Thermal Systems Engineer

Flex•Littleton, MA

About The Position

JetCool, a Flex company, develops liquid-cooling solutions for AI and high-performance computing. The Jr. Thermal Systems Engineer supports thermal-fluid modeling, requirements management, component characterization, testing, and system-performance analysis for liquid-cooling products. This early-career position provides hands-on experience with complete cooling loops and system-level engineering. The role is located in Littleton, Massachusetts and reports to the Product Manager. The engineer supports product requirements and verification, develops thermal-fluid models, assists with analysis and component selection, and builds and instruments prototypes and test loops. The role also includes documenting analyses and test results, investigating system performance issues, participating in design reviews and troubleshooting, and improving reusable models, component libraries, and calculation tools. Success includes producing accurate, well-documented calculations and reliable, repeatable test data, correlating analytical predictions with tests, and taking on increasingly complex and independent assignments.

Requirements

Bachelor’s degree in mechanical, thermal, or aerospace engineering, 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.

Nice To Haves

Internship, co-op, or academic experience involving thermal systems, fluid networks, electronics cooling, HVAC, or liquid cooling.
Experience with MacroFlow, Cadence Celsius EC, Python, MATLAB, or similar analytical tools.

Responsibilities

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.