JPH04313686A - Heat exchange unit - Google Patents

Abstract

PURPOSE:To enhance the efficiency of heat exchange by increasing the flow rate of a secondary fluid (air) from that inlet side of a tube which a primary fluid (refrigerant) enters to the outlet side from which the secondary fluid leaves in structure and increasing the flow rate of the secondary fluid in inverse proportion to the differential temperature between the fluids. CONSTITUTION:A tower main body 1 is built-in with heat exchangers 5 and 6 which cools or heats refrigerant based on the application of air. The air from the lower end sections of the heat exchangers 5 and 6 flow past tubes 5 and 6 and flow through a tapered flow passage at the tip of pipe rows with minimum air resistance, which increases the velocity of the air flowing past the tubes 5 and 6 laid out on the upper end side faster than that on the lower end side. On the other hand, the temperature of the refrigerant flowing past the tubes 5 and 6 is increased gradually so that heat transfer may be gradually attenuated. The velocity of the air is more increased on the upper end side of the tubes 5b and 6b while the flow rate is maintained to a satisfactory extent, which makes it possible to inhibit a drop in the efficiency of heat exchange and hence a high efficiency of heat exchange may be maintained on the whole.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a heat exchange unit using heat transfer tubes used in air heat exchangers such as refrigerators, closed cooling towers, or heating towers, and particularly relates to a heat exchange unit using heat transfer tubes used in air heat exchangers such as refrigerators, closed cooling towers, or heating towers, and particularly relates to cross-flow type heat exchangers. The present invention relates to a structure of a heat exchanger that improves the heat exchange efficiency of the heat exchanger and prevents a decrease in efficiency due to frost formation on the surfaces of heat exchanger tubes and other members.

0002

[Prior Art] Conventionally, cooling towers or heating towers for air conditioning, air heat exchangers for refrigerators, etc. pass internal fluid through a large number of pipes, and air from the outside flows around these pipes to heat or heat the tower. Cooling structures are common. The heat transfer method for heating or cooling is classified into a countercurrent type, a parallel flow type, and a cross flow type. The counterflow type exchanges heat by flowing air in the opposite direction to the flow direction of the internal fluid passing through the pipe, while the parallel flow type, on the other hand, exchanges heat between the internal fluid and air. The flow direction is the same. Further, the cross-flow type is a method in which air flows perpendicularly across the flow direction of the internal fluid.

[0003] Among these various methods, the countercurrent type has the highest heat exchange efficiency, followed by the crossflow type and the parallel flow type, and is currently the most commonly used in air conditioning and industrial equipment. The one that is used is a countercurrent type.

In the case of a countercurrent heat exchanger, when the internal fluid flowing through the tube is below zero and is heated with high-temperature air, the air cools down at the inlet side of the internal fluid where the temperature is lowest. When the temperature drops below the dew point, frost forms on the tube surface. For this reason, the air flow path between the tubes becomes narrow, flow path resistance increases, and the air flow rate is also restricted, resulting in a decrease in heat exchange efficiency.

[0005]

[Problems to be Solved by the Invention] On the other hand, although a similar frosting phenomenon occurs in cross-flow type heat exchangers, it is known that the degree of frost formation is less than in counter-flow type heat exchangers. For example, if the heat exchange part is horizontal and the heat exchanger tube is meandering so that the internal fluid flows upward and the air also flows from the bottom to the top, this applies only to the heat exchanger tube at the bottom end where the temperature difference is greatest. This is because frost formation occurs. On the other hand, in the case of a countercurrent type, since the internal fluid and the air flow face each other, frost often forms on the entire heat exchanger tube, reducing the air flow rate and reducing the heat exchange efficiency.

However, even if the problem of frost formation is small,
As mentioned above, the cross-flow type is inferior to the counter-flow type in terms of heat exchange efficiency itself. For this reason, if the installation environment is such that the occurrence of frost formation is expected to be low, a counter-current type is preferable, but in reality, this type of frost formation is a major problem, so
It is not a good idea to select a countercurrent type solely from the standpoint of heat exchange efficiency.

