TECHNICAL CONTRIBUTION

The present disclosure relates to computer room cooling systems. More particularly, the present disclosure relates to a computer room cooling system with a bifurcated heated air return pathway.

BACKGROUND

FIG. 1 is a block diagram illustrating a heated air return pathway, of the prior art, through a computer room 15. To assist in the description of items in the figures, FIG. 1 identifies several planar interfaces. The terms “plane” and “co-planar”, as used in this description, are intended to describe cross-sectional volumes (either horizontal or vertical) within the computer room 15, rather than ideal planes having no volume. A first horizontal plane 21 is co-planar with an FCP top surface of the false ceiling plenum 16. A second horizontal plane 22-a is co-planar with the FCP bottom surface of the false ceiling plenum 16, as well as the cold aisle ceiling 15A1 of the cold aisle 15A and the hot aisle ceiling 15B1 of the hot aisle 15B. A third horizontal plane 23 is co-planar with a top surface of a raised floor plenum 17. A fourth horizontal plane 24 is co-planar with a bottom surface of the raised floor plenum 17. A first vertical plane 31 is co-planar with a first side of the hot aisle 15B. A second vertical plane 32 is co-planar with a second side of the hot aisle 15B. A third vertical plane 33 is co-planar with one side edge of the false ceiling plenum 16.

The computer room 15 of FIG. 1 includes a cold aisle 15A and a hot aisle 15B separated by a server rack row 15C. The cold aisle 15A receives cooled air via a raised floor plenum inlet 15Dl-a and/or a fan wall inlet 15Dl-b. The cooled air in the cold aisle 15A is drawn through the server rack rows 15C into the hot aisle 15B, heated by electronics (e.g., servers and/or data storage devices) mounted in the server rack rows 15C. The heated air is drawn from the hot aisle 15B through a hot aisle ceiling 15B1 (often comprised of perforated ceiling tiles in the prior art) into a false ceiling plenum 16 and back to an air handling unit (not shown, see item see item 15D2 of FIG. 2). The heated air collection duct (HACD) 14C is mounted at the third vertical plane 33 on one side edge of the false ceiling plenum 16.

FIG. 2 is a block diagram illustrating a dual coil cooling system 10, of the prior art, for a computer room 15 employing a free cooling tower 11 and a chiller 13. As in FIG. 1, the computer room 15 includes a cold aisle 15A and a hot aisle 15B separated by a server rack row 15C. The cold aisle 15A receives cooled air from an air handling unit (AHU) 14 via a cooled air inlet 15D1. The cooled air is drawn through the cold aisle 15A and heated by electronics (e.g., servers and/or data storage devices) mounted in the server rack row 15C. Heated air is drawn from the hot aisle 15B to back the AHU for cooling via a heated air outlet 15D2. The AHU 14 includes a free cooling coil 14A and a trim cooling coil 14B for the cooling of the heated air received from the hot aisle 15B. The free cooling coil 14A receives a first free coolant flow from a free cooling tower 11 to pre-cool the heated air. The trim cooling coil 14B receives a trim coolant flow from an evaporator passage 13B of the chiller 13 to further cool the heated air. The AHU includes a fan (not shown) to pump the heated air and the cooled air. The chiller 13 includes a condenser passage 13A to receive a second free coolant flow from the free cooling tower 11. The free cooling tower 11 receives ambient air 12 from an outer environment to cool the free coolant delivered via: (i) the first free coolant flow to the free coiling coil 14A of the AHU 14; and (ii) the second free coolant flow to the condenser passage 13A of the chiller 13.

Free cooling towers 11 derive their cooling benefit from a relatively low ambient air temperature (in comparison to the heated air of the computer room 15) of an outside environment and the evaporation of water vapor within the free cooling tower 11. Free cooling towers 11 are most efficient therefore when they interact with the ambient air 12 of an outside environment with both a relatively low temperature and a low humidity (for greater evaporation of water vapor). While the trim cooling coil 14B of the AHU 14 can be employed to further cool the heated air of a computer room 15 located in a tropical or otherwise high humidity environment, chillers 13 require substantial electrical power to function. The high expense of cooling for data centers located in tropical or otherwise high humidity environments can force these businesses to outsource their data computing to offshore data center locations. Such offshoring can complicate the management of the business’ data computing functions and complicate the business’ procedures for local data privacy rules compliance.

What is needed, therefore, is a computer room cooling system that can be maximize the efficiency of free coiling towers for computer rooms 15 operating in the tropics or otherwise high humidity environments.

Heat generation within a computer room 15 can also fluctuate due to uneven computing needs during weekly or daily cycles, activation of new server rack rows 15C, maintenance schedules requiring server downtime, removal of old servers from the computer room 15, or revamping of a business computing strategy. What is needed, therefore, is a computer room cooling system that can maintain high cooling efficiency with varying heat generation loads during each day, week, or month.

As described in the detailed description of this specification and illustrated in FIGs. 4A to 6, the invention employs a damper 20 of the prior art. FIG. 3 is a block diagram illustrating the damper 20, of the prior art, which including a series of louvers 21 in mechanical connection with a mechanical thermostat 22. The damper 20 is illustrated as viewed from a first side view 20-X along a length of the damper 20. The damper 20 is also illustrated as viewed from a second side view 20-Y along a width of the damper 20. The damper 20 is further illustrated as viewed from a top view 20-Z as viewed from below the damper 20 (as it is mounted in a hot aisle ceiling 15B1 as described in the detailed description section of this specification). Note that, as described in the detailed description section of this specification, the height of a damper 20 (e.g., as seen in the first side view 20-X or second side view 20-Y) can be mounted coplanar with one of the horizontal planes or one of the vertical planes of the computer room 15 when installed according to the invention.

