www . refrigerationandaircon . co . za RACA Journal I November 2024 35
Professionals who care
By Michael Young , Pr . Eng .
MICHAEL YOUNG
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 8
What to consider when retrofitting to a ‘ greener ’ refrigerant in an existing system : Things to consider when using a DX system
When it comes to refrigerants , can we just change an existing system that uses R410A to a greener refrigerant like R513A ? Surely it can ’ t be that complicated to change the refrigerants as all you need to do is reclaim the R410A refrigerant and replace it with R513A right ?
To answer this , we first need to understand that each refrigerant has different thermodynamic properties such as density , specific heat , operating pressure and temperature .
So how does this impact the performance of the unit ? Firstly , the compressor is rated to provide a specific amount of cooling capacity for a specific refrigerant at a certain operating pressure and temperature .
When we change the refrigerant , the operating pressures and temperatures start to change as each refrigerant behaves differently . The density of the refrigerant also changes , which alters the mass flow of refrigerant that the compressor can circulate through the system , which in turn changes the cooling capacity of the compressor .
Since the operating temperatures of the compressor has changed , the cooling performance of the evaporator and condenser also changes as these components are sized according to the evaporating and condensing temperatures of the compressor .
So , in reality , what are the complications of retrofitting an existing cooling unit with another refrigerant ?
“ So , in reality , what are the complications of retrofitting an existing cooling unit with another refrigerant ?”
Firstly , the existing compressor may not be able to deliver the required amount of cooling capacity due to the changes in operating temperatures . Another implication could be that the compressor may no longer operate within a desired area of the compressor envelope which could lead to high power consumption or other complications that may cause the system to shut down .
The electronic expansion valve may need to be recalibrated or replaced as the existing valve may not be able to accommodate the new mass flow at the new operating pressure . The existing condenser and evaporator coils may not provide the required total heat of rejection or gross cooling at the new condensing and evaporating temperatures .
Refrigerant piping may need to be replaced as the operating pressure of the new refrigerant may be higher which will require a thicker line to be installed . The existing oil within the system may need to be changed to ensure the system performs in an optimal manner .
To answer this question , if the properties of the ‘ greener ’ refrigerant is identical to the existing refrigerant then you will be able to perform the retrofit with few problems . However , if the refrigerant properties are different , the system may not deliver the required cooling capacity and the system may consume more energy - and the warranty may no longer be honoured .
It is for these reasons that an existing unit is often replaced when the owner wishes to use a greener type of refrigerant as it is very seldom that both refrigerants have identical properties .
Wishing you a successful month ahead . RACA
www . refrigerationandaircon . co . za RACA Journal I November 2024 35