CN207946330U - Fluid Viscosity Test Device - Google Patents

Abstract

The utility model discloses a fluid viscosity testing device, wherein the testing device comprises a reference fluid box, a fluid box to be tested, a capillary, a valve, a measuring cylinder and a timer; the reference fluid box is used for injecting a reference fluid, and the fluid box to be tested The fluid box is used to inject the fluid to be measured; the capillary is connected to the lower end of the reference fluid box and the fluid box to be tested, the valve is arranged on the capillary, and the measuring cylinder is arranged at the outlet of the capillary; the timing The instrument is used to record the time when the reference fluid flows into the measuring cylinder through the capillary and the time when the fluid to be measured flows into the measuring cylinder through the capillary. In the process of viscosity testing, there are few to be measured. At the same time, the temperature control system can adjust the temperature of the fluid, which can meet the viscosity testing of fluids at different temperatures. It has the advantages of simple structure, convenient and fast operation, and accurate test results. It is suitable for Measure the Newtonian fluid whose solution viscosity is less than 1200cP.

Description

Fluid Viscosity Test Device

technical field

The utility model relates to the technical field of testing, in particular to a testing device and method for fluid viscosity.

Background technique

Viscosity is one of the basic physical parameters of fluids, and it has an important influence on the production process or production links of many industries (such as chemical industry, medicine, food and metallurgy, etc.). actual value. At present, based on different measurement principles, many methods that can be used for viscosity measurement have been widely proposed, such as capillary method, falling ball method, vibration method, plate method, rotation method and gravity method, etc. Some of these viscometers have been gradually commercialized. However, these traditional viscosity measurement methods have problems such as complex structure, high cost, and inability to change the temperature of the fluid to be measured in real time. In order to meet the viscosity measurement of fluids at different temperatures, the temperature control method used by the existing viscosity tester is to place the sample cup in a water bath, and then use the temperature probe to test the temperature. Using this method not only makes the experimental steps complicated , the temperature of the fluid after removing the water bath will also produce a large error, resulting in a larger error in the final test result.

Contents of the invention

The technical problem to be solved by the utility model is to provide a fluid viscosity testing device and method for the above-mentioned deficiencies in the prior art, to realize the temperature control of the fluid to be tested, and to measure the Newtonian fluid quickly, efficiently and accurately. viscosity.

In order to solve the above problems, the technical solution adopted in the utility model is:

A testing device for fluid viscosity, characterized in that it includes a reference fluid box, a fluid box to be tested, a capillary, a valve, a measuring cylinder, and a timer; the reference fluid box is used for injecting reference fluid, and the fluid box to be tested is used for Inject the fluid to be tested; the capillary is connected to the lower end of the reference fluid box and the fluid box to be tested, the valve is arranged on the capillary, and the graduated cylinder is set at the outlet of the capillary; the timer is used to record the reference The time for the fluid to flow into the measuring cylinder through the capillary and the time for the fluid to be measured to flow into the measuring cylinder through the capillary.

The diameter of the capillary is 0.5mm-2.0mm, and the specific size depends on the viscosity of the Newtonian fluid, and the viscosity of the Newtonian fluid does not exceed 1200cP.

It also includes a temperature control system for heating the reference fluid box and the fluid box to be tested, and a temperature sensor for monitoring the temperature of the fluid in the capillary.

The temperature control system includes a refrigerating sheet, a voltage stabilizing source, and a positive and negative switching switch; the refrigerating sheet is arranged in the walls of the reference fluid box and the fluid box to be tested; The negative switching switch is connected to the refrigerating sheet, and the refrigerating sheet is controlled by the positive and negative switches to heat or cool the fluid.

Fins are arranged on the walls of the reference fluid box and the fluid box to be tested.

The temperature sensor is a thermocouple.

A method for measuring fluid viscosity, characterized in that: using a standard fluid whose viscosity and density are known at various temperatures as a reference fluid, the time item and the density of the fluid to be measured are measured through experiments, and the fluid to be tested is calculated according to the formula Viscosity, viscosity testing steps include:

Injecting the reference fluid and the fluid to be tested into the reference fluid tank and the fluid tank to be tested respectively;

Simultaneous heating or cooling of the reference fluid and the fluid to be measured;

Monitor the temperature of the reference fluid and the fluid to be tested; when the reference fluid and the fluid to be tested reach the required temperature, open the capillary valves of the reference fluid box and the fluid box to be tested at the same time to obtain the time taken for the reference fluid to flow out of the same volume V t ₁ and the time t ₂ used by the fluid to be tested;

Weigh the graduated cylinder, the mass is m ₁ , weigh the graduated cylinder with the fluid volume V, the mass is m ₂ , and calculate the density ρ ₂ of the fluid to be measured according to ρ=(m ₂ -m ₁ )/V ;

according to Calculate the viscosity of the fluid to be measured, where μ ₁ is the viscosity of the reference fluid; μ ₂ is the viscosity of the fluid to be measured; ρ ₁ is the density of the reference fluid.

