JPH04332391A - Heat exchanger - Google Patents

Abstract

PURPOSE:To maintain and or increase the overcooling degree of a heat transfer tube and prevent the blockading of a flow passage due to freezing. CONSTITUTION:A flow passage forming body 21 is inserted into a heat transfer tube 20. The flow passage of cold heat accumulating material W is formed cylindrically between the flow passage forming body 21 and the inner peripheral wall of the heat transfer tube 20. A spiral projection 22, formed on the outer periphery of the flow passage forming body 21, changes the flow of the cold heat accumulating material W into whirling flow. The flow of the cold heat accumulating material W is pushed against the inner peripheral wall of the heat transfer tube 20 by the centrifugal force of the whirling flow whereby disturbance is hardly generated and the flow of the cold heat accumulating material W is stabilized.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applied to a heat exchanger used in an ice heat storage device, etc., which circulates and supercools the cold storage material in an ice storage tank, and then eliminates the supercooled state and converts it into a slurry-like frozen product. Regarding measures to prevent freezing of heat exchangers.

0002

2. Description of the Related Art In recent years, thermal storage air conditioning systems have been used in relatively large-scale air conditioning systems in industrial plants, buildings, and the like. A supercooling control type ice heat storage device is known as a device used in a heat storage air conditioning system.

[0003] This supercooling control type ice heat storage device has a circulation path for circulating the cold storage material in the ice storage tank between a heat exchanger connected to the cooling device and the ice storage tank, and the ice storage material is stored by the heat exchanger. After cooling the cold storage material in the ice tank, the supercooled state is eliminated and the slurry is
It is used to make ice cubes.

[0004] As a heat exchanger for supercooling, for example, U
The ice heat storage devices disclosed in SP4401449, USP4671077, and JP-A-63-14064 are of the well-known multi-tube type (shell-type).
and-tube type) heat exchangers are used. A refrigerant or brine as a low-temperature heat medium is passed through the shell, while water is passed through a large number of heat transfer tubes disposed inside the shell, and the water is supercooled by the refrigerant or brine.

[0005]

When designing heat exchangers, it is generally advantageous to disrupt the flow of water within the heat exchanger tubes. This is because heat exchange between the fluid near the tube wall and the mainstream fluid due to the turbulence results in effective heat transfer.

However, the above-mentioned heat exchanger intended for supercooling has a problem in that the flow path becomes clogged when severe turbulence occurs. In other words, supercooled water is unstable;
Even with the slightest stimulus, the supercooled state can be overcome and freezing can easily begin. The elimination of the supercooled state also occurs due to severe turbulence that occurs in the flow of water within the heat transfer tube. Once icing begins, ice adheres to the tube wall of the heat transfer tube and forms an icing layer, and if the icing layer becomes even thicker, it blocks the flow path, and the heat transfer tubes are further damaged by the expansion pressure of the ice. A problem arises.

[0007] As a way to solve this problem, it is possible to prevent ice from forming by keeping the temperature of the heat exchanger tube at a relatively high value without lowering the temperature of the low-temperature heat medium on the outside of the heat exchanger tube too much. Conceivable. However, in this method, the degree of supercooling ΔTsc of water (indicating the degree to which the cooling temperature T is lower than the freezing point Tf, ΔTsc=|T−Tf|
) is small, the amount of ice made per cycle is small, and the amount of ice made per unit time is reduced. Therefore, in order to secure the amount of ice storage necessary for daytime air conditioning, a problem arises in that the heat exchanger must be scaled up.

[0008] The present invention has been made in view of these points, and its purpose is to maintain and even increase the degree of supercooling of heat exchanger tubes, and to prevent freezing and blockage of flow passages.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the means taken by the present invention is to form a flow path for a cold storage material flowing inside a heat transfer tube into a cylindrical shape along the inner circumferential wall of the heat transfer tube. A protrusion is provided on the channel forming body and either the outer periphery of the channel forming body or the inner periphery of the heat transfer tube to create a spiral swirl flow in the regenerator material flowing through the channel set by the channel forming body. It is something.

