JP6687974B2 - Ground freezing method - Google Patents

Description

  The present invention relates to a ground freezing construction method, and more particularly to a technique for determining a construction specification or a construction plan when constructing a ground freezing construction method.

The ground freezing method has a proven track record in tunnel excavation, etc., and has recently been applied to block groundwater flow.
When constructing the ground freezing method, it is necessary to determine various numerical values such as the diameter and length of the piping for circulating the refrigerant (brine), the route, the discharge pressure of the pump for circulating the refrigerant, the discharge flow rate, etc. , Construction plan).
In this specification, the determination of construction specifications or construction plans and the determination of various numerical values are collectively referred to as “design”.

However, in the conventional design, various numerical values required for construction were determined by "intuition" backed by the experience of the designer.
When carbon dioxide is selected as the refrigerant here, the properties of carbon dioxide are different compared to the brine used in the conventional freezing method, so designing based on experience and intuition only makes inefficient freezing. Otherwise, a situation occurs in which the ground cannot be frozen because the refrigerant does not circulate.
Therefore, it is desired to design after determining a clear standard, but in the ground freezing method, a technique for defining a "clear standard" necessary for construction has not been proposed at this time.

As another conventional technique, for example, a ground freezing method using a freezing material having high fluidity and thermal conductivity and having a low freezing latent heat has been proposed (see Patent Document 1).
However, even in the technique (Patent Document 1), there is no disclosure of defining "clear criteria" necessary for construction at the design stage.

JP, 2008-69246, A

  The present invention has been proposed in view of the above-mentioned problems of the conventional technology, and an object thereof is to provide a ground freezing construction method that enables efficient construction by designing by defining the criteria necessary for construction. .

In the ground freezing method of the present invention, carbon dioxide is used as a refrigerant, the theoretical value of pressure loss (ΔPcal) is calculated, and the numerical value (expected value: ΔPp) corresponding to the actual measured value of pressure loss is calculated and calculated. Calculate and determine various items required for construction from the expected pressure loss value (△ Pp),
When calculating the expected value (ΔPp) of the pressure loss, the theoretical value (ΔPcal) of the pressure loss is a predetermined construction condition (outline of construction: position, volume, refrigerator, etc. of region to be frozen). From the position where the pump can be installed, etc., calculate from the minimum required carbon dioxide flow rate, the length of the piping system, the approximate route, etc.), and calculate the theoretical value (ΔPcal) It is characterized by multiplying the characteristic (ΔPexp / ΔPcal: KL, KG) .

In the present invention, the characteristics of the theoretical and measured values (△ Pexp / △ Pcal: KL , KG) , the refrigerant (carbon dioxide) is different between cases where the and the gas phase of the liquid phase, be separately used depending on the conditions Is preferred.

In the present invention, in the case where a problem occurs (for example, efficiency is low, refrigerant does not circulate, etc.) when the work is performed with the specifications designed based on the predicted value of pressure loss (ΔPp), design of a method for solving the problem. Is preferably performed using the expected value of pressure loss (ΔPp).

In the present invention, the two ratios between the measured value and the theoretical value of the pressure drop in the carbon monoxide (KG, KL), the in carbon dioxide ratio (KG, KL) and flow characteristics (characteristic curve CG in FIGS. 3-6 , CL, CLh, CGh: KL, KG: or an approximate expression KL = 20Q ^−0.5 , KG = 15 / Q) .

According to the ground freezing method of the present invention having the above-mentioned configuration, the minimum required dioxide that is determined from the construction conditions (for example, the position and volume of the region to be frozen, the installable position of the refrigerator or pump, etc.) The theoretical value (ΔPcal) of the pressure loss is obtained based on the carbon flow rate, the length of the piping system, the approximate route, etc., and the theoretical value (ΔPcal) of the pressure loss has the characteristic (ΔPexp / ΔPcal: KL, KG) is multiplied to obtain an expected pressure loss value (ΔPp), and assuming that the expected pressure loss value (ΔPp) is the same as the pressure loss, the design items necessary for construction are determined. It can be calculated.
Then, it is much easier to calculate or determine the design item by using the specific numerical value (predicted pressure loss value ΔPp) as a guide, as compared with the conventional method of determining the design item by intuition or experience. In addition, the design items can be set to appropriate numerical values. Here, in the freezing method, the refrigerant discharged from the cooling equipment returns to the cooling equipment, and the refrigerant is circulated. Therefore, the pressure loss in the refrigerant circulation system is an important parameter in design.
Therefore, even when using a different refrigerant, for example, carbon dioxide, compared to the brine used in the conventional freezing method, a specific numerical value of pressure loss is used as a guideline for easy and good design. You can do it.

