Patent Application
20080229780
This invention relates generally to the field of cooling systems and, more particularly, to a system and method for separating components of a fluid coolant for cooling a structure.
A variety of different types of structures can generate heat or thermal energy in operation. To prevent such structures from over heating, a variety of different types of cooling systems may be utilized to dissipate the thermal energy. Certain cooling systems utilize water as a coolant. To prevent the water from freezing, the water may be mixed with antifreeze.
According to one embodiment of the invention, a cooling system for a heat-generating structure includes a heating device, a cooling loop, and a separation structure. The heating device heats a flow of fluid coolant including a mixture of water and antifreeze. The cooling loop includes a director structure which directs the flow of the fluid coolant substantially in the form of a liquid to the heating device. The heating device vaporizes a substantial portion of the water into vapor while leaving a substantial portion of the antifreeze as liquid. The separation structure receives, from the heating device, the flow of fluid coolant with the substantial portion of the water as vapor and the substantial portion of the antifreeze as liquid. The separation structure separates one of the substantial portion of the water as vapor or the substantial portion of the antifreeze as liquid from the cooling loop while allowing the other of the substantial portion of the water as vapor or the substantial portion of the antifreeze as liquid to remain in the cooling loop.
Certain embodiments of the invention may provide numerous technical advantages. For example, a technical advantage of one embodiment may include the capability to separate a fluid coolant including a mixture of antifreeze and water into a fluid coolant including substantially only water and a fluid coolant including substantially only antifreeze. Other technical advantages of other embodiments may include using only the fluid coolant including substantially only water to cool a heat-generating structure. Still yet other technical advantages of other embodiments may include the capability to remix the fluid coolant including substantially only water with the fluid coolant including substantially only antifreeze.
Although specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the following figures and description.
For a more complete understanding of example embodiments of the present invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
It should be understood at the outset that although example embodiments of the present invention are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or in existence. The present invention should in no way be limited to the example embodiments, drawings, and techniques illustrated below, including the embodiments and implementation illustrated and described herein. Additionally, the drawings are not necessarily drawn to scale.
Conventionally, cooling systems may be used to cool server based data centers or other commercial and military applications. Although these cooling systems may minimize a need for conditioned air, they may be limited by their use of either a fluid coolant including only water or a fluid coolant including a mixture of antifreeze and water.
The cooling system 10 of
The structure 12 may be arranged and designed to conduct heat or thermal energy to the heat exchangers 23, 24. To receive this thermal energy or heat, the heat exchanger 23, 24 may be disposed on an edge of the structure 12 (e.g., as a thermosyphon, heat pipe, or other device) or may extend through portions of the structure 12, for example, through a thermal plane of structure 12. In particular embodiments, the heat exchangers 23, 24 may extend up to the components of the structure 12, directly receiving thermal energy from the components. Although two heat exchangers 23, 24 are shown in the cooling system 10 of
In operation, a fluid coolant flows through each of the heat exchangers 23, 24. As discussed later, this fluid coolant may be a two-phase fluid coolant, which enters inlet conduits 25 of heat exchangers 23, 24 in liquid form. Absorption of heat from the structure 12 causes part or all of the liquid coolant to boil and vaporize such that some or all of the fluid coolant leaves the exit conduits 27 of heat exchangers 23, 24 in a vapor phase. To facilitate such absorption or transfer of thermal energy, the heat exchangers 23, 24 may be lined with pin fins or other similar devices which, among other things, increase surface contact between the fluid coolant and walls of the heat exchangers 23, 24. Additionally, in particular embodiments, the fluid coolant may be forced or sprayed into the heat exchangers 23, 24 to ensure fluid contact between the fluid coolant and the walls of the heat exchangers 23, 24.
The fluid coolant departs the exit conduits 27 and flows through the vapor line 61, the condenser heat exchanger 41, the expansion reservoir 42, a loop pump 46, the liquid line 71, and a respective one of two orifices 47 and 48, in order to again to reach the inlet conduits 25 of the heat exchanger 23, 24. The loop pump 46 may cause the fluid coolant to circulate around the loop shown in
The orifices 47 and 48 in particular embodiments may facilitate proper partitioning of the fluid coolant among the respective heat exchanger 23, 24, and may also help to create a large pressure drop between the output of the loop pump 46 and the heat exchanger 23, 24 in which the fluid coolant vaporizes. The orifices 47 and 48 may have the same size, or may have different sizes in order to partition the coolant in a proportional manner which facilitates a desired cooling profile.
