COOLING DEVICE

Abstract

A cooling device comprising a cooling circuit, is described. The cooling circuit further comprises a compressor adapted to compress cooling agent present in the cooling circuit during an active cooling mode, wherein the compressed cooling agent contains lubricant oil from the compressor; a condensing unit connected to the compressor by a first fluid line of the cooling circuit; and an evaporating unit, which is connected to the condensing unit by a second fluid line of the cooling circuit. The cooling circuit further comprises an expansion device arranged in the second fluid line; and an additional evaporator connected to the evaporating unit by a third fluid line of the cooling circuit, and connected to the compressor by a fourth fluid line of the cooling circuit.

Claims

1. A cooling device comprising a cooling circuit, the cooling circuit comprising: a compressor, which is adapted to compress cooling agent present in the cooling circuit in an active cooling mode, wherein the compressed cooling agent contains lubricant oil from the compressor; a condensing unit, which is connected to the compressor by a first fluid line of the cooling circuit; an evaporating unit, which is connected to the condensing unit by a second fluid line of the cooling circuit; an expansion device, which is arranged in the second fluid line; an additional evaporator, which is connected to the evaporating unit by a third fluid line of the cooling circuit, and which is connected to the compressor by a fourth fluid line of the cooling circuit, wherein the cooling device, in the active cooling mode, is configured to transfer lubricant oil from the compressor through the condensing unit, through the expansion device, through the evaporating unit, through the additional evaporator and through the fourth fluid line back to the compressor; a first fluid by-pass line, which connects the condensing unit with the evaporating unit; and a second fluid by-pass line, which connects the evaporating unit with the condensing unit, wherein the first fluid by-pass line comprises a first by-pass valve and wherein the second fluid by-pass line comprises a second by-pass valve, which are adapted to close the first fluid by-pass line and the second fluid by-pass line in the active cooling mode, respectively.

2. The cooling device according to claim 1, wherein in the active cooling mode the compressor is adapted to compress gaseous cooling agent, wherein the compressed gaseous cooling agent is adapted to be conducted together with the lubricant oil through the first fluid line to the condensing unit, wherein the condensing unit is adapted to condensate the compressed gaseous cooling agent and to obtain liquid cooling agent, wherein the obtained liquid cooling agent is adapted to be conducted together with the lubricant oil through the second fluid line and through the expansion device to the evaporating unit, wherein the evaporating unit is adapted to at least partially evaporate the liquid cooling agent and to obtain a mixture of gaseous and liquid cooling agent, wherein the obtained mixture of gaseous and liquid cooling agent is adapted to be conducted together with the lubricant oil through the third fluid line to the additional evaporator, wherein the additional evaporator is adapted to completely evaporate the liquid cooling agent and to obtain gaseous cooling agent, wherein the obtained gaseous cooling agent is adapted to be conducted through the fourth fluid line back to the compressor.

3. The cooling device according to claim 1, wherein in the active cooling mode the first by-pass valve and the second by-pass valve are adapted to completely close the first fluid by-pass line and the second fluid by-pass line, respectively, or wherein in the active cooling mode the first by-pass valve is adapted to completely close the first fluid by-pass line and the second by-pass valve is adapted to partially close the second fluid by-pass line by decreasing the cross-section of the second fluid by-pass line between 1% and 99%.

4. The cooling device according to claim 1, wherein in a passive cooling mode the compressor is adapted to be deactivated, wherein in the passive cooling mode the first by-pass valve and the second by-pass valve are adapted to open the first fluid by-pass line and the second fluid by-pass line, respectively, wherein in the passive cooling mode the cooling agent is adapted to directly flow from the condensing unit through the first fluid by-pass line, through the evaporating unit, and through the second fluid by-pass line back to the condensing unit.

5. The cooling device according to claim 1, wherein the cooling device comprises a control, wherein the third fluid line or the additional evaporator comprises a first sensor arrangement, which is adapted to detect a superheat of the cooling agent flowing through the third fluid line or through the additional evaporator, and wherein the control is adapted to operate the expansion device and/or the first by-pass valve in dependence of the detected superheat of the cooling agent.

6. The cooling device according to claim 1, wherein the cooling device comprises a control, wherein the third fluid line comprises a first sensor arrangement, which is adapted to detect a void fraction X of the cooling agent flowing through the third fluid line, and wherein the control is adapted to operate the expansion device and/or the first by-pass valve in dependence of the detected void fraction X of the cooling agent.

7. The cooling device according to claim 5, wherein the fourth fluid line comprises a second sensor arrangement, which is adapted to detect a superheat of the cooling agent flowing through the fourth fluid line, and wherein the control is adapted to operate the expansion device and/or the first by-pass valve in dependence of the detected superheat.

8. The cooling device according to claim 1, wherein the evaporating unit comprises a top part, a bottom part, and a plurality of evaporating tubes connecting the top part with the bottom part, wherein the bottom part is connected to the condensing unit by the second fluid line, and wherein the top part is connected to the third fluid line.

9. The cooling device according to claim 1, wherein the additional evaporator comprises an inlet, which is connected to the third fluid line, and wherein the additional evaporator comprises an outlet, which is connected to the fourth fluid line, wherein the inlet is connected to the outlet of the additional evaporator by at least one evaporating tube of the additional evaporator.