The damper 20 includes a series of louvers 21. The series of louvers 21 is configured to open and close when activated by mechanical connection to a mechanical thermostat 22. When the series of louvers 21 are twisted more open, the louver free area percentage of the damper 20 increases to reduce air resistance across the series of louvers 21, and thereby increase a volume of a variable air flow across the series of louvers 21 (e.g., cubic meters of air per minute) at a given pressure differential across the series of louvers 21. When the series of louvers 21 are twisted closed, the louver free area percentage of the damper 20 decreases to increase air resistance across the series of louvers 21, and thereby decrease the volume of the variable air flow across the series of louvers 21 at the given pressure differential across the series of louvers 21.

After installation and during use, each mechanical thermostat 22 is exposed to an adjacent heated air having an adjacent temperature. The mechanical thermostat 22 is mounted on the side of the damper 20 exposed to the heated air (of the adjacent temperature) that is to be regulated by the opening and closing of the series of louvers 21. The damper 20 can include more than one mechanical thermostat 22. The mechanical thermostat 22 need not be connected to a power source and need not be networked as an internet of things device. The mechanical thermostat 22 is configured to: (1) increase the louver free area percentage of the series of louvers 21 in mechanical connection to the mechanical thermostat 22 when the adjacent temperature for the mechanical thermostat 22 is above a preset threshold temperature for the mechanical thermostat 22; and (2) decrease the louver free area percentage of the series of louvers 21 in mechanical connection to the mechanical thermostat 22 when the adjacent temperature for the mechanical thermostat 22 is below the preset threshold temperature.

Sets of dampers 20 can include a preset thermostat setting that includes: (1) a preset threshold temperature; and (2) a minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers 21. The preset threshold is the adjacent temperature at which the mechanical thermostat 22 will twist open the series of louvers 21 to increase the louver free area percentage which increased the variable air flow across the damper 20. For instance, if the preset threshold temperature is set at 40 degrees Celsius, then the mechanical thermostat 22 will begin opening the series of louvers 21 more when the adjacent temperature of the mechanical thermostat 22 exceeds 40 degrees Celsius, and begin closing the series of louvers 21 more when the adjacent temperature of the mechanical thermostat 22 drops below 40 degrees Celsius. In this manner, each damper 20 can modulate an airflow across the damper 20 and (assuming that a higher air flow reduces the adjacent temperature of the air) maintain a general temperature range within a volume of air that is partially confined by the damper 20. Different sets of dampers 20 can have different preset thermostat settings (e.g., the preset thermostat settings can vary between sets of dampers 20, not every set of dampers 20 requires the same preset thermostat settings). The setting of a minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers 21 can act as a safety feature to avoid excessive heat buildup in a room and/or reduce the probability of suffocation of work staff due to lack of oxygen, a buildup of carbon dioxide, or a build up of other poisonous gases. For instance, if the damper 20 is preset with a 10 percent minimum louver free area percentage, there will always be an airflow across the damper 20 (assuming there is a pressure differential across the damper 20).

SUMMARY

In its most general form, the invention is a computer room cooling system including a plurality of bifurcated heated air return pathways for heated air generated by a plurality of server rack rows operating in a computer room with a false ceiling plenum and a heated air collection duct. A first heated air return pathway routed the heated air from a hot aisle duct into a heated air collection duct. A second heated air return pathway routes the heated air from the hot aisle duct into a voluminous false ceiling plenum before the heated air is routed into the heated air collection duct. Dampers with mechanical thermostats are employed to control airflow between the hot aisle duct and the voluminous false ceiling plenum. The invention can be employed to maintain a minimum delta temperature between the heated air and a first free coolant flow received by an air handling unit from a free cooling tower operating in an outer environment with high humidity.

A primary embodiment of the invention is a computer room cooling system including a plurality of bifurcated heated air return pathways for heated air generated by a plurality of server rack rows operating in a computer room with a false ceiling plenum and a heated air collection duct. Each bifurcated heated air return pathway is associated with one server rack row in the computer room, one hot aisle located adjacent the one server rack row, and one hot aisle duct positioned above a ceiling of the one hot aisle, and further each bifurcated heated air return pathway includes: (i) a first heated air return pathway for the heated air generated by the one server rack row; and (ii) a second heated air return pathway for the heated air generated by the one server rack row. The first heated air return pathway progresses: (1) from the one server rack row associated with the bifurcated heated air return pathway; (2) into the one hot aisle located adjacent the one server rack row; (3) through a plurality of first dampers mounted on the ceiling of the one hot aisle; (4) into the one hot aisle duct positioned above the ceiling of the one hot aisle; and (5) into the heated air collection duct. The second heated air return pathway progresses: (1) from the one server rack row associated with the bifurcated heated air return pathway; (2) into the one hot aisle located adjacent the one server rack row; (3) through a plurality of first dampers mounted on the ceiling of the one hot aisle; (4) into the one hot aisle duct positioned above the ceiling of the one hot aisle; (5) through a plurality of second dampers mounted on sides or atop the one hot aisle duct; (6) into the false ceiling plenum; (7) through a plurality of third dampers mounted between the false ceiling plenum and the heated air collection duct; and (8) into the heated air collection duct.

