Device for measuring heat conductivity coefficient of visual nano cooling liquid

Abstract

The utility model discloses a heat conductivity coefficient measuring device of visual nano cooling liquid, and belongs to the technical field of measurement of thermal physicochemical property parameters of nano fluid. According to the measuring device disclosed by the utility model, the stable dispersion state of the liquid in the hot wire body is observed and measured in real time by adopting the data acquisition system, measurement errors caused by dispersion stability are reduced, accurate test data are directly read from the data acquisition system after measurement is finished, and the whole measuring process is convenient and rapid and high in precision.

Description

TECHNICAL FIELD

[0001] The utility model belongs to nanometer fluid thermophysical chemical property parameter measurement technical field relates to a kind of visual nanometer coolant's thermal conductivity measuring device. BACKGROUND

[0002] Nanometer refrigerant is nanometer fluid with refrigerant as base fluid, that is, suspension formed by dispersing nanometer metal or non-metal particles into refrigerant. Due to small volume, large specific surface area and high thermal conductivity of nanometer particles, nanometer refrigerant has excellent heat transfer performance. Studies have shown that nanometer refrigerant can improve thermal conductivity and heat transfer performance. Dispersion stability of nanometer refrigerant is an important evaluation index. In addition to stability in preparation process, stability in performance test and actual application of nanometer refrigerant should also be considered. Currently, methods for measuring thermal conductivity of nanometer refrigerant include flat plate method, concentric cylinder method, transient hot wire method and transient hot needle method. Flat plate method and concentric cylinder method both belong to steady-state method. In order to avoid occurrence of natural convection, both methods require high processing accuracy of device. Transient hot wire method is currently the most accurate method for measuring thermal conductivity of liquid at home and abroad. Transient hot needle method replaces hot wire with hot needle, which improves stability of hot wire, but has lower accuracy.

[0003] In existing thermal conductivity measuring device, stable dispersion state of nanometer refrigerant to be measured cannot be directly observed during thermal conductivity measurement, which affects measurement accuracy. UTILITY MODEL CONTENT

[0004] The utility model aims at providing a kind of visual nanometer coolant's thermal conductivity measuring device, to solve the technical problem that stable dispersion state of nanometer refrigerant to be measured cannot be directly observed in existing measuring device, which affects measurement accuracy.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] The utility model discloses a kind of visual nanometer coolant's thermal conductivity measuring device, including data acquisition system and hot wire body;The hot wire body includes hot wire, fixed support, working cavity and thermostat tank;One end of the working cavity is inserted into thermostat tank;Two ends of the hot wire are fixed on fixed support, and middle is inserted into working cavity;

[0007] Two ends of the hot wire fixed in fixed support are provided with lead-out wire, and the data acquisition system is connected with both ends of the lead-out wire of hot wire.

[0008] Further, the data acquisition system includes first multimeter, second multimeter, direct current power supply, standard resistance and switch;The direct current power supply, switch, standard resistance and lead-out wire of hot wire are connected in series;The switch is connected with industrial computer.

[0009] The first and second multimeters are connected with the industrial computer through a USB bus; the first multimeter is connected with both ends of a standard resistance; and the second multimeter is connected with both ends of a hot wire lead.

[0010] Further, the hot wire is a nickel wire.

[0011] Further, the nickel wire is connected with the fixing support through a nickel rod.

[0012] Further, the nickel wire is connected with the nickel rod through spot welding.

[0013] Further, the diameter of the nickel wire is 50-55 μm; and the diameter of the nickel rod is 1-1.1 mm.

[0014] Further, the working cavity is quartz glass.

[0015] Further, one end of the working cavity has a gap with the bottom of the constant-temperature tank; and a thermocouple is arranged in the constant-temperature tank.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] The utility model discloses a visual nanometer cooling liquid's heat conductivity coefficient measuring device adopts data acquisition system real -time observation measurement hot line body in the stable dispersion state of liquid, reduces the measurement error due to dispersion stability, after measurement, directly reads accurate test data from data acquisition system, whole measurement process is convenient and fast, and the precision is high.

[0018] Further, the temperature of the cooling liquid is measured through the thermocouple, so that the constant-temperature requirement of the measurement process is ensured; KEI7100 switch control is used, so that the voltage difference data collection is started at the same time of switch conversion, and the time difference error caused by manual switch is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. 1 is a whole structure schematic view of the present application;

[0020] Wherein: 1-data acquisition system; 2-hot wire; 3-fixing support; 4-quartz glass; 5-constant-temperature tank; 6-thermocouple; A, B: standard resistance two end measuring points; C, D: hot wire two end measuring points. DETAILED DESCRIPTION

[0021] In order to make the person skilled in the art better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0022] It should be noted that the terms "first", "second" and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0023] The present application will be described in further detail below in conjunction with the drawings:

[0024] Referring to Figure 1 The present application discloses a kind of visualization nanometer cooling fluid's thermal conductivity measuring device, it can be used for the measurement of thermal conductivity of most organic liquid and other non-conductive liquid under normal pressure, mainly comprising data acquisition system 1 and hot wire body composition;The hot wire body in it is mainly composed of hot wire 2, fixed support 3, working cavity and thermostat 5.

