Specialists in glycol refrigeration engineering for commercial and industrial applications. We have extensive experience in the design, maintenance and repair of secondary glycol refrigeration systems.
Glycol Refrigeration
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Conventional Direct Expansion Refrigeration
Whilst glycol refrigeration systems have been used for some time, recent changes to refrigerant pricing, environmental concerns and commitment to sustainable refrigeration approaches has seen the popularity and benefits of glycol refrigeration systems increase significantly. Glycol is a totally food safe, nonhazardous liquid which is mixed with tap water, chilled in a glycol chiller unit and pumped around a closed loop to all refrigerated spaces and processes (cool rooms, fridges, process coolers etc).
The equipment and plant design
A conventional direct expansion system includes a condensing unit usually located externally to the remote refrigerated spaces (cool rooms, fridges, etc.). The condensing unit rejects heat from the refrigerant and circulates refrigerant to all of the refrigerated spaces. When the refrigerated space requires cooling a digital temperature control instructs a solenoid valve to open which allows for liquid refrigerant to flow into the evaporator and start the direct expansion cooling process.
A glycol refrigeration system is made up of 2 sub-systems often referred to as a secondary loop system. Stage 1 of the system is a direct expansion system which chills the liquid glycol utilised in stage 2 of the process. The chilled glycol is then pumped to all refrigerated spaces and processes. When the refrigerated space requires cooling a digital temperature control instructs a glycol flow valve to open which allows chilled glycol to flow through the evaporator and start the cooling process.
The benefits of glycol refrigeration systems
Future flexibility of the refrigeration plant
Due to the global warming potential of convention synthetic refrigerants commonly used in most commercial refrigeration systems it is expected that the industry will experience a large shift in the coming years to greener refrigerants. These new generation of refrigerants however also carry certain properties that make them potentially flammable or highly toxic. For these reasons they cannot be retrofitted into existing conventional refrigeration systems without significant modifications to the entire system. A large number of conventional systems will not be able to be retrofitted with new generation refrigerants due to the potential risks involved. This means the system is locked to running on conventional refrigerants which will rise steadily in price as the demand and supply decreases.
A glycol system however isolates the refrigerant inside the glycol chiller unit located in a remote location (roof or plant room etc.) This makes them ideal for retrofitting with the new generations of refrigerants in the future with minimal system modification and without the need to modify any of the existing glycol circuit.
Increased temperature stability and product quality
Unlike direct expansion evaporators used in conventional refrigeration systems, glycol systems use fully flooded evaporator coils. Direct expansion evaporator coils use approximately 65% of the cooling coil in the cooling process where as glycol system evaporators are 100% filled with chilled glycol and therefor 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 / perception, increased product shelf life, reduced wastage and fresher product.
The constant temperature of the glycol also minimises air dehydration which reduces product wastage through drying out.
Significant reductions in the total system refrigerant volume
Due to the refrigerant circuit being contained within the remote glycol chiller unit the volume of refrigerant in the system is significantly reduced. The decrease in refrigerant volume can provide significant savings to the end user in the event of refrigerant loss through leaking components etc.
In additional to this by containing the refrigerant circuit to the glycol chiller, the points of failure causing a refrigerant leak to occur are significantly less.
Reduction in maintenance, servicing and downtime costs
Due to a reduction in the system complexity and failure points on a glycol system servicing and down times are reduced. By isolating the refrigerant plant to the glycol chiller unit maintenance costs are also reduced. Failures in a glycol system on one refrigerated space (coolroom or fridge etc.) are unlikely to effect the integrity of other refrigerated spaces on the system.
Reduced energy costs
Glycol refrigerant systems have approximately 33% faster temperature pull down time, 50% longer off cycles and 50% shorter on cycles. This results in overall energy savings of up to 25%. Often self-contained refrigerators are specified due to the complexity and capital cost of installing a larger refrigeration system to service an entire installation. Whilst a larger glycol chiller will also increase capital cost, the system complexity does not differ and the increase in capital cost can be offset by the reduced requirement and energy usage for heat extraction, ventilation and air conditioning.
Disclaimer : All figures stated on this page are indicative only and will differ dependant on the size of the systems compared, configuration of the systems compared and many other factors. For expert advise on your particular applications please feel free to contact us.
Glycol refrigeration system limitations
Glycol refrigeration systems are limited to servicing refrigerated spaces above 0 degrees C. Glycol temperature generally runs about 8 degrees colder (usually -8° C) than the required refrigerated space temperature. The properties of glycol when it is chilled to very low temperatures below -10° C make it unsuitable for use in refrigerated space applications below 0° C.