JP3906830B2 - Natural circulation cooling device and heat exchange method using natural circulation cooling device - Google Patents

Description

  The present invention relates to a heat transport device that uses a coolant whose use environment may be near a critical point, circulates the coolant naturally using a change in density of the coolant, and transports cold or warm heat.

  In recent years, fields for removing heat generated by electronic devices such as communication base stations containing relay electronic devices for mobile communication are rapidly expanding, and cooling operation throughout the year is required in these places. In such applications, if the outside air temperature is low, such as in winter or at night, it is possible to cool it by ventilation, but a device that prevents intrusion of fog, rain, snow, and dust is required, and the outside air temperature As the room temperature also fluctuates due to fluctuations, stable cooling cannot be performed. In such a case, it is possible to use a heat transport device that uses a natural circulation in which heat is transferred from the room to the room by a refrigerant using the temperature difference between the room temperature and the outside air temperature. Since this natural circulation type heat transport device does not use a compressor, the annual power consumption can be greatly reduced as compared with a normal vapor compression type cooling device.

In recent years, natural refrigerants tend to be used from the viewpoint of global environmental protection, and the use of carbon dioxide (CO ₂ ), which is particularly low in flammability, has been studied. This carbon dioxide is in a supercritical state different from both liquid and gas in an environment where the critical point is a pressure of 7.3 MPa and the temperature is 31 ° C. or higher.

  There is a conventional heat transport device using carbon dioxide in a supercritical state as a refrigerant. In general, in a heat pipe enclosing a hydraulic fluid such as water, a large amount of energy is required to counter the latent heat for phase change and the viscosity of the hydraulic fluid when circulating the hydraulic fluid. Carbon dioxide in a supercritical state has physical properties similar to those of liquids in density and thermal conductivity, but has a viscosity close to that of gas. For this reason, if carbon dioxide, which is in a supercritical state, is enclosed in the internal space of the heat pipe, it can be circulated in the heat pipe with less energy than a heat pipe enclosing a hydraulic fluid such as water (for example, patents) Reference 1).

In addition, there has been a heat transport device that uses carbon dioxide as a refrigerant and attempts to determine the amount of the enclosed gas in consideration of the performance during operation and the pressure resistance characteristics when stopped (for example, see Patent Document 2). Generally, in a heat pipe in which carbon dioxide is sealed, when the refrigerant temperature exceeds 31 ° C. due to the environmental temperature in a stopped state, the carbon dioxide in the heat pipe becomes a supercritical state, and the internal pressure increases as the enclosed amount increases. At this time, if the internal pressure becomes higher than the pressure resistance characteristic determined by, for example, the end sealing strength of the heat pipe, the heat pipe will burst or the like. For this reason, the amount of refrigerant enclosed is set so that the performance of the heat transfer medium is maximized and the internal pressure is equal to or lower than the pressure resistance of the heat pipe even when the refrigerant temperature exceeds 31 ° C. in a stopped state. Specifically, when copper pipes are connected in an annular shape, the thickness is 1.1 mm, the weight per unit length is 274 g / m, and the maximum temperature of the environment is 55 ° C. The enclosed amount of the heat transfer medium is set to 300 kg / m ³ or less so that the pressure is lower than 10 MPa.

JP 2001-91170 A (first to third pages, FIG. 1) JP 2001-91173 A (page 1 to page 3, FIGS. 1 and 2)

  The problem to be solved is that when the refrigerant temperature exceeds the critical temperature depending on the use environment temperature, the refrigerant enters a supercritical state, the latent heat due to phase change disappears, and the heat transfer coefficient is higher than when the refrigerant temperature is lower than the critical temperature. It is to decline. On the other hand, in the conventional heat transport device, a specific configuration for improving the heat exchange performance of the heat exchanger has not been considered at all. For example, when a plate fin tube type heat exchanger used in cross flow is used to cool a predetermined space with carbon dioxide as the refrigerant and the heat receiving side as the load side, the gas-liquid is at a temperature lower than 31 ° C. It becomes a coexistence state (two-phase state) and exhibits almost the same cooling performance as a chlorofluorocarbon refrigerant (for example, refrigerants such as R410A and R22), but latent heat disappears in a high temperature region where the temperature becomes 31 ° C. or higher In addition, the cooling performance is greatly reduced as compared with the fluorocarbon refrigerant.

  The present invention has been made in order to solve the above-described conventional problems. When heat transport is performed at an operating temperature including a temperature range in which the refrigerant is in a supercritical state, the super An object of the present invention is to provide a heat transport device capable of obtaining a high cooling performance even in a high temperature region showing a critical state.