The simplified test device and method for fluid viscosity of the utility model is different from the traditional viscosity test theory, which is derived based on the loss along the laminar flow in the capillary. The principle of the method is that the fluid in two devices with the same volume moves along the When the capillary with the same diameter flows out the fluid with the same volume V (V can be taken as 20ml-40ml), the pressure loss is basically the same. From the loss along the laminar flow in the capillary and the Bernoulli equation, it can be deduced that the viscosity ratio is equal to the density of the two fluids and The ratio of the product of time.

Beneficial effect

The utility model relates to a simplified test device and method for fluid viscosity, in order to complete the measurement of the fluid viscosity under the conditions of different temperatures required to test Newtonian fluid. The materials used in the whole device and the preparation process are very simple, and the operability of transfer and utilization is very strong. In addition, the amount of sample required in the test process is small, and the test time is short. The process of analysis and calculation is relatively simple, and the final test result is accurate. The error is relatively small, and it is suitable for measuring Newtonian fluids whose solution viscosity is less than 1200cP.

Description of drawings

Figure 1 is a simple viscosity testing device.

Figure 2 shows the liquid level observation device.

Figure 3 is a diagram of capillary force analysis.

In the figure: 1-positive and negative switching switch; 2-stabilized voltage source; 3-fin; 4-liquid level observation port; 5-fluid inlet; 6-fluid outlet; 7-refrigerating plate; 8-reference fluid tank; 9-fluid box to be tested; 10-thermocouple; 11-valve; 12-graduating cylinder; 13-partition; 14-capillary;

Detailed ways

Preferred examples of the present utility model are described in further detail below in conjunction with accompanying drawings, so that advantages and features of the present utility model can be more easily understood by those skilled in the art:

As shown in Figure 1, a fluid viscosity testing device includes a viscosity testing system and a temperature control system. The viscosity testing system includes a reference fluid box 8, a fluid box to be tested 9, a capillary 14, a valve 11, a measuring cylinder 12 and a timer. The temperature control system includes a cooling plate 7 , a voltage stabilizing source 2 , fins 3 , a switch 1 for positive and negative poles, and a thermocouple 10 . In the temperature control system, the temperature of the fluid is raised (lowered) by the refrigerating plate 7 .

The reference fluid box 8 is arranged symmetrically with the fluid box 9 to be tested, separated by a partition, and the cooling plate 7 is embedded in the wall of the box to provide a heat source (cold source) for heating (cooling) of the fluid. The fins 3 are evenly arranged on the wall of the reference fluid box 8 and the fluid box 9 to be tested, and the energy of the side of the cooling fin 7 that cannot provide heat (cold) for the fluid is dissipated in time to ensure that the temperature of the side close to the fluid layer is sufficient High or low enough, while avoiding excessively high or low cabinet temperatures. The upper ends of the reference fluid box 8 and the fluid box 9 to be tested are all provided with a fluid inlet 5, and the lower ends are all provided with a fluid outlet 6, which facilitates the injection and discharge of the fluid and the cleaning of the box body. In order to make the volume of fluid used in each test the same, the box There is also a liquid level observation device at the upper end of the external wall.

Viscosity testing system based on derived formula The viscosity and density of the reference fluid are known at each temperature. Use the temperature control system to regulate the temperature of the fluid, open the valve 11, the fluid flows into the measuring cylinder 12 from the capillary 14, observe the volume of the solution in the measuring cylinder 12, when the specified volume is reached, record the time t ₁ used by the reference fluid and the fluid to be measured respectively ,t ₂ , taking the average value of multiple tests. Weigh the clean graduated cylinder, the mass is m ₁ , weigh the graduated cylinder with the fluid volume V, the mass is m ₂ , and the density of the fluid to be tested can be calculated according to ρ=(m ₂ -m ₁ )/V ;

The heating or cooling of the fluid by the refrigerating sheet is controlled by the positive and negative switches. After the positive and negative electrodes are switched, the heating sheet and the cold end of the refrigerating sheet will also be switched accordingly, and the heating (or cooling) of the refrigerating sheet The temperature can be regulated by a stabilized voltage source, and the fluid temperature in the fluid box is monitored in real time by a thermocouple.