In the primary embodiment of the invention, each of the first dampers, each of the second dampers, and each of the third dampers include at least one mechanical thermostat in mechanical connection to a series of louvers. Each mechanical thermostat is exposed to an adjacent heated air having an adjacent temperature, the mechanical thermostat configured to increase or decrease a louver free area percentage of the series of louvers in mechanical connection to the mechanical thermostat in response to each change in the adjacent temperature such that: (1) the mechanical thermostat is configured to increase the louver free area percentage of the series of louvers in mechanical connection to the mechanical thermostat when the adjacent temperature for the mechanical thermostat is above a preset threshold temperature for the mechanical thermostat; and (2) the mechanical thermostat is configured to decrease the louver free area percentage of the series of louvers in mechanical connection to the mechanical thermostat when the adjacent temperature for the mechanical thermostat is below the preset threshold temperature. Each first damper associated with each hot aisle is configured to: (i) control a first variable airflow of the heated air from the hot aisle into the hot aisle duct associated with the hot aisle; and (ii) preset a first thermostat setting. The first thermostat setting includes: (1) a first threshold temperature for the preset threshold temperature for the mechanical thermostat of the first damper; and (2) a first minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers of the first damper. Each second damper associated with each hot aisle duct is configured to: (i) control a second variable airflow of the heated air from the hot aisle duct into the false ceiling plenum; and (ii) preset a second thermostat setting. The second thermostat setting includes: (1) a second threshold temperature for the preset threshold temperature for the mechanical thermostat of the second damper; and (2) a second minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers of the second damper. Each third damper is configured to: (i) control a third variable airflow of the heated air from the false ceiling plenum to the heated air collection duct; and (ii) preset a third thermostat setting. The third thermostat setting includes: (1) a third threshold temperature for the preset threshold temperature for the mechanical thermostat of the third damper; and (2) a third minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers of the third damper.

In an alternative embodiment of the primary embodiment of the invention, each hot aisle duct includes: (i) an HAD top surface of the hot aisle duct along a first horizontal plane, the first horizontal plane co-planar with an FCP top surface of the false ceiling plenum; and (ii) an HAD bottom surface of the hot aisle duct along a second horizontal plane. The second horizontal plane is: (1) co-planar with the hot aisle ceiling associated with the hot aisle duct; and (2) coplanar with an FCP bottom surface of the false ceiling plenum. Each of the first dampers of each hot aisle duct is mounted: (i) in the second horizontal plane; and (ii) between the hot aisle ceiling and the HAD bottom surface of the hot aisle duct. Each of the second dampers of each hot aisle duct is mounted: (i) in at least one of a first vertical plane along a first vertical side of the hot aisle duct and a second vertical plane along a second vertical side of the hot aisle duct; and (ii) between the first vertical side or the second vertical side of the hot aisle duct and the false ceiling plenum.

In an alternative embodiment of the primary embodiment of the invention, each hot aisle duct includes: (i) an HAD top surface of the hot aisle duct along a second horizontal plane, the second horizontal plane co-planar with an FCP bottom surface of the false ceiling plenum; and (ii) an HAD bottom surface of the hot aisle duct along a second alternative horizontal plane. The second alternative horizontal plane is: (1) co-planar with the hot aisle ceiling associated with the hot aisle duct; and (2) located in parallel and between the second horizontal plane and a third horizontal plan that is co-planar with a floor area of the hot aisle associated with the hot aisle duct. Each of the first dampers of each hot aisle duct is mounted: (i) in the second alternative horizontal plane; and (ii) between the hot aisle ceiling and the HAD bottom surface of the hot aisle duct. Each of the second dampers of each hot aisle duct is mounted: (i) in the second horizontal plane; and (ii) between the HAD top surface of the hot aisle duct and the FCP bottom surface of the false ceiling plenum. A secondary embodiment of the invention further includes, in addition to the technical elements of the primary embodiment of the invention: (a) for each server rack row, at least one cooled air inlet into a cold aisle associated with the server rack row; and (b) an air handling unit (AHU). The AHU is in fluid connection with: (i) the heated air collection duct; and (ii) the at least one cooled air inlet of each cold aisle. The AHU is configured to receive the heated air via the heated air collection duct to create cooled air. The at least one cooled air inlet is configured to receive the cooled air from the AHU.

In an alternative embodiment of the secondary embodiment of the invention, the system further includes a free cooling tower and a chiller. The AHU includes a free cooling coil configured to receive a first free coolant flow from the free cooling tower. The AHU includes a trim cooling coil configured to receive a trim coolant flow from an evaporator passage of the chiller. In this embodiment, the chiller may include a condenser passage to receive a second free coolant flow from the free cooling tower. In this embodiment, the free cooling tower may receive ambient air from an outer environment in an ambient temperature range of 25 to 32 degrees Celsius.

In an alternative embodiment of the secondary embodiment of the invention: (a) the AHU further includes an AHU controller and a variable speed fan; and (b) each bifurcated heated air return pathway includes a plurality of networked temperature sensors. Each networked temperature sensor is configured to: (i) detect a series of current local temperature; and (ii) transmit the series of current local temperature to the AHU controller. The AHU controller is configured to: (i) reduce a speed of the variable speed fan of the AHU when at least one of the current local temperatures received from one of the networked temperature sensors is below a heated air threshold temperature; and (ii) increase the speed of the variable speed fan of the AHU when at least one of the current local temperatures received from one of the networked temperature sensors is above the heated air threshold temperature. In this embodiment, the heated air threshold temperature may be selected from a heated air threshold temperature range of 38 to 42 degrees Celsius.

