MULTIPATH CROSS FLOW HEAT EXCHANGER

Abstract

The present invention relates to a multipath cross flow heat exchanger and, more particularly, to a multipath cross flow heat exchanger, capable of preventing degradation of the cooling performance for cooling a superconductor which may occur when circulation of liquid nitrogen in a circulation tube is not efficient, by forming a cooling tube, in which a refrigerant for cooling liquid nitrogen flows, to intersect multiple times with the circulation tube, in which the liquid nitrogen is circulated, to thereby freeze the liquid nitrogen by the refrigerant.

Description

TECHNICAL FIELD

The present invention relates to a multipath cross flow heat exchanger and, more particularly, to a multipath cross flow heat exchanger, capable of preventing degradation of the cooling performance for cooling a superconductor which may occur when circulation of liquid nitrogen in a circulation tube is not efficient, by forming a cooling tube, in which a refrigerant for cooling liquid nitrogen flows, to intersect multiple times with the circulation tube, in which the liquid nitrogen is circulated, to thereby freeze the liquid nitrogen by the refrigerant.

The present application claims the benefit of Korean Patent Application No. 10-2013-0082388, filed on Jul. 12, 2013, the contents of which are entirely incorporated herein by reference.

BACKGROUND ART

As well known to those skilled in the art, a superconductor is a conductor showing superconductivity, a phenomenon wherein near-zero electrical resistance can be reached at a very low temperature. Magnetic fields cannot penetrate into the superconductor, and magnetic fields already present therein are expulsed, thereby producing a magnetic levitation effect when placed over a magnet.

The superconductor having such a property may be used in various fields such as a fault current limiter controlling electric power, magnetic levitation technology, and power transmission.

Particularly, in the field of power transmission, as the length of a superconducting cable increases, heat transfer thereto from outside increases, and when alternating current flows in the superconducting cable, the temperature thereof increases, thereby generating power loss and increasing cooling load.

That is, to maintain the near-zero electrical resistance of the superconductor, it is important to maintain the superconductor at an ultra-low temperature by cooling the superconductor.

As described above, to maintain a superconducting device at ultra-low temperature, liquid nitrogen at an ultra-low temperature for cooling the superconducting cable is used, and heat exchange between the liquid nitrogen and the superconducting cable increases the temperature of the liquid nitrogen, and thus it is required to have an additional cooling system for cooling the liquid nitrogen.

An example of prior art documents related to the present invention may be referred to Korean Patent No. 10-0124825 (Published on Dec. 3, 2009, entitled Cooling system for a superconducting fault current limiter using solid cryogens).

DISCLOSURE

Technical Problem

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a multipath cross flow heat exchanger constructed in such a manner that a cooling tube, in which a refrigerant for cooling a cooling fluid flows, intersects multiple times the circulation tube in which the cooling fluid for cooling a superconducting cable flows, thereby preventing the cooling fluid from freezing and the cooling performance of the cooling fluid from degrading.

An object of the present invention having the above-mentioned construction is to provide a heat exchanger that does not require the installation of a heater for preventing the cooling fluid from freezing.

Technical Solution

In order to accomplish the above object, the present invention provides a multi-path cross flow heat exchanger including: a circulation tube in which cooling fluid for cooling a superconducting cable flows; and a cooling tube defining a flowing path intersecting the circulation tube multiple times and in which a refrigerant that exchanges heat with the cooling fluid flows.

The circulation tube and the cooling tube may intersect each other while being isolated from each other so that the cooling fluid in the circulation tube and the refrigerant in the cooling tube are prevented from being mixed together.

The cooling tube may be constructed in such a manner that when the cooling fluid flows from a first end to a second end of the circulation tube, a position at which the refrigerant flowing in the cooling tube primarily intersects the circulation tube is located at the second end of the circulation tube, and another position at which the refrigerant completing heat exchange with the cooling fluid in the cooling tube secondarily intersects the circulation tube is located at the first end of the circulation tube.

The cooling tube may be constructed to have a diameter larger than a diameter of the circulation tube, and the circulation tube is located in the cooling tube at positions at which the circulation tube and the cooling tube intersect each other, so that heat exchange between the cooling fluid and the refrigerant occurs on an outer surface of the circulation tube at portions at which the circulation tube intersects the cooling tube.

The cooling tube may include: a body part having a housing-shaped structure and defining a space part therein, the space part including a predetermined part of the circulation tube; a supply part provided on a position of an outer surface of the body part and supplying the refrigerant to the space part; and a discharge part provided on another position of an outer surface of the body part and through which the refrigerant supplied to the space part is discharged.

