Humidifier

For use with a forced air furnace having an exhaust flow path for heated waste combustion gas, and having an air flow system including a cool air return duct and a warm air duct, a humidifying system comprising:

• a coiled conduit disposed in the exhaust flow path for directing water through the exhaust flow path wherein at least a portion of the liquid water is vaporized into steam by the transfer of heat from the heated waste combustion gas to the liquid water, said coiled conduit being formed of tubing having rib means thereon for inducing turbulence in the waste gas and a spirally recessed internal surface for inducing turbulence in the water to thereby enhance the efficiency of heat transfer to the liquid water and to dislodge sediment from within said tubing;
• means for introducing liquid water into said coiled conduit;
• flow control means including a pressure regulating means and valve means for controlling the volume flow rate of liquid water introduced into said coiled conduit such that at least a portion of said water passing through said conduit remains unvaporized during each operating cycle;
• means for discharging a mixture of steam and unvaporized water from said coiled conduit into the warm air duct;
• drip collector means in the warm air duct for separating and collecting unvaporized water entering the warm air duct from said coiled conduit;
• and
• means for removing the collected unvaporized water and said dislodged sediment from the warm air duct.