www . refrigerationandaircon . co . za RACA Journal I January 2024 39
Professionals who care
MICHAEL YOUNG
Contributed by Michael Young , Pr . Eng .
Michael Young is a trainer , coach and a pre-sales engineer in the HVAC industry . He graduated from the University of the Witwatersrand in the field of Mechanical Engineering ( B . Sc Mech Eng ) in 2008 and qualified as a Professional Engineer ( Pr . Eng ) in 2013 . Michael is passionate about promoting knowledge and helping other young engineers grow within the industry through his training workshops and coaching sessions .
HOW TO COOL THE DATA CENTRE IN THE 21ST CENTURY
Part 3 : The impact of using a “ greener ” refrigerant in a cooling system .
The focus of sustainability within the data centre industry has led to the implementation of new cooling technologies and the use of alternative and green refrigerants .
Use of a specific refrigerant within the data centre space needs to consider flammability and toxicity while capacity difference needs to be considered within the design of the central cooling unit .
The design of a cooling unit that uses an alternative refrigerant can become a complex exercise as the condenser , evaporator and compressor need to be reassessed .
So how does the use of an alternative refrigerant impact the compressor ? The compressor can often be described as ‘ the heart ’ of the HVAC system , whereby the compressor moves the refrigerant through the system and also raises the pressure of the refrigerant gas once it leaves the evaporator .
When suppliers select a specific compressor , they first define the operating evaporating and condensing temperature . These temperatures are selected according to the type of cooling application .
A data centre cooling system is designed to provide
sensible cooling and will operate at a higher return air condition compared to comfort cooling . To accomplish this requirement , the evaporating temperature of the compressor will also be higher .
To reduce energy consumption , the condensing temperature of the compressor will be as low as possible , taking into consideration the ambient air temperature on site and the optimal size of the condenser .
Once the condensing and evaporating temperatures have been defined , the operations of the compressor are reviewed by looking at the compressor envelope . The goal is to find the optimal condensing and evaporating condition that meets the requirements of the data centre while operating with the lowest energy consumption .
So how does refrigerant play a role within the operation of the compressor ? Each refrigerant has a different density and pressure-temperature relationship . Density influences cooling capacity while pressure-temperature changes the operating point on the compressor envelope .
Therefore , it is possible that a specific compressor will operate efficiently with R134A but cannot be used with R410A due to operations outside of the compressor envelope or excessive operating pressures .
Cost also needs to be taken into account as loss of cooling capacity means the units have to increase in size which results in a higher capital cost . While it is desirable to develop low GWP , low flammable and low toxicity refrigerants , the impact on the cooling performance , energy consumption and capital cost for the data centre application needs to be considered .
It is not easy to replace the refrigerant within a cooling system as there are many factors to consider , and this is the primary reason why the use of a newly developed refrigerant can take months or years to implement .
To learn more on how refrigerants impact a cooling system drop us an email on michael @ myengineeringcoach . co . za and I look forward to seeing you in next month ’ s publication .
Wishing you a successful month ahead .
RACA
“ The compressor can often be described as ‘ the heart ’ of the HVAC system whereby the compressor moves the refrigerant through the system .”
www . refrigerationandaircon . co . za RACA Journal I January 2024 39