WO2021176979A1

WO2021176979A1 - Heat exchanger

Info

Publication number: WO2021176979A1
Application number: PCT/JP2021/004924
Authority: WO
Inventors: 俊彦幸; 皓也新井
Original assignee: 三菱マテリアル株式会社
Priority date: 2020-03-05
Filing date: 2021-02-10
Publication date: 2021-09-10
Also published as: CN115210520A; JP7459570B2; US20230126444A1; EP4116636A1; JP2021139559A; EP4116636A4

Abstract

This heat exchanger includes: an external tube through which a heat medium flows; a heat source which heats or cools a middle position of the external tube from outside; and a heat exchange unit which can perform heat exchange between the heat medium flowing inside the external tube and the heat source. The heat exchange unit comprises: a cylindrical porous body that is in close contact with the inner surface of the external tube; at least one circuit of an inner side flowpath formed on the inner side of the porous body; and at least one valve which opens/closes the inner flowpath. The porous body includes continuous pores formed therein, the pores communicating with both ends of the porous body in the heat medium flow direction and allowing the heat medium to flow therethrough.

Description

Heat exchanger

The present invention relates to a heat exchanger and relates to a heat exchanger whose heat exchange performance can be changed by switching the flow path. The present application claims priority based on Japanese Patent Application No. 2020-038132 filed on March 5, 2020, the contents of which are incorporated herein by reference.

Patent Document 1 describes one or more first heat exchange means buried in soil, one or more second heat exchange means laid in a building, and a first heat exchange means. A pipe system that connects the second heat exchange means, a liquid medium for heat exchange that circulates in the pipe system, a pump means for circulating the liquid medium for heat exchange in the pipe system, and circulation in the pipe system. Valve switching means for switching the circulation path of the liquid medium for heat exchange, temperature detection system for detecting the temperature of each place, and pump means and valve switching based on the temperature data from each temperature sensor constituting the temperature detection system. A control means for controlling the means and an air conditioning system using soil heat provided with the means are disclosed.

Japanese Unexamined Patent Publication No. 2003-21360

In the air conditioning system described in Patent Document 1, it is necessary to switch the circulation path according to the indoor temperature and the like, but if the valve is suddenly opened and closed to prevent the fluid from flowing to a specific heat exchange portion, the circulation path is circulated. A water hammer phenomenon occurs in the pipe of the path, which may lead to damage to the device.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a heat exchanger capable of efficiently exchanging heat and suppressing the occurrence of a water hammer phenomenon when switching a flow path. ..

The heat exchanger of the present invention heats between an outer tube through which a heat medium flows, a heat source that heats or cools an intermediate position of the outer tube from the outside, and the heat medium and the heat source that flow through the outer tube. It has a heat exchange unit that can be exchanged. The heat exchange unit includes a tubular porous body in close contact with the inner peripheral surface of the outer tube, an inner flow path formed inside the porous body, and a valve for opening and closing the inner flow path. The porous body is formed with continuous pores that communicate with both ends of the heat medium in the flow direction and allow the heat medium to flow.

In this heat exchanger, the porous body has continuous pores through which the heat medium can flow. Therefore, when the inner flow path is closed by a valve, the heat medium flows through the continuous pores of the porous body. .. Since a heat source is provided on the outside of the outer tube, heat is exchanged between the heat medium flowing through the porous body and the heat source, and the heat source heats or cools the heat. The heat medium that has exchanged heat with this heat source flows downstream of the porous body and exchanges heat with the outside environment of the outer tube at the downstream position to dissipate heat or absorb heat.

On the other hand, when the valve of the inner flow path of the porous body is opened, the flow path resistance of this inner flow path is smaller than that of the porous body, so that most of the heat medium flowing from the upstream of the porous body is mostly. It flows into the inner flow path and is guided downstream. At this time, the flow of the heat medium hardly occurs in the porous body, and the heat medium stays in the pores, or even if it flows, the flow rate remains small.

Therefore, the heat from the heat source on the outside of the outer tube heats or cools the porous body and the heat medium inside the porous body while being transferred to the inner flow path via the heat medium inside the porous body. Since energy is consumed and the heat medium is substantially retained in the porous body, heat transfer is blocked and the amount of heat transferred from the inner surface of the inner flow path to the heat medium is reduced.