10. The cooling device according to claim 1, wherein the additional evaporator comprises a top part, a bottom part, and a plurality of evaporating tubes connecting the top part with the bottom part, wherein the top part or bottom part of the additional evaporator is connected to the evaporating unit by the third fluid line, and wherein the bottom part or top part of the additional evaporator is connected to the compressor by the fourth fluid line.

11. The cooling device according to claim 10, wherein the bottom part of the additional evaporator is connected to the evaporating unit by the third fluid line, wherein the top part of the additional evaporator is connected to the compressor by the fourth fluid line, the cooling circuit further comprising an oil release line, which connects the bottom part of the additional evaporator with the fourth fluid line, wherein the oil release line comprises a flow restricting element or oil release valve, which is adapted to close the oil release line and to retain lubricant oil in the bottom part of the additional evaporator, and to open the oil release line, wherein lubricant oil is adapted to flow from the bottom part of the additional evaporator through the oil release line into the fourth fluid line.

12. The cooling device according to claim 1, wherein the additional evaporator is formed as a regenerative heat exchanger, comprising a first flow-path, which connects a first condensing section of the second fluid line with a second condensing section of the second fluid line, and comprising a second flow-path, which connects the third fluid line with the fourth fluid line, wherein the regenerative heat exchanger is adapted to transfer heat from the cooling agent flowing through the first flow-path to the cooling agent flowing through the second flow-path.

13. The cooling device according to claim 1, the cooling circuit further comprising a third fluid by-pass line, which connects the evaporating unit with the additional evaporator, wherein the third fluid by-pass line comprises a flow-restricting element.

14. The cooling device according to claim 13, wherein the third fluid by-pass line connects the evaporating unit with a bottom part of the additional evaporator, with an outlet of the additional evaporator or with an outlet of the additional evaporator, which is formed as a regenerative heat exchanger.

15. The cooling device according to claim 13, wherein the third fluid by-pass line connects the evaporating unit with at least one of the plurality of evaporating tubes of the additional evaporator, with the at least one evaporating tube of the additional evaporator, or with the second flow path of the additional evaporator, which is formed as a regenerative heat exchanger.

16. The cooling device according to claim 1, wherein during the active cooling mode the second fluid by-pass line is adapted to transfer lubricant oil from condensing unit back to the compressor.

17. A method for cooling by using a cooling circuit of a cooling device, comprising: closing of a first fluid by-pass line of the cooling circuit by a first by-pass valve when the cooling device is in an active cooling mode, wherein the cooling circuit comprises a compressor, a condensing unit connected to the compressor by a first fluid line of the cooling circuit, an evaporating unit connected to the condensing unit by a second fluid line of the cooling circuit, an expansion device arranged in the second fluid line, an additional evaporator, connected to the evaporating unit by a third fluid line of the cooling circuit, and connected to the compressor by a fourth fluid line of the cooling circuit, the first fluid by-pass line, which connects connecting the condensing unit with the evaporating unit and a second fluid by-pass line, connecting the evaporating unit with the condensing unit, wherein the first fluid by-pass line comprises the first by-pass valve, and wherein the second fluid by-pass line comprises a second by-pass valve, closing of the second fluid by-pass line in the active cooling mode by the second by-pass valve, compressing cooling agent present in the cooling circuit in the active cooling mode by the compressor, wherein the compressed cooling agent contains lubricant oil from the compressor, and transferring at least a portion of the lubricant oil from the compressor through the condensing unit, through the expansion device, through the evaporating unit, through the additional evaporator and through the fourth fluid line back to the compressor in the active cooling mode.

18. The method of claim 17, the method further comprising: opening the first fluid by-pass line in a passive cooling mode by the first by-pass valve, and opening the second fluid by-pass line in the passive cooling mode by the second by-pass valve, wherein the cooling agent directly flows from the condensing unit through the first fluid by-pass line to the evaporating unit, and through the second fluid by-pass line back to the condensing unit.

19. The method of claim 17, further comprising: partially opening the second fluid by-pass line in the active cooling mode by the second by-pass valve, wherein at least a portion of the lubricant oil is transferred from the condensing unit back to the compressor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0125] In the following, examples of the disclosure are described in more detail with reference to the attached figures and drawings, in which:

[0126] FIG. 1 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example;

[0127] FIG. 2 is a schematic diagram of a cooling device comprising a cooling circuit during a passive cooling mode according to an example;

[0128] FIGS. 3A and 3B are schematic diagrams of an evaporating unit and an additional evaporator of a cooling circuit according to an example;

[0129] FIG. 4 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example;

[0130] FIG. 5 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example;

[0131] FIG. 6 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example;

[0132] FIG. 7 is a schematic diagram of a cooling device comprising a cooling circuit during a passive cooling mode according to an example;

[0133] FIG. 8 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example;

[0134] FIG. 9 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example;

[0135] FIG. 10 is a schematic diagram of a cooling device comprising a cooling circuit during a passive cooling mode according to an example;

[0136] FIG. 11 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example;

[0137] FIG. 12 is a schematic diagram of a cooling device comprising a cooling circuit during a passive cooling mode according to an example; and

[0138] FIG. 13 is a flow diagram illustrating a method for cooling according to an example.

[0139] In the following, identical reference signs refer to identical or at least functionally equivalent features.

