Fluids / Mechanical Engineer, R&D

Fluidstack

$110K — $130K *
Technical Services
Less than 5 years of experience
Job Overview by Ladders

Qualifications

  • Experience in building thermodynamic cycle models and defending their assumptions.
  • Proven ability to size heat exchangers against published correlations.
  • Skilled in calibrating models against machine data and reporting discrepancies honestly.
  • Ability to write technical analyses that influence design decisions.
  • Experience in sizing safety relief paths and validating system protection.
  • Track record of maintaining open results during analysis.
  • Bonus: Knowledge of vapor-compression and cryogenic systems, piping design, and data center thermal architecture.

Responsibilities

  • Define machine requirements and own the thermodynamic cycle model.
  • Design heat exchangers with millions of square meters of surface area.
  • Develop fluid systems including piping and valves according to pressure-drop budgets.
  • Manage trade-offs affecting machine performance and validate design feasibility.
  • Reconcile cycle predictions with test stand measurements to identify model inaccuracies.

Benefits

  • Supportive team culture that values exceptional talent.
  • Commitment to pay equity and transparency in compensation practices.
Full Job Description
The Thermofluids R&D Team

Examples of key problems the team is working on
  • Reject more than 10 gigawatts of heat, starting now. Fluidstack is targeting 10 GW of compute in 2027 and 30 GW the year after. Every watt of it becomes heat that has to go somewhere, and no cooling team has ever been asked to open at that number rather than grow into it.
  • Design and build the machines, because nobody can supply them. The merchant compressor market cannot deliver at this rate, and the vendor base behind today's chillers will not scale to gigawatts. We are taking compressor and chiller design in house, working on machine architectures nobody sells today, and going from blank sheet to production faster than this industry thinks is possible.
  • Own every thermofluids problem behind the fleet, not just the chiller. Working fluid and cycle architecture, heat exchangers at a scale that dominates the cost of the plant, two-phase heat transfer at the chip, and thermal energy storage. All of it is open, and whatever this team lands gets built thousands of times.
Role Scope
  • Define what the machine has to be, 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, among the largest single drivers of a data center's physical footprint.
  • Design the fluid system around the machine: piping, valves, headers, relief and isolation, sized against the pressure-drop budget the cycle can afford and the pressures the fluid actually runs at.
  • Run the trades that decide the machine: air-side temperature rise, face velocity and subcooling. Derive the operating points from coupled exchanger ratings rather than asserted approach temperatures, so infeasible designs get caught in the model instead of in hardware.
  • Take the cycle predictions onto the test stand and reconcile them against measured COP, then say plainly where the model was wrong.


What We're Looking For

The below is a starting point. We always make space for exceptional people, so if you don't fit this role exactly, tell us where you would.
  • You've built a thermodynamic cycle model from fluid properties up and defended its assumptions to someone actively trying to break it.
  • You've sized real heat exchangers against published correlations, and you've caught a case where the correlation belonged to a different geometry than the one in front of you.
  • You've calibrated a model against a machine datasheet or test data and reported the gap honestly rather than tuning until it disappeared.
  • You've written the analysis that changed a design decision, in a form that people who never ran the code could read and act on.
  • You've sized a relief path and been the one who signed off that the system was protected.
  • You've held a result open when it was still open, instead of closing it early to be helpful.
  • Bonus: Vapor-compression and transcritical cycles (chillers, heat pumps, refrigeration). Propulsion and cryogenic fluid systems (feed systems, regenerative cooling, two-phase transport). Piping and relief design for high-pressure fluid systems. Real-gas properties and two-phase heat-transfer correlations (CoolProp, REFPROP, Cavallini, Gnielinski, Wang). Data center thermal architecture (CDUs, dry coolers, direct-to-chip).


We are committed to pay equity and transparency.

You will receive a confirmation email once your application has successfully been accepted. If there is an error with your submission and you did not receive a confirmation email, please email [redacted] with your resume/CV, the role you've applied for, and the date you submitted your application-- someone from our recruiting team will be in touch.

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