SE518336C2 - Temperature control device and method for controlling the temperature of such a device - Google Patents

Abstract

The present invention relates to a temperature control system, especially a thermosiphon system (301), with controllable refrigeration capacity, comprising an evaporator (303), a condenser (305), a rise pipe (307), a fall pipe (309) and a refrigerant medium, the refrigerant medium being arranged to evaporate and take up heat in the evaporator, rise in the rise pipe, condense and emit heat in the condenser and fall back to the evaporator in the fall pipe. The invention comprises a container (311), a branch pipe (313), a heater (315), a contact body (317) and a cooling medium, the branch pipe being connected to the fall pipe (309) and to the container. The heater is thermally connected both to the container (311) and the contact body is thermally connected to the container and to the cooling medium. The temperature control system is arranged to adjust its refrigeration capacity to the present refrigeration need by regulation of the power of the heater. The cooling medium can consist of condensed refrigerant medium in the fall pipe or of an external refrigerant medium, especially surrounding air.

Description

Evaporator 205 of the thermosyphon. This absorbs heat from the air as the refrigerant evaporates. Cold air is returned to the magazines and heated. The heat supplied to the evaporator is emitted at the thermosiphone's condenser 209 and. occupied by, for example, the outdoor air. Note that the thermosiphon's evaporator and condenser must be placed separately from each other.

An alternative to this type consists of outdoor cabinets with self-convection, whereby the evaporator is placed in direct connection to the circuit boards (not shown in the figures). The condenser is placed higher in a space that is self-ventilating, ie. has direct contact with the outdoor air.

Another problem with outdoor applications is that the cabinets sometimes have to be cooled and sometimes heated depending on the temperature of the ambient air. The solution that has been used so far is to dimension the cooling for the highest intended outdoor temperature, but at the same time provide the cabinets with electric heating elements, so that the lowest intended outdoor temperature does not cause operational disturbances. Using outdoor cabinets that are both heated and cooled at the same time is of course both an expensive and energy-consuming solution. Another problem with a thermosiphone circuit is that the refrigerant can leak out. However, this can to some extent be compensated for by oversizing the amount of refrigerant slightly.

DISCLOSURE OF THE INVENTION An object of the present invention is to obtain a simple and reliable temperature control system, in particular a thermosyphon system, the cooling capacity of which can be controlled. Another object of the invention is to obtain an energy-efficient temperature control system.

Another purpose is to obtain a temperature control system with a built-in refrigerant buffer.

These objects and others are achieved according to one aspect of the invention with a temperature control system, in particular a thermosyphon system, with controllable cooling capacity, comprising an evaporator, a condenser, a riser, a downcomer and a refrigerant, the refrigerant being arranged to evaporate and absorb heat in the evaporator. rise in the riser, condense and emit heat in the condenser and fall back to the evaporator in the downcomer. The invention comprises a container, a manifold, a heater, a contact body and a cooling medium. The manifold is connected to the downcomer and to the container. The heater is thermally connected to the container and the contact body is thermally connected both to the container and to the coolant. The temperature control system is arranged to dynamically adapt its cooling capacity to the current cooling demand by regulating the heater's power.

The refrigerant may consist of condensed refrigerant in the downcomer or of an external refrigerant, especially ambient air.

The cooling capacity depends on how much refrigerant is present in the evaporator-condenser riser-downpipe system, which is controlled by the heater's power: the higher the power, the more refrigerant is boiled and the more liquid is forced into the evaporator-condenser-downpipe-downpipe system and the lower cooling power obtained.

Thus, the heater is advantageously arranged to heat the container with an increasing power in case of a decreasing cooling need and with a decreasing effect in case of an increasing cooling need. .v u 10 15 20 25 518 336 4 Preferably, the container, manifold, heater and contact body are thermally insulated.

The heater can be controlled with a thermostat that senses some temperature in the system. Alternatively, the heater may be a temperature-dependent resistor connected in an electrical circuit, in particular a PTC resistor.

