Thermal Management Considerations for Medical Equipment Cooling

The healthcare industry relies on advanced machinery — from small, handheld surgical equipment to massive, full-body MRI machines — to deliver quality care. That care, however, can only be accomplished if these medical devices are reliable.

When these systems malfunction, it could be a matter of life or death. Using medical equipment cooling methods, thermal engineers have designed innovative cooling solutions to help regulate their thermal loads during their unique operating cycles. 

Discover some of the top challenges of medical equipment cooling and how ACT’s team helps solve them using advanced technology. 

Importance of Temperature Control in Medical Devices

The need for temperature control in medical technology boils down to 2 necessities: device performance and safety. 

1. Device Performance

If medical devices don’t work, they’re fruitless. Optimal device performance is contingent on precision, reliability, and longevity. 

Medical professionals need these systems to perform at their peak to yield precise results. The inability to control heat fluctuations can impact the accuracy of readings. Medical device cooling helps doctors return accurate results.

Medical technology must also be reliable. Drastic changes in temperature force the cooling technology to work harder, increasing the risk of malfunctions, breakdowns, or other technical failures. If the technology breaks, unexpected device downtime can occur, resulting in productivity or financial losses for the institution. 

When the temperature can be controlled through medical device cooling, the risk of downtown is reduced and the device’s lifespan is extended. 

2. Safety

What’s worse than technology that doesn’t work? Technology that isn’t safe. In the Medical Industry, thermal engineers must solve the unique challenge of designing cooling solutions that are safe for patients and doctors. 

High heat in medical technology, like surgical devices, can cause tissue damage, discomfort, or increased risk of infection in patients. Some of that same technology must also be designed to operate in touch-safe temperature ranges, so the doctors handling them don’t injure themselves.

Controlling the heat loads using medical device cooling can improve patient welfare and doctor safety. 

Medical Equipment Cooling Challenges

Cooling medical equipment comes with its own set of unique challenges. From packaging requirements to duty cycle challenges, let’s break down the nuances of device cooling in the medical industry.

1. Packaging Challenges

There’s no “one size fits all” solution when it comes to cooling medical equipment. Some systems, like surgical devices, are really small. If there’s not enough space immediately around the heat-generating component to dissipate the energy, that heat needs to be moved to a location where cooling is available. This method is called remote cooling. 

The opposite of remote cooling is spot cooling, which is a method of direct cooling the proximity where the heat is being generated. Larger technology like MRI machines can utilize this method because there’s more surface area to dissipate the heat away from the area it’s being generated. 

Another thing to consider with packaging requirements, specifically for larger technology, is sound. Pumps and fans used to cool machines can be irritating for patients and operators. Engineers must balance the need for efficiency with the need for quieter technology. 

2. Temperature Stability

Unlike other industries, medical equipment cooling has a human element to consider. Precise heat control is required for items like surgical devices to operate in safe temperature ranges that will not damage tissue. On the other hand, temperature stability helps maintain touch-safe temperatures to protect the doctors operating the technology. 

Isothermality requirements are often addressed in conversations about temperature stability. Medical equipment must operate at consistent temperatures, especially in diagnostic testing. In PCR machines, for example, it’s crucial the temperature remains constant so that the data cycles at the same rate and samples don’t deviate. 

3. Operating Temperature Requirements

Medical applications have a large range of operating temperature requirements, with solutions stretching from sub-ambient to above-ambient cooling. The inability to stay within these safe operating temperatures can negatively impact performance results, safety, and reliability. 

As the design of these devices shrinks, medical equipment cooling to maintain these temperatures becomes an increasing challenge. (Example: DNA Replicators)

4. Duty Cycle Challenges

Not all medical electronics are “steady-state,” which operate on constant “on” schedules. Some medical devices are “transient,” meaning they operate on on/off cycles. 

When they’re on, these devices operate at very high temperatures for a short time, followed by an extended period of rest. When not managed properly, the “cyclical thermal stresses” can lead to reduced reliability. Lasers are a good example of technology that works at high heat for a very short on-cycle, followed by an extended off-cycle.

ACT’s Cooling Solutions for Medical Equipment

ACT has decades of proven experience in medical equipment cooling. 

Spot-Cooling Systems for Low-Density Medical Devices

Medical devices with lower power densities can be cooled through spot-cooling technology. These systems directly cool the heat-generating component at its source. 