The circulation tube may be divided into multiple branch tubes in an area at which the circulation tube intersects the cooling tube, wherein each of the multiple branch tubes has a diameter smaller than the diameter of the circulation tube.

The supply part and the discharge part may be located at one side based on the circulation tube passing through the body part, and be spaced apart from each other on an outer surface of the cooling tube.

The body part may further include: a partition wall arranged in the space part defined in the body part at a location between the supply part and the discharge part, wherein the partition wall is provided with an opening part through which the refrigerant passes such that the refrigerant supplied to the space part through the supply part can be discharged through the discharge part.

Advantageous Effects

As described above, the present invention has an advantage preventing the cooling fluid from being frozen and the cooling performance of the cooling fluid from degrading.

Accordingly, the present invention has another advantage in that it does not require installing a heater for preventing the cooling fluid from freezing

DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing the first embodiment of the multipath cross flow heat exchanger according to the present invention;

FIG. 2 is a schematic diagram showing heat exchange of the second embodiment of the multipath cross flow heat exchanger according to the present invention;

FIG. 3 is a view showing various embodiments of the multipath cross flow heat exchanger according to the present invention;

FIG. 4 is a view showing the outline of a cooling fluid behavior and the distribution of the cooling fluid temperature of the multipath cross flow heat exchanger according to the present invention;

FIG. 5 is a view showing the outline of a cooling fluid behavior and the distribution of the cooling fluid temperature of a parallel-flow heat exchanger; and

FIG. 6 is a view showing the outline of a cooling fluid behavior and the distribution of the cooling fluid temperature of a cross flow heat exchanger.

MODE FOR INVENTION

The present invention will be described in detail below with reference to the accompanying drawings.

Here, repeated descriptions and descriptions of known functions and configurations that have been deemed to make the gist of the present invention unnecessarily obscure will be omitted below.

And the embodiments of the present invention are intended to fully describe the present invention to a person having ordinary knowledge in the art to which the present invention pertains.

Accordingly, the shapes, sizes, etc. of components in the drawings may be exaggerated to make the description clearer.

FIG. 1 is a view showing the first embodiment of the multipath cross flow heat exchanger according to the present invention.

Referring to FIG. 1, the multipath cross flow heat exchanger according to the present invention includes: a circulation tube 100 in which cooling fluid for cooling a superconducting cable flows; and a cooling tube 200 defining a flowing path intersecting the circulation tube 100 multiple times and in which a refrigerant that exchanges heat with the cooling fluid flows.

Here, the following describes a heat exchange process through which the cooling fluid is deprived of heat by the refrigerant while the circulation tube 100 and the cooling tube 200 intersect each other. The circulation tube and the cooling tube intersect each other while being isolated from each other so that the cooling fluid in the circulation tube 100 and the refrigerant in the cooling tube 200 are prevented from being mixed together.

That is, the cooling fluid and the refrigerant are prevented from being mixed together and heat exchange occurs at the circulation tube 100 in which the cooling fluid flows.

The circulation tube 100 and the cooling tube 200 can exchange heat with each other in the following configuration.

The cooling tube 200 includes: a body part 210 having a housing-shaped structure and defining a space part S therein, the space part S including a predetermined part of the circulation tube 100; a supply part 220 provided on a position of an outer surface of the body part 210 and supplying the refrigerant to the space part S; and a discharge part 230 provided on another position of an outer surface of the body part 210 and through which the refrigerant supplied to the space part S is discharged.

As illustrated in FIG. 1, the supply part 220 and the discharge part 230 are located at one side (the same side) based on the circulation tube 100 passing through the body part 210, and are spaced apart from each other on an outer surface of the cooling tube.

The following details describe the heat exchange process of the heat exchanger of the present invention described in FIG. 1 as a first embodiment. The cooling fluid flows from the left side to the right side of the circulation tube 100, and the refrigerant is supplied to the body part through the supply part 220, and the refrigerant is in thermal contact with the outer surface of the circulation tube 100 in the body part 210, thereby exchanging heat with the cooling fluid flowing in the circulation tube and being discharged through the discharge part 230.

By using the heat exchanger having the above-mentioned construction according to the present invention, the heat exchanger can prevent the cooling fluid from freezing and can maintain efficient cooling performance of the cooling fluid. The heat exchange process is described further in detail below.

FIG. 2 is a schematic diagram showing heat exchange of the second embodiment of the multipath cross flow heat exchanger according to the present invention.

Referring to FIG. 2, the cooling tube 200 is constructed in such a manner that when the cooling fluid flows from a first end to a second end of the circulation tube 100, a position P1 at which the refrigerant flowing in the cooling tube 200 primarily intersects the circulation tube 100 is located at the second end of the circulation tube 100, and another position P2, at which the refrigerant completing heat exchange with the cooling fluid in the cooling tube 200, secondly intersects the circulation tube 100, is located at the first end of the circulation tube 100.

