{"id":2469,"date":"2026-06-19T11:08:14","date_gmt":"2026-06-19T03:08:14","guid":{"rendered":"https:\/\/szfengheng.com\/ai-server-liquid-cooling-fans\/"},"modified":"2026-06-19T21:24:40","modified_gmt":"2026-06-19T13:24:40","slug":"ai-server-liquid-cooling-fans","status":"publish","type":"post","link":"https:\/\/szfengheng.com\/de\/ai-server-liquid-cooling-fans\/","title":{"rendered":"Do AI Servers Still Need Cooling Fans in Liquid Cooling Systems?"},"content":{"rendered":"<p><script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"TechArticle\",\n  \"headline\": \"Do AI Servers Still Need Cooling Fans in Liquid Cooling Systems?\",\n  \"description\": \"Explains why AI servers running liquid cooling still require high-static-pressure fans for RDHx, CDU cooling, and GPU auxiliary airflow in hybrid thermal architectures.\",\n  \"url\": \"https:\/\/szfengheng.com\/ai-server-liquid-cooling-fans\/\",\n  \"datePublished\": \"2026-06-19\",\n  \"dateModified\": \"2026-06-19\",\n  \"author\": {\"@type\": \"Organization\",\"name\": \"Fengheng Technology\",\"url\": \"https:\/\/szfengheng.com\"},\n  \"publisher\": {\"@type\": \"Organization\",\"name\": \"Fengheng Technology\",\"url\": \"https:\/\/szfengheng.com\"},\n  \"mainEntityOfPage\": \"https:\/\/szfengheng.com\/ai-server-liquid-cooling-fans\/\",\n  \"keywords\": \"liquid cooling fans AI server, RDHx fan, CDU fan, 48V DC fan, AI data center cooling\"\n}\n<\/script><\/p>\n<p><script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"FAQPage\",\n  \"mainEntity\": [\n    {\n      \"@type\": \"Question\",\n      \"name\": \"Do AI servers with liquid cooling still need fans?\",\n      \"acceptedAnswer\": {\"@type\": \"Answer\",\"text\": \"Yes. Even fully liquid-cooled AI servers require fans in three places: Rear Door Heat Exchangers (RDHx) need high-static-pressure fans to push air through the water-cooled door panel; CDU (Coolant Distribution Units) require fans to reject heat from the coolant-to-air heat exchanger; and GPU cold plate loops often need auxiliary fans for residual heat removal. Fengheng Technology supplies 48V DC PWM fans rated \u2265350 Pa for all three applications.\"}\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What static pressure do RDHx fans need for AI servers?\",\n      \"acceptedAnswer\": {\"@type\": \"Answer\",\"text\": \"RDHx fans for AI server racks (30\u201360 kW thermal load) require static pressure \u2265300\u2013400 Pa to overcome rear-door heat exchanger resistance. Fengheng Technology 92mm fans deliver 350 Pa and 120mm fans deliver 380\u2013420 Pa at operating speed, covering standard AI GPU rack densities.\"}\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What voltage do AI data center liquid cooling fans use?\",\n      \"acceptedAnswer\": {\"@type\": \"Answer\",\"text\": \"OCP Open Rack v3 standardizes on 48V DC power distribution. AI data center liquid cooling fans should use native 48V DC input to eliminate DC-DC conversion losses. Fengheng Technology offers 48V DC fans from 92mm to 172mm covering RDHx, CDU, and auxiliary cooling applications.\"}\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"How many fans does a 42U AI server rack RDHx need?\",\n      \"acceptedAnswer\": {\"@type\": \"Answer\",\"text\": \"A 42U rack with 30\u201360 kW heat load typically requires 12\u201316 fans in N+1 redundant configuration for the RDHx rear door. Using 92\u00d725mm fans (80 CFM each), a 16-fan array provides 1,280 CFM total airflow \u2014 sufficient for 60 kW dissipation with 10\u00b0C approach temperature.\"}\n    },\n    {\n      \"@type\": \"Question\",\n      \"name\": \"What is MTBF for AI data center liquid cooling fans?