The invention is directed toward creating a computer room cooling system that provides maximum energy efficiency for data computing centers located in the tropics or otherwise high humidity environments. The primary benefit of the invention is accomplished by maintaining a high delta temperature between: (i) the temperature of the heated air received from the heated air collection duct; and (ii) the free tower coolant received from the free cooling tower.

The first dampers act to regulate a first variable airflow between the hot aisles and the hot aisle duct. The first dampers allow the heated air temperature in the hot aisles to reach a first threshold temperature before a substantial portion of this heated air is permitted into the hot aisle duct.

The second dampers have a lower minimum louver free air percentage than the first dampers. The first dampers preferably have a minimum louver free air percentage in a range of 8 to 12 percent. The second dampers preferably have a minimum louver free air percentage in a range of 0 to 3 percent. The second threshold temperature of the mechanical thermostats of the second dampers can also be set at a preset thermostat temperature that is higher than the first threshold temperature of the mechanical thermostats of the first dampers.

Therefore, if there is a low rate of heat generation by the server rack row associated with the hot aisle duct, the heated air generated by that server rack row is limited primarily to the volume of the hot aisle and the first volume of the hot aisle duct. Airflow from this low heat generation server rack row can progress to the heated air collection duct via the first heated air return pathway.

On the other hand, if there is a high rate of heat generation in a particular server rack row, the extra heat can flow into the second volume of the false ceiling plenum. The false ceiling plenum, thereby, acts as a heat reservoir for the cooling system, permitting for fluctuations in heat generation between the server rack rows of the computer room. The third dampers only permit heated air in the false ceiling plenum to enter the heated air collection duct (for completion of the second heated air return pathway) if the mechanical thermostats in these third dampers meet a third threshold temperature. The dampers thus enable dynamic adjustment to the total heated air reservoir volume for the computer room cooling system.

The AHU also includes a variable speed fan that can slow down to reduce the volume of heated air removed from the computer room during times of low heat generation, or increase in speed during times of high heat generation. Together, the dampers creating the bifurcated heated air return pathway and the variable speed fan of the AHU provide a computer room cooling system that can maintain a more consistent high delta temperature between the temperature of the heated air drawn into the AHU and the temperature of the free tower coolant. This high delta temperature increases the efficiency and benefit of the free coolant tower and thereby decreases the reliance on the trim cooling coil to cool the heated air to reduce energy consumption by the chiller.

Electronics mounted in the server rack rows are protected from excessive temperatures (e.g., temperatures above 40 degrees Celsius) because the mechanical thermostat damper design prevents any single point of failure. If one of the first dampers fails, the heated air will escape the hot aisle through other first dampers that are in functioning order. Also, the first dampers have preferably a first minimum louver free area percentage in the range of 8 to 12 percent, permitting a minimum heated air flow out of the hot aisles. The mechanical thermostats also do not rely on electrical power or network communication. Thus, if there is a power outage or network failure, the dampers are not affected.

The dampers are also easy to install in buildings that are not custom designed to function as a data computing center. E.g., the existing perforated ceiling tiles in the hot aisle ceiling can be replaced with first dampers. E.g., the existing false ceiling plenum can be used for the second heated air return pathway.

The invention also improves the performance of a dual coil cooling system, of the prior art. The invention produces a higher delta temperature, such that the higher temperature heated air passing through the air handling unit is first cooled by a first free coolant flow (from the free coiling tower) to a greater degree than if the heated air was of a lower temperature.

Together, all the technical aspects of the invention work together to maintain a high delta temperature and thereby maximize the efficiency of a free cooling tower in tropical or otherwise high humidity environments. At the same time, the invention prevents overheating of electronics in the server racks and provides flexibility for computer room operations. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure are described herein with reference to the drawings in which:

FIG. 1 is a block diagram illustrating a heated air return pathway, of the prior art, through a computer room.

FIG. 2 is a block diagram illustrating a dual coil cooling system, of the prior art, for a computer room employing a free cooling tower and a chiller.

FIG. 3 is a block diagram illustrating a damper, of the prior art, including a series of louvers in mechanical connection with a mechanical thermostat.

FIGs. 4A and 4B are block diagrams illustrating, in a vertical plane side view of a computer room, alternative bifurcated heated air return pathway designs for a hot aisle duct, in alternative embodiments of the invention.

FIG. 5 is a block diagram illustrating, in a horizontal plane top view of a computer room, a bifurcated heated air return pathway design for a hot aisle duct in an embodiment of the invention.

FIG. 6 is a block diagram illustrating, in a simplified format, a first heated air return pathway and a second heated air return pathway for a computer room in an embodiment of the invention.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. The illustrative embodiments described in the detailed description, drawings and claims are not meant to be limiting. Other embodiments can be utilized, and other changes can be made, without departing from the spirit or scope of the subject matter presented herein. Unless specified otherwise, the terms “comprising,” “comprise,” “including” and “include” used herein, and grammatical variants thereof, are intended to represent “open” or “inclusive” language such that they include recited elements but also permit inclusion of additional, unrecited elements.

A described in this specification, the server racks rows can house various computing devices generating heated air, such as servers and data storage devices. The terms “plane” and “coplanar” are intended to describe cross-sectional volumes (either horizontal or vertical) within the computer room. These cross-sectional volumes can include, for instance a height of a damper, a height of a ceiling tile or flooring tile. E.g., “plane” and “co-planar are not meant to designate an ideal plane possessing no volume.