Also, since the flow is small even if it occurs in the porous body, the heat transfer from the porous body to the downstream is also small. Further, the inner flow path has a small pressure loss with respect to the heat medium flowing inside the inner flow path, so that the inner flow path flows at a relatively large flow rate. Since the amount of heat transferred from the inner surface of the inner flow path is smaller than the flow rate, the amount of heat carried by the heat medium in the inner flow path is also smaller. Therefore, when the valve of the inner flow path is open, heat exchange between the heat source and the heat medium is suppressed.

By opening and closing the valve in the inner flow path in this way, the magnitude of heat exchange between the heat source and the heat medium can be switched. At this time, since the heat medium flows not only in the inner flow path but also in the porous body from the upstream to the downstream of the heat exchange portion, a sudden change in the pressure inside the outer tube is unlikely to occur, and the occurrence of the water hammer phenomenon is suppressed.

In this heat exchanger, the porosity of the porous body is preferably 60% or more and 90% or less. If the porosity is less than 60%, the flow path resistance of the porous body is large, so that the amount of heat medium flowing through the porous body is small when the valve is closed, and the load of the pump that sends the heat medium is large. If the porosity exceeds 90%, the heat medium flowing through the porous body quickly flows downstream, and there is a risk that heat exchange with the heat source will not be sufficient.

In this heat exchanger, the pressure loss between the upstream position and the downstream position of the porous body when the heat medium is circulated in the outer tube seals the upstream surface of the porous body. Assuming that the pressure loss when only the inner flow path of the inner pipe is opened is ΔP1 and the pressure loss when the valve is closed and only the inside of the porous body is circulated is ΔP2, the pressure loss ratio (ΔP2 / ΔP1) is 1. It is preferable that it is 3 or more and 3 or less.

If these pressure loss ratios (ΔP2 / ΔP1) exceed 3 times, the pressure fluctuation when the valve is closed becomes too large, and the water hammer phenomenon may occur. If it is less than 1 times, when the valve is opened, a large amount of heat medium flows not only into the inner flow path but also into the porous body, so that the heat insulating effect in the porous body is reduced and the effect of switching heat exchange is small. ..

According to the present invention, it is possible to efficiently exchange heat and suppress the occurrence of the water hammer phenomenon when switching the flow path.

It is a schematic diagram of the heating system using the heat exchanger of one Embodiment of this invention. FIG. 5 is an enlarged cross-sectional view showing a state in which a valve is closed in the heat exchanger shown in FIG. It is sectional drawing which shows the state which opened the valve in the heat exchanger of FIG. It is sectional drawing which shows the heat exchanger of another embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The heat exchanger 1 of the present embodiment is used in a heating system 10 in which a heat medium (air) is heated by a heat source 2 and the heat of the heat medium that has become hot is dissipated in a target room or the like. FIG. 1 schematically shows the heating system 10, and reference numeral 20 corresponds to a heat absorbing unit (first heat exchange unit, heat exchange unit of the present invention) in which a heat medium is heated by the heat of the heat source 2. ), Reference numeral 40 indicates a heat dissipation unit (second heat exchange unit) that dissipates the heat of the heat medium that has become hot in the first heat exchange unit 20.

The heat exchanger 1 heats between the outer tube 3 through which the heat medium flows, the heat source 2 that heats the intermediate position of the outer tube 3 from the outside, and the heat medium and the heat source 2 that flow through the outer tube 3. It has a first heat exchange unit 20 for replacement.

The first heat exchange unit 20 includes a tubular porous body 21 in close contact with the inner peripheral surface of the outer tube 3, an inner tube 22 in close contact with the inner peripheral surface of the porous body 21, and the inner tube 22. It is provided with a valve 24 that opens and closes the flow path (inner flow path) 23.

