{"id":3773,"date":"2026-07-30T23:34:17","date_gmt":"2026-07-30T15:34:17","guid":{"rendered":"https:\/\/www.taichungbro.com\/2026\/07\/30\/fluorocarbon-immersion-cooling-pfas\/"},"modified":"2026-07-30T23:34:17","modified_gmt":"2026-07-30T15:34:17","slug":"fluorocarbon-immersion-cooling-pfas","status":"publish","type":"post","link":"https:\/\/www.taichungbro.com\/en\/2026\/07\/30\/fluorocarbon-immersion-cooling-pfas\/","title":{"rendered":"What are fluorocarbon coolants? Analysis of single-phase and two-phase immersion cooling and PFAS risks."},"content":{"rendered":"<p>As the power density of AI servers increases, fans not only become noisier, but airflow may also be insufficient to remove heat from the chips. Immersion cooling has therefore gained attention: placing the server board directly into a non-conductive dielectric coolant, allowing the liquid to absorb heat in close proximity to the CPU, GPU, memory, and power components.<\/p>\n<p>However, &quot;immersion coolant&quot; is not the same as &quot;fluorocarbon coolant,&quot; and &quot;fluorine-containing&quot; does not automatically equate to being regulated by a particular PFAS regulation. The correct selection must consider heat transfer methods, liquid properties, material compatibility, leakage and recovery methods, and the product&#039;s chemical composition. This article will first break down the differences between single-phase and two-phase coolants before explaining how to assess PFAS risks.<\/p>\n<nav class=\"article-toc\" aria-labelledby=\"article-toc-heading\" style=\"margin-block: 1.5em;\">\n<h2 id=\"article-toc-heading\">Table of Contents<\/h2>\n<ol>\n<li><a href=\"#what-is-fluorocarbon-coolant\" style=\"color: #00c8d7; text-decoration: underline;\">What is fluorocarbon coolant? Not all immersion fluids contain fluorine.<\/a><\/li>\n<li><a href=\"#single-phase-immersion\" style=\"color: #00c8d7; text-decoration: underline;\">Single-phase immersion cooling: The liquid does not boil; heat is removed through circulation.<\/a><\/li>\n<li><a href=\"#two-phase-immersion\" style=\"color: #00c8d7; text-decoration: underline;\">Two-phase immersion cooling: utilizes boiling and condensation to transfer heat.<\/a><\/li>\n<li><a href=\"#single-vs-two-phase\" style=\"color: #00c8d7; text-decoration: underline;\">How to choose between single-phase and two-phase? First, compare six engineering conditions.<\/a><\/li>\n<li><a href=\"#fluid-selection-parameters\" style=\"color: #00c8d7; text-decoration: underline;\">When it comes to coolant, you can&#039;t just look at its dielectric properties; what other parameters should you check?<\/a><\/li>\n<li><a href=\"#pfas-risk\" style=\"color: #00c8d7; text-decoration: underline;\">Is every fluorocarbon coolant a PFAS? The key lies in the definition and chemical structure.<\/a><\/li>\n<li><a href=\"#deployment-checklist\" style=\"color: #00c8d7; text-decoration: underline;\">Before implementing immersion cooling, complete this checklist.<\/a><\/li>\n<li><a href=\"#choose-system-not-fluid-only\" style=\"color: #00c8d7; text-decoration: underline;\">The choice wasn&#039;t a tank of liquid, but a maintainable thermal management system.<\/a><\/li>\n<\/ol>\n<\/nav>\n<h2 id=\"what-is-fluorocarbon-coolant\">What is fluorocarbon coolant? Not all immersion fluids contain fluorine.<\/h2>\n<p>Fluorocarbon coolants are a class of engineering fluids containing a carbon-fluorine structure and used to remove heat. Fluorinated ethers, perfluorinated compounds, or other fluorinated dielectric fluids may be found on the market, but these have similar product names and do not represent the same molecular structure, boiling point, global warming potential (GWP), or regulatory status.<\/p>\n<p>The dielectric fluid used in immersion cooling may also be non-fluorinated fluids such as mineral oil, synthetic hydrocarbons, esters, or silicates. Therefore, seeing the words &quot;immersion fluid&quot; does not necessarily mean that it is a fluorocarbon fluid; seeing &quot;non-conductive&quot; does not mean that it is safe for all plastics, seals, and circuit board materials.<\/p>\n<p>The value of dielectric fluid lies in allowing the liquid to directly contact electrically conductive electronic components without immediately causing a short circuit, while also absorbing heat using its higher density and heat capacity compared to air. To first establish a complete concept of a liquid cooling system, it can be combined with...