DETAILED DESCRIPTION OF THE EXAMPLES

[0140] In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of examples of the disclosure or specific aspects in which examples of the disclosure may be used. It is understood that examples of the disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the disclosure is defined by the appended claims.

[0141] For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method operations are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method operations (e.g. one unit performing the one or plurality of operations, or a plurality of units each performing one or more of the plurality of operations), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one operation to perform the functionality of the one or plurality of units (e.g. one operation performing the functionality of the one or plurality of units, or a plurality of operations each performing the functionality of one or more of the plurality of units), even if such one or plurality of operations are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various examples and/or aspects described herein may be combined with each other, unless specifically noted otherwise.

[0142] FIG. 1 is a schematic diagram of a cooling device 100 comprising a cooling circuit 101 during an active cooling mode according to an example.

[0143] The cooling device 100, which is only schematically shown in FIG. 1, is not limited to any specific cooling application, but is adapted to cool any media, for example ambient air, liquid from an additional cooling circuit of another cooling device, a solid element, which generates heat, or any other solid or liquid material. Therefore, heating, ventilation, and air conditioning devices (HVAC) are comprised by a cooling device 100 according to the example.

[0144] Only as an example, the cooling device 100 according to the example is adapted to cool a cabinet, for example a server cabinet, which for example directly cools servers within the exemplary server cabinet or which for example cools the air within the exemplary server cabinet, thereby indirectly cooling the servers.

[0145] As illustrated in FIG. 1, the cooling circuit 101 of the cooling device 100 comprises inter alia a compressor 105, a condensing unit 111, an expansion device 115, an evaporating unit 103 and an additional evaporator 135, which are fluidically connected within the cooling circuit 101. A cooling agent, for example tetrafluorethane, is flowing through the cooling circuit 101. The cooling agent is characterized in that it can be present in the cooling circuit 101 in two phases, e.g. in a liquid and in a gaseous phase. At lower temperatures and/or higher pressure the cooling agent is typically present in the liquid phase, while at higher temperatures and/or lower pressure, the cooling agent is typically present in the gaseous phase.

[0146] In the following the cooling circuit 101 of the cooling device 100 is described, wherein in particular reference to an active cooling mode is provided.

[0147] The compressor 105 forms a first section 101-a of the cooling circuit 101. The compressor 105 is positioned in the cooling circuit 101 downstream of the additional evaporator 135. The compressor is adapted to compress the gaseous cooling agent during the active cooling mode, in order to obtain compressed gaseous cooling agent. During compression, the compressor 105, which is driven by electrical and/or mechanical energy, pressurizes the gaseous cooling agent thereby allowing for an increase of temperature of the cooling agent and for an active flow of the compressed gaseous cooling agent further downstream through the cooling circuit 101.

[0148] In this respect, it is mentioned that the compressor 105 is formed as an oil-lubricated compressor 105, which is characterized in that its moving parts are lubricated by lubricant oil to reduce friction. However, during compression, at least a part of the lubricant oil, which is present in the compressor 105, can be transported together with the compressed gaseous cooling agent further downstream in the cooling circuit 101.

[0149] At a first connection point 109-1, the compressor 105, which forms a first section 101-a of the cooling circuit 101, is connected to a fourth fluid line 119 of the cooling circuit 101. At a second connection point 109-2, the compressor 105 is connected to a first fluid line 107 of the cooling circuit 101, wherein the first fluid line 107 forms a second section 101-b of the cooling circuit 101. The first fluid line 107 is adapted to transfer the compressed gaseous cooling agent from the compressor 105 to the condensing unit 111, wherein the condensing unit 111 forms a third section 101-c of the cooling circuit 101. The first fluid line 107 is connected to the condensing unit 111 at a third connection point 109-3.

[0150] The condensing unit 111, which is positioned in the cooling circuit 101 downstream of the compressor 105, is adapted to condensate the compressed cooling agent by dissipating heat from the cooling agent, in order to obtain liquid cooling agent.

[0151] The heat dissipating from the condensing unit 111 typically is adapted to be transferred to a flow of ambient air, which temperature is lower than the temperature of the cooling agent entering the condensing unit 111, to allow for a heat transfer from the cooling agent flowing through the condensing unit 111 to the ambient air. To enable an efficient heat dissipation, the condensing unit 111 in particular comprises extended surface areas, which for example can comprise at least one condensing tube, a top part of the condensing unit 111, a bottom part of the condensing unit 111, and/or condensing fins.

[0152] At a fourth connection point 109-4, the condensing unit 111 is connected to a first section 113-1 of a second fluid line 113 of the cooling circuit 101, wherein the first section 113-1 of the second fluid line 113 forms a fourth section 101-d of the cooling circuit 101. The first section 113-1 of the second fluid line 113 is adapted to transfer the liquid cooling agent from the condensing unit 111 to the expansion device 115, which forms a fifth section 101-e of the cooling circuit 101.

[0153] The expansion device 115 is positioned in the cooling circuit 101 downstream of the condensing unit 111 and upstream of the evaporating unit 103. The expansion device 115 is adapted to expand the liquid cooling agent, in order to obtain expanded liquid cooling agent, wherein the expanded liquid cooling agent can comprise a two-phase mixture of gaseous and liquid cooling agent. The expansion device 115 can be a thermal expansion valve, an electronic expansion valve, a capillary tube, an ejector, a turbine, a ball valve, an orifice and/or a porous plug.

