KR20220005182A - Calculation method of input amount of liquid for cooldown and computer-readable recording medium thereof - Google Patents

Abstract

The present invention relates to a calculation method of input amount of liquid for cooldown and computer-readable recording medium with computer program for executing the same on a computer. According to an embodiment of the present invention, the calculation method of the input amount of the liquid for cooldown comprises: a step of calculating a vaporized amount of a unit droplet (1) by using a change in a radius (r) of the unit droplet (1) of the liquid for cooldown (10) falling as a first input amount is inputted into a cargo warehouse (100); a step of repeating the step of calculating the vaporized amount of the unit droplet (1) until a reference point of time, and calculating the total vaporized amount of the unit droplet (1); a step of multiplying the total vaporized amount of the unit droplet (1) by the total number of the unit droplets (1) and calculating the total vaporized amount of the liquid for cooldown (10); a step of calculating the internal temperature of the cargo warehouse (100) after the first input amount of the liquid for cooldown (10) is inputted into the cargo warehouse (100) by using the total vaporized amount of the liquid for cooldown (10); and a step of, when the internal temperature of the cargo warehouse (100) is the same as a target internal temperature of the cargo warehouse (100), determining the first input amount of the liquid for cooldown (10) inputted into the cargo warehouse (100) as the final input amount of the liquid for cooldown (10). The present invention aims to provide a calculation method of input amount of liquid for cooldown and computer-readable recording medium with computer program for executing the same on a computer, which are capable of rapidly and precisely calculating the input amount of the liquid for cooldown into a cargo warehouse.

Description

A computer-readable recording medium in which a computer program for executing a method of calculating the input amount of a liquid for cool-down and executing the method is recorded on a computer

The present invention relates to a method for calculating the input amount of liquid for cool-down and to a computer-readable recording medium in which a computer program for executing the method is recorded on a computer, in particular, to a method for calculating the input amount of liquid for cool-down in a cargo hold and the same It relates to a computer-readable recording medium in which a computer program for executing the method in a computer is recorded.

Natural gas is transported in gaseous state through land or sea gas pipelines, or liquefied in the state of liquefied natural gas or liquefied petroleum gas, and then stored in LNG carriers or LPG carriers. transported to remote consumers.

Liquefied natural gas is obtained by cryogenically cooling natural gas, and its volume is reduced to about 1/600 of that of gaseous natural gas, so it is suitable for long-distance transportation by sea.

An LNG carrier for loading and unloading LNG to an onshore destination by operating the sea, or an LNGRV (regasification vessel) that loads LNG and operates the sea to arrive at an onshore destination, then regasifies the stored LNG and unloads it into natural gas ) includes a storage tank (usually called a cargo hold) that can withstand the cryogenic temperature of liquefied natural gas.

A storage tank for storing liquefied gas such as LNG in a cryogenic state provided in offshore structures such as LNG carriers, LNG RVs, LNG FPSOs, and LNG FSRUs is the first time liquefied gas is shipped or maintained after the production of the storage tank is completed. In the case of shipping liquefied gas after the storage tank is completely emptied and maintenance work is completed for should take precedence

In the replacement method of the liquefied gas storage tank, dry gas is supplied to the inside of the liquefied gas storage tank to remove moisture, and in order to eliminate the possibility of fire or explosion, an inert gas is supplied to the inside of the liquefied gas storage tank to remove oxygen. process is required.

In addition, a hydrocarbon gas of the same component as the liquefied gas to be stored in the storage tank is supplied to the inside of the liquefied gas storage tank to remove the inert gas, and the liquefied gas storage tank is cooled by using a liquefied gas such as LNG. ) process, and finally, liquefied gas such as LNG is supplied to the inside of the liquefied gas storage tank to carry out the shipping operation.

In this cool-down process, since the temperature must be lowered within a given time enough that thermal stress does not occur even when cryogenic cargo enters, spraying through a nozzle is common.

The present invention provides a method for calculating the amount of liquid for cool-down that quickly calculates the amount of liquid for cool-down in a cargo hold without using a complicated method such as computational fluid dynamics, and a computer program for executing the method on a computer. , to provide a computer-readable recording medium.

