JPH0233087B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to an experimental device for simulating ice-breaking and structural icing disasters using scale models of icebreakers, polar ships, polar offshore structures, etc. This invention relates to a method for producing a simulated ice sea for forming an ice layer.

[Conventional technology]

For polar offshore structures such as icebreakers, polar ships, or oil platforms, scale models are created at the design stage.
We conducted a simulation experiment using an ice layer that simulated an actual ice sea.
We are conducting tests on ship shape and structural durability under various conditions.

One example of such experimental equipment is one in which a large cooling coil is installed on the ceiling of a test chamber in which a water tank is placed, and the entire test chamber is cooled by natural convection.

However, the following problems arose in the means for cooling and freezing water in the test chamber and aquarium.

(1) The freezing rate of ice in the tank is slow, and one experiment cycle is long, making it impossible to conduct many experiments.

(2) The ice quality of the ice layer is not good.

(3) Avatars appear on the ice surface.

(4) Accurate experimental results cannot be expected because there are many deviations in the ice thickness at the end of freezing, and the ice thickness varies depending on the location in the tank.

[Problem that the invention seeks to solve]

In order to solve the above-mentioned problems, the present invention increases the rate of freezing by forcibly feeding sub-zero low temperature air into the test chamber, changing the blowing direction every required time, and furthermore, the ice layer is removed from the spray nozzle. Ice crystal nuclei, which are made by instantaneously freezing the fog, are evenly distributed in the water tank to promote uniform ice layer growth.

[Means for solving problems]

Therefore, the method for producing a simulated ice sea of the present invention rapidly cools the test chamber by blowing sub-zero cold air at high speed along the surface of the water in the test chamber, which is equipped with a water tank. Thin ice is formed on the surface of the water, then the air blowing into the test chamber is temporarily stopped, the thin water with uneven strength generated by rapid cooling is appropriately removed, and then water is sprayed into the test chamber in the form of a mist. The ice crystal nuclei that instantly freeze the fog are then lowered to uniformly spread the ice crystal nuclei on the surface of the water in the aquarium, and then the low-temperature cold air is directed along the ice layer, and the airflow is The ice layer is characterized by being able to generate an ice layer with an even thickness by blowing air so as to create an alternating air flow in which the direction of flow is reversed every required time.

[Effect]

Before creating the experimental ice layer, the inside of the test chamber is rapidly cooled, which forms thin ice on the surface of the water, but because this thin ice forms rapidly, it is uneven in thickness and strength.

Once this thin ice is removed, the ice crystal nuclei are quietly and evenly scattered on the water surface, and then an alternating air current is sent to the water surface to grow the ice, creating a simulated ice sea with uniform thickness and strength for experiments. is formed.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to a specific example shown in the accompanying drawings.

In FIG. 1, a water tank 3 containing water 4 is provided at the bottom of a test chamber 2 constituted by a heat-insulating structure chamber body 1. In addition, on the left and right sides of the test chamber, there are a pair of left and right cold air supply devices 1, each consisting of ducts 13a and 13b whose upper ends are connected to chambers 12a and 12b, and whose lower ends have cold air inlets and outlets 11a and 11b.
4a and 14b are provided, and the cold air inlet/outlet 11
The openings a and 11b are slanted and opened so that cold air is blown out along the surface of the water in the aquarium.

Further, a large number of spray nozzles 5 for spraying water are provided in the upper part of the test chamber, and water from a water sprinkler 8 is force-fed to each nozzle 5 through a water spray pipe 6.

Furthermore, rails 10a and 10b are laid on the left and right sides of the water tank 3, and a carrier 28 that can be moved in the longitudinal direction of the test chamber 2 so as to straddle the water tank 3 is provided on the rails 10a and 10b. At the bottom of the carrier 28, there is a rod 27 with a mock ship 25 for experiments that can be moved by breaking the ice 26 in the water tank 3.
It is attached by.