A flow 56 of fluid (either gas or liquid) may be forced to flow through the condenser heat exchanger 41, for example by a fan (not shown) or other suitable device. In particular embodiments, the flow 56 of fluid may be ambient fluid. The condenser heat exchanger 41 transfers heat from the fluid coolant to the flow 56 of ambient fluid, thereby causing any portion of the fluid coolant which is in the vapor phase to condense back into a liquid phase. In particular embodiments, a liquid bypass 49 may be provided for liquid fluid coolant that either may have exited the heat exchangers 23, 24 or that may have condensed from vapor fluid coolant during travel to the condenser heat exchanger 41. In particular embodiments, the condenser heat exchanger 41 may be a cooling tower.
The liquid fluid coolant exiting the condenser heat exchanger 41 may be supplied to the expansion reservoir 42. Since fluids typically take up more volume in their vapor phase than in their liquid phase, the expansion reservoir 42 may be provided in order to take up the volume of liquid fluid coolant that is displaced when some or all of the coolant in the system changes from its liquid phase to its vapor phase. The amount of the fluid coolant which is in its vapor phase can vary over time, due in part to the fact that the amount of heat or thermal energy being produced by the structure 12 will vary over time, as the structure 12 system operates in various operational modes.
Turning now in more detail to the fluid coolant, one highly efficient technique for removing heat from a surface is to boil and vaporize a liquid which is in contact with a surface. As the liquid vaporizes in this process, it inherently absorbs heat to effectuate such vaporization. The amount of heat that can be absorbed per unit volume of a liquid is commonly known as the latent heat of vaporization of the liquid. The higher the latent heat of vaporization, the larger the amount of heat that can be absorbed per unit volume of liquid being vaporized.
The fluid coolant used in the embodiment of
Water boils at a temperature of approximately 100° C. at an atmospheric pressure of 14.7 pounds per square inch absolute (psia). In particular embodiments, the fluid coolant's boiling temperature may be reduced to between 55-65° C. by subjecting the fluid coolant to a subambient pressure of about 2-3 psia. Thus, in the cooling system 10 of
In particular embodiments, the fluid coolant flowing from the loop pump 46 to the orifices 47 and 48 through liquid line 71 may have a temperature of approximately 55° C. to 65° C. and a pressure of approximately 12 psia as referenced above. After passing through the orifices 47 and 48, the fluid coolant may still have a temperature of approximately 55° C. to 65° C., but may also have a lower pressure in the range about 2 psia to 3 psia. Due to this reduced pressure, some or all of the fluid coolant will boil or vaporize as it passes through and absorbs heat from the heat exchanger 23 and 24.
After exiting the exits ports 27 of the heat exchanger 23, 24, the subambient coolant vapor travels through the vapor line 61 to the condenser heat exchanger 41 where heat or thermal energy can be transferred from the subambient fluid coolant to the flow 56 of fluid. The flow 56 of fluid in particular embodiments may have a temperature of less than 50° C. In other embodiments, the flow 56 may have a temperature of less than 40° C. As heat is removed from the fluid coolant, any portion of the fluid which is in its vapor phase will condense such that substantially all of the fluid coolant will be in liquid form when it exits the condenser heat exchanger 41. At this point, the fluid coolant may have a temperature of approximately 55° C. to 65° C. and a subambient pressure of approximately 2 psia to 3 psia. The fluid coolant may then flow to loop pump 46, which in particular embodiments, loop pump 46 may increase the pressure of the fluid coolant to a value in the range of approximately 12 psia, as mentioned earlier. Prior to the loop pump 46, there may be a fluid connection to an expansion reservoir 42 which, when used in conjunction with the pressure controller 51, can control the pressure within the cooling loop.
It will be noted that the embodiment of
As discussed above with regard to
On the other hand, mixing antifreeze with water substantially lowers the freezing point of the fluid coolant. Therefore, a fluid coolant including a mixture of antifreeze and water may be used in many environments where a fluid coolant including only water incurs difficulties. However, as discussed above, mixing antifreeze with water lowers the heat transfer coefficient of the fluid coolant, resulting in a less efficient way to cool a heat-generating structure.
Conventionally, these problems have been addressed by using a fluid coolant including a mixture of antifreeze and water and accepting the less efficient heat transfer, or using a fluid coolant including only water and removing the fluid coolant from the cooling loop when not in use. Accordingly, teachings of some embodiments of the invention recognize a cooling system for a heat generating structure including a flow of fluid coolant comprising a mixture of water and antifreeze, the system capable of separating the antifreeze and the water.