The natural circulation type cooling device of the present invention includes a heat receiving side heat exchanger that is a plate fin tube heat exchanger having a refrigerant outlet portion provided above the refrigerant inlet portion , and a position above the heat receiving side heat exchanger. A heat radiation side heat exchanger that is a plate fin tube heat exchanger provided below the refrigerant inlet portion with the refrigerant outlet portion , and a pipe that connects the heat receiving side heat exchanger and the heat radiation side heat exchanger in an annular shape, A refrigerant that is enclosed in the pipe, becomes a supercritical state at a predetermined temperature or more, and naturally circulates in the pipe due to a density change due to a temperature change in the heat receiving side heat exchanger and the heat radiating side heat exchanger, The heat-receiving-side heat exchanger and the heat-dissipating-side heat exchanger are arranged in substantially the same vertical direction in the row direction and in the horizontal direction in the horizontal direction, and the refrigerant is in a supercritical state. in the heat-receiving side heat exchanger in the temperature range When performing the replacement, and the downward flow direction of the heat exchange fluid exchanges heat with the refrigerant of the heat receiving side in the heat exchanger from above in the gravity direction along the column direction of the heat-receiving-side heat exchanger, the heat-receiving side The supercritical refrigerant in the heat exchanger changes from low temperature to high temperature, whereas the heat exchange fluid flows from the high temperature side to the low temperature side of the refrigerant to exchange heat. is there.

In the natural circulation type cooling device of the present invention, the flow direction of the refrigerant in the heat-receiving-side heat exchanger and the flow direction of the heat exchange fluid that exchanges heat with the refrigerant are counterflows, and therefore the temperature of the refrigerant and the heat exchange fluid The difference can be averaged in the heat exchanger, and even if the refrigerant temperature due to the environmental temperature reaches a high temperature range above the supercritical temperature, the heat exchange performance can be improved to prevent the overall heat transport performance from being lowered. .

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a heat transport device according to Embodiment 1 of the present invention. As shown in FIG. 1, it is comprised from the heat radiation side heat exchanger 1, the heat receiving side heat exchanger 2, and the piping 3 and 4 which connects them cyclically | annularly, and the carbon dioxide which is a natural refrigerant | coolant is enclosed as a refrigerant | coolant inside. Yes. The heat radiation side heat exchanger 1 is arranged above the heat receiving side heat exchanger 2. Hereinafter, the case where this heat transport apparatus is applied to, for example, a cooling apparatus will be described. In the cooling device, the heat radiation side heat exchanger 1 is a heat source side heat exchanger, and the heat receiving side heat exchanger 2 is a load side heat exchanger, which is arranged in the space to be cooled. In addition, the pipe for annular connection is a pipe through which the refrigerant from the heat source side heat exchanger 1 to the load side heat exchanger 2 passes through the liquid pipe 3 and from the load side heat exchanger 2 to the heat source side heat exchanger 1. A pipe through which the refrigerant passes is referred to as a gas pipe 4. Carbon dioxide sealed as a refrigerant becomes a supercritical state at a critical point (critical temperature: about 31 ° C., critical pressure: 7.3 MPa) or higher.

  In the heat exchangers 1 and 2 shown in FIG. 1, a refrigerant flow path is provided in which the refrigerant branches and flows in order to reduce pressure loss, and stable operation is possible even with a minute height difference. . That is, a plurality of refrigerant flow paths branched from the gas pipe 4 are provided inside the heat source side heat exchanger 1, and for example, four inflow pipes 7 and outflow pipes 8 are provided in FIG. Similarly, the load-side heat exchanger 2 is provided with a plurality of refrigerant channels branched from the liquid pipe 3, and in FIG. 1, for example, six inflow pipes 9 and outflow pipes 10 are provided.

Further, the connection portion between the refrigerant inlet portion of the load side heat exchanger 2 and the liquid pipe 3 and the connection portion between the refrigerant inlet portion of the heat source side heat exchanger 1 and the gas pipe 4 are respectively U-shaped as a backflow prevention means. A mold trap pipe 5 and an inverted U-shaped trap pipe 6 are provided to prevent the refrigerant from flowing backward.
The U-shaped trap pipe 5 is configured such that its lowest position is lower by, for example, 20 mm or more than the lowest position of the load-side heat exchanger 2. Further, the inverted U-shaped trap pipe 6 is configured such that its highest position is, for example, 20 mm or more higher than the highest position of the heat source side heat exchanger 1.

  In the natural circulation type cooling device, the heat source side heat exchanger 1 is installed at a higher position than the load side heat exchanger 2 because the refrigerant is circulated using the difference in gravity and density. The height difference H between the lower surface of the heat source side heat exchanger 1 and the upper surface of the load side heat exchanger 2 is set to be several tens of cm or more, for example.

  Although not shown in FIG. 1, the heat source side heat exchanger 1 is provided with a blower for the heat source side heat exchanger, and the load side heat exchanger 2 is provided with a blower for the load side heat exchanger. Outdoor air is forcibly supplied to the outer surface of the heat exchanger 1 and indoor air is forcibly supplied to the outer surface of the load-side heat exchanger 2. At this time, the flow direction of the outdoor air supplied to the outer surface of the heat source side heat exchanger 1 flows from the top to the bottom in FIG. 1 so that the outdoor air flows from the outdoor air inlet 51 to the outdoor air outlet 52. It is comprised so that it may oppose. Similarly, the flow direction of the indoor air supplied to the outer surface of the load-side heat exchanger 2 also flows from the indoor air inlet portion 53 to the indoor air outlet portion 54 in FIG. Configure to face the flow.