<a href=\"https:\/\/www.taichungbro.com\/en\/2024\/09\/18\/liquid-cooling\/\" style=\"color: #00c8d7; text-decoration: underline;\">How liquid cooling is applied in high-efficiency equipment<\/a>Let&#039;s read together.<\/p>\n<h2 id=\"single-phase-immersion\">Single-phase immersion cooling: The liquid does not boil; heat is removed through circulation.<\/h2>\n<p>The &quot;single-phase&quot; in single-phase immersion cooling refers to the coolant remaining in a liquid state throughout its normal operating range. After the components transfer heat to the liquid, the hot liquid flows to the tank or an external heat exchanger through natural convection or forced circulation by a pump; after cooling, it returns to the vicinity of the server.<\/p>\n<p>The Open Compute Project (OCP) also defines a single-phase system as one in which the liquid does not change its phase during heating and cooling, and circulation can be completed by natural or forced convection. The control logic of this system is relatively intuitive, and the main on-site management includes flow rate, liquid temperature, filtration, liquid level, and secondary water circuit.<\/p>\n<p>However, a higher pump flow rate is not always better. Liquid viscosity, plate spacing, flow guiding structure, and local hot spots all contribute to determining the flow field; increasing the flow rate also increases pump power and pressure drop. This is related to...<a href=\"https:\/\/www.taichungbro.com\/en\/2025\/11\/24\/cold-plate\/\" style=\"color: #00c8d7; text-decoration: underline;\">Selection of water-cooled plate flow channels and pressure drop<\/a>Similarly, heat dissipation capacity must be considered together with energy consumption during transmission.<\/p>\n<h2 id=\"two-phase-immersion\">Two-phase immersion cooling: utilizes boiling and condensation to transfer heat.<\/h2>\n<p>Two-phase immersion cooling causes the coolant to boil on the surface of high-temperature components. The liquid absorbs latent heat of vaporization, turning into vapor, which rises to the condenser above the tank. The vapor releases heat, condenses back into liquid, and drips back into the tank. Heat transfer primarily occurs through phase change between the liquid and gas phases, and a pump is not necessarily needed to drive the main circulation within the tank.<\/p>\n<p>This method can handle high heat fluxes at near-fluid saturation temperatures, but &quot;boiling&quot; does not guarantee a successful design. Nucleation conditions on the component surface, condenser capacity, tank sealing, vapor management, and operating pressure all affect temperature and coolant loss. If a localized area transitions from nucleation boiling to unstable film boiling, the surface may be separated by a vapor film, worsening heat transfer.<\/p>\n<p>Furthermore, two-phase systems are more sensitive to fluid boiling points and vapor pressures. Open-cell maintenance, seal aging, or insufficient condensation can all cause working fluid leakage. Therefore, initial thermal performance is only the first hurdle; replenishment, recovery, and personnel exposure control must also be factored into the total cost of ownership.<\/p>\n<h2 id=\"single-vs-two-phase\">How to choose between single-phase and two-phase? First, compare six engineering conditions.<\/h2>\n<figure class=\"wp-block-table\">\n<table>\n<thead>\n<tr>\n<th>Comparison items<\/th>\n<th>Single-phase immersion cooling<\/th>\n<th>Two-phase immersion cooling<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Cooling mechanism<\/td>\n<td>The liquid is heated and then circulated to the heat exchanger.<\/td>\n<td>Liquid boils, vapor condenses and then refluxes.<\/td>\n<\/tr>\n<tr>\n<td>In-slot power<\/td>\n<td>Natural convection or pump circulation<\/td>\n<td>Mainly relies on phase change and buoyancy flow<\/td>\n<\/tr>\n<tr>\n<td>fluid conditions<\/td>\n<td>Boiling point higher than normal operating temperature<\/td>\n<td>Boiling point needs to be considered in conjunction with component and system pressure.