# Cooling guides

Liquid Cooling has 8 guides on liquid cooling for AI and high-density data centers, grouped by country.

## General

- [ASHRAE TC 9.9 Liquid Cooling Classes (W17-W45) Explained](https://liquidcooling.fyi/guides/ashrae-tc-9-9-liquid-cooling-classes.md): Understand the ASHRAE Thermal Guidelines liquid cooling classes W17 through W45: supply temperature ranges, delta-T limits, and how to select the right class for your deployment.
- [Direct-to-Chip vs Immersion vs Rear-Door Cooling Compared](https://liquidcooling.fyi/guides/direct-to-chip-vs-immersion-vs-rear-door.md): Compare the three main liquid cooling approaches for AI and high-density data centers: direct-to-chip cold plates, single-phase and two-phase immersion, and rear-door heat exchangers.
- [How to Size a Coolant Distribution Unit (CDU)](https://liquidcooling.fyi/guides/how-to-size-a-cdu.md): Step-by-step guide to sizing a CDU for direct-to-chip liquid cooling: heat load, flow rate, temperature rise, redundancy, and facility integration.
- [Liquid Cooling Market Size and Forecast for AI Data Centers](https://liquidcooling.fyi/guides/liquid-cooling-market-size.md): Market data for data center liquid cooling: $8.3B in 2027, $22.56B by 2032 (22.1% CAGR). Segments by technology, coolant, data center type, workload, and geography.
- [Questions to Ask a Liquid Cooling Vendor Before You Buy](https://liquidcooling.fyi/guides/questions-to-ask-cooling-vendor.md): A practical checklist for data center operators and MEP engineers evaluating liquid cooling vendors: technical specs, warranties, fluid qualification, integration, and commercial terms.
- [Rack Density Trends for AI: From 30 kW to 150+ kW per Rack](https://liquidcooling.fyi/guides/rack-density-trends-ai.md): Track how AI rack power densities have escalated from 30 kW to 150+ kW, driven by NVIDIA GB200 NVL72, AMD Helios, and hyperscale deployment data.
- [Retrofit vs New Build: Liquid Cooling Deployment Strategies](https://liquidcooling.fyi/guides/retrofit-vs-new-build.md): Compare brownfield retrofit and greenfield new-build approaches for liquid cooling: costs, timelines, technical constraints, and decision framework.
- [Water Use and PUE in Liquid-Cooled Data Centers](https://liquidcooling.fyi/guides/water-use-and-pue.md): Understand Water Usage Effectiveness (WUE), Power Usage Effectiveness (PUE), and the trade-offs between water-free and evaporative cooling for AI data centers.