  FIG. 2 is a perspective view showing the heat source side heat exchanger 1 according to the present embodiment. Here, for example, a plate fin tube heat exchanger is shown as the heat exchanger. The heat source side heat exchanger 1 is a plate fin tube heat exchanger composed of plate fins 30 and tubes (heat transfer tubes) such as an inflow pipe 7 and an outflow pipe 8, and the row direction is substantially vertical and the step direction is substantially vertical. It is arranged horizontally. A plurality of, for example, four inflow pipes 7 are connected to the inlet header pipe 11, and a plurality of, for example, four outflow pipes 8 are connected to the outlet header pipe 12. By configuring the inlet header pipe 11 to be higher than the outlet header pipe 12, the plurality of refrigerant flow paths having both the inflow pipe 7 and the outflow pipe 8 at both ends have the refrigerant gravity in the heat source side heat exchanger 1. It arrange | positions so that it may flow from upper direction to the downward direction with respect to a direction.

Further, above the inlet header pipe 11, as a backflow prevention means for preventing the reverse flow of the refrigerant, particularly the liquid refrigerant in the heat source side heat exchanger 1 from flowing back to the pipe end portion 20, for example, a reverse U-shaped trap pipe 6 is connected and connected to the gas pipe 4 at the pipe end 20. On the other hand, a straight pipe having a downward gradient in the refrigerant flow direction is connected below the outlet header pipe 12 and connected to the liquid pipe 3 at the pipe end 21. In addition, heat transfer tubes such as the inflow tube 7 and the outflow tube 8 are about 6 mm to 13 mm, for example, and the inlet header tube 11, the outlet header tube 12, the liquid piping 3, and the gas piping 4 are about 7 mm to 20 mm, for example. Is done.
Also, the load side heat exchanger 2 has the same configuration as the heat source side heat exchanger 1 shown in FIG. 2, but in the case of the load side heat exchanger 2, the refrigerant passes through the inside from below in the direction of gravity. The arrangement is such that the vertical direction is reversed and the air flow direction is reversed so as to flow upward. That is, on the upstream side of the inflow pipe 9, for example, a U-shaped trap pipe 5 is provided as a backflow prevention means for preventing the reverse flow of the refrigerant, in particular, the backflow of the gas refrigerant in the load side heat exchanger 2 to the liquid pipe 3. Connected. On the other hand, the downstream side of the outflow pipe 10 is connected to a straight pipe having an upward gradient in the refrigerant flow direction, and connected to the gas pipe 4 at the pipe end. Note that heat transfer tubes such as the inflow tube 9 and the outflow tube 10 are, for example, about 6 mm to 13 mm.

The operation of the refrigerant natural circulation type cooling apparatus configured as described above will be described below.
When an electronic device that generates heat is installed in a room, the outdoor temperature usually indicates a temperature lower than the room temperature. Therefore, a case where the heat generated from the electronic device is cooled using outdoor air having a temperature lower than that of the indoor air will be described. In such use, heat transport is performed at an operating temperature including 31 ° C., which is a temperature range in which the refrigerant is in a supercritical state.

  When the refrigerant temperature reaches a low temperature range lower than 31 ° C. due to the environmental temperature, the operation of carbon dioxide circulates while changing phase between a gas state and a liquid state. The liquid refrigerant condensed by exchanging heat with the outdoor air in the heat source side heat exchanger 1 flows out from the plurality of outflow pipes 8 and descends the liquid pipe 3 by gravity. The liquid refrigerant descending the liquid pipe 3 is branched into a plurality of inflow pipes 9 through the U-shaped trap pipe 5 and flows into the load side heat exchanger 2. The gas refrigerant evaporated by exchanging heat with the room air in the load side heat exchanger 2 flows out from the outflow pipe 10 and rises in the gas pipe 4. A natural circulation cycle is formed by branching to a plurality of inflow pipes 7 through the inverted U-shaped trap pipe 6 and returning to the heat source side heat exchanger 1. The heat source side heat exchanger 1 radiates heat to the outdoor air, and the load side heat exchanger 2 receives heat from the room air to cool the room.

Here, in the high temperature region where the refrigerant is in a supercritical state, condensation and evaporation do not occur, so that no phase change occurs in the heat exchangers 1 and 2 and only a temperature change occurs. That is, the carbon dioxide in the supercritical state undergoes heat exchange with the outdoor air in the heat source side heat exchanger 1, so that the temperature is lowered, the density is increased, and the liquid pipe 3 is lowered. And it flows in into the load side heat exchanger 2, and temperature rises by exchanging heat with room air, a density becomes low and becomes light, and the gas piping 4 goes up. And a natural circulation cycle is formed by returning to the heat source side heat exchanger 1. As in the low temperature region lower than 31 ° C., the heat source side heat exchanger 1 radiates heat and the load side heat exchanger 2 receives heat from room air to cool the room.
In the heat transport in the supercritical state, the cooling performance may be lower than in the heat transport due to the phase change, but in this embodiment, the flow direction of the refrigerant in the heat exchangers 1 and 2 and the heat exchange fluid Considering the flow direction of certain indoor air, the heat exchange performance is improved to prevent the cooling performance from being lowered.

