JP2005188813A - Thermo-siphon type cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermo-siphon type cooling device capable of inhibiting the lowering of cooling efficiency caused by the fluctuation of thermal load of a cooled part, and exercising superior effect on pressure-resistance and safety of a thermo-siphon piping system, with respect to a cooling device constituted by combining a thermo-siphon with a refrigeration machine. <P>SOLUTION: In this thermo-siphon type cooling device wherein a loop type thermo-siphon 3 is placed between a cool-temperature part 1b of the refrigeration machine 1 and the cooled part 2, and the cold heat obtained by the cool-temperature part is transported to the cooled part to cool the same, a refrigerant bypass circuit 6 including a buffer tank 5 is mounted at a refrigerant liquid pipe conduit 3c side of the thermo-siphon as a control means for adjusting the circulation of refrigerant of the thermo-siphon in accordance with the increase and decrease of the thermal load, the refrigerant liquid is released to the refrigerant circulating circuit from the buffer tank to increase the circulation of refrigerant when the increase of thermal load of the cooled part is detected on the basis of temperature information detected by temperature sensors 9a-9d, on the contrary, the refrigerant liquid is recovered to the buffer tank from the refrigerant circulating circuit to decrease the circulation of refrigerant when the thermal load is decreased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermosiphon cooling device suitable as a cooling device that cools a product that is mounted on a vending machine and stored in a product storage, for example.

  As the thermosyphon cooling device described above, a gravitational reflux loop thermosyphon is installed between the cooling / heating part (cold head) and the cooled part (refrigerator) of the Stirling refrigerator, and the cooling heat obtained in the cooling / heating part is provided. The thing of the structure which carried out heat transport to the to-be-cooled part and cooled the inside of a store | warehouse | chamber is known (for example, refer patent document 1).

  Further, regarding the loop-type thermosiphon laid between the cold temperature part of the refrigerator and the cooled part, the refrigerant circulation circuit is connected to the cold part of the refrigerator in a heat transfer manner, and the cooled part. It is the same as that of the present invention, and is composed of an evaporating section arranged in the section, a forward-side refrigerant liquid pipe that is connected between the condensing section and the evaporating section, and a return-side refrigerant gas pipe. The applicant previously proposed as Japanese Patent Application No. 2003-73218 (prior application 1).

  Next, the configuration and operation of the thermosiphon cooling device proposed in the prior application 1 will be described with reference to FIG. In the figure, 1 is a Stirling refrigerator, 1a is a heat radiating part of the refrigerator, 1b is a cold / warm part (cold head), 2 is a part to be cooled (for example, a product storage of a vending machine), and 3 is a Stirling refrigerator 1 A loop-type thermosiphon 4 laid between the cooled portion 2 and the inside of the cooled portion 2 is a fan inside the cabinet.

  Here, the thermosiphon 3 includes a condensing unit 3a disposed in the cooling / warming unit 1b of the Stirling refrigerator 1, and an evaporation unit disposed in the chamber of the cooled unit 2 (a fin- A refrigerant circulation circuit is configured by a tube-type heat exchanger) 3b, a forward-side refrigerant liquid pipe 3c that is connected between the condensing unit 3a and the evaporation unit 3b, and a return-side refrigerant gas pipe 3d. An appropriate amount of carbon dioxide, for example, is sealed as a working fluid refrigerant in the refrigerant circuit. In addition, in order to circulate the refrigerant | coolant which changes a phase between the condensation part 3a and the evaporation part 3b of a refrigerant | coolant circulation circuit using the positional energy difference of gravity, the height drop H between the condensation part 3a and the evaporation part 3b is carried out. Is set, and the refrigerant liquid pipeline 3c on the forward path side is piped below the refrigerant gas pipeline 3d on the return path side. Further, the condenser 3a, the refrigerant liquid pipe 3b, and the refrigerant gas pipe 3c of the refrigerant circulation pipe are covered with a heat insulating material to suppress heat loss as much as possible.

The operating principle of the thermosyphon described above is well known, and the refrigerant sealed in the thermosiphon 3 is condensed and liquefied in the condenser 3a by heat exchange with the cold generated in the cold / hot part 1b as the refrigerator 1 is operated. After that, it flows downward by gravity and moves to the evaporator 3b via the refrigerant liquid conduit 3c. The liquid refrigerant that has moved to the evaporating section 3b is boiled and evaporated by heat exchange with the air in the chamber of the cooled section 2 to change phase from liquid to gas, and the refrigerant gas that has become gas moves upward in the tube of the evaporating section 3b. It moves and returns from the outlet of the evaporator 3b to the condensing part 3a through the refrigerant gas line 3d, and repeats a cooling cycle in which heat is dissipated to the cold / hot part 1b of the refrigerator 1 and condensed again. By this cooling cycle, the inside of the cooled portion 2 is cooled to a low temperature.
JP 2001-33139 A

  By the way, in the conventional thermosiphon operated by previously charging a predetermined amount of refrigerant in the refrigerant circuit as described above, there is a problem that the cooling efficiency is lowered when the heat load of the cooled portion is changed.