As used in this specification, the term “damper” is not meant to be limited to any specific form factor. Dampers used in the invention may be off-the-shelf purchased dampers or customized dampers of various dimensions. However, to ensure no single point of failure, the term “damper” is meant to describe discrete, separate devices, wherein each damper include its own mechanical thermostat and series of louvers. In this manner, if one or more dampers fail, there is a low likelihood of damage to the electronics mounted in the server rack rows, as the remaining dampers remain functional. The dampers also have the benefit of enabling a fast upgrade methodology for prior art computer rooms (e.g., by replacing the perforated ceiling tiles of the hot aisle ceilings with first dampers). For convenience, each of the items referenced in the figures by number are listed below.

No. Items

10 dual coil cooling system

11 free cooling tower

12 ambient air

13 chiller

13A condenser passage

13B evaporator passage

14 air handling unit (AHU)

14A free cooling coil

14B trim cooling coil

14C heated air collection duct (HACD)

14D variable speed fan

15 computer room

15A cold aisle

15A1 cold aisle ceiling

15B hot aisle

15B1 hot aisle ceiling

15C server rack row

15D1 cooled air inlet

15Dl-a raised floor plenum inlet

15Dl-b fan wall inlet

15D2 heated air outlet

16 false ceiling plenum (FCP)

17 raised floor plenum

18 hot aisle duct (HAD)

20 damper

20A first dampers

20A1 first variable outflow

20B second dampers

20B1 second variable outflow

20C third dampers 20C2 third variable outflow

20-X side view of damper

20-Y end view of damper

20-Z bottom view of damper

21 first horizontal plane

21 series of louvers

22 mechanical thermostat

22-a second horizontal plane

22-b second alternative horizontal plane

23 third horizontal plane

24 fourth horizontal plane

31 first vertical plane

32 second vertical plane

33 third vertical plane

34 fourth vertical plane

61 first heated air return pathway

62 second heated air return pathway

FIGs. 1 to 3 have been described in the background section of this specification.

FIGs. 4A and 4B are block diagrams illustrating, in a vertical plane side view of a computer room 15, alternative bifurcated heated air return pathway designs for a hot aisle duct 18, in alternative embodiments of the invention. As in FIGs. 1 and 2, the computer rooms 15 depicted in FIGs. 4A and 4B include a cold aisle 15A and a hot aisle 15B separated by a server rack row 15C. The cold aisle 15A receives cooled air via a raised floor plenum inlet 15Dl-a and/or a fan wall inlet 15Dl-b for the cooled air inlet 15D1. The cooled air in the cold aisle 15A is drawn into the hot aisle 15B through and heated by electronics (e.g., servers and/or data storage devices) mounted in the server rack row 15C. As in FIG. 2, to assist in the description of the items in the figures, FIGs. 4A and 4B identify several planar interfaces. The terms “plane” and “co-planar”, as used in this description, are intended to describe cross-sectional volumes (either horizontal or vertical) within the computer room 15, rather than ideal planes having no volume. A first horizontal plane 21 is co-planar with an FCP top surface of the false ceiling plenum 16. A second horizontal plane 22-a is coplanar with the FCP bottom surface of the false ceiling plenum 16 and the cold aisle ceiling 15A1 of the cold aisle 15A and the hot aisle ceiling 15B1 of the hot aisle 15B. A third horizontal plane 23 is co-planar with a top surface of a raised floor plenum 17. A fourth horizontal plane 24 is co-planar with a bottom surface of the raised floor plenum 17. A first vertical plane 31 is co-planar with a first side of the hot aisle 15B. A second vertical plane 32 is co-planar with a second side of the hot aisle 15B. A third vertical plane 33 is co-planar with one side edge of the false ceiling plenum 16.

In FIGs. 4A and 4B, the heated air in the hot aisle 15B is drawn into a hot aisle duct 18 through first dampers 20A (see arrows 20A1) mounted in the hot aisle ceiling 15B1 along the second horizontal plane 22-a, replacing the perforated ceiling tiles of the prior art design detailed in FIG. 1. The heated air can return to an air handling unit 14 (not shown) along the length of the hot aisle duct 18 in a first heated air return pathway 61 (see also FIG. 5 for a top view of the computer room 15). The heated air can also return to the AHU 14 (not shown) in a second heated air return pathway 62: starting from the hot aisle duct 18 after passage through second dampers 20B (mounted in the first vertical plane 31, see arrows 20B1), into the false ceiling plenum 16, through third dampers 20C (mounted in the third vertical plane 33, see arrows 20C1), into a heated air collection duct (HACD) 14C, and lastly into a heated air outlet 15D2 (not shown). The cold aisle 15A receives cooled air via a raised floor plenum inlet 15Dl-a and/or a fan wall inlet 15Dl-b for the cooled air inlet 15D1.

In the FIG. 4A embodiment of the invention, the hot aisle duct 18 includes an HAD top surface of the hot aisle duct 18 along the first horizontal plane and an HAD bottom surface of the hot aisle duct 18 along a second horizontal plane 22-a. The second horizontal plane 22-a is coplanar with the hot aisle ceiling 15B1 associated with the hot aisle duct 18. E.g., when retrofitting an industrial office location to use the FIG. 4A embodiment of the invention, the hot aisle ducts 18 are mounted within the existing false ceiling plenum 16. Each of the first dampers 20A of the hot aisle duct 18 is mounted in the second horizontal plane 22-a between the hot aisle ceiling 15B1 and the HAD bottom surface of the hot aisle duct 18. Second dampers 20B are mounted in a first vertical side of the hot aisle duct 18 in the first vertical plane 31, between the first vertical side of the hot aisle duct 18 and a first portion of the false ceiling plenum 16.