As shown in FIG. 2, the circulation tube 100 is divided into multiple branch tubes 110 in an area at which the circulation tube 100 intersects the cooling tube 200, wherein each of the multiple branch tubes has a diameter smaller than the diameter of the circulation tube 100.

As described above, the multiple branch tubes 110 are selectively connected to the circulation tube 100 according to the requirements of facilities using the superconducting cable, thereby increasing the efficiency of the cooling performance of the heat exchanger.

In addition, the body part 210 further comprises: a partition wall 240 arranged in the space part S defined in the body part at a location between the supply part 220 and the discharge part 230, wherein the partition wall 240 is provided with an opening part 241 through which the refrigerant passes such that the refrigerant supplied to the space part S through the supply part can be discharged through the discharge part 230.

That is, referring to FIG. 2, the refrigerant flows in an “∩” shape in the space part S, thereby cooling the cooling fluid.

Referring to FIG. 2, the following details describe the heat exchange process of the second embodiment of the multipath cross flow heat exchanger. The cooling fluid for cooling the superconducting cable flows from the left side to the right side of the circulation tube 100 to pass through the body part 210 of the cooling tube 200.

As illustrated in FIG. 2, the circulation tube may be divided into multiple branch tubes 110 in the body part 210 when it is desired.

The refrigerant for cooling the cooling fluid flows into the body part 210, or the space part S through the supply part 220.

The refrigerant first exchanges heat with the cooling fluid on the outer surface of the circulation tube 100 at the position P1 in the space part S, thereby first cooling the cooling fluid.

The refrigerant passing through the position P1 changes its flowing direction to the left side of the circulation tube 100 while hitting the inner wall of the body part 210, and the refrigerant changing its flowing direction passes through the position P2 in the space part S, thereby secondarily exchanging heat with the cooling fluid and being discharged from the body part 210 through the discharge part 230.

The multipath cross flow heat exchanger according to the present invention may be designed in the following various embodiments according to cooling performance required in facilities for cooling the superconducting cable.

FIG. 3 is a view showing various embodiments of the multipath cross flow heat exchanger according to the present invention.

As described above, FIG. 3a is a view showing an embodiment of a structure constructed in such a manner that a cooling fluid and a refrigerant first exchange heat at the position P1 and second exchange heat at the position P2.

A detailed description of the above-mentioned heat exchange process is omitted since it is the same as described above.

FIG. 3b is a view showing another embodiment of the structure constructed in such a manner that the refrigerant passing through the position P2 is not discharged through a discharge part 230 but the refrigerant changes its flowing direction again, thereby exchanging heat with the cooling fluid three times prior to being discharged through the discharge part 230.

As illustrated in FIG. 3b, FIG. 3c is a view showing still another embodiment of the structure constructed in such a manner that the refrigerant supplied to a space part S through a supply part 220 intersects a circulation tube 100 four times in the space part, thereby exchanging heat with the cooling fluid four times.

FIG. 4 is a view outlining the cooling fluid behavior and the distribution of the cooling fluid temperature of the multipath cross flow heat exchanger according to the present invention, FIG. 5 is a view outlining the cooling fluid behavior and the distribution of the cooling fluid temperature of a parallel-flow heat exchanger, and FIG. 6 is a view outlining the cooling fluid behavior and the distribution of the cooling fluid temperature of a cross flow heat exchanger.

First, FIG. 4 is a view showing the cooling fluid behavior and the distribution of the cooling fluid temperature of the multipath cross flow heat exchanger according to the present invention, and shows that in a normal load state, liquid nitrogen can efficiently flow without freezing in the circulation tube 100.

Here, temperature distribution lines (unit: absolute temperature, K) are concentrated around the supply part 220 through which the refrigerant begins to be supplied, and the lowest temperature is 64K, and thus the liquid nitrogen can efficiently flow without freezing

In a low-load state, the lowest temperature around the supply part 220 is 63K, and an area indicating 63K is such a small frozen area that the liquid nitrogen is not prevented from flowing in the circulation tube 100.

A parallel-flow method shown in FIG. 5, which is generally used, refers to the method operated in such a manner that liquid nitrogen in a circulation tube 100 flows in a direction contrary to a refrigerant in a cooling tube 200. The parallel-flow method is excellent in cooling efficiency, and thus it is widely used.

As shown in FIG. 5, in the parallel-flow method, the liquid nitrogen efficiently flows without freezing in a normal load state. However, in a low-load state, the lowest temperature approaches 62K, and the liquid nitrogen is frozen in a 62K area or an area lower than 62K, including temperature distribution lines around 63K.

