolant. The method includes the following steps: (1) ball milling MgO powder using a planetary ball mill to reduce the particle size of the MgO particles to below 100 nm; (2) adding the ball-milled MgO powder and a dispersant to a base solution composed of water and propylene glycol, and magnetically stirring to prepare a mixed solution; (3) using an ultrasonic cell disruptor to sonicate the mixed solution to obtain nanofluid. The preparation method of this invention is mild and can be completed at room temperature. The water and propylene glycol mixed base solution is stable and non-corrosive at high temperatures. MgO forms a stable colloidal solution in the base solution, exhibiting good dispersion stability and high thermal conductivity and low viscosity in the range of 25℃ to 105℃. The novel coolant obtained by this invention is beneficial for more efficient heat dissipation in cooling systems such as engines.

Description

Technical Field

[0001] This invention belongs to the field of thermal management functional fluid technology, specifically, it relates to a method for preparing MgO nanofluid coolant. Background Technology

[0002] With the advancement of technology and the continuous improvement of energy utilization, energy power devices are developing towards higher power, smaller size, and miniaturization, leading to a sharp increase in the heat exchange intensity and heat load of heat exchange systems. As the performance indicators of heat exchange systems, such as heat exchange efficiency and space utilization, continue to improve, higher demands are placed on heat exchange enhancement technologies. Solving the problem of efficient heat exchange within limited spaces has become a new research hotspot. Enhanced convective heat transfer technology is the most studied and widely applied enhancement technology. Most convective heat transfer enhancement technologies are based on the research of heat transfer equipment, such as increasing the heat exchange area, surface treatment of heat exchange surfaces, and external disturbances. However, with the development of new, efficient, and compact heat exchange systems, the difficulty of improving heat exchanger performance using existing enhancement technologies is gradually increasing. The low thermal conductivity of traditional heat exchange working fluids has become a bottleneck limiting the improvement of heat exchange system efficiency. Therefore, developing a new heat exchange working fluid with high thermal conductivity and good stability has become an important research topic in enhanced heat transfer technology.

[0003] Dispersing high thermal conductivity nanoparticles in traditional fluids to form uniform and stable nanofluids can significantly improve the thermal conductivity of traditional liquids. Compared to traditional heat exchangers, nanofluid coolants exhibit superior heat transfer efficiency. For many years, researchers have conducted experimental studies on applications such as vehicle engine cooling, heat pipes, and nuclear reactor cooling, achieving promising results. The emergence and development of nanofluid coolants have pointed to new directions in the exploration of highly efficient heat transfer media.

[0004] MgO nanoparticles are highly favored due to their high thermal conductivity, good stability, environmental friendliness, and low cost, and their dispersion in liquids to form nanofluids has been extensively studied. However, MgO nanoparticles are prone to agglomeration in base liquids. This not only reduces the thermal conductivity of the nanofluid but also leads to an abnormal increase in fluid viscosity, increasing flow resistance. Secondly, traditional base liquids (such as water, oil, and alcohol) all have performance limitations. Water has high thermal conductivity and low viscosity, but its low boiling point and high freezing point make it unsuitable for high-temperature or extremely cold conditions. Oil and alcohol have both low freezing points and high boiling points, making them applicable to a wide temperature range, but their low thermal conductivity and high viscosity may increase pumping energy consumption, limiting their application in heat exchange systems.

[0005] Currently, some researchers have improved the dispersion of MgO nanofluids by modifying the MgO surface or adding dispersants, which has yielded some results, but the dispersibility still needs further improvement. While compounding alcohols with water can broaden the applicable temperature range, some alcohol-based solutions are prone to degradation and corrosion of equipment at high temperatures and are toxic, making them environmentally unfriendly.

[0006] Therefore, there is still great potential to be explored in the study of MgO dispersibility and the selection of base solutions. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, the present invention aims to provide a water / propylene glycol-based MgO nanofluid coolant and its preparation method, which utilizes inexpensive and readily available raw materials. The preparation method of the present invention employs mild conditions; the water and propylene glycol mixture is stable and non-corrosive at high temperatures, and MgO forms a stable colloidal solution in the mixture, exhibiting good dispersion stability. It also possesses high thermal conductivity and low viscosity within the temperature range of 25℃ to 105℃. This novel coolant, obtained by the present invention, is beneficial for more efficient heat dissipation in cooling systems such as engines.

