BACKGROUND OF THE INVENTION
The present invention is generally directed to a system for cooling electronic circuit components. In one aspect of the invention, an evaporator plate is provided which ensures uniform component cooling. In another aspect of the present invention, there is provided a thermosyphon cooling system which provides a cooling mechanism while, at the same time, permitting close and compact placement of electronic circuit chip modules. In yet another aspect of the present invention, there is provided a cooled, compact electronic system which permits placement of electronic modules in a dense configuration within the central portion of a computer frame assembly while, at the same time, providing air cooling capability in spite of the component density and access difficulty.
In various electrical and electronic systems, certain designs result in the generation of significant amounts of thermal energy which must be removed in order for the system to continue to function. When these systems are data processing devices, it is noted that the thermal load that results is also a function of the frequency at which the device is operated. For example, it is well known that a doubling in the frequency at which a device operates generally produces a doubling in the amount of heat which must be removed from the system.
Accordingly, as systems, particularly computer systems, are driven to operate at ever-increasing speeds, there is a corresponding need to provide improved cooling systems for these systems. Even more particularly with respect to data processing systems, their speed of operation is dependent upon providing short signal paths between various modules, chips and components. Accordingly, it is seen to be very desirable to place computer processing modules in relatively close proximity to one another and to memory modules. However, close and compact configurations of these modules can render it difficult to provide air-cooling capabilities especially when a relatively hot processing unit is surrounded by other peripheral components to which it is attached in a manner which provides as short a set of signal paths as is possible.
Accordingly, it is seen that it is very desirable to be able to cool computer systems in a manner which still permits close packaging of their electronic component modules and still maintain compatibility with frame size and with the thermal capabilities of various computer installations. It is also noted that this cooling should be provided in a manner which is effective yet reliable over relatively long periods of time, particularly when such systems are used in on-line transaction processing environments.
One of the ways proposed herein for cooling such systems is through the utilization of thermosyphon-based cooling units. Such units typically employ evaporators which are oriented in a vertical direction corresponding to placement of electronic modules within the system. Vertical placement is decidedly preferred in such systems since vertical module orientation facilitates any convectional cooling that occurs. However, this vertical placement forces the evaporator fins to be quite long and, accordingly, it is seen that the vertical orientation sometimes can result in the drying out of the coolant liquid at upper internal regions of the evaporator thus rendering that portion of the evaporator somewhat ineffective for its desired cooling purposes.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, a cooling system for electrical or electronic equipment is provided which includes a substantially flat evaporator which has a thermally conductive surface for direct and immediate contact with the electrical equipment which is to be cooled. A condenser which is disposed above and sufficiently far away from the evaporator so as to avoid interference with close placement of separately cooled portions of the electronic or electrical equipment is likewise provided in a thermosyphon system. A vapor line extends from an upper portion of the evaporator to an upper portion of the condenser. Similarly, a return line extends from a lower portion of the condenser to a lower portion of the evaporator. This permits liquid coolant converted to vapor in the evaporator to be introduced into the condenser where it is cooled, condensed and is returned as a liquid which flows back to the evaporator in a closed loop fashion. In preferred embodiments of the present invention, there is also provided an air-moving device (AMD) such as a fan for removing heat from the condenser. In lower power applications, natural convection through the condenser may be employed.
