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Thermal-Fluids Mechanical Engineer

Fermilab · Batavia, IL · $88,800–$116,900 a year · Full time

Posted Sep 22, 2026 · We last checked this listing on Oct 6, 2026

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Likely interview questions for this role

Written from this job description, not a generic list. Each one notes what the interviewer is really checking.

About your past

Tell me about a thermal system you designed and saw through installation and first operation.

What they are checking: Whether they have led thermal projects through the full lifecycle the posting describes.

Tell me about directing technicians or other engineers. How did you check their progress?

What they are checking: Whether they can review work and evaluate results as a technical lead.

What would you do

A low conductivity water system is causing corrosion or erosion problems. How would you investigate?

What they are checking: Whether they consider water chemistry, velocity, materials and operations when diagnosing system issues.

Testing shows your system runs hotter than predicted. What do you do?

What they are checking: Whether they dig into the gap between model and reality honestly rather than adjusting assumptions to fit.

How do you work with physicists who need tight temperature stability?

What they are checking: Whether they can turn scientific requirements into engineering specifications.

About the work

How would you size a cooling water system for a set of accelerator magnets and power supplies?

What they are checking: Whether they can apply heat transfer and fluid flow fundamentals to a real load calculation.

What tools do you use for thermal and flow analysis, and how do you validate the results?

What they are checking: Whether they combine simulation with hand calculations and test data.

How do you estimate the manpower and schedule for a major thermal project?

What they are checking: Whether they can plan labor and time realistically, since the role estimates and directs work.

How do you build compliance with DOE orders and codes into a thermal system design?

What they are checking: Whether code and DOE requirements shape their designs from the start.

How do you write a procurement specification for pumps, heat exchangers or chillers?

What they are checking: Whether their specifications get the right equipment from vendors.

Practice this interview out loud.

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The full job description

As published by Fermilab.

