Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-05-13
2001-12-11
Thompson, Gregory (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C454S184000
Reexamination Certificate
active
06330154
ABSTRACT:
The present invention relates to cooling apparatus, in particular, but not exclusively, cooling apparatus for cooling electrical or other equipment. The invention further relates to an electrical device comprising the cooling apparatus, and a method of cooling equipment.
The invention relates more particularly to electrical equipment which performs a processing or memory function, such as any processor (for example a semiconductor or other logic device, an integrated circuit, a microprocessor and the like) or any storage device (for example a mass storage device). Such equipment may be in the form of an integrated circuit, possibly mounted on a printed circuit board. Accordingly, the electrical device may typically be a computer, modem, switch, hub or like device.
An electrical device such as a computer includes various items of electrical equipment which generate heat during use. During use, such equipment becomes warm. It is undesirable for the equipment to become too hot because excessive heat can cause damage to components of the equipment. It is known to cool electrical equipment using one or more fans and indeed a cooling fan is often provided in electrical devices. In a conventional arrangement, electrical equipment is arranged within a casing. The fan sucks air through one or more vents in the casing, the air passes over the equipment and out of the casing via the fan.
However, under many conditions, such fans have been found to be inefficient.
Furthermore, it has been realised pursuant to the present invention that, in many situations, some of the items of electrical equipment in the device require more cooling than other equipment. In order to cool such equipment sufficiently, a high air flow through the equipment is required. Other equipment which requires little or no cooling is also subject to the high air flow unnecessarily.
The present invention seeks to mitigate one or more of the above-mentioned problems and/or other problems.
According to the present invention, there is provided a cooling apparatus for cooling electrical equipment using a fan, the apparatus comprising a duct for communication with the fan and for transporting air past the equipment, the duct including a diffuser.
As used herein, it should be understood that the term “duct” should be interpreted broadly to include any passage or channel along which air flow may be directed. The term is not restricted to fully enclosed structures (as for example a tube), but also includes for example structures which are not fully enclosed, and yet have the flow directing features of a duct. It includes structures which, with the addition of say a wall of the device in which the duct may be located, constitute fully enclosed structures. Considering a duct having a generally rectangular section, for example, the air flow might be enclosed only on three sides or on two sides: the duct may comprise three surfaces or only two surfaces. It is envisaged that the duct may only comprise a single surface but that surface may serve to effect the desired air flow.
By providing a cooling apparatus with a duct, the flow of air can be arranged so that it passes directly past the equipment to be cooled. Furthermore, the flow of air directly adjacent the equipment may be more easily controlled. Thus the efficiency of the cooling apparatus may be increased. By using a duct for the transport of the air, the equipment to be cooled by the cooling apparatus may also be remote from the fan.
Preferably, the diffuser is arranged adjacent the downstream end of the duct. In arrangements in which air is sucked through the duct and into a fan, the diffuser is advantageously arranged immediately upstream of the fan. The diffuser is a passage which gradually increases in sectional area downstream and its function is to reduce the velocity of flow of the air while preserving its total head as much as possible.
The use of a diffuser is particularly advantageous in arrangements where the diffuser is provided directly upstream from the fan. The efficiency of the fan can be maximised by arranging for the velocity of the air at the fan to be in the most desirable range for its operation. The most desirable velocity of the air flow at the fan will usually be below that of the most desirable velocity for the cooling of the electrical equipment. Thus, by using the diffuser, a high velocity of air can be maintained upstream of the fan while not sacrificing too much the efficiency of the fan.
It will be appreciated that pressure will be lost as the air flow passes through regions of changing sectional area in the duct as well as there being a general pressure loss due to friction effects along the length of the duct. Additional losses of pressure at the downstream end are advantageously reduced by the use of the diffuser. Preferably, the dimensions of the diffuser are chosen to recover as much of the pressure head as possible. In many cases, the diffuser dimensions may not be those required for the maximum pressure recovery because of lack of space in the device.
The area ratio of the diffuser outlet to the inlet may be, for example, greater than 3:2, 2:1, 3:1 5:1 or even 10:1; it may be for example less than 100:1, 50:1, 20:1 or 10:1. In a preferred embodiment of the invention, the area ratio of the diffuser outlet to the diffuser inlet is 2.4:1. The areas of the diffuser outlet and inlet are preferably the (transverse) sectional areas measured at the downstream and the upstream ends, respectively, of the diffuser.
The particular size of the diffuser will depend on the device in which it is arranged, the size of the duct and the nature of the fan. In many arrangements, for example where the duct is installed in a computer, the area of the diffuser inlet is preferably greater than 100 mm
2
, 150 mm
2
, 200 mm
2
, or 300 mm
2
. The area may be less than 1000 mm
2
, 750 mm
2
, 500 mm
2
, or 400 mm
2
. Further, the area of the diffuser outlet is preferably greater than 500 mm
2
, 750 mm
2
, or 1000 mm
2
.
A long diffuser is preferred but, as indicated above, might not be practical with regard to the layout of the device. Preferably, the length of the diffuser is not less than the mean width of the inlet of the diffuser. Preferably, the length of the diffuser is at least twice, three times, or four times the width of the inlet of the diffuser. Where the cross section of the inlet of the diffuser is generally circular, the mean width will usually be the diameter of the inlet. Where the inlet has a different cross section, the mean width may conveniently be determined by averaging several lengths transverse to direction to the air flow. In some cases the duct might not enclose the air flow on all sides. In such cases the mean width of the duct may be determined from a consideration of the stream of air which in use passes through the duct.
Preferably, the resultant angle of the diffuser is greater than 9, 15, 20 or 30 degrees. The resultant angle preferably is the angle of the wall of the diffuser to the direction of air flow in the duct. In most arrangements, the angle of the diffuser will be limited by the size and layout of the device.
Preferably, the diffuser has a well rounded entry and preferably a well rounded exit. Preferably the kick of the diffuser is also rounded. Such an arrangement is thought to give improved flow characteristics of the air flowing through the diffuser.
Preferably, the duct includes a nozzle. Preferably, the nozzle is arranged adjacent the upstream end of the duct and is a convergent nozzle having a sectional area which decreases downstream. The nozzle converts pressure head at the mouth of the duct into velocity head and assists the formation of the desirable high velocity flow in the duct. By using a nozzle at the upstream end of the duct, air can be brought to a high velocity almost immediately on entering the duct and thus only a small length of duct is required upstream of the first item of equipment to be cooled by the duct. The use of the nozzle also gives smoother flow of the air entering the duct.
Preferably the area
Foley Nicholas
Fryers Bruce
MacManus Gerard
Tate Michael
3Com Corporation
Michaelson Peter L.
Michaelson & Wallace
Skafar Janet M.
Thompson Gregory
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