The porous body 21 is formed by sintering a metal having excellent thermal conductivity, for example, powder or fiber made of aluminum, copper or the like, or a mixture thereof, has a metal skeleton, and has a porosity of 60%. It is set within the range of 90% or more and 90% or less. The pores in the porous body 21 include continuous pores communicating from one end to the other end of the porous body 21, and when a heat medium is supplied to one end of the porous body 21, the pores pass through the continuous pores. It can flow out from the other end of the body 21.

The specific surface area (per unit volume) of the porous body 21 ^{is preferably 1000 m 2} / m ³ or more and 15000 m ² / m ³ or less. If the porosity of the porous body 21 is less than 60%, the flow path resistance of the porous body 21 becomes large (for example, 3 kPa), so that the amount of heat medium flowing through the porous body when the valve is closed is small, and the heat medium is used. The load on the sending pump increases. If the porosity exceeds 90%, the heat medium flowing through the porous body 21 will quickly flow downstream, and there is a risk that heat exchange with the heat source 2 will not be sufficient.

As such a porous body 21, for example, one obtained by sintering an aggregate of a large number of metal powders, one obtained by sintering an aggregate of a large number of metal fibers, and a mixture of these metal fibers and the metal powder are sintered. Can be adopted. Further, by adding a foaming agent and sintering, a foamed metal having a three-dimensional network structure in which a plurality of pores formed by a continuous metal skeleton communicate with each other may be obtained.

The porous body 21 is provided in close contact with the inner peripheral surface of the outer tube 3. In the figure, a relatively short short pipe 35 is formed in the middle of the outer pipe 3 so that it can be connected by flanges 31 to 34, and a porous body 21 is provided in the short pipe 35. In this case, the metal powder or metal fiber is solidified into a tubular shape in the short tube 35 to form an aggregate, and the metal powder or metal fiber is bonded to the inner peripheral surface of the short tube 35 by sintering in the short tube 35. NS.

The inner pipe 22 is provided coaxially with the short pipe 35 in a state of being in close contact with the inner peripheral surface of the porous body 21. Also in this case, the metal powder or metal fiber is solidified into a tubular shape on the outer peripheral surface of the inner tube 22 to form an aggregate, and the metal powder is sintered on the outer peripheral surface of the inner tube 22 to form a metal powder on the outer peripheral surface of the inner tube 22. And metal fibers are bonded.

Specifically, the short pipe 35 and the inner pipe 22 are arranged coaxially, and metal powder or metal fiber is solidified and filled in a tubular shape between them, and the short pipe 35, the inner pipe 22, the metal powder or the like is put into a furnace. By putting and heating, the inner peripheral surface of the porous body 21 and the outer peripheral surface of the inner tube 22 are bonded, and the outer peripheral surface of the porous body 21 and the inner peripheral surface of the short tube 35 are formed in a bonded state. NS.

The outer tube 3 and the inner tube 22 may be formed of the same type of metal as the porous body 21, or may be formed of a different type of metal as long as they can be joined, such as by combining aluminum and copper. You may.

The inner pipe 22 is larger than the length of the porous body 21 and protrudes in the downstream direction from one end (downstream side end) of the porous body 21. A valve 24 for opening and closing the inner flow path 23 is provided at the end of the protruding inner pipe 22.

As the valve 24, a butterfly valve that opens and closes the flow path by rotating the valve body 24a by 90 ° is illustrated in the figure, but it can be applied as long as it can open and close the flow path such as a ball valve and a sluice valve. ..

At the other end (upstream end) of the porous body 21, the tip of the inner tube 22 is arranged in the same manner as the end face of the porous body 21.

The pressure loss ratio between the inner flow path 23 and the porous body 21 is such that the heat medium flows only through the inner flow path 23 by sealing the upstream surface of the porous body 21 and opening only the inner flow path 23. When the pressure loss is ΔP1 and the pressure loss when the heat medium flows only in the porous body 21 (equal to the pressure loss when the valve 24 is closed) is ΔP2, the pressure loss ratio (ΔP2 / ΔP1) Is 1 or more and 3 or less.

