Patent ID: 7824178

Claim:
A water heater apparatus comprising: a horizontally oriented cylindrical heat exchanger having a central combustion chamber defined concentrically within the cylindrical heat exchanger; an elongated burner tube extending axially in a first direction into the combustion chamber, the burner tube having a burner inlet; a variable speed pre-mix blower located above the heat exchanger for providing a fuel-air mixture to the burner tube at variable flow rates, the blower having a blower outlet; and a fuel-air transfer arm connecting the blower outlet to the burner inlet, the transfer arm including a transfer arm inlet connected to the blower and a transfer arm outlet connected to the burner tube, a continuously curved 180° bend portion between the transfer arm inlet and the transfer arm outlet, and at least one inwardly extending internal flow disrupter located in the 180° bend portion, for improving fuel-air mixture distribution across the burner inlet; wherein the internal flow disrupter comprises an inwardly projecting rib extending peripherally around at least a portion of an inside cross-section of the transfer arm, the rib being located in an outside curve of the 180° bend portion of the transfer arm for disrupting a concentration of flowing fuel-air mixture to the outside curve that would otherwise occur due to centrifugal force on the mixture as the mixture flows through the 180° bend portion.