The fins are evenly arranged on the wall of the fluid box. When the side of the cooling plate close to the fluid is used as the cooling end, the other side is the heating end. If the temperature is too high, the cooling plate will be damaged, and it will also affect the temperature of the cooling end. The use of fins increases the heat dissipation area of the fluid box wall, which can improve heat exchange efficiency, avoid affecting the structure of the cooling plate and the temperature of the cooling end, and at the same time avoid excessive temperature of the fluid box wall. Conversely, when the side of the cooling fin close to the fluid is the heating end, the other side is the cooling end, and the presence of the fins can prevent the temperature of the wall surface of the fluid box from being too low.

The liquid level observation device is a transparent device with a U-shaped tube structure, which are respectively arranged at the same position on the wall surface of the reference fluid tank and the fluid tank to be measured. The liquid level of the fluid in the tank can be judged by the position of the fluid in the U-shaped tube.

The diameter of the capillary is between 0.5mm-2.0mm. The specific size depends on the viscosity of the Newtonian fluid. The viscosity of the Newtonian fluid does not exceed 1200cP. When the viscosity is high, choose a larger tube diameter, and refer to Table 2 for capillary selection. Its material can be metal, alloy, polymer compound or composite material.

Table 2

Capillary diameter mm Dynamic viscosity test range cP 0.6 2-16 0.8 7-35 1 20-100 1.2 50-200 1.5 100-500 2 300-1200

The test method of fluid viscosity of the present utility model, the steps are:

Firstly close the outlet valves of the reference fluid box 8 and the fluid box to be tested 9, inject the standard fluid used into the reference fluid box from the inlet 5 of the fluid box, and inject the fluid to be tested into the fluid box to be tested. According to the temperature required by the fluid to be tested, turn on the positive and negative switching switch 1 and the voltage regulator 2, and determine whether the cooling plate will heat or cool the fluid through the positive and negative switching switch. Using the voltage regulator to adjust the voltage can control the fluid The temperature is regulated, and the temperature of the fluid is monitored by a thermocouple 10 arranged beside the entrance of the capillary 14 . When the temperature displayed by the thermocouple reaches the required temperature of the fluid to be measured, open the valve 11 and the timer at the capillary of the reference fluid and the fluid to be measured at the same time, observe the volume of the fluid flowing into the measuring cylinder 12, when the required volume is reached (generally 20ml-40ml) , use a timer to record the time it takes for the two fluids to flow out of the same volume, then use an electronic scale to measure the weight of the fluid to be tested, and calculate the density of the fluid to be tested according to ρ=m/V. Since the viscosity and density of the reference fluid at each temperature are standard known quantities, finally according to the derivation formula Calculate the viscosity of the fluid to be measured.

Since the diameter of the capillary and the average flow velocity in the tube are small, according to the expression of Reynolds number, the flow of Newtonian fluid in the capillary belongs to the laminar flow in the circular tube. In addition, the diameter of the capillary is uniform, and the shape and size of the section remain unchanged. The laminar flow in the pipe conforms to the characteristics of uniform flow, so only the loss along the path is considered, and the local loss is not considered.

First, take a vertical capillary for stress analysis, as shown in Figure 3, the diameter of the capillary is d, and a cylindrical element with a length of l and a radius of r is taken inside the capillary, and the fluid flows along the x direction. In this flow direction, the acting forces on the microelements are:

Gravity: ρgπr ² cosα

End face pressure: p ₁ πr ² , p ₂ πr ²

Pipe wall shear force: τ·l·2πr

Among them, p ₁ , p ₂ - the pressure at the same selected point on the upper and lower sections of the capillary section; τ - the shear stress on the side of the micro-element body, the direction is opposite to the flow direction of the fluid; r - the radius of the micro-element circular tube; The pipe sections are arranged vertically, so cosα=1.

The flow of the fluid in the capillary belongs to the uniform flow. The fluid particles move at a constant speed along the x direction, and the fluid velocity only changes along the r direction, as shown in the figure. Therefore, the resultant force on the cylindrical micro-elements along the x direction is zero. Considering the direction of action of each force, the balance equation is obtained

p ₁ πr ² -p ₂ πr ² +ρgπr ² lcosα-τl2πr＝0 (1)

Newton's law of internal friction Substituting into formula (1) and simplifying, we can get

Since the length and diameter of the two capillaries are basically the same, the value of Δp+ρgl does not change with the change of r during the fluid flow process. The above formula is integrated and brought into the boundary conditions: when r=R, the velocity u=0, have to

Wherein, Δp=p ₁ -p ₂ ; R is the capillary radius. Due to the viscous resistance of Newtonian fluid, energy loss occurs in the process of fluid flow, and the energy equation between the capillary segments is established as:

In the capillary, the fluid flow conforms to the characteristics of uniform flow, that is, α ₁ v ₁ ² /2g=α ₂ v ₂ ² /2g, h _l =h _f .