In another aspect of the present invention, the thermosyphon system described above includes an evaporator plate which is particularly effective for ensuring that coolant is not boiled away entirely from any region of the evaporator. In particular, the evaporator includes a substantially flat, sealable housing with an inlet on its lower portion and an outlet disposed on an upper portion of the housing. This housing includes a thermally conductive outer surface (preferably flat) for direct thermal contact with a body, object or equipment to be cooled. Within the housing itself, a first internal conduit extends substantially upwardly from the inlet port. A second internal conduit extends substantially downwardly from the outlet port on the opposite side of the housing. Additionally, there is also included within the housing a plurality of substantially horizontally oriented individual evaporation chambers which are in flow communication between the first conduit on one side of the housing and the second conduit on the opposite side of the housing. These evaporation chambers provide connections between the internal conduits so as to provide flow communication across the evaporator and the housing. Additionally, it is noted that the connections to the conduits are such that the connection to the first conduit is very much preferably located below the connection to the second conduit. The evaporator plate also preferably includes a sequence of substantially parallel baffles within at least one of the individual evaporation chambers (and preferably in all of them). These baffles assist in ensuring a uniform distribution of liquid phase coolant throughout the entire evaporator and its housing so as to ensure uniform cooling of the thermally conductive outer surface of the housing. This, therefore, ensures that the devices to be cooled are in fact cooled uniformly. Additionally, it is noted that the baffles may also be configured in a custom fashion to ensure the flow of liquid coolant to regions having chip “hot spots.”
In yet another aspect of the present invention, the thermosyphon system and evaporator plate described above are employed in conjunction with a structural frame which supports one or more printed circuit boards. At least one of these printed circuit boards has electronic modules, which are to be cooled, disposed on it. An evaporator is disposed in thermal contact with the module and a condenser is disposed within or on the frame in a position above the evaporator. A vapor line extends from an upper portion of the evaporator to an upper portion of the condenser. A condensate (return) line extends from a lower portion of the condenser to a lower portion of the evaporator. The evaporator, the condenser, the vapor line and the condensate line form a closed loop for containing a coolant fluid. An air-moving device is provided for removing heat from the condenser. The frame members provide support, concealment and/or protection for either or both of the vapor and condensate lines.
The cooling system described above has the particular advantage that it typically requires no moving parts other than the air-moving device which moves a cooling flow of air over and/or through the condenser.
Accordingly, it is an object of the present invention to provide a cooling system for electronic modules in a fashion which permits close, vertical module placement.
It is also an object of the present invention to provide a cooling system which employs air cooling but which does not require the presence of bulky, space-consuming air-moving devices to be present in the immediate vicinity of the electronic modules.
It is also an object of the present invention to provide an evaporator plate for which the problem of localized coolant dry spots is significantly ameliorated.
It is a still further object of the present invention to eliminate the need for pump-based water cooling systems which often require auxiliary plumbing devices such as expansion tanks.
It is a still further object of the present invention to reduce the volume of cooling hardware which is required immediately adjacent to electronic modules to be cooled so as to therefore reduce the board or card pitch (in the linear density sense) thus leading to enhanced processor and system operation speeds.
It is also an object of the present invention to provide a cooling system which is relatively insensitive to module power variations.
It is a still further object of the present invention to reduce the number of mechanical and/or moving devices associated with a cooling system for data processing equipment.
It is also another object of the present invention to provide a mechanism for operation of data processing and the like equipment at increased speeds and frequencies.
It is a still further object of the present invention to take advantage of the simplicity of thermosyphon-operating characteristics.
It is yet another object of the present invention to provide a closed and sealable thermosyphon cooling system which can be partially filled with a coolant liquid and vapor phase materials which are maintained at subatmospheric pressures to facilitate conversion to the vapor phase at a lower temperature.
It is also an object of the present invention to provide a cooling system which is operable using simple and uncomplicated coolants such as water and/or mixtures of water and alcohol, fluorocarbons and/or, much less preferably, chlorofluorocarbons.
It is also an object of the present invention to provide a packaging arrangement for data processing equipment which includes thermosyphon heat removal means.
It is also an object of the present invention to provide packaging for electronic and/or electrical equipment which is packagable in standard frame and cabinet arrangements and which provide heat rejection and removal arrangements which are located at relatively exterior portions of the frame cabinetry.
It is a still further object of the present invention to provide a cooling system which permits the placement of printed circuit boards at relatively closely spaced intervals to one another, particularly in a standard cabinet and frame package.
It is also an object of the present invention to provide a cooling system wherein coolant is driven in a closed loop around the system solely by action of gravity and the density difference between liquid and vapor phases.
Lastly, but not limited hereto, it is an object of the present invention to enhance the thermal characteristics of vertically oriented evaporators.