The 7 most common myths about heat pipes
As electronic devices continue to evolve, demanding more features and higher reliability, excessive heat remains a significant obstacle to developing better-performing next-generation applications and groundbreaking innovations. In every industry, especially in mobile, medical, telecommunications, and the Internet of Things (IoT), the challenge is to create new products and systems that are compact, multifunctional, and capable of managing high heat loads with high reliability. Engineers face the challenge of effectively handling heat as consumers demand smaller, thinner, more powerful devices with additional options, features, and capabilities.
Dual-phase cooling is rapidly evolving and gaining popularity in addressing these challenges. Heat pipes, in particular, have proven highly effective in achieving faster cooling, lighter weight, increased reliability, and longer lifespan. However, their most significant advantage lies in their design flexibility, seamlessly integrating into thermal systems to significantly enhance cooling efficiency and capacity.
Overview:
Heat pipe components combine the mature and reliable passive two-phase heat transfer with various other thermal management technologies to generate effective, durable cooling solutions. With over fifty years of innovation and manufacturing experience in heat pipe solutions, Boyd is well-equipped to design and manufacture efficient and durable cooling solutions that can operate under the most demanding environmental conditions.
Extendable copper walls and cores can be bent or flattened to meet the thermal and geometric requirements of applications. This flexibility can be utilized to reduce overall size, increase surface contact, or arrange heat pipes around installed hardware. Heat pipes can be embedded in other technologies to expedite heat dissipation or utilize heat pipes within a system to transport heat from the heat source to a safe dissipation location.
Misconception 1: If a heat pipe breaks, it will leak liquid onto my electronic device.
Truth: Heat pipes rarely, if ever, break. In extremely unlikely scenarios, a minimal amount of liquid in the pipe may saturate its core, but it cannot drip or leak onto your electronic device. Heat pipes are inherently robust, operating as a purely passive system with no moving parts that could wear out over time. To "break" a well-manufactured heat pipe, one would need to cut it open or subject it to excessive bending or folding. Heat pipes are filled under vacuum, ensuring that the fluid volume in the pipe remains in vapor form, preventing any dripping.
Their durability, higher reliability, and leak-free characteristics make heat pipes the ideal solution for aerospace, medical, consumer electronics, high-power applications that demand high reliability, and markets where leaks from traditional liquid solutions could have catastrophic consequences.
Misconception 2: Heat pipes are heavy.
Truth: Heat pipes can reduce weight more than they add to components.
While heat pipes are typically made of copper (a relatively heavy material), some mistakenly believe that integrating heat pipes will increase the weight of their solution. However, despite being made of copper, heat pipes are hollow, reducing the weight of the solution while enhancing heat performance in various ways. Heat pipes are commonly used to transfer heat to areas that are cooler, more remote, and more open, where airflow and space can be better utilized. This allows for the addition of fans and lightweight fin structures in these spaces, reducing the overall size and weight of the cooling solution.
Another common example is replacing traditional copper heatsinks or larger heatsinks with an aluminum base embedded with heat pipes. The high heat dissipation efficiency of heat pipes evenly and quickly distributes heat across the entire heatsink, improving efficiency, reducing heatsink size and material requirements, ultimately lowering the overall weight and cost of the solution.
Misconception 3: Heat pipes can only be used with evaporators and condensers at both ends.
Truth: Heat pipes operate along their entire length, regardless of their position on the pipe; they consistently transfer heat from hotter areas to cooler ones.
Heat pipes are typically designed as heat management components to transport heat from a heat source at one end to another for safe and effective dissipation. While this use is common, it is not the only way to employ heat pipes.
The wick structure of heat pipes allows them to operate in any direction, often traversing the entire length of the pipe. Heat, by its nature, moves from hot to cold, and heat pipes are no exception. Regardless of where the heat is placed along the pipe, it will always flow from the heat source towards the condensation point, and then back through the core. This increases design flexibility and options for heat pipe usage, allowing for more innovative and cost-effective thermal management. One such application is embedding heat pipes to propagate heat instead of transferring heat. When heat pipes are embedded at the bottom of a heatsink, heat is distributed along the entire length of the heat pipe rather than condensing in a fixed area. For example, integrating heat pipes into air-cooled heatsinks to extend high-power performance, reducing the need for liquid systems when cooling high-power IGBT.
Misconception 4: Heat pipes can only propagate heat in a straight line. If I want to spread heat across the entire base, I need a heat spreader.
Truth: Heat pipes can be bent, behaving similarly to a heat spreader but with a more integrated structure.
When heat pipes were initially introduced and integrated with other technologies, they were embedded in straight lines. To achieve more even heat dissipation, engineers used heat spreaders. While heat spreaders can effectively achieve uniform heat diffusion, they come with their own set of design challenges that may not be suitable for every application.
Although heat pipes move heat only along their axis, the axis can be bent or used with multiple heat pipes to effectively act as a planar diffusion mechanism similar to a heat spreader. Heat pipes are more cost-effective, structurally more robust, and can be designed to mimic the function and performance of a heat spreader. If embedded correctly, heat pipes can withstand significant mounting force in applications where a vapor chamber might be too fragile.
Misconception 5: Heat pipes need to be very hot to function.
Truth: Manufacturing technology enables heat pipes to function even with a small temperature difference.
Since heat pipes rely on evaporation and condensation to function, there is a common misconception that there must be a large temperature difference or high temperature for heat pipes to be beneficial. However, as heat pipes are filled with a vacuum before sealing, the fluid within them exists simultaneously in liquid and vapor forms at its saturation point. This is akin to boiling a liquid at lower temperatures under reduced pressure, such as at higher altitudes and lower pressures. Molecules require less heat to be excited enough to change from liquid to vapor. Therefore, the temperature of the heat source does not need to reach the standard room temperature boiling point to initiate the phase change. In fact, only a few degrees of difference between the "hot" and "cold" regions of the heat pipe are sufficient for it to function. This is one of the primary advantages of using heat pipes, as it can minimize the thermal resistance of the solution.
Misconception 6: Heat pipes cannot be used in freezing conditions.
Truth: Heat pipes can be developed to operate in extremely harsh conditions, such as freezing environments.
The operational mode of heat pipes in environmental conditions depends on the materials and design. While copper/water is the most popular combination, other materials can be used for specific requirements. Liquids like ammonia, methanol, and acetone can be combined with compatible metals to form heat pipes that operate at temperatures far below -60°C.
Misconception 7: Heat pipes are expensive.
Truth: Adding heat pipes can reduce overall solution costs.
The ductility of copper allows for the economical manufacturing, reliable sealing, and easy bending and pressing into specific geometric shapes. Boyd has perfected manufacturing processes and heat pipe design technology to produce cost-effective high-performance copper/water heat pipes. Heat pipes enable engineers to use aluminum and embedded heat pipes in applications requiring copper finned bases, reducing costs. They can also eliminate the need for fans or other components, saving money and weight.
In conclusion, heat pipes are versatile and highly beneficial in thermal management, dispelling various misconceptions. These misconceptions often stem from a lack of understanding of the technology's capabilities and applications. With the ability to enhance cooling efficiency, reduce weight, and operate in diverse conditions, heat pipes stand as a reliable and cost-effective solution in the ever-evolving landscape of electronic and high-power applications.