According to the present invention, the theoretical pressure loss (ΔPcal) is multiplied by the characteristics of the theoretical value and the measured value (ΔPexp / ΔPcal: KL, KG) to calculate the expected pressure loss value (ΔPp). The characteristic can be used depending on whether the refrigerant (carbon dioxide) is in the liquid phase (KL) or in the gas phase (KG).
Therefore, even if it is a refrigerant such as carbon dioxide that vaporizes from the liquid phase to the gas phase when it freezes the ground, or becomes a gas-liquid two phase, the theoretical value and the actual measurement should be taken into consideration in consideration of the phase change of the refrigerant. By properly using the value characteristics (ΔPexp / ΔPcal: KL, KG), it becomes possible to approximate the expected pressure loss value (ΔPp) to actual construction.

In addition, even if various design items are determined from the above-mentioned expected pressure loss value (ΔPp) and construction is not performed, the efficiency of the ground freezing method is not good, or the circulation of the refrigerant (carbon dioxide) is not good. Must determine the method to deal with by changing the construction specification or construction plan, and determine the design items for executing the method.
According to the present invention, when the design item for executing the method is determined, the expected value (ΔPp) of the pressure loss described above can be used for calculation and determination.

It is explanatory drawing which shows the outline | summary of embodiment of this invention. 6 is a flowchart showing a designing procedure in the embodiment. FIG. 7 is a characteristic diagram showing a relationship between a flow rate and a numerical value KL (= ΔPexp (L) / ΔPcal (L)) obtained by dividing a measured value of pressure loss when carbon dioxide is in a liquid phase by a theoretical value. FIG. 4 is a characteristic diagram similar to FIG. 3, in which an approximate curve is divided into an upper limit CLh and a lower limit CLl. It is a characteristic view which shows the numerical value KG (= (DELTA) Pexp (G) / (DELTA) Pcal (G)) which divided the measured value of the pressure loss when carbon dioxide is a gas phase, and a flow volume. FIG. 6 is a characteristic diagram similar to FIG. 5, in which an approximate curve is divided into an upper limit CGh and a lower limit CGl. 3 is a flowchart showing a design procedure after the procedure shown in FIG. 2 in the embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, with reference to FIG. 1, an outline of a ground freezing method using carbon dioxide as a refrigerant will be described.
In FIG. 1, a freezing pipe 1 is extended from the ground side to a region F (frozen soil planned part) corresponding to a frozen part in the ground G. A refrigerator 4 and a pump 5 are arranged on the ground side, and the refrigerator 4 and the pump 5 are connected to the connecting pipe 1 via an iron-made refrigerant supply pipe 2 and a refrigerant return pipe 3.
The portion corresponding to the region F in the freezing pipe 1 is constituted by a refrigerant pipe 1A made of, for example, aluminum. The refrigerant pipe 1A is connected to the refrigerant supply pipe 2 and the refrigerant return pipe 3 via a branch pipe 1B (for example, made of copper) in a region on the ground side of the refrigerant pipe 1A in the freezing pipe 1. Here, the refrigerant pipe 1A and the branch pipe 1B are connected by, for example, a socket (not shown).
A temperature measuring pipe 6 is embedded in the vicinity of the region F corresponding to the freezing part, and the underground temperature at a plurality of side temperature points 6A is measured. Note that reference numeral 7 indicates a refrigerator compartment that houses the refrigerator 4, the pump 5, and other related equipment (not shown).

The liquid phase carbon dioxide liquefied in the refrigerator 4 is discharged from the pump 5, supplied into the freezing pipe 1 via the refrigerant supply pipe 2, and flows through the branch pipe 1B in the freezing pipe 1 into the refrigerant pipe 1A. Flowing. At that time, the liquid-phase carbon dioxide removes heat (sensible heat and / or latent heat) from the region F to be frozen and becomes vapor-phase carbon dioxide, which rises to the ground side. Alternatively, part of the gas is vaporized into a gas-liquid two-phase flow, and the rising gas-phase carbon dioxide carries the liquid-phase carbon dioxide.
The gas-phase or gas-liquid two-phase flow of carbon dioxide that has passed through the branch pipe 1B in the freezing pipe 1 flows through the refrigerant return pipe 3 and is returned to the refrigerator 4, is liquefied again in the refrigerator 4, and is again pumped from the pump 5. Is ejected. Then, this cycle is repeated until the freezing method is completed.

