3.7.5.3 Evaporative Cooler

90.1-2016 BM

This is equipment that pre-cools the outside air that is brought into the building. It may be used with any type of cooling system that brings in outside air. This equipment is not applicable for the baseline building.

Evaporative Cooling Type

Applicability

Systems with evaporative pre-cooling

Definition

The type of evaporative pre-cooler, including:

  • None
  • Non-Integrated Indirect
  • Non-Integrated Direct/Indirect
  • Integrated Indirect
  • Integrated Direct/Indirect

An integrated pre-cooler can operate together with the compression or CHW cooling. A non-integrated pre-cooler will shut down the evaporative cooling whenever it is unable to provide 100% of the cooling required.

In all cases, the evaporative pre-cooler must be modeled with 100% of the outside air routed through the pre-cooler.

Units

None

Input Restrictions

As designed

Baseline Rules

Not applicable

 

Direct Stage Effectiveness

Applicability

Systems with evaporative pre-cooling

Definition

The effectiveness of the direct stage of an evaporative cooling system. Effectiveness is defined as follows:

(Equation 3.7.5.3-1)

$$DirectEFF=\frac{T_{db}-T_{direct}}{T_{db}-T_{wb}}$$

Where

DirectEFF

The direct stage effectiveness

Tdb

The entering air dry-bulb temperature

Twb

The entering air wet-bulb temperature

Tdirect

The direct stage leaving dry-bulb temperature

Units

Numeric

Input Restrictions

As designed

Baseline Rules

Not applicable

 

Indirect Stage Effectiveness

Applicability

Systems with evaporative pre-cooling

Definition

The effectiveness of the indirect stage of an evaporative cooling system. Effectiveness is defined as follows:

(Equation 3.7.5.3-2)

$$IndEFF=\frac{T_{db}-T_{ind}}{T_{db}-T_{wb}}$$

where

IndEFF

The indirect stage effectiveness

Tdb

The entering air dry-bulb temperature of the supply air

Twb

The entering air wet-bulb temperature of the “scavenger air”

Tind

The supply air leaving dry-bulb temperature

Units

Numeric, a value between zero and one

Input Restrictions

As designed

Baseline Rules

Not applicable

 

Evaporative Cooling Performance Curves

Applicability

Systems with evaporative cooling

Definition

A curve that varies the evaporative cooling effectiveness as a function of primary air stream airflow. The default curves are given as follows:

(Equation 3.7.5.3-3)

$$PLR=\frac{CFM_{operating}}{CFM_{design}}$$

$$EFF\_FFLOW=a+b\cdot PLR+ c \cdot PLR^{2}$$

where

PLR

Part load ratio of airflow based on design airflow

EFF-FFLOW

A multiplier on the evaporative cooler effectiveness to account for variations in part load

CFMoperating

Operating primary air stream airflow (cfm)

CFMdesign

Design primary air stream airflow (cfm)

a, b, c

Coefficients from Appendix H

 

Units

Data structure

Input Restrictions

User may input curves or use default curves. If defaults are overridden, the software must indicate that supporting documentation is required on the output forms.

Baseline Rules

Not appliable

 

Auxiliary Evaporative Cooling Power

Applicability

Systems with evaporative cooling

Definition

The auxiliary energy of the indirect evaporative cooler fan, and the pumps for both direct and indirect stages

Units

kW or kW/cfm

Input Restrictions

As designed

Baseline Rules

Not applicable

 

Evaporative Cooling Scavenger Air Source

Applicability

Systems with evaporative cooling

Definition

The source of scavenger air for an indirect section of an evaporative cooler. Options include:

  • Return Air
  • Outside Air

Units

List (see above)

Input Restrictions

As designed

Baseline Rules

Not applicable