  The flow direction of the refrigerant in the heat exchanger such as the load side heat exchanger 2 or the heat source side heat exchanger 1 and the flow direction of air that is a heat exchange fluid that exchanges heat with the refrigerant are configured as counterflows. Here, the “counterflow” is a counterflow in which the flow direction of the refrigerant and the flow direction of the heat exchange fluid in the heat exchangers 1 and 2 are approximately 180 ° opposite to each other. However, it includes a configuration in which the overall refrigerant flow direction and the overall air flow direction are counterflows (orthogonal counterflows). For example, the flow shown in FIG. 3A can be a counter flow when the refrigerant flow (black arrow) and the air flow (white arrow) are viewed as an overall flow. That is, the refrigerant flows from the upper side to the lower side when viewed as a whole while flowing left and right, and the air flows from the lower side to the upper side. Such a counter flow is referred to as a pseudo counter flow. On the other hand, the orthogonal parallel flow shown in FIG. 3B is a parallel flow that is parallel when the refrigerant flow (black arrow) and the air flow (white arrow) are viewed as an overall flow. Can do. This is called pseudo parallel flow. In FIG. 3, the air flow (the white arrow) is shown vertically in the vertical direction, but the pseudo counter flow (FIG. 3A) and the pseudo parallel flow (FIG. 3) even in a slightly inclined direction. (B)).

The refrigerant flow and the air flow direction in the heat transfer tubes of the heat exchangers 1 and 2 are a pseudo counter flow as shown in FIG. 3 (a) and a pseudo parallel flow as shown in FIG. 3 (b). FIG. 4 shows a result of performance comparison of a refrigerant natural circulation cooling device constructed by the above-described method, in which R410A, which is a chlorofluorocarbon-based HFC mixed refrigerant, and carbon dioxide (CO ₂ ) are enclosed. FIG. 4 shows a condition in which the height difference between the load side heat exchanger 2 and the heat source side heat exchanger 1 is about 0.3 m, the temperature difference between the intake air in the room and the outside is constant at 10 deg, and the amount of enclosed refrigerant is constant. FIG. 5 is a graph showing the relationship of the cooling performance (W / K) to the room temperature (° C.) when the room temperature is raised. In FIG. 4, ● represents the experimental results for counter flow of CO _2, ▲ shows the experimental results of the parallel flow of CO _2, ○ shows the results of experiments in a parallel flow of R410A.

Based on the results shown in FIG. 4, when CO ₂ in parallel flow and R410A are compared, when the room temperature is 30 ° C. or lower and the temperature is low, CO ₂ shows a slightly higher cooling performance than R410A. As described above, when the room temperature is increased, the cooling performance of CO ₂ is greatly reduced as compared with R410A. This is because when the refrigerant temperature becomes 31 ° C. or higher due to the environmental temperature, CO ₂ becomes a supercritical state, and gas-liquid phase change, that is, evaporation (boiling) or condensation does not occur, so the heat transfer coefficient is lower than R410A. It is thought that it is because it does.

  Furthermore, in the configuration in which the air and the refrigerant are in parallel flow, the temperature difference between the air and the refrigerant is reduced on the outlet side of the load side heat exchanger 2 and the heat source side heat exchanger 1, and the heat exchange efficiency is reduced. The heat exchange performance will be reduced. FIG. 5 is an explanatory diagram showing temperature changes of the air 31 and the refrigerant 33 from the refrigerant inlet side to the refrigerant outlet side in the load side heat exchanger 2, for example. In the configuration in which the indoor air and the refrigerant are in parallel flow, the refrigerant in the load-side heat exchanger 2 changes from the low temperature to the high temperature from the refrigerant inlet side to the refrigerant outlet side, whereas the high temperature indoor air also flows from the refrigerant inlet side. It will flow to the refrigerant outlet side. Accordingly, since a large temperature difference is obtained on the refrigerant inlet side, a certain degree of heat exchange performance can be obtained. However, as the temperature approaches the refrigerant outlet side, the temperature difference decreases as shown in FIG. 5, and the heat exchange performance decreases. The same applies to the heat source side heat exchanger 1.

On the other hand, in the experimental result of the counterflow of CO ₂ shown in FIG. 4, the rate of decrease in the cooling performance with respect to R410A is kept small. This is because, in a configuration in which the air flow direction and the refrigerant flow direction are opposite flows, the temperature difference between the air and the refrigerant in the heat exchangers 1 and 2 can be increased on an average over the entire heat exchanger. This is because it can.
In addition, when R410A is enclosed in a counterflow configuration, a phase change occurs in the heat exchangers 1 and 2 and the refrigerant temperature at the inlet and the outlet hardly changes. Therefore, the parallel flow experiment indicated by ○ in FIG. The result is similar to the result.