Here, in FIG. 1, the single freezing pipe 1 (branch pipe 1B, medium pipe 1A) is connected to the refrigerator 4 and the pump 5, but in the actual construction, it is connected to the refrigerator 4 and the pump 5. Branch pipes 1B (made of copper, for example) are branched from a plurality of places of the refrigerant supply pipe 2 and the refrigerant return pipe 3 (made of iron, for example), and each branch pipe 1B is a refrigerant pipe 1A in each freezing pipe 1. Connected with. Therefore, a plurality of regions can be frozen at the same time.
Further, although not clearly shown, the refrigerant pipe 1A in the freezing pipe 1 is provided with, for example, a plurality of minute pipe lines therein (so-called “microchannel”). However, the refrigerant pipe 1A in the freezing pipe 1 may be configured by a single pipe (for example, a U-shaped pipe) or a double pipe.

When constructing the ground freezing method shown in FIG. 1, for example, regarding the piping system, it is necessary to determine the piping material, the pipe diameter, the pipe friction coefficient, the length, and other design items. Also, regarding the refrigerant pipe 1A in the freezing pipe 1, its type (whether it is a microchannel, a double pipe or a single pipe), and if it is a microchannel, a single microchannel is used. Whether or not carbon dioxide flows only in the direction, or both directions of the supply side and the return side, must be determined. Further, for the pump 5, for example, the discharge pressure, the discharge flow rate, etc. must be determined.
However, the various design items (parameters) described above are related to each other, and it is difficult to determine them at the time of designing.

On the other hand, in the illustrated embodiment, the design items necessary for construction are calculated according to the procedure shown in FIG.
In FIG. 2, a construction outline is determined in step S1. As a construction outline, the position of the area F corresponding to the area to be frozen (planar position, depth range of the area to be frozen), the volume of the area F, the installable position of the refrigerator 4, the pump 5, and the like are determined.
Further, from the construction outline, the flow rate of carbon dioxide, which is the minimum required refrigerant, and the length of the piping system (refrigerant supply pipe 2, refrigerant return pipe 3, branch pipe 1B in the freezing pipe, refrigerant pipe 1A), Determine the general route, etc. (decision of construction conditions).

In step S2, the construction outline (position of the area F corresponding to the area portion to be frozen, volume of the area F, installable position of a refrigerator or pump, etc.) determined in step S1, construction conditions (carbon dioxide flow rate, piping The theoretical pressure loss ΔPcal is calculated for each of the case where the carbon dioxide is 100% gas and the case where the carbon dioxide is 100% liquid, according to the length of the system, the approximate route, etc.).
The calculation of the theoretical pressure loss ΔPcal can be performed using conventionally known mathematical expressions, empirical expressions, and the like.

In step S3, the pressure loss of the pressure loss is calculated based on the theoretical value ΔPcal of the pressure loss calculated in step S2 and “the characteristic of the theoretical value and the actual measurement value (ΔPexp / ΔPcal)” described later with reference to FIGS. The expected value ΔPp (a numerical value corresponding to the actual measured value of pressure loss) is calculated and determined. Specifically, the theoretical pressure loss ΔPcal is multiplied by the characteristic (ΔPexp / ΔPcal = coefficient K) of the theoretical value and the actual measurement value to calculate the expected pressure loss value ΔPp.
“Characteristics of theoretical value and measured value (ΔPexp / ΔPcal)” described later with reference to FIGS. 3 to 6 is (ΔPexp (L) / ΔPcal (when the carbon dioxide flowing through the piping system is a liquid. L)), and when the carbon dioxide flowing through the piping system is a gas, it is (ΔPexp (G) / ΔPcal (G)), and both are different. That is, "the characteristic between the theoretical value and the measured value (ΔPexp / ΔPcal)" indicates whether the pressure loss to be obtained is the pressure loss in the case where the carbon dioxide is in the liquid phase or the pressure loss in the case where the carbon dioxide is in the gas phase. To use properly.