Specifically, the solution of the present invention is as shown in FIG.
As shown in the solid line portion only), an outer flow path (11) through which a low-temperature heat medium flows, and an outer flow path (11) disposed within the outer flow path (11),
The present invention is based on a heat exchanger including a heat exchanger tube (20) through which a cold storage material (W) flows and supercools the cold storage material (W) by the low-temperature heat medium (M).

Furthermore, a flow path forming body (
21) is inserted into either the outer periphery of the flow path forming body (21) or the inner circumferential wall of the heat transfer tube (20) to control the flow of the regenerator material (W) in the heat transfer tube (20) in a spiral shape. It has a configuration in which a spiral protrusion (22) is formed to create a swirling flow.

0012

[Operation] According to the structure of the present invention, the cold storage material (W) is forcedly circulated from the ice storage tank (2) and flows into the heat exchanger tube (20) of the heat exchanger. A flow path forming body (21) is inserted into the heat exchanger tube (20). This channel forming body (
21) and the tube inner peripheral wall of the heat exchanger tube (20), a flow path for the cool storage material (W) flowing inside the heat exchanger tube (20) is formed in a cylindrical shape. The spiral protrusion (22) formed on either the outer periphery of the flow path forming body (21) or the inner circumferential wall of the heat transfer tube (20) transforms the flow of the cold storage material (W) into a spiral swirling flow. do. Therefore, the flow of the regenerator material (W) is pressed against the inner circumferential wall of the heat transfer tube (20) by the centrifugal force of the swirling flow within the cylindrical flow path, making it difficult for turbulence to occur.
The flow becomes stable.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the present invention is applied to a supercooling heat exchanger used in an ice heat storage device will be described below with reference to the drawings.

FIG. 1 shows the configuration of an ice heat storage device. The ice storage device (1) is equipped with an ice storage tank (2) for storing a cold storage material (W) frozen in the form of slurry, and includes an ice storage tank (2) and a heat exchanger (as a cooler). 3) is connected by a circulation path (4) so that the cold storage material (W) can be circulated. The circulation path (4) includes an outflow path (4A) that supplies cold storage material (W) from the bottom of the ice storage tank (2) to the heat exchanger (3), and a
) and a return flow path (4B) that returns the cold storage material (W) in the form of slurry ice to the upper part of the ice storage tank (2), and a pump interposed in the outflow flow path (4A). By (5), the cold storage material (W) of the ice storage tank (2) is forcedly circulated within the circulation path (4).

Furthermore, the return flow path (4B) of the circulation path (4) is
), on the downstream side of the heat exchanger (3), there is a heat exchanger (
A supercooling eliminating section (6) is provided to eliminate the supercooling state of the cool storage material (W) supercooled in step 3).

Methods for eliminating the supercooled state in the supercooling elimination section (6) include methods that apply thermal shock by cooling, mechanical methods that generate large flow velocity and turbulence, or generate vibrations and bubbles. There are various types, including those that give a strong impact.

[0017] Furthermore, as shown in Fig. 1, the ice storage tank (2) is provided with a cooling load (7) for using the cold energy of frozen substances mixed in the cold storage material (W) for air conditioning. . The cooling load (7) may be a method in which the stored cold storage material (W) is used to cool the refrigerant in the refrigerant circuit, or a method in which the air is directly cooled.

The cooling method for the heat exchanger (3) is a direct expansion type that uses a refrigerant as a low-temperature heat medium to directly cool the cold storage material (W), or a direct expansion type that uses cooled brine as a low-temperature heat medium to cool the cold storage material (W). Any indirect expansion type that cools (W) indirectly may be used. Water or an aqueous solution is used for the cold storage material (W).