[0007] In the case of a cross-flow type, there are fewer problems due to frost formation, but there is a limit to the improvement in heat exchange efficiency. For this reason, there are restrictions on the temperature and flow rate of the internal fluid, installation conditions, etc., and if an attempt is made to operate with high heat exchange efficiency, it can only be used for limited applications. In a cross-flow type heat exchanger, an external fluid, such as air, passing through the heat exchanger tubes has a uniform flow rate around all the heat exchanger tubes. Therefore, in a region where the temperature difference between the internal fluid and the air is small, the heat transfer efficiency cannot be maintained unless the air flow rate is increased, and if the flow rate is uniform, the efficiency inevitably decreases.

The problem to be solved by the present invention is to provide a cross-flow type heat exchanger that maintains the same thermal efficiency as a counter-flow type and suppresses a decrease in thermal efficiency due to frost formation.

[0009]

[Means for Solving the Problems] The present invention is incorporated into an air heat exchanger such as a refrigerator or a tower body of a cooling tower or a heating tower, circulates a primary fluid from the refrigerator, etc., and converts the primary fluid into air, etc. A heat exchange unit equipped with a heat exchanger for externally heating or cooling with a secondary fluid, the heat exchanger increasing the passage resistance of the secondary fluid from the inlet side to the outlet side of the primary fluid. A cross-flow type with a meandering tube that is small and orthogonal to the flow of the primary fluid and the secondary fluid, and the flow rate of the secondary fluid is increased from the side where the primary fluid enters the tube to the side where it exits. It is characterized by having a flow rate distribution.

[0010] In addition, two heat exchangers are combined into one pair, and the inlet side of the primary fluid tube is opened and the outlet side is narrowed, and the outlet side of the heat exchanger is formed in an open-air shape. It is also possible to adopt a configuration in which the primary fluid and the secondary fluid exit in the same direction.

[0011]

[Operation] In a cross-flow type heat exchanger, the temperature difference between the primary fluid and the secondary fluid is the largest when entering the tube, and is the smallest when exiting the tube. Therefore, heat transfer decreases in areas where the temperature difference is small, but in the present invention, the flow rate of the secondary fluid is large, so there is no shortage of heat transfer. Therefore, heat exchange efficiency is maintained at a high level, and since frost only forms on the tube on the entry side of the primary fluid, the entire air flow rate is not restricted, further improving heat exchange efficiency. It will be done.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing a heat exchange tower which is equipped with a heat exchanger of the present invention and can be used for both cooling and heating.

In the figure, the heat exchange tower is equipped with a louver 2 for sucking air on the peripheral wall of the bottom side of the tower body 1, and a fan 3 is installed at the upper end for sucking in air through the louver 2 and discharging it. . Furthermore, in preparation for use as a cooling tower, a nozzle head 4 for spraying water is incorporated in the upper end side.

Heat exchangers 5 and 6 are installed inside the tower body 1 to heat or cool an air conditioning refrigerant or steam, a refrigerant for a refrigerator, etc. using the air sucked from the louvers 2. FIG. 2 is a schematic perspective view showing how these heat exchangers 5 and 6 are assembled, and FIG. 3 is a side view of one heat exchanger 5.

The heat exchangers 5 and 6 are provided with a pair of headers 5a and 6a spaced apart in the depth direction in FIG.
is connected to the piping. In one header 5a, 6a,
Inflow ports 5c and 6c are provided for supplying fluid to be heated or cooled, and reflux ports 5d and 6 are provided for returning the fluid after heat exchange to the circulation system.
Provide d. Note that the tube 5b is provided with appropriate fins 5e for promoting heat transfer, and the other tube 6b is provided with appropriate fins 5e for promoting heat transfer.
The same is true.

As shown in FIG. 3, the heat exchanger 5 has tubes 5b arranged in a meandering manner between two headers 5a. In this figure, one tube is shown for ease of explanation. It is depicted as 5b. On the other hand, in reality, a plurality of tubes 5b are arranged in the longitudinal and width directions of the header 5a, as shown in FIG. The header 5a has partition walls 5a-1, 5a-2, 5a-3.
The interior is divided into a plurality of chambers, and a tube 5b is connected to each chamber. Note that the other heat exchanger 6 is also shown in FIG.
It has a similar structure to that of .

The heat exchangers 5 and 6, which are assembled as a pair inside the tower body 1, are assembled in an inverted V shape by abutting the upper ends of the respective headers 5a and 6a, as shown in FIG. . At this time, since only the tubes 5b and 6b are installed between the headers 5a and 6a, as shown in FIG.
As can be seen from FIG. 2, the space sandwiched between the heat exchangers 5 and 6 has a substantially triangular cross-section and an open upper end.

