The Thinking Layer

Data center · Cooling

What each accelerator asks of your cooling plant

Cooling, more than power, decides what a room can host. Some products run in any air-cooled room, some come either way, and the largest cannot run without liquid piped to the rack.

Three tiers

Air only–

Cards and servers cooled by chassis fans. They fit an existing room if it can supply the airflow.

    Air or liquid–

    Sold in both forms. The liquid version is denser: the same eight GPUs in 4U, not 8U to 10U. One more product, AMD's MI440X, has no published cooling figure.

      Liquid required–

      No air-cooled version exists. The site needs coolant piping and a cooling distribution unit.

        The two heat paths

        Air cooling
        ChipHeat spreads into a finned heatsink.
        Chassis fansPull room air front to back, about 105 CFM per kW.
        Hot aisleAir leaves 16 to 17 °C warmer than it entered.
        Room air handlerCools the air and returns it to the cold aisle.
        OutdoorsChiller or cooling tower rejects the heat.
        Direct liquid cooling
        ChipA cold plate sits directly on the processor.
        Rack manifoldFeeds every tray; coolant warms about 13 °C (as water).
        Cooling distribution unitPumps the rack loop and passes heat to facility water.
        Facility waterCarries the heat out of the building.
        OutdoorsAt 45 °C supply, often a dry cooler with no chiller.

        Figures in these strips are calculated from the published specifications below. The note on dry coolers is general engineering practice, not a vendor claim: coolant supplied at 45 °C is warmer than outdoor air in most US climates for most of the year, so it can be cooled without refrigeration once heat-exchanger temperature differences are allowed for; the hottest sites still need some assistance.

        Air-cooled systems: airflow and inlet temperature

        SystemMaximum drawAirflowInlet air allowedExhaust riseAirflow per kW
        NVIDIA DGX H20010.2 kW1,105 CFM5 to 30 °C16.2 °Ccalc.108 CFMcalc.
        NVIDIA DGX B20014.3 kW1,550 CFM10 to 35 °C16.2 °Ccalc.108 CFMcalc.
        NVIDIA DGX B30014.5 kW1,500 CFM1,350 CFM with DC busbar10 to 30 °C17.0 °Ccalc.103 CFMcalc.

        Draw, airflow and inlet limits are from NVIDIA's user guides. Exhaust rise assumes maximum draw at the listed airflow and sea-level air. NVIDIA states airflow at 80% fan speed for the H200 and 70% for the B300, so fans running faster would lower the rise; the B300's busbar version at 1,350 CFM gives 18.9 °C. the working is on the methods page.

        The newer system tolerates less: the B300's inlet ceiling is 30 °C against 35 °C for the B200. Three AC-powered B300 systems in one rack need about 4,500 CFM and put 43.5 kW into the hot aisle.

        AMD and Intel servers are sold by server makers who publish power supply sizes but not airflow, so they are missing from this table. Ask the maker for airflow at your inlet temperature before committing.

        Liquid-cooled systems: what the loop must deliver

        SystemHeat loadShare to liquidCoolant inletFlowCooling distribution unit
        NVIDIA GB200 NVL72132 kWmakerabout 192 kW electrical peakabout 87%calc.115 kW liquid, 17 kW airup to 45 °Cmaker65 °C maximum return (QCT)up to 130 L/minmakerQCTIn-rack 250 kW, in-row 1.3 MW, or 180 to 240 kW liquid-to-air (Supermicro)maker
        NVIDIA GB300 NVL72132 kW nominalmaker155 kW peakabout 90%est.up to 45 °Cest.not publishedIn-row 1.3 MW for up to 8 racks (HPE); in-rack 250 kW, in-row 1.8 MW, or 200 kW liquid-to-air (Supermicro)maker
        NVIDIA Vera Rubin NVL72up to 240 kWmaker98 to 100%est.45 °Cabout 271 L/mincalc.assumes GB200's temperature rise, coolant as waterNo in-rack option: in-row 1.8 MW, or 200 kW liquid-to-airmaker
        NVIDIA HGX Rubin NVL8about 24 kW per 2U nodeest.not publishednot publishednot publishedIn-rack, in-row or liquid-to-airmaker
        AMD Instinct MI355X (4U liquid server)up to 13.2 kWcalc.not published43 °C maximumnot publishednot published
        AMD Helios rack246 kWest.not publishednot publishednot publishedNamed in a partner reference design; capacity not statedest.

        In-rack unit

        Sits in the rack it serves and connects to facility water. Rated 250 kW in the documents found, so one unit per rack.

        In-row unit

        A separate cabinet serving a row. HPE's 1.3 MW unit serves up to eight GB300 racks: eight racks at the 155 kW peak is 1,240 kW, inside its rating.

        Liquid-to-air unit

        For rooms with no facility water. It moves the heat from coolant into room air, so the room's air handling must still remove all of it. The 200 kW rating listed is below Vera Rubin's 240 kW maximum; confirm sizing with the maker.

        What to ask a vendor

        Coolant chemistry, flow at your supply temperature, pressure drop across the rack, and what happens to the 2 to 13% of heat that still leaves as air.

        Every product by cooling type

        Figures come from public vendor, server-maker and press sources, last checked on October 7, 2026. How the numbers were sourced