Abstract:
An enclosed air conditioning unit includes a filter section and a cooling section through which intake air passes before being discharged into a space within a building. The orientation of the filter section and cooling section is substantially vertical, and the airflow path through the filter section and the cooling section is substantially horizontal, resulting in reduced face velocities across these components, thereby increasing filtration efficiency and cooling effectiveness, while allowing the physical size and configuration of the air conditioning unit&#39;s enclosure to be the same as or smaller than the enclosures for conventional air conditioning units having comparable or lower performance.

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates in general to air conditioning units for controlling environmental conditions within building spaces, including air conditioning units for computer rooms, data centers (server rooms), and other building spaces intended for uses having special environmental control requirements. The disclosure relates in particular to air conditioning units adapted for installation within the building spaces served by the units. 
     BACKGROUND 
     Computer rooms and other building spaces intended for specialized uses often require precise control and regulation of environmental conditions such as temperature and humidity in order to ensure proper operation of equipment (such as but not limited to computers) installed in such building spaces. Cooling requirements for computer rooms are typically much greater and more stringent than for most building spaces due to the need to dissipate heat generated by the computer equipment operating in the computer rooms. Humidity control requirements are typically stringent as well, as excessive moisture in the air in a computer room can cause operational and maintenance problems with the computer equipment. 
     Accordingly, computer rooms commonly are provided with specialized air conditioning (A/C) systems for controlling and regulating temperature and humidity. It has been common in the past for computer room A/C systems to be located outside the computer room and even outside the building housing the computer room, due to the physical size of the equipment needed to meet the A/C requirements for the computer room in question. In recent years, however, computer room air conditioning units (or “CRAC units”) have been developed that are sufficiently compact for installation within a computer room without greatly increasing the required floor area or height of the computer room. Examples of such CRAC units include chilled water or DX (direct expansion) A/C units manufactured by the Liebert® Corporation. 
     Conventional CRAC units commonly utilize banked (i.e., angularly-oriented) cooling coils specially constructed for use in CRAC unit and arrayed in an A-frame or V-frame configuration within the unit. Airflow typically enters the unit vertically through the top or bottom of the unit and proceeds in a straight, vertical path through the filters and coils. In CRAC units of this type, the air velocity through the filters (also referred to herein as the “face velocity”) is comparatively high, which results in reduced filter performance. 
     Another drawback of known CRAC units is that they cannot be readily adapted to use direct evaporative cooling systems using saturated evaporative media pads without increasing the size of the units so much that their use within a computer room becomes unviable or undesirable. Direct evaporative cooling systems using saturated evaporative media pads rely on gravity to allow water sprayed on top of the unit to trickle down, saturating the pad through which the airstream passing through the CRAC unit travels. Some of the water in the evaporative pad evaporates into the airstream, adiabatically cooling it. Water is collected in a sump located beneath the evaporative pad. However, this type of direct evaporative cooling system cannot be used in conventional CRAC units using a conventional vertical airflow pattern, because the evaporative media pads would have to be oriented horizontally, such that water would not be able to drain from the media by gravity into a drain pan. Moreover, the requirement for the evaporative media to be horizontally oriented for use in a CRAC unit having a vertical airflow pattern would increase the size of the unit and the floor area it requires. 
     For the foregoing reasons, there is a need for CRAC units characterized by lower face velocities (and therefore better filter performance and efficiency) than conventional CRAC units, without increasing the physical size of the units significantly or at all. In addition, there is a need for CRAC units that can be adapted to use direct evaporative cooling media, without significant effect on the physical size of the units. 
     BRIEF SUMMARY 
     In general terms, the present disclosure teaches an enclosed air conditioning unit comprising a filter section and a cooling section in which the airflow path through the filter section and cooling section is substantially horizontal, with the physical size and configuration of the unit&#39;s cabinet or enclosure being essentially the same as (or smaller than) the cabinets for conventional air conditioning units having comparable or lower performance capabilities. 
     In a first aspect, the present disclosure teaches an air conditioning unit comprising an enclosure having a first wall, a second wall opposite the first wall, and a primary air intake in an upper region of the enclosure; and an air treatment component assembly mounted within the enclosure so as to define a first chamber between the component assembly and the enclosure&#39;s first wall and a second chamber between the component assembly and the enclosure&#39;s second wall. Air entering the primary air intake from outside the enclosure will flow, in sequence, downward within the first chamber, horizontally through the component assembly into the second chamber, and downward within the second chamber toward a discharge outlet in a lower region of the enclosure. 
     In one particular embodiment in accordance with the above-described first aspect, the air conditioning unit comprises an enclosure (cabinet) having a first wall, a second wall opposite the first wall, and a primary air intake in an upper region of the enclosure; plus an air treatment component assembly including a generally flat filter section and a generally flat cooling section. The filter section and cooling section are installed in parallel juxtaposition, and oriented vertically within the enclosure, so as to define a first chamber between the filter section and the enclosure&#39;s first wall, and a second chamber between the cooling section and the enclosure&#39;s second wall. Air entering the primary air intake from outside the enclosure will flow, in sequence, downward within the first chamber, horizontally through the filter section and the cooling section into the second chamber, and downward within the second chamber toward a discharge outlet in a lower region of the enclosure. Optionally, the air conditioning unit may include a bypass air intake through which air from outside the unit can flow downward into the second chamber. Embodiments that have a bypass air intake preferably will also have an intake damper for regulating the flow of air into the second chamber. 
     In a second aspect, the present disclosure teaches an air conditioning unit comprising an enclosure having a first wall, a second wall opposite the first wall, and a primary air intake in a lower region of the enclosure; and an air treatment component assembly mounted within the enclosure so as to define a first chamber between the component assembly and the enclosure&#39;s first wall and a second chamber between the component assembly and the enclosure&#39;s second wall. Air entering the primary air intake from outside the enclosure will flow, in sequence, upward within the first chamber, horizontally through the component assembly into the second chamber, and upward within the second chamber toward a discharge outlet in an upper region of the enclosure. 
     In one particular embodiment in accordance with the above-described second aspect, the air conditioning unit comprises an enclosure (cabinet) having a first wall, a second wall opposite the first wall, and a primary air intake in a lower region of the enclosure; plus an air treatment component assembly including a generally flat filter section and a generally flat cooling section. The filter section and cooling section are in parallel juxtaposition and oriented vertically within the enclosure, so as to define a first chamber between the filter section and the enclosure&#39;s first wall, and a second chamber between the cooling section and the enclosure&#39;s second wall. Air entering the primary air intake from outside the enclosure will flow, in sequence, upward within the first chamber, horizontally through the filter section and the cooling section into the second chamber, and upward within the second chamber toward a discharge outlet in an upper region of the enclosure. Optionally, the air conditioning unit may include a bypass air intake through which air from outside the unit can flow upward into the second chamber. Embodiments that have a bypass air intake preferably will also have an intake damper for regulating the flow of air into the second chamber. 
     The first and second walls typically will be, respectively, the front and rear walls of the enclosure, such that the first chamber will be adjacent the front wall. In alternative embodiments, however, the first and second walls could be, respectively, the rear and front walls of the enclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of CRAC units in accordance with the present disclosure will now be described with reference to the accompanying Figures, in which numerical references denote like parts, and in which: 
         FIG. 1  is a schematic vertical cross-section through a prior art CRAC unit. 
         FIG. 2  is a longitudinal vertical section through a first embodiment of a CRAC unit in accordance with the present disclosure, incorporating evaporative cooling media and a drift eliminator. 
         FIG. 3A  is a transverse vertical section through the CRAC unit shown in  FIG. 2 . 
         FIG. 3B  is a transverse vertical section through a variant CRAC unit similar to the embodiment shown in  FIG. 3A  but with a DX cooling coil added. 
         FIG. 4  is an enlarged vertical section through a CRAC unit as shown in  FIG. 3A , in which air enters an upper region of the unit and exits from a lower region of the unit. 
         FIG. 5  is an enlarged vertical section through a variant embodiment of the CRAC unit shown in  FIGS. 3A and 4 , in which air enters a lower region of the unit and exits from a upper region of the unit. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a prior art CRAC unit  10  in which airflow (denoted by flow arrows F) enters the top of the unit (either directly from the room in which the unit is installed or, alternatively, via a duct bringing air from outside the room), passes through a filtration section  12 , then through an A-frame banked cooling coil section  14 , and then is discharged into the room at the bottom of the unit by means of supply fans  16 . Drain pans  15  are provided to carry condensation off the coils  14  to a sump (not shown). 
       FIGS. 2 and 3A  illustrate the general configuration and basic components of one CRAC unit embodiment  100  in accordance with the present disclosure. CRAC unit  100  comprises an enclosure  101  which has a first wall  103  and an opposing second wall  104 , with either or both of walls  103  and  104  having access doors  102  as required for operation and maintenance. Enclosure  101  houses an assembly of air treatment equipment components which in the illustrated embodiment includes a filter section  115  and a cooling section  120 . Filter section  115  and cooling section  120  are each of substantially uniform thickness with generally flat side surfaces, and they mounted within enclosure  101  so as to be substantially parallel and closely adjacent to each other (i.e., in parallel juxtaposition) and oriented vertically within the enclosure  101  between and generally parallel to walls  102  and  103 . In the embodiment shown in  FIG. 4 , this arrangement of the air treatment component assembly results in the formation of a first chamber  140  between filter section  115  and first wall  103 , and a second chamber  145  between cooling section  120  and second wall  104 . 
       FIG. 3B  shows a variant CRAC unit embodiment  150  similar to CRAC unit  100  but with a DX coil  160  added to the air treatment component assembly. 
       FIG. 4  illustrates the airflow path through CRAC unit embodiment  100 . The airflow path through CRAC unit  150  would be similar to that shown in  FIG. 4 . CRAC units  100  and  150  are “downflow” units in which airflow through the unit is from top to bottom. However, these units can be readily adapted for upflow operation, such as in the variant CRAC unit embodiment  200  shown in  FIG. 5 , in which airflow through the unit is from bottom to top. 
     In the downflow CRAC unit  100  shown in  FIG. 4 , air enters a primary air intake  105  at the top of the unit, with the airflow initially being vertically downward (as denoted by airflow arrow F 1 ) within first chamber  140 , but then is diverted horizontally (as denoted by horizontal airflow arrow F 2 ) through filter section  115  and cooling section  120 . Cooling section  120  may comprise cooling coils and/or evaporative media. The use of direct evaporative cooling in a vertically-oriented CRAC unit is thus made possible by configuring the unit  100  such that the airflow pattern through the unit has a primary horizontal component F 2  as illustrated in  FIG. 4 . 
     In the embodiment shown in  FIG. 4 , in which cooling section  120  includes evaporative media, CRAC unit  100  also incorporates a “drift eliminator”  125  (a term that will be well understood by persons skilled in the art) to remove any water droplets present in the airflow exiting the evaporative media, thus preventing what is known as “water carryover” from the evaporative media into the cooled air discharged from the unit. The airflow F 2  downstream of drift eliminator  125  is diverted vertically downward (as denoted by airflow arrow F 3 ) within second chamber  145  to a lower region of CRAC unit  100 , from which it is discharged into the space to be cooled. As indicated in  FIG. 4 , the airflow discharge from CRAC unit  100  could be vertically downward (as denoted by airflow arrow F 4 ), or alternatively horizontal (as denoted by airflow arrow F 5 ) through the front and/or sides of the unit. Supply fans  130  propel the cooled air either directly into the space to be cooled or into connecting ductwork. 
     Also as shown in  FIG. 4 , CRAC unit  100  may optionally be provided with a bypass air intake  110  controlled by an intake damper  112  to allow a regulated downward flow of incoming air into second chamber  145  (as denoted by airflow arrow F 6 ), bypassing cooling section  120  to allow for cooling capacity modulation, by blending the downward-flowing untreated bypass airflow F 6  into the airflow F 2  exiting cooling section  120  (and drift eliminator  125 , as the case may be). Depending on the properties of the primary incoming airflow F 1  (e.g., temperature and humidity), it may not always be necessary for all supplied air to pass through cooling section  120  of CRAC unit  100 . For example, cooled air exiting cooling section  120  can be blended in suitable proportions with warmer untreated bypass air F 6  to produce an airflow supply to the room at a temperature somewhere between the temperatures of the two airflows being blended. 