In the above configuration, heat exchange when a refrigerant below zero degrees Celsius is circulated and supplied to the heat exchangers 5 and 6 and used as a heating tower for heating with air will be described below.

Inside the tower body 1, air is forced upward from the louver 2 at the bottom by the suction force of the fan 3. On the other hand, the refrigerant is supplied to the heat exchangers 5 and 6 from the inflow ports 5c and 6c at the lower ends thereof, and flows through the tubes 5b and 6b by forced circulation, and when viewed from the whole of the heat exchangers 5 and 6, The flow is upward.

In such a flow of air and refrigerant, the portions having the lowest temperature due to the refrigerant supplied to the heat exchangers 5 and 6 are the inlets 5c and 6c and the tube 5 directly connected thereto.
This is the lower end side of the rows b and 6b. For this reason, during the heating process using air, frost formation is concentrated on the lower end portions of the heat exchangers 5 and 6. This kind of frost formation can be seen, for example, in Figure 3.
Most of the frost is generated in the tubes 5b running at the lower end of the header 5a, and as the refrigerant in the tubes 5b arranged above is gradually heated, the amount of frost is gradually reduced. For this reason, as explained in the conventional example, with a counter-flow type, frost forms on the entire heat transfer surface on the low-temperature primary fluid inlet side, blocking the entire air flow path, but with a cross-flow type, frost forms. The area is only a part of the air flow path. Therefore, the flow rate of the air flowing through the tube 5b is not restricted, and the heat exchange efficiency is maintained high.

Further, as shown in FIG. 1, air passes between the tubes 5b and 6b of the heat exchangers 5 and 6, resulting in orthogonal heat exchange. Air from the lower ends of the heat exchangers 5 and 6 passes between the tubes 5b and 6b due to the arrangement of the tubes 5b and 6b, and also flows through the tapered flow path cross section with low air resistance of the tube row at the tip. flows. Therefore, the flow velocity of the air passing between the tubes 5b and 6b arranged on the upper end side is faster than that flowing between the rows of tubes 5b and 6b on the lower end side. Therefore, with respect to the tubes 5b and 6b arranged vertically, the velocity distribution becomes such that the flow velocity of the air increases from the lower end side to the upper end side.

On the other hand, the tubes 5b and 6 of the heat exchangers 5 and 6
The refrigerant flowing through b is gradually heated by the air as it flows upward, and the temperature difference between the refrigerant and the air gradually becomes smaller. Therefore, the heat transfer from the air to the refrigerant also decreases, but the tubes 5b and 6b
Since the air flow velocity is high on the upper end side of the arrangement, a sufficient flow rate is ensured, and a decrease in heat exchange efficiency can be suppressed. That is, since the air flow rate increases in inverse proportion to the decrease in temperature difference, there is no decrease in heat transfer coefficient, the overall heat exchange efficiency is maintained high, and efficient heat exchange is possible.

It should be noted that the air flow velocity is lower at the lower ends of the heat exchangers 5 and 6 than in the upper regions. However, since this is the part where the temperature difference between the air and the refrigerant is greatest, heat exchange between the fluids is performed well even when the flow rate of air is small. Therefore, efficient heat exchange can be achieved even in areas where frost formation is expected.

Next, consider the case where the fluid sent to the heat exchangers 5 and 6 is used as a cooling tower in which air and water sprayed from the nozzle head 4 are used to cool the fluid.

In the case of this cooling tower, the air and the spray water flow in opposite directions, and the spray water and the cooling fluid flowing through the heat exchangers 5 and 6 also flow in opposite directions. As mentioned above, the speed of the air is gradually increased in the flow that blows upward from the lower ends of the heat exchangers 5 and 6, so that at the lower end side, the slow-flowing air and the spray water have a large temperature difference. Good heat exchange occurs between the fluids. Further, although the temperature difference between the upper end side and the cooling fluid becomes smaller, since the air containing the spray water flows at an increased speed, the heat exchange efficiency is maintained high and the heat exchange efficiency does not decrease.

FIG. 4 shows another embodiment in which four heat exchangers 5 to 8 are arranged in parallel. As shown in the figure, pairs of heat exchangers 5, 6 and 7, 8 are arranged in an inverted V shape with their upper ends abutting each other. The rest of the structure is the same as that shown in FIG. 1, and has twice the heat exchange capacity. In addition, 1a is a water scattering prevention eliminator.

