Custom Tube-Fin Heat Exchanger

OEM engineers sometimes opt for an off-the-shelf standard cold plate or heat exchanger for prototyping purposes, even though they know they will end up needing a custom product in production. Typically this is done in an effort to save time or money. However, it’s important to note that standard products are usually not designed or manufactured to withstand the demanding requirements and/or harsh environments found in some applications. For example, in military and aerospace applications, shock, vibration, extreme pressure and temperatures, and severe environmental exposure is common. One of Lytron’s customers found this out the hard way, when he purchased an off-the-shelf standard tube-fin heat exchanger for a military application. The heat exchanger failed to withstand the shock and vibration seen in his application, costing him valuable time. He ended up turning to Lytron for the design and manufacture of a custom tube-fin heat exchanger built for the application. 

If you’re unsure about your application’s requirements, we recommend consulting with an engineer before buying. Lytron’s Ask an Engineer form is a great place to start. Lytron’s engineers work extensively with OEM engineers during the design phase of a project or program to provide insight into industry specific requirements and design-for-manufacturability considerations.  

Have you tried a standard and ended up needing a custom?

Plate-Fin Oil Cooler

Lytron frequently receives questions through its “Ask an Engineer” website form. A customer recently asked us the following question: “What custom heat exchanger technologies do you recommend for cooling oil?”

There are two heat exchanger technologies that we typically use for custom oil coolers: flat tube and plate-fin. Both are vacuum-brazed and high performance. If flat tube will meet your thermal and mechanical requirements, we will generally recommend it over plate-fin because flat tube typically costs less to manufacture.

Curved Flat Tube Heat Exchanger

In addition, our flat tube can be bent into a 3⁄8˝ (3 mm) inside radius without buckling, allowing us to manufacture a flat tube heat exchanger into a curved shape if necessary.

Tube-fin heat exchangers are also an option for cooling oil, but their performance is not as high as flat-tube or plate-fin heat exchangers.

For applications requiring the highest performance and the lightest weight, we will generally recommend plate-fin heat exchangers over flat tube heat exchangers. The majority of military and aerospace oil coolers being designed today use plate-fin technology. Shown in the image to the left is a liquid-to-liquid plate-fin oil cooler designed for a commercial airplane.

JLTV

Lytron will be exhibiting at the inaugural National Defense Industrial Association’s (NDIA) Detroit Industrial Base Product Expo next week. The show runs March 10th-11th in Sterling Heights, Michigan, USA. It’s a defense industry product exhibition intended to showcase military contractors’ products to U.S. Army Tank-Automotive and Armaments Command (TACOM) and Army Tank Automotive Research, Development and Engineering Center (TARDEC) customers in the Detroit, Michigan area. Lytron will be exhibiting custom designed heat exchangers, heat exchanger assemblies, cold plates, and cold plate assemblies.

BigDog image provided courtesy of Boston Dynamics ©2009

In the Boston Sunday Globe[1] newspaper this week, there was an article featuring the Boston Dynamics BigDog. The BigDog is a 240 lb (109 kg), 3 ft (0.9 m) long robot designed to carry loads up to 340 lbs (154 kg), run up to 4 miles/hr (6.4 km/hr), and even climb hills. Last week, Boston Dynamics announced it had landed a $32 million grant from the U.S. Pentagon’s Defense Advanced Research Projects Agency (DARPA) to develop the next generation of BigDog for use by U.S. Marines. On the front of the BigDog is a flat tube heat exchanger to keep the BigDog from overheating. Flat tube heat exchangers typically cool oil or hydraulic fluid or electronics. Apparently the BigDog has been spotted in a park just down the road in Waltham, Massachusetts! You can watch videos of the very popular BigDog on YouTube.com.

Read the article or see custom military heat exchangers.

BigDog and Heat Exchanger - BigDog image provided courtesy of Boston Dynamics ©2009

BigDog in Snow - BigDog image provided courtesy of Boston Dynamics ©2009

Lytron Heat Exchanger

Plate-Fin Heat Exchanger Mounted on Fire Scout

We recently received these great photos from Pacific Design Technologies, courtesy of DRS Technologies. The photos are of the Northrop Grumman Fire Scout Unmanned Aerial Vehicle (UAV) and show the plate-fin heat exchanger that Lytron designed and manufactured for the helicopter. 

The heat exchanger is a custom PAO-to-air plate-fin heat exchanger for electronics cooling and features custom hail fin for the exposed side of the heat exchanger. The close up photo shows the heat exchanger in the front center of the UAV just below the nose.

Plate-Fin Heat Exchanger Mounted on Fire Scout

Fire Scout Helicopter

Lytron Custom Plate-Fin Heat Exchanger

Stainless Steel Tubes

An article recently published on MachineDesign.com, titled “Comparing Stainless Steel and Other Metals,” is an excellent overview of what stainless steel is as well as its types, properties, and manufacturing challenges. The article, written by Norm Ellis, focuses on the use of stainless steel in the aerospace industry. It contains a table that compares austenitic, ferritic, martensitic, precipitation hardening, and duplex type stainless steels, their percentages of chromium and nickel, and their UTS, yield strength, elongation, and hardness properties. Although steel is typically 66% heavier than aluminum, it is because of steel’s specific strength that it is of interest to aircraft engineers. (Specific strength is the ratio of strength to density.)

According to the American Iron and Steel Institute, stainless steel is steel that contains more than 10% chromium, either with or without other alloying elements. Stainless steel resists corrosion, maintains its strength at high temperatures, and is easily maintained or sanitized. For these reasons, stainless steel is often used in the food, medical, transportation, and aerospace industries.

One of the most common grades of stainless steel is Type 316, the type Lytron uses for the tubes of its standard stainless steel heat exchangers and some tubed cold plates. Type 316 is an austenitic (chromium-nickel stainless class) stainless steel containing 2%–3% molybdenum. The inclusion of molybdenum gives 316 greater resistance to various forms of deterioration, while nickel and manganese keep the metal in an austenitic microstructure. Austenitic stainless steels generally have the best corrosion resistance of all stainless steels because they contain at least 16% chromium. These alloys are also weldable, which is important in the manufacturing of heat exchangers and cold plates.   

When selecting metals for liquid cooling components or systems, there are a large number of considerations. Strength and corrosion resistance are just two of the considerations. In most aerospace liquid cooling applications, weight is one of the other major considerations. Vacuum-brazed aluminum heat exchangers are typically the cooling technology selected because they are lightweight as well as strong. In applications where weight is much less of a factor, the strength and cleanliness of stainless steel might make it worth sticking with stainless.

John, Engineer

Paris Air Show 2009

Lytron exhibited at the International Paris Air Show in Paris, France from June 15th through June 18th. The Paris Air Show is a commercial air show, organized by the French aerospace industry’s body the Groupement des Industries Françaises Aéronautiques et Spatiales (GIFAS), whose main purpose is to demonstrate military and civilian aircraft to potential customers. Major sales contracts are announced during the show as part of the corporate communication of the manufacturers. All major international manufacturers, as well as the military forces of several countries, attend the Paris Air Show. In addition to commercial visitors, the show welcomes a large number of public visitors from France and many other European countries. The 2009 show had more than 400,000 visitors and more than 2,000 exhibitors.

Lytron first exhibited at the Paris Air Show in 2007. This year, four Lytron employeees attended the show. We staffed our exhibit booth and held scheduled as well as impromptu business meetings both inside and outside of our booth. The booth attracted a large number of visitors and demonstrated Lytron’s continued commitment to the commercial aerospace and military markets and aircraft liquid cooling.