In the method for calculating the input amount of the cool-down liquid according to an embodiment of the present invention, the first input amount is input into the cargo hold 100 and the radius r of the unit droplet 1 of the cool-down liquid 10 falls calculating the vaporization amount of the unit droplet (1) using the change; calculating the total vaporization amount of the unit droplet (1) by repeating calculating the vaporization amount of the unit droplet (1) until a reference time point; calculating the total vaporization amount of the cool-down liquid (10) by multiplying the total vaporization amount of the unit droplet (1) by the total number of the unit droplets (1); calculating an internal temperature of the cargo hold 100 after the first input amount of the cool-down liquid 10 is put into the cargo hold 100 using the total vaporization amount of the cool-down liquid 10; When the internal temperature of the cargo hold 100 is the same as the target internal temperature of the cargo hold 100 , the first input amount of the cool-down liquid 10 injected into the cargo hold 100 is set to the cool-down liquid 10 . ) to determine the final input amount.

In addition, when the calculated internal temperature of the cargo hold 100 is greater than the target internal temperature of the cargo hold 100, the method further includes the step of injecting a second input amount of the cool-down liquid 10 into the cargo hold can do.

In addition, the reference time may be a time when the radius r of the unit droplet 1 becomes 0 or a time when the unit droplet 1 reaches the bottom of the cargo hold 100 .

In addition, the section in which the unit droplet 1 falls within the cargo hold 100 includes a plurality of sub-fall sections in which the radius r of the unit droplet 1 changes and is connected to each other, and the unit droplet ( The total vaporization amount of 1) may be the sum of the vaporization amounts of each of the unit droplets 1 in the plurality of sub-falling sections.

In addition, the unit droplet 1 is a spherical unit droplet 1 , and the size of the radius r of the unit droplet 1 is the point at which the cool-down liquid 10 is put into the cargo hold 100 . It can be assumed that it decreases while descending from the to the bottom of the cargo hold 100 .

In addition, the target internal temperature of the cargo hold 100 may be -130 ℃.

In addition, there may be provided a computer-readable recording medium in which a computer program for executing a method of calculating an input amount of a liquid for cool-down according to an embodiment of the present invention is recorded on a computer.

By using the method for calculating the input amount of the cool-down liquid according to an embodiment of the present invention, it is possible to quickly and accurately calculate the input amount of the cool-down liquid input into the cargo hold.

Therefore, it is possible to quickly calculate the input amount of the liquid for cool-down injected into the cargo hold without using a complicated method such as computational fluid dynamics.

1 is a flowchart sequentially illustrating a method of calculating an input amount of a liquid for cool-down according to an embodiment of the present invention.
2 is a diagram schematically illustrating a cargo hold to which a method of calculating an input amount of a cooling-down liquid according to an embodiment of the present invention is applied.
FIG. 3 is a view for explaining a change in the radius of a unit droplet inside a cargo hold to which a method of calculating an input amount of a liquid for cool-down according to an embodiment of the present invention is applied.

Hereinafter, with reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement them. The present invention may be embodied in several different forms and is not limited to the embodiments described herein.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

The method of calculating the input amount of the liquid for cool-down according to an embodiment of the present invention will be described using an LNG storage tank (CT) (hereinafter referred to as a cargo hold) provided in an LNG carrier (LNGC) as an example. However, it can be employed not only in LNG carriers but also in offshore structures such as LNG RV (regasification vessel), LNG FPSO (floating, production, storage and offloading) or LNG FSRU (floating storage and regasification unit), and in addition to other low-temperature liquefied gas, It can be employed for cooling down storage tanks of ships or special ships for storing, transporting and transporting low-temperature liquefied cargo such as liquid hydrogen, liquid nitrogen, liquid carbon dioxide, and LPG. For example, it may be applied to a cool-down using LPG for an LPG fuel tank of an LPG ship, a cool-down using ethane for an ethane fuel tank of an ethane carrier, and the like.

The inside temperature of the cargo hold to which the cool-down liquid is supplied is higher than the outside temperature. Accordingly, when the liquid for cool-down is injected into the cargo hold, the liquid may be vaporized in the cargo hold and then discharged to the outside through a vent line.

