Equipment efficiency versus system efficiency has always fascinated me. While we often focus on equipment efficiency to save energy, it’s important to consider other factors as well. Selection of equipment and system resistance are equally important in achieving energy savings. Let me elaborate with an example of a blower in an AHU.
There are three types of blowers commonly used in AHUs or air washers – axial (MXC/TDC), plug type (BNC), and centrifugal (ADA) – all with similar flow rates and static. While text book efficiency rates ADA as the highest, followed by BNC and axial, it’s important to consider how much of the AHU area is utilized in all three cases and the resistance offered by the equipment itself while air is flowing through it. The resistance offered by the blowers is higher in centrifugal, followed by BNC and least in axial.
Even in the axial fan, using a higher diameter and lower RPM will result in lower pressure drop and power consumption. Therefore, the key is in selecting the right blower/fan and the size (cross section) of the AHU.
In fluid flow, power consumption is a function of flow and pressure drop (static), while flow is a process requirement. However, the pressure drop is totally dependent on our selection and design. After comparing data from over 100 AHUs involving large, medium, and small AHUs and air washers, and all three types of blowers/fan for similar applications, I would give equal weightage to all three factors – equipment efficiency, selection (type and size), and system (AHU cross section).
Remember, when it comes to energy savings, it’s not just about equipment efficiency. It’s about selecting the right equipment and system resistance (increasing area & lowering velocity) as well. All 3 have the same weightage.
Milind Chittawar
CEO
SEE-Tech Solutions
milind.chittawar@seetechsolutions.in
9422145534