Thermal Systems Engineer

At Jet. Cool, 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 Jet. Cool 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.

Job Summary

To support our extraordinary teams who build great products and contribute to our growth, we’re looking to add a Jr. Thermal Systems Engineer located in Littleton, MA. Reporting to the Product Manager the Jr. Thermal Systems Engineer will supports thermal-fluid modeling, requirements management, component characterization, testing, and system-performance analysis for liquid-cooling products.

This early-career role offers significant hands-on experience with complete cooling loops and system-level engineering. What a typical day looks like: Support product requirements, specifications, and verification traceability. Develop and update 1D thermal-fluid models. Support CFD and conjugate heat-transfer analysis.

Calculate pressure drop, flow distribution, thermal resistance, heat rejection, and system operating points. Support selection and characterization of pumps, radiators, heat exchangers, tubing, and fittings. Build and instrument prototypes and thermal-fluid test loops. Operate flow meters, pressure transducers, thermocouples, and data-acquisition systems.

Document assumptions, boundary conditions, uncertainty, results, and recommendations. Support investigation of flow imbalance, pressure drop, aeration, cavitation, coolant loss, and thermal-performance issues. Participate in design reviews, troubleshooting, and failure investigations. Improve reusable models, component libraries, and calculation tools.

The experience we’re looking to add to our team: Bachelor’s degree in mechanical, thermal, aerospace, or equivalent practical experience. Typically 0 to 3 years of relevant experience. Strong foundation in thermodynamics, fluid mechanics, and heat transfer. Exposure to CFD, thermal analysis, or 1D fluid-network modeling.

Ability to perform fundamental pressure-drop, energy-balance, pump, and heat-exchanger calculations. Hands-on aptitude and familiarity with laboratory instrumentation. Internship, co-op, or academic experience involving thermal systems, fluid networks, electronics cooling, HVAC, or liquid cooling preferred. Macro. Flow, Cadence Celsius EC, Python, MATLAB, or similar analytical-tool experience is beneficial.

Models and calculations are accurate and well documented. Test setups generate reliable and repeatable data. Analytical predictions improve through test correlation. The engineer assumes progressively more complex and independent assignments. BO18 What you'll receive for the great work you provide: Full range of medical, dental, and vision plans Life Insurance Short-term and Long-term Disability Matching 401(k) Contributions Vacation and Paid Sick Time Tuition Reimbursement 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 10-18-2026 Job Posting End Date 12-31-2026 The 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.

$105,000.00 USD - $144,400.00 USD Annual Job Category Design, Process & Technology Engineering Is Sponsorship Available? No Jet. Cool 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.

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