SynJet® Cooling Technology FAQ’s
- What is a SynJet®?
A SynJet is a high reliability fanless air mover that is used for thermal management. SynJet is short for Synthetic Jet which is a turbulent pulse of air that is more effective at removing heat than steady laminar (fan) flow.
- Are there any moving parts inside the SynJet®?
There is an oscillating diaphragm, but there are no friction or wear surfaces. There are no bearings or valves to wear out.
- Are there valves inside the SynJet®?
No. SynJets work like human breathing – the air is drawn in and out through the same opening in the internal cavity and no valves are needed.
- The SynJet® does not seem to generate very much airflow?
This is one of the benefits of SynJet cooling, it is very effective. SynJet flow is more efficient in removing heat than the typical flow in other forced air systems, so less than half the airflow of a laminar (fan) system is required to achieve a comparable cooling level.
- Why is the SynJet® more effective?
First, the SynJet turbulent air pulses are aimed directly into the heat sink fin channels. As the turbulent air pulse from the SynJet travels down the heat sink fin channel, it strips away the boundary layer of hot stagnant air next to the fin surface. Second, the turbulent pulse acts much like a large truck passing by, creating a low pressure area behind it. The low pressure area sucks cool ambient air into the fin channel behind the turbulent pulse. The hot stagnant air is replaced by cool air, thus heat can more easily transfer from the fin surface. With a traditional fan air mover, the heat sink fin channel presents a high flow resistance path to the air, so the air flow tends to try to go over or around the heat sink, not through the channels.
- Does the SynJet® inhale the hot air back inside itself?
No. Due to the jets’ high momentum and velocity, the jets carry the hot air through the heat sink and away from the SynJet inlet. The best way to illustrate this is via human breathing. Imagine that you are trying to blow out a candle. If you exhale sharply, it will blow out. Notice that your breath can be felt very far from your face. Now inhale just as sharply; the candle does not even flicker. All the air that you inhale comes from very close around your face. The same physics apply to SynJets. See an animation of how a SynJet® works.
- SynJet® mechanics are sometimes compared to a speaker, how are they different?
A speaker is made for reproduction of sound. A SynJet is a high reliability air mover designed to be silent. Its design has been optimized for operation over a broad temperature range, and for best thermal and acoustic performance while operating over a range of frequencies much narrower than the usual audio spectrum.
- Can I control the SynJet® actuator frequency and displacement?
The operating parameters are selected and optimized for your application. However, if you want to control the cooling level (the thermal resistance) of the SynJet cooler, this can be accomplished by similar control methods as fans (i.e. dc control voltage, digital control, serial port, logic levels, PWM, etc.).
- What is the SynJet® operating frequency?
The typical operating frequency for standard products is 40 to 70 Hz. However, we have developed custom products that can operate at higher frequencies.
- Does a P-Q curve exist for SynJets®?
There is no need for a P-Q curve because SynJets are not system air movers. SynJets are coupled with an optimized heat sink or Nuventix can design a custom heat sink for you.
- How do I model with SynJets® using a CFD tool such as ICEPAK or Flotherm?
Using commercial CFD code to model synthetic jet fluidic behavior is uncertain and the results are likely to be inaccurate so it is not recommended to make design decisions using CFD modeling. Nuventix is continuing to advance SynJet modeling capabilities and is working towards providing guidelines and/or code within a commercial CFD program to simulate SynJet devices. However, in the majority of applications customers are able to request a specified thermal cooling performance (°C/W), an acoustic (dBA) requirement and a dimensioned mechanical envelope and we are able to offer either one of our standard products, or, depending on the business case, develop a customized solution.
SynJet® Reliability and Testing
- Are SynJets® reliable?
Astoundingly so. SynJet products are rated for an L10 of 100,000 hours per cooler. L10 is defined as the point of time at which the cumulative failures of a product reach 10% and 90% remain functioning as intended under stated conditions. Nuventix has a state-of-the-art Reliability Lab in-house and a dedicated Reliability engineering staff. For specific SynJet tests and results, see the SynJet Reliability Report.
- How do dust and other particulate contamination affect SynJet® performance?
SynJets provide equal cooling with less than half the airflow of other forced-air systems; this means that there is less air moving through a SynJet. Less contaminant inhalation, in conjunction with the high velocity and turbulence of a SynJet, results in no significant dust build-up even after extended operation in a dusty environment.
- Do SynJets® produce excessive vibration?
Standard products have been benchmarked against other air movers and typically have less vibration.
- How is the SynJet® affected by vibration?
SynJets have been subjected to various shock/vibration profiles (sine sweeping, sine dwelling and random). The various levels of these tests are detailed on page 9 of the SynJet Reliability Report. If you have specific shock or vibration requirements, Nuventix sales team can evaluate those requirements to identify if there would be a risk in operating the SynJet in that environment.
