Engineering Information

Most densely packaged electronic systems use a fan or blower for forced-air cooling. Smaller systems usually use axial cooling fans where airflow is perpendicular to the fan blades. However,larger systems may require centrifugal blowers to deliver adequate airflow in high static pressure situations.
The need for forced-air cooling should be determined at an early stage in system design. It is important that the design plans for good airflow to heat-generating components and also allows adequate space and power for the cooling fan.Factors to be considered in fan selection include: required airflow, AC or DC power, voltage, speed, life expectancy,EMI/RFI, heat dissipation, auto-restart and audible noise.
The first stage in designing a forced-air cooling system is to estimate the required airflow. This depends on the heat generated within the enclosure and the maximum temperature rise permitted.
AC input power is usually a good approximation of the power dissipated within the enclosure.
In estimating the power dissipated within a system, the possibility of future changes and additions of heat-generating subsystems should be allowed for. Therefore, the power
dissipation figure used should be a worst-case estimate for a fully loaded system.