1 is a flowchart sequentially illustrating a method for calculating an input amount of a liquid for cool-down according to an embodiment of the present invention, and FIG. 2 is a method for calculating an input amount of a liquid for cool-down according to an embodiment of the present invention is applied. It is a view schematically showing a cargo hold, and FIG. 3 is a view for explaining a change in the radius of a unit droplet inside a cargo hold to which the method for calculating the input amount of the cool-down liquid according to an embodiment of the present invention is applied. .

1 to 3 , in the method for calculating the input amount of the cool-down liquid according to an embodiment of the present invention, first, the first input amount is input into the cargo hold 100 and the cool-down liquid 10 is dropped. ) calculates the vaporization amount of the unit droplet 1 (S10).

Hereinafter, a method of calculating the vaporization amount of the unit droplet 1 will be described in detail.

At this time, the unit droplet 1 is a spherical unit droplet 1 , and the size of the radius r of the unit droplet 1 is the point 110 at which the cool-down liquid 10 is put into the cargo hold 100 . It is assumed that the height H from the cargo hold 100 to the floor 120 decreases while descending.

The vaporization amount of the unit droplet 1 is calculated using the change in the radius r of the unit droplet 1 of the liquid 10 for cooldown.

Accordingly, by calculating the change in the size and ambient temperature of the unit droplet according to heat exchange on the surface of the unit droplet 1 , it is possible to calculate the optimal input amount of the liquid 10 for cool-down injected into the cargo hold 100 .

As shown in Equation 1 below, the vaporization amount Mvap of the unit droplet 1 can be obtained.

Here, q is the amount of heat entering the unit droplet 1 from the periphery of the unit droplet 1 , and qh is the latent heat of the unit droplet 1 .

And, as shown in Equation 2 below, the amount of heat q entering the unit droplet 1 from the periphery of the unit droplet 1 can be obtained.

Here, h is the thermal convection coefficient of the unit droplet 1 , Tin is the internal temperature of the cargo hold 100 , and Ts is the surface temperature of the unit droplet 1 .

And, as shown in Equation 3 below, the thermal convection coefficient (h) of the unit droplet 1 can be obtained.

Here, Nu is the Nusselt number of the unit droplet (1), k is the thermal conductivity of the unit droplet (1), and D is the diameter of the unit droplet (1).

And, as shown in Equation 4 below, the Nussel number Nu of the unit droplet 1 can be obtained.

Here, Re is the Reynolds number, Pr is the Prandtl number, and m is the dynamic viscosity.

Next, the step of calculating the vaporization amount of the unit droplet 1 is repeated until the reference time point to calculate the total vaporization amount of the unit droplet 1 ( S20 ).

This will be described in detail below.

In the falling unit droplet 1, it is vaporized by the vaporization amount Mvap, and the remaining unit droplet 11 falls again and is vaporized. Accordingly, since a new vaporization amount is generated, the vaporization amount of the vaporized and remaining unit droplet 11 is calculated again.

Hereinafter, for convenience of description, the initial unit droplet 1 is defined as the primary unit droplet 1 , and the vaporized and remaining unit droplet 11 is defined as the secondary unit droplet 11 .

The mass (Mr) of the second unit droplet 11 that is vaporized by the vaporization amount (Mvap) in the falling primary unit droplet 1 and remains can be obtained through Equation 5 below.

Here, Md is the mass of the primary unit droplet 1 before falling.

And, the radius r1 of the secondary unit droplet 11 can be obtained through Equation 6 below. At this time, it is assumed that the secondary unit droplet 11 is also a spherical unit droplet.

Here, r is the density of the vaporized and left secondary unit droplet 11 .

The first unit droplet 1 injected into the cargo hold 100 is vaporized due to the internal temperature of the cargo hold 100 while descending to the bottom of the cargo hold 100 and the second unit droplet 11 with a reduced radius is generated. .