[0154] A second section 113-2 of the second fluid line 113 of the cooling circuit 101, which forms a sixth section 101-f of the cooling circuit 101, connects the expansion device 115 with the evaporating unit 103, e.g., at a fifth connection point 109-5. The evaporating unit 103 forms a seventh section 101-g of the cooling circuit 101 and is adapted to at least partially evaporate the expanded liquid cooling agent in the active cooling mode by supplying heat to the cooling agent, thereby obtaining a two-phase mixture of liquid and gaseous cooling agent.

[0155] At a sixth connection point 109-6, the evaporating unit 103 is connected to the third fluid line 117 of the cooling circuit 101, wherein the third fluid line 117 forms an eighth section 101-h of the cooling circuit 101. The third fluid line 117 is adapted to transfer the at least partially evaporated cooling agent from the evaporating unit 103 to the additional evaporator 135, e.g., to an inlet 135-1 of the additional evaporator 135, wherein the additional evaporator 135 forms a ninth section 101-i of the cooling circuit 101.

[0156] At an eight connection point 109-8, an outlet 135-2 of the additional evaporator 135 is connected to the fourth fluid line 119, which forms a tenth section 101-j of the cooling circuit 101 thereby closing the cooling circuit 101.

[0157] The additional evaporator 135 is adapted to completely evaporate the at least partially evaporated cooling agent flowing from the evaporating unit 103 into the additional evaporator 135 by supplying heat to the cooling agent, in order to obtain a gaseous cooling agent.

[0158] As can be derived from FIG. 1, the additional evaporator 135 comprises the inlet 135-1, which is connected to the outlet 135-2 by a single evaporating tube 135-3, which is formed as a meander-shaped single evaporating tube 135-3.

[0159] The heat supply to the evaporating unit 103 and/or additional evaporator 135 typically is provided by a flow of ambient air, which temperature is higher than the temperature of the cooling agent flowing through the evaporating unit 103 and/or additional evaporator 135, to allow for a heat transfer from the ambient air to the cooling agent flowing through the evaporating unit 103 and/or additional evaporator 135. To enable an efficient heat transfer, the evaporating unit 103 and/or the additional evaporator 135 comprises extended surface areas, which can comprise optional evaporating fins.

[0160] At a ninth connection point 109-9, the condensing unit 111 is connected to a first fluid by-pass line 121 of the cooling circuit 101, which forms eleventh section 101-k of the cooling circuit 101, wherein the first fluid by-pass line 121 comprises a first by-pass valve 125, which is adapted to close the first fluid by-pass line 121 in the active cooling mode. The first fluid by-pass line 121 is connected to the bottom part 103-2 of the evaporator 103 at a tenth connection point 109-10, wherein the first fluid by-pass line 121 will be explained in more detail further below.

[0161] At an eleventh connection point 109-11, the evaporating unit 103 is connected to a second fluid by-pass line 127 of the cooling circuit 101, which forms a twelfth section 101-I of the cooling circuit 101, wherein the second fluid by-pass line 127 comprises a second by-pass valve 129, which is adapted to close the second fluid by-pass line 127 in the active cooling mode. The second fluid by-pass line 127 joins the condensing unit 111 at a twelfth connection point 109-12. The second fluid by-pass line 127 will be explained in more detail further below.

[0162] The above described active cooling mode of the cooling is typically required when the temperature of ambient air, which corresponds to air contacting the condensing unit, is above or close to the temperature of air inside the cabinet, which corresponds to air flowing from the evaporator to the cabinet. The active cooling mode requires the active work of the compressor 105 and thereby consumes electrical energy.

[0163] During the active cooling mode, the compressor 105 of the cooling circuit 101 is activated, the first by-pass valve 125 is adapted to close the fluid by-pass line 121, and the second by-pass valve 129 is adapted to at least partially close the second fluid by-pass line 127.

[0164] Therefore, during the active cooling mode the cooling agent is adapted to be transferred from the compressor 105, through the first fluid line 107, through the condensing unit 111, through the first section 113-1 of the second fluid line 113, through the expansion device 115, through the second section 113-3 of the second fluid line 113, through the evaporating unit 103, through the third fluid line 117, through the inlet 135-1 of the additional evaporator 135, through the evaporating tube 135-3 of the additional evaporator 135, through the outlet 135-2 of the additional evaporator 135, and through the fourth fluid line 119 back to the compressor 105.

[0165] The circulation between vapor and liquid phases of the cooling agent within the cooling circuit 101 during the active cooling mode is enabled by active work from the compressor 105, in combination with the expansion of liquid cooling agent at the expansion device 115.

[0166] The corresponding direction of flow of the cooling agent 131 in the active cooling is marked with solid arrows in FIG. 1. The direction of flow of the cooling agent in the passive cooling is marked with dashed arrows in FIG. 1.

[0167] As mentioned above, due to employing an oil-lubricated compressor 105, oil particles can be transferred together with the compressed gaseous cooling agent from the compressor 105 to other components of the cooling circuit 101, which are located downstream of the compressor 105, for example to the condensing unit 111, to the expansion device 115, to the evaporating unit 103 and/or to the additional evaporator 135.

