What are the Benefits of Microchannel Heat Exchangers?

Advanced industrial systems require heat exchangers to move enormous amounts of thermal energy through space constrained environments. Yet the intense heat and pressure of applications like nuclear power generation and hydrogen fueling often push traditional heat exchanger designs well past their limits. When they do, the results can be catastrophic. 

Microchannel heat exchangers offer a better solution. These devices provide highly efficient heat transfer in a compact design. And because they are diffusion bonded, they are purpose-built to withstand extreme heat and pressure.

Below, we’ll explore the benefits of microchannel heat exchangers and how they make advanced thermal systems possible.

What Are Microchannel Heat Exchangers?

Microchannel heat exchangers transfer large amounts of thermal energy between fluids. Though the term “microchannel heat exchanger” can refer to a wide variety of devices—like a car radiator or HVAC coils—in high-performance industrial applications, microchannel heat exchangers are more accurately described as Printed Circuit Heat Exchangers (PCHEs). 

These heat exchangers are fabricated by chemically etching or machining hundreds to thousands of micro-scale flow channels into the surface of metal plates. These channels are extremely small, typically between 0.5 – 2 mm in diameter. The narrow diameter creates a very high surface-area-to-volume ratio, which enables extremely efficient heat transfer between hot and cold fluids. 

PCHEs are fabricated by stacking the etched plates together in various configurations such as  counter-flow, cross-flow, or co-flow configurations. The plates are joined together using a process called diffusion bonding. 

Diffusion bonding is a solid-state joining process. It is performed by heating the plates to a temperature that is just below the parent material’s melting point. This allows the atoms at the surface of each plate to diffuse and bond together. A solid core block is formed that has the strength and durability of the parent materials. 

Design flexibility is another core feature of this technology. Engineers can manipulate design variables including channel geometry, channel density, and wall thickness to create a flow configuration optimized for each client’s needs.  

Diffusion bonded microchannel heat exchangers offer very efficient thermal transfer, in a form factor as little as 1/6th the size of conventional shell-and-tube exchangers. This makes them ideal not only for high heat and pressure applications, but for those where a small footprint is necessary.

The Key Advantages of Microchannel Heat Exchangers

There are three primary advantages microchannel heat exchangers offer over traditional heat exchangers:

Exceptional Heat Transfer Efficiency

The extremely narrow diameter of flow channels enables high heat transfer coefficients. The counter-flow configuration creates a low contact penalty that can result in a large equivalent surface area for thermal energy to be transferred with a relatively small volume of fluids.

Despite their compact size, microchannel heat exchanger efficiency can transfer heat loads into the mega-watt scale. This allows them to be used for applications ranging from small cold plates to exchanging heat for large power plants using various fluids (liquid, gas and two phase fluids). Their operation also covers cryogenic (-250C) to high temperature (+900C) applications only limited by material’s capability to withstand temperature.

Durability Under Extreme Pressure and Heat

Microchannel heat exchangers are far more durable than other heat exchanger designs. 

Diffusion bonding produces a solid metal core, with no gaskets, bolts, tubes or brazed joints that can fail, as in traditional heat exchangers. This provides greater structural integrity capable of withstanding extreme pressures and elevated temperatures.

The variety of materials that can be used offer another advantage of microchannel heat exchangers. Materials like 300-series stainless steel are commonly used, as well as titanium, aluminum, and high-nickel alloys. This flexibility in materials allows these exchangers to be tailored for specific thermal and chemical applications. 

This makes microchannel heat exchangers well suited for hydrogen pre-cooling at pressures that exceed 1000 barg. LNG processing and nuclear heat transfer systems that require pressure containment and thermal stability for safety also benefit from diffusion bonded strength.

Compact Size and Minimal Materials

A major benefit of microchannel heat exchangers is their compact size. VPE Thermal’s advanced engineering and design capabilities produce some of the most compact and highly efficient PCHES on the market, with designs as little as 1/6th the size of conventional shell-and-tube exchangers.

