Fluids / Mechanical Engineer, R&D

Fluidstack•Austin, TX

3d•$210,000 - $260,000

About The Position

Fluidstack is seeking a Fluids / Mechanical Engineer for its R&D team. The company's mission is to make humanity more free by deploying civilization-scale infrastructure for AI. They are focused on delivering 10 to 100s of GWs of compute faster than anyone else, rethinking every layer of the stack. This role involves acquiring power, designing and building data centers, and operating them, with teams spanning hardware and software. Speed and scale are key differentiators. The ideal candidate will care deeply about the problem space and be driven by a sense of urgency and a desire to build something that matters. The role offers full autonomy, requiring individuals to own things end-to-end and take on scope without being asked. The team operates with insane urgency, driving everything forward as fast as possible, and encourages reasoning from first principles, challenging assumptions, and allowing the best idea to win. The team is working on rejecting more than 10 gigawatts of heat, designing and building machines because the market cannot supply them at the required rate, and owning every thermofluids problem behind the fleet, from working fluid and cycle architecture to heat exchangers and two-phase heat transfer at the chip, and thermal energy storage. Whatever this team lands will be built thousands of times.

Requirements

Built a thermodynamic cycle model from fluid properties up and defended its assumptions.
Sized real heat exchangers against published correlations and identified when a correlation was misapplied.
Calibrated a model against machine datasheet or test data and reported the gap honestly.
Written analysis that changed a design decision in a readable and actionable format.
Sized a relief path and signed off on system protection.
Held a result open when it was still open, rather than closing it early.

Nice To Haves

Experience with vapor-compression and transcritical cycles (chillers, heat pumps, refrigeration).
Experience with propulsion and cryogenic fluid systems (feed systems, regenerative cooling, two-phase transport).
Experience with piping and relief design for high-pressure fluid systems.
Familiarity with real-gas properties and two-phase heat-transfer correlations (CoolProp, REFPROP, Cavallini, Gnielinski, Wang).
Knowledge of data center thermal architecture (CDUs, dry coolers, direct-to-chip).

Responsibilities

Define the machine's requirements, owning the cycle model that sets the working fluid and the pressures, temperatures, and flows the compressor, turbine, and exchangers are designed against.
Design heat exchangers with surface areas running into millions of square meters.
Design the fluid system around the machine, including piping, valves, headers, and isolation, sized against the pressure-drop budget and actual fluid pressures.
Run trade-offs to decide on the machine's specifications, such as air-side temperature rise, face velocity, and subcooling.
Derive operating points from coupled exchanger ratings rather than asserted approach temperatures to identify infeasible designs early.
Take cycle predictions to the test stand and reconcile them against measured COP, reporting discrepancies between model and reality honestly.
Own thermofluids problems behind the fleet, including working fluid and cycle architecture, large-scale heat exchangers, two-phase heat transfer at the chip, and thermal energy storage.