In determining the expected pressure loss value ΔPp, for example, the result calculated using the characteristics (ΔPexp (L) / ΔPcal (L)) of the theoretical value and the actual measured value in the liquid, the theoretical value and the actual measured value in the gas It is possible to set the numerical value satisfying both conditions of the result calculated by using the value characteristic (ΔPexp (G) / ΔPcal (G)) as the predicted pressure loss value ΔPp.
In other words, in addition to theoretical pressure loss ΔPcal, characteristics of theoretical value and measured value in liquid (ΔPexp (L) / ΔPcal (L)) and characteristics of theoretical value and measured value in gas (ΔPexp (G)) It is possible to calculate the expected pressure loss value ΔPp by multiplying the characteristic (ΔPexp / ΔPcal = coefficient K) satisfying both conditions of / ΔPcal (G).

Further, for example, when determining the expected pressure loss value ΔPp, as is clear from FIG. 1, since carbon dioxide flowing in the iron-made refrigerant supply pipe 2 is in the liquid phase, when determining design items in the refrigerant supply pipe 2, It is preferable to calculate using the characteristic (ΔPexp (L) / ΔPcal (L)) of the theoretical value and the actually measured value in the liquid.
Regarding the pressure loss in the copper branch pipe 1B (supply side) that connects the iron refrigerant supply pipe 2 and the refrigerant pipe 1A in the freezing pipe 1, since the supply side is in the liquid phase, the theoretical value and the measured value in the liquid It is preferable to use the characteristic (ΔPexp (L) / ΔPcal (L)).

On the other hand, it is better to calculate the carbon dioxide flowing in the refrigerant pipe 1A in the freezing pipe 1 as a gas phase, which is in better agreement with the actual behavior. It is preferable to use the characteristic (ΔPexp (G) / ΔPcal (G)) of the theoretical value and the actually measured value in the gas for calculation.
Similarly, in the iron-made refrigerant return pipe 3, the flowing carbon dioxide is in a gas phase or a gas-liquid two-phase, so (when determining design items in the refrigerant return pipe 3) characteristics of theoretical value and measured value in gas It is preferable to perform the calculation using (ΔPexp (G) / ΔPcal (G)).
Further, regarding the pressure loss in the copper branch pipe 1B (return side) that connects the iron refrigerant return pipe 3 and the refrigerant pipe 1A in the freezing pipe 1, similarly, the characteristics (ΔPexp) of the theoretical value and the measured value in the gas (ΔPexp It is preferable to calculate using (G) / ΔPcal (G).

In step S4, using the predicted pressure loss value ΔPp calculated in step S3,
Calculates various design items required for construction.
The design items calculated from the predicted pressure loss value ΔPp include, for example, the pipe material, pipe diameter, and the like for the piping system (refrigerant supply pipe 2, refrigerant return pipe 3, branch pipe 1B in the freezing pipe, refrigerant pipe 1A). There are pipe friction coefficient, pipe length, etc. Further, in the case of the refrigerant pipe 1A in the freezing pipe 1, determining the type of pipe (microchannel, double pipe, or single pipe) is also included in the design item. Further, if the refrigerant pipe 1A in the freezing pipe 1 is a micro channel, whether carbon dioxide flows in only one direction in a single micro channel, or whether carbon dioxide flows in both directions of the supply side and the return side is a design item. Must be decided as.
Further, for the pump 5, for example, the discharge pressure and the discharge flow rate can be calculated from the expected pressure loss value ΔPp.
However, the design items calculated from the pressure loss (predicted pressure loss value ΔPp) are not limited to the above-mentioned parameters.

In step S4, each of the various design items described above is not uniquely determined from the expected pressure loss value ΔPp. As described above, formulas and empirical formulas for determining pressure loss from the numerical values of various design items (for example, pipe diameter of pipe system, pipe line length, discharge pressure of pump 5, discharge flow rate, etc.) determined at the time of design Etc. are conventionally known, and the numerical values of various design items can be appropriately calculated from the predicted value ΔPp of the pressure loss using the formula or the like.
Although the expected pressure loss value ΔPp is an “estimated value”, if the “pressure loss” is found even though it is an expected value, various design items can be calculated using the obtained pressure loss (estimated pressure loss value ΔPp). I can. The calculation of various design items using the “predicted pressure loss value ΔPp” depends on “experience” and “intuition” of various design items that are related to each other without any guidelines. It is much easier and more accurate than the conventional task of determining.
Therefore, according to the illustrated embodiment, it is possible to reduce the labor required for design and improve the design accuracy.