[0025] The present application discloses a kind of visualization nanometer cooling fluid's thermal conductivity measuring device, the core component of thermal conductivity measurement is hot wire 2 and fixed support 3, hot wire 2 adopts nickel wire with diameter 50 ~ 55 μm, is welded to 1 ~ 1.1 mm thick nickel rod after straightening, nickel wire and nickel rod are connected using spot welding, then fixedly connected with fixed support 3;Among them, nickel rod and nickel wire have the same thermal expansion coefficient, when temperature changes, nickel wire is always in tension state;The working cavity of hot wire is transparent quartz glass 4 due to the need of observing the dispersion stability of nanometer cooling fluid, it is convenient to observe the working state of nanometer cooling fluid.

[0026] The utility model discloses a visual nanometer cooling liquid's heat conductivity coefficient measuring device, data acquisition system 1 adopts two multimeters of Keysight 34470A and Keysight 34461A, is connected to industrial computer through USB bus, can realize the automation of collection very well, 34470A is used to measure the voltage of standard resistance both ends, can obtain the current through hot wire 2, 34461A directly measures the voltage of hot wire 2 both ends,

[0027] Wherein, the role of resistance box is to stabilize the voltage in the circuit, ensure the stability of power supply voltage, DC voltage source adopts Agilent E3610A DC power supply, provides more stable voltage for the circuit.

[0028] The circuit measurement principle of the above data acquisition system 1 is as follows:

[0029] A, B, C, D four points access data acquisition system, the voltage of hot wire 2 both ends is measured as U1, the voltage of standard resistance both ends U2 during the experiment process;

[0030] The voltage U1 of hot wire 2 both ends is as follows:

[0031] U 1= V C - V D ;

[0032] Wherein, the subscript represents different analog input channels, V represents the potential of corresponding channel;

[0033] Similarly, the voltage U2 of standard resistance both ends is as follows:

[0034] U 2= V A - V B ;

[0035] The current I of series circuit is obtained by calculation, and the resistance R of hot wire 2 w The size of the line power q of hot wire is as follows:

[0036] ;

[0037] ;

[0038] ;

[0039] Wherein, R is the resistance of standard resistance, unit is Ω, L is the length of the heating wire 2, unit is m.

[0040] The power is disconnected before the experiment, and the current needs to be applied to the heating wire 2 through the switch. Due to the action of the pulse current, the temperature of the heating wire 2 and the surrounding medium rises, and the resistance of the heating wire 2 changes. The temperature of the heating wire 2 at this time can be inversely solved according to the resistance-temperature relationship of the heating wire 2 calibrated before the experiment.

[0041] The resistance-temperature relationship of the heating wire 2 is:

[0042] ;

[0043] When the resistance of the heating wire 2 is R w , the positive solution of the quadratic equation is calculated, and the temperature of the heating wire is:

[0044] ;

[0045] Wherein: a, b and c are constants, and T is the temperature of the heating wire 2.

[0046] In order to obtain the slope of the ΔT~lnt graph, the temperature of the first data point is selected as the initial temperature T0, the temperature rise of each subsequent data point is obtained, and the slope A of the ΔT~lnt curve is fitted by using the program, so that the final solving formula of the thermal conductivity coefficient is obtained:

[0047]

[0048] Labview programming is adopted to convert the multimeter signal into data, and the liquid thermal conductivity coefficient is obtained through calculation.

[0049] The measurement steps of the visual nanometer cooling liquid thermal conductivity measurement device are as follows:

[0050] Turn on the computer and the power supply, and preheat the device. Then wash the working cavity with the to-be-measured liquid three times, then install about 50mL of to-be-measured liquid, put the working cavity into the constant temperature tank 5 and ensure that the main part of the working cavity is completely immersed below the liquid level of the constant temperature tank 5, connect the nickel wire resistance lead-out wire to the data acquisition system 1, and tightly cover the tank cover of the constant temperature tank 5 to ensure that the temperature field in the constant temperature tank 5 is more stable.

[0051] Adjust the temperature of the constant temperature tank 5 to the predetermined value, control the temperature through the thermocouple 6, and continue to keep the temperature constant for about 20min after the temperature thermocouple 6 is stable, so that the temperature distribution in the constant temperature tank 5 is more uniform.

