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SMALLER REFRIGERANT CHARGE In , for example , a supermarket application , traditional direct expansion systems circulate refrigerants through long pipe runs from the condensing unit through to the evaporators located within the cabinets in the shopping area . This type of direct expansion system utilises a fairly large refrigerant charge when compared to a chilled water system . More refrigerant piping means more opportunities for leaks and the greater amount of refrigerant in the systems means more refrigerant in the atmosphere when a leak occurs .
In the case of an indirect system , due to the refrigerant circuit being contained within the remote glycol chiller unit , the volume of refrigerant in the system is significantly reduced . In addition , the decrease in refrigerant volume can provide significant savings to the end user in the event of refrigerant loss .
INCREASED TEMPERATURE STABILITY Unlike direct expansion evaporators used in conventional refrigeration glycol systems use fully flooded cooling coils . Direct expansion evaporator coils use only a percentage of the cooling coil in the cooling process whereas glycol system cooling coils are 100 % filled with chilled glycol and therefore use 100 % of the cooling coil in the cooling process .
This results in faster temperature pull-down time , increased temperature holding times , and improved recovery times after defrost , ultimately resulting in improved end-user satisfaction . In a glycol cooling coil the temperature does not fluctuate as much as in a direct expansion evaporator , improving installation temperature stability .
Due to sensible heat being utilised , should a plant experience a power failure , brine gives a further advantage of a slower increase in installation temperatures . Due to a reduction in the system complexity on a glycol system , servicing and down times are reduced .
ENERGY COSTS Glycol refrigerant systems have a faster temperature pull down time , longer off cycles and shorter on cycles . This results in overall energy savings . Whilst a glycol chiller will also increase capital cost , the increase in capital cost can be offset by the reduced energy usage .
Khulani , I hope that this answers your question with regards to the usage of glycol in refrigeration and air conditioning systems .
REFERENCES : 1 . ACRA RACA
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RACA Journal I July 2021 www . hvacronline . co . za