Next, the characteristics (ΔPexp / ΔPcal) between the theoretical value and the actually measured value will be described with reference to FIGS. 3 to 6.
The inventor changed various conditions for the iron refrigerant supply pipe 2 and the refrigerant return pipe 3, the copper branch pipe 1B in the connecting pipe 1, and the refrigerant pipe 1A in the freezing pipe 1 in FIG. The theoretical value ΔPcal and the actual measurement value ΔPexp were calculated. As the refrigerant pipe 1A in the freezing pipe 1, a "micro channel" having a plurality of micro pipes formed therein was used.

  In an experiment conducted by the inventor when obtaining the theoretical value ΔPcal of pressure loss and the actually measured value ΔPexp, in the iron refrigerant supply pipe 2 and the refrigerant return pipe 3, the inner diameters are about 20 mm (20 A) and about 25 mm (25 A), With respect to three types of about 50 mm (50 A), the lengths were set to four types of 30 m, 65 m, 100 m and 130 m. The flow rate is changed to 7.0 L (liter) / minute, 17.0 L / minute, and 38.0 L / minute for "20 A", and 20.0 L (liter) / minute, 38.0 L for "25 A". / Min, 69.0 L / min, and for "50A", 15.0 L (liter) / min, 37.0 L / min, 58.0 L / min, 76.0 L / min, 93.0 L / min, It was changed to 150.0 L / min.

As for the copper branch pipe 1B, two types were prepared with an inner diameter of about 10 mm (10 A) and a length of 30 m, and an inner diameter of about 15 mm (15 A) and a length of 30 m. The flow rate was changed to 1.3 L / min, 3.1 L / min, 5.4 L / min, and 7.3 L / min for 10 A, and 1.0 L / min, 2.5 L / min for 15 A, and 4. It was changed to 7 L / min, 11.1 L / min, and 15.3 L / min.
The microchannel (refrigerant pipe 1A) having a width of 48 mm (W48R) was selected, and the length was set to 4 ways of 1 m, 5 m, 10 m, and 20 m. The flow rate was changed to 1.1 L / min, 3.4 L / min, 5.1 L / min, 9.8 L / min for a length of 1 m, and 1.5 L / min, 3.0 L / min for a length of 5 m, 4.8 L / min and 7.0 L / min, 1.4 L / min at 10 m length, 2.7 L / min and 5.3 L / min, and 20 L length at 1.4 L / min, It was changed to 2.1 L / min.

Then, the inventor measures the pressure loss (measured value ΔPexp: measurement result in gas-liquid two-phase flow) for each of the above-described values, calculates a theoretical value (theoretical value ΔPcal), and theoretically calculates the measured pressure loss value ΔPexp. A value was obtained by dividing the value by ΔPcal.
In FIG. 3, a value KL (= ΔPexp (L) / ΔPcal (L)) obtained by dividing the measured pressure drop ΔPexp (L) by the theoretical value ΔPcal (L) in the case where carbon dioxide is in the liquid phase is given. A characteristic diagram in which the relationship with the flow rate is plotted (“●”) is shown.
In FIG. 3, a curved line CL indicated by a dotted line is an approximate curve.

4 is a characteristic diagram similar to that shown in FIG. 3, but the approximation curve is an upper limit approximation curve (curve CLh in FIG. 4) that approximates the upper limit plot (the plot of “●” in FIG. 4), The lower limit approximation curve (curve CL1 in FIG. 4) that approximates the lower limit plot (the plot of “■” in FIG. 4) is divided and expressed.
As is clear from FIG. 4, the lower limit approximation curve CL1 is close to the coordinate axes. Therefore, only the upper limit approximation curve CLh needs to be considered.

In FIG. 5, the value KG (= ΔPexp (G) / ΔPcal (G)) obtained by dividing the measured pressure drop ΔPexp (G) by the theoretical value ΔPcal (G) in the case where carbon dioxide is in the gas phase. A characteristic diagram in which the relationship with the flow rate is plotted (“■”) is shown.
Also in FIG. 5, the curve CG indicated by the dotted line is an approximate curve.

6 is similar to FIG. 4, the upper limit approximation curve (curve CGh in FIG. 6) that approximates the approximation curve to the upper limit plot (the plot of “●” in FIG. 6) and the lower limit plot (the curve “CG” in FIG. 6). It is expressed by dividing it into a lower limit approximation curve (curve CG1 in FIG. 6) that is similar to the "(2) plot".
Also in FIG. 6, the lower limit approximation curve CG1 is close to the coordinate axes. Therefore, even when carbon dioxide is in a gas phase, it is understood that only the upper limit approximation curve CGh needs to be considered.