- Are SynJets® UL approved?
SynJet coolers have been UL recognized. Additional certifications could be required for your applications and should be included in your requirements to Nuventix.
- Does the SynJet® meet UL94V-0?
Yes, all products are designed to meet UL94V-0.
- Is EMI/RFI a problem for SynJets®?
SynJets have been tested at the EMI range and they have passed FCC Part 15, Subpart B, and Class A and Class B.
SynJet® Supporting Components (drivers, boards, heatsinks, etc.)
- Can I use my existing heat sink?
You can, however, the heat transfer could be sub-optimum. The lower flow rates and turbulent nature of SynJet coolers typically require a re-optimized heatsink to achieve ideal performance. It is also important to insure that the heat sink is not closed on the top – no ducting should be used. The reason for this is that the SynJet draws air from around itself and injects it into the heat sink (e.g. entrainment).
- Must I purchase the heat sink from Nuventix?
Nuventix can provide the heat sink or, if you prefer, we can specify the ideal heat sink dimensions and material and you may source it with your supply chain.
- Can I operate the SynJet® with my constant current LED driver?
Standard SynJet electronics requires 5 VDC or 12VDC (constant voltage) and usually consumes less than 1.5 W average power. A SynJet is not designed to operate from a constant current supply and it will be damaged by powering from a constant current supply.
- Reliability is crucial for the success of my product (i.e. telecom, military, industrial, LEDs), can SynJets® support this requirement?
SynJets are designed and constructed for very long life – 10 times that of any other active air cooler.
- My design requires unique form factors, how flexible are SynJets®?
SynJets enable you to open up the design envelope and think about how we can radically improve your product through new cooling architectures. Air doesn’t need to be just moved from left-to-right, it can be focused right where your design needs it.
- My product is in the high volume consumer electronics industry and I’m concerned about the cost of SynJets®?
SynJets provide benefits that highly differentiate products. You will have silent, fanless, active cooling that will essentially never fail. SynJets provide the best value in the industry from a cost/performance perspective and are well-suited for high volume consumer products.
- Can SynJets® be used outdoors?
SynJets can operate in virtually any environment. If you have a specific environmental concern, testing for that specification can be designed and tested by Nuventix.
- Can I retrofit a SynJet® into my current system?
Yes, SynJet technology is uniquely flexible. If a standard product does not fit to your design, the Nuventix sales team can discuss the application requirements. Nuventix provides custom design services in order to insure you receive the cooling performance you require.
- Can I use SynJets® to cool my entire system?
The most accurate way to find out is to discuss your specific cooling issues with a Nuventix Applications Engineer. However, SynJets do work well in most small enclosures (Set Top Boxes, Notebooks, etc.) so could be used to cool an entire system.
- How much space does a SynJet® require within a system?
There are a range of standard SynJet coolers in different sizes. Standard product specifications as well as 3D CAD files are available on the Nuventix website. In addition, you may contact the Nuventix sales team to discuss custom form factors and designs using the contact us link at the top of the page.
- How do I control/change the cooling level?
Most of the standard products have a variable cooling level control by use of a digital interface, however others can be designed to have a simple DC level control and PWM control.
- How much power and what kind of power does a SynJet® require?
Standard SynJet electronics requires 5 VDC or 12VDC (constant voltage) and usually consumes less than 1.5 W and some require much less.
- Can I put the electronics on my board?
The electronics are physically attached to the SynJet and during manufacturing firmware is loaded into the microcontroller for the SynJet, so it is not possible to separate the electronics from the SynJet.
- Where are SynJets® manufactured?
SynJets are produced by Hi-P.
- How much do SynJets® cost?
The cost will depend on the volume and product design. SynJet pricing is comparable with that of high quality fans.
- Given that SynJets® are a new technology, can high volumes be delivered?
Manufacturing is done by Hi-P in China. Hi-P can support tens of thousands of units per day. If higher volumes are required, Hi-P can rapidly add capacity.
- Who are Nuventix’ investors?
Our investors are Venture Capitalists specializing in Clean Tech industries. For more information, see the Investor’s section.
- What is SynJet’s® warranty?
The warranty is based on the reliability and testing of your specific product.
- What does Nuventix think about the LED thermal parameter evolution, i.e. many LED suppliers are decreasing thermal resistance. Do you think SynJet® technology will still be necessary in 5 years?
The LED system efficacy is a continuous process and will certainly result in more lumens per watt with every new LED generation. There is, however, a theoretical physical limit to how efficient the LED can become and developers are already reaching that limit. Also worth noting is that most OEMs wish their products could produce more light. So even if efficacy improves, thermal problems would remain as more light would be demanded. This coupled with the desire to produce products in smaller dimensions will result in increased thermal issues.