  That is, looking at the change in the thermal load fluctuation of the cooled part taking the product storage of the vending machine as an example, the thermal load of the cooled part is large in the state immediately after loading the room temperature product in the warehouse, and from here If the inside cooling proceeds and the product temperature reaches a low temperature (for example, around 10 ° C.), the heat load decreases.

  In this case, if the heat load of the cooled part increases with a fixed amount of the refrigerant in the thermosyphon matched to the heat load in the steady-state cold state, the boiling evaporation amount of the refrigerant in the evaporation part increases, On the contrary, a large amount of refrigerant gas that has moved from the evaporation section is condensed and liquefied in the condensing section, and the liquid level rises, so that the liquid level difference between the two increases. In addition, when the operation state with a large heat load is reached, the evaporating unit completes the boiling evaporation of the refrigerant on the near side of the outlet and becomes a dryout heat flux, so that the effective heat exchange area involved in the heat transfer of the boiling evaporation is increased. It decreases and heat transfer efficiency falls. Further, since the liquid level is increased in the condensing part, the heat exchange area between the refrigerant gas that has returned to the condensing part and the cold / hot part of the refrigerator is reduced accordingly. For this reason, the total cooling efficiency of the cooling device including the refrigerator and the thermosiphon is lowered.

  In addition, when carbon dioxide, which is a natural refrigerant, is used as a thermosyphon refrigerant in terms of protecting the global environment (ozone layer), the pressure level (condensation pressure) of the carbon dioxide refrigeration cycle is much higher than that of other refrigerants. Therefore, the safety of the thermosiphon piping system, the condensing part, and the evaporation part with respect to the pressure-resistant structure becomes a problem. Therefore, when carbon dioxide gas is used as the refrigerant, it is desirable that the amount of refrigerant liquid directly involved in the cooling cycle be as small as possible in order to keep the pressure resistant design level of the thermosiphon piping system, condensing and evaporation section low.

  The present invention has been made in view of the above points, and its purpose is to suppress a decrease in cooling efficiency due to fluctuations in the thermal load of a portion to be cooled, and to a cooling device that combines a thermosiphon with a refrigerator. An object of the present invention is to provide a thermosiphon cooling device that exhibits excellent effects in terms of pressure resistance and safety of a thermosyphon piping system that employs carbon dioxide as a refrigerant.

In order to achieve the above object, according to the present invention, a loop-type thermosiphon is laid between a cold temperature part of a refrigerator and a cooled part, and the cold heat obtained in the cold temperature part is transported to the cooled part. A thermosiphon type cooling device that cools the refrigerant, and the refrigerant circulation circuit of the thermosyphon is disposed between the condensing unit disposed in the cold temperature part of the refrigerator and the evaporating unit disposed in the cooled part, and between the condensing unit and the evaporating unit It consists of a refrigerant liquid line on the forward path and a refrigerant gas line on the return path that are connected and piped, and the refrigerant is enclosed in the system of the refrigerant circulation circuit.
As a control means for adjusting the refrigerant circulation amount of the thermosyphon according to the thermal load increase / decrease of the cooled part, a bypass circuit including a buffer tank for the refrigerant liquid is provided on the refrigerant liquid pipeline side of the refrigerant circulating circuit, Based on the temperature information detected from each part of the refrigerant circulation circuit, when the heat load of the cooled part increases, the refrigerant liquid is discharged from the buffer tank to the refrigerant circulation circuit to increase the refrigerant circulation amount, and conversely the heat load is reduced. In this case, the refrigerant liquid is recovered from the refrigerant circulation circuit to the buffer tank to reduce the refrigerant circulation amount (Claim 1).

