In this post we are going to see how to find the Area of a Sand Trap Louver. But first, we will see..
What is a sand trap louver?
Sand trap louvers are specialty louvers designed to be the primary filters for air intakes, in areas where sand and dust are prevalent. Normally, the sand trap louver consists of two rows of interlocking vertical blades that catches upto 93% of sand and dust. Sand trap louvers are available with a full range of disposable and replaceable filters. The Aluminum washable filter with frame is secured behind the louver blades with clip angles and bolts. For filter maintenance simply unscrew the bolt, to allow the filter and its frame to come away from the Louver.
When calculating the Sand Trap Louver pressure drop Please add the pressure drop of the filter to the total pressure drop. Sand rejection performance of a sand trap louver depends on the manufacturer and its quality.
This sand trap louver (Shown in the images above), from an example brand is 80% effective at 1.0 metre per second draw velocity. Sand is blown on louver at 20 to 25 meter per second in the injection tube. The graph shown in the image above represents a sand trap louver tested for size 1220 mm x 1220 mm in size. The sand grating used is in between 76 micrometer to 699 micrometers as per AMCA standards. Based on this data, recommended draw velocity 1.0 meter per second draw velocity is the maximum used when sizing up sand trap louvers, to assure good performance.
The airflow performance of this example sand trap louver is as shown in the image below.
Free Area Velocity (m/s) = Air flow rate (metre cube/ second) / Free area (square meter)
With the help of these two charts shown below, one can easily find the area of sand trap louver.
To help you guys understand this in a simpler way, i will use a simple example to see how to find the free area of a Sand Trap Louver.
Example:
Find the Area of a Sand Trap Louver, who's air flow rate is 7400 cfm, and face velocity is 197 fpm. Let us see the solution for this example.
Solution:
We know the formula for free area velocity which is:
Free Area Velocity (m/s) = Air flow rate (metre cube/ second) / Free area (square meter)
Convert this equation to feet and minutes, and re-arrange the formula:
So, we will get,
Free area (square feet) = Air flow rate (cfm) / Free Area Velocity (fpm)
Now, let us substitute the values in the above re-arranged equation.
That is, we get,
Free area (square feet) = 7400 / 197
which will be equal to,
= 37.56 sq ft.
This is the Free area of the given sand trap louver. In order to find the actual area of the sand trap louver we need to convert this square feet area into square metre area.
Area in square meter = 37.56 / 10.76
which will be equal to,
= 3.49 square meter.
This is the free area in square meter of this sand trap louver. In order to find the actual area of the sand trap louver we need to go back to the free area charts posted above. so, let us go back to the free area charts and see how to calculate the actual area of the sand trap louver from these free area charts.
Let us try to locate the 3.49 sq meter free area that we got ,as we look into this chart below, we don't find 3.49, but we could locate 3.54 which is very near to 3.49. Always take a little higher value, never take a lower value. If you get the exact value, take it. But never go for a lower value ever. Locate on the dead end left of this 3.54, you will see 3920 mm. This is the actual width of the sand Trap Louver. Similarly, locate on the top end of the 3.54, you will see 2870 mm. This is the actual height of the sand trap louver.
Area of Sand Trap Louver = Length x Width
Whatever we found from that chart, we will substitute in this equation.
= 2.870 x 3.920
Here we have converted mm to meters.
So, Actual Area of Sand Trap Louver = 11.25 sq meter.
In this way, we can easily calculate, the area of any sand trap louver, with this easy method.
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