A downdraft boiler has a ceramic burner plate overlying a horizontal-tube heat exchanger at least the upper tubes of which each have an internal turbulator preventing premature vaporization of the water traversing the heat exchanger. The turbulator can consist of a twisted metal strip whose edges lie along helices.
A gas water heater device includes a combustion chamber for providing a gas flow, a pipe assembly, and a heat exchanger disposed over the combustion chamber including a plurality of thermal conductors disposed in parallel with each other, each of the plurality of thermal conductors further comprising a base, a plurality of through holes accommodating the pipe assembly therethrough, and a flange for collecting condensed water formed on the base.