The buffer tank is configured in the following manner in order to smoothly discharge and collect the refrigerant liquid.
(1) The buffer tank is arranged at a position lower than the refrigerant liquid line of the refrigerant circulation circuit, and an opening / closing valve is provided on the inlet and outlet sides of the buffer tank, and the opening / closing valve is controlled to open and close between the refrigerant liquid line and the buffer tank. The liquid refrigerant is collected and released by (Claim 2).
(2) A heater is provided in the buffer tank, and when the liquid refrigerant is discharged from the buffer tank to the refrigerant circulation circuit, the liquid refrigerant is released by increasing the refrigerant pressure in the tank by heating the heater (claim) Item 3).
(3) When the outlet side bypass pipe connected to the buffer tank is pulled out from a position higher than the inlet side bypass pipe and the liquid refrigerant is collected from the refrigerant circulation circuit to the buffer tank, it is accumulated in the tank. The refrigerant gas is discharged through the outlet side bypass pipe, and the liquid refrigerant is recovered through the inlet side bypass pipe (claim 4).
(4) A check valve is connected to each of the inlet and outlet bypass pipes piped to the buffer tank to prevent unnecessary reverse flow of the refrigerant during refrigerant recovery and discharge.

  According to the configuration of the present invention in which a bypass circuit including a buffer tank is provided in the refrigerant circulation circuit of the loop-type thermosyphon, and the refrigerant liquid is discharged and collected in accordance with the thermal load fluctuation of the cooled part. The amount of refrigerant that circulates between the condenser and evaporator of the thermosyphon in the cold operation state can be adjusted to an appropriate amount corresponding to the heat load of the part to be cooled, thereby improving the cooling efficiency and the refrigerator Power consumption can be reduced.

  In addition, excessive refrigerant liquid is recovered from the refrigerant circulation circuit to the buffer tank in accordance with fluctuations in the heat load, so that the refrigerant pressure in the refrigerant circulation circuit can be prevented from excessively increasing, which makes the thermosiphon The pressure resistance design level of the piping system, condensing and evaporating parts can be lowered, ensuring high safety and reliability, and reducing manufacturing costs.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on the examples shown in FIGS. In addition, in the figure of an Example, the same code | symbol is attached | subjected to the member corresponding to FIG. 4, and the description is abbreviate | omitted.

  The thermosiphon cooling device shown in FIG. 1 (a) is between the cool / warm portion 1b of the Stirling refrigerator 1 and the cooled portion 2 (for example, the vending machine storage) as in the conventional configuration described in FIG. In the embodiment shown in the drawing, the refrigerant liquid on the forward path side of the refrigerant circulation circuit of the cooling / warming part 1b and the cooled part 2 of the Stirling refrigerator 1 is provided. A refrigerant bypass circuit 6 including a buffer tank 5 that stores refrigerant liquid is newly provided in the pipe line 3c.

  Here, the buffer tank 5 is provided with a heater (electric heater) 5a, and is disposed at a position lower than the refrigerant liquid line 3c. In addition, the inlet and outlet side pipes 6a and 6b connected to the buffer tank 5 and drawn back and forth are branched and connected to the thermosiphon 3 at points upstream and downstream of the refrigerant liquid pipe 3b, respectively. The refrigerant bypass circuit 6 is configured by connecting on-off valves 7a and 7b and check valves 8a and 8b to the side pipe lines 6a and 6b, respectively.

  Further, temperature sensors 9a to 9d are arranged in the chamber of the cooled portion 2, the inlet and outlet ends of the evaporator 3b, and the inlet end of the condensing unit 3a, and the temperature information detected by each temperature sensor is shown in FIG. ), And the temperature information is used to determine whether the amount of refrigerant circulating in the refrigerant circulation circuit of the thermosiphon 3 is excessive or insufficient as described later (see the flowchart in FIG. 3). On the basis of this, the on-off valves 7a and 7b and the heater 5a of the buffer tank 5 are energized to release and collect the refrigerant liquid.