<\/td>\n<\/tr>\n<tr>\n<td>Control focus<\/td>\n<td>Flow rate, liquid temperature, filtration, pressure drop<\/td>\n<td>Boiling, condensation, sealing, vapor pressure<\/td>\n<\/tr>\n<tr>\n<td>Maintenance risks<\/td>\n<td>Liquid contamination, pump and filter maintenance<\/td>\n<td>Vapor escaping, liquid replenishment and condenser maintenance<\/td>\n<\/tr>\n<tr>\n<td>Import difficulty<\/td>\n<td>The system is relatively intuitive, but the liquid volume is usually large.<\/td>\n<td>High heat flux potential, but also high integration requirements.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/figure>\n<p>This table is not intended to determine which is necessarily better. Single-phase systems are generally easier to manage when hardware upgrades are frequent and maintenance personnel need to frequently open slots; two-phase systems may show advantages when high heat flux is desired, sealing and condensation conditions can be controlled, and the hardware design is optimized for boiling.<\/p>\n<p>When evaluating data center solutions, do not just compare the wattage of the heat sink.<a href=\"https:\/\/www.taichungbro.com\/en\/2024\/11\/06\/tdp\/\" style=\"color: #00c8d7; text-decoration: underline;\">Differences between TDP, rack power and PUE<\/a>This will affect how the facility calculates electricity, cooling, and backup; pumps, condensate, and heat dissipation equipment will still consume energy.<\/p>\n<h2 id=\"fluid-selection-parameters\">When it comes to coolant, you can&#039;t just look at its dielectric properties; what other parameters should you check?<\/h2>\n<p>Dielectric strength is just the bare minimum. The coolant comes into contact with the entire server, not just the chip, so at least the following should be checked:<\/p>\n<ol>\n<li><strong>Thermal properties<\/strong>Specific heat, thermal conductivity, density, viscosity, and the boiling point and latent heat of vaporization required for a two-phase system.<\/li>\n<li><strong>Electrical properties<\/strong>Changes in volume resistivity, dielectric strength, water content, and pollution.<\/li>\n<li><strong>Material compatibility<\/strong>Check whether the wire sheath, connector, sealing ring, label, adhesive, solder joint and heat interface materials are swollen, dissolved or embrittled.<\/li>\n<li><strong>Safety<\/strong>Flash point, flammability, acute exposure, decomposition products and ventilation requirements.<\/li>\n<li><strong>Environmental indicators<\/strong>: GWP, Ozone Depletion Potential (ODP), persistence and wastewater treatment methods.<\/li>\n<li><strong>life cycle<\/strong>Risks include: replenishment, filtration, quality monitoring, recovery and purification, transportation and supply disruptions.<\/li>\n<\/ol>\n<p>Material compatibility must be tested using actual components at the expected temperature; it cannot be determined solely by a summary table from the liquid supplier. Especially...<a href=\"https:\/\/www.taichungbro.com\/en\/2024\/08\/27\/tim\/\" style=\"color: #00c8d7; text-decoration: underline;\">Thermal interface material between chip and heat sink<\/a>If dissolution, pumping out, or changes in mechanical properties occur after prolonged immersion, the local thermal resistance may increase.<\/p>\n<h2 id=\"pfas-risk\">Is every fluorocarbon coolant a PFAS? The key lies in the definition and chemical structure.<\/h2>\n<p>PFAS is a collective term for per- and polyfluoroalkyl substances, but there is currently no single definition that is completely consistent across all studies and regulations.<a href=\"https:\/\/www.oecd.org\/en\/publications\/reconciling-terminology-of-the-universe-of-per-and-polyfluoroalkyl-substances_e458e796-en.html\" style=\"color: #00c8d7; text-decoration: underline;\" target=\"_blank\" rel=\"noopener\">OECD 2021 Report<\/a>One approach offers a broader definition centered on molecular structure; the US EPA, in its TSCA 8(a)(7) filing rule, lists specific structural conditions. Their scopes of work are not entirely the same.<\/p>\n<p>Therefore, regulatory status cannot be determined solely by terms like &quot;fluorinated,&quot; &quot;fluorocarbon,&quot; or product name. The correct procedure is to obtain a Safety Data Sheet (SDS), Chemical Abstracts Service Registry Number (CAS RN), and composition information, and then compare these details with current regulations for the country of sale, use, and disposal.