Thereafter, a vaporization phenomenon due to the internal temperature of the cargo hold 100 also occurs in the secondary unit droplet 11 that continues to fall, and the radius is reduced to generate the tertiary unit droplet 12 . And, this process is a reference point, that is, a point in time when the unit droplet 1 is completely vaporized and the radius r of the unit droplet 1 becomes 0, or a point in time when the unit droplet 1 reaches the bottom of the cargo hold 100 . can proceed up to.

Since the internal temperature of the cargo hold 100 is high in the beginning, all of the unit droplets 1 can be vaporized before they reach the bottom of the cargo hold 100, so the reference point for determining the total vaporization amount of the unit droplets is set as the unit droplet 1 It can be determined as a point in time when the radius r of the unit droplet 1 becomes 0 after being completely vaporized. However, when the internal temperature of the cargo hold 100 is lowered due to vaporization, the amount of vaporization is also reduced, so that the unit droplet 1 is not completely vaporized and may reach the bottom of the cargo hold 100 . Accordingly, in this case, the reference time point for determining the total vaporization amount of the unit droplet may be determined as the time point at which the unit droplet 1 reaches the bottom of the cargo hold 100 .

3 of this embodiment shows a state in which the unit droplet 1 is not completely vaporized and reaches the bottom of the cargo hold 100 in the state of the fourth unit droplet 13. In this case, the total vaporization amount of the unit droplet is determined A reference time point may be determined as a time point at which the unit droplet 1 reaches the bottom of the cargo hold 100 .

Therefore, in this case, the vaporization amount of the first unit droplet 1, the vaporization amount of the second unit droplet 11, and the vaporization amount of the tertiary unit droplet 12, which have been vaporized up to the reference time point, are added to the total of the unit droplet. The total vaporization amount can be calculated.

At this time, the section in which the unit droplet 1 falls from the inside of the cargo hold 100 includes a plurality of sub-fall sections P1, P2, and P3 that are connected to each other with the radius r of the unit droplet 1 changing. can

The total vaporization amount of the unit droplet 1 may be the sum of the vaporization amounts of each unit droplet 1 of the plurality of sub-falling sections P1 , P2 , and P3 . For convenience of explanation, only the first sub-fall section P1 , the second sub-fall section P2 , and the third sub-fall section P3 are illustrated in the present embodiment, but the present invention is not limited thereto.

During the first sub-fall section (P1), the vaporization amount of the primary unit droplet (1) occurs, during the second sub-fall section (P2), the vaporization amount of the secondary unit droplet (11) occurs, and during the third sub-fall section ( During P3), the amount of vaporization of the tertiary unit droplet 12 is generated. Accordingly, the total vaporization amount of the unit droplet 1 may be the sum of the vaporization amount of the first unit droplet 1 , the vaporization amount of the secondary unit droplet 11 , and the vaporization amount of the tertiary unit droplet 12 . .

Next, the total vaporization amount of the liquid 10 for cool-down is calculated by multiplying the total vaporization amount of the unit droplet 1 by the total number N of the unit droplets 1 ( S30 ).

The total number N of the unit droplets 1 supplied to the inside of the cargo hold 100 may be obtained through Equation 7 below.

Here, m is the total input amount of the liquid 10 for cool-down.

Next, the internal temperature of the cargo hold 100 after the first input amount of the cool-down liquid 10 is put into the cargo hold 100 is calculated using the total vaporization amount of the cool-down liquid 10 calculated above. do (S40). At this time, the internal pressure (P) of the cargo hold 100 can also be calculated.

The internal pressure P of the cargo hold 100 may be calculated using Equation 8 below.

Here, T is the internal temperature of the cargo hold, V is the internal volume of the cargo hold, n is the number of moles of gas in the cargo hold, and R is a gas constant of 0.082.

Next, the internal temperature of the cargo hold 100 and the target internal temperature of the cargo hold 100 are compared ( S50 ). The target internal temperature of the cargo hold 100 may be -130 ℃, but is not necessarily limited thereto.

At this time, when the internal temperature of the cargo hold 100 is the same as the target internal temperature of the cargo hold 100 , the first input amount of the cool-down liquid 10 injected into the cargo hold 100 is the amount of the cool-down liquid 10 . It is determined as the final input amount (S60).