Next, the control operation of the refrigerant bypass circuit 6 corresponding to the heat load increase / decrease of the cooled part 2 will be described based on the control operation flowcharts shown in FIGS. 2 (a) to 2 (c) and FIG. First, FIG. 2A shows a refrigerant in the thermosiphon 3 in a steady cold state where the heat load is stable (a product stored in the product storage of the vending machine is kept at a predetermined product temperature). Represents the current flow. That is, as described in FIG. 4, the refrigerant of the thermosiphon 3 condensed and liquefied in the condenser 3a by heat exchange with the cold / hot part 1b of the Stirling refrigerator 1 passes through the refrigerant liquid line 3c by gravity and evaporates 3b. Move to (Fined tube heat exchanger), heat exchange with the heat load of the cooled part 2 and move upward in the evaporation part while boiling and evaporating, completing evaporation near the outlet of the evaporation part 3b After that, the cooling cycle of returning to the condensing unit 3a through the refrigerant gas pipe 3d on the forward path side is repeated. In this heat load stable operation state, the inlet side temperature and the outlet side temperature of the evaporation section 3b are substantially the same temperature, so that the on-off valves 7a and 7b of the refrigerant bypass circuit 6 are both closed as shown in the flowchart of FIG. Until then, the heater 5a of the buffer tank 5 is also de-energized.
On the other hand, when the thermal load increases from the above operating state (the state immediately after the product is stored in the product storage of the vending machine), the temperature of the evaporation unit 3b rises following the internal temperature of the cooled unit 2. Therefore, the specific enthalpy of the carbon dioxide gas that is the refrigerant increases and the density decreases. As a result, as compared with the operation state of FIG. 2 (a) where the heat load is small, the refrigerant liquid that has moved to the evaporation unit 3b has completed its boiling evaporation before reaching the outlet of the evaporation unit 3b, and is dry out. Therefore, the outlet side temperature of the evaporation unit 3b rises higher than the inlet side temperature, and the inlet side temperature of the condensing unit 3a where the refrigerant recirculates in a dry vapor state is higher than the outlet side temperature of the evaporation unit 3b. .
When this heat load increase operation state is entered, the heater 5a of the buffer tank 5 is energized by a command from the control device 10 according to the flowchart of FIG. 3, and the internal pressure of the buffer tank 5 is increased by heating the heater. Moreover, the on-off valve 7b connected to the outlet side pipeline 6b of the bypass circuit 6 is opened by a command from the control device 10. As a result, the refrigerant liquid 11 stored in the buffer tank 5 is discharged by receiving the internal pressure of the tank, and is introduced into the refrigerant liquid pipe 3b of the thermosiphon 3 through the outlet side pipe 6b as shown in FIG. 3 (b). To be replenished. Accordingly, the amount of refrigerant directly involved in the cooling cycle of the thermosyphon 3 increases, and as a result, heat transfer by boiling evaporation of the refrigerant in the evaporating section 3b is performed to the outlet, thereby improving the cooling efficiency. .
Next, the internal cooling proceeds from the operation state of the high heat load described in FIG. 3B so that the heat load of the cooled portion 2 decreases, and the internal temperature decreases to a predetermined cool temperature T. Then, the refrigerant liquid that has moved to the evaporating unit 3b rises in the evaporating unit while being in a supercooled liquid state, and even if it reaches the outlet end of the evaporating unit, boiling evaporation does not complete and returns to the condensing unit 3a. For this reason, in the evaporation part 3b, heat exchange performance with the heat load by the boiling heat transfer of a refrigerant | coolant cannot fully be exhibited, but cooling efficiency falls. Further, the refrigerant circulation amount of the thermosiphon 3 is also reduced, the refrigerant liquid level difference between the condensing unit 3a and the evaporating unit 3b is reduced, and the outlet side temperature and the inlet side temperature of the evaporating unit 3b are approximately the same. Become.
In such an operating state, according to the flowchart of FIG. 3, the control device 10 determines the magnitude of the thermal load from the detected value of the internal temperature of the cooled part 2, and then determines the outlet side temperature of the evaporation unit 3 b and the condensing unit. On the condition that the inlet side temperature of 3a is substantially the same, the on-off valves 7a and 7b on the inlet side and outlet side connected to the refrigerant bypass circuit 6 are opened. Thereby, the pressure of the refrigerant liquid line 3c of the thermosiphon 3 and the internal pressure of the buffer tank 5 are balanced, and part of the refrigerant liquid that has flowed down from the condenser 3a to the refrigerant liquid line 3c. Flows into the buffer tank 5 through the inlet line 6a of the bypass circuit 6 and is stored in the tank as it is. As a result, the amount of refrigerant liquid moving to the evaporation unit 3b through the refrigerant liquid line 3c is reduced, and in accordance with this, in the evaporation unit, the boiling heat transfer of the refrigerant is performed in substantially the entire region from the inlet to the outlet, Since the condensation heat transfer area in the condensing part 3b also increases, the total cooling efficiency as a cooling device improves.
In this case, the outlet side pipe 6b of the bypass circuit 6 connected to the buffer tank 5 is opened at a position higher than the inlet side pipe 6a, so that the refrigerant staying on the liquid surface in the buffer tank. The gas returns to the refrigerant circulation circuit of the thermosiphon 3 through the outlet side pipe 6b. Further, since the check valves 8a and 8b are inserted and connected in series with the on-off valves 7a and 7b on the inlet side pipe 6a and the outlet side pipe 6b of the bypass circuit 6, the refrigerant liquid pipe of the thermosyphon 3 There is no possibility that the refrigerant flows back to and from 3c.
And if the inlet side temperature and outlet side temperature of the evaporation part 3b become comparable, the on-off valves 7a and 7b of the bypass circuit 6 will be closed. Thereby, the thermosiphon 3 returns to the driving | running state of Fig.3 (a).
In addition, in the vending machine product storage to which the thermosiphon cooling device is applied, the heat load increases immediately after the product is replenished, but the rate of closing the time is small when viewed from the overall operating time of the vending machine. The majority of the operation time is a steady cold operation at a low load in which the product temperature of the product stored in the warehouse is lowered to a predetermined temperature. Therefore, as described above, the amount of refrigerant liquid in the thermosiphon is adjusted in response to the increase or decrease in the thermal load, and in the normal cold operation state, surplus refrigerant liquid is recovered from the thermosiphon refrigerant circulation circuit to the buffer tank, Even when carbon dioxide gas with high operating pressure is used as the refrigerant, the pressure in the refrigerant circuit during steady operation can be kept relatively low, thereby reducing the pressure level required for the thermosiphon piping system and heat exchange section. In addition to improving safety and reliability, the cost of the cooling device can be reduced.
In the illustrated embodiment, a Stirling refrigerator is used as the refrigerator of the cooling device. However, the present invention is not limited to this, and a vapor compression refrigerator or an electronic refrigerator using a Peltier element is used as the refrigerator. It is also possible to adopt. In addition to the product storage of the vending machine, the cooling device can be used for cooling a CPU used in, for example, a large-capacity electronic device, and further to an air conditioner.