Substituting into the above formula, we can get

Simultaneous formula (3) and formula (5), sorted out

In the formula, Z ₁ , Z ₂ - the height of any point on the upper and lower end surfaces of the capillary section taken relative to the capillary outlet; α ₁ , α ₂ - the kinetic energy correction coefficients of the upper and lower end surfaces of the capillary section taken, when the flow velocity in the capillary tube is uniformly distributed , α=1; v ₁ , v ₂ —average velocity of the upper and lower ends of the capillary section; h _l1 -2—average unit energy loss between the capillary sections; h _f —head loss along the way.

Therefore, it can be concluded that for the fluid flowing in a uniform laminar flow in the capillary, the flow velocity on the effective section of the capillary is distributed in a parabolic law. When r=0, that is, on the tube axis, the maximum velocity is reached

Substituting formula (6) into the definition formula of average velocity

The average flow rate is

According to formula (8), we get

Q _v is the flow rate of the fluid flowing through the capillary, A is the cross-sectional area of the capillary, d is the diameter of the capillary, λ is the drag coefficient along the way, and the theoretical value is λ=64μ/ρvd. Simultaneous formula (9) and formula (5), get

In the process of testing the viscosity of the fluid, the device used for the reference fluid and the experimental fluid is the same, that is, the height of the capillary inlet and outlet is basically consistent with the pressure, indicating that Δp ₁ + ρ ₁ gl = Δp ₂ + ρ ₂ gl, let Δp = Δp+ ρgl, then

And because the capillary length is the same as the tube diameter, when the same volume of fluid flows out, v ₁ /v ₂ ≈t ₂ /t ₁ , where v ₁ and v ₂ are the speeds of the reference fluid and the fluid to be measured flowing out of the capillary, respectively. Organized and available

Fig. 2 is a liquid level observation device, which is a transparent device with a U-shaped tube structure. It is installed at the same position on the wall surface of the reference fluid tank and the fluid tank to be measured, and there is a scale line 15 at the same position on the side of the tube for Make sure the tank has the same volume of fluid.

In order to prove the feasibility of a kind of fluid viscosity testing device and method of the present invention, pure water is used as the standard fluid, 99% ethanol solution and 2% PVA solution are used as the fluid to be tested, and the density and viscosity of these three fluids are the same. is known. Assuming that the viscosity of 99% ethanol solution and 2% PVA solution is unknown, the temperature of the reference fluid and the fluid to be tested is controlled at 20°C by the viscosity testing device, and then the fluid is tested for many times, and when the fluid of the same volume V flows out, The time t consumed is then averaged to finally calculate the viscosity of 99% ethanol solution and 2% PVA solution, which is compared with the standard viscosity, as shown in Table 1:

Table 1

The results show that the error can be controlled within a small range, and the verification of the viscosity testing device is completed.

Claims (6)

1. a kind of test device of fluid viscosity, it is characterised in that：Including reference fluid case, fluid to be measured case, capillary, valve Door, graduated cylinder and timer；The reference fluid case waits for flow measurement for injecting reference fluid, the fluid to be measured case for injecting Body；The capillary is connected to the reference fluid case and fluid to be measured case lower end, and the valve is arranged on the capillary, In the outlet of the capillary, the graduated cylinder is set；The timer flows into graduated cylinder for recording reference fluid through the capillary Time and fluid to be measured through the capillary flow into graduated cylinder time.

2. the test device of fluid viscosity according to claim 1, it is characterised in that：The capillary caliber is 0.5mm- 2.0mm, depending on the viscosity of specific scale visual Newtonian fluid, the viscosity of Newtonian fluid is no more than 1200cP.

3. the test device of fluid viscosity according to claim 2, it is characterised in that：Further include for heating the reference The temperature sensor of fluid temperature (F.T.) in the temperature control system and the monitoring capillary of fluid tank and fluid to be measured case.

4. the test device of fluid viscosity according to claim 3, it is characterised in that：The temperature control system includes refrigeration Piece, source of stable pressure and positive and negative anodes switching switch；The babinet in the reference fluid case and fluid to be measured case is arranged in the cooling piece In wall surface；The source of stable pressure is connect through positive and negative anodes switching switch with the cooling piece, is switched and is carried out by the positive and negative anodes Control cooling piece is heated or is cooled down to fluid.

5. the test device of fluid viscosity according to claim 3, it is characterised in that：In the reference fluid case and to be measured It is provided with fin on fluid tank wall surface.

6. the test device of fluid viscosity according to claim 5, it is characterised in that：The temperature sensor is thermoelectricity It is even.