When the pressure loss ratio (ΔP2 / ΔP1) between the inner flow path 23 and the porous body 21 is less than 1, when the valve 24 is opened, not only the inner flow path 23 but also the inside of the porous body 21 has many. Since the heat medium flows in, the heat insulating effect of the porous body 21 is reduced, and the effect of switching the heat exchange is small. If the pressure loss ratio (ΔP2 / ΔP1) exceeds 3, the pressure fluctuation when the valve 24 is closed is large, and a water hammer phenomenon may occur. The pressure loss ratio (ΔP2 / ΔP1) between the inner flow path 23 and the porous body 21 is more preferably 1.5 or more and 2 or less.

Further, assuming that the pressure loss of the entire flow path when the valve 24 is open (fully open state) is ΔP3 and the pressure loss of the entire flow path when the valve 24 is closed (fully closed state) is ΔP2, the pressure The loss ratio (ΔP2 / ΔP3) is preferably 1.2 or more and 15 or less.

If the pressure loss ratio (ΔP2 / ΔP3) when the valve 24 is opened and closed exceeds 15, the pressure fluctuation of the entire heat exchanger 1 system becomes too large, and the design becomes complicated. If it is less than 1.2, when the valve 24 is opened, a large amount of heat medium flows not only into the inner flow path 23 but also into the porous body 21 (in other words, the amount of heat medium flowing through the inner flow path 23 is small). The heat insulating effect of the porous body 21 is reduced, and the effect of switching the heat exchange is reduced. The pressure loss ratio (ΔP2 / ΔP3) due to opening and closing of the valve 24 is more preferably 3 or more and 10 or less.

Further, although not necessarily limited, when the cross-sectional area of the inner flow path 23 is A1 mm ² and the cross-sectional area of the porous body 21 is A2 mm ² , these cross-sectional area ratios (A2 / A1) are 3. It is preferable that it is 12 or less. If this cross-sectional area ratio (A2 / A1) is less than 3, the water hammer phenomenon is likely to occur because the flow rate difference between when the valve 24 is closed and when it is opened is large, and when it exceeds 12, the total flow rate is small and the heat exchange efficiency is high. Reduce.

In the first heat exchange section 20, it is preferable that the heat source 2 and the outer tube 3 are covered with a heat insulating material.

The second heat exchange unit 40 is installed in a room that requires heating in this embodiment, and a plurality of fins 41 are integrally formed on the outer peripheral surface of the outer pipe 3 to promote heat dissipation.

In the heating system 10 configured in this way, the heat source 2 arranged outside the first heat exchange unit 20 is heated, the valve 24 is closed, and the heat medium (air) is circulated from the upstream of the first heat exchange unit 20. Then, in the first heat exchange unit 20, the heat medium does not flow into the inner tube 22 but flows through the porous body 21.

Since the porous body 21 has continuous pores as described above, the heat medium flows through the porous body 21 and flows out from the other end of the porous body 21 toward the downstream side. The outer peripheral surface of the porous body 21 is in close contact with the inner peripheral surface of the outer tube 3, and the heat source 2 is provided on the outer side of the outer tube 3 in a heat-generating state. Therefore, the heat of the heat source 2 is rapidly transferred to the porous body 21 through the wall of the outer tube 3, and is porous until it is transferred to the inner tube 22 via the metal skeleton in the porous body 21. It is transmitted to the heat medium circulating in the pores of the body 21 to heat the heat medium.

Since the specific surface area of the porous body 21 is large, heat is efficiently transferred from the metal skeleton of the porous body 21 to the heat medium. The heat medium that has become hot in the porous body 21 and has flowed downstream of the porous body 21 is transferred to the fins 41 by the second heat exchange section 40 to dissipate heat from the fins 41, and is dissipated from the fins 41. 40 Warm the surrounding environment.

On the other hand, when the valve 24 is opened (FIG. 3), the heat medium supplied from the upstream of the first heat exchange section 20 has a larger pressure loss in the porous body 21 than in the inner tube 22, so that the inside tube 22 has a larger pressure loss. Preferentially flow into. Therefore, most of the heat medium flows through the inner flow path 23 and flows downstream, and the heat medium flows little or hardly flows in the porous body 21 and stays in the pores.

Therefore, the porous body 21 functions as a heat insulating body, and heat transfer from the heat source 2 into the inner pipe 22 is suppressed. Therefore, the heat medium flowing through the inner flow path 23 is guided downstream without changing the temperature.