Next, a specific example of the structure of a multi-tubular heat exchanger is shown in FIG. The multi-tubular heat exchanger (3) shown in FIG. (1
1) and end chambers (12) located above and below the shell (11).
), (12) are formed into sections. Shell (11)
A bundle of a large number of heat exchanger tubes (20) is housed inside. Both ends of the heat exchanger tube (20) are fixed to the tube plate (10) and communicate with the upper and lower end chambers (12), (12). The shell (11) has a fluid inlet (13) and an outlet (14). On the other hand, the lower end chamber (12
) is provided with an inflow nozzle (15), and the upper end chamber (12
) is provided with an outflow nozzle (16). Then, a low-temperature heat medium (M), which is a low-temperature fluid, is passed through the shell (11), and a cold storage material (M), which is a high-temperature fluid, is passed through the heat transfer tube (20).
W) is being distributed. Both fluids are piped so that they flow in parallel from the bottom to the top. That is, the low temperature heat medium (M) flows into the shell (11) through the inlet (13) and flows out through the outlet (14). In addition, cold storage material (
W) flows into the lower end chamber (12) from the inflow nozzle (15), flows through the heat transfer tube (20) from the lower end chamber (12), and then enters the upper end chamber (12); Upper end chamber (1
2) flows out from the outflow nozzle (16).

Next, as a feature of the present invention, as shown in FIG. 3, a flow path forming body (21) is inserted into the heat exchanger tube (20). The flow path forming body (21) is formed into a cylindrical hollow body that can be deformed inwardly, and a spiral protrusion (22) is formed on the outer periphery. The reason why the shape of the flow path forming body (21) is made into a hollow body that can be deformed inward is that even if the supercooling state is resolved and ice is generated, the ice will not connect to the heat exchanger tube (20) and the flow path forming body (21). This is to prevent the heat transfer tubes (20) from being damaged by the ice by allowing the flow path forming body (21) to expand and deform inward due to the expansion pressure of the ice even when the flow path between the heat exchanger tubes (20) is blocked. .

The spiral protrusion (22) may be of any type as long as it can form a spiral swirling flow in the flow of the cold storage material (W). In particular, the spiral protrusion (22) in FIG. 3 is formed into a helical twisting blade with a curved surface similar to the screw blade of a screw conveyor. When the twisted blades are used, the flow of the cool storage material (W) can be reversed without causing any disturbance. In other words, the high temperature part that was on the spiral protrusion (22) side can be periodically transferred to the heat exchanger tube (20) side. It can be reversed, and the cool storage material (W) can be cooled uniformly and efficiently. In addition, if a plurality of spiral protrusions (22) are formed, the cool storage material (W) can be cooled by dividing into several swirling flows, and the cooling effect is improved.

[0022] The channel forming body (21) and the spiral protrusion (22)
) is preferably a material that is less likely to corrode due to the cold storage material (W). Specifically, a synthetic resin or a corrosion-resistant metal such as stainless steel is used.

Next, the operation of the ice heat storage device (1) will be explained. To perform cold storage heat operation and store cold heat in the ice storage tank (2), the cold storage material (W) is circulated between the ice storage tank (2) and the heat exchanger (3), and the heat exchanger ( 3) supercools the cold storage material (W) in the ice storage tank (2). The supercooled cold storage material (W) is recooled in the supercooling elimination section (6), the supercooled state is eliminated, and a slurry-like frozen product is generated. The cold storage material (W) containing this frozen product is forcedly circulated and stored in the ice storage tank (2) while maintaining a flowable slurry state, and is used as cold energy during daytime cooling operation.

