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7148DG 参数 Datasheet PDF下载

7148DG图片预览
型号: 7148DG
PDF下载: 下载PDF文件 查看货源
内容描述: 与折叠鳍频道风格散热片 [Channel style heat sink with folded back fins]
分类和应用: 散热片
文件页数/大小: 116 页 / 8734 K
品牌: AAVID [ AAVID THERMALLOY, LLC ]
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Reading a Thermal Performance Graph  
The performance graphs you will see in this  
catalog (see graph 579802) are actually a  
composite of two separate graphs which  
have been combined to save space. The small  
arrows on each curve indicate to which axis  
the curve corresponds. Thermal graphs are  
published assuming the device to be cooled  
is properly mounted and the heat sink is in  
its recommended mounting position.  
CONVERTING VOLUME  
TO VELOCITY  
579802  
Air Velocity—Feet Per Minute  
0
200  
400  
600  
800  
1000  
Although most fans are normally rated and  
compared at their free air delivery at zero  
back pressure, this is rarely the case in most  
applications. For accuracy, the volume of  
output must be derated 60%–80% for  
the anticipation of back pressure.  
100  
80  
20  
16  
12  
8
60  
40  
4
0
20  
0
0
1
2
3
4
5
Heat Dissipated—Watts  
EXAMPLE: The output air volume  
of a fan is given as 80 CFM. The output area  
is 6 inches by 6 inches or 36 in2 or 25 ft2.  
To find velocity:  
GRAPH A  
GRAPH B  
Air Velocity—Feet Per Minute  
400  
600 800  
0
200  
1000  
Volume (CFM)  
Velocity (LFM) =  
20  
16  
12  
8
100  
80  
area (ft2)  
80  
60  
Velocity =  
= 320  
0.25  
40  
4
0
20  
0
Velocity is 320 LFM, which at 80%,  
derates to 256 LFM.  
0
1
2
3
4
5
Heat Dissipated—Watts  
GRAPH B is used to show heat sink per-  
formance when used in a forced convec-  
tion environment (i.e. with forced air flow  
through the heat sink). This graph has its  
origin in the top right hand corner with  
the horizontal axis representing air velocity  
over the heat sink LFM* and the vertical  
axis representing the thermal resistance of  
the heat sink (°C/W). Air velocity is calculat-  
ed by dividing the output volumetric flow  
rate of the fan by the cross-sectional area  
of the outflow air passage.  
GRAPH A is used to show heat sink perform-  
ance when used in a natural convection envi-  
ronment (i.e. without forced air). This graph  
starts in the lower left hand corner with the  
horizontal axis representing the heat dissipa-  
tion (watts) and the vertical left hand axis  
representing the rise in heat sink mounting  
surface temperature above ambient (°C). By  
knowing the power to be dissipated, the  
temperature rise of the mounting surface  
can be predicted. Thermal resistance in natu-  
ral convection is determined by dividing this  
temperature rise by the power input (°C/W).  
DESIGN ASSISTANCE  
Aavid Thermalloy can assist in the design  
of heat sinks for both forced and natural  
convection applications. Contact us for help  
with your next thermal challenge. For more  
information, visit our web site at:  
www.aavidthermalloy.com  
Velocity (LFM)* = Volume (CFM)**  
area (ft2)  
EXAMPLE A: Aavid Thermalloy part number  
579802 is to be used to dissipate 3 watts of  
power in natural convection. Because we are  
dealing with natural convection, we refer to  
graph “A. Knowing that 3 watts are to be dis-  
sipated, follow the grid line to the curve and  
find that at 3 watts there is a temperature  
rise of 75°C. To get the thermal resistance,  
divide the temperature rise by the power  
dissipated, which yields 25°C/W.  
EXAMPLE B: For the same application  
we add a fan which blows air over the heat  
sink at a velocity of 400 LFM.  
The addition of a fan indicates the use of  
forced convection and therefore we refer  
to graph “B. This resistance of 9.50°C/W is  
then multiplied by the power to be dissi-  
pated, 3 watts. This yields a temperature  
rise of 28.5°C.  
* Linear feet per minute  
** Cubic feet per minute  
USA Tel: +1 (603) 224-9988 email: info@aavid.com  
Singapore Tel: +65 6362 8388 email: sales@aavid.com.sg  
Taiwan Tel: +886(2) 2698-9888 email: sales@aavid.com.tw  
AMERICA  
EUROPE  
ASIA  
Italy Tel: +39 051 764011 email: sales.it@aavid.com  
United Kingdom Tel: +44 1793 401400 email: sales.uk@aavid.com  
11  
www.aavidthermalloy.com  
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