According to another aspect of the invention, said temperature control system may be used as a refrigerant buffer in case of leakage. In this case, the refrigerant must consist of condensed refrigerant in the downcomer. The heater is arranged to always heat the container with at least a small threshold power, which power is adapted so that the temperature in the container, when operating at high temperature, is below the boiling point. When the amount of liquid in the system evaporator-condenser-riser-downpipe becomes smaller, the subcooling in the downpipe decreases. The result is that the temperature increases in the container and then liquid is decoction whereby p.g.a. the increased pressure liquid is forced out into the system evaporator-condenser-riser ~ downpipe. With appropriately selected parameters regarding threshold power, refrigerant, container contact body and the forced liquid compensates for the leakage.

An advantage of the present invention is that it is simple, inexpensive and reliable as it lacks moving mechanical parts.

A further advantage of the invention is that a combined temperature control and refrigerant buffer can be obtained.

More advantages of the invention appear in the following description. DESCRIPTION OF THE FIGURES The invention is described in more detail below with reference to Figs. 3-8, which are shown only to illustrate the invention, and should therefore not in any way limit it.

Fig. 1 shows a thermosiphon according to the prior art.

Fig. 2 shows a thermosiphon-cooled outdoor cabinet with internal fan circulation according to prior art.

Fig. 3 shows a thermosiphon with cooling capacity control according to an embodiment of the present invention.

Fig. 4 shows a thermosiphon with cooling capacity control according to an alternative embodiment of the present invention.

Fig. 5 shows details of a thermosiphon with cooling capacity control as well as examples of temperature conditions and liquid levels in control according to the invention.

Figs. 6a-c show different examples of how a thermosyphon container can be cooled according to the invention.

Fig. 7 shows an example of how circuit boards mounted in cassettes can be cooled with a thermosiphon according to the invention.

Fig. 8 shows an example of how circuit boards in a radio base station can be cooled with a thermosyphon according to the invention.

PREFERRED EMBODIMENTS In the following description, for the purpose of explaining and not limiting the invention, specific details are set forth such as particular applications, techniques, etc., to provide a clear understanding of the invention. It will be apparent to those skilled in the art, however, that the invention may be embodied in other forms than those set forth in the specification.

Fig. 3 shows a thermosiphon system 301 filled with a two-phase refrigerant 321 with temperature control according to a preferred embodiment of the present invention. The system includes an evaporator 303, a condenser 305, a riser 307 for evaporated liquid, a downcomer 309 for condensed steam and a refrigerant container 311.

The container is connected via a branch pipe 313 to the downcomer 309. In contact with the container 311 there is an electric heating element 315 and a thermally conductive contact body 317 which also abuts against the downcomer. In addition, in order to prevent heat exchange with the environment, the container is insulated 319.

The manifold 313 may alternatively be connected to the container 311 and the downcomer 309 as shown in Fig. 4.

The function of the thermosyphon according to the invention is described below in connection with Fig. 5.

In addition, the thermosiphon condenser 305 is shown separately from the other components. A temperature diagram shows the temperature in the downcomer, in the contact body, and in the refrigerant tank for two different power positions C) and @) of the heater. Corresponding liquid levels in the refrigerant container and condenser are also indicated.

The liquid flowing through the downcomer 309 always has a temperature which is some degree below the boiling point of the liquid. If only a small threshold power is emitted by the electric heater (ie in power mode CD), all the gas in the container will condense, ie. the container is completely filled with liquid (level CD). Liquid. u ... sou n 10 15 20 25 518 336 7 the amount in the system evaporator-condenser-riser-downpipe is then adapted for a minimum amount of liquid in the condenser (level CU. In this position the thermosiphon has its maximum cooling function.

When the electric heater is activated, and if the output power is greater than the power lost to the environment (ie power mode ®), heat will be conducted to the downcomer via the contact body. This heat flow creates a temperature difference in the contact body which means that the temperature of the downcomer is always lower than the temperature of the refrigerant container, see the temperature diagram in Fig. 5.