When calculating the expected pressure loss value ΔPp in step S3 of FIG. 2, a plot (from either the lower region of the approximate curve CLh of FIG. 4 or the lower region of the approximate curve CGh of FIG. (Relationship between KL or KG and flow rate) is selected.
Then, the expected pressure loss value ΔPp is calculated by multiplying the theoretical pressure loss ΔPcal calculated in step S2 by the selected KL or KG.
Using the predicted pressure loss value ΔPp thus calculated, various items in the design are calculated or determined, and the ground freezing method shown in FIG. 1 is constructed.

  Here, in FIGS. 4 and 6, KL and KG are selected in a region above the upper limit approximate curves CLh and CGh, and the selected KL or KG is theoretically pressure loss ΔPcal (see step S2 in FIG. 2). ) To calculate the expected pressure loss value ΔPp and design using the estimated pressure value ΔPp, the ground freezing method cannot be efficiently constructed, or the refrigerant carbon dioxide It has been confirmed by the inventor's experiment that it does not circulate.

Further, instead of using the upper limit approximation curves CLh and CGh in the characteristic diagrams of FIGS. 4 and 6, it is possible to use approximation formulas of the approximation curves CLh and CGh.
According to the calculation by the inventor, the approximate expression of the upper limit approximation curve CLh (when carbon dioxide is in the liquid phase) in the characteristic diagram of FIG. 4 is KL = 20Q ^−0.5 . Here, Q is the flow rate.
When using this approximate expression (KL = 20Q- ^0.5 ), KL that satisfies the inequality KL <20Q- ^0.5 may be selected.

On the other hand, the approximate expression of the upper limit approximation curve CGh (when carbon dioxide is in the gas phase) in the characteristic diagram of FIG. 6 is KG = 15 / Q.
When using this approximate expression (KG = 15 / Q), it is sufficient to select a KG that satisfies the inequality KG <15 / Q.
Range not satisfying the above inequality, that is, KL ≧ 20Q ^−0.5 inequality region (when carbon dioxide is in liquid phase) or KG ≧ 15 / Q inequality region (when carbon dioxide is in gas phase) In this case, it has been confirmed by the inventor's experiment that the ground freezing method cannot be efficiently constructed, or that carbon dioxide, which is a refrigerant, does not circulate.

The plot (relationship between KL or KG and the flow rate) is selected from the region under the approximate curves CLh and CGh in FIG. 4 or 6 to obtain the predicted pressure loss value ΔPp, and based on the predicted pressure loss value ΔPp. There are cases where the efficiency is not good at the time of construction or the circulation of the refrigerant (carbon dioxide) is not good even if the design is performed (the numerical values of various design items are calculated). In such a case, for example, it is possible to deal with the problem by adding a pump 5 for the refrigerant.
Here, for example, even when the pump 5 for the refrigerant is added, there arises a design problem such as how much the discharge pressure of the pump should be increased, and the discharge flow rate.
According to the illustrated embodiment, the design problem in such a case can be easily solved by the procedure shown in FIG. 7.

In step S11 in FIG. 7, the ground freezing method is constructed according to the construction specification or construction plan determined by the various design items calculated in FIG. Then, the process proceeds to step S12.
In step S12, the construction status of the ground freezing method in step S11 is verified, and it is examined (checked) whether or not there is any inconvenience (for example, poor construction efficiency, poor refrigerant (carbon dioxide) circulation, or the like). As a result of the examination, if the construction situation is inconvenient (Yes in step S12), the process proceeds to step S13.
As a result of the verification in step S12, if there is no inconvenience in the construction status (step S12 is No), the procedure of FIG. 7 is ended.

In step S13, a method for eliminating the inconvenience confirmed in step S12, for example, a method for adding a refrigerant pump, a method for changing the piping system to increase the refrigerant flow rate, and the like are determined.
Although not shown, in the “decision of method” in step S13, it is possible to appropriately select from the conventional construction data stored in the database in the system, or the operator can decide. It is only necessary to select the method with the highest feasibility in the various construction site environments.