FIG. 6 is an explanatory diagram showing a comparison between changes in the air temperature and the refrigerant temperature at the refrigerant inlet / outlet of the heat exchanger when CO ₂ and R410A are enclosed as refrigerant at an environmental temperature at which CO ₂ is in a supercritical state. is there. 6A shows the temperature change in the load-side heat exchanger 2, and FIG. 6B shows the temperature change in the heat source-side heat exchanger 1. FIG. The heat exchangers 1 and 2 are both configured in a counterflow, and the refrigerant natural circulation operation is performed under the condition that the temperature of the indoor intake air is 50 ° C. and the temperature of the outdoor intake air is 40 ° C. In the figure, the abscissa represents the dimensionless distance from the refrigerant inlet of the heat exchanger, the ordinate represents the refrigerant temperature and the air temperature, ● represents the CO ₂ experimental result, and ◯ represents the R410A experimental result. There were three temperature measurement positions near the refrigerant inlet, near the center, and near the outlet. Moreover, the temperature change of air is shown with a solid line arrow.

When the refrigerant is R410A, since the two-phase region exists, the refrigerant temperature changes almost constant in the heat exchangers 1 and 2, and the temperature difference from the air becomes small on the refrigerant inlet side (air outlet side). Yes. On the other hand, when the refrigerant is CO ₂ , CO ₂ is in a supercritical state at the environmental temperature of the experimental condition, so that no phase change occurs in the heat exchangers 1 and 2, and the outlet side in the heat exchangers 1 and 2 On the inlet side and on the inlet side, a temperature change (ΔT) of about 5 to 6 deg occurs, and an average large temperature difference is obtained between the air and the refrigerant over the entire heat exchanger.

In the present embodiment, in consideration of such a temperature change, as shown in FIGS. 1 and 2, in the heat source side heat exchanger 1 and the load side heat exchanger 2, the flow direction of the air and the refrigerant is changed to the counter flow. As a result, the heat exchange performance was improved in the supercritical state, and the cooling performance was prevented from being lowered. FIG. 7 shows changes in the refrigerant temperature and the air temperature in the heat exchangers 1 and 2 when the air and refrigerant flow directions are opposed in the heat source side heat exchanger 1 and the load side heat exchanger 2. In FIG. 7, 31 is the indoor air temperature, 32 is the outdoor air temperature, 33 is the refrigerant temperature in the load-side heat exchanger 2, and 34 is the refrigerant temperature in the heat source-side heat exchanger 1.
In this way, by making the flow of air and refrigerant countercurrent, the refrigerant in the supercritical state changes from low temperature to high temperature, whereas air as the heat exchange fluid flows from the high temperature side to the low temperature side of the refrigerant. Exchange heat. For this reason, the temperature difference ΔTc between the outdoor air and the refrigerant in the heat source side heat exchanger 1 and the temperature difference ΔTe between the indoor air and the refrigerant in the load side heat exchanger 2 can be increased on average. Taking an average large temperature difference over the entire heat exchanger leads to an improvement in heat exchange performance and can increase the cooling capacity.

The temperature change occurs in the heat source side heat exchanger 1 and the load side heat exchanger 2, particularly the load side heat exchanger 2, because the refrigerant is in a natural circulation type heat transport using a fluid that becomes a supercritical state at the use environment temperature. This phenomenon is unique to the device. In a vapor compression type air conditioner using a compressor, the load side heat exchanger 2 uses latent heat of vaporization, so that a temperature change occurs only in the heat source side heat exchanger 1. Therefore, the effect of improving the cooling performance when the refrigerant and air flows are opposed to each other is greater in the refrigerant natural circulation type heat transport device than in the vapor compression type air conditioner.
By improving the cooling performance, the apparatus can be reduced in size.

  In the cooling device shown in FIG. 1, both the heat source side heat exchanger 1 and the load side heat exchanger 2 have a counterflow in the flow direction of the refrigerant and air. It has the effect of increasing the cooling capacity to some extent.

  Furthermore, since the refrigerant flow path is configured so that the refrigerant in the heat source side heat exchanger 1 flows from the upper side to the lower side with respect to the direction of gravity, when carbon dioxide is used as the refrigerant, in the environment below the critical point, the heat source side The liquid refrigerant condensed in the heat exchanger 1 flows smoothly downward due to gravity, and the reverse flow of the refrigerant in the heat source side heat exchanger 1 can be prevented. Further, since the density increases as the temperature of the refrigerant decreases even at a critical point or higher, it is configured to smoothly flow downward due to gravity, and the reverse flow of the refrigerant in the heat source side heat exchanger 1 can be prevented. .

  In addition, since the refrigerant flow path is configured so that the refrigerant in the load-side heat exchanger 2 flows from below to above in the direction of gravity, when carbon dioxide is used as the refrigerant, The gas refrigerant evaporated in the heat exchanger 2 can smoothly flow upward, and the reverse flow of the refrigerant in the load side heat exchanger 2 can be prevented. Further, since the density decreases as the temperature of the refrigerant rises even above the critical point, the refrigerant flows smoothly upward, and the reverse flow of the refrigerant in the load-side heat exchanger 2 can be prevented.