1. Heat Pipes

Heat pipes for medical devices are a powerful, passive solution to remove heat. They move energy from the immediate cross-section of the heat-generating component to a heat sink where it can be rejected without the use of pumps or compressors. 

They’re considered 1-directional heat spreaders because the thermal energy travels in a constant cycle, entering through the evaporator and leaving through the condenser. 

2. Vapor Chambers

Vapor Chambers are another passive, spot-cooling solution for medical equipment. Unlike heat pipes, however, these are planar, two-phase transfer devices with the unique ability to form an almost uniform temperature gradient across the heat output. 

They work in 2 dimensions, capturing heat at the evaporator, where the working fluid boils and evaporates. That vapor fills the inner chamber, spreading heat in 2 directions across the plane.  This process enables them to manage the thermal energy in high-heat flux applications.  

Generally, vapor chambers for medical devices are best suited for applications that require precise temperature control across the equipment.

3. Hik™  Plates 

Hik™ plates are a reliable technology that falls somewhere between heat pipes and vapor chambers in terms of performance capabilities. These heat spreaders are made by embedding heat pipes into regular aluminum base plates, boosting their thermal conductivity from <200 W/m-k to upwards of 1000 W/m-k.  

They’re considered a more “cost-effective” solution compared to vapor chambers because they can effectively spread thermal energy away from the heat-generating component across the aluminum plate. Through strategic placement of the heat pipes, HiK™ plates can spread heat from multiple sources on the base plate.

4. Thermoelectric Modules

Thermoelectric coolers (TECs) are one of the best spot-cooling systems for medical devices with low power densities. They operate best in densities with only tens of watts, which means they require a significant amount of energy input to actually cool the machine.

When used in products like laser modules that require the temperature to be maintained below the ambient air temperature, TECs can spot-cool the device by lowering the local temperature with sub-ambient cooling. 

Remote Cooling for High-Density Medical Devices

In medical systems with tight packaging restraints, medical equipment cooling can be achieved through an intermediate heat transport loop. This method of remote cooling removes heat from point A to point B in medical devices that are too small to cool it at its source. 

1. Heat Pipes

In remote cooling applications, heat pipes transport the thermal energy from the heat-generating component to a heat sink (usually the air). These systems work best in low-power devices where the heat transfer distance is short. 

2. Loop Thermosyphons

Loop Thermosyphon technology can be utilized in medical devices that use more power and require the heat to be transfered across further distances. They mirror the thermodynamics of regular heat pipes — fluid boils at the evaporator and moves heat from the source to its rejection site at the condenser — but in a loop instead of a straight line. 

These systems are unique because they require a certain amount of gravity to operate, which can limit their use to only certain orientations. 

3. Liquid Cooling

Liquid cold plates are another powerful remote-cooling solutions. When mounted to your heat-generating component, they can manage the highest thermal loads and transport energy across the longest distances. 

These plates can be installed in a variety of different orientations, but they require support from balance plant components — pumps, reservoirs, heat exchangers, etc. — to supply the fluid to the plate where it can remove the energy. 

With the addition of a chiller, liquid cold plates can support sub-ambient cooling. 

4. Pumped-Two Phase

The most advanced remote solution for medical equipment cooling is pumped two-phase (P2P). It operates similarly to the loop thermosyphons, but with a pump to support orientations against gravity. Using the pump, this technology is able to remove 10s to 100s of kWs of energy.

Like liquid cooling, P2P requires support from balanced plant components to move the hot vapor to the condenser to be rejected. This exchange can happen at a constant, almost uniform temperature. When multiple components are mounted onto the evaporator, each line of heat can maintain a temperature within 1℃ of each other. 

Transient vs Steady-State Cooling Considerations

Most of the products listed above can operate in steady-state applications, but some applications have a high heat rejection requirement over a short period of operation. Transient operations like these require a transient cooling system.

Phase Change Materials (PCMs) can help “dampen” the peak loads of transient systems by storing the thermal energy during on cycles and waiting to dissipate it when it returns to the off cycle. 

In most medical applications, this change occurs from a solid to liquid instead of liquid to vapor, allowing the PMC to absorb and store that energy until it reaches the maximum melt zone. This still happens at a constant temperature to maintain isothermality. 

Work With ACT to Solve Your Medical Device Cooling Problems

Advanced Cooling Technologies (ACT) has over 2 decades of experience in thermal management, with proven experience in the medical industry. 

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