# Patent

## Title
Thermal control system for rack mounting

## Abstract

A thermal control system of a 3 U height includes various modules for providing temperature control in a rack environment. The modules may be, for example, a power module, user interface module, various different pump assemblies, various different models of fan assemblies, HTAs, and/or a serial communication interfaces.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application is a continuation of U.S. patent application Ser. No. 12/176,084, filed Jul. 18, 2008 now U.S. Pat. No. 7,804,686 and incorporated herein by reference. U.S. patent application Ser. No. 12/176,084 is a continuation of U.S. patent application Ser. No. 11/202,885, filed on Aug. 12, 2005 now abandoned and incorporated herein by reference. U.S. patent application Ser. No. 11/202,885 claims priority to U.S. Provisional Patent Application No. 60/601,013, filed Aug. 12, 2004, and incorporates by reference for all purposes the entire disclosures of U.S. patent application Ser. No. 09/328,183, now U.S. Pat. No. 6,935,409, filed Jun. 8, 1999 and U.S. Pat. No. 6,462,949, entitled “Electronic Enclosure Cooling System.” This patent application incorporates by reference each of U.S. Provisional Patent Application No. 60/601,013, U.S. patent application Ser. No. 09/328,183, and U.S. Pat. No. 6,462,949.


BACKGROUND
1. Technical Field
The present invention relates to thermal control systems, and more particularly, but not by way of limitation, to low profile, rack mounted thermal control systems for cooling or heating equipment disposed in or in the vicinity of an equipment rack.
2. Background of Related Art
As the evolution of computers continued from mini-computers that filled entire rooms with equipment to PC modules similar to the personal computer known today, rack mounted equipment decreased in popularity. However, with the introduction of new electronic equipment, such as slice servers and laser systems, racks are returning to the computing environment. Rack mount enclosures are compact in design and allow for mounting of various components (e.g., servers, laser systems, chillers, etc.) in a stacked style configuration. Utilizing racks allows a user to include various rack mounted components in the rack, decreasing the foot print, while the components remain easily accessible for maintenance.
By mounting multiple components in a rack heat is increased, thereby causing deterioration and possible failure of many of the components. For example, most laser systems, such as those utilized for medical or industrial applications, generate a large amount of heat that requires cooling, via a chiller, in order to maintain proper function. In addition, many components, such as laser systems, perform poorly when subject to vibration and noise that many compressor-based chillers exhibit.
Conventional racks for the components as described herein are typically constructed of predetermined spatial parameters. For example, the height of an individual rack area, or “mounting space” adapted for conventional electronic components and the like is referred to in multiples of “U”. Each “U” (standing for the word “unit”) is equal to 1.75 inches. A 3 U height is therefore 5.25 inches. It is this “U” height that defines the standard rack mounting spatial relationship relative to a typical “19” inch wide mounting space. The “19” inch reference refers in actuality to the space allotted outside the mounting spaces for the equipment or component face plate. The inside of the mounting space generally has an inside dimension on the order of 17.5 inches. Using these spacing parameters, components and equipment mounted within such a rack are typically of a height that is a “U” multiple with a face panel on the order of 19 inches wide.
Although many components, such as servers and laser systems, are available in a height that is on the order of a “U” multiple for placement in the conventional rack, rack mounted chillers typically require a height of more than 3 U to offer effective cooling to the surrounding components. Some compressor-based units may require as much as an 8 U height. It should be noted, however, that such height is critical to space considerations of the overall rack. Conventional equipment racks only have a specified number of U's available and the higher the number of U's required for temperature control equipment, the fewer U's available for the necessary equipment. It is for this reason that special height considerations are important along with the functionality of the temperature control system.
