For the purposes of determining refrigerant inventory in a system, we will focus on the normal operation and not the abnormal operation; however, the inventory under abnormal operation should be considered in the context of risk assessments and condenser siting.
Select “Specify Inventory” if you have the manufacturer data available.
In the event that operating charge data is not readily available, select “Specify Heat Rejection.” Two other rules-of-thumb can be applied to estimate evaporative condenser refrigerant inventory. The first rule-of-thumb says that the average density of refrigerant in the condenser heat exchanger is ~10 lbm/ft3. The condenser inventory is then the coil volume times that average density. The second rule-of-thumb says that a reasonable average charge is 90 lbm per million Btu/hr of rated heat rejection at a manufacturer’s specified condition.
Note: The rate of heat rejection is based on a 96.3 °F saturation temperature (a saturated suction temperature of +20 °F for an outdoor air wetbulb temperature of 78 °F).
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