Abstract: A humidifier includes a burner for burning fuel within a water tank for generating steam, a primary heat exchanger within the water tank for transferring heat from products of combustion of the fuel to the water within the water tank, and a secondary heat exchanger. The secondary heat exchanger includes a combusted gas section for receiving the cooled products of combustion from the primary heat exchanger and a water section for transferring additional heat from the cooled products of combustion to water flowing within the secondary heat exchanger. The humidifier further includes a secondary fill valve which is pulsed to provide cool water for transferring additional heat from the cooled products of combustion to water flowing within the secondary heat exchanger. The water from a primary fill valve is fed directly into the water tank. An outlet of the secondary heat exchanger is fed directly into the water tank.

Abstract: Today vaporizing humidifier must achieve their desired function and operate with conflicting requirements such as cost of ownership (CoO) and regulatory guidelines. Low CoO requires high injection efficiency, low water consumption, and high energy efficiency to reduce energy consumption and running costs. All of this is sought with variable humidification and low exhaust gas temperatures from safety/regulatory viewpoints as well as ducting material selection and venting of the exhaust gases and high efficiency. To date vaporizing humidifiers have been partially successful utilizing a single stage heat exchanger that could not extract latent energy from exhaust gases because the secondary fluid is boiling water. High exhaust temperature requires high temperature stainless steel exhaust venting.