Heat transfer review – electric immersion heater for heavy crude oil (watt density / film coefficient)

We are a Venezuelan engineering company developing an electric immersion heater for extra-heavy crude oil (tubular sheathed elements, U-shaped hairpins, in an ASME VIII pressure vessel). The thermal design is already done. We need an experienced heat-transfer / process engineer to REVIEW it and give an independent opinion — not to design from scratch.
▎
▎ Service:
▎ - Crude: ~8 °API (Orinoco Belt), highly viscous, with 20–50 % emulsified water
▎ - Heating 70 → 85 °C, line pressure ~4.5 barg (design 10 barg / 200 °C)
▎ - Two models: 100 bbl/d (~9.5 kW) and 600 bbl/d (~53 kW)
▎ - Incoloy 825 sheath, Ø 0.475", no baffles (natural convection dominated)
▎
▎ Questions to answer:
▎ 1. Is a watt density of ~1.5–1.7 W/in² reasonable for this service? What would you use and why?
▎ 2. Is "sheath temperature ≤ water saturation temperature at line pressure − 10 K" the right limiting criterion, or is it too conservative?
▎ 3. Film coefficient: natural convection in a confined tube bundle with viscous crude — what values and correction factor for bundle confinement would you expect?
▎ 4. Would you add baffles? Estimated effect on bundle size vs. pressure drop and fouling.
▎ 5. Is the design basis (ΔT 15 K, 50 % water cut, bare-body losses) appropriate?
▎
▎ Deliverable: a short written report (3–6 pages) with your answers, your own numbers and references, plus one video call to discuss.
▎ We provide: a 3–4 page technical summary and our calculation sheet.
▎
▎ Required: proven experience with heaters, heat exchangers or line heaters for heavy oil / bitumen / fuel oil (please describe a real project). Knowledge of natural convection correlations (Churchill–Chu, etc.). Spanish is a plus.
▎ An NDA will be required.