In the above, an example in which a plate fin tube type heat exchanger, for example, is used as the load side heat exchanger 2 and the heat source side heat exchanger 1 is shown. However, as shown in FIG. It is also possible to use a plate heat exchanger that exchanges heat with the refrigerant, or a double-pipe heat exchanger as shown in FIG. In these cases, the refrigerant and the heat exchange fluid can be configured to have a substantially complete counter flow.
Further, the fluid that exchanges heat with the refrigerant in the load-side heat exchanger 2 is not limited to room air, and may be a liquid such as water or brine. In the heat exchange between the refrigerant and the liquid, the heat exchange performance can be improved by configuring the flow direction to be an opposite flow.
Of course, the heat source side heat exchanger 1 and the load side heat exchanger 2 do not have to be the same type of heat exchanger.

In addition, since the refrigerant flow paths of the load side heat exchanger 2 and the heat source side heat exchanger 1 have a plurality of branched refrigerant flow paths, the refrigerant is a natural circulation type cooling that has a small pressure loss and can be stably operated even with a minute height difference. An apparatus can be provided. In the present embodiment, both the refrigerant flow paths of the load-side heat exchanger 2 and the heat source-side heat exchanger 1 are configured by a plurality of branched refrigerant flow paths, but at least one of the refrigerant flow paths is a plurality of refrigerant flow paths. If it is configured to be branched into the flow path, it can be effective to some extent.
Note that the number of the plurality of refrigerant channels is not limited to the above embodiment.

In addition, backflow prevention means for preventing backflow of the refrigerant at the connection portion between the refrigerant inlet portion of the load side heat exchanger 2 and the liquid pipe 3 and the connection portion between the refrigerant inlet portion of the heat source side heat exchanger 1 and the gas pipe 4. Since the U-shaped trap pipe 5 and the reverse U-shaped trap pipe 6 are provided, it is possible to prevent the backflow of the naturally circulating refrigerant.
Note that the U-shaped trap pipe 5 and the reverse U-shaped trap pipe 6 are not limited to the above-described sizes, as long as they can prevent the refrigerant from flowing backward. In order to prevent the gas refrigerant in the load side heat exchanger 2 from flowing into the liquid pipe 3, the gas refrigerant flows back into the liquid pipe 3 upstream of the portion where the refrigerant may be gasified. What is necessary is just to provide the flow path and member which prevent this. Similarly, in order to prevent the liquid refrigerant in the heat source side heat exchanger 1 from flowing into the gas pipe 4, the liquid refrigerant flows back to the gas pipe 4 upstream of the portion where the refrigerant may be liquefied. What is necessary is just to provide the flow path and member which prevent this. For example, the trap pipes 5 and 6 can use check valves having a very small minimum operating pressure difference.
In addition, both of the backflow prevention means 5 and 6 are not necessarily required, and may not be provided in one of them or in a configuration in which backflow does not occur. For example, as shown in FIG. 1, if the flow of the refrigerant is configured from the upper side to the lower side in the heat source side heat exchanger 1 and from the lower side to the upper side in the load side heat exchanger 2, the reverse flow of the refrigerant can be prevented to some extent. it can.

  Hereinafter, a refrigerant natural circulation type cooling device having a compact configuration will be described as a heat transport device actually installed in a communication base station or the like. FIG. 9 is a configuration diagram showing the refrigerant natural circulation type cooling device according to the present embodiment. This cooling device is an integrated cooling device that is attached to a housing wall 40 such as a communication base station and in which the load side heat exchanger 2 and the heat source side heat exchanger 1 are built in the same housing. In the figure, 41 is an outdoor fan, 42 is an indoor fan, 43 is an indoor / outdoor partition plate, 44 is an outdoor air inlet, 45 is an outdoor air outlet, 46 is an indoor air inlet, and 47 is an indoor air outlet. . Carbon dioxide is sealed in the heat exchangers 1 and 2 and the pipes 3 and 4 as a refrigerant. The same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Hereinafter, in the refrigerant natural circulation type cooling apparatus using carbon dioxide as the refrigerant shown in FIG. 9, when the refrigerant temperature in the usage environment is lower than the critical point, that is, in the low temperature range where the refrigerant temperature at the environmental temperature is lower than 31 ° C. The operation of will be described. In the heat source side heat exchanger 1, the refrigerant dissipates heat to the outdoor air sucked from the outdoor air suction port 44 by the outdoor blower 41, and condenses and liquefies itself. At this time, outdoor air whose temperature has increased due to condensation latent heat from the refrigerant is blown out from the outdoor air outlet 45 to the outside air. On the other hand, the refrigerant liquefied in the heat source side heat exchanger 1 descends the liquid pipe 3 and flows into the load side heat exchanger 2. In the load-side heat exchanger 2, the refrigerant receives heat from the indoor air sucked from the indoor air suction port 46 by the indoor blower 42 and evaporates itself. At this time, the room air whose temperature has been lowered due to the latent heat of vaporization being removed by the refrigerant is blown into the room from the room air outlet 47 to cool the room. On the other hand, the refrigerant vaporized in the load-side heat exchanger 2 moves up the gas pipe 4 and returns to the heat source-side heat exchanger 1 to form a refrigerant natural circulation cycle.