[0008] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0009] A method for preparing an MgO nanofluid coolant includes the following steps: (1) The MgO powder was ball-milled using a planetary ball mill so that the particle size of the MgO particles after ball milling was reduced to below 100 nm; (2) Add the ball-milled MgO powder and dispersant to the base liquid composed of water and propylene glycol, stir magnetically, and prepare a mixed solution; in the mixed solution, the MgO mass concentration is 0.2%–0.6%, and the volume ratio of water to propylene glycol is 1:2; (3) The mixed solution was ultrasonically processed using an ultrasonic cell disruptor to obtain nanofluids.

[0010] In this invention, in step (1), the ball-to-material ratio is 5:1 to 10:1, the ball milling speed is 500-700 rpm, and the ball milling time is 12-15 h.

[0011] In this invention, in step (2), the dispersant is sodium dodecyl sulfate, and the mass ratio of MgO to sodium dodecyl sulfate is 1:1 to 1:2.

[0012] In this invention, in step (2), the magnetic stirring speed is 400-600 rpm and the magnetic stirring time is 10-30 min.

[0013] In this invention, in step (3), the ultrasonic power is 600-800W and the ultrasonic time is 90min-120min.

[0014] The present invention also provides an MgO nanofluid coolant prepared by the above preparation method; preferably, its thermal conductivity is between 0.4828 W / mK and 0.5311 W / mK and its viscosity is between 1.5227 mPa·s and 4.0396 in the temperature range of 25℃ to 105℃.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention employs a combined mechanical and chemical method to enable MgO nanoparticles to form a stable colloidal solution in a water and propylene glycol mixed base solution, avoiding the aggregation of MgO nanoparticles, thereby improving the thermal conductivity of the water / propylene glycol-based MgO nanofluid and reducing its viscosity. Secondly, the base solution is a mixture of water and propylene glycol, achieving complementary properties between the two base solutions. This not only broadens the applicable temperature range of the base solution but also reduces its viscosity. Furthermore, propylene glycol has better thermal stability, lower toxicity, and is biodegradable and environmentally friendly.

[0016] (2) The process is simple, the preparation conditions are mild, the production is easy, the raw materials are cheap and readily available, and it can be produced and applied on a large scale.

[0017] (3) The nanofluid of the present invention has good long-term dispersion stability and high thermal conductivity and low viscosity in the temperature range of 25℃-105℃. The present invention can be applied to the field of thermal management and heat dissipation, which is beneficial to more efficient heat dissipation of cooling systems such as automobile engines. Attached Figure Description

[0018] Figure 1 Flowchart for the preparation of water / propylene glycol-based MgO nanofluids.

[0019] Figure 2 SEM images of MgO at different ball milling times.

[0020] Figure 3 (a) Initial state of samples with different dispersant addition amounts (SN) and after standing for 7 days; (b) Zeta potential diagram of samples in the initial state; (c) Absorbance of the upper layer of the sample changing over time.

[0021] Figure 4 (a) Initial state of samples of different concentrations and after standing for 7 days; (b) Zeta potential of samples of different concentrations in their initial state; (c) Absorbance of the supernatant of samples of different concentrations over time.

[0022] Figure 5 (a) Thermal conductivity of water / propylene glycol-based MgO nanofluids at different concentrations; (b) Thermal conductivity of water / propylene glycol-based MgO nanofluids at different temperatures; (c) Thermal conductivity increase at different concentrations.

[0023] Figure 6(a) Viscosity graphs of water / propylene glycol-based MgO nanofluids at different concentrations; (b) Viscosity graphs of water / propylene glycol-based MgO nanofluids at different temperatures. Detailed Implementation

[0024] The preferred embodiments of the present invention are given below with reference to the accompanying drawings to illustrate the technical solution of the present invention in detail.

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention. A method for preparing MgO nanofluid with good performance includes the following steps: (1) Ball milling of MgO powder: First, weigh a certain amount of MgO powder and grinding balls and put them into a ball milling jar to mix. Then, put the ball milling jar into a planetary ball mill and mill for a certain period of time. Take out the milled MgO for later use.