In this way, when the valve 24 is closed (FIG. 2), the heat of the heat source 2 is transferred to the heat medium flowing through the porous body 21, and the heated heat medium flows downstream, while the valve 24 is opened. In this state, heat is not transferred to the heat medium flowing through the inner flow path 23, and flows downstream while maintaining the temperature upstream of the first heat exchange unit 20. Therefore, by opening and closing the valve 24, the heat of the heat source 2 can be transferred to or cut off from the heat medium.

Further, by adjusting the opening degree of the valve 24, the heat medium is circulated to both the porous body 21 and the inner pipe 22, and the temperature of the heat medium passing through the first heat exchange unit 20 is appropriately controlled. Is also possible. That is, although there is a large difference between the pressure loss of the porous body 21 and the pressure loss of the inner pipe 22, a part of the heat medium is made of the porous body by appropriately adjusting the opening degree of the valve 24. It can be distributed to 21 and the rest can be distributed in the inner pipe 22.

In the porous body 21, the heat medium that has become hot due to the heat of the heat source 2 flows downstream, and in the inner tube 22, the heat medium flows downstream while the temperature of the upstream is almost maintained. Then, both of them merge at a downstream position of the first heat exchange section 20 and flow as a mixed fluid thereof. The temperature of this mixed fluid is set by a combination of the temperature and flow rate of the heat medium passing through the porous body 21 and the temperature and flow rate of the heat medium passing through the inner flow path 23.

Then, by adjusting the opening degree of the valve 24, the pressure loss difference between the porous body 21 and the inner pipe 22 is controlled, the flow rate ratio between the porous body 21 and the inner pipe 22 is adjusted, and the porous body is adjusted. The temperature of the heat medium downstream of 21 can be arbitrarily set.

By adjusting the opening degree of the valve 24 in this way, the temperature around the second heat exchange unit 40 can be appropriately controlled. In this case, the temperature can be adjusted only by opening and closing the valve 24 (adjusting the opening degree), and since the pressure of the heat medium is not abruptly changed, the occurrence of the water hammer phenomenon can be prevented.

The present invention is not limited to the configuration of the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the examples shown in FIGS. 1 to 3, one inner pipe 22 is provided, but as in the heat exchanger 11 shown in FIG. 4, a plurality of inner pipes 22 each having a valve 24 are provided and a plurality of systems are provided. The inner flow path 23 of the above may be formed.

In this case, the pressure loss ΔP1 of the inner flow path 23 is the pressure loss when all the inner flow paths 23 of the plurality of inner pipes 22 are circulated, and the pressure loss ratio (ΔP2 / ΔP3) when the valve 24 is opened and closed. Is the pressure loss ratio when all the inner flow paths 23 are opened and closed. The cross-sectional area A1 mm ² of the inner flow path 23 is the total cross-sectional area of all the inner flow paths 23.

In the heat exchanger 11 shown in FIG. 4, since valves 24 are provided in each of the plurality of inner pipes 22, the opening degrees of the valves 24 are not the same, but are fully opened, fully closed, and intermediately opened. It is possible to set the optimum temperature while adjusting the opening and closing of each valve 24 such as degree.

Further, when the porous body 21 was formed by sintering, it was bonded to the inner peripheral surface of the outer tube 3 and the outer peripheral surface of the inner tube 22, but the outer tube 3 and the inner tube 22 were in close contact with each other. If it is filled, it does not necessarily have to be bonded.

No. As 1 to 9, aluminum powder and fibers are formed between an outer tube having an inner diameter of 15 mm to 30 mm and a thickness of 1 mm made of aluminum or an aluminum alloy and an inner tube having an inner diameter of 8 mm and an outer diameter of 10 mm also made of aluminum or an aluminum alloy. A porous body was formed by filling and sintering the mixture of. The length of the inner tube was 150 mm, and the porous body had the length (50 mm, 100 mm, 150 mm, 300 mm) and the porosity (60% to 95%) shown in Table 1.

Air was used as the heat medium, and the pressure difference between the upstream and downstream of the porous body was measured when the valve was open and when the valve was closed.