As the power of the heater increases, the temperature in the refrigerant tank rises. Some of the refrigerant then boils off, which means that a cushion of gas is formed at the top of the container. As a result, the liquid displaced by the gas cushion is forced out into the evaporator-condenser-downpipe-downpipe system, whereby the liquid level drops (to level ®). The liquid level in the thermosiphon condenser will then rise (to level CU, which results in a greater subcooling of the liquid. When the subcooling becomes as large as the temperature drop in the contact body, the decoction in the container ceases.

As the condensate's gaseous surface of the condenser decreases, the temperature difference with respect to the environment will increase, which means that the system stabilizes around a higher boiling point, see the temperature diagram in Fig. 5.

The power control can in principle be operated as long as the condenser is filled with liquid, whereby the function of the thermosyphon ceases completely.

This simple and uncomplicated control principle means that the down-regulation of the cooling effect will be approximately proportional to the power applied to the container, which provides a stable regulation.

It should be noted that the temperature difference that occurs between the refrigerant in the container and the supercooled liquid in the downcomer is given by the heat resistance of the contact body in series with the heat resistance for boiling in the container and the heat resistance for convection in the downcomer. However, the latter two heat resistances are small in relation to the heat resistance in the contact body. However, the principle of regulation according to the invention would work even if this were not the case. The requirement is that the total heat resistance when it is transmitted through an effect that is less than the subcooling effect creates a temperature difference that is equal to the subcooling of the liquid.

Also note that the refrigerant container should be insulated from the outside environment. Otherwise there is a risk that the container will not be completely filled. of 'liquid when the heater is switched off. and. then the regulation will not work as intended. This risk occurs when the environment has a high temperature and there is an influx of heat to the container. If, on the other hand, the refrigerant in the container has a temperature which is higher than the ambient temperature, a heat exits from the container to the environment. However, this can be compensated for by a higher effect on the heater.

The power needed to drive the liquid out of the container depends on how quickly the device is to regulate. For an outdoor cabinet, a thermal time constant of about ten minutes can be a reasonable value. With a correct dimensioning of the thermal resistance in the contact body and the insulation, the heat demand of the heater will then be very small in relation to the power developed in the cabinet. For example, a heat output of 10 W, u ø Q I n | o. 10 15 20 25 518 336 9 be more than sufficient for a total cooling power of 500 W.

An obvious way to control the container heater 315 is to use a thermostat that senses some temperature in the system.

Another very simple temperature control is obtained by allowing the heater to consist of a PTC resistor connected in an electrical circuit.

This type of resistor is temperature dependent and in principle has a switching temperature above which the resistance increases sharply with temperature. The control device then becomes very simple.

The dimensioning of the thermosyphon system according to the invention, i.e. of the subcooling, the contact body, the insulation of the container, the time constant of the control and the heat supplied to the container must be adapted for an optimal function.

Figs. 6a-6c show different forms of cooling medium for cooling the container 311.

Fig. 6a shows the already described alternative of cooling with subcooled liquid in the downcomer 309, which is in thermal contact with the insulated container via the contact body 317. This alternative works well if the temperature of the container is higher than its ambient temperature. If this is not the case, problems with external heating may occur, especially if small containers are used.

Fig. 6b shows an alternative with an external cooling medium 601, which can for instance consist of self-convection of ambient air, especially if the thermosiphon is placed outdoors. This coolant is in thermal contact with the container 311 via a contact body 603. The disadvantage of this type of cooling is that it becomes very uneven as the external coolant varies greatly in temperature. The power of the heater must therefore be able to be regulated within o s Q n | «U. 10 15 20 25 518 336 10 a large range. Simple solutions such as heating with a PTC resistor can then be difficult to get to work.

Fig. 6c shows an alternative with cooling with subcooled liquid which partially surrounds the container 311. The thermosiphon downpipe 611 with subcooled liquid has a helical shape. part in which the container is located. The container is surrounded by a metal jacket 613 which in turn is surrounded by a filling 615 which acts as a contact body and against which the downcomer abuts. Solutions such as this with supercooled liquid that partially or completely surrounds the container work very well and safely in all environments.

Another alternative (not shown in the figures) is that the entire construction of downpipe containers is integrated in a single so-called roll-bond plate. Such an alternative is particularly suitable for containers with a small volume.