In the next step S14, the concrete specifications (numerical values) of the design items to be decided when the method decided in step S13 (to eliminate the inconvenience) are executed, the predicted value of the pressure loss obtained in step S3 of FIG. It is calculated and determined using ΔPp.
For example, if it is decided in step S13 to add a pump for refrigerant, it is necessary to calculate the discharge pressure, discharge flow rate, etc. of the pump as design items. In the past, in order to determine the discharge pressure, discharge flow rate, etc. of the pump, we had to rely on the experience and intuition of “experienced workers”, so we had to repeat trial and error, and it took time to design (specify). There was a problem that the construction period would be lengthened accordingly.

On the other hand, in the illustrated embodiment, the discharge pressure, the discharge flow rate, etc. of the pump can be calculated using the predicted pressure loss value ΔPp obtained in step S3 of FIG.
As described above, the relational expression (or arithmetic expression) between various design values (for example, the pipe diameter of the piping system, the pipe length, the discharge pressure of the pump 5, the discharge flow rate, etc.) and the pressure loss value is known, and the pressure loss Calculating the discharge pressure, discharge flow rate, etc. of the pump using the predicted value ΔPp is much easier and more accurate than determining the discharge pressure, discharge flow rate, etc. of the pump by intuition and experience. is there.
Also, when it is decided to increase the refrigerant flow rate by changing the piping system in step S13, similarly, the pipe diameter of the piping system, the pipe friction coefficient, the length, and other design items are set as the design items in the step of FIG. The expected value ΔPp of the pressure loss obtained in S3 can be used for easy calculation or determination.

According to the illustrated embodiment of the present invention, the theoretical value ΔPcal of pressure loss is determined based on the construction conditions (for example, the minimum required carbon dioxide flow rate, the length of the piping system, the approximate route, etc.), The theoretical value ΔPcal of the pressure loss is multiplied by the characteristics of the theoretical value and the measured value (ΔPexp / ΔPcal: KL, KG) to obtain the expected value ΔPp of the pressure loss, and the design items necessary for construction are calculated.
Therefore, it is possible to calculate a design item required for construction much more easily and obtain an appropriate numerical value, as compared with the case where the design item is determined by conventional intuition or experience.
Therefore, even when carbon dioxide, which has various characteristics different from those of the brine used in the conventional freezing method, is used as a refrigerant, a good design can be easily performed.

Further, according to the illustrated embodiment, it is possible to use the characteristics of the theoretical value and the actually measured value (ΔPexp / ΔPcal: KL, KG) for the liquid phase and the gas phase, and to approximate the actual construction.
Further, according to the illustrated embodiment, in the case where the efficiency of the ground freezing method is not good even when various design items are determined from the expected pressure loss value ΔPp and the construction is performed, the construction specification or the construction plan is changed to cope with the situation. When the method to be performed is determined, various design items required to execute the method to be dealt with can be easily and accurately calculated using the predicted pressure loss value ΔPp.

  It should be noted that the illustrated embodiment is merely an example and is not intended to limit the technical scope of the present invention.

1 ... Freezing pipe 1A ... Refrigerant pipe 1B ... Branch pipe 2 ... Refrigerant supply pipe 3 ... Refrigerant return pipe 4 ... Refrigerator 5 ... Pump 6 ... Temperature measurement Tube 7 ... Refrigerator room F ... Area corresponding to frozen section

Claims (4)

Using carbon dioxide as a refrigerant, the theoretical value of pressure loss is calculated, the numerical value equivalent to the actual value of pressure loss is calculated, and various items necessary for construction are calculated and determined from the calculated expected value of pressure loss ,
When calculating the expected value of the pressure loss, the theoretical value of the pressure loss is calculated from the predetermined construction conditions, and the theoretical value of the pressure loss is multiplied by the characteristics of the theoretical value and the actual measurement value. . The ground freezing method according to claim 1 , wherein the characteristics of the theoretical value and the actually measured value are different depending on whether the refrigerant is in the liquid phase or in the gas phase, and used properly according to the conditions. The method according to any one of claims 1 and 2 , wherein, when a construction is carried out with specifications designed on the basis of the predicted value of the pressure loss and a problem occurs, the method of eliminating the problem is designed using the predicted value of the pressure loss . Ground freezing method. The ratio between the measured value and the theoretical value of the pressure drop in the carbon dioxide, soil freezing method according to claim 1, selected from a range equal to or smaller than the characteristics of the ratio and the flow rate in the carbon dioxide.

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