The “Design” functionality of Coils lets the user choose from a list of coils the best solution for a certain heat transfer and pressure drop requirement. But how does Coils generate the list of possible solutions? This will be discussed in the following document.

# How does it work

Basically the software performs an automated calculation with all possible combinations of these three parameters:

1. Number of rows
2. Fin pitch
3. Number of passes (or nr of tubes in series)

The first two parameters changes between the minimum and maximum values set by the user in the “Design profile” form. The third parameter instead changes between 1 and 14 (*) and it’s used to calculate the number of circuits with the following formula:

Nr of circuits = (Nr of tubes per row * Nr of rows) / Nr of passes

Where the Nr of tubes per row is set by the user in the input parameters.

# Examples

A few practical example of these values are:

Nr of Rows: 2

Fin Pitch: 2.1 mm

Nr of Tubes per Row: 32

In this situation, the number of circuits will vary from:

Nr of Passes: 1

Nr of Circuits = (32 * 2) / 1 = 64

To:

Nr of Passes: 14

Nr of Circuits = (32 * 2) / 14 = 4,57 = 5

Another example:

Nr of Rows: 3

Fin Pitch: 2.1 mm

Nr of Tubes per Row: 32

In this situation, the number of circuits will vary from:

Nr of Passes: 1

Nr of Circuits = (32 * 3) / 1 = 96

To:

Nr of Passes: 14

Nr of Circuits = (32 * 3) / 14 = 6,85 = 7

Another example:

Nr of Rows: 4

Fin Pitch: 2.1 mm

Nr of Tubes per Row: 32

In this situation, the number of circuits will vary from:

Nr of Passes: 1

Nr of Circuits = (32 * 4) / 1 = 128

To:

Nr of Passes: 14

Nr of Circuits = (32 * 4) / 14 = 9,14 = 9