In the heat exchanger (3), the low temperature heat medium (M) flows into the shell (11) from the inlet (13), flows upward in the shell (11), and flows through the outlet (14). ) is ejected from the aircraft. The cold storage material (W) flows into the lower end chamber (12) from the outgoing flow path (4A), and flows into the lower end chamber (12).
), the cold storage material (W) is distributed and supplied to each heat exchanger tube (20). The cold storage material (W) that has flowed into the heat transfer tube (20) rises, and during the rise, the low temperature heat medium (M) passes through the heat transfer tube (20).
), the upper end chamber (1
2) is reached. Then, the supercooled cold storage material (W) is
From the outflow nozzle (16) of the upper end chamber (12) to the return flow path (
4B).

Furthermore, heat exchanger tubes (20) of the heat exchanger (3)
The internal structure and flow of the cold storage material (W) will be explained in detail.

The most important factor in eliminating the supercooled state of the regenerator material (W) in the heat transfer tube (20) is the occurrence of severe turbulence. In order to improve the heat transfer efficiency of a heat exchanger, it is necessary to generate some degree of turbulence in order to perform efficient heat transfer through heat exchange between the fluid near the tube wall and the mainstream fluid. However, when the turbulence becomes severe in the supercooling heat exchanger, the supercooled regenerator material (W
), the problem arises in that the supercooled state of the water is eliminated, which leads to ice formation and subsequent blockage of the flow path.

Therefore, in the present invention, the heat exchanger tube (20) is inserted by inserting the flow path forming body (21) into the heat exchanger tube (20).
), and the flow of the cold storage material (W) in this limited flow path is made into a spiral swirling flow by the spiral protrusions (22). That is, the outer periphery of the flow path forming body (21) inserted into the heat exchanger tube (20) and the tube inner peripheral wall of the heat exchanger tube (20) form the flow path of the regenerator material (W) flowing inside the heat exchanger tube (20). Form into a cylinder. Furthermore, a spiral protrusion (22) formed on the outer periphery of the flow path forming body (21)
makes the flow of the cold storage material (W) into a spiral swirling flow.

[0028] The cylindrical flow path formed by the heat transfer tube (20) is annular when viewed in a certain cross section, and the heat transfer tube (20)
The cold storage material (W) does not flow through the center of the area. On the other hand, when the flow path forming body (21) is not inserted into the heat exchanger tube (20), the cold storage material (W) can move from a certain point on the tube wall to the opposing tube wall through the center of the tube, and the cold storage material (W) can move from a certain point on the tube wall to the opposing tube wall. There is a risk that severe turbulence will occur in the flow of (W). In contrast, in the present invention, since the flow path of the cold storage material (W) is formed with an annular cross section, the area in which the cold storage material (W) can move in the radial direction is small, and the degree of turbulence can be reduced. Can be done. parable,
Even if the flow velocity of the cool storage material (W) increases to some extent due to the swirling flow, an increase in turbulence can be suppressed. Moreover, the centrifugal force of the swirling flow presses the regenerator material (W) against the inner circumferential wall of the heat transfer tube (20), suppressing turbulence and suppressing the regenerator material (W).
) flow can be stabilized. As a result, it becomes difficult to eliminate the supercooled state within the heat exchanger tube (20),
Blockage of the flow path can be prevented.

Conventionally, fluctuations in the flow velocity of the cool storage material (W) cannot be avoided to some extent, and in order to avoid the situation where the supercooling state is eliminated due to fluctuations in the flow velocity, the degree of supercooling is set to a small value. The safety factor was large. However, it becomes difficult to eliminate the supercooled state within the heat exchanger tube (20), and the degree of supercooling can be set large. In addition, the amount of ice made per cycle can be increased, and the ice making capacity can be improved.

[0030] Furthermore, making the flow of the cold storage material (W) a swirling flow also lengthens the residence time of the cold storage material (W) and increases the amount of heat transfer, so from this point of view as well. Ice making capacity can be improved.