On the other hand, outside the test chamber 2, a cold air generator 20 is provided in which a blower 16, a heater 17, and a refrigerant coil 19 to which a refrigerant is supplied from a refrigerator 18 through a refrigerant pipe 7 are arranged. Inlet 1
A blower duct 22 is connected to a cold air outlet 15a that cools and blows out the air sucked in from the air outlet 5, and branch ducts 22a and 22b each having dampers 21a and 21b are connected to the same duct, and each branch duct supplies cold air. Chamber chambers 12a, 12b
are connected to each. Therefore, from the chambers 12a and 12b, there are dampers 23a and 23b, respectively.
A return duct 24a, 24b having a diameter is connected to the intake port 15b of the cold air generator 20.

To generate an alternating cold air flow with the device described above,
First, the air sucked from the intake port 15b of the cold air generator 20 is cooled by the cooling coil 19, and then passed through the air ducts 22a, 22b to each chamber 12a, 12b.
Send to. Here, dampers 21b and 23b are opened,
By closing the dampers 21a and 23a, the cold air flows in the direction of the solid arrow, is sent to the chamber 12a, and is blown out onto the water surface of the freezing water tank 3 from the cold air inlet/outlet 11a.

This air is absorbed by the cold air inlet/outlet 11b and returned to the cold air generator 20 through the return duct 24b.

Also, in order to reverse the direction of the cold air, the damper 21
By opening a, 23a and closing dampers 21b, 23b, the flow of cold air is reversed, and the cold air flows in the direction of the dashed arrow from the cold air inlet/outlet 11b to the inlet/outlet 11a.

The reason for using alternating airflow here is that the heat transfer on the downstream side of the airflow decreases, so if the airflow flows in the same direction, the ice layer will be thinner on the downstream side, and the ice layer will be thinner on the upstream and downstream sides. This is to correct the deviation in thickness that occurs.

Next, a method for forming an ice layer on the water surface used in the experiment will be explained with reference to FIGS. 3 and 4.

[Process] First, the test chamber is rapidly cooled from +2°C to -10°C using high-speed wind (0.5 to 1.0 m/sec). As a result, thin ice 26a having a thickness of about 1 to 2 mm is formed on the entire surface of the water (FIG. 3a).

Once the ice has cooled down to -10°C, the cold air supply is temporarily stopped and all thin ice is removed using a scraper or the like.
This is because the ice crystals are large, so only the surface becomes strong and uneven ice [Part 3]
Figure b].

Next, from point S, the water sprinkler 8 is operated in a calm state with a wind speed of 0 m, and water is spouted from the nozzle 5 in the form of mist. Since the temperature inside test chamber 2 at this time is around -10℃, the fog freezes instantaneously, becomes ice crystal nuclei with a diameter of 30μ or less, and falls uniformly on the water surface whose temperature is close to 0℃. A floating layer 26b of ice crystal nuclei is formed [FIG. 3c].

[Process] Alternating low-speed wind with a wind speed of approximately 0.3 to 0.5 m/sec, and in which the wind direction alternates in opposite directions at predetermined intervals, is used to cool the ice layer on the water surface to about -15°C without being washed away.

From point u, where the ice thickness has grown to about 3 mm or more, it is 0.5~
The ice layer is increased by re-cooling at a high speed of 1.0 m/sec and with cold air at -21℃ [Figure 3 d].

[Process] Next, in order to create ice layers of various strengths for experiments, an operation was performed to increase the temperature. In the device, high temperature air is sent into the test chamber 2 by operating the heater 17 of the cold air generator 20.

[Process] In the process of conducting the ice sea simulation experiment, select high-speed wind or low-speed wind and maintain the temperature in the test room constant. In this state, the entire carrier 28 shown in FIGS. 1 and 2 is moved along the rails 10a and 10b to cause the simulated ship 25 to run in the ice.

Furthermore, inside the carrier 28, the state of ice breaking, etc. is monitored.

After the experiment is finished, remove the remaining ice, and if you want to repeat the experiment again, repeat the same operation from the beginning.

The above operation commands are performed by commands from a timer or a program controller, and the blowing speed can be controlled by an inverter of the blower motor or by various other methods of controlling the motor rotation speed.

[Effects of the present invention]

According to the present invention described above, there are the following effects.

