• Self-Resonant Frequency, a type resonance in electronic circuit
• Server Response File
• Ship Repair Facility (one of several US Navy installations)
• Serum response factor, molecular biology term
• Solid recovered fuel also called refuse derived fuel, fuel produced by shredding municipal solid waste
• Superconducting RF, electrical superconductors yielding high Q-factor

Other:

• Self-Realization Fellowship, spiritual organization
• SleepResearch_Facility, a dark ambient artist from Glasgow, Scotland
• Smooth Rock Falls, Ontario
• Spec Racer Ford, a class of racing car
• SRF Limited, a company
• SRF Overseas Limited
• Strategic Rocket Forces, part of Russian army that controls the nuclear rocket weapons
• Sweden Rock Festival
• Systematic Reconnaissance Flight