[0052] Open the LabVIEW data acquisition operation panel on the computer, adjust the voltage range of the multimeter, adjust the power supply, apply a constant voltage to the circuit, stabilize for 5 minutes, click the start acquisition button on the panel, clear the chart, close the Keithley 7001 switch, wait for 2-3 seconds, then open the switch, stop acquisition, click the panel to close the acquisition button;

[0053] The tedx file is obtained from LabVIEW, the effective temperature rise section is selected, after selection, it is put into MATLAB for data processing, the slope is obtained, and the thermal conductivity of the coolant is finally calculated;

[0054] Repeat the experiment, repeat steps 4-7, and perform 5 sets of repeated experiments to obtain the average value of the thermal conductivity.

[0055] Example 1

[0056] In this embodiment, the thermal conductivity measurement device for visualized nanometer coolant is used to measure the thermal conductivity of deionized water / absolute ethanol / pure R141b, and the thermal conductivity of the three substances at different temperatures is measured. Each temperature is measured five times, and the average value of the five results is taken. The experimental results are compared with the thermal conductivity calculated by Refprop10.0, and the data obtained is shown in Tables 1-3. It can be seen that the deviation of deionized water is within 1.55%, the deviation of absolute ethanol is within 1.12%, and the deviation of pure R141b is within 1%. The experimental results show that the hot-wire transient thermal conductivity experimental system is accurate and reliable, and achieves the expected experimental precision. The device can be used for measuring the thermal conductivity of nanometer coolant.

[0057] Table 1: Comparison of experimental and calculated values of thermal conductivity of pure water at different temperatures

[0058]

[0059] Table 2: Comparison of experimental and calculated values of thermal conductivity of absolute ethanol at different temperatures

[0060]

[0061] Table 3: Comparison of experimental and calculated values of thermal conductivity of R141b at different temperatures

[0062]

[0063] The thermal conductivity of the nano-cooling liquid Al2O3 / R141b is measured, and the thermal conductivities of the nano-cooling liquid with mass fractions of 0.1%, 0.2% and 0.3% are measured at temperatures of 10℃, 15℃, 20℃, 25℃ and 30℃. The thermal conductivities are measured at least 5 times at each temperature, and the average value of the experimental results is taken and compared with the thermal conductivity of pure R141b to calculate the thermal conductivity improvement value k eff / k f As shown in Table 4. The results show that at the same concentration, with the increase of temperature, the thermal conductivity of the Al2O3 / R141b nano-cooling liquid is improved; at the same temperature, with the increase of concentration, the thermal conductivity of the Al2O3 / R141b nano-cooling liquid is improved.

[0064] Table 4: Thermal conductivity experimental values of the nano-fluid at different temperatures and different concentrations

[0065]

[0066] The above content only illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made on the basis of the technical scheme according to the technical idea of the present application falls within the protection scope of the claims of the present application.

Claims

1. A device for measuring the thermal conductivity of a visualized nano-coolant, characterized in that: The invention comprises a data acquisition system (1) and a hot wire body; the hot wire body comprises a hot wire (2), a fixed bracket (3), a working cavity and a constant temperature bath (5); one end of the working cavity extends into the constant temperature bath (5); both ends of the hot wire (2) are fixed on the fixed bracket (3), and the middle portion extends into the working cavity; The hot wire (2) is fixed to a fixed bracket (3) and is provided with lead wires at both ends. The data acquisition system is connected to both ends of the lead wires of the hot wire (2).

2. The device for measuring thermal conductivity of a visualized nano-coolant according to claim 1, characterized in that: The data acquisition system (1) comprises a first multimeter, a second multimeter, a DC power supply, a standard resistor and a switch; the DC power supply, the switch, the standard resistor and the lead wires of the hot wire (2) are connected in series in sequence; the switch is connected to an industrial computer; The first multimeter and the second multimeter are connected to the industrial computer via a USB bus; the first multimeter is connected to both ends of a standard resistor; and the second multimeter is connected to both ends of a lead wire of the hot wire (2).

3. The device for measuring thermal conductivity of a visualized nano-coolant according to claim 1, characterized in that: The heating wire (2) is a nickel wire.

4. The device for measuring thermal conductivity of a visualized nano-coolant according to claim 3, characterized in that: The nickel wire is connected to the fixed bracket (3) via a nickel rod.

5. The device for measuring thermal conductivity of a visualized nano-coolant according to claim 4, characterized in that: The nickel wire and the nickel rod are connected by spot welding.

6. The device for measuring thermal conductivity of a visualized nano-coolant according to claim 4, characterized in that: The diameter of the nickel wire is 50-55 μm; the diameter of the nickel rod is 1-1.1 mm.

7. The device for measuring thermal conductivity of a visualized nano-coolant according to claim 4, characterized in that: The working cavity is made of quartz glass (4).

8. The device for measuring thermal conductivity of a visualized nano-coolant according to claim 1, characterized in that: There is a gap between one end of the working cavity and the bottom of the constant temperature bath (5); a thermocouple (6) is provided in the constant temperature bath (5).

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