The operation when the refrigerant temperature in the use environment is higher than the critical point, that is, the refrigerant temperature at the environmental temperature is 31 ° C. or higher is as follows.
In the heat source side heat exchanger 1, the refrigerant does not condense and exchanges heat with low-temperature outdoor air, and the temperature drops. Moreover, in the load side heat exchanger 2, the refrigerant does not evaporate and heat is exchanged with hot indoor air, and the temperature rises. The density of the refrigerant changes according to the temperature change, and the refrigerant circulates between the heat source side heat exchanger 1 and the load side heat exchanger 2 provided at a lower position to form a refrigerant natural circulation cycle. Is done. As in the case of the phase change of the refrigerant, the indoor air taken in from the indoor air inlet 46 is cooled by exchanging heat with the refrigerant in the load-side heat exchanger 2 and blown out from the indoor air outlet 47 into the room. Thus, the room is cooled.

In the heat source side heat exchanger 1 and the load side heat exchanger 2 shown in FIG. 9, the refrigerant and air flows in opposite directions. That is, in the heat source side heat exchanger 1, the refrigerant flows from the upper side to the lower side with respect to the direction of gravity, and the air flows from the lower side to the upper side. In the load side heat exchanger 2, the refrigerant flows from the lower side to the upper side with respect to the direction of gravity. Air flows from top to bottom.
For this reason, as shown in FIG. 7, the temperature difference between the refrigerant and the air can be increased on the average over the entire heat exchangers 1 and 2, and the refrigerant can be in a supercritical state where latent heat due to phase change cannot be expected. By improving the heat exchange performance, it is possible to prevent a decrease in cooling performance.

  In this way, in the integrated refrigerant natural circulation type cooling device attached to a housing wall such as a communication base station, carbon dioxide is used as the refrigerant, and the refrigerant in the load side heat exchanger 2 and the heat source side heat exchanger 1 By configuring the air flow direction to be a counter flow, the heat exchange performance can be improved even when the refrigerant is in a supercritical state, the cooling performance can be maintained, and the reliability can be improved.

In the above embodiment, the case where the heat receiving side heat exchanger of the natural circulation type heat transport device is used as a cooling device on the load side has been described. However, if the heat radiation side heat exchanger is on the load side, it is used as a heating device. You can also.
Further, although carbon dioxide has been described as a refrigerant exhibiting a supercritical state, the same effect can be achieved when applied to a case where the refrigerant is operated at an operating temperature including a temperature range where the refrigerant is in a supercritical state.

  As described above, in the refrigerant natural circulation type cooling device in which the load side heat exchanger, the heat source side heat exchanger, and the gas pipe and the liquid pipe connecting them are connected in an annular shape, carbon dioxide is used as the refrigerant. Since the flow direction of the refrigerant and air in the load-side heat exchanger is used as a counter flow, it is possible to provide a refrigerant natural circulation type cooling device in which a decrease in cooling performance is small even when a supercritical fluid is used.

  In addition to the load-side heat exchanger, the refrigerant and air flow directions in the heat-source-side heat exchanger are also used as counterflows, so that the refrigerant natural-circulation type cooling with little deterioration in cooling performance even when using a supercritical fluid An apparatus can be provided.

  Further, since the load side heat exchanger and the heat source side heat exchanger have a plurality of refrigerant flow paths, it is possible to provide a refrigerant natural circulation type cooling device that has a small pressure loss and can be stably operated even with a minute height difference.

In addition, a U-shaped trap pipe and a reverse U-shape that prevent the refrigerant from flowing back to the connection part between the inlet part of the load side heat exchanger and the liquid pipe and the connection part between the inlet part of the heat source side heat exchanger and the gas pipe. Since the type trap pipe is provided, the reverse flow of the refrigerant can be prevented.

  In addition, since the refrigerant flow path is configured so that the flow of the refrigerant in the load side heat exchanger and the heat source side heat exchanger is from top to bottom with respect to the direction of gravity, back flow of the refrigerant can be prevented.

  Moreover, since at least one of a plate fin tube heat exchanger, a plate heat exchanger, and a double tube heat exchanger is used as the load side heat exchanger or the heat source side heat exchanger, a gas such as air and a refrigerant are used. The counter flow can be formed either in the heat exchange with the liquid or in the heat exchange between the liquid such as water or brine and the refrigerant, and the cooling performance can be improved.