However, when the internal temperature of the cargo hold 100 is greater than the target internal temperature of the cargo hold 100 , the cool-down of the cargo hold 100 is not yet completed, so the second input amount of the cool-down liquid 10 is set to the cargo hold. It is additionally put into the inside of (S70).

Then, the vaporization amount of the unit droplet 1 of the liquid 10 for cool-down having the second input amount is calculated again and the above process until the internal temperature of the cargo hold 100 is the same as the target internal temperature of the cargo hold 100 . Repeat to determine the final input amount.

As described above, the method for calculating the input amount of the liquid for cool-down according to an embodiment of the present invention calculates the total vaporization amount of the liquid for cool-down, and the liquid for cool-down at a time when the internal temperature of the cargo hold becomes the same as the target internal temperature By calculating the input amount of , it is possible to quickly calculate the input amount of the liquid for cool-down input into the cargo hold.

On the other hand, since some of the mass of the existing liquid unit droplet 1 is vaporized in the form of gas, the pressure inside the cargo hold 100 is affected by the amount of gas generated by vaporization, and at this time, the vaporized mass is added to the cargo hold The internal pressure of (100) can be calculated.

On the other hand, the internal temperature of the cargo hold 100 does not instantaneously drop even if all of the liquid required until the target internal temperature is reached.

For example, since it takes 6 hours to lower the internal temperature of the cargo hold 100 to -130° C., the amount of the liquid for cool-down may be divided by the time to evenly pour into the inside of the cargo hold 100 .

Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to carry out various modifications within the scope of the claims, the detailed description of the invention, and the accompanying drawings. It goes without saying that it falls within the scope of the invention.

1: Unit droplet 11: Second unit droplet
12: tertiary unit droplet 13: quaternary unit droplet
10: liquid for cooldown 100: cargo hold

Claims (7)

Calculating the vaporization amount of the unit droplet (1) by using a change in the radius (r) of the unit droplet (1) of the cool-down liquid (10) falling after the first input amount is put into the cargo hold (100);
calculating the total vaporization amount of the unit droplet (1) by repeating calculating the vaporization amount of the unit droplet (1) until a reference time point;
calculating the total vaporization amount of the cool-down liquid (10) by multiplying the total vaporization amount of the unit droplet (1) by the total number of the unit droplets (1);
calculating the internal temperature of the cargo hold 100 after the first input amount of the cool-down liquid 10 is put into the cargo hold 100 using the total vaporization amount of the cool-down liquid 10;
When the internal temperature of the cargo hold 100 is the same as the target internal temperature of the cargo hold 100 , the first input amount of the cool-down liquid 10 injected into the cargo hold 100 is set to the cool-down liquid 10 . ) to determine the final input amount of
A method of calculating the input amount of the liquid for cool-down comprising a. The method of claim 1,
When the calculated internal temperature of the cargo hold 100 is greater than the target internal temperature of the cargo hold 100, injecting a second input amount of the cool-down liquid 10 into the cargo hold
A method of calculating the input amount of the liquid for cool-down further comprising a. The method of claim 1,
The reference time is a time when the radius r of the unit droplet 1 becomes 0 or a time when the unit droplet 1 reaches the bottom of the cargo hold 100 . 4. The method of claim 3,
The section in which the unit droplet 1 falls within the cargo hold 100 is
The unit droplet (1) includes a plurality of sub-fall sections in which the radius (r) changes and is connected to each other,
The total vaporization amount of the unit droplet 1 is
A method of calculating the input amount of the liquid for cooldown which is the sum of the vaporization amounts of each of the unit droplets 1 in the plurality of sub-falling sections. 5. The method of claim 4,
The unit droplet (1) is a spherical unit droplet (1),
It is assumed that the size of the radius r of the unit droplet 1 decreases while descending from the point where the cool-down liquid 10 is put into the cargo hold 100 to the bottom of the cargo hold 100 . How to calculate the dosage of liquid. The method of claim 1,
The target internal temperature of the cargo hold 100 is -130 ℃ method of calculating the input amount of the liquid for cool-down. A computer-readable recording medium having recorded thereon a computer program for executing the method of calculating the input amount of the liquid for cool-down according to any one of claims 1 to 6 on a computer.

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