[0168] Deposits of lubricant oil within for example the evaporating unit 103, the additional evaporator 135 and/or condensing unit 111 might impair the efficiency of heat transfer with the ambient air, and deposits of lubricant oil within for example the expansion device 115 might restrict the flow of cooling agent through the expansion device 115. Moreover, the presence of dissolved lubricant oil in the liquid phase of the cooling agent, leads to an increase in the viscosity of the cooling agent and to a significant increase of the flow resistance. At such condition, the force of gravity is not enough for an efficient circulation and the thermal performance of the cooling device 100 during the passive cooling mode is poor.

[0169] The example of the present invention allows for an efficient prevention of deposits of lubricant oil within the condensing unit 111, the expansion device 115, the evaporating unit 103 and/or the additional evaporator 135 as summarized in the following.

[0170] The compressed gaseous cooling agent together with liquid lubricant oil forms a two-phase mixture, which is adapted to flow from the compressor 105 through the first fluid line 107 into the condensing unit 111. At the condensing unit 111 during condensation the gaseous cooling agent is transformed into liquid cooling agent, wherein the liquid lubricant oil is adapted to be dissolved in the obtained liquid cooling agent, thereby forming a one-phase mixture.

[0171] The one-phase mixture comprising liquid cooling agent and the liquid lubricant oil dissolved therein is adapted to be conducted through the second fluid line 113 and is expanded in the expansion device 115 before the one-phase mixture is adapted to enter the evaporating unit 103.

[0172] When the one-phase mixture subsequently is adapted to flow through the evaporating unit 103, the liquid cooling agent is partially evaporated, thereby forming a two-phase mixture of liquid cooling agent and gaseous cooling agent, wherein the liquid lubricant oil is dissolved in the liquid cooling agent.

[0173] The two-phase mixture of liquid cooling agent and gaseous cooling agent, wherein the liquid lubricant oil is dissolved in the liquid cooling agent, flows from the evaporating unit 103 through the third fluid line 117 into the additional evaporator 135, wherein the two-phase mixture is completely evaporated in the evaporating tube 135-3 of the additional evaporator 135 resulting in the presence of exclusively gaseous cooling agent and phase-separated liquid lubricant oil, which is formed in the evaporating tube 135-3 as lubricant oil particles.

[0174] Since the direction of flow of the two-phase mixture of gaseous cooling agent and liquid lubricant oil within the evaporating tube 135-3 is aligned to the force of gravity acting on the liquid lubricant oil particles and with the pressure exerted on the liquid oil particles by the gaseous cooling agent, the movement of the liquid oil particles from the evaporating tube 135-3 to the outlet 135-2 of the additional evaporator 133 is efficiently supported, thereby preventing any deposits of lubricant oil within the evaporating tube 135-3, e.g., by pushing the lubricant oil particles into the fourth fluid line 119 and further to the compressor 105, which is achieved by a small diameter of the evaporating tube 135-3.

[0175] Therefore, due to the design of the additional evaporator 135 any lubricant oil exiting the compressor 105 together with the cooling agent during the active cooling mode is recycled back to the compressor 105. Therefore, a stable return of lubricant oil from the additional evaporator 135 to the compressor 105 is ensured.

[0176] In case, the temperature of ambient air, which corresponds to air contacting the condensing unit, is below the temperature of air inside the cabinet, which corresponds to air flowing from the evaporator to the cabinet, a passive cooling mode can be applied. In the passive cooling mode, the compressor 105 is adapted to be deactivated for energy saving, and the circulation of the cooling agent through the cooling circuit 101 is provided by the principle of a loop thermosiphon. The function of the passive cooling mode is described in respect to the example of FIG. 2.

[0177] FIG. 2 is a schematic diagram of a cooling device 100 comprising a cooling circuit 101 during a passive cooling mode according to an example.

[0178] The cooling circuit 101 depicted in FIG. 2 is identical to the cooling circuit 101 depicted in FIG. 1 except for the passive cooling mode applied.

[0179] During the passive cooling the first by-pass valve 125 is adapted to open the first fluid by-pass line 121, so that during the passive cooling mode the liquid cooling agent is adapted to flow from the condensing unit 111 through the first fluid by-pass line 121 into the evaporating unit 103, in which the liquid cooling agent is evaporated thereby obtaining gaseous cooling agent.

[0180] During the passive cooling mode, the compressor 105 of the cooling circuit 101 is adapted to be deactivated and the second by-pass valve 129 is adapted to open the second fluid by-pass line 127, so that during the passive cooling mode the gaseous cooling agent, which has been evaporated in the evaporating unit 103, is adapted to flow from evaporating unit 103 through the second fluid by-pass line 127 to the condensing unit 111. In the condensing unit 111 the gaseous cooling agent is liquefied, in order to obtain liquid cooling agent again, thereby closing the passive cooling cycle.

[0181] The corresponding direction of flow of the cooling agent 133 in the passive cooling mode is marked with solid arrows in FIG. 2. The direction of flow of the cooling agent in the active cooling is marked with dashed arrows in FIG. 2.

[0182] The circulation between vapor and liquid phases of the cooling agent between the condensing unit 111 and the evaporating unit 103 during the passive cooling mode is enabled by the natural flow of the cooling agent due to gravitational forces.