\",\n      \"acceptedAnswer\": {\"@type\": \"Answer\",\"text\": \"AI data centers targeting 99.999% uptime require cooling fans with MTBF \u226550,000 hours. Fengheng Technology dual ball bearing fans achieve L10 life \u226550,000 hours at 40\u00b0C ambient operating temperature, qualified through HALT testing and IEC 60068 environmental testing.\"}\n    }\n  ]\n}\n<\/script><\/p>\n<h2>The Misconception: Liquid Cooling Doesn&#8217;t Eliminate Fan Requirements<\/h2>\n<p>When AI infrastructure teams first deploy liquid cooling \u2014 whether Rear Door Heat Exchangers (RDHx), direct liquid cooling (DLC), or immersion cooling \u2014 a common assumption is that fans become unnecessary. The reality is more nuanced. In hybrid liquid-air cooling architectures, which represent the vast majority of deployed AI data centers today, fans remain critical components in at least three distinct subsystems.<\/p>\n<p>This guide explains where fans are still required, what specifications matter for each application, and how to select the right liquid cooling fan for AI server environments running NVIDIA DGX, Meta Grand Teton, OCP Open Rack v3, and similar platforms.<\/p>\n<h2>Where Fans Are Still Required in AI Liquid Cooling<\/h2>\n<h3>1. Rear Door Heat Exchangers (RDHx)<\/h3>\n<p>RDHx systems mount water-cooled panels on the rear of server racks. Hot exhaust air from servers passes through the chilled panel, transferring heat to the building chilled water loop before it enters the data hall hot aisle. The RDHx panel itself creates airflow resistance \u2014 typically 150\u2013300 Pa depending on fin density and chilled water temperature.<\/p>\n<p>Servers alone cannot overcome this added resistance. Dedicated RDHx fans mounted in the door panel boost static pressure to push air through the heat exchanger matrix. For AI GPU racks dissipating 30\u201360 kW, fan arrays of 12\u201316 units in N+1 redundancy are standard, with each fan delivering \u2265350 Pa static pressure.<\/p>\n<h3>2. Coolant Distribution Units (CDU)<\/h3>\n<p>CDU stations circulate chilled water or dielectric fluid to server cold plates. The CDU itself contains a coolant-to-air heat exchanger that rejects heat from the return loop before recirculating to the facility chilled water system \u2014 or in adiabatic configurations, directly to atmosphere. Fans in the CDU cabinet drive airflow across this internal heat exchanger.<\/p>\n<p>CDU fan requirements depend on heat rejection capacity: 15\u201330 kW units typically use 92mm fans, while 40\u2013100 kW CDU stations require 120mm or larger fans for adequate airflow volume at acceptable noise levels.<\/p>\n<h3>3. GPU Cold Plate Auxiliary Cooling<\/h3>\n<p>High-density GPU clusters (NVIDIA H100, H200, B200) use cold plates that contact the GPU die directly, but surrounding components \u2014 VRM voltage regulators, memory modules, NVLink bridges \u2014 still dissipate heat into the chassis airspace. Auxiliary fans maintain positive pressure within the chassis to prevent hotspot formation around these non-liquid-cooled components. These fans typically require 80\u2013120 CFM at 200\u2013300 Pa static pressure.<\/p>\n<h2>Critical Specifications for AI Liquid Cooling Fans<\/h2>\n<table>\n<thead>\n<tr>\n<th>Application<\/th>\n<th>Size<\/th>\n<th>Static Pressure<\/th>\n<th>Airflow<\/th>\n<th>Voltage<\/th>\n<th>MTBF<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>RDHx Array<\/td>\n<td>92mm or 120mm<\/td>\n<td>\u2265350 Pa<\/td>\n<td>80\u2013140 CFM<\/td>\n<td>48V DC<\/td>\n<td>\u226550,000 h<\/td>\n<\/tr>\n<tr>\n<td>CDU Cabinet<\/td>\n<td>120mm or 172mm<\/td>\n<td>\u2265300 Pa<\/td>\n<td>110\u2013350 CFM<\/td>\n<td>48V DC<\/td>\n<td>\u226550,000 h<\/td>\n<\/tr>\n<tr>\n<td>GPU Auxiliary<\/td>\n<td>80mm or 92mm<\/td>\n<td>\u2265250 Pa<\/td>\n<td>60\u2013100 CFM<\/td>\n<td>12V or 48V DC<\/td>\n<td>\u226550,000 h<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Why 48V DC Matters for AI Data Centers<\/h2>\n<p>OCP Open Rack v3 standardizes on 48V DC power distribution throughout the rack. Native 48V DC fans eliminate the need for intermediate DC-DC converters, reducing power conversion losses by 3\u20135%, simplifying the power architecture, and enabling compatibility with OCP BBU (Battery Backup Unit) modules for ride-through during power events.