Immersion Cooling Emerges as New Cooling Technology

Immersion cooling, in which electronics are submerged in liquid coolants, is gaining popularity in the cooling industry. Companies have become aware of the benefits of immersion cooling in extreme environments, such as oil rigs or in the desert. The U.S. military is also considering liquid-immersion cooling to save energy in tropical camps.

Two types of liquid-immersion cooling include single-phase and two-phase. Single-phase is when an electronic device is placed in a metal case, and the liquid absorbs heat from the electronic device as the liquid flows over the case. The liquid is then pumped to a cooling unit outside, thus reducing the temperature.

Two-phase is a more complex process. “Heat from electronic components vaporizes liquid coolant, which condenses again in an outside unit as the heat is transferred to water. A fluid called Novec made by 3M is popular because it changes easily between gas and liquid and doesn’t adhere to electronics,” according to researchers.

Liquid immersion cooling has proved more successful than other cooling methods, since air cooling and other methods still require fans or air conditioners. Immersion cooling also saves 20 percent on costs, 40 percent on power and 60 percent on space.

“Liquid cooling will grow at about 16 per cent per year through 2019. The military is expected to drive modular designs because it operates in remote locations and requires security and mobility,” according to TechNavio.

Some companies that have already begun using immersion cooling include Icetope, LiquidCool Solutions (LCS), and Allied Control and Silicon Graphics Inc. (SGI). Icetope and LCS use single-phase cooling and SGI uses two-phase cooling.

Company Brings Liquid Cooling Technology to Smartphones

Reducing size of liquid cooling systems has been a challenge for companies in the electronics cooling industry for many years. Fujitsu introduces a 1mm thick liquid cooling heat pipe for compact electronic devices such as smartphones and tablets.

Consumers constantly feel their smartphones and tablets become hot after continuous use and Fujitsu believes its new heat pipe will solve this problem. The heat pipe can transfer more than five times the heat than current heat pipes in the industry.

“The miniature heat pipe is a closed system comprising of an evaporator and a condenser. The evaporator will sit closer to a hot spot (CPU or GPU) and the condenser would be located at a relatively cooler section of the phone. Tiny pipes will connect the two to form a closed loop. The evaporator has six perforated sheets of copper, each about 0.1mm thick. The heat from the hotspot causes the liquid to vaporise and the vapor line will carry these vapors to the condenser where the lower temperature causes the vapours to condense back to liquid state and release heat energy in the process. The liquid moves in the system through capillary action which makes the orientation of the smartphone irrelevant,” according to Fujitsu.

Thermal Foil Sheets Offer Advanced Thermal Management in Smartphones

Angstron Materials Inc. has developed a family of thermal foil products ideal for smartphones, and other hand-held devices. The new thermal foil sheets have a thickness of from 5 um to 40 um and thermal conductivity between 800 W/m-K and 1,700 W/m-K. The sheets offer design flexibility and they are available in different grades; they are also cost-effective.

“Miniaturization results in less space to dissipate heat generated from today’s high-performance processors. Efficient thermal interface materials are critical for current and next generation devices due to the growing demand for greater functionality in smaller spaces like the new Apple Watch,” Ian Fuller, Angstron’s application engineering manager, said.

These thermal sheets are ideal for use in EMI Shielding, smartphones, tablets, laptops, flatscreen TVs and other applications.

Thermoelectric Coolers Ideal for Cooling Mobile Devices in All Environments

EIC Solutions Inc. introduces a product line of Auto-ranging (M105) Thermoelectric Air Conditioners. The ThermoTEC 141, 145 and 151 series have auto ranging power capabilities. The auto ranging feature is ideal for cooling mobile devices and applications. A heating option is also available for environments with fluctuating temperatures.

“The Auto-Ranging Series (M105) coolers are a rugged, durable unit designed for a variety of applications. The flexibility of these auto ranging units makes them the ideal choice for virtually any power scenario, eliminating the need for transformers. This design is also a great fit for the early phases of a project where the AC power supply is undefined,” Lori Galdo, EIC sales engineer, said.

The air conditioners have an operating temperature of up to 140 degrees Fahrenheit and advanced circuit design which allows units to run on 120 or 240 AC power. The coolers offer advanced protection of electronics in many different environments. Some ideal applications for these coolers include computers, control panels, sensors, telecommunication systems and surveillance devices.

Piezoelectric fans and their application In electronics cooling

Piezoelectric fans seem to represent an example of research and development that has culminated in a product that is deceptively simple. Although piezoelectric technology is capable of producing rotary motion, the fans operate quite differently from rotary fans, as they generate airflow with vibrating cantilevers instead of spinning blades.

Piezoelectric, as derived from Greek root words, means pressure and electricity. There are certain substances, both naturally occurring and man-made, which will produce an electric charge from a change in dimension and vice-versa. Such a device is known as a piezoelectric transducer (PZT), which is the prime mover of a piezoelectric fan. When electric power, such as AC voltage at 60 Hz is applied, it causes the PZT to flex back and forth, also at 60 Hz.

The magnitude of this motion is very tiny, so to amplify it, a flexible shim or cantilever, such as a sheet of Mylar, is attached and tuned to resonate at the electrical input frequency. Since piezoelectric fans must vibrate, they must use a pulsating or alternating current (AC) power source. Standard 120 V, 60 Hz electricity, just as it is delivered from the power company, is ideal for this application, since it requires no conversion.

[If direct current (DC), such as in battery-operated devices, is the power source, then an inverter circuit must be employed to produce an AC output. An inverter may be embodied in a small circuit board and is commercially available with frequency ranges from 50 to 450Hz.]

Driving the fan at resonance minimizes the power consumption of the fan while providing maximum tip deflection. The cantilever is tuned to resonate at a particular frequency by adjusting its length or thickness. The PZT itself also has a resonant frequency, so the simplistic concept of adjusting only the cantilever dimensions to suit any frequency may still not yield optimum performance. (Conceivably, tuning the electrical input frequency to match existing cantilever dimensions may work, though with the same caveat, that the resonant frequencies of all the components must match, within reason.