[0183] Further, during the passive cooling mode, oil migration of lubricant oil through the cooling circuit 101 is not significant, because the compressor 105 is adapted to be deactivated and the main volume of lubricant oil is maintained at the compressor 105.

[0184] FIGS. 3A and 3B are schematic diagrams of an evaporating unit and an additional evaporator of a cooling circuit according to an example.

[0185] In an embodiment, the evaporating unit 103 shown in FIG. 3A corresponds to the evaporating unit 103 shown in FIGS. 1 and 2. In an embodiment, the additional evaporator 135 shown in FIG. 3B corresponds to the additional evaporator 135 shown in FIGS. 1 and 2.

[0186] The evaporating unit 103 shown in FIG. 3A is formed as an evaporator, which comprises a top part 103-1 with an outlet 141, a bottom part 103-2 with an inlet 139, and a plurality of evaporating tubes 103-3 connecting the top part 103-1 with the bottom part 103-2. Further, the evaporating unit 103 shown in FIG. 3A comprises a plurality of optional evaporating fins 137, which increase the surface area of the evaporating unit 103, thereby increasing the efficiency of heat uptake of the evaporating unit 103.

[0187] Liquid cooling agent from the condensing unit 111 is adapted to enter the bottom part 103-2 of the evaporating unit through the inlet 139, and is adapted to flow from the bottom part 103-2 through the plurality of evaporating tubes 103-3 into the top part 103-1, and is adapted to exit the top part 103-1 through the outlet 141.

[0188] In the passive cooling mode, the flow of liquid cooling agent through the plurality of evaporating tubes 103-3 of the evaporating unit 103 is regulated in that way that the liquid cooling agent is completely evaporated.

[0189] In the active cooling mode, the flow of liquid cooling agent through the plurality of evaporating tubes 103-3 of the evaporating unit 103 is regulated in that way that the liquid cooling agent is at least partially evaporated, which means that the resulting partially evaporated cooling agent is present as a two-phase mixture comprising liquid cooling agent and gaseous cooling agent. The two-phase mixture comprising liquid cooling agent and gaseous cooling agent is then adapted to be conducted to the additional evaporator 135 shown in FIG. 3B where the complete evaporation of the mixture subsequently is performed in order to obtain only gaseous cooling agent.

[0190] The additional evaporator shown in FIG. 3B comprises an inlet 135-1, an outlet 135-2, and a single evaporating tube 135-3 connecting the inlet 135-1 with the outlet 135-2, wherein the single evaporating tube 135-3 comprises a meander shape. Further, the additional evaporator 135 comprises a plurality of optional evaporating fins 137.

[0191] FIG. 4 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example.

[0192] The cooling circuit 101 shown in the example according to FIG. 4 is identical to the cooling circuit 101 shown in the example according to FIG. 1 and FIG. 2, except for a control 145, which is connected to a first sensor arrangement 143-1 and to a second sensor arrangement 143-2.

[0193] The first sensor arrangement 143-1 is positioned in the third fluid line 117 connecting the evaporating unit 103 and the additional evaporator 135 and is adapted to detect a superheat of the cooling agent flowing through the third fluid line 117.

[0194] The second sensor arrangement 143-2 is positioned in the fourth fluid line 119 connecting the additional evaporator 135 with the compressor 105 and is adapted to detect a superheat of the cooling agent flowing through the fourth fluid line 119.

[0195] The control 145 is adapted to operate the first by-pass valve 125 in dependence of the superheat of the cooling agent flowing through the third fluid line 117 detected by the first sensor arrangement 143-1 and/or in dependence of the superheat of the cooling agent flowing through the fourth fluid line 119 detected by the second sensor arrangement 143-2.

[0196] While not shown in FIG. 4, the control 145 is optionally adapted to operate the expansion device 115 in dependence of the superheat of the cooling agent flowing through the third fluid line 117 detected by the first sensor arrangement 143-1 and/or in dependence of the superheat of the cooling agent flowing through the fourth fluid line 119 detected by the second sensor arrangement 143-2.

[0197] In an embodiment, the first and/or second sensor arrangement 143-1, 143-2 comprises a pressure sensor, which is adapted to detect a pressure of the cooling agent flowing through the third fluid line 117 and/or the fourth fluid line 119.

[0198] In an embodiment, the first and/or second sensor arrangement 143-1, 143-2 comprises a temperature sensor, which is adapted to detect a temperature of the cooling agent flowing through the third fluid line 117 and/or the fourth fluid line 119.

[0199] In an embodiment, the first and/or second sensor arrangement 143-1, 143-2 comprises both a pressure sensor and a temperature sensor.

[0200] In an embodiment, the control 145 is adapted to switch the expansion device 115 and/or the first by-pass valve 125 in an at least partially closed state to increase the flow rate of cooling agent, if the superheat is detected, wherein the superheat is defined by ΔT1=T1−TS1. T1 is the temperature of the cooling agent in the third fluid line 117 and/or the additional evaporator 135 as measured by the temperature sensor of the first second sensor arrangement 143-1. TS1 is the evaporation temperature of the cooling agent inside the third fluid line 117 and/or the additional evaporator 135, wherein the control is adapted to determine TS1 based on the pressure of the cooling agent in the third fluid line 117 and/or the additional evaporator 135, wherein the pressure is measured by the pressure sensor of the first sensor arrangement 143-1.