Accordingly, compared to the frozen area of the low-load state of FIG. 4, the liquid nitrogen in the low-load state of the parallel-flow method is frozen in areas ranging from 62K to 63K in the circulation tube 100, so that the liquid nitrogen is prevented from flowing in the circulation tube 100.

FIG. 6 shows the cross flow heat exchanger constructed in such a manner that a refrigerant in a cooling tube 200 flows in a direction perpendicular to liquid nitrogen in a circulation tube 100.

In the cross flow heat exchanger, as shown in FIG. 6, even in a normal load state, a frozen area is formed in which some of the liquid nitrogen is frozen in the circulation tube 100. Even in a normal load state, the frozen area of the liquid nitrogen in the cross flow heat exchanger is larger than the frozen area of the liquid nitrogen in the multipath cross flow heat exchanger in the low-load state according to the present invention shown in FIG. 4.

As described above, in the cross flow heat exchanger, a flowing area as much as or more than ⅓ thereof is frozen even in the normal load state, thereby the liquid nitrogen being prevented from flowing in the circulation tube 100, and if the cross flow heat exchanger in the state continues to be operated, it is required to install and operate at all times an additional heater for safety.

In the cross flow heat exchanger, it is shown that the amount of frozen liquid nitrogen in the low-load state is more than the amount of liquid nitrogen in the normal load state.

As described above, by using the multipath cross flow heat exchanger according to the present invention, the liquid nitrogen in the normal load state is prevented from freezing in the circulation tube 100. And even the liquid nitrogen in the low-load state is frozen in a very small area, so that the liquid nitrogen is not prevented from flowing in the circulation tube 100, thereby realizing the efficient flow of the liquid nitrogen and preventing the cooling performance for cooling the superconducting cable from degrading.

Additionally, the frozen area of the liquid nitrogen is so small that it is not required to install an additional heater to heat the circulation tube 100 to solve the problems, thereby increasing the efficiency of a cooling system, and removing or decreasing energy consumption caused by operating the heater.

Although a preferred embodiment of the present invention has been described for illustrative purposes, the spirit of the present invention is not limited to the accompanying drawings and the above-mentioned description, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A multipath cross flow heat exchanger comprising: a circulation tube in which cooling fluid for cooling a superconducting cable flows; anda cooling tube defining a flowing path intersecting the circulation tube multiple times and in which a refrigerant that exchanges heat with the cooling fluid flows.

2. The multipath cross flow heat exchanger of claim 1, wherein the circulation tube and the cooling tube intersect each other while being isolated from each other so that the cooling fluid in the circulation tube and the refrigerant in the cooling tube are prevented from being mixed together.

3. The multipath cross flow heat exchanger of claim 1, wherein the cooling tube is constructed in such a manner that when the cooling fluid flows from a first end to a second end of the circulation tube, a position at which the refrigerant flowing in the cooling tube primarily intersects the circulation tube is located at the second end of the circulation tube, and another position at which the refrigerant completing heat exchange with the cooling fluid in the cooling tube secondarily intersects the circulation tube is located at the first end of the circulation tube.

4. The multipath cross flow heat exchanger of claim 1, wherein the cooling tube is constructed to have a diameter larger than a diameter of the circulation tube, and the circulation tube is located in the cooling tube at positions at which the circulation tube and the cooling tube intersect each other, so that heat exchange between the cooling fluid and the refrigerant occurs at an outer surface of the circulation tube at portions at which the circulation tube intersects the cooling tube.

5. The multipath cross flow heat exchanger of claim 1, wherein the cooling tube comprises: a body part having a housing-shaped structure and defining a space part therein, the space part including a predetermined part of the circulation tube;a supply part provided on a position of an outer surface of the body part and supplying the refrigerant to the space part; anda discharge part provided on another position of an outer surface of the body part and through which the refrigerant supplied to the space part is discharged.

6. The multipath cross flow heat exchanger of claim 5, wherein the circulation tube is divided into multiple branch tubes in an area at which the circulation tube intersects the cooling tube, wherein each of the multiple branch tubes has a diameter smaller than the diameter of the circulation tube.

7. The multipath cross flow heat exchanger of claim 5, wherein the supply part and the discharge part are located at one side based on the circulation tube passing through the body part, and are spaced apart from each other on an outer surface of the cooling tube.

8. The multipath cross flow heat exchanger of claim 6, wherein the body part further comprises: a partition wall arranged in the space part defined in the body part at a location between the supply part and the discharge part, wherein the partition wall is provided with an opening part through which the refrigerant passes such that the refrigerant supplied to the space part through the supply part can be discharged through the discharge part.