How should burner flame shape be evaluated when buying a rotating clay-pot cooker?

Flame shape on a rotary claypot rice cooker is not about how big the fire looks. What matters is whether the flame hugs the curved pot base and keeps the temperature gap between the center and outer ring within about 15°C. Check this with an infrared gun at the center, mid-radius and rim of a loaded claypot. Watch that flames do not lick the rim or produce black smoke, and confirm the shape holds steady when several pots run back-to-back. Insist on testing with your own claypots rather than a showroom unit.