Below are the questions asked during the event, along with their respective answers.
Q: Does a connector’s configuration or type impact flow values?
A: Yes, it can have a significant impact. Initial sizing as well as valving or shutoff configurations will influence the overall press loss. Directional variation may be observed when flowing from socket to plug and vise versa. Termination selections such as inline or elbow, tubing or thread will also impact flow.
Q: Is coolant selection your recommended first specification? (Then we specify wetted components after that…?)
A: Coolant is the logical place to start as it’s one of the most critical aspects of the overall system capacity and performance. Once the coolant is identified, the other pieces can start to fall into place. Understanding the entire wetted materials list is also key to ensuring long term compatibility and reliability.
Q: How severe is the global warming potential of some of these fluids (especially the FC candidate fluids) in end customers adopting these fluids?
A: Ultimately it depends on the overall size of the system, the operating environment, and the geographical location. Some regions might have differing regulations around GWPs and environmental factors. When considering some of the FC fluid candidates it’s generally important to ensure a closed system so that none of the fluid can escape. Additionally, many new fluids are hitting the market that address the GWP and OCP concerns like HFEs and some of the new 4th generation refrigerants like HFOs.
Q: What polymer composition is best suited for sealing on sliding surfaces? Are there special additives or formulations that have low friction and low wear?
A: Generally the sealing friction can be associated with of course the condition of the mating surface, the compression on the seal, and any lubricant that might be present. In dynamic sealing applications, controlling the amount of compression on the seal to ensure leak tightness, but not increasing it so much that significant drag is developed. As for additives or formulations that have low friction properties, yes elastomers can be compounded with a variety of materials and fillers such as wax or PTFE to provide internal lubricity.
Q: Do the polymer seals slide easier on metal or plastic surfaces you use?
A: In these types of dynamic applications it really comes down to lubrication, surface finish, and compression. Balancing those all to promote effective sealing, while also facilitating low friction movement. Controlling surface finishes especially with machined metal components is certainly important.
Q: Are the QDs UL certified for refrigerants?
A: There are some recent developments in accelerating testing for QDs in new refrigerant applications. Leveraging some of the data and test methodology from the HVACR industry such as UL207 can be useful when considering QDs for these applications. If there are specific certifications or tests needed, reach out to a QD supplier like CPC to discuss.
Q: Great Presentation. Have you seen situations in which another wetted material from a flow loop, an elastomeric hose, for example, caused fluid contamination that in turn caused a QD elastomer to fail?
A: We have conducted experimental comparisons with un-ducted flow as part of the development of the tool. In all of the validated cases, the results were verified within the 3-7% error range. Examples are not yet published.
Q: How does constant rotation of the connection impact sealing capabilities?
A: In dynamic sealing applications, either linear sliding or rotary motion – friction will impact the overall ability to seal over time. Repeated cycles under high friction loads due to thermal swelling, improper specification, lack of lubrication, etc can lead to failures and leaks. Mitigating those risks with proper design and understanding the requirements upfront can ensure long term reliability of dynamic sealing applications.