Another of the problems with a thermosiphon according to the prior art is that the refrigerant can leak out for some reason. Large leaks are easily detected in production. However, extremely small leaks, the impact of which is only felt after several years, are much more difficult to detect. In addition, damage can occur after installation. In a normal household refrigerator, the refrigerant length is dimensioned so that you can manage a reasonable service life with a leakage of a few grams of refrigerant per year. Some type of refrigerant buffer is always needed in a thermosyphon system.

It would be an advantage if the container in the thermosyphon system according to the invention can also be used as a refrigerant buffer.

This is achieved by the heater always emitting a certain small threshold effect. Normally this effect is so small that the temperature in the container is below the boiling point. However, if the amount of liquid in the evaporator-condenser-riser-downpipe system becomes 10 15 20 25 518 336 ll p o u | o «an very small reduces the subcooling in the downcomer. The temperature in the container then rises and at a given liquid level reaches the boiling point whereby liquid is decocted. Some of the liquid in the container will then be forced out into the evaporator-condenser-riser-downpipe system.

In a thermosyphon system without a liquid buffer, the amount of liquid can be controlled by measuring the subcooling of the liquid coming from the condenser. The subcooling decreases if the amount of liquid in the thermosyphon system and thus the condenser decreases. However, in some men the connection is affected by the total heat load in the system.

At high heat load, the proportion of liquid in the condenser is slightly higher than at low heat load. Therefore, comparative measurements should be made at equal heat loads.

If you use the thermosyphon system according to the invention, this type of control can be done if you turn off the heater completely.

In order to detect leaks in a functioning system, it should be sufficient to carry out such a control measurement once or twice. The control can be done once a year, which should be completely feasible. also performed with a certain small threshold effect on the heater.

However, the control itself should be switched off, which means that the measurement is preferably performed when the external ambient air temperature is high.

Fig. 7 shows an application of the thermosiphon according to the invention with refrigerant container. Circuit boards 701 mounted in cassettes 703 are cooled with the thermosiphon evaporator 705 genonx that they are in contact with side beams 707 in which the cassettes 703 are mounted.

The losses in a stack 709 with cassettes can be quite high.

The thermosiphon condenser 711 should then be cooled with a fan 713.

The evaporators 705 are preferably made of roll bond plates. 10 15 20 25 518 336 12 The thermosiphon's refrigerant container 715 is advantageously placed together with the evaporators and the stack of cassettes in a space with insulation 717 so as not to cause excessive disturbances from a varying outdoor temperature. Fig. 8 shows another application of the thermosiphon according to the invention with refrigerant container. Here the thermosiphon is used in a smaller radio base station 800 containing only one circuit board. The thermosiphon condenser 801 is self-convection cooled (with an air flow 802 from below) and integrated in the upper half of a heat sink element 803.

The evaporator 805 preferably consists of a roll bond plate which abuts against circuit boards 806 located in the base station or against individual components 806a. The refrigerant container 807 is shown greatly enlarged in Fig. 8.

The heat emitted from the lower part of the flange element may be conducted through the bottom plate of the flange element (not shown in Fig. 8). Despite the fact that the level of the condenser outlet is below the highest point of the evaporator, a satisfactory circulation of refrigerant is obtained. This has been verified experimentally for a thermosyphon. Note, however, that the thermosiphon should contain a very small amount of refrigerant.

The evaporator can i.a. is designed according to the alternatives shown in the detail views in Fig. 8 at the bottom left 805 'and at the bottom right 805 ". According to the former alternative, a roll bond plate 805' is folded around the circuit board 806 with components 806a. contact body 809 is placed between these components and the evaporator. In this way, high point effects can be diverted. contact with components 806a on the front of the circuit board.

The present invention as described herein solves the problems associated with the prior art.

The temperature control system according to the invention is simple, reliable and energy-efficient. In addition, it includes a built-in refrigerant buffer.

The invention is of course not limited to the embodiments described above but shown in the drawings, modified within the scope of the appended claims.