FIG. 5 also shows one heat exchanger 5 connected to the tower body 1.
FIG. The heat exchanger 5 is disposed obliquely in the tower body 1, and circulates heating or cooling fluid in the direction shown by the dashed line in the figure from the inlet 5c at the lower end toward the reflux port 5d. The air flow is also similar to that shown in the right half of FIG. 1, and the heat exchange efficiency can be improved by increasing the air flow velocity toward the top.

Furthermore, FIG. 6 shows the four heat exchangers 5 to 8 of FIG.
This figure shows a skeleton diagram in which similar heat exchangers 9 to 12 are arranged in addition to the heat exchangers 9 to 12 below. In this way, the heat exchanger 9
-12 can also be incorporated as two or more stages in the air flow direction.

Furthermore, FIG. 7 shows an example in which a plurality of heat exchangers 10 are arranged horizontally.

[0030] In this way, by using two heat exchangers as a basis, which are paired together in order to increase the speed of the air flowing inside, various layouts of the heat exchangers can be made freely. For example, as shown in FIG. 8, by preparing heat exchangers 11 of the same size and arranging two of them in an inverted V shape, various specifications of the heat exchangers can be easily changed. Furthermore, space can be saved by improving heat exchange efficiency.

[0031]

[Effects of the Invention] In the present invention, in a cross-flow type heat exchanger through which the primary fluid to be heated or cooled flows, the secondary fluid such as air that heats or cools the primary fluid is inversely proportional to the temperature difference between the fluids. The flow rate of the secondary fluid can be increased by For this reason, compared to the case where heat is exchanged by a secondary fluid with a uniform flow rate around a group of heat transfer tubes in a cross-flow type heat exchanger, the amount of heat transferred, which is affected by the temperature difference between the fluids, is attenuated. High heat exchange efficiency can be obtained. Further, since frost occurs only in a part of the group of tubes, the degree of influence on the flow velocity of the secondary fluid is small, and high heat exchange efficiency can be maintained at all times. By achieving such high heat exchange efficiency, it becomes possible to make the heat exchanger more compact, which greatly contributes to space saving.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a tower body that is equipped with a heat exchanger of the present invention and can be used as a heating or cooling tower.

FIG. 2 is a schematic perspective view showing a combination of heat exchangers.

FIG. 3 is a side view showing the flow of fluid and air inside the heat exchanger.

FIG. 4 is a schematic diagram of a column body with four heat exchangers.

FIG. 5 is a schematic diagram showing an example in which one heat exchanger is disposed within the tower body.

FIG. 6 is a schematic diagram showing an example in which four heat exchangers each provided in the tower body are arranged in two stages.

FIG. 7 is a schematic diagram showing another arrangement of heat exchangers.

FIG. 8 is a schematic diagram showing a heat exchanger layout based on a combination of two heat exchangers. 1 Tower body 1a Water scattering prevention eliminator 2 Louver 3 Fan 4 Nozzle head 5 Heat exchanger 5a Header 5b Tube 5c Inlet 5d Reflux port 6 Heat exchanger 6a Header 6b Tube 6c Inlet 6d Reflux port

Claims (2)

[Claims] Claim 1: It is built into an air heat exchanger such as a refrigerator or the tower body of a cooling tower or a heating tower, circulates a primary fluid from the refrigerator, etc., and heats the primary fluid from the outside with a secondary fluid such as air. Or a heat exchange unit equipped with a heat exchanger for cooling, wherein the heat exchanger reduces the passage resistance of the secondary fluid from the inlet side to the outlet side of the primary fluid and connects the primary fluid and the secondary fluid. A cross-flow type having meandering tubes that orthogonally intersect the flow of the fluid, and a flow rate distribution that increases the flow rate of the secondary fluid from the side where the primary fluid enters the tube to the side where the secondary fluid exits the tube. Features a heat exchange unit. [Claim 2] A combination of two of the heat exchangers is made into one pair, and the arrangement is such that the inlet side portion of the primary fluid into the tube is opened and the outlet side portion is narrowed, and the outlet side heat exchanger portion is further narrowed. 2. The heat exchange unit according to claim 1, wherein the heat exchange unit has an open-air shape, and the outlet sides of the primary fluid and the secondary fluid are directed in the same direction.