## Total Flow Area (TFA) Total Flow Area (TFA) is summation of nozzle areas which fluid can pass through a bit. When you consider about the TFA, you need to count all nozzles that you have in a bit or a reamer. Basically, you can determine flow area with a simple circle area formula.

Flow Area = (π × D2) ÷ 4

Where;

Area in square inch

π is a constant which approximately equates to 3.14159.

D is diameter in inch

Let’s make it easier for our life. Normally, a diameter of nozzle is reported in xx/32 inch. For example, a bit has 3 nozzles and each one of them has size of 20/32 inch.

The formula above can be simplified like this.

## Oilfield Unit

Flow Area = N2 ÷ 1303.8

Where;

Flow Area for each nozzle in square inch

N is nozzle size in number/32 inch.

In order to find the total flow area of each bit or reamer, you must add all area of each nozzle.

Example

The bit that has a total of 5 nozzles. Three nozzles have a diameter of 10/32 inch and other 2 nozzles are 12/32 inch diameter.

Determine the total flow area (TFA) of the bit.

By the definition, you must sum every nozzle together in order to get the TFA; therefore, you can apply the formula above into this form.

Total Flow Area = (102 + 102 + 102 + 122 + 122 )÷ 1303.8

Total flow area = 0.451 square inch

## Metric Unit

Flow Area = N2 × π ÷  4

Where;

Flow Area for each nozzle in square millimeter

N is nozzle size in millimeter .

Example

The bit that has a total of 5 nozzles. Three nozzles have a diameter of 7.94 mm and other 2 nozzles are 9.53 mm diameter.

Determine the total flow area (TFA) of the bit.

Total Flow Area = (7.942 + 7.942 + 7.942 + 9.532 + 9.53 2 ) × π ÷  4

Total flow area =  291 square mm 