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It is a block diagram of the thermosiphon type cooling device by the Example of this invention, (a) is a refrigerant circuit diagram, (b) is a figure showing the control system with respect to the refrigerant bypass circuit in (a). In the operation explanatory diagram of FIG. 1, (a), (b), and (c) are diagrams showing refrigerant flow states at the time of steady heat load, when heat load is increased, and when heat load is reduced, respectively. The figure showing the flowchart of the control action corresponding to Drawing 2 (a)-(c) Refrigerant circulation circuit diagram of conventional thermosiphon cooling device

Explanation of symbols

1 Stirling refrigerator (refrigerator)
DESCRIPTION OF SYMBOLS 1b Cold / warm part 2 Cooled part 3 Thermosyphon 3a Condensing part 3b Evaporating part 3c Refrigerant liquid line 3d Refrigerant gas line 5 Buffer tank 6 Refrigerant bypass circuit 6a Inlet side line 6b Outlet side line 7a, 7b On-off valve 8a, 8b Check valves 9a to 9d Temperature sensor 10 Controller 11 Refrigerant liquid

Claims (6)

A thermosiphon-type cooling device in which a loop-type thermosyphon is installed between a cold temperature part and a cooled part of a refrigerator, and the cold heat obtained in the cold temperature part is transported to the cooled part for cooling. The refrigerant circulation circuit of the condenser is disposed in the cooler / warm part of the refrigerator, the evaporator disposed in the cooled part, the refrigerant liquid conduit on the forward path, which is connected and connected between the condenser and the evaporator, and It consists of a refrigerant gas line on the return side, and in which the refrigerant is sealed in the system of the refrigerant circuit,
As a control means for adjusting the refrigerant circulation amount of the thermosyphon according to the thermal load increase / decrease of the cooled part, a bypass circuit including a buffer tank for the refrigerant liquid is provided on the refrigerant liquid pipeline side of the refrigerant circulating circuit, Based on the temperature information detected from each part of the refrigerant circulation circuit, when the heat load of the cooled part increases, the refrigerant liquid is discharged from the buffer tank to the refrigerant circulation circuit to increase the refrigerant circulation amount, and conversely the heat load is reduced. In this case, the thermosiphon cooling device is characterized in that the refrigerant liquid is collected from the refrigerant circulation circuit into the buffer tank to reduce the refrigerant circulation amount. 2. The cooling device according to claim 1, wherein the buffer tank is disposed at a position lower than the refrigerant liquid pipe line of the refrigerant circulation circuit, and an open / close valve is provided on the inlet and outlet sides of the buffer tank and connected to the refrigerant liquid pipe. Thermosiphon cooling device. 3. The thermosiphon cooling device according to claim 2, wherein a heater is attached to the buffer tank. 3. The thermosiphon cooling device according to claim 2, wherein the outlet side bypass pipe connected to the buffer tank is drawn from a position higher than the inlet side bypass pipe. 5. The thermosiphon cooling device according to claim 4, wherein a check valve is connected to each of the inlet and outlet bypass pipes. 2. The cooling device according to claim 1, wherein the refrigerant sealed in the thermosyphon is carbon dioxide.

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