It is a block diagram which shows the heat transport apparatus which concerns on Embodiment 1 of this invention. It is a perspective view which shows the heat source side heat exchanger which concerns on Embodiment 1 of this invention. It is explanatory drawing explaining the flow of the refrigerant | coolant and heat exchange fluid which concern on Embodiment 1 of this invention. It is a graph which shows the relationship between the room temperature and cooling performance which concern on Embodiment 1 of this invention. It is explanatory drawing which shows the temperature change of the refrigerant | coolant in the heat exchanger which concerns on Embodiment 1 of this invention, and air. It is explanatory drawing which shows the temperature change of the refrigerant | coolant in the heat exchanger which concerns on Embodiment 1 of this invention, and air. It is explanatory drawing explaining the change of the refrigerant | coolant temperature in the heat exchanger which concerns on Embodiment 1 of this invention, and air temperature. It is a block diagram which shows the other example of the heat exchanger which concerns on Embodiment 1 of this invention. It is a block diagram which shows the refrigerant | coolant natural circulation type cooling device which concerns on Embodiment 1 of this invention.

Explanation of symbols

1 Heat Dissipation Side Heat Exchanger 2 Heat Reception Side Heat Exchanger 3 Piping 4 Piping 5, 6 Backflow prevention means

Claims (4)

A heat-receiving-side heat exchanger that is a plate fin tube heat exchanger with the refrigerant outlet portion provided above the refrigerant inlet portion ;
A heat dissipating side heat exchanger that is a plate fin tube heat exchanger disposed above the heat receiving side heat exchanger and having a refrigerant outlet portion provided below the refrigerant inlet portion ;
A pipe connecting the heat receiving side heat exchanger and the heat radiating side heat exchanger in an annular shape;
A refrigerant that is enclosed in the pipe, becomes a supercritical state at a predetermined temperature or more, and naturally circulates in the pipe due to a density change due to a temperature change in the heat receiving side heat exchanger and the heat radiating side heat exchanger; Prepared,
The row direction of each of the heat receiving side heat exchanger and the heat radiating side heat exchanger is arranged substantially vertically, and the step direction is arranged substantially horizontally and incorporated in the same housing,
When heat exchange is performed in the heat receiving side heat exchanger in a temperature range where the refrigerant is in a supercritical state, the flow direction of the heat exchange fluid that exchanges heat with the refrigerant in the heat receiving side heat exchanger is changed to the heat receiving side heat exchange. The supercritical refrigerant in the heat-receiving-side heat exchanger changes from low temperature to high temperature, while the heat exchange fluid is changed to the high temperature side of the refrigerant. The natural circulation type cooling device is characterized in that heat is exchanged by flowing from the low temperature side to the low temperature side. Refrigerant from the refrigerant inlet portion of the heat exchanger to the upstream pipe at the upstream side of at least one of the refrigerant inlet portion of the heat receiving side heat exchanger and the refrigerant inlet portion of the heat radiating side heat exchanger The natural circulation type cooling device according to claim 1, further comprising a backflow prevention means for preventing backflow. A heat-receiving-side heat exchanger that is a plate fin tube heat exchanger with the refrigerant outlet portion provided above the refrigerant inlet portion;
  A heat dissipating side heat exchanger that is a plate fin tube heat exchanger disposed above the heat receiving side heat exchanger and having a refrigerant outlet portion provided below the refrigerant inlet portion;
  A pipe connecting the heat receiving side heat exchanger and the heat radiating side heat exchanger in an annular shape;
  A refrigerant that is enclosed in the pipe, becomes a supercritical state at a predetermined temperature or higher, and circulates naturally in the pipe due to a density change due to a temperature change in the heat receiving side heat exchanger and the heat radiating side heat exchanger;
It is attached to the wall surface that partitions the indoor side and the outdoor side, or is disposed in the space to be cooled, and the heat receiving side heat exchanger and the heat radiating side heat exchanger are arranged substantially vertically in the respective column directions and in the horizontal direction in the step direction. A housing that is arranged and built in,
A partition plate that partitions the space inside the housing into a space in which the heat receiving side heat exchanger is provided and a space in which the heat dissipation side heat exchanger is provided;
The indoor air inlet and the indoor air provided in the casing so that the air sucked from the room flows from the lower side to the upper side in the direction of gravity along the row direction of the heat-receiving-side heat exchanger and is blown into the room. The air outlet,
Outdoor air suction port and outdoor air provided in the housing so that air sucked from the outside flows in the direction of gravity in the row direction in the heat radiation side heat exchanger from the upper side to the lower side and is blown out to the outside The air outlet,
A natural circulation type cooling device comprising: A heat receiving side heat exchanger, a heat radiating side heat exchanger disposed above the heat receiving side heat exchanger, a pipe connecting the heat receiving side heat exchanger and the heat radiating side heat exchanger in an annular shape, and the pipe Heat exchange using a natural circulation type cooling device comprising: a refrigerant that is sealed in a supercritical state at a predetermined temperature or higher; and an indoor fan that blows indoor air that exchanges heat with the refrigerant in the heat-receiving-side heat exchanger. A method,
  In a temperature range where the refrigerant is in a supercritical state, blowing the indoor air by the indoor blower so as to be opposite to the refrigerant flow direction in the heat receiving side heat exchanger;
  Heat exchange between the blown room air and the refrigerant in the heat-receiving-side heat exchanger, and circulating the refrigerant from the heat-receiving-side heat exchanger to the heat-radiating-side heat exchanger by density change due to temperature change of the refrigerant A heat exchange method using a natural circulation type cooling device.

Images