A heat source (heater) was brought into close contact with the outer peripheral surface of the outer tube at an intermediate position of the length of the porous body within a range of 30 mm in length, and air at room temperature (25 ° C.) was circulated as a heat medium. The heat source and the outer tube were covered with heat insulating material.

Then, the pressure at the upstream position and the pressure at the downstream position of the porous body when the porous body was sealed and circulated only in the inner flow path were measured, and the differential pressure ΔP1 (pressure loss) was obtained. ..

The pressure at the upstream position and the pressure at the downstream position of the porous body when only the porous body is circulated with the valve closed are measured to obtain the differential pressure ΔP2 (pressure loss), and these differential pressures are obtained. The ratio of P1 and P2 (pressure loss ratio) (ΔP2 / ΔP1) was calculated.

The pressure at the upstream position and the pressure at the downstream position of the porous body were measured with the valve open without sealing the porous body, and the differential pressure ΔP3 (pressure loss) was also obtained.

With the valve closed, measure the temperature between the heat source and the outer tube with a thermocouple, adjust the temperature of the heat medium so that the thermocouple records 60 ° C, and 5 minutes after opening the valve. The temperature of the above was measured with a thermocouple, and the thermal change ΔT (K) was determined.

For comparison, a product without a porous body between the outer pipe and the inner pipe (No. 10) was also prepared. These results are shown in Tables 1 and 2.

As is clear from the results shown in Tables 1 and 2, No. 1 in which a porous body is provided between the outer tube and the inner tube. It can be seen that in 1 to 9, a predetermined thermal change can be obtained by switching the flow path between the porous body and the inner flow path of the inner tube. No. As in 1 to 8, when the porosity of the porous body is 60% or more and 90% or less, and the pressure loss ratio (ΔP2 / ΔP1) between the porous body and the inner flow path is 1 time or more and 3 times or less. The thermal change ΔT is large and the heat is sufficiently exchanged.

On the other hand, No. which did not provide a porous body. In No. 10, the pressure loss ratio (ΔP2 / ΔP1) and the thermal change ΔT are small, and sufficient heat exchange is not obtained.

In addition to efficiently exchanging heat, it is possible to suppress the occurrence of the water hammer phenomenon when switching the flow path.

1,11 Heat exchanger 2 Heat source 3 Outer pipe 10 Heating system 20 First heat exchange part 21 Porous body 22 Inner pipe 23 Inner flow path 24 Valve 40 Second heat exchange part 41 Fin

Claims

The outer tube through which the heat medium flows and
A heat source that heats or cools the middle position of the outer pipe from the outside,
A heat exchanger having a heat exchange unit capable of exchanging heat between the heat medium flowing in the outer tube and the heat source.
The heat exchange section opens and closes a tubular porous body in close contact with the inner peripheral surface of the outer tube, at least one inner flow path formed inside the porous body, and the inner flow path. With at least one valve
A heat exchanger characterized in that the porous body communicates with both ends of the heat medium in the flow direction and has continuous pores through which the heat medium can flow.
The heat exchanger according to claim 1, wherein the porous body has a porosity of 60% or more and 90% or less.
The pressure loss between the upstream position and the downstream position of the porous body when the heat medium is circulated in the outer tube seals the upstream surface of the porous body and only the inner flow path. Assuming that the pressure loss when opened is ΔP1 and the pressure loss when the valve is closed and only the porous body is circulated is ΔP2, the pressure loss ratio (ΔP2 / ΔP1) is 1 or more and 3 or less. The heat exchanger according to claim 1.
The pressure loss between the upstream position and the downstream position of the porous body when the heat medium is circulated in the outer tube seals the upstream surface of the porous body and only the inner flow path. Assuming that the pressure loss when opened is ΔP1 and the pressure loss when the valve is closed and only the porous body is circulated is ΔP2, the pressure loss ratio (ΔP2 / ΔP1) is 1 or more and 3 or less. 2. The heat exchanger according to claim 2.
The heat exchanger according to claim 1, wherein the inner flow path is provided with a plurality of systems, each of which has the valve.
The heat exchanger according to claim 1, wherein each of the valves has an adjustable opening degree.