<\/p>\n<p>In large AI clusters (10,000+ GPUs), the cumulative efficiency gain from eliminating fan power converters represents meaningful power savings \u2014 and simplifies compliance with data center PUE targets.<\/p>\n<h2>Fengheng Technology Liquid Cooling Fan Portfolio<\/h2>\n<p>Fengheng Technology (Shenzhen) manufactures industrial-grade cooling fans for AI liquid cooling applications. The complete portfolio for RDHx, CDU, and auxiliary cooling:<\/p>\n<ul>\n<li><strong>92\u00d725mm 48V DC<\/strong> \u2014 8,000 RPM, 80 CFM, 350 Pa \u2014 RDHx arrays, compact CDU<\/li>\n<li><strong>120\u00d725mm 48V DC<\/strong> \u2014 5,500 RPM, 110 CFM, 380 Pa \u2014 CDU stations, OCP Open Rack v3<\/li>\n<li><strong>120\u00d738mm 48V DC<\/strong> \u2014 4,500 RPM, 140 CFM, 420 Pa \u2014 High-density RDHx, large CDU<\/li>\n<li><strong>172\u00d751mm 48V DC<\/strong> \u2014 3,200 RPM, 280 CFM, 480 Pa \u2014 100 kW+ CDU stations<\/li>\n<li><strong>172\u00d751mm EC<\/strong> \u2014 0-10V\/Modbus control, 350 CFM, 520 Pa \u2014 Building automation integrated CDU<\/li>\n<li><strong>240mm Radiator<\/strong> \u2014 2,200 RPM, 180 CFM, 220 Pa \u2014 Edge AI liquid cooling loops<\/li>\n<\/ul>\n<p>All models feature dual ball bearing construction (MTBF \u226550,000 hours), 4-pin PWM speed control, tachometer output, and CE\/RoHS certification. 48V DC models are OCP Open Rack v3 compatible.<\/p>\n<div style=\"background:#f0f6ff;border-left:4px solid #2E75B6;padding:20px 24px;margin:32px 0;border-radius:4px;\">\n<h3 style=\"margin:0 0 8px;color:#1F3864;\">Need AI Server Liquid Cooling Fans?<\/h3>\n<p>Fengheng Technology supplies high-static-pressure 48V DC fans for RDHx, CDU stations, and GPU auxiliary cooling. Sample lead time: 2 weeks. Contact <a href=\"mailto:fengheng@adc-coolingfan.com\">fengheng@adc-coolingfan.com<\/a> or <a href=\"\/ai-liquid-cooling\/\">view the full AI liquid cooling fan portfolio \u2192<\/a><\/p>\n<\/div>\n<h2>Related Technical Guides<\/h2>\n<ul>\n<li><a href=\"\/rdhx-fan-selection-guide-static-pressure-airflow\/\">RDHx Fan Selection: Static Pressure vs Airflow for Rear Door Heat Exchangers<\/a><\/li>\n<li><a href=\"\/cdu-cooling-fan-comparison-92mm-120mm-pwm\/\">CDU Cooling Fan Comparison: 92mm vs 120mm PWM<\/a><\/li>\n<li><a href=\"\/48v-dc-cooling-fans-ai-computing-racks\/\">48V DC Cooling Fans for OCP Open Rack v3 AI Computing Racks<\/a><\/li>\n<li><a href=\"\/gpu-liquid-cooling-auxiliary-fan-mtbf-selection\/\">GPU Liquid Cooling Auxiliary Fan Selection: MTBF \u226550,000 Hours<\/a><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>The Misconception: Liquid Cooling Doesn&#8217;t Elimina [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-2469","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"acf":[],"_links":{"self":[{"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/posts\/2469","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/comments?post=2469"}],"version-history":[{"count":5,"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/posts\/2469\/revisions"}],"predecessor-version":[{"id":2501,"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/posts\/2469\/revisions\/2501"}],"wp:attachment":[{"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/media?parent=2469"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/categories?post=2469"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/szfengheng.com\/de\/wp-json\/wp\/v2\/tags?post=2469"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}