(1) In the present invention, the temperature inside the test chamber is lowered to a predetermined level as a pre-stage to create an ice sea consisting of an ice layer for experiments, but this is done by rapidly cooling with high-speed air blowing, so the room temperature decrease in the previous step can be reduced in a short time. It can be carried out.

This rapid cooling produces thin ice on the surface of the water in the aquarium, but because the thin ice is rapidly cooling,
Furthermore, since there is no alternating air flow, the thickness is uneven and the strength also varies from part to part.

However, in the present invention, this thin ice with uneven thickness and strength is removed once, and then the ice crystal nuclei are allowed to fall calmly and uniformly to the water surface in no wind or light wind conditions, forcing the cold air to become an alternating air current. This method promotes the growth of ice by blowing air along the water surface, and when air is blown in one direction, the ice layer forms with a difference in thickness and strength between the upstream and downstream sides of the wind. It is possible to create a simulated ice sea with an ice layer of uniform thickness and even strength over the entire front surface.

(2) Since the freezing rate of ice is proportional to the heat transfer coefficient between water and air, by using the forced convection method for the cooling air flow, the amount of heat taken from the water (ice) by the air flow per unit time increases. Freezing rate is 2.0 to 2.5 compared to conventional
The speed increases from mm/h to 3 to 3.5 mm/h, making it possible to shorten the experimental cycle.

(3) There is a partial pressure difference of about 20 mmHg between the saturated water vapor partial pressure on the ice and the water vapor partial pressure in the cooling air, but forced convection is occurring in the test room, and the fog that forms on the ice surface is transferred to the outside of the test room. It is sucked in and captured by the cold air generator, and can be removed by defrosting etc. on the cold air generator side. Therefore, avatars on the ice are caused by falling lumps of frost generated on the cooler during natural convection method or falling condensate during defrosting. This eliminates the phenomenon that occurs.

(4) Since this method creates cold air by forcing air into the cooling coil, the heat transfer rate to the air is high, and when the wind speed is approximately 2.5 m/s, the heat transfer rate is approximately 20 to 30 Kcal/m ²・h・℃,
Compared to conventional cooling coils, the heat transfer area is only about one-fourth, and the cost of experimental equipment can be reduced.

(5) It has been experimentally confirmed that the method of forming ice at high speed from ice crystal nuclei of 30 μm or less improves ice quality, making it possible to conduct accurate experiments.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of an experimental apparatus for carrying out the method for producing a simulated ice sea according to the present invention, Fig. 2 is a longitudinal sectional side view of the same, Figs. The figure is a diagram showing temperature changes in the test chamber. In the figure: 1...Insulated chamber body, 2...Test chamber, 3...Water tank, 4...Water, 5...Nozzle, 6...Water pipe, 7...
Refrigerant pipe, 8... Water sprinkler, 11a, 11b... Cold air inlet/outlet, 10a, 10b... Rail, 13a, 13b
...Cold air duct, 12a, 12b...Chamber, 1
5...Casing, 14a, 14b...Cold air supply device,
15b...Suction side, 15a...Cold air outlet, 16...Blower, 17...Heater, 18...Freezer, 19...Cooling coil, 20...Cold air generator, 21a, 21b, 23
a, 23b...Damper, 22...Blower duct, 22
a, 22b...branch duct, 24a, 24b...return duct, 25...mock ship, 26...ice, 27...rod, 28...carrier.

Claims (1)

[Claims] 1. A low-temperature cold air below freezing is blown at high speed along the surface of the water in the tank into a test chamber equipped with a water tank to quickly cool the inside of the test room and form thin ice on the surface of the water in the tank. After temporarily stopping air blowing into the test chamber and appropriately removing the thin ice with uneven strength generated by rapid cooling, water was sprayed into the test chamber in the form of a mist, and the mist instantly froze. By uniformly scattering ice crystal nuclei on the surface of the water in the aquarium, and then blowing low-temperature cold air along the ice layer, and creating an alternating airflow in which the direction of the airflow reverses every required time. A method for producing a simulated ice sea characterized by growing ice crystal nuclei in an aquarium to form an ice layer.