While not shown in FIG. 4A (see top view of this embodiment depicted in FIG. 5), the second dampers 20B of the hot aisle duct 18 can also be mounted in the second vertical plane 32 along a second vertical side of the hot aisle duct 18. These second dampers 20B would be mounted between the second vertical side of the hot aisle duct 18 and a second portion of the false ceiling plenum 16 (not shown in FIG. 4A, see top view of this embodiment depicted in FIG. 5).

Third dampers 20C are mounted in a third vertical plane 33 between the false ceiling plenum 16 and the heated air collection duct (HACD) 14C.

In the FIG. 4B embodiment of the invention, the hot aisle duct 18 includes an HAD top surface of the hot aisle duct 18 along the second horizontal plane 22-a and an HAD bottom surface of the hot aisle duct 18 along a second alternative horizontal plane 22-b. The second alternative horizontal plane 22-b is co-planar with the hot aisle ceiling 15B1 associated with the hot aisle duct 18. Each of the first dampers 20A of the hot aisle duct 18 is mounted in the second alternative horizontal plane 22-b between the hot aisle ceiling 15B1 and the HAD bottom surface of the hot aisle duct 18. E.g., in the FIG. 4B embodiment of the invention, the hot aisle ceiling 15B1 is lowered such that the hot aisle duct 18 is mounted below the false ceiling plenum 16. Each of the second dampers 20B are mounted in the second horizontal plane 22-a between the HAD top surface of the hot aisle duct 18 and the bottom surface of the false ceiling plenum 16.

FIG. 5 is a block diagram illustrating, in a horizontal plane top view of a computer room 15, a bifurcated heated air return pathway design for a hot aisle duct 18 in the embodiment of the invention depicted in FIG. 4A.

As in FIGs. 2, 4A, and 4B, to assist in the description of the items in the figures, FIG. 5 identifies several planar interfaces. The terms “plane” and “co-planar”, as used in this description, are intended to describe cross-sectional volumes within the computer room 15, rather than ideal planes having no volume. A first vertical plane 31 is co-planar with a first side of the hot aisle 15B. A second vertical plane 32 is co-planar with a second side of the hot aisle 15B. A third vertical plane 33 is co-planar with one side edge of the false ceiling plenum 16. FIG. 5 introduces a fourth vertical plane 34 along the right side of the figure.

As in FIGs. 4A and 4B , in FIG. 5 the heated air in the hot aisle 15B is drawn into a hot aisle duct 18 through via first dampers 20A (not shown, see FIG. 4A and arrows 20A1). The heated air can return to an AHU 14 (not shown) along the length of the hot aisle duct 18 in a first heated air return pathway 61. The heated air can also return to the AHU 14 (not shown) in a second heated air return pathway 62 from the hot aisle duct 18 after passage through second dampers 20B (mounted in the first vertical plane 31, see arrows 20B1), into the first portion of the false ceiling plenum 16, through third dampers 20C (mounted in the third vertical plane 33 and the fourth vertical plane 34, see arrows 20C1), into a heated air collection duct (HACD) 14C, and a heated air outlet 15D2.

As in FIG. 4A. the second dampers 20B in FIG. 5 are mounted in a first vertical side of the hot aisle duct 18 in the first vertical plane 31. The second dampers 20B of the hot aisle duct 18 are also illustrated in FIG. 5 as mounted in the second vertical plane 32 along a second vertical side of the hot aisle duct 18. These second dampers 20B are mounted between the second vertical side of the hot aisle duct 18 and a second portion of the false ceiling plenum 16.

Third dampers 20C are mounted in the third vertical plane 33 and the fourth plane between the false ceiling plenum 16 and the heated air collection duct (HACD) 14C.

Note that FIG. 5 is not drawn to scale. In particular, preferably, the first volume of each hot aisle duct 18 is less than 25 percent of the second volume of the false ceiling plenum 16.

FIG. 6 is a block diagram 6-00 illustrating, in a simplified format, a first heated air return pathway 61 and a second heated air return pathway 62 for a computer room 15 in an embodiment of the invention. The first heated air return pathway 61 proceeds from the server rack rows 15C, into the hot aisle 15B, through the first dampers 20A (see arrows 20A1), into the hot aisle duct 18, and into the heated air collection duct (HACD) 14C. The second heated air return pathway 62 proceeds from the server rack rows 15C, into the hot aisle 15B, through the first dampers 20A (see arrows 20A1), into the hot aisle duct 18, through the second dampers 20B (see arrows 20B1), into the false ceiling plenum 16, through the third dampers 20C (see arrows 20C1), and into the heated air collection duct (HACD) 14C. The heated air from the first heated air return pathway 61 and the second heated air return pathway is directed into the air handling unit (AHU) 14 via the heated air outlet 15D2.

The heated air collected from the first heated air return pathway 61 and the second heated air return pathway 62 is directed into the AHU 14. The AHU 14 includes a variable speed fan 14D, a free cooling coil 14A, and a trim cooling coil 14B. Cooled air from the AHU 14 is directed into the cold aisle 15A via a raised floor plenum inlet 15Dl-a and/or a fan wall inlet 15Dl-b.