Today's cooling technology typically includes passive cooling systems, compressor-based systems, and thermoelectric systems. In certain passive cooling systems, the air to be cooled is circulated over an air-to-air heat exchanger, which includes folded, finned heat exchangers, heat pipes, etc. The heat is then exchanged with the outside ambient air. As the amount of heat to be removed from the area increases, the size of the air-to-air heat exchanger increases. Compressor-based systems function by using a refrigerant and the cooling function is achieved by the compression and expansion of the refrigerant such as U.S. Patent Application Publication 2004/0221604, entitled “Liquid Cooling System for a Rack-mount Server System,” which is hereby incorporated by reference. These compressor-based systems typically weigh over seventy pounds and create unwanted vibrations. Thermoelectric temperature control systems use thermoelectric devices that pump heat using the Peltier effect. Typical thermoelectric devices incorporate a thermoelectric component that utilizes electrical current to absorb heat from one side of the component and dissipate that heat on the opposite side.
In addition to the above, instances arise where heating and/or temperature stabilization is equally important. For example, laser systems require a stable heat and temperature environment because the frequency of the light is dependent on the temperature of the diode. When rack-mounted systems that are vibrationally sensitive require precise temperature control, a compressor based system cannot be used. Thus, a more technologically complex scenario can evolve. A simple chiller is generally not capable of also performing a heating function without adding resistive elements. Thermal electric temperature control systems using thermal electric devices are, as described above, capable of both heating and cooling, low vibration, relatively high Coefficient Of Performance (“COP's”) (ability to remove heat), low noise, and low profile.
U.S. patent application Ser. No. 09/328,183 (the '183 patent application), now U.S. Pat. No. 6,935,409, assigned to the assignee of the present invention teaches a heating and cooling system with low vibration, relative high COP's, low noise and low profile. The low profile cooling system of the '183 patent application is, as stated therein, particularly well suited for cooling power amplifiers and other electronic components. In one embodiment, a heat transfer fluid is circulated in a closed loop to the area of components that generate heat. This approach allows the design, implementation and utilization of such thermoelectric cooling systems utilizing low profile extrusions capable of cooling high watt density sub assemblies such as a power amplifiers and filters commonly secured in rack mounted equipment or equipment that may be mounted around a conventional electronic component rack.
It would therefore be a distinct advantage relative to the above-described technology to provide a thermal control system that would be of low vibration, high efficiency, and yet easily mountable within a conventional rack with minimal “U” utilization.
SUMMARY
The present invention relates to thermal control systems for equipment. More particularly, one aspect of the invention relates to low profile, rack-mounted temperature control systems for cooling or heating equipment disposed in or in the vicinity of an equipment rack. The control system is constructed in a 3 U (3×1.75′′=5.25 inches) height for placement in standard “19” inch wide equipment rack units (inside dimension of unit is in the order of 17-1⁄2 inches.
In another aspect, the present invention relates to a thermal control system including at least one Heat Transfer Assembly (HTA) module. The HTA modules are formed of low profile extrusions having micro channels formed therein. The HTA's may include external fins and/or high density bonded fin heat sinks.
In another aspect, one embodiment of the invention includes a thermal control system for heating and cooling select equipment disposed in the vicinity of conventional 19 inch equipment racks having an interval mounting space width on the order of 17.5 inches for the placement of equipment therein, and a height on the order of 3 U. The system further includes at least one heat transfer assembly module of the type formed with a plurality of low profile extrusions having micro channels formed therein and disposed within a chassis for the flow of heat transfer fluid for thermal control and a height no more than 3 U.
In another aspect, the above-described embodiment includes the heat transfer fluid being circulated in a closed loop to cool or heat components within the rack wherein the thermal control system is disposed. In one embodiment, the heat transfer fluid includes a water/glycol mixture, and in another embodiment it includes a water/alcohol mixture.
In yet another embodiment, the above-described invention includes the ability to customize the design of the 3 U system and allow on the order of three heat transfer assemblies to effect cooling and/or heating of the temperature control system. A plurality of internal fan assemblies may also be further utilized in conjunction with the heat transfer fluid for the effective transfer of heat therefrom.



BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the method and apparatus of the present invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein:
FIG. 1 is a top view of a temperature control system in accordance with an embodiment of the present invention;
FIG. 2 is a front view of a temperature control system in accordance with an embodiment of the present invention;
FIG. 3 is a back view of a temperature control system in accordance with an embodiment of the present invention;
FIG. 4A is a side-elevation view of the temperature control system with rubber feet attached for standing in a vertical position;
FIG. 4B is a front elevation view of the temperature control system with rubber feet attached for standing in a vertical position;
FIG. 5A is a perspective view of the temperature control system with rubber feet attached for standing in a horizontal position;
FIG. 5B is a bottom view of the temperature control system with rubber feet attached for standing in a horizontal position;
FIG. 5C is a side elevation view of the temperature control system with rubber feet attached for standing in a horizontal position;
FIG. 5D is a front elevation view of the temperature control system with rubber feet attached for standing in a horizontal position;
FIG. 6 shows the temperature control system as it would fit into a conventional rack mount;
FIG. 7 is a perspective view of an HTA module of the type used in FIG. 1;
FIG. 8 is a table detailing various elements that can be selected by a customer to be included in the chassis of the temperature control system of the present invention; and
FIG. 9 is a block diagram of a temperature control system in accordance with an embodiment of the present invention.



DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE INVENTION
Referring now to FIG. 1, a top view of a temperature control system 100 in accordance with an embodiment of the present invention is illustrated. The temperature control system 100 utilizes a heat transfer fluid that is circulated in a closed loop to cool or heat components within a conventional rack. The heat transfer fluid may be, for example, a water/glycol mixture, although other heat transfer fluids may be utilized. In one embodiment, the temperature control system 100 is contained in a chassis 110 having an available internal space 111, a front face 201, and a rear face 301. In one embodiment, three HTA modules 102 are utilized to effect cooling and/or heating in the temperature control system 100, however embodiments of the present invention may include more or fewer HTA modules as desired. As clearly illustrated in FIG. 1, the HTA modules 102 are secured in a chassis 110 in a continuous heat transfer chassis region 103. Spaces 106 are disposed between adjacent HTA modules 102. The HTA modules 102 are oriented parallel to each other and perpendicular to a depth 107 of the chassis 110. The continuous heat transfer chassis region 103 occupies over half of the available internal space 111 of the chassis 110. The temperature control system 100 may also include up to six internal fan assemblies (not shown) and an addition three internal fans with an external fan tray. The fans may be oriented in a push/pull fan arrangement or other arrangement as desired. In alternate embodiments, fans on the heat transfer side are not included. Instead, the temperature control system 100 may utilize micro extrusions to transfer power from the Thermoelectric Cooling Module (“TEC”) via water. The power supplies that drive the TEC's may have variable output (5-135 Vdc) which can be varied by the controller using, for example, a Pulse Width Modulation (“PWM”) signal. This variable output design of the power supply can modulate the power to the TEC's to achieve precise temperature control. This variable output also allows the chiller to only use the minimum required input power to provide the optimal control. This lowers the overall input power required by lowering the drive voltage to the TEC's in applications that have low heat loads. A preferred embodiment of the present inventions has thermal performance capabilities of 725 Watts at 0° C. delta T supply minus ambient air. An alternative embodiment of the present inventions utilizing a plant water supply has capabilities in excess of 1,100 Watts at 0° C. delta T supply minus service water.
The fan assembly 206 maximizes efficiency of the temperature control system 100 by maximizing the airflow (denoted by arrow 231) to the HTA modules 102. In one embodiment, shown in FIG. 7, the HTA modules of the present invention are formed of low profile extrusions 220 having a plurality of micro channels 223. Each micro channel 223 has a micro channel inlet and a micro channel outlet. The low profile extrusions 220 are preferably formed with heat sinks 231 and external fins 230 to maximize heat transfer, if space allows. The fins 230 are constructed having spaces 223 disposed there between. In a typical embodiment, the HTA modules are arranged so that the spaces 233 are parallel to a depth 107 of the chassis 110. The micro channel inlets are in fluid communication with each other, and to an inlet channel, by an inlet end cap. Similarly, micro channel outlets are in fluid communication with each other, and to the outlet channel, by an outlet end cap. The heat transfer fluid (denoted by arrow 232) is circulated through the inlet channel, the low profile extrusion 220, the outlet channel, and tubing via the pump 104. As shown in FIG. 1, in a typical embodiment, the heat transfer fluid 232 flows through the low profile extrusion 220 in a direction perpendicular to the depth 107 of the chassis 110. The pump 104 is disposed within the chassis 110 in a continuous pump region 101. The continuous pump region 101 occupies less than half of the available internal space 111 of the chassis 110 and is disposed adjacent to the continuous heat transfer chassis region 103. The continuous pump region 101 and the continuous heat transfer region 103 are separated by a boundary 105. The boundary 105 is disposed parallel to the depth 107 of the chassis 110 and runs between an interior aspect 108 of the front face 201 to an interior aspect 109 of the rear face 301. Alternatively, the temperature control system 100 may be evacuated and charged with fluid which is then circulated via the pump 104. Further details regarding low profile extrusions 220 and the heat transfer fluid flow system and method herein referenced are set forth and shown in U.S. patent application Ser. No. 09/328,183, now U.S. Pat. No. 6,935,409 referenced above and incorporated herein by reference.
The temperature control system 100 utilizes a pump 104, such as a positive displacement, centrifugal, or turbine style magnetically coupled pump. The pump 104 is of such a size as to fit in the 3 U configuration and may have a variety of gear sizes, port sizes, etc. as needed. The customized selection of the pump and other components may also be provided in the 3 U system as described below. A preferred embodiment of the present invention has flow rate capabilities on the order of one gallon per minute or four Liters per minute.
The temperature control system 100 is formed in a modular design to allow flexibility and versatile configuration for a variety of customers. For example, a customer may request one or two HTAs with a smaller displacement pump in order to create a chiller with less depth, allowing the chassis to only be fifteen inches in depth compared to the standard twenty three inches. In addition, the present invention also may have high thermal cycle module capability. A preferred embodiment of the present invention has the capability of remote temperature monitoring utilizing external temperature sensors such as thermistors or Resistance Temperature Detection (“RTD”) devices, etc. A preferred embodiment of the present invention also allows user communication in a variety of manners including serial USB ports, Ethernet ports, RS485 ports and RS232, etc. The present invention has the capability of operation off a DC power source (150-340 Vdc) or universal AC voltage operation (95-250 Vac, 45-70 Hz). There are various wiring selections that can be utilized to maximize the efficiency of the system based on the input voltage. Conductivity meters and voltage sensors may also be utilized to ensure the accuracy of the system. Another preferred embodiment of the present invention utilizes flow meters to monitor air flow across the HTA's and the fluid flow of the heat transfer fluid. The fluid in the present invention can utilize various fluid connections and types depending on the specific needs of the user. One contemplated embodiment utilizes the present invention in conjunction with both external heat exchangers including air and plant liquid coolers. Utilizing the flow meters and conductivity meters in conjunction with the temperature sensors gives the thermal control system the capability of maintaining the temperature of the heat transfer fluid to within +/−0.05 degrees Celsius.