[0026] (2) Prepare the base solution by measuring water and propylene glycol in a graduated cylinder and mixing them in a beaker as the base solution.

[0027] (3) Prepare a mixed solution by weighing the MgO powder and dispersant sodium dodecyl sulfate after ball milling in step (1) and adding them to the base liquid in step (2) and stirring magnetically to prepare a mixed solution.

[0028] (4) To prepare nanofluids, the mixed solution from step (3) was ultrasonicated for a certain time using an ultrasonic cell disruptor to obtain nanofluids.

[0029] Below are some specific examples.

[0030] In the examples, the thermal conductivity of the samples was measured using a transient hot wire; the viscosity of the samples was measured using a digital rotational viscometer.

[0031] Example 1

[0032] A method for preparing a water / propylene glycol-based MgO nanofluid includes the following steps: (1) Ball milling of MgO powder: Weigh grinding balls with a ball-to-powder ratio of 10:1 and MgO powder, load them into a ball mill jar and ball mill for 12 hours at a speed of 600 rpm.

[0033] (2) Prepare the base solution, in which the volume ratio of water to propylene glycol in the mixed base solution is 2:1.

[0034] (3) Prepare a mixed solution by adding the ball-milled MgO powder and the dispersant sodium dodecyl sulfate to the base liquid (MgO mass concentration is 0.2%), wherein the mass ratio of MgO to dispersant (SN) is 1:2, and magnetically stir for 20 min at a magnetic stirring speed of 500 rpm to obtain a mixed solution.

[0035] (4) Prepare nanofluids by sonicating the prepared mixed solution for 90 min with an ultrasonic power of 700 W to obtain MgO nanofluids with different amounts of dispersant.

[0036] Example 2

[0037] Other implementation conditions are the same as in Example 1, except that in step (3), the mass concentration of MgO is 0.4%.

[0038] Example 3

[0039] Other implementation conditions are the same as in Example 1, except that in step (3), the mass concentration of MgO is 0.6%.

[0040] Example 4

[0041] Other implementation conditions are the same as in Example 1, except that in step (1), the ball milling time is 15 hours.

[0042] Example 5

[0043] Other implementation conditions are the same as in Example 1, except that in step (3), the mass ratio of MgO to dispersant (SN) is 1:1.

[0044] Comparative Examples 1-3 Other implementation conditions are the same as in Example 1, except that in step (3), the mass ratio (SN) of MgO to dispersant is 1:3, 1:4 or 1:5.

[0045] Comparative Examples 4 to 5 Other implementation conditions are the same as in Example 1, except that in step (3), the mass concentration of MgO is 0.8% or 1.0%.

[0046] like Figure 2 The image shows the morphology of MgO after ball milling, as observed by SEM. When the ball milling time reaches 12 h, the particle size of MgO can be reduced to below 100 nm; when the ball milling time is extended by 15 h, the change in particle size slows down significantly.

[0047] like Figure 3 As shown, Figure 3 (a) shows the initial state of samples with different dispersant addition amounts (SN) and the 7-day standing time. It can be seen that the SN of 1:1 in Example 5 and 1:2 in Example 1 had smaller sedimentation after standing for 7 days. Figure 3 (b) is the Zeta potential diagram of the initial state of the sample. It can be seen that the Zeta potential of the samples in Example 1 and Example 5 is relatively large, reaching the potential threshold for system stability. Among them, the Zeta potential of the sample in Example 1 is the largest, which is 40.3mV. Figure 3(c) in the figure shows the change of absorbance of the upper liquid of the sample over time. The absorbance of the upper liquid of the samples in Examples 1 and 5 decreased by a small amount; while the samples in Comparative Examples 1-3 with SN of 1:3, 1:4 or 1:5 had poor long-term nanofluid dispersion stability.

