JPS5999214A - Surface state evaluating method - Google Patents

Abstract

PURPOSE:To measure surface roughness and wettability at the same time by loading a discoid sample, and bringing one surface into contact with the surface of liquid, and rotating the sample and detecting torque as a funtion of the load. CONSTITUTION:The rotary measurement part consisting of the sample 7, sample holder 8, torque meter 9, output shaft 10, into shaft 11, and a motor 12 is balanced with the load 15, and while the sample 7 is brought into contact with the surface of the water 17 in a water tank 16, the measurement part is balanced again. The load 15 is adjusted to place a specific test load W on the rotary measurement part and the sample 7 is rotated by the motor 12 to read the fluid resistance between the sample 7 and water 17 on the torque meter 9 as torque T. The load W is varied and the measurement of torque W is repeated as the function of the W, measuring the surface roughness and wettability of the same 7 at the same time.

Description

[Detailed Description of the Invention] [Industrial Field of Application and Prior Art] The present invention relates to a surface condition evaluation method for simultaneously evaluating the surface condition of metals, plastics, ceramics, etc., particularly hydrophilicity and surface roughness. be.

Heat exchangers with plate fins, which are widely used in air conditioners, etc., are made of aluminum plate fins stacked at predetermined intervals, with steel pipes completely penetrating them, but in order to improve the heat exchange efficiency, It is necessary to reduce the ventilation resistance (wind pressure loss) of the airflow passing between the plate fins.

By the way, when the plate fin is used for cooling operation, water droplets adhere to the surface of the plate fin and wind pressure loss increases, so surface treatment is required to reduce this. There are two types of surface treatment methods: water-repellent treatment and hydrophilic treatment; the former makes water droplets form beads to make them slippery, and the latter makes them easier to run off.

However, in recent years, as the spacing between plate fins has tended to become smaller, more emphasis has been placed on hydrophilic treatment.

The surface condition evaluation method is a method for evaluating the degree of water repellency or hydrophilicity of the surface of a substance that has been subjected to water repellent surface treatment or hydrophilic surface treatment. Water repellency and hydrophilicity are two sides of the same coin; high water repellency means low hydrophilicity, and high hydrophilicity means low water repellency.

FIG. 1 shows a conventionally used general method for evaluating surface conditions, in which hydrophilicity (water repellency) is evaluated by measuring the contact angle θ of a water droplet 1 with respect to a surface 2. In this method, the contact angle θ is measured on a small part of the surface;
It is unreliable because the data varies over the entire surface. FIG. 2 shows another conventional surface condition evaluation method, in which the degree of hydrophilicity (pressure) of the sample 4 is evaluated by measuring 5 and recording 6 the pressure for dipping the sandals 4 in water 5. It's a method. This method has less variation in data and better reproducibility of sample data to the actual object than the method shown in Figure 1, but there are issues that need to be considered when applying this method to surface evaluation of plate fins for heat exchangers. There is.

[Object of the Invention] The wind pressure loss of a plate fin for a heat exchanger is determined by the degree of roughness and unevenness of its surface. If the wettability is increased by the hydrophilic surface treatment, the wind pressure loss will be reduced, but if the surface iJ becomes uneven due to the aging of the hydrophilic surface treatment, the wind pressure loss will increase. Therefore, in evaluating the surface condition of a plate fin for a heat exchanger, it is necessary to measure the surface irregularities (surface roughness) in addition to measuring the degree of hydrophilicity using the apparatus shown in FIG. The object of the present invention is to provide a surface condition evaluation method that can simultaneously measure the unevenness of the surface and the wettability.

[Structure of the Invention] The surface condition evaluation method of the present invention involves bringing one side of a disc-shaped sandal into contact with the surface of a liquid under a load, rotating the sample around its center, and measuring the torque required for the rotation. is measured each time the magnitude of the load is changed, and the surface state of the sample is evaluated from the relational expression between the torque and the load. This will be specifically explained below with reference to FIGS.