The cooling system 110 of
The heating device 130 may include a heat structure operable to heat a fluid coolant. In one embodiment, the heating device 130 may be a heat-generating structure, a boiler, or any other structure operable to heat the fluid coolant. In a further embodiment, the heating device 130 may further include a structure 112. The structure 112 is similar to the structure 12 of
The cooling system 110 may further include a fluid coolant including, but not limited to, a mixture of antifreeze and water. A fluid coolant comprising a mixture of antifreeze and water may have a freezing point range between −40° C. and −50° C. In one embodiment, this freezing point range occurs in a fluid coolant when the fluid coolant comprises a mixture between 60:40 and 50:50 (antifreeze:water). In certain embodiments, the lower freezing point of the fluid coolant prevents the fluid coolant from freezing when not being used in the cooling system 110 to cool the structure 112.
In operation, the heating device 130 is turned on, causing it to generate heat. The structure 112, in one embodiment, is not activated when the heating device 130 is turned on. A fluid coolant including a mixture of antifreeze and water enters the heating device 130, in liquid form, through a heating device inlet conduit 129. At the heating device 130, absorption of heat from the heating device 130 causes the water in the fluid coolant to substantially vaporize. The antifreeze in the fluid coolant, however, remains substantially in liquid form. In one embodiment, the antifreeze remains in liquid form because antifreeze has a lower vapor pressure than water.
Once heated, the fluid coolant, which includes both vapor consisting substantially of water and liquid consisting substantially of antifreeze, departs a heating device outlet conduit 131 and flows through a vapor line 161. The vapor line 161 is similar to the vapor line 61 of
The fluid coolant in vapor form, which includes substantially only water, flows through the condenser heat exchanger 141, the expansion reservoir 142, the loop pump 146, and the liquid line 171, in order to, once again, reach the heating device inlet conduit 129 of the heating device 130. The condenser heat exchanger 141, the expansion reservoir 142, the loop pump 146, and the liquid line 171 of
The condenser heat exchanger 141 transfers heat from the fluid coolant to a flow 156 of ambient fluid, thereby causing any portion of fluid coolant which is in the vapor phase to condense back into a liquid phase. The flow 156 of
In order to keep the cooling loop within a desired range of pressure, the control pump 138 may remove the liquid fluid coolant exiting the condenser heat exchanger 141. The liquid fluid coolant removed by the control pump 138 is stored, in one embodiment, in the expansion reservoir 142.
The liquid fluid coolant not removed by the control pump 138 flows back to the heating device 130 through the heating device inlet conduit 129. At the heating device 130, the liquid fluid coolant is, once again, heated, and the separation process repeats. In one embodiment, this process may repeat until the feedback from the mixture sensor 139 reaches a predetermined level of mixture of the fluid coolant. In one embodiment, the predetermined mixture level may be where the fluid coolant in the loop is within a range of 0-5% antifreeze. In another embodiment, the predetermined mixture may be where the fluid coolant in the loop is 5% antifreeze.
Once the predetermined mixture level is met, the controller 151 commands the solenoid valve 140 to close. In one embodiment, this prevents the fluid coolant from flowing into the heating device 130. When the solenoid valve 140 is closed, the fluid coolant, which now includes substantially only water, may now flow through inlet orifices 147 and 148, the inlet conduits 125, the heat exchangers 123 and 124, and the exit conduits 127. The inlet orifices 147 and 148, the inlet conduits 125, the heat exchangers 123 and 124, and the exit conduits 127 of
In another embodiment, when the structure 112 is no longer operating, and thus does not need to be cooled by the fluid coolant, the fluid coolant including substantially only antifreeze may be, once again, mixed with the fluid coolant including substantially only water. In one embodiment, the storage pump 134 pumps the fluid coolant including substantially only antifreeze from the storage reservoir 136 and into the vapor line 161, allowing the fluid coolant including substantially only antifreeze to mix with the fluid coolant including substantially only water. This allows the loop to be filled with the fluid coolant including a mixture of antifreeze and water. In one embodiment, the fluid coolant including a mixture of antifreeze and water lowers the freezing point of the coolant mixture. This may, in certain embodiments, prevent the fluid coolant from freezing in many commercial and military applications.