The structure of the heat exchanger (3) is a double-tube type in order to ensure the flow velocity when the flow rate of the low-temperature heat medium and the cold storage material (W) is low.
type) heat exchanger may be used. In addition, if the film heat transfer coefficient on the outside of the heat tube (low-temperature heat medium side) is much smaller than that on the inside of the tube (cool storage material side), use a low-fin tube as the heat transfer tube, and use the heat transfer area on the outside of the tube. The amount of heat transfer per unit pipe length may be increased by widening the pipe length. Furthermore, the number of reciprocations of the fluid inside the tubes in the multi-tubular heat exchanger may be either one-pass or multi-pass.

Next, the supercooling of the present invention will be explained based on experimental examples.

FIGS. 4(a) and 4(b) show Example 1 of the present invention in which a double-tube type heat exchanger is used as the heat exchanger. The heat transfer tube (20), which is the inner tube of the double tube, has an inner diameter of 14.0 mm.
A straight pipe was used. The flow path forming body (21) has an outer diameter of 10.
A spiral protrusion (22) was formed by winding a synthetic resin-coated wire around a 0 mm bar. Two types of channel forming bodies (21) were prepared in which the wire diameter δ and the winding pitch p were changed. A double-tube heat exchanger was manufactured by inserting the flow path forming body (21) into the heat transfer tube (20). A cool storage material (W) was passed through the heat transfer tube (20) at a flow rate of 3 to 4 l/min, and the critical degree of supercooling ΔTsc at which the supercooling state started to be eliminated was measured.

To measure the degree of supercooling ΔTsc, a thermocouple was attached near the end of the heat exchanger tube, and the temperature of the heat exchanger tube or the temperature of the regenerator material (W) was measured. Then, based on the measured temperature records, the temperature curve rapidly rises to 0℃ when the supercooling state is eliminated, so by finding the inflection point, the temperature T at the time of elimination can be found, and the degree of supercooling △T
sc was determined.

In Example 1 of the present invention, the wire diameter δ of the spiral protrusion (22)
was set to 1.2 mm, and pitch p was set to 8.0 mm. Figure 5 (a
In Example 2 of the present invention shown in ) and (b), the wire diameter δ of the spiral protrusion (22) was 2.0 mm, and the pitch p was 48.0 mm.

Comparative Example 1 is a case in which the channel forming body (21) and the spiral protrusion (22) shown in FIGS. 6(a) and 6(b) are not inserted, and the case shown in FIGS. 7(a) and (b) is The flow path forming body shown (
Comparative Example 2 was a case in which the spiral protrusion (22) was not formed in 21), and the degree of supercooling ΔTsc was measured in the same manner. The results are shown in Table 1.

[0037]

[Table 1]

As shown in Table 1, compared to Comparative Example 3 in which the channel forming body (21) was not inserted and Comparative Example 4 in which the spiral protrusion (22) was not formed in the channel forming body (21). It was confirmed that the critical degree of supercooling ΔTsc at which the supercooling state starts to disappear can be increased. In addition, Example 2 of the present invention in which the spiral protrusion (22) is closely attached to the heat exchanger tube (20),
The critical degree of supercooling ΔTsc is larger than that of Example 1 of the present invention in which there is a gap between the spiral protrusion (22) and the heat exchanger tube (20). This is considered to be because the regenerator material does not flow between adjacent flow paths, so that a swirling flow is formed in a better shape.

By the way, as mentioned above, in the supercooling control type ice heat storage device, it is important not to eliminate the supercooling state in the heat exchanger for supercooling. To do this, it is necessary to control the supercooling temperature, but to do so, it is first necessary to accurately know the degree of supercooling, or in other words, the temperature of the supercooled regenerator material.

[0040] There are contact and non-contact methods for measuring the temperature of the regenerator material, but it is preferable to use a non-contact measuring device that does not eliminate the supercooled state due to the resistance of the measuring device. Non-contact measuring devices include optical measuring devices that use changes in refractive index due to temperature, as well as measuring devices that mix temperature-sensitive liquid crystals into cold storage material and use the fact that the color of water changes with temperature changes. is used.