<\/p>\n<p>As of July 2026,<a href=\"https:\/\/echa.europa.eu\/hot-topics\/perfluoroalkyl-chemicals-pfas\" style=\"color: #00c8d7; text-decoration: underline;\" target=\"_blank\" rel=\"noopener\">The European Chemicals Agency (ECHA)&#039;s broad PFAS restriction plan<\/a>The process is still in the regulatory stage, and the Commission&#039;s opinions and possible specific exemptions are still evolving, so it cannot be written as &quot;the EU has completely banned it.&quot; However, for data centers that need to be used for more than 10 years, the ability to maintain the continuous supply, recycling, and cross-border transfer of fluids is a risk that must be taken into account during procurement.<\/p>\n<h2 id=\"deployment-checklist\">Before implementing immersion cooling, complete this checklist.<\/h2>\n<ol>\n<li>First, establish the thermal load using the actual CPU, GPU, power supply, and memory configuration, rather than using the TDP of a single component to replace the requirements of the entire cabinet.<\/li>\n<li>Confirm the immersion warranty conditions for servers, capacitors, cables, connectors, seals, TIMs, and storage devices.<\/li>\n<li>Establish acceptable quality boundaries by conducting accelerated immersion, insulation, contamination, and thermal cycling tests using actual liquids.<\/li>\n<li>Incorporate pumps, heat exchangers, condensers, secondary water circuits, ventilation, and leak detection outside the tank into the system diagram.<\/li>\n<li>Obtain complete SDS, CAS RN, GWP, ODP, PFAS statements and waste liquid recycling solutions; marketing terms that only state &quot;environmentally friendly&quot; are not acceptable.<\/li>\n<li>First, design the processes for slotting maintenance, circuit board dripping, liquid sampling, liquid replenishment, accidental leakage and decommissioning, and then decide on the equipment configuration.<\/li>\n<\/ol>\n<p>If a supplier can only provide initial thermal testing but cannot address issues such as liquid quality, material changes, and recycling responsibilities five years from now, the solution remains incomplete. The reliability of immersion cooling depends on whether mechanical, thermal, electrical, chemical, and maintenance processes can be validated together.<\/p>\n<h2 id=\"choose-system-not-fluid-only\">The choice wasn&#039;t a tank of liquid, but a maintainable thermal management system.<\/h2>\n<p>The advantage of single-phase systems is that control is more intuitive, while two-phase systems utilize boiling and condensation to achieve high heat flux; both can perform well, and both can fail due to poor flow field, sealing, materials, or maintenance design. The suitability of fluorocarbon coolants cannot be judged solely by whether they are &quot;non-conductive&quot; or have a &quot;low boiling point.&quot;<\/p>\n<p>In practice, the selection of a solution should return to three questions: Can heat be stably removed under all load conditions? Can the hardware and fluid coexist in the long term? Are regulations, supply and recycling responsibilities manageable? Only after passing these three tests can we evaluate immersion cooling, rather than just picking a barrel of liquid that looks advanced.<\/p>","protected":false},"excerpt":{"rendered":"<p>Fluorocarbon coolants are not all immersion fluids, and dielectric properties and boiling points should not be the sole considerations. This article compares single-phase and two-phase immersion cooling, analyzes material compatibility, GWP (Gross Power Potential), PFAS (Power Factor Assurance System) definitions, and discusses selection risks.<\/p>","protected":false},"author":5,"featured_media":3772,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[45],"tags":[488,525,523,521,522,526,524],"class_list":["post-3773","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-industrial-knowledge","tag-ai","tag-pfas","tag-523","tag-521","tag-522","tag-526","tag-524"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts\/3773","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/comments?post=3773"}],"version-history":[{"count":0,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/posts\/3773\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/media\/3772"}],"wp:attachment":[{"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/media?parent=3773"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/categories?post=3773"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.taichungbro.com\/en\/wp-json\/wp\/v2\/tags?post=3773"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}