[0201] In other words, the control 145 is adapted to switch the expansion device 115 and/or the first by-pass valve 125 in an at least partially closed state to increase the flow rate of cooling agent, if the detected superheat is above 0, in case that ΔT1>0. If ΔT1=0 or ΔT1<0, the flow rate is not changed.

[0202] In particular, the control 145 is adapted to switch the expansion device 115 and/or first by-pass valve 125 in at least partially closed state to reduce the flow rate of cooling agent, if the detected superheat is below an additional superheat threshold, wherein the additional superheat threshold is defined by □T2=T2−TS2. TS2 is the saturation temperature of the cooling agent in the fourth fluid line 119, which is determined based on the pressure of the cooling agent in the fourth fluid line, wherein the pressure is measured by the pressure sensor of the second sensor arrangement 143-2. T2 is the temperature of the cooling agent flowing through the fourth fluid line 119, which is measured by the temperature sensor of the second sensor arrangement 143-2.

[0203] In particular, the control 145 is adapted to switch the expansion device 115 and/or first by-pass valve 125 in at least partially opened state to increase the flow rate of cooling agent, if the detected superheat is above an additional superheat threshold, wherein the additional superheat threshold is defined by □T2=T2−TS2. TS2 and T2 are defined as summarized above.

[0204] Due to the specific operation of the expansion device 115 and/or first by-pass valve 125 by the control 145, the flow rate of the cooling agent could be regulated in that way, that the temperature of the cooling agent on the outlet of the additional evaporator 135, i.e. the inlet of the compressor 105 is as close as possible to the superheat threshold, thereby allowing for a particularly effective evaporation process.

[0205] FIG. 5 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example.

[0206] The cooling circuit 101 shown in the example according to FIG. 5 is identical to the cooling circuit 101 shown in the example according to FIG. 4, except for the difference that the first sensor arrangement 143-1 is positioned in the additional evaporator 135 instead of the third fluid line 117 as an alternative.

[0207] Reference to the details according to the example according to FIG. 4 is provided.

[0208] FIG. 6 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example.

[0209] The cooling circuit 101 shown in the example according to FIG. 6 is related to the cooling circuit 101 shown in the example according to FIG. 1, except for the difference that the additional evaporator 145 comprises a top part 147-1, a bottom part 147-2 and a plurality of evaporating tubes 147-3 connecting the top part 147-1 with the bottom part 147-2, wherein the plurality of evaporating tubes 147-3 are vertically oriented.

[0210] Consequently during the active cooling mode, the partially evaporated cooling agent is adapted to enter the top part 147-1 of the additional evaporator 147 and subsequently flows down the plurality of evaporating tubes 147-3 before entering the bottom part 147-2 and subsequently entering the fourth fluid line 119. After complete evaporation of the cooling agent in the plurality of evaporating tubes 147-3 gaseous cooling agent and liquid lubricant oil is obtained, wherein the flow of the liquid lubricant oil down the plurality of evaporating tubes 147-3 is supported by the force of gravity thereby allowing for an effective removal of lubricant oil from the additional evaporator 147.

[0211] FIG. 7 is a schematic diagram of a cooling device comprising a cooling circuit during a passive cooling mode according to an example.

[0212] The cooling circuit 101 shown in the example according to FIG. 7 is identical to the cooling circuit 101 shown in the example according to FIG. 6, except for that in the example according to FIG. 7 the passive cooling mode is shown.

[0213] FIG. 8 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example.

[0214] The cooling circuit 101 shown in the example according to FIG. 8 is related to the cooling circuit 101 shown in the example according to FIG. 1, except for that in the example according to FIG. 8 in addition to the third fluid line 117, an additional third fluid by-pass line 149 is present, which connects the evaporating unit 103 with the additional evaporator 135, wherein the third fluid by-pass line 149 comprises a flow-restricting element 151.

[0215] In an embodiment, the third fluid by-pass line 149, which forms a thirteenth section 101-m of the cooling circuit 101, is connected to the evaporating unit 103 at a thirteenth connection point 109-3, and is connected to the outlet 135-2 of the additional evaporator 103 at the eighth connection point 109-8. However, even if not shown in FIG. 8, the third fluid by-pass line 149 can be alternatively connected to the evaporating tube 135-3 of the additional evaporator 135.

[0216] The third fluid by-pass line 149 with the flow restrictor 151 allows for an additional path between the evaporating unit 103 and the additional evaporator 135 to transfer lubricant oil away from the evaporating unit 103, e.g., when the third fluid by-pass line 149 is connected to a bottom part 103-2 of the evaporating unit 103.

[0217] FIG. 9 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example.

[0218] The cooling circuit 101 shown in the example according to FIG. 9 is related to the cooling circuit 101 shown in the example according to FIG. 1, except for that in the example according to FIG. 9 the additional evaporator 159 is formed as a regenerative heat exchanger.

[0219] As can be derived from FIG. 9, the additional evaporator 159, which is formed as a regenerative heat exchanger, comprises a first flow path 159-1, which connects a first condensing section 113-3 of the second fluid line 113 with a second condensing section 113-4 of the second fluid line 113. The second condensing section 113-4 of the second fluid line 113 is connected to the expansion device 115, wherein the expansion device 115 is connected to the evaporating unit 103 by the second section 113-2 of the second fluid line 103.

