Direct Research Special

This cooler is similar in principal to the Direct CelDekPad. The model differs in that it gives the user a simple way of specify the cooler effectiveness. Using the Research Special input object also allows the cooler to control the amount of cooling based on node setpoints, controlled by Setpoint managers. This avoids problems from over cooling when conditions are such that loads are low and cooling power is high. Water pump power is assumed to vary linearly when the cooler is operating at less than full capacity.

General

Name

A unique name for an instance of an evaporative cooler which is predetermined by DesignBuilder.

Settings

Cooler effectiveness

This field specifies the effectiveness that is applied to the wet-bulb depression to determine the conditions leaving the cooler. This model assumes that the effectiveness is constant.

Drift loss fraction

This field is optional and can be used to model additional water consumed by the cooler from drift. Drift is water that leaves the cooling media as droplets and does not evaporate into the process air stream. For example, water may get blown off the evaporative media by winds and escape the air system. The value entered here is a simple fraction of the water consumed by the cooler for normal process evaporation. The amount of drift is this fraction times the water evaporated for the normal cooling process. This field can be left blank and then there will be no added water consumption from drift.

Recirculating water pump power consumption

This field is used to specify the power consumed by the water pump that circulates water (in W).

Blowdown

Blowdown On

Select this option to model additional water consumed by the cooler from blowdown. Blowdown is water that is intentionally drained from the cooler’s sump to offset the build up of solids in the water that would otherwise occur because of evaporation.

Blowdown concentration ratio

The value entered here is dimensionless. It can be characterized as the ratio of solids in the blowdown water to solids in the make up water. Typical values are 3 to 5. The default is 3.0.

Operation

Availability schedule

Schedule that defines when the coil is available, i.e. whether the evaporative cooler can run during a given time period. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during a given time period. A value less than or equal to 0 (usually 0 is used) denotes that the unit is off.