How to make components for CO2 as refrigerant (Simple)

Most with insight into refrigerants will tell you there is no silver bullet refrigerant. I concur. You may recently have heard that the upcoming Covid 19 vaccine needs to be stored at very low temperatures. Here we are talking below 70 degree C according to some news...here maybe a refrigerant like Ammonia (R717) and CO2 (R744) are not as suitable as e.g. Air (R729).

With that out of the way lets have a look at CO2..

CO2 is an excellent solvent which may challenge engineers in their material choice while at the same time running CO2 in an application very often may provide challenges in regards to pressure..... at least compared with some of the other widely available refrigerants and the MWP (Max Working Pressure) they may strain the system with.... HFC and HFO lovers will use this argument a lot. And do not be mistaken pressures of compressible fluids in refrigeration systems etc. is to be taken serious. There is a good reason why we at Juutac think the PED (Pressure Equipment Directive) is a good thing. Our founder Anders have blown a significant amount of valves to pieces over the years to test if the simulated/calculated burst pressures were as predicted and designed for ;-) 

Mechanical components

So it is pretty straight forward doing mechanical components for CO2 refrigeration, Air conditioning and heatpump applications. Just make sure you understand the following fundamentals:

1. Pressures at the product. MWP and differential pressure across the product

2. Flow characteristics. Do not get surprised if noise, and difficult jet streams will challenge your product in sensitive regulating areas as example

3. External and internal leakage requirements... a good place to start looking is at EN 378-2 and the associated component standards as EN 12284 for valves...if I do not recall incorrectly. Of course here this is a more trickier part than how it looks. Tightening with the right polymers if that kind of assembly is chosen is key, and are we talking valves the tradeoff between # on/off vs. tightness one will always face.

4. Temperatures Ambient and internally

5. Of course trivial but still needed things to consider is also. connection types, oil in system, means of actuation if any, life time expectancy, serviceability etc.

So you see straight forward.

Electronic components

Doing electronic components...and let us here for simplicity of the blog look this time around on controllers and not e.g. Frequency converters to drive say Compressors or fans. Here there are also a few basics to get right. and we do it very top level only today. 

1. Always always make sure that the application you want to support running CO2 as refrigerant is understood 100% by your lead engineers overseeing the hardware and software development.

2. Understand the transcritical part of regulating very well and make sure you double check the patents out there.

3. Speed...and even more speed of your processing of code can be essential. CO2 as refrigerant may make you system fairly aggressive, and if then at the same time the application has been build with e.g. small receiver in relation to the charge of system (due to cost) you want your actuation of valves and compressors to be rapid so that you do not need to cut out on high pressure, and then depending on your safety set need to do some resetting before you are up and running again.

4. Communication. The world is getting connected...it already is ..;-) so are your application running CO2. Make sure you have competent electronics capable of communicating broadly so that the end user have an easy task monitoring and acting on data, that will allow for safety of food preservation as example, but just as important for optimum energy performance in coexistence with say heat recovery systems etc.

Summary

For most of you reading here, the above may be obvious. the intention is to give you inspiration to have the technical side covered when specifying a product/component.