Claims (27)

10 15 20 25 30 518 336 PAYMENT REQUIREMENTS Temperature control device, in particular thermosyphon system, with controllable cooling capacity, which device comprises: (303) and one connected to each other by a riser (309): (305) (307) which are and one - an evaporator condenser downcomer - a refrigerant (321 ) (303), subcooled in the condenser which evaporates and absorbs heat in the riser in the condenser and (305) the evaporator the riser, and via the downcomer flows back to the evaporator; (311) the downcomer via a - a refrigerant container, which is connected to manifolds (313) for transporting the refrigerant in liquid form; and - a heater (315) thermally connected to the container, characterized in that (317,613)) which is in thermal communication with the container, (309,601); the device also comprises a contact body and a coolant (315) (311), the refrigerant (313) changing its cooling capacity; and - the heater is arranged to change the temperature ii depending on the required cooling capacity, (321) the container is transported through the manifold and changes the amount of liquid in the condenser (305) so (317) is arranged to generate a temperature difference between the container (311) and the coolant (309 ), the refrigerant transport between the container (311) contact body and the downcomer ceases when the subcooling of the refrigerant (321) contact body corresponds to the said temperature difference in (317). 10 15 20 25 518 336 Temperature control device according to Claim 1, characterized in that the coolant consists of condensed and subcooled refrigerant (321) in the downcomer (309). The temperature control device (611) for at least a part encloses the container according to claim 2, and the contact body (311). characterized in that the downcomer (613) Temperature control device according to one of Claims 1 to 3, characterized in that the container (311), (313), the heater (315) (317) is insulated from an external environment. according to the manifold and the contact body is thermal Temperature control device according to claim 1, (601), in particular of ambient air. characterized in that the coolant consists of an external cooling medium, according to any one of the patents (315) has an increasing effect in Temperature control device 1-5, arranged to heat the container, characterized in that the heater (311) in the event of a decreasing cooling demand and with a decreasing power effect in the event of an increasing cooling demand. Temperature control device according to claim 6, (315) (311), characterized in that the heater is arranged to always heat the container during operation at least with some effect. 10 15 20 25 518 336 - | u <. .- Temperature control device 1-7, according to one (315) temperature-dependent according to the claims, characterized in that the heater consists of a resistor connected in an electrical circuit, in particular a PCT resistor. something (315) Temperature control device according to patent 1-7, a thermostat. the claims characterized in that the heater comprises 10. l0. Temperature control device according to any one of patents 1-9, cooling electronic circuits, such as circuit boards (701). the claims characterized in that the device is intended to 11. ll. Temperature control device, in particular thermosiphon system, with controllable cooling capacity, which device comprises: (303) and one which are connected to each other by means of a riser (309); (305) (307) - an evaporator condenser and a downcomer - a refrigerant (321) (303), which evaporates and absorbs heat in rises in the condensed and (305) evaporator riser, subcooled in the condenser and flows back to the evaporator via the downcomer; for the refrigerant which is connected to (313) for - a container (311) the downcomer via a manifold transporting the refrigerant in liquid form; and - a heater (315) which is thermally connected to the container, characterized in that the device also comprises a contact body (317,63) thermally connected to the container, (309 ): which is in part a coolant which comprises the downcomer - the heater (315) to the container on the refrigerant is arranged to emit a predetermined power (311) (321) so that its temperature is always boiling point; and arranged that (311) refrigerant leakage of the refrigerant (321) is thereby transported from the downcomer (311) via being transported through the manifold - the contact body (317) is the temperature difference between the container (309), the subcooling of generating one and the downcomer thereby reducing and heating (309 ) to the container (317), so that the refrigerant (313) from the container. the contact body Temperature control device claim 11, characterized in that the refrigerant according to (321) until the subcooling of the refrigerant in the downcomer corresponds to that (317). the said temperature difference in the contact body is emitted from the container Temperature control device according to claim 11 or (611) for at least a part enclosing the container. 12, characterized in that the downcomer (615) and the contact body Temperature control device according to one of Claims 11, 12 or 13, characterized in that the container (311), the manifold (313), the heater (315) and the contact body (317) are thermally insulated from an external environment. Temperature control device according to one of 11 to 14, characterized in that the heater (315) consists of 10 15 20 25 518 336 a u u o | c oo a temperature-dependent resistor connected in an electrical circuit, in particular a PCT resistor. 