[0220] As can be derived from FIG. 9, the additional evaporator 159, which is formed as a regenerative heat exchanger, comprises a second flow-path 159-2, which connects the third fluid line 117 with the fourth fluid line 119.

[0221] The regenerative heat exchanger is adapted to transfer heat from the cooling agent flowing through the first flow-path 159-1 to the cooling agent flowing through the second flow-path 159-2.

[0222] Warm liquid cooling agent, which is adapted to flow from the condensing unit 111 through the first flow path 159-1, is adapted to transfer heat to the at least partially evaporated cooling agent, which is adapted to flow from the evaporating unit 103 through the second flow path 159-2, thereby decreasing the amount of heat, which is required at the additional evaporator 159 to completely evaporate the at least partially evaporated cooling agent. Therefore, the size of the additional evaporator 159, which is formed as a regenerative heat exchanger, can be significantly reduced.

[0223] FIG. 10 is a schematic diagram of a cooling device comprising a cooling circuit during a passive cooling mode according to an example.

[0224] The cooling circuit 101 shown in the example according to FIG. 10 is identical to the cooling circuit 101 shown in the example according to FIG. 9, except for that in the example according to FIG. 10 the passive cooling mode is shown.

[0225] FIG. 11 is a schematic diagram of a cooling device comprising a cooling circuit during an active cooling mode according to an example.

[0226] The cooling circuit 101 shown in the example according to FIG. 11 is related to the cooling circuit 101 shown in the example according to FIG. 6, except for that in the example according to FIG. 11 an oil release line 155 is present, which connects the additional evaporator 147 with the fourth fluid line 119.

[0227] As can be derived from FIG. 11, the bottom part 147-2 of the additional evaporator 147 is connected to the evaporating unit 135 by the third fluid line 117, wherein the top part 147-1 of the additional evaporator 147 is connected to the compressor 105 by the fourth fluid line 119 similar to the example according to FIG. 6.

[0228] However, as shown in the example according to FIG. 11, the oil release line 155 additionally connects the bottom part 147-2 of the additional evaporator 147 with the fourth fluid line 119. The oil release line 155 comprises a flow restricting element or oil release valve 157, which is adapted to close the oil release line 155 in order to retain lubricant oil in the bottom part 147-2 of the additional evaporator 147, and to open the oil release line 155, so that lubricant oil is adapted to flow from the bottom part 147-2 of the additional evaporator 147 through the oil release line 155 into the fourth fluid line 119.

[0229] By the oil release line 155 comprising a flow restricting element or oil release valve 157 any liquid lubricant oil, which maintains in the bottom part 147-2 of the additional evaporator 147 after the complete evaporation of cooling agent within the plurality of evaporating tubes 147-3, can be directly transferred into the fourth fluid line 119 and further to the compressor 105.

[0230] FIG. 12 is a schematic diagram of a cooling device comprising a cooling circuit during a passive cooling mode according to an example.

[0231] The cooling circuit 101 shown in the example according to FIG. 12 is identical to the cooling circuit 101 shown in the example according to FIG. 11, except for that in the example according to FIG. 10 the passive cooling mode is shown.

[0232] FIG. 13 is a flow diagram illustrating a method 200 for cooling according to an example.

[0233] The method 200 comprises the operations of:

[0234] Closing 201 of the first fluid by-pass line 121 in an active cooling mode by the first by-pass valve 125.

[0235] Closing 203 of the second fluid by-pass line 127 in the active cooling mode by the second by-pass valve 129.

[0236] Compressing 205 cooling agent present in the cooling circuit 101 during the active cooling mode by the compressor 105, wherein the compressed cooling agent contains lubricant oil from the compressor 105.

[0237] Transferring 207 lubricant oil from the compressor 105 through the condensing unit 111, through the expansion device 115, through the evaporating unit 103, through the additional evaporator 135, 147, 159 and through the fourth fluid line 119 back to the compressor 105 in the active cooling mode.

[0238] In an embodiment, the method comprises the optional method operations of opening 209 of the first fluid by-pass line 121 in a passive cooling mode by the first by-pass valve 125, and opening 211 of the second fluid by-pass line 127 in the passive cooling mode by the second by-pass valve 129, so that the cooling agent directly flows from the condensing unit 111 through the first fluid by-pass line 121 to the evaporating unit 103, and through the second fluid by-pass line 127 back to the condensing unit 111.

[0239] In an embodiment, the method comprises the optional method operation of partially opening 213 of the second fluid by-pass line 127 in the active cooling mode by the second by-pass valve 129, so that lubricant oil is transferred from the condensing unit 111 back to the compressor 105.

[0240] Further features of the method 200 result directly from the structure and/or functionality of the cooling device 100, respectively cooling circuit 101 as well as its different examples described above.

[0241] The person skilled in the art will understand that the “blocks” (“units”) of the various figures (method and apparatus) represent or describe functionalities of examples of the present disclosure (rather than necessarily individual “units” in hardware or software) and thus describe equally functions or features of apparatus examples as well as method examples (unit=operation).

[0242] In the several examples provided in the present invention, it should be understood that the disclosed apparatus, and method may be implemented in other manners. For example, the described examples of an apparatus are merely exemplary.