In FIG. 3, the output shaft 10 of a torque meter 9 is attached to the output shaft 7 whose surface condition is to be evaluated, and the input shaft 11 of the torque meter 9 is connected to the rotating shaft of a motor 12. The motor 12 has a load 15 at the opposite end of the fulcrum 14 via a cantilever 16 . 16 is an aquarium, and 17 is water. In the above configuration, first, the rotation measuring section (sample 7, sample holder 8, torque meter 9, output shaft 10, input shaft 1
1. Balance the motor 12) and the load 15, and then bring the sample 7 into contact with the surface of the water 17 of the water ta 16 to balance the load 15 again. After the setting is completed, the load 15 is adjusted to apply a predetermined test load W to the rotation measuring section, and the motor 12 is driven to measure the fluid resistance between the sample 7 and the water 17 from the scale 18 of the torque meter 9. Read as torque T. This operation is repeated for the same sandal while changing the load W, and the torque T is measured each time.

-5= Figure 4 shows W- measured for different samples α and b.
It shows the value of T, which can be expressed by the relational expression T=AW+B, and the surface condition can be evaluated from this relational expression. Now, the relational expression for sample α is Tα= AIZW
+ Bα, the relational expression for sample b is Th = AhH + B
b, when W=O, Aα〉hh, Bh=Tb>B
Since α=Tα, p, TA>Tα, it can be seen that sample α is more hydrophilic than sample b, and A(Z>AA
It can be seen that sample α has a higher resistance than sample B due to surface roughness.

The general findings obtained from the relationship between W and T will be explained with reference to FIG. The degree of hydrophilicity is essentially unaffected by the load W. If the unevenness of the surface is the same, the more hydrophilic the material, the greater the degree of water penetration into the unevenness and the larger the torque T. Therefore, the torque TO when W=O indicates the degree of hydrophilicity, and the larger TO is, the better the hydrophilicity is. On the other hand, the surface condition is affected by the load W. That is, if the degree of hydrophilicity is the same,
As the load W increases, the degree of water penetration into the unevenness of the optical surface increases, and the torque T increases accordingly. Comparing straight lines l and m in FIG. 5 shows that although they have the same hydrophilicity, m has a rougher surface than l. Comparing the tfC straight line m and le, the surface roughness is the same, but n is m
Yoshi also shows good hydrophilicity.

[Effects of the Invention] In order to confirm the effects of the present invention, the surface condition of aluminum plate fins for heat exchangers of air conditioners was compared and evaluated using the conventional method shown in FIG. 2 and the method of the present invention. The comparative evaluation method is as follows: hydrophilic surface treatment α, b
Surface evaluation was conducted on aluminum samples with and without aluminum immersion in water for 1 minute and left in the air for 9 minutes several times. We investigated the correlation with wind pressure loss during actual operation after repeated periods of time-stop operation. The results were as follows.

In the above table, ○, △, and × indicate that there is a good correlation between the sample test results and actual operation (○), there is a correlation (△), and there is no correlation at all ( ×)
It is.

As shown by the above experimental results, the method of the present invention is superior to the conventional method in that it can change data that correlates with actual operation. This means that the surface condition evaluation method of the present invention is T=A
In the relational expression of W×B, the torque T(l
This is because the conventional method focuses only on changes in 'fo' and determines the surface condition from TO and A.

As described above, the surface condition evaluation method of the present invention can obtain highly reliable data that correlates with actual operation, and therefore greatly contributes to the design of plate fins for heat exchangers, etc.

[Brief explanation of the drawing]

Figure 1: Explanation diagram of conventional surface condition evaluation method Figure 2: Explanation diagram of other conventional surface condition evaluation methods Figure 5N: Diagram explaining the principle of the present invention [Symbols] 7...Sample, 8...Sample holder, 9...Torque meter, 1o...Output shaft, 11...
・Input shaft, 12...Motor, 13...Cantilever, (
-114...Fully point, 15...Load, 16...Water tank, 17...Water, 18...Scale 9-

Claims (2)

[Claims] (1) One side of a disk-shaped sample is brought into contact with the surface of the liquid under a load, the sample is rotated around its center, and the torque required for the rotation is applied by changing the magnitude of the load. A surface state evaluation method characterized in that the surface state of the sample is evaluated from the relational expression between the torque and its load by measuring each time. (2) The hydrophilicity of the sample surface is evaluated from the torque value when the load in the relational expression between torque and its load is 00, and the roughness of the sample surface is evaluated from the differential coefficient of the relational expression. Surface condition evaluation method according to claim (1)