Furthermore, even a contact-type measuring device can be used to measure the temperature of a cold storage material by providing a means for peeling off icing caused by the measuring device. For example, a heat insulating section is provided near the end of a heat transfer tube of a heat exchanger, and a contact measuring device such as a thermocouple is attached to this heat insulating section to measure the temperature of the heat transfer tube or the temperature of the cool storage material (W). When the supercooling state is resolved by the measurement device, the measured temperature rapidly rises to 0°C, making it possible to detect the formation of ice. Immediately after the measured temperature suddenly changes, defrost operation is performed. Therefore, the ice peeling means may be provided with a sensor that detects sudden temperature changes and a defrost control means that performs defrost operation based on an ice generation signal from the sensor. In this way, even if the measuring device induces the elimination of the supercooled state and ice builds up on the pipe wall,
It is possible to prevent clogging and further damage of the heat exchanger tubes. Note that during the defrost operation, it is desirable to stop the flow of the cold storage material (W) so as not to reduce the defrost performance.

[0042] Furthermore, as a special measurement method, there is a method in which a flow path forming member within a heat transfer tube is provided with a temperature measurement function. Specifically, the temperature at the end of the heat exchanger tube, where temperature conditions are the most important, is measured using an optical fiber. That is, an optical fiber is built into the body of the flow path forming body so that the cool storage material inside the heat transfer tube can be irradiated. On the other hand, a transparent window is attached to the end of the heat exchanger tube and the shell near the end, and the temperature is measured by detecting the light transmitted through the regenerator material or the light reflected from the inner wall of the tube from the outside.

[0043]

As described above, according to the present invention, a cylindrical flow path is formed in a heat transfer tube by inserting a flow path forming body into the heat transfer tube, and the cylindrical flow path in this limited flow path is The flow of the cold storage material is made into a spiral swirling flow by the spiral protrusions.

[0044] Therefore, the area in which the flow path forming body can move in the radial direction is narrowed, and the spiral swirl flow created by the spiral protrusions presses the regenerator material (W) against the inner circumferential wall of the heat transfer tube (10). , the degree of turbulence is kept small, and the cold storage material (
The flow of W) can be stabilized. As a result, it is possible to make it difficult to eliminate the supercooled state within the heat transfer tube (20), prevent blockage of the flow path, and increase the degree of supercooling, thereby improving ice making capacity.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of an ice heat storage device.

FIG. 2 is a sectional view showing the overall structure of the heat exchanger.

FIG. 3 is a sectional view showing the structure of a heat exchanger tube of a heat exchanger.

4 shows Example 1 of the present invention, FIG. 4(a) is a longitudinal cross-sectional view, and FIG. 4(b) is a cross-sectional view.

FIG. 5 shows Example 2 of the present invention, in which FIG. 5(a) is a longitudinal cross-sectional view and FIG. 5(b) is a cross-sectional view.

6 shows Comparative Example 1, FIG. 6(a) is a longitudinal cross-sectional view, and FIG. 6(b) is a cross-sectional view.

7 shows Comparative Example 2, FIG. 7(a) is a longitudinal cross-sectional view, and FIG. 7(b) is a cross-sectional view.

[Explanation of symbols]

3 Heat exchanger 11 Shell (outer channel) 20 Heat exchanger tube 21 Channel forming body 22 Spiral protrusion M Low temperature heat medium W Cold storage material

Claims (1)

[Claims] 1. An outer flow path (11) through which a low-temperature heat medium (M) flows; ), the cold storage material (
In a heat exchanger equipped with a heat transfer tube (20) for supercooling W), a flow path forming body (21) is inserted into the heat transfer tube (20), and the outer periphery of the flow path forming body (21) or Heat exchanger tube (
A heat transfer tube (20) is attached to either one of the inner peripheral walls of the tube (20).
A heat exchanger characterized in that a spiral protrusion (22) is formed to make the flow of a cold storage material (W) in a spiral spiral flow.