Recuperative furnace system for space air and domestic hot water

Claim 1

A method of heating space air, comprising the steps of: burning a fuel to provide combustion products; raising the dew point of said combustion products; transferring sensible heat and heat of condensation from said dew point elevated combustion products to a liquid in a tube of a first heat exchanger wherein said dew point elevated combustion products and said liquid move in counter-flow directions; conveying said liquid to a second heat exchanger and transferring heat from said liquid to space air in said second heat exchanger wherein said liquid and said space air are moved in substantially counter-flow directions; and conveying said liquid so cooled by said space air in said second heat exchanger in a loop back to said first heat exchanger to be reheated by dew point elevated combustion products.

Claim 2

A method of heating space air, comprising the steps of: burning a fuel to provide combustion products; raising the dew point of said combustion products; transferring sensible heat and heat of condensation from said dew point elevated combustion products to a liquid in a tube of a first heat exchanger wherein said dew point elevated combustion products and said liquid move in counter-flow directions; conveying said liquid to a second heat exchanger and transferring heat from said liquid to space air in said second heat exchanger wherein said liquid and said space air are moved in substantially counter-flow directions; and conveying said liquid so cooled by said space air in said second heat exchanger in a loop back to said first heat exchanger to be reheated by dew point elevated combustion products.

Claim 8

A method of heating space air, comprising the steps of: burning a fuel to provide combustion products; raising the dew point of said combustion products; passing said dew point elevated combustion products upwardly across the fins of a recuperative heat exchanger having water passing through tubes thereof so that said dew point elevated combustion products are cooled below said elevated dew point thereby resulting in said dew point elevated combustion products condensing on said fins wherein the condensate so formed drains down said fins counter to the flow of said dew point elevated combustion products maintaining said fins in a substantially continuous wet state; conveying said water from said recuperative heat exchanger to a remote space air heat exchanger; conveying said water through tubes in said space air heat exchanger while passing said space air across fins coupled to said tubes, said space air moving counter-flow to a direction of said water in said tubes so that said space air is heated to a temperature of 120° F. or more and said water is cooled to a temperature below said elevated dew point of said combustion products; and conveying said water from said space air heat exchanger in a loop back to said recuperative heat exchanger to be reheated by dew point elevated combustion products.

Claim 9

A method of heating space air, comprising the steps of: burning a fuel to provide combustion products; raising the dew point of said combustion products; passing said dew point elevated combustion products upwardly across the fins of a recuperative heat exchanger having water passing through tubes thereof so that said dew point elevated combustion products are cooled below said elevated dew point thereby resulting in said dew point elevated combustion products condensing on said fins wherein the condensate so formed drains down said fins counter to the flow of said dew point elevated combustion products maintaining said fins in a substantially continuous wet state; conveying said water from said recuperative heat exchanger to a remote space air heat exchanger; conveying said water through tubