Abstract:
A cabinet for electronics equipment, comprising: a compartment for installing the electronics equipment; a door for accessing the compartment; an outer duct mounted on an outer surface of the door for directing exterior air around a heat exchanger core mounted in the door, the heat exchanger core for transferring heat from interior air in the compartment to the exterior air to thereby cool the interior air; an exhaust duct extending over a top surface of the compartment and pneumatically coupling with the outer duct when the door is in a closed position, the exhaust duct for exhausting the exterior air and for reducing solar loading on the top surface by transferring heat absorbed by the exhaust duct to the exterior air passing therethrough; and, one or more fans for forcing the exterior air in through the outer duct, around the heat exchanger core, and out through the exhaust duct, the one or more fans being mounted between the outer duct and the exhaust duct to thereby attenuate noise emitted by the one or more fans.

Description:
FIELD OF THE INVENTION 
   This invention relates to the field of equipment cabinets, and more specifically, to cabinets for electronics equipment. 
   BACKGROUND OF THE INVENTION 
   The power requirements of electronics equipment (e.g., telecommunications equipment) is continually increasing. In particular, newer generation telecommunications equipment has increased power density. That is, the power requirements of such equipment per unit volume has increased. As a result, this newer generation equipment dissipates more heat during operation than older generation equipment. Dissipating heat from electronics equipment is important as excess operating temperatures may decrease the operating performance and life-span of the equipment. As such, electronics equipment installed in cabinets require sufficient cooling to ensure optimal operating performance and life-span. This is especially so for electronics equipment cabinets that are weatherproofed for outdoor use. 
   Several existing electronics equipment cabinets rely on the natural convection of heat dissipated from enclosed equipment to the exterior cabinet walls where it is then conducted to the external environment thereby providing cooling. However, such natural convection cooling techniques are typically not sufficient to provide the cooling needed to promote optimal performance of newer generation electronics equipment. 
   Other existing electronics equipment cabinets relay on forced convection cooling using fans, heat exchangers, etc. Refer to, for example, U.S. Pat. No. 6,164,369 to Stoller. However, the fans used in such equipment often generates excessive noise. This is problematic as noise emission limits for electronics equipment cabinets installed in the field are being routinely lowered. 
   A need therefore exists for an improved electronics equipment cabinet. Accordingly, a solution that addresses, at least in part, the above and other shortcomings is desired. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention, there is provided a cabinet for electronics equipment, comprising: a compartment for installing the electronics equipment; a door for accessing the compartment; an outer duct mounted on an outer surface of the door for directing exterior air around a heat exchanger core mounted in the door, the heat exchanger core for transferring heat from interior air in the compartment to the exterior air to thereby cool the interior air; an exhaust duct extending over a top surface of the compartment and pneumatically coupling with the outer duct when the door is in a closed position, the exhaust duct for exhausting the exterior air and for reducing solar loading on the top surface by transferring heat absorbed by the exhaust duct to the exterior air passing therethrough; and, one or more fans for forcing the exterior air in through the outer duct, around the heat exchanger core, and out through the exhaust duct, the one or more fans being mounted between the outer duct and the exhaust duct to thereby attenuate noise emitted by the one or more fans. 
   Advantageously, the noise generated by the fans is attenuated as it passes along the outer and exhaust ducts, the fans being located between the two. To provide further noise attenuation, noise insulation may be added to the exhaust duct and to a door intake duct extending the outer duct. These ducts also serve to insulate the electronics compartment from solar loading on corresponding external surfaces. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the embodiments of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
       FIG. 1  is a front view illustrating an electronics equipment cabinet in accordance with an embodiment of the invention; 
       FIG. 2  is a top view of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 3  is a section view of the electronics equipment cabinet of  FIG. 1  (along line A-A in  FIG. 1 ); 
       FIG. 4  is a front perspective view of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 5  is a rear perspective view of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 6  is a front perspective exploded view of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 7  is a front view (doors and panels removed) of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 8  is a left side view (doors and panels removed) of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 9  is a perspective view (exploded) of the inner side of the front door of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 10  is a front perspective view (top panel removed) of the electronics equipment cabinet of  FIG. 1 ; 
       FIG. 11  is a front view of the heat exchanger mounted in the front door of  FIG. 9 ; 
       FIG. 12  is a top view of the heat exchanger of  FIG. 11 ; 
       FIG. 13  is a right side view of the heat exchanger of  FIG. 11 ; 
       FIG. 14  is a front view of the outer loop fan module of the heat exchanger of  FIG. 11 ; 
       FIG. 15  is a top view of the outer loop fan module of  FIG. 14 ; 
       FIG. 16  is a section view of the outer loop fan module of  FIG. 14  (along line A-A in  FIG. 15 ); 
       FIG. 17  is a front perspective view of the electronics equipment cabinet of  FIG. 1  (doors and panels removed) illustrating the application of sound insulation and/or thermal insulation; 
       FIG. 18  a rear perspective view of the cabinet (doors and panels removed) illustrating the application of sound insulation and/or thermal insulation; and, 
       FIG. 19  is a section view (along line A-A in  FIG. 1 ) illustrating air flows through the electronics equipment cabinet. 
   

   It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   In the following description, details are set forth to provide an understanding of the invention. In some instances, certain circuits, structures and techniques have not been described or shown in detail in order not to obscure the invention. 
     FIG. 1  is a front view illustrating an electronics equipment cabinet  100  in accordance with an embodiment of the invention.  FIG. 2  is a top view of the cabinet  100 .  FIG. 3  is a section view of the cabinet  100  (along line A-A in  FIG. 1 ).  FIG. 4  is a front perspective view of the cabinet  100 .  FIG. 5  is a rear perspective view of the cabinet  100 .  FIG. 6  is a front perspective exploded view of the cabinet  100 .  FIG. 7  is a front view (doors and panels removed) of the cabinet  100 . And,  FIG. 8  is a left side view (doors and panels removed) of the cabinet  100 . 
   Referring to  FIGS. 1-8 , the cabinet  100  has a frame or housing  110  in which is formed an electronics equipment compartment  200 , a battery compartment  220 , a splice compartment  600 , and a cable entry compartment  660 . In this embodiment, the electronics equipment compartment  200  is positioned above the battery compartment  220  and the splice compartment  600  is positioned above the cable entry compartment  660 , the splice and cable entry compartments  600 ,  660  being generally adjacent to the electronics equipment and battery compartments  200 ,  220 , respectively. 
   The electronics equipment compartment  200  has a front door  120  for providing access to the compartment  200  and to an exhaust duct  300 , which will be described below. The electronics equipment compartment  200  is for mounting electronics equipment  210  such as telecommunications equipment  211 , DC (Direct Current) power supplies  212 , and fiber termination panels  213 . The front door  120  has ventilation openings  121 , the operation of which will be described in more detail below. The front door  120  may be mounted to the housing  110  or compartment  200  with hinges, pins, etc. 
   The battery compartment  220  has a removable cover  130  for providing access to the compartment  220 . The battery compartment  220  is for mounting batteries  221  to provide standby power to the electronics equipment  210 . The removable cover  130  has ventilation openings  131 , the operation of which will be described in more detail below. The removable cover  130  may be mounted to the housing  110  with tabs, pins, etc. 
   The splice and cable entry compartments  600 ,  660  share a side door  140  for providing access to these compartments  600 ,  660 . The side door  140  has ventilation openings  141  opening into the cable entry compartment  660 , the operation of which will be described in more detail below. The splice compartment  600  is for mounting cable termination blocks  610 ,  620  for POTS (Plain Old Telephone Service) lines, DSL (Digital Subscriber Line) lines, etc. The splice compartment  600  may also house an AC (Alternating Current) power panel  640  for providing AC power to the DC power supplies  212  to power the electronics equipment  210  and an AC convenience outlet  630 . The cable entry compartment  660  facilitates the entry of cables (not shown) to the splice compartment  600  and cabinet  100 . These cables enter the cable entry compartment  660  though an opening  690  in the bottom of that compartment  660 . The side door  140  may be mounted to the housing  110  with hinges, pins, etc. 
   Thus, the housing  110  has separate electronics equipment, battery, splice, and cable entry compartments  200 ,  220 ,  600 ,  660 . Suitable openings (not shown) are provided between compartments for the passage of wiring (not shown). 
   Gases and heat generated by the batteries  221  are exhausted from the battery compartment  220  through the ventilation openings  131  in the battery compartment cover  130 . To provided enhanced ventilation for the battery compartment  220 , optionally, a fan  810  is mounted in the cable entry compartment  660  through the inner panel or wall  650  separating the cable entry compartment  660  from the battery compartment  220 . Noting that the ventilation openings  141  in the side door  140  open into the cable entry compartment  660 , the fan  810  functions to draw air in through the ventilation openings  141  in the side door  140 , through the panel  650 , across the battery compartment  220 , and out through the ventilation openings  131  in the battery compartment cover  130 . According to an alternate embodiment, the air flow is in the opposite direction with the fan  810  functioning to draw air in through the ventilation openings  131  in the battery compartment cover  130 , across the battery compartment  220 , through the panel  650 , and out through the ventilation openings  141  in the side door  140 . 
     FIG. 9  is a perspective view (exploded) of the inner side of the front door  120  of the electronics equipment cabinet  100  of  FIG. 1 .  FIG. 10  is a front perspective view (top panel  150  removed) of the cabinet  100 .  FIG. 11  is a front view of the heat exchanger  320  mounted in the front door  120  of  FIG. 9 .  FIG. 12  is a top view of the heat exchanger  320 .  FIG. 13  is a right side view of the heat exchanger  320 .  FIG. 14  is a front view of the outer loop fan module  330  of the heat exchanger  320  of  FIG. 11 .  FIG. 15  is a top view of the outer loop fan module  330 . And,  FIG. 16  is a section view of the outer loop fan module  330  (along line A-A in  FIG. 15 ). 
   Referring to  FIGS. 1-16 , the enclosure has a top casing or panel  150  spaced from a top surface  1020  of the electronics equipment compartment  200  to form an enclosed exhaust duct  300  therebetween. The exhaust duct  300  extends across the top of the electronics equipment compartment  200 , from the front door  120  to the rear wall or panel  500  of the electronics equipment compartment  200 . The exhaust duct  300  has a front inlet opening  390  at the front door  120  and a rear outlet opening  395  at the rear panel  500 . In one embodiment, the rear panel  500  extends upwards to cap the rear opening  395  of the exhaust duct  300  and ventilation openings  501  for the exhaust duct  300  are provided in the rear panel  500 . Of course, the ventilation openings  501  may be integrated into the top panel  150 . When the front door  120  is in a closed position, the front inlet opening  390  of the exhaust duct  300  engages an outer loop fan module  330  of a heat exchanger  320  mounted in the front door  120 , as will be described in more detail below. The top panel  150  may be provided with one or more lifting eyes  160  mounted therethrough to facilitate lifting of the cabinet  100 . 
   The front door  120  has an outer casing or door  900  fitted over an inner panel or door  910 . When the front door  120  is in the closed position, the inner surface  911  of the inner door  910  faces the interior of the electronics equipment compartment  200  and the front inlet opening  390  of the exhaust duct  300 . The inner door  910  isolates the electronics equipment compartment  200  from the exterior environment when the front door  120  is closed. The outer door  900  is mounted over the outer surface  912  of the inner door  910 . The outer surface  902  of the outer door  900  faces the environment while the inner surface  901  of the outer door  900  faces the outer surface  912  of the inner door  910 . The outer door  900  is box-shaped such that when it is mounted over the outer surface  912  of the inner door  910  an enclosed door intake duct  360  is formed. The ventilation openings  121  in the outer door  120  open into this door intake duct  360 . In normal operation, the outer door  900  and inner door  910  are fastened together and function as one unit (i.e., a single door). 
   The heat exchanger  320  is mounted in the inner door  910 . The heat exchanger  320  has a enclosed outer loop duct  340  mounted on the outer surface  912  of the inner door  910 . In addition, the heat exchanger  320  has an enclosed inner loop duct  310  mounted on the inner surface  911  of the inner door  910 . The outer loop duct  340  and the inner loop duct  310  are generally coextensive being separated by a heat exchanger core  1210  which may be, or form, a portion of the inner door  910 . The heat exchanger core has an inner surface  1211  facing the inner loop duct  310  and an outer surface  1212  facing the outer loop duct  340 . It is through the heat exchanger core  1210  that heat from the interior air in the electronics equipment compartment  200  will be dissipated to the external environment. Thus, the outer loop duct  340  is located in the door compartment  360  and the inner loop duct  310  is located in the electronics equipment compartment  200 . 
   According to one embodiment, the outer loop duct  340  is spaced from the inner surface  901  of the outer door  900 . This spacing allows for the optional application of sound insulation  1710  and/or thermal insulation  1720  on the inner surface  901  of the outer door  900  and for the circulation of air within the door intake duct  360 . 
   The outer loop duct  340  of the heat exchanger  320  has vertical heat radiating fins  1220  disposed therein and forming part of the heat exchanger core  1210  to improve heat transfer efficiency. Alternatively, the fins  1220  may be heat pipes, corrugated surfaces, or other heat exchanging elements known in the art. The outer loop duct  340  has an outlet opening  341  at its top end and an inlet opening  342  at its bottom end allowing for the passage of air therethrough. 
   The inner loop duct  310  has an inlet opening  322  at its top end an outlet opening  323  at its bottom end allowing for the passage of air therethrough. Both the inlet and outlet openings  322 ,  323  face into the electronics equipment compartment  200 . Like the outer loop duct  340 , the inner loop duct  310  has vertical heat radiating fins  1120  disposed therein and forming part of the heat exchanger core  1210  to improve heat transfer efficiency. Alternatively, the fins  1120  may be heat pipes, corrugated surfaces, or other heat exchanging elements known in the art. In addition, the inner loop duct  310  has one or more fans  321  mounted at the bottom outlet opening  323  for drawing air in the electronics equipment compartment  200  over the electronics equipment  210 , through the top inlet opening  322  in the inner loop duct  310 , over the fins  1120  of the heat exchanger core  1210  disposed in the inner loop duct  310 , and out through the bottom outlet opening  323  of the inner loop duct  310 . This air flow will be referred to as the inner loop air flow  1910  below. According to an alternate embodiment, the fans  321  may be located at the top inlet opening  322 . 
   According to one embodiment, the fins  1120 ,  1220  may represent opposite sides of a corrugated surface forming the heater exchanger core  1210 . 
   An outer loop fan module  330  is mounted above the top outlet opening  341  of the outer loop duct  340  on the outer surface  912  of the inner door  910 . The outer loop fan module  330  is mounted over an opening  301  in the inner door  910  which, when the front door  120  is in a closed position, is aligned with the front inlet opening  390  of the exhaust duct  300 . The outer loop fan module  330  is elbow-duct shaped having a bottom inlet opening  334  aligned with the top outlet opening  341  of the outer loop duct  340  and having a top outlet opening  335  aligned with the opening  301  in the inner door  910 . In addition, the outer loop fan module  330  has one or more fans  331  mounted therein for drawing air from the external environment through the ventilation openings  121  in the front door  120 , through the door intake duct  360 , through the bottom inlet opening  342  of the outer loop duct  340 , over the fins  1220  of the heat exchanger core  1210  disposed in the outer loop duct  340 , through the top outlet opening  341  in the outer loop duct  310 , through the bottom inlet opening  334  of the outer loop fan module  330 , through the outer loop fan module  330 , through the top outlet opening  335  of the outer loop fan module  330 , through the opening  301  in the inner door  910 , through the front inlet opening  390  of the exhaust duct  300 , through the exhaust duct  300 , through the rear outlet opening  395  of the exhaust duct  300 , and out through the ventilation openings  501  in the rear panel  500 . This air flow will be referred to as the outer loop air flow  1920  below. 
   Of course, rather than a separate outer loop fan module  330 , the outer loop fan module  330  and the outer loop duct  340  may be a single unit. 
     FIG. 17  is a front perspective view of the electronics equipment cabinet  100  of  FIG. 1  (doors  120 ,  140  and panels  130  removed) illustrating the application of sound insulation  1710  and/or thermal insulation  1720 . And,  FIG. 18  a rear perspective view of the cabinet  100  (doors  120 ,  140  and panels  130  removed) illustrating the application of sound insulation  1710  and/or thermal insulation  1720 . To improve the thermal performance of the cabinet  100  and to reduce noise emissions, optional thermal insulation  1720  and/or sound insulation  1710  may be applied to the inner surface  901  of the front door  900 , to the inner surface  151  of the top panel  150 , and to the inner surfaces of exterior facing walls of the electronics equipment and splice compartments  200 ,  600 . The sound insulation  1710  functions to reduce noise emissions generated by the fans  321 ,  331  and/or electronic equipment  210 . The thermal insulation  1720  functions to reduce solar/thermal loading from the sun and/or the external environment. 
     FIG. 19  is a section view (along line A-A in  FIG. 1 ) illustrating air flows  1910 ,  1920  through the electronics equipment cabinet  100 . In operation, with the front door  120  closed, inner loop air flow  1910  circulates warm interior air from the top of the electronics equipment compartment  200  through the inner loop duct  310  of the heat exchanger  320  where heat is transferred to cool exterior air being circulated through the outer loop duct  340  of the heat exchanger  320 . The two air flows  1910  and  1920  are isolated and do not mix (i.e., exterior air does not enter the electronics equipment compartment  200 ). The interior air flows in a direction from top to bottom of the inner loop duct  310  while the exterior air flows in a direction from bottom to top of the outer loop duct  340 . Thus, the heat exchanger  320  may be referred to as a “counterflow” heat exchanger. These opposite air flow directions improve the heat transfer efficiency of the heat exchanger  320 . The cooled interior air exits the inner loop duct  310  into the bottom of the electronics equipment compartment  200  where it absorbs heat from the electronics equipment  210  and is warmed as it rises to the top of the compartment  200 . One or more vertical baffles  380  may be provided at the bottom of the electronics equipment compartment  200 , extending from the front to the back of the compartment  200 , to distribute and direct the cooled air over the electronics equipment  210 . The cool exterior air in the outer loop duct  340  absorbs heat from the interior air, is warmed, and is expelled through the exhaust duct  300 . The top panel  150 , being located on the top of the cabinet  100 , absorbs heat from the sun (i.e., solar thermal loading) when the cabinet  100  is located outdoors. This heat is transferred from the inner surface  151  of the top panel  150  to the exterior air flowing through the exhaust duct  300  further warming this air before it is expelled through the ventilation openings  501  at the rear of the cabinet  100 . 
   According to one embodiment, the air flows  1910 ,  1920  are facilitated by natural convection rather than by one or more of the inner loop and outer loop fans  321 ,  331 . According to one embodiment, the cabinet  100  is primarily constructed from sheet metal. 
   Advantageously, the cabinet  100  and its front door  120  allows for the ducting  300 ,  360  of the outer loop air flow  1920  both before and after the fans  331  and heat exchanger  230 . This ducting  300 ,  360  may have sound absorbing/attenuating material  1710  added to the walls thereof to create sound deadening spaces. This ducting  300 ,  360  also serves to insulate the electronics compartment  200  from solar loading on the corresponding external surfaces. The placement of the outer loop fan module  330  between the outer loop duct  340  and the exhaust duct  300 , well away from the ventilation openings  121 ,  501  in the front door  120  and rear panel  500 , reduces fan  331  noise emitted by the cabinet  100 . In addition, this placement improves fan  331  life as the fans  331 , being remote from the ventilation openings  121 ,  501 , are protected from the elements (i.e., rain, snow, dust, etc.). Furthermore, the reduction in solar loading on the top panel  150  by the exhaust duct  300  allows for a smaller capacity heat exchanger  320  and fans  321 ,  331  further enhancing the efficiency of the cabinet  100 . In addition, the baffling  380  provided in the electronics equipment compartment  200  improves circulation of cooled interior air over the heat producing electronics equipment  210  hence increasing heat transfer from this equipment. Moreover, the location of the ventilation openings  121 ,  501  on opposite sides (i.e., front and back) of the cabinet  100  helps to prevent re-circulation of exterior air hence improving the thermal efficiency of the cabinet. 
   The embodiments of the invention described above are intended to be exemplary only. Those skilled in this art will understand that various modifications of detail may be made to these embodiments, all of which come within the scope of the invention.