In its most general form, the invention is a computer room cooling system including a plurality of bifurcated heated air return pathways for heated air generated by a plurality of server rack rows 15C operating in a computer room 15 with a false ceiling plenum 16 and a heated air collection duct (HACD) 14C. A first heated air return pathway 61 routed the heated air from a hot aisle duct 18 into a heated air collection duct (HACD) 14C. A second heated air return pathway 62 routes the heated air from the hot aisle duct 18 into a voluminous false ceiling plenum 16 before the heated air is routed into the heated air collection duct (HACD) 14C. Dampers 20 with mechanical thermostats 22 are employed to control airflow between the hot aisle duct 18 and the voluminous false ceiling plenum 16. The invention can be employed to maintain a minimum delta temperature between the heated air and a first free coolant flow received by an air handling unit (AHU) 14 from a free cooling tower 11 operating in an outer environment with high humidity.

A primary embodiment of the invention is a computer room cooling system including a plurality of bifurcated heated air return pathways for heated air generated by a plurality of server rack rows 15C operating in a computer room 15 with a false ceiling plenum 16 and a heated air collection duct (HACD) 14C. Each bifurcated heated air return pathway is associated with one server rack row 15C in the computer room 15, one hot aisle 15B located adjacent the one server rack row 15C, and one hot aisle duct 18 positioned above a ceiling of the one hot aisle 15B, and further each bifurcated heated air return pathway includes: (i) a first heated air return pathway 61 for the heated air generated by the one server rack row 15C; and (ii) a second heated air return pathway 62 for the heated air generated by the one server rack row 15C. The first heated air return pathway 61 progresses: (1) from the one server rack row 15C associated with the bifurcated heated air return pathway; (2) into the one hot aisle 15B located adjacent the one server rack row 15C; (3) through a plurality of first dampers 20A (see arrows 20A1) mounted on the ceiling of the one hot aisle 15B; (4) into the one hot aisle duct 18 positioned above the ceiling of the one hot aisle 15B; and (5) into the heated air collection duct (HACD) 14C. The second heated air return pathway 62 progresses: (1) from the one server rack row 15C associated with the bifurcated heated air return pathway; (2) into the one hot aisle 15B located adjacent the one server rack row 15C; (3) through a plurality of first dampers 20A (see arrows 20A1) mounted on the ceiling of the one hot aisle 15B; (4) into the one hot aisle duct 18 positioned above the ceiling of the one hot aisle 15B; (5) through a plurality of second dampers 20B (see arrows 20B1) mounted on sides or atop the one hot aisle duct 18; (6) into the false ceiling plenum 16; (7) through a plurality of third dampers 20C (see arrows 20C1) mounted between the false ceiling plenum 16 and the heated air collection duct (HACD) 14C; and (8) into the heated air collection duct (HACD) 14C.

In the primary embodiment of the invention, each of the first dampers 20A, each of the second dampers 20B, and each of the third dampers 20C include at least one mechanical thermostat 22 in mechanical connection to a series of louvers 21. Each mechanical thermostat 22 is exposed to an adjacent heated air having an adjacent temperature, the mechanical thermostat 22 configured to increase or decrease a louver free area percentage of the series of louvers 21 in mechanical connection to the mechanical thermostat 22 in response to each change in the adjacent temperature such that: (1) the mechanical thermostat 22 is configured to increase the louver free area percentage of the series of louvers 21 in mechanical connection to the mechanical thermostat 22 when the adjacent temperature for the mechanical thermostat 22 is above a preset threshold temperature for the mechanical thermostat 22; and (2) the mechanical thermostat 22 is configured to decrease the louver free area percentage of the series of louvers 21 in mechanical connection to the mechanical thermostat 22 when the adjacent temperature for the mechanical thermostat 22 is below the preset threshold temperature. Each first damper 20A associated with each hot aisle 15B is configured to: (i) control a first variable airflow of the heated air from the hot aisle 15B into the hot aisle duct 18 associated with the hot aisle 15B; and (ii) preset a first thermostat setting. The first thermostat setting includes: (1) a first threshold temperature for the preset threshold temperature for the mechanical thermostat 22 of the first damper 20A; and (2) a first minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers 21 of the first damper 20A. Each second damper 20B associated with each hot aisle duct 18 is configured to: (i) control a second variable airflow of the heated air from the hot aisle duct 18 into the false ceiling plenum 16; and (ii) preset a second thermostat setting. The second thermostat setting includes: (1) a second threshold temperature for the preset threshold temperature for the mechanical thermostat 22 of the second damper 20B; and (2) a second minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers 21 of the second damper 20B. Each third damper 20C is configured to: (i) control a third variable airflow of the heated air from the false ceiling plenum 16 to the heated air collection duct (HACD) 14C; and (ii) preset a third thermostat setting. The third thermostat setting includes: (1) a third threshold temperature for the preset threshold temperature for the mechanical thermostat 22 of the third damper 20C; and (2) a third minimum louver free area percentage for the preset minimum louver free area percentage for the series of louvers 21 of the third damper 20C.

In an alternative embodiment of the primary embodiment of the invention, each hot aisle duct 18 includes: (i) an HAD top surface of the hot aisle duct 18 along a first horizontal plane 21, the first horizontal plane 21 co-planar with an FCP top surface of the false ceiling plenum 16; and (ii) an HAD bottom surface of the hot aisle duct 18 along a second horizontal plane 22-a. The second horizontal plane 22-a is: (1) co-planar with the hot aisle ceiling 15B1 associated with the hot aisle duct 18; and (2) co-planar with an FCP bottom surface of the false ceiling plenum 16. Each of the first dampers 20A of each hot aisle duct 18 is mounted: (i) in the second horizontal plane 22-a; and (ii) between the hot aisle ceiling 15B1 and the HAD bottom surface of the hot aisle duct 18. Each of the second dampers 20B of each hot aisle duct 18 is mounted: (i) in at least one of a first vertical plane 31 along a first vertical side of the hot aisle duct 18 and a second vertical plane 32 along a second vertical side of the hot aisle duct 18; and (ii) between the first vertical side or the second vertical side of the hot aisle duct 18 and the false ceiling plenum 16.

