Abstract: To address the mismatch between end-field concentration and cooling losses in a tubular ozone generator, an axisymmetric multiphysics model coupling the electric field, variable-density flow and conjugate heat transfer was developed, retaining fillets, flat shoulders and a grounded step. Volume-weighted electric-field percentiles were adopted, and dielectric temperature rise, heat-removal pathways and hydraulic dissipation were jointly evaluated under a prescribed 90 W heat load. The baseline end-field concentration factor was 1.0751, the quartz temperature rise was 14.135 K, the water-side net convective heat fraction was 95.92%, and the dissipative pressure drop was 30.808 Pa. The end-field concentration and the dominant heat-removal pathway were identified, providing a basis for structural evaluation under consistent conditions.