16. Temperature control device ll-14, a thermostat. according to any one of the claims, characterized in that the heater (315) comprises Temperature control device according to any one of patent 11-16, cooling electronic circuits, such as circuit boards (701). the claims characterized in that the device is intended to A method of controlling the temperature in a temperature control device, in particular in a thermosyphon system, which device comprises: (305) (307) (303) and a condenser which are connected. with each other through a riser (309): - an evaporator and a downcomer - a container (311) which is connected to the downcomer via a manifold for the refrigerant, (313); - a heater (315) thermally connected to the container; and - a refrigerant (321), which process comprises the following process steps: (321) so that the steam rises in the riser; evaporating the refrigerant and absorbing heat in the evaporator (303) - condensing and subcooling the refrigerant in the condenser (305) downpipe; and so that the liquid flows back to the evaporator in 518 20 5 518 336 - transporting the refrigerant through the manifold (313) in liquid form, which method is characterized by: - changing the temperature in the container by means of the heater ((315) depending on the required cooling capacity; - exchange of heat energy with the container (311) via a contact body (317,613) which is in thermal communication with the container and a coolant (309.60l); - change of the amount of liquid in the condenser (305) at (321) ) (313) so that the cooling capacity of the condenser changes; the transport of the refrigerant through the manifold by a temperature difference between the container (309,601) - generation (311) and the coolant (317,613); and by means of the contact body - interruption of the refrigerant transport between the container (311) (309 ) when (321) said temperature difference in and the downcomer subcooling of the refrigerant corresponds to that contact body 317,613). characterized by selection of the downcomer (309) A process according to claim 18, the condensed refrigerant as a coolant. characterized in that (317) The method of claim 19, (311), (313) is thermally isolated from the environment. and the contact body container manifold 10 15 20 25 518 336 6 Process according to Claim 18, characterized by the selection of an external coolant, in particular ambient air (601), such as the coolant. Method according to one of Claims 18 to 21, characterized in that the container (311) has an effect in the event of a decreasing cooling demand and is heated with an increasing decreasing effect in the event of an increasing cooling need. Method according to one of the containers developed in one of Claims 18 to 22, temperature-dependent, characterized in that it is heated by a heat energy resistor, in particular in a PTC resistor. A method of controlling the temperature in a temperature control device, in particular in a thermosyphon system, the device comprising: (303) and one which are and one - an evaporator condenser (305) connected to each other by a riser (307) downpipe (309) ; (311) the downcomer via a manifold (313); - a container - a heater (315) thermally connected to the container; and - a refrigerant (321), which process comprises the following process steps: - evaporating the refrigerant (321) so that the steam rises in the riser; and absorbing heat in the evaporator (303) of the refrigerant, which is connected to condensing and subcooling the refrigerant in the condenser (305) of the downcomer; and so that the liquid flows back to the evaporator i - transporting the refrigerant through the manifold (313) in liquid form, which method is characterized by: (315) to the container so that its temperature is always at the boiling point of the refrigerant (321); - emitting a predetermined power from the heater (311) via one which is in thermal connection (311), partly a coolant which (309): of heat energy with the container (3l7,6l5) - exchange contact body with partly comprises the downcomer the container - generation of a temperature difference between the container (311) (309) (317); and the downcomer by means of the contact body - reducing the subcooling of the refrigerant (321) in the event of refrigerant leakage of the device; to the container - transport of heat from the downcomer (309) (311) via the contact body (317,6l5); and - transporting the refrigerant (321) through the manifold (313) from the container (311). Method according to claim 24, characterized in that the refrigerant (321) of the refrigerant in is discharged from the container until the subcooling (309) the temperature difference in the contact body. the downcomer corresponds to the said 518 356% = :: ;; ==. Method according to claim 24 or 25, characterized in that the container (311), the manifold (313) and the contact body (317) are thermally insulated from the environment. Method according to one of Claims 24 to 26, characterized in that the container (311) is heated by heat energy developed in a temperature-dependent resistor, in particular in a PTC resistor.