In an alternative embodiment of the primary embodiment of the invention, each hot aisle duct 18 includes: (i) an HAD top surface of the hot aisle duct 18 along a second horizontal plane 22-a, the second horizontal plane 22-a co-planar with an FCP bottom surface of the false ceiling plenum 16; and (ii) an HAD bottom surface of the hot aisle duct 18 along a second alternative horizontal plane 22-b. The second alternative horizontal plane 22-b is: (1) co-planar with the hot aisle ceiling 15B1 associated with the hot aisle duct 18; and (2) located in parallel and between the second horizontal plane 22-a and a third horizontal plan that is co-planar with a floor area of the hot aisle 15B associated with the hot aisle duct 18. Each of the first dampers 20A of each hot aisle duct 18 is mounted: (i) in the second alternative horizontal plane 22-b; and (ii) between the hot aisle ceiling 15B1 and the HAD bottom surface of the hot aisle duct 18. Each of the second dampers 20B of each hot aisle duct 18 is mounted: (i) in the second horizontal plane 22-a; and (ii) between the HAD top surface of the hot aisle duct 18 and the FCP bottom surface of the false ceiling plenum 16.

In an alternative embodiment of the primary embodiment of the invention, the third dampers 20C are mounted: (a) in a third vertical plane 33 along at least one edge side of the false ceiling plenum 16; and (b) between the false ceiling plenum 16 and the heated air collection duct (HACD) 14C.

In an alternative embodiment of the primary embodiment of the invention, a first volume of each hot aisle duct 18 is less than 25 percent of a second volume of the false ceiling plenum 16.

In an alternative embodiment of the primary embodiment of the invention: (a) the first threshold temperature is selected from a first threshold temperature range from 35 to 39 degrees Celsius; and (b) the second threshold temperature is selected from a second threshold temperature range from 37 to 41 degrees Celsius.

In an alternative embodiment of the primary embodiment of the invention, the first minimum louver free area percentage is in a first free area range of 8 to 12 percent.

In an alternative embodiment of the primary embodiment of the invention, the second minimum louver free area percentage is in a second free area range of 0 to 3 percent.

In an alternative embodiment of the primary embodiment of the invention: (a) a maximum louver free area percentage of each of the first dampers 20A, each of the second dampers 20B, and each of the third dampers 20C is in a maximum free area range of 25 to 35 percent; (b) each of the mechanical thermostats 22 has an adjacent temperature response time of less than 15 seconds; and (c) each of the mechanical thermostats 22 has an optimized temperature response range of 30 to 45 degrees Celsius.

In an alternative embodiment of the primary embodiment of the invention, the at least one mechanical thermostat 22 associated with each series of louvers 21 is mounted on an upstream side of the series of louvers 21.

A secondary embodiment of the invention further includes, in addition to the technical elements of the primary embodiment of the invention: (a) for each server rack row 15C, at least one cooled air inlet 15D1 into a cold aisle 15 A associated with the server rack row 15C; and (b) an air handling unit (AHU) 14. The AHU 14 is in fluid connection with: (i) the heated air collection duct (HACD) 14C; and (ii) the at least one cooled air inlet 15D1 of each cold aisle 15A. The AHU 14 is configured to receive the heated air via the heated air collection duct (HACD) 14C to create cooled air. The at least one cooled air inlet 15D1 is configured to receive the cooled air from the AHU 14.

In an alternative embodiment of the secondary embodiment of the invention: (a) the cooled air received into each cold aisle 15A from the AHU 14 is in a cooled air temperature range of 23 to 27 degrees Celsius; and (b) the heated air received by the AHU 14 via the heated air collection duct (HACD) 14C is in a heated air temperature range of 38 to 42 degrees Celsius.

In an alternative embodiment of the secondary embodiment of the invention, the system further includes a free cooling tower 11 and a chiller 13. The AHU 14 includes a free cooling coil 14A configured to receive a first free coolant flow from the free cooling tower 11. The AHU 14 includes a trim cooling coil 14B configured to receive a trim coolant flow from an evaporator passage 13B of the chiller 13. In this embodiment, the chiller 13 may include a condenser passage 13A to receive a second free coolant flow from the free cooling tower 11. In this embodiment, the free cooling tower 11 may receive ambient air 12 from an outer environment in an ambient temperature range of 25 to 32 degrees Celsius.

In an alternative embodiment of the secondary embodiment of the invention: (a) the AHU 14 further includes an AHU controller and a variable speed fan 14D; and (b) each bifurcated heated air return pathway includes a plurality of networked temperature sensors. Each networked temperature sensor is configured to: (i) detect a series of current local temperature; and (ii) transmit the series of current local temperature to the AHU controller. The AHU controller is configured to: (i) reduce a speed of the variable speed fan 14D of the AHU 14 when at least one of the current local temperatures received from one of the networked temperature sensors is below a heated air threshold temperature; and (ii) increase the speed of the variable speed fan 14D of the AHU 14 when at least one of the current local temperatures received from one of the networked temperature sensors is above the heated air threshold temperature. In this embodiment, the heated air threshold temperature may be selected from a heated air threshold temperature range of 38 to 42 degrees Celsius.

While various aspects and embodiments have been disclosed herein, it will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit of the invention being indicated by the appended claims.