Another aspect of one embodiment of the present invention is the flexibility that the 3 U design affords relative to the customer requests referred to above. As seen in FIG. 1, the temperature control system 100 includes a chassis 110 that provides a basic frame for a variety of options that may be utilized therewith pursuant to customer specification while maintaining the 3 U height limitation for rack mounting in accordance with the principles of the present invention. In addition to the 3 U height limitation, the present invention weighs approximately fifty-four pounds, making it suitable for a variety of applications. FIG. 8 is thus submitted for illustrating the high level of specificity with which a customer may select various elements within the temperature control system 100 and securement to the chassis 110. By utilizing the chart shown in FIG. 8, the manufacturer of the present invention is able to utilize an “assembly line” type of fabrication without the need for multiple redesign and re-engineering to meet the 3 U and/or performance criteria. The various elements as set forth in the chart shown in FIG. 8 can be selected and will all fit within the chassis 110 and within the 3 U module fitting into a 3 U mounting space of the conventional rack, even though the temperature control system 100 has been customized by a given customer.
Referring now to FIG. 2, a front view of the temperature control system 100 is illustrated. The temperature control system 100 exhibits a front to back air flow and easily removable air filter. The front panel of the temperature control system 100 includes a user interface 200, such as a membrane keypad or other user interface. The user interface 200 allows the user to enter various information (e.g., set various conditions, adjust fan speed, adjust temperature, display flow, heat load, thermal performance, etc.) for use by the temperature control system 100. At least one fan guard 202 protects the fan blades of the fan assemblies 206. The front panel may also include fluid connections 204 including but not limited to quick connections National Pipe Taper (“NPT”), etc.
In operation, the 3 U system of the present invention affords multiple advantages for both the customer and user. Thermal control systems utilizing a 3 U height and manifesting low vibration consistent with the technology set forth and described herein is a distinct advantage. The ability to customize the particular operational system parameters within the temperature control system 100 is likewise of significant benefit. The system 100 can be upgraded as required while manifesting quiet operation, low vibration and being energy efficient even after upgrades. The upgrades are, as referenced above, integral elements that may be selected by the customer and therefore are all compatible with the remaining elements within the 3 U system of the present invention.
Referring now to FIG. 3, a rear panel of the temperature control system 100 is illustrated. The rear panel also includes fan guards 202 and fluid connections 204 similar to those of the front panel. Also oriented on the rear panel is a power entry module 300 for supplying power to the thermal control system 100. A reservoir filler quick disconnect 304, communication IP ports including alarms, stand by signals, expansion/accessories, electronics side vents, and an RS232 interface connection 302 are included on the rear panel as well. A circuit breaker 306 prevents the thermal control system 100 from being overloaded by a surge in power.
Referring now to FIGS. 4A and 4B, the thermal control system is shown with the face plate trimmed down and with feet added. This embodiment utilizes the advantages of the slim, low profile design, low vibration, and precise temperature control in a bench top vertical unit. An alternative embodiment of the bench top unit has feet 401 attached in such a way so that the face plate is oriented in the same direction as when mounted in a rack giving a bench top horizontal unit. These configurations keep the unit stable even when not mounted in a conventional rack, allowing it to be used for a plurality of purposes.
Referring now to FIGS. 5A-5D and FIG. 6, the thermal control system is shown disposed in a conventional rack mount 602. The 3 U height of the chassis allows it to fit in the slots 604 of the conventional rack mount 602, taking up no more space than most standard electronic equipment. The design of the chassis also allows the thermal control system to be secured to the conventional rack mount 602 in number of different ways, one being with screws through the faceplate.
There are several modifications and variations of the innovative concepts of the present application that are contemplated and within the scope of the patented subject matter. A few examples of these alternative embodiments are given below, but in no way do these examples enumerate all possible contemplated embodiments of the present application.
For example, one contemplated embodiment of the present invention utilizes two temperature control systems for increased cooling capabilities. The present invention has the capability of being connected in a Master/Slave type relationship where both temperature control systems have the capability of being mounted in two separate mounting spaces of a conventional mounting rack.
An example of an alternative embodiment includes mounting the thermal control system independent of the conventional mounting rack. Rubber feet may be added and the system can be placed on a desktop.
Another alternative implementation that is contemplated would be to use the thermal control system disclosed in the present application in conjunction with an external heat exchanger. In this embodiment, the thermal control system would cool the air that passes over the micro channels and at the same time warm the heat transfer fluid. The heat transfer fluid could then be cooled by some external heat exchanger, e.g. plant water. This embodiment may be desirable to use in a closed environment such as a clean room, where the only air exchange possible is through recirculation.
Another example embodiment includes using the thermal control system for the temperature regulation of vehicle parts or compartments in a vehicle.
FIG. 9 is a block diagram of a temperature control system in accordance with an embodiment of the present invention. A system 900 includes a chassis 902, an external heat exchanger 904, and a monitor 906. The external heat exchanger 904 is thermally exposed to adjacent select equipment 908. The chassis 902 includes a plurality of heat transfer modules 910. The heat transfer assembly modules 910 are formed with a plurality of low profile extrusions having micro channels formed therein for the flow of heat transfer fluid therethrough. The monitor 906 is operable to monitor airflow across the micro channels, fluid flow of the heat transfer fluid, and performance of the micro channels. In a typical embodiment, a temperature of the heat transfer fluid is maintained within one-tenth of one degree Celsius of a temperature set by the user. An alarm 912 is activated when the temperature of the heat transfer fluid is outside the range of satisfactory temperatures. The system 900 is contained within an isolated closed environment 914.
The previous description is of a preferred embodiment for implementing the invention, and the scope of the invention should not necessarily be limited by this description. The scope of the present invention is instead defined by the following claims.

