EvaporativeCooler:Direct:ResearchSpecial
Used in:
- Air Handling Units
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Used in:
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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.
The model allows the effectiveness to be vary depending on the primary air flow rates. The design effectiveness can be modified by multiplying by an Effectiveness flow fraction modifier curve. The flow fraction is the ratio of the current primary airflow rate to the design flow rate. The recirculating and spray water pump power is assumed to vary with the primary air flow. The design pump power is modified using user specified pump modifier curve value. The normalized pump power modifier curve is a function of primary air flow fraction as a independent variable.
Also the direct evaporative cooler operating range can be controlled depending on the entering air dry bulb and wet bulb temperatures. The operating range can be controlled based on minimum and maximum inlet node air temperature limits. The evaporative cooler can be turned on or off depending user specified minimum and maximum temperature limits. If the inlet node entering air temperature is lower or higher than the minimum and maximum limits, respectively, then the evaporative cooler is turned off. The operating range control feature is primarily intended for application in data centres.
A unique name for an instance of an evaporative cooler which is predetermined by DesignBuilder.
Select the type of evaporative cooler from the list of options:
This autosizable setting is the primary air design air flow rate (in m3/s or ft3/min). If the evaporative cooler is on main air loop branch, the design flow rate is the same as branch design flow rate, or else if it is on outdoor air system it will be the maximum of the outdoor air design flow rate and the half of the primary air flow rate on the main air loop branch.
This setting specifies the effectiveness of the cooler at design flow rate that is applied to the wet-bulb depression to determine the conditions leaving the cooler. This model assumes that the effectiveness can vary with supply air flow rate. For effectiveness variation with supply air flow fraction enter the Effectiveness flow ratio modifier curve below. The flow fraction is the ratio of the sum of current primary air and secondary air sides flow rates and the sum of the design flow rates.
If an Effectiveness flow ratio modifier curve (below) is to be specified then check this checkbox. If this option is not checked then the effectiveness is assumed to be constant.
This curve modifies the Cooler effectiveness design value (above) by multiplying the value by the result of this curve. The modifying curve is a function of flow fraction, which is the ratio of the current primary air flow rates divided by the design primary air flow rates. Any curve with one independent variable can be used. Select a curve from one of these categories:
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.
This is the nominal water recirculating and spray pump power of evaporative cooler at primary air design flow rates and cooler design effectiveness. This setting is autosizable.
This numeric input field value is recirculating water pump sizing factor (in W/(m3/s) or W/gpm). This field is used when the previous field is set to autosize. The pump design electric power is scaled with Secondary Design Air Flow Rate. The default value is 90.0 W/(m3/s), i.e. Pump power / Primary air design flow rate = 90 W/(m3/s). Typical values range from 55.0 to 150.0 W/(m3/s).
Select this option to apply a Water pump power modifier curve. If this option is not checked then the pump power is assumed to vary linearly with the load.
Select a dimensionless normalized pump power modifying curve. This curve modifies the pump electric power by multiplying the design power by the result of this curve. The normalized curve is a function of the primary air flow fraction as independent variable. The curve generates a value of 1.0 at a flow fraction of 1.0. The flow fraction is the ratio of the primary air during current operation divided by Primary design air flow rate. Any curve with one independent variable can be used. Select a curve from one of these categories:
To define a dry-bulb temperature lower limit for evaporative cooler operation check this checkbox. Otherwise, if this option is unchecked then there is no dry-bulb temperature lower limit for evaporative cooler operation.
Minimum limit dry-bulb temperature
This setting defines the evaporative cooler inlet node dry-bulb temperature minimum limit (in °C or °F). The evaporative cooler will be turned off when evaporator cooler air inlet node dry-bulb temperature falls below this value. The typical minimum value is 16°C.
To define a wet-bulb temperature upper limit for evaporative cooler operation check this checkbox. Otherwise, if this option is unchecked then there is no wet-bulb temperature upper limit for evaporative cooler operation.
Minimum limit dry-bulb temperature
This setting defines the evaporative cooler air inlet node air wet-bulb temperature maximum limit (in °C or °F). When the evaporative cooler air inlet node air wet-bulb temperature exceeds this limit, then the evaporative cooler is turns off. The typical maximum value is 24°C.
To define a dry-bulb temperature upper limit for evaporative cooler operation check this checkbox. Otherwise, if this option is unchecked then there is no dry-bulb temperature upper limit for evaporative cooler operation.
Maximum limit dry-bulb temperature
This setting defines the evaporative cooler air inlet node dry-bulb temperature maximum limit (in °C or °F). The evaporative cooler will be turned off when the evaporative cooler air inlet node dry-bulb temperature exceeds this value. The typical maximum value is 28°C.
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.
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.
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.