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Heat pipes

ADVANCED COOLING TECHNOLOGIES, INC. (ACT) HAS WORKED EXTENSIVELY ON HEAT PIPE PRODUCT RELIABILITY. This guide provides information for designing, modeling, and practical reliability surrounding copper/water heat pipes.

A heat pipe is a two phase heat transfer device with very high “effective” thermal conductivity. It is a vacuum tight device consisting of an envelope, a working fluid, and a wick structure. As shown below, the heat input vaporizes the liquid working fluid inside the wick in the evaporator section. The saturated vapor, carrying the latent heat of vaporization, flows towards the colder condenser section. In the condenser, the vapor condenses and gives up its latent heat. The condensed liquid returns to the evaporator through the wick structure by capillary action. The phase change processes and two phase flow circulation continue as long as the temperature gradient between the evaporator and condenser are maintained.

Thermal Solutions, Power Electronics, Power Generation, Operational Equipment

Power Electronics are the most critical components in a large number of applications; including power generation and operational equipment. Power Electronics module manufacturers invest millions of dollars to make these devices as effcient as possible, aiming primarily to reduce waste heat. However, even with effciency gains at the module level, overall waste heat is rising across the industry due to more system and user driven functional requirements. Increased system capability leads to higher power densities and more waste heat! Selecting off the shelf thermal solutions is no longer a viable option for applications that are pushing the envelope on power and operating effciency.

Investing in an optimal thermal solution can be the design change with the largest payback potential in a high power system. If properly designed, the thermal management system should not only meet performance requirements, but do so while minimizing energy usage. This eBook provides a guide for designers looking to expand the operating limits of traditional air and liquid cooled thermal solutions.

Machine Vision Challenge: Cement Board Inspection

A customer inspecting 4 ft. by 10 ft. white fiber-cement boards required a lighting solution to highlight small 5cm long and 1mm thick surface scratches and defects. They also identified significant surface concavity created during the manufacturing process on some of the 2cm thick boards. As a result, they required the flexible lighting solution to also assist their efforts to develop an identification and grading system to pass/fail board concavity.

The cement boards were inspected in motion, running 1 foot/second through an enclosed tunnel. The inspection setup required a low-angle, narrow beam throw for uniform illumination across the full surface of the board to identify the scratches. The tunnel setup also required the use of longer lights for full board coverage and to facilitate installation.

An additional inspection using the same area-scan camera, but with bright field oriented lighting, necessitated the two lighting orientations be independently controlled with an on/off trigger. The customer contacted Control System Integrators (CSI), Inc. to configure a lighting solution for this inspection challenge.

Ai Solution: High Intensity Bar Lights

Via Ai’s Distribution Partner, Kendall Electric, CSI, Inc. reached out to Advanced illumination to provide a dark field lighting solution for their customer. To match the size and uniformity needs, Ai suggested the LL174 High Intensity Bar Lights with a diffuse light conditioning.

These lights are highly customizable, each available in the 24” length demanded of the application. The configurable control options also allowed for the use of the iCS 3 Inline Cable Controller to enable constant or strobed power to the light. The longer length and controller options met the customer’s initial requirements to fit within the existing machine vision setup constraints.

Illumination Results: Superior Contrast for Inspection

When deployed in the inspection setup, the LL17424-WHII3D Bar Lights provided a uniform light spread across the entire length of the cement board within the inspection tunnel. In comparison to competitive lights tested for consideration in this application, the High Intensity Bar Lights provided superior contrast to identify the scratches and other defects, even with the occasional concave boards.

Board Inspection with Competitive Bar Light

Board Inspection with Competitive Bar Light

Board Inspection with LL174 High Intensity Bar Light from Ai

According to Daniel Alcala, Vision Automation Engineer for CSI, Inc., “we try to provide our clients with the best possible solution, and the small form factor, high intensity, and high uniformity of the Ai lights made them the best fit for the job.”

Sealed Enclosures, Thermal Solutions, Harsh Environments

All electronics dissipate waste heat. In typical high-power electronics cabinets this waste heat can become significant, in the range of 100’s to 1,000’s of Watts. At these levels dissipating the waste heat becomes a critical design issue. Most cabinets that operate in controlled indoor environments use fan filter systems, which duct ambient air through the cabinet, because they are the most eective and ecient way of dissipating the waste heat load. This is also feasible for some outdoor applications assuming rain guards and filters are used.

However, in many applications such as dirty / dusty environments, hose down / wash down facilities in the food industry, harsh outdoor applications, and many others it is not possible or advisable to allow ambient air to flow through and cool the sensitive and expensive components inside your enclosure. The best way to protect electronics is to use a sealed cabinet that does not allow any contaminated ambient air, even filtered air, from entering the cabinet. This is where sealed air-to-air heat exchangers, or sealed enclosure coolers, become an invaluable part of the overall system.