Hi,
I am looking for cold plate for my experiment. I have check one DigiKey and interesting in cold plate code 120964 and i have some question regarding this.
- What is the maximum working pressure for this cold plate?
- Can this cold plate be used with refrigerant (R1234yf) as the coolant?
- What is the maximum heat absorption capacity (in watts) of model 120964?
- I am planning to use this cold plate to vaporize a refrigerant under the following conditions: Mass flow rate: 0.0243 kg/s
Operating pressure: 20 bar
Heat will provide by the heater at 100 -120 C
Based on these conditions, can this cold plate operate safely and effectively in my application? Thank you very much for your assistance. I look forward to your reply.
Hello,
Welcome to the DigiKey TechForum. You can use refrigerant with this cold plate as listed on page 1 of the datasheet . Here is the performance graph for the 6 pass, 24 inch plate showing flow rate in gallons per minute to pressure drop in psi. You will need to verify with this information if this will work for your application.
1 Like
Thank you so much.
What about the maximum working pressure for this cold plate?
(1) The datasheet does not specify a maximum working pressure for the cold plate, but does indicate that the tubing used is 3/8" type K copper. Various sources indicate a working pressure for this material in the neighborhood of 60 bar in the annealed state, but this figure may be affected by forming operations such as bending.
(3) This depends on several things including the heat transfer properties of the working fluid, acceptable temperature differences within the system, to which side of the cold plate the heat source is mounted, how the heat source is distributed across the surface of the device, and several other things. The performance figures given for water as a working fluid could be used as a staring point for estimation, but it would be up to you to determine if the device will meet your needs under your specific conditions of use.
(4) Lots of information is still missing, but if I read the refrigerant chart correctly, the boiling point of R1234yf is approximately 70°C at 20 bar pressure with approximately 100kJ/Kg change in enthalpy between liquid and vapor states. This suggests roughly a 2.5 kW thermal transfer rate for a 30°C temperature difference, or a thermal resistance of approximately 0.012°C/W. This seems in the neighborhood of what can be expected from the device when using water as a working fluid.
All that said, if I understand correctly the application is vaporizing a refrigerant that is already at a high temperature. This seems unusual, since most of the time people are interested in using refrigerants for refrigeration…
1 Like
Thank you so much. Your information is really helpful. I also have other question to confirm with my operating condition.
I would like to confirm the maximum allowable temperature difference between the cold plate and the heat source, based on the cold plate’s design limitations. Specifically, is it acceptable for the design temperature difference to reach up to 50 °C?
My system operates on an ejector refrigeration cycle, in which the refrigerant undergoes vaporization at both low and high temperatures. The resulting vapor streams are mixed within the ejector before being condensed in the condenser. The cold plate will be used on the high-temperature side to facilitate the vaporization process.
I haven’t been able to find a solid answer on this so far. On the face of it this doesn’t strike me as unusual, but there aren’t any ratings given for maximum allowable temperature and the like.
I’m curious to see what rick_1976 has to say, as he has more experience with these, but I may have to reach out to the manufacturer for clarification.
1 Like
I find no mention in the datasheet of limitations on this point. This would suggest that studies of device behavior in this area are limited, and that it would be up to the user to evaluate it under their specific conditions.
To maintain a 50°C difference between heat source and inlet fluid temperature would imply a rather large heat flux through the device, which brings the potential for rapid, large temperature changes that may (or may not) cause problems due to differences in expansion coefficient among the different materials involved. Rate of temperature change, uniformity of heat application, number of thermal cycles, all of these things could potentially be factors in long-term device performance. Considering the number of variables that are potentially involved, it becomes impractical for the manufacturer to characterize the device under conditions that might represent a small minority of potential use cases.
Also, a working fluid that vaporizes during the process will also behave differently from one that remains liquid throughout; there’s nearly 4 meters of rather narrow tube in the device, and getting vapor bubbles through that without some liquid coming along for the ride may prove troublesome, if that’s the desired result.
2 Likes
Thank you very much for your response.
I would like to provide more details regarding my operating conditions, as they are somewhat more complex. The cold plate in my system will be exposed to both single-phase and two-phase boiling, with a refrigerant mass flow rate of 0.0243 kg/s. The operating conditions are as follows:
- Single-phase boiling: Inlet temperature at 35 °C and outlet at 70 °C.
- Two-phase boiling: Inlet temperature at 70 °C (saturated).
- Superheated vapor phase: Temperature rise from 70 °C to 90 °C.
Initially, I planned to apply a heat source temperature of 100 °C or 120 °C to a cold plate connected in series, with the goal of providing uniform heating throughout the process. However, based on your earlier comments, I am now concerned that this setup may not be feasible, as the temperature difference between the heat source and the refrigerant inlet could range from 65 °C to 85 °C, which may exceed practical or tested limits.
I am now considering an alternative approach of connecting three cold plates in series, each with a different heat source temperature, to better manage the thermal load at each stage of the process.
For context, my name is Liyean Soeun, and I am a master’s student conducting this experiment for academic purposes. I fully understand that several factors can influence the system’s performance, but I would greatly appreciate any comments or suggestions you may have regarding the feasibility of this approach or potential limitations.
Thank you once again for your time and guidance.
The experimental setting allows for the luxury of being able to over-build things and only needing them to last until the experiment is over. Giving oneself some working room in terms of multiple heating stages and more transfer area might be a reasonable idea, as well as offer an opportunity to monitor and control different parts of the process independently.
Two things that I might suggest would be to evaluate the expected pressure drop across the cold plate(s) at the flow rate desired, and to provide a means of phase separation at the output of the second phase above. It’s been 20 years since I did any serious fluid mechanics work so I wouldn’t trust myself to offer estimates on the pressure drop, but intuitively it seems that 24g/s might be quite a bit of flow to push through several meters of 3/8" tube while evaporating it in the process.
At the very least, generating vapor at that rate in a single-tube system will have a tendency to push liquid into places where one doesn’t want it due to buoyancy and entrainment effects. The steam dome on old traction engines was there to allow gravity separation of liquid and vapor, and something similar after your vaporization stage ((2) above) would seem likely to be helpful so that one doesn’t end up with a bunch of liquid blurping into the superheat stage. Aside from that, being able to control the amount of superheat applied might be a useful experimental variable.
If there are concerns about the pressure tolerance of the experimental setup, hydrotesting the system may offer some assurances on that front. This involves filling the system with an incompressible fluid and pressurizing it to some level in excess of the expected working pressure, to demonstrate the mechanical integrity of the system without risk of explosive rupture that compressed gasses present. (150% of rated working pressure is a common figure used by those of us that drive old steam engines of the sort pictured)
2 Likes