The expected hiring range for this position is: $88,800.00-$116,900.00. Please note that the pay range information is a general guideline only. The pay offered to a selected candidate will be determined based on factors such the scope and responsibilities of the position, qualifications of the selected candidate, business considerations, internal equity, and external market pay for comparable jobs. This position is not eligible for referral bonus program and sponsorship assistance. This position is eligible for relocation assistance. About the Role: The Mechanical Support Department of the Accelerator Division within Fermilab is seeking a Mechanical Thermal Fluids Engineer. Under general directions, this individual will be responsible for planning, researching, and developing large/ major engineering projects. They will lead and contribute to areas such as design, procurement, manufacture, installation, testing, and initial operation of thermal systems in compliance with all applicable local, state, and federal regulations, requirements, and standards, and all Department of Energy (DOE) orders. Responsibilities will also include the estimation of manpower, work scheduling, coordinating and directing or managing technicians and other engineers as assigned. Will review progress and evaluate results. What your day-to-day as a Thermal Fluids Mechanical Engineer at Fermilab will look like: • Utilize fundamental mechanical engineering concepts and principles to complete assignments and develop familiarization with the Laboratory’s method of project engineering, from the design stage through review, procurement, fabrication, installation, test, and operation. • Perform mechanical design, analysis, specification, and construction of fluid cooling piping systems that support the operation of the accelerator complex, including the temperature control of beamline components such as magnets, collimators, RF cavities, beam instrumentation, high-powered targets, kickers, and associated beam components. • Participate in and lead efforts related to thermal-fluid system design, piping system fluid flow analysis, and heat transfer analysis. • Learn the operations of existing accelerator fluids systems and provide operations engineering support by troubleshooting system issues and designing upgrades to existing systems to improve their reliability. • Participate in the design of compressible and incompressible thermal fluids systems to support the accelerator. • Write fabrication specifications that involve welding, brazing, bonding, and soldering techniques with materials such as aluminum, stainless steels, copper, brass, PVC, CPVC, PVDF etc. • Work in a team environment and under the supervision of a senior engineer. • Be responsible for directing the activities of drafters, designers, technicians, and skilled trades on their projects. • Occasionally direct the activities of co-op engineering students and interns on their projects. • Communicate with outside vendors, contractors, and fabricators verbally and through written specifications and engineering drawings. • Abide by and be responsible for performing all duties in accordance with all environmental, health and safety regulations and practices pertinent to this position. Skills and Attributes for Success: • Bachelor’s in an applicable Engineering discipline from an ABET accredited institution with 4+ years of engineering experience, or a Master’s or PhD in an applicable Engineering discipline from an ABET accredited institution with 2+ years of engineering experience. Applicable Knowledge, Skills and Abilities Required: • Demonstrated ability to communicate expectations clearly using verbal and written practices with customers / stakeholders, and with team members. • Demonstrated ability to work effectively under the requirements of schedules and shifting priorities. • Demonstrated ability to perform fluid mechanics, thermodynamics, heat transfer, piping network calculations, and engineering mechanics calculations including statics, stress, strain, and deflection. • Basic understanding of electrical engineering concepts such as current, voltages, resistance, frequencies, and speed requirements. • Demonstrated ability to create and read mechanical drawings, including piping and instrumentation diagrams (P&ID) and process piping flow schematics. • Demonstrated ability in performing mass and energy balance calculation on various hydraulic and heat transfer components. • Demonstrated ability in performing heat transfer calculations to size heat exchangers. • Demonstrated knowledge of machine shop practices and techniques. • Demonstrated knowledge of piping flexibility analysis is desirable. • Must have strong computing skills including preparing and documenting engineering calculations, creating 3D models and 2D drawings using CAD software data presentation, and project management activities (cost estimates, schedules). • Familiarity of CAD software for the creation of piping fluid flow network systems is a plus. • Demonstrated ability to creatively solve engineering problems and troubleshoot operational issues. • Knowledge of welding and brazing practices (e.g., TIG, MIG and torch brazing) as related to manufacturing and fabrication of piping is desirable. • Knowledge of materials, metallurgy, and radiation damage of materials is desirable. • Knowledge of codes and standards such as ASME, AISC, CGI, API and ANSI/ASME pressure vessel and piping codes is desirable. • Use of geometric dimensioning and tolerancing on drawings per ASME Y14.5 is desirable. • Skills or experience in AFT Fathom, AFT Arrow, and ANSYS Workbench are desirable. • Skills or experience in AutoCAD Plant are desirable. Work Arrangement: Please note that the described work arrangement is subject to change based on business needs and is not guaranteed to be final. • Onsite: This is an onsite role, and the candidate must be able to work from our Batavia office. Benefits/Perks: Fermilab offers a competitive and comprehensive benefits program, including: • Medical, Dental, Vision and Flexible Spending Accounts • Paid time off • Life insurance • Short and Long-term disability insurance • Retirement benefits • Onsite day care Why Fermilab: Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. We support discovery science experiments in Illinois and locations around the world, including deep underground mines in South Dakota and Canada, mountaintops in Arizona and Chile, CERN in Europe and the South Pole. Pre-Employment Screening: Drug-Free Workplace & Pre-Employment Screening Fermilab is dedicated to fostering a safe, productive and drug-free environment. An offer of employment is contingent upon the successful completion of a background check and drug screening. HSPD-12 In accordance with Homeland Security Presidential Directive 12 (HSPD-12) new employees are required to obtain and maintain a HSPD-12 Personal Identity Verification (PIV) Credential. To obtain this credential, new employees must successfully complete and pass a federal background check investigation. This investigation includes a declaration of illegal drug activities, including use, supply, possession, or manufacture. This includes marijuana and cannabis derivatives, which are still considered illegal under federal law, regardless of state laws. Failure to obtain or maintain such government access authorization could result in the withdrawal of a job offer or future termination of employment. Foreign Government Sponsored Activities Fermilab employees, and certain guest researchers and contractors, are subject to particular restrictions related to participation in Foreign Government Sponsored or Affiliated Activities, as defined and detailed in United States Department of Energy Order 486.1A. Such individuals will be asked to disclose any participation for review by Fermilab's Office of General Counsel. REAL-ID Requirement for access to Fermilab Campus Fermilab requires all members of the public to produce a REAL-ID, or equivalent, to access the Fermilab Campus for interviews or career events. A list of acceptable forms of ID can be found here: https://get-connected.fnal.gov/wp-content/uploads/2021/09/REALID-Documents.pdf . If a candidate is selected for an interview but does not possess any of the equivalent documents, we may schedule a virtual interview. Equal Opportunity Statement Fermilab is an equal opportunity employer. We evaluate qualified applicants without regard to race, color, religion, sex, age, national origin, disability, veteran status, genetic information, and other legally protected categories.

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