The cooling system 210 of
In operation, the heating device 230 is turned on, causing it to generate heat. The structure 212, in one embodiment, is not activated when the heating device 230 is turned on. In a further embodiment, when the heating device 230 is turned on, the expansion reservoir 242 is empty and both the storage reservoir 236 and the cooling loop include a liquid coolant including a mixture of antifreeze and water. The fluid coolant including a mixture of antifreeze and water enters the heating device 230, in liquid form, through a heating device inlet conduit 229. At the heating device 230, absorption of heat from the heating device 230 causes the water in the fluid coolant to substantially vaporize. The antifreeze in the fluid coolant, however, remains substantially in liquid form. In one embodiment, the antifreeze remains in liquid form because antifreeze has a lower vapor pressure than the water.
Once heated, the fluid coolant, which includes both vapor consisting substantially of water, and liquid consisting substantially of antifreeze, departs a heating device outlet conduit 231 and flows through a vapor line 261. The vapor line 261 of
The control pump 238 removes the fluid coolant in liquid form, which consists of the fluid coolant including substantially only water, exiting condenser heat exchanger 241. The control pump 238 stores the fluid coolant in liquid form in the expansion reservoir 242. As a result, the fluid coolant stored in the expansion reservoir 242 includes substantially only water. In one embodiment, as the control pump 238 removes the fluid coolant in liquid form, the storage pump 234 pumps the fluid coolant including a mixture of antifreeze and water from the storage reservoir 236 and into the cooling loop. In one embodiment, this allows the loop pressure to remain at a near constant level.
The fluid coolant including substantially only antifreeze exits the liquid bypass 249, flows into vapor line 261, and returns to the heating device 230 through the heating device inlet conduit 229. At the heating device 230, the fluid coolant, which, in one embodiment, also includes the fluid coolant pumped from the storage reservoir 236, is heated, and the separation process repeats. In one embodiment, this process continues until the expansion reservoir 242 is full of the liquid coolant including substantially only water. In another embodiment, this process continues only until the expansion reservoir 242 includes more of the liquid coolant including substantially only water than can be held in the cooling loop. In one embodiment, the expansion reservoir 242 and the storage reservoir 236 are each capable of holding more fluid coolant than the cooling loop.
In one embodiment, once the expansion reservoir 242 is full of the fluid coolant including substantially only water, the heating device 230 is turned off and the solenoid valve 239 is closed. The control pump 238 then backflushes the fluid coolant including substantially only water through the loop. As a result, the fluid coolant including substantially only water flows through the condenser heat exchanger 241, the vapor line 261, the heating device outlet conduit 231, the heating device 230, the heating device inlet conduit 229, and into the liquid line 271. In one embodiment, the backflushing causes the fluid coolant including substantially only water to force the fluid coolant including substantially only antifreeze into the storage reservoir 236. As a result, in one embodiment, the loop includes substantially only the fluid coolant including substantially only water, while the storage reservoir 236 stores the fluid coolant including substantially only antifreeze. In one embodiment, the backflushing further causes the storage reservoir 236 to also store some of the fluid coolant including substantially only water. In a further embodiment, the backflushing of the fluid coolant including substantially only water empties the expansion reservoir 242.
Once the cooling loop includes substantially only the fluid coolant including substantially only water, the solenoid valve 239, in one embodiment, is reopened, and the solenoid valve 240 is closed. As a result, the fluid coolant including substantially only water flows through inlet orifices 247 and 248, the inlet conduits 225, the heat exchangers 223 and 224, and the exit conduits 227. The inlet orifices 247 and 248, inlet conduits 225, heat exchangers 223 and 224, and exit conduits 227 are substantially similar to the inlet orifices 47 and 48, the inlet conduits 25, the heat exchangers 23 and 24, and the exit conduits 27, respectively, of
In a further embodiment, when the structure 212 is deactivated, the storage pump 234 pumps the fluid coolant including substantially only antifreeze from the storage reservoir 236 back into the loop. This causes the fluid coolant including substantially only antifreeze to mix with the fluid coolant including substantially only water. As a result, in one embodiment, the fluid coolant including a mixture of antifreeze and water provides freeze protection to the cooling system 210 when not in use. In a further embodiment, after the storage pump 234 mixes the fluid coolant in the cooling loop, the storage reservoir 236 still stores some of the fluid coolant including a mixture of antifreeze and water.
Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformation, and modifications as they fall within the scope of the appended claims.