     The upflow CRAC unit embodiment  200  illustrated in  FIG. 5  operates in substantially the same way as downflow CRAC unit embodiment in  FIG. 4  except for the direction of airflow and correspondingly necessary modifications. In the illustrated embodiment, CRAC unit  200  comprises an enclosure  201  having first and second walls  203  and  204  (and access doors  202 ) and housing an air treatment component package comprising a filter section  115 , cooling section  120 , and drift eliminator  125  generally as in CRAC unit embodiments  100  and  150 . Similar to CRAC unit  100  shown in  FIG. 4 , the arrangement of the air treatment component assembly within enclosure  201  results in the formation of a first chamber  240  between filter section  115  and first wall  203 , and a second chamber  245  between cooling section  120  and second wall  204 . 
     A lower portion of enclosure  201  defines an intake plenum  210  having a roof structure  212  defining a primary air intake  215  through which intake air (denoted by airflow arrow F 1 ′) can flow upward into first chamber  240  within enclosure  201  to be horizontally diverted (as denoted by horizontal airflow arrow F 2 ′) through filter section  115 , cooling section  120 , and drift eliminator  125 . 
     The airflow F 2 ′ downstream of drift eliminator  125  is diverted vertically upward (as denoted by airflow arrow F 3 ′) within second chamber  245  to an upper region of CRAC unit  200 , from which it is discharged into the space to be cooled by supply fans  130 . As indicated in  FIG. 5 , the airflow discharge from CRAC unit  200  could be vertically upward (as denoted by airflow arrow F 4 ′), or alternatively horizontal (as denoted by airflow arrow F 5 ′) through the front and/or sides of the unit. 
     Also as shown in  FIG. 5 , CRAC unit  200  optionally may be provided with a bypass air intake  220  controlled by an intake damper  222  to allow a regulated upward flow of incoming air into second chamber  245  (as denoted by airflow arrow F 6 ′), bypassing cooling section  120  and flowing upward within second chamber  245  to mix with the airflow F 2 ′ exiting cooling section  120  and drift eliminator  125 . 
     The airflow paths through the CRAC units shown in  FIGS. 4 and 5  provide enhanced flexibility over prior art CRAC units and facilitate standardization of parts, thus avoiding the need for specialized components such as A-frame or V-frame coils and banked filters as in prior art CRAC units. The horizontal airflow across the internal components of the CRAC unit results in reduces face velocities across those components. Low face velocities increase filtration efficiency, prevent water carryover, reduce static pressure drop through the unit, and increase the cooling effectiveness of the cooling systems in the unit. The horizontal airflow in CRAC units in accordance with the present disclosure also allows for the use of direct evaporative cooling systems within the units using saturated evaporative media pads. 
     CRAC units in accordance with the present disclosure can be adapted to use a variety of cooling systems, including but not limited to chilled water, DX refrigeration, and direct evaporative cooling systems. A wide range of airflows and static pressures can be accommodated. The CRAC units and associated control systems can be designed to provide reliable data center climate control while significantly reducing the electrical energy consumption of the computer room or data center&#39;s HVAC system. 
     CRAC units in accordance with the present disclosure can be manufactured as packaged pieces of equipment, requiring a single-point electrical connection and communications connection as well as one piping connection each for water and drain for easy unit set-up on site. Outdoor air and return air can be mixed remotely via the building&#39;s ventilation system and ducted into the CRAC unit. 
     In preferred embodiments, CRAC units as disclosed herein are controlled by dedicated, onboard PLCs (programmable logic controllers). Each CRAC unit&#39;s onboard controller controls all aspects of the unit&#39;s operation, including monitoring internal temperatures, modulating fan speed, and operation of the cooling systems. 
     Variants of the disclosed CRAC units can be adapted in accordance with one or more options as listed below with respect to airflow configuration, air conditioning method, control type, and fan type: 
     Flow Configuration 
     Both downflow or upflow configurations are readily adaptable for mounting in rooms with or without raised floor systems, for example:
         Downflow units with an air intake in the upper section of the unit (top, front, side, or back), and an air discharge outlet in a lower region of the unit (bottom, front, side, or back).   Upflow units with an air intake in the lower section of the unit (bottom, front, side, or back), and an air discharge outlet in a upper region of the unit (top, front, side, or back).
 
Air Conditioning Method
       

     One or more air conditioning options can be used in a given CRAC unit, for example: 
     Direct evaporative cooling—uses adiabatic evaporative cooling to cool the air stream by streaming water down an internal evaporative media pad. All components of the evaporative cooling system are provided integral to the unit. 
     Water cooling—uses water passing through a coil in the CRAC unit to act as a cooling medium. Various cooling sources are possible, including: 
     Chilled water using the building&#39;s chilled water system. Cooling provided by air-cooled or water-cooled chillers. 
     Waterside economizer: water is cooled using an outdoor drycooler or indirect evaporative cooler; this can be used independently or in conjunction with a water-cooled chiller. 
     Seawater, river water, irrigation water, or water from other natural sources can be passed through a coil to provide cooling. 
     DX cooling—uses a refrigeration-based direct expansion (DX) coil to cool the airstream, with a rooftop condensing unit to provide heat rejection. 
     Heating—for applications requiring specific dehumidification reheat, a heating coil can be provided to warm the airstream; heating coils may be of hot water or electric element types. 
     CRAC Unit Control 
     CRAC units in accordance with the present disclosure can use a variety of different control options, preferably including an onboard PLC controller capable of handling all unit functions, and optionally including any of the following: 
     Full stand-alone unit control—all CRAC unit control is carried out by the onboard controller. Units can modulate remote dampers, control fan speed, choose modes of cooling, modulate valves, control pumps, etc. 
     Remote automatic control—some high-level unit control is handled by a remote building management system (BMS) or by a dedicated central control system for the CRAC units. Modes of cooling and overall enable/disable functions are controlled by the external controller, as well as operating setpoints. Full CRAC unit information can be sent to the remote controller, and the remote controller is capable of controlling any part of the unit as may be desired. 
     Constant/variable air volume—supply fans can be speed-controlled for variable-volume systems. For constant air volume operation, the speed controller is set to a constant value at the time of CRAC unit start-up. 
     Sensors—various sensors can be provided with the CRAC unit for various control aspects. Examples of sensors include temperature, humidity, smoke detection, and water detection. 
     Miscellaneous control options—other modes of operation such as control of external devices such as duct-mixing dampers and remote pumps, etc. 
     Fan Types 
     CRAC units in accordance with the present disclosure can be adapted to accommodate a variety of different required airflows and system static pressures according to the type of fans selected. For compactness of size and pressure-handling capabilities, the preferable fan type is an airfoil-blade backwards-inclined plenum fan. However, other types of fans such as forward and backward curved centrifugal scroll fans could also be used. 
     It will be readily appreciated by those skilled in the art that various modifications to embodiments in accordance with the present disclosure may be devised without departing from the scope and teaching of the present teachings, including modifications which may use equivalent structures or materials hereafter conceived or developed. It is to be especially understood that the scope of the claims appended hereto should not be limited by any particular embodiments described and illustrated herein, but should be given the broadest interpretation consistent with the description as a whole. It is also to be understood that the substitution of a variant of a claimed element or feature, without any substantial resultant change in functionality, will not constitute a departure from the scope of the disclosure. 
     In this patent document, any form of the word “comprise” is intended to be understood in its non-limiting sense to mean that any item following such word is included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one such element is present, unless the context clearly requires that there be one and only one such element. Any use of any form of any term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements in question, but may also extend to indirect interaction between the elements such as through secondary or intermediary structure. 
     Relational terms such as “vertical”, “horizontal”, and “parallel”, are not intended to denote or require absolute mathematical or geometrical precision. Accordingly, such terms are to be understood as denoting or requiring substantial precision only (e.g., “substantially vertical” or “generally vertical”) unless the context clearly requires otherwise. Any use of any form of the term “typical” is to be interpreted in the sense of representative of common usage or practice, and is not to be interpreted as implying essentiality or invariability.