## Claims

1. A precision thermal control method of heating and cooling select equipment utilizing a heat transfer fluid in conjunction with an external heat exchanger, the method comprising the steps of:
providing a chassis having a height of no more than 3 U, the chassis comprising:
a front face;
a rear face
a continuous heat transfer chassis region occupying over half of an available internal space of the chassis, the continuous heat transfer chassis region not being coextensive with the available internal space of the chassis, the continuous heat transfer chassis region extending from an interior aspect of the front face to an interior aspect of the rear face; and
a continuous pump region comprising a pump, the continuous pump region occupying less than half of the available internal space of the chassis, the continuous pump region extending from an interior aspect of the front face to the interior aspect of the rear face, the continuous pump chassis region and the continuous heat transfer chassis region positioned adjacent to each other along a boundary oriented parallel to a depth of the chassis;
securing within the chassis a first plurality of fan assemblies disposed adjacent to the front face, the first plurality of fan assemblies connecting the continuous heat transfer chassis region with the exterior environment;
securing within the chassis a second plurality of fan assemblies disposed adjacent to the rear face, the second plurality of fan assemblies connecting the continuous heat transfer chassis region with the exterior environment, the second plurality of fan assemblies operable to allow an airflow through the continuous heat transfer chassis region;
providing a first plurality of fluid connections on a portion of the front face corresponding to the boundary;
providing a second plurality of fluid connections on a portion of the rear face corresponding to the boundary;
securing to said chassis within the continuous heat transfer chassis region a plurality of heat transfer assembly modules of a type formed with a plurality of low profile extrusions having micro channels formed therein for the flow of the heat transfer fluid therethrough, the plurality of heat transfer assembly modules oriented parallel to each other and perpendicular to the depth of the chassis;
orienting the plurality of heat transfer assembly modules within the continuous heat transfer chassis region such that a plurality of spaces are disposed there between;
securing a power supply within said chassis for powering said plurality of heat transfer assembly modules;
circulating the heat transfer fluid through each of the plurality of low profile extrusions in a direction perpendicular to the depth of the chassis;
circulating air through the continuous heat transfer region in a direction parallel to the depth of the chassis; and
pumping said heat transfer fluid in a closed loop to said external heat exchanger for the cooling of said heat transfer fluid.

2. The method as set forth in claim 1, wherein said precision thermal control method is implemented inside an isolated closed environment.

3. The method as set forth in claim 1, further comprising circulating the heat transfer fluid in a closed loop to cool or heat the select equipment.

4. The method as set forth in claim 3, wherein the select equipment and the chassis are disposed in a conventional system rack.

5. The method as set forth in claim 3, further comprising fins extending from said plurality of low profile extrusions for cooling therewith.

6. The method as set forth in claim 3, further comprising using a water/glycol mixture for the heat transfer fluid.

7. The method as set forth in claim 3, further comprising using a water/alcohol mixture for the heat transfer fluid.

8. The method as set forth in claim 3, further comprising using distilled water for the heat transfer fluid.

9. The method as set forth in claim 3, further comprising using dionized water for the heat transfer fluid.

10. The method as set forth in claim 1, further comprising allowing a user to set a range of satisfactory temperature of the heat transfer fluid.

11. The method as set forth in claim 10, further comprising adjusting a fan speed of the first plurality of fan assemblies and/or the second plurality of fan assemblies and a flow rate of the heat transfer fluid automatically in at least partial dependence on the range of satisfactory temperature.

12. The method as set forth in claim 10, further comprising recording a temperature of the heat transfer fluid.

13. The method as set forth in claim 12, further comprising displaying recorded temperature of the heat transfer fluid.

14. The method as set forth in claim 10, further comprising activating an alarm when a temperature of the heat transfer fluid is outside the range of satisfactory temperature.

15. The method as set forth in claim 12, further comprising monitoring airflow across the micro channels, the fluid flow of the heat transfer fluid, and the performance of the micro channels.

16. The method as set forth in claim 15, further comprising maintaining the temperature of the heat transfer fluid to within one-tenth of one degree Celsius of a temperature of the range of satisfactory temperature set by the user.

17. The method as set forth in claim 1, further comprising adapting the chassis to stand in one of a vertical direction or a horizontal position by adding a plurality of support feet to at least one side of the chassis.