[0048] like Figure 4 As shown, the dispersion stability of nanofluids with different MgO mass concentrations is characterized by visual sedimentation, absorbance, and Zeta potential. Figure 4 As can be seen in (a), the samples in Examples 1, 2 and 3 with concentrations of 0.2%, 0.4% and 0.6% showed almost no obvious sedimentation trend after standing for 14 days; Figure 4 (b) The Zeta potentials of the samples in Examples 1, 2 and 3 with concentrations of 0.2%, 0.4% and 0.6% were all greater than 30 mV, reaching the potential threshold for system stability; Figure 4 In (c), the absorbance decreases in Examples 1, 2 and 3 with concentrations of 0.2%, 0.4% and 0.6% were only 1.7%, 3.4% and 4.1%, respectively, and the absorbance tended to stabilize after 3 days of standing, indicating that the nanofluids in these three concentration ranges can achieve long-term stable dispersion; while in Comparative Examples 4 and 5 with concentrations of 0.8% and 1.0%, the nanofluid dispersion stability of the samples was poor over a long period of time.

[0049] like Figure 5 As shown, for the coolant obtained in Examples 1-3, Figure 5 (a) Thermal conductivity diagram of water / propylene glycol-based MgO nanofluids with different concentrations; Figure 5 (b) Thermal conductivity diagrams of water / propylene glycol-based MgO nanofluids at different temperatures; Figure 5 (c) shows the increase in thermal conductivity at different concentrations. Figure 6 (a) Viscosity diagrams of water / propylene glycol-based MgO nanofluids at different concentrations; Figure 6 (b) Viscosity diagrams of water / propylene glycol-based MgO nanofluids at different temperatures. Figure 5 As shown in (a), the thermal conductivity increases with increasing concentration, with the 0.6% concentration showing the most significant improvement, reaching 0.4828 W / mK at 25℃, exhibiting superior thermal conductivity compared to the base working fluid. Figure 5 (b) shows that within the temperature range of 25-105℃, the thermal conductivity continuously increases with increasing temperature. When the temperature rises to 105℃, the thermal conductivity further increases to 0.5311 W / mK, indicating that its thermal conductivity is further optimized with increasing temperature. Regarding viscosity properties, such as... Figure 6(a) shows that 0.6% MgO has a low viscosity, with a viscosity of only 4.0396 mPa·s at 25°C. At the same time, its viscosity shows a significant decreasing trend as the temperature increases. When the temperature rises to 105°C, the viscosity drops to 1.5227 mPa·s. This value is far below the upper limit of viscosity commonly used in industrial heat exchange media and will not have an adverse effect on the flow resistance of the heat exchange system.

[0050] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as defined by the appended claims and their equivalents.

Claims

1. A method for preparing an MgO nanofluid coolant, characterized in that, Includes the following steps: (1) The MgO powder was ball-milled using a planetary ball mill so that the particle size of the MgO particles after ball milling was reduced to below 100 nm; (2) Add the ball-milled MgO powder and dispersant to the base liquid composed of water and propylene glycol, stir magnetically, and prepare a mixed solution; in the mixed solution, the MgO mass concentration is 0.2%–0.6%, and the volume ratio of water to propylene glycol is 2:1; (3) The mixed solution was ultrasonically processed using an ultrasonic cell disruptor to obtain nanofluids.

2. The method for preparing the MgO nanofluid coolant according to claim 1, characterized in that, In step (1), during the ball milling process, the ball-to-material ratio is 5:1 to 10:1, the ball milling speed is 500-700 rpm, and the ball milling time is 12-15 h.

3. The method for preparing the MgO nanofluid coolant according to claim 1, characterized in that, In step (2), the dispersant is sodium dodecyl sulfate, and the mass ratio of MgO to sodium dodecyl sulfate is 1:1 to 1:

2.

4. The method for preparing the MgO nanofluid coolant according to claim 1, characterized in that, In step (2), the magnetic stirring speed is 400-600 rpm and the magnetic stirring time is 10-30 min.

5. The method for preparing the MgO nanofluid coolant according to claim 1, characterized in that, In step (3), the ultrasonic power is 600-800W and the ultrasonic time is 90min-120min.

6. A MgO nanofluid coolant prepared by the preparation method according to any one of claims 1-5.

7. The MgO nanofluid coolant according to claim 6, characterized in that, Within a temperature range of 25℃ to 105℃, its thermal conductivity is between 0.4828 W / mK and 0.5311 W / mK, and its viscosity is between 1.5227 mPa.s and 4.0396 mPa.s.

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