Sr. Thermal Systems Engineer
Flex
USA, MA, Littleton
Contract
$126,500
OfficeExecutive
At JetCool, a Flex company, we’re at the forefront of liquid cooling innovation, delivering advanced solutions that empower our partners in AI and high-performance computing. United by a shared purpose, our teams are pushing the limits of what’s possible and tackling complex challenges.
A career at JetCool offers the opportunity to make a real impact by helping build smarter, more sustainable data centers. Together, we’re not just advancing technology — we’re redefining cooling standards to create a more sustainable tomorrow.
To support our extraordinary teams who build great products and contribute to our growth, we’re looking to add a Senior Thermal Systems Engineer located in Littleton, MA.
Reporting to the Product Manager the Senior Thermal Systems Engineer will own the end-to-end architecture, analysis, validation, and deployment of direct-to-chip (D2C) cooling systems used to cool high-TDP CPUs/GPUs/accelerators. They will be the technical leader partnering with Product Management, Mechanical/Electrical Engineering, Manufacturing, Quality, Reliability, and key customers to deliver robust, scalable products that meet performance, reliability, and cost targets.
What a typical day looks like:
Own thermal architecture & modeling
Define system-level thermal requirements (TDP range, ΔT, coolant temperature, flow rate, pressure drop, acoustic & power budgets).
Apply first principles in fluid dynamics and heat transfer to analyze design concept thermal performance
Build and validate 1D/3D models (e.g., FloEFD, Icepak, MacroFlow, ANSYS Fluent, COMSOL) for cold plates, manifolds, quick-disconnects (QDs), pumps, and CDUs.
Perform sensitivity trade-offs (flow distribution, fin geometry, microchannel optimization, TIM selection, manifold topology).
Design liquid cooling subsystems
Specify and refine cold plates, CDUs, manifolds, hoses/QDs, reservoirs, filters, sensors, and controls.
Collaborate with ME/EE on mechanical stack-up, materials, corrosion mitigation (galvanic compatibility), and leak risk reduction.
Define DFX (DFM/DFA/DFT) and lead EVT/DVT/PVT from prototypes to mass production.
Validate and qualify
Develop test plans for thermal performance, pressure integrity, leak detection, long-term reliability (HALT/HASS), and contamination control (particulates, biogrowth).
Execute lab and rack-scale testing (pump curves, flow balance, ΔP mapping, heat load emulation, transient behavior).
Drive failure analysis and corrective actions (FMEAs, 8D/PPS).
Partner across the business
Work with Product Management on PRDs, roadmaps, and business cases.
Support manufacturing process development (leak/pressure test stations, purge and fill, cleanliness criteria) and supplier selection/qualification.
Engage with customers: define requirements, run pilots, analyze fleet telemetry, and support deployment at scale.
The experience we’re looking to add to our team:
BS/MS in Mechanical Engineering or Aerospace Engineering or related field (PhD a plus).
5+ years experience in thermal design/validation for high-power electronics (preferably data center/server/HPC).
Excellent first principles knowledge in fluid dynamics, thermodynamics, and heat transfer
Proven expertise in liquid cooling, including CFD, pressure drop/flow modeling, and thermal metrology.
Hands-on with lab instrumentation (flow meters, pressure transducers, thermocouples/RTDs, DAQ, leak detectors) and test automation (Python, LabVIEW, or similar).
Experience bringing products from EVT → DVT → PVT → ramp, including DFX and supplier engagement.
Excellent technical communication and documentation skills.
BO18
What you'll receive for the great work you provide:
Application Deadline:
Applications for this job position will be accepted for at least five days following the job posting start date below and continuing until the end date below or until the position is filled. This posting may close sooner due to application volume.
Job Posting Start Date 06-22-2026 Job Posting End DateThe base pay range for this position is provided below. The final base rate offered will be determined using job-related, non-discriminatory criteria, including but not limited to experience, qualifications, geographic location, education, external market data, and internal equity.
$126,500.00 USD - $173,900.00 USD AnnualIs Sponsorship Available?
NoJetCool is an Equal Opportunity Employer and employment selection decisions are based on merit, qualifications, and abilities. We do not discriminate based on: age, race, religion, color, sex, national origin, marital status, sexual orientation, gender identity, veteran status, disability, pregnancy status, or any other status protected by law. We're happy to provide reasonable accommodations to those with a disability for assistance in the application process. Please email accessibility@flex.com and we'll discuss your specific situation and next steps (NOTE: this email does not accept or consider resumes or applications. This is only for disability assistance. To be considered for a position at JetCool, you must complete the application process first).