This reduced form factor enables them to be used in space-constrained environments, like hydrogen fueling stations. A smaller footprint also makes production more cost efficient. The volume of fluids needed is kept to a minimum, as well the raw material required to produce the device.

Common Misconceptions of Microchannel Heat Exchangers

We often hear misconceptions about the performance of microchannel heat exchangers. However these can be easily dispelled:

Misconception #1: “Microchannels are too small and restrict flow”

Hundreds to thousands of microchannels are etched onto a single plate, with several plates used to form each core. Together, thousands of microchannels create a high surface-area-to-volume ratio that allows fluids to flow easily through the device.

Misconception #2: “Microchannels are easily clogged by debris”

Microchannel heat exchangers use upstream filtration to keep debris from entering the channels. Each PCHE has a highly controlled process environment to manage the fluid quality. When needed, the devices can be flushed and cleaned. 

Misconception #3: “These devices are too small to handle serious heat loads”

Despite their compact size, microchannel heat exchangers can safely and efficiently transfer heat loads on the megawatt scale. By spreading thousands of microchannels over a relatively large surface area they achieve efficiency that rivals much larger shell-and-tube exchangers.

Microchannel vs. Shell-and-Tube Heat Exchangers

Shell-and-tube heat exchangers are quite capable, but many applications can benefit from microchannel heat exchanger’s advantages:

Microchannel heat exchangers are extremely compact. Their footprint is as little as 1/6th that of shell-and-tube exchangers, making them ideal in applications where space is at a premium.

Their compact size also requires minimal materials when compared to much larger shell-and-tube assemblies. PCHEs can also be fabricated using a variety of metals based on client requirements. 

In addition, their diffusion bonded construction makes these units incredibly durable under extreme heat and pressure. Single block construction means there are zero fail points compared to shell-and-tube designs. 

PCHE’s are often hermetically sealed. This leaves minimal chance for leak paths, compared to the mechanical joints of shell-and-tube exchangers.

With thousands of microchannels across a large surface area, MCHEs also provide greater thermal efficiency than traditional heat exchangers.

For applications that require durability under extreme pressure, leak-proof design, and minimal footprint, microchannel heat exchangers offer a clear advantage over traditional shell-and-tube designs.

Microchannel Heat Exchanger Applications

VPE and its subsidiary VPE Thermal produce custom designed microchannel heat exchangers that serve a range of industries and applications including:

• Nuclear power generation
• Hydrogen fueling stations
• Renewable power generator cooling including solar, geothermal, and wind
• Brayton cycle utilizing supercritical CO2
• Pharmaceutical
• Waste heat recuperation
• Cryogenic temperatures
• Botanical extraction
• And many more

Why Use Microchannel Heat Exchangers?

For many advanced applications operating under extreme temperatures and pressures, microchannel heat exchangers offer significant advantages:

• Compact form makes them ideal where space is limited

• Diffusion bonded construction is extremely durable under high pressure and heat

• Materials can be optimized based on user requirements

• Devices can be hermetically sealed to reduce leak paths

• Provide high efficiency heat transfer in tight spaces

• Cost effective, with low weight and fluid inventory and minimal raw materials

• Can achieve corrosion resistance with properly selected alloys

When operating requirements call for high-performance in a compact footprint, diffusion bonded microchannel heat exchangers offer a reliable, cost effective solution built for the most demanding environments. 

VPE: Your Source for Custom Built Microchannel Heat Exchangers

For over 50 years, Vacuum Process Engineering (VPE) has served countless clients with custom designed diffusion bonded microchannel heat exchangers. 

VPE combines:

• Custom design and engineering of microchannel heat exchangers
• Advanced thermal design software to optimize for each client’s needs
• Multiple diffusion bonding furnaces capable of large batch production
• Fast turn around and reliable sourcing
• In-house machining, welding, cleaning, and testing
• ISO 9001:2015 certification
• ASME U Stamp

Featuring more than 150,000 square feet of design, lab, production, and quality control space, VPE is more than just a manufacturer. We are a fully equipped design partner.

Ready to see the advantages of microchannel heat exchangers first hand? Contact the VPE team to discuss your project’s needs and let us engineer the ideal solution.