What is the difference between a water heater and a dry burner heater? Why can't a dry burner burn water? What's the difference in production?

I've seen the water heater, generally using copper material surface plating or stainless steel, dry heating tube mostly stainless steel, surface with heat sink and without heat sink two kinds. On the difference lies mainly in the heat dissipation surface, water heating tube using the environment in the water, heat dissipation faster, and the water temperature will not be higher than 100 degrees, so the same power than the dry burning tube is shorter than the effective heat dissipation area is smaller, dry burning, in a very short period of time will be damaged. Dry burning heating tube is the opposite. There is enough heat dissipation area, allowing dry burning, generally used in ovens, heaters and so on. Generally also need to limit the temperature or cooling fan, etc., for reference only.