How to Arrange Chillers?

The chiller supplier introduces how to combine multiple chillers for use in a variety of combinations, piping and control methods, which usually constitute a chiller room.

Single chiller arrangement

In its simplest form, there is only one chiller providing chilled water to the building's coils. The chilled water can be cooled by water or air cooling. Without regard to the cooling medium, a single chiller has certain features in common with a combination of multiple chillers.

These features include, among others, variable flow regulation of chilled water, energy-efficient operation, control methods, and typical operating procedures. 

First, let us understand some basic principles as follows.

1. Water flow rate variation

2 . Energy consumption

3 . How to control chillers

4 . The general sequence of operation

Water Cooled Scroll Chiller

For the variation of flow rate

The design operating water flow rate of the chiller plant is 3fps to 12fps. Within this flow rate range, the water flow in the tube is in turbulent state and the performance is good, and the heat transfer achieves the expected effect. When the flow rate inside the tube is lower than 3fps, the flow becomes laminar, and the operation of the heat exchanger will not achieve the expected effect and the performance is unstable. The operation of the chiller unit will be unstable. 

Therefore, the flow in the tube must be outside the laminar region to ensure reliable and good operation.

Although the heat exchanger design requires a maximum flow rate of 12 fps, the system must be designed to account for pressure drop, so the designer should take steps to ensure that the pressure drop is 20 to 30 inches of water column. Generally speaking, this will leave the flow rate in the tube between 8 and 10 fps.

Therefore, the chiller may have a laminar flow of load percentage between 30% and 38%. Here it is taken as 40%. Thus, it is best to keep the operating load of the chiller unit at no less than 40% to ensure good and reliable operation of the chiller unit.

 Air Cooled Screw Chiller   

Chiller heat exchanger flow rate range - (3 < velocity < 12 ft/sec), typically 8 to 10 fps.

The design operating water flow rate of the chiller is 3 fps to 12 fps. Within this flow rate range, the water flow in the tube is in a turbulent state with good performance and the heat transfer achieves the desired effect. When the flow rate inside the tube is lower than 3fps, the flow becomes laminar, and the operation of the heat exchanger will not achieve the expected effect and the performance is unstable. The operation of the chiller unit will be unstable.

Therefore, the flow in the tube must be outside the laminar region to ensure reliable and good operation.

Although the heat exchanger design requires a maximum flow rate of 12 fps, the system must be designed to account for pressure drop, so the designer should take steps to ensure that the pressure drop is 20 to 30 inches of water column. Generally speaking, this will leave the flow rate in the tube between 8 and 10 fps.

Therefore, the chiller may have a laminar flow of load percentage between 30% and 38%. Here it is taken as 40%. Thus, it is best to keep the operating load of the chiller unit at no less than 40% to ensure good and reliable operation of the chiller unit.

Chiller heat exchanger flow rate range - (3 < velocity < 12 ft/sec), typically 8 to 10 fps.

When less than 3 fps causes laminar flow and automatic shutdown - this means (3/10) x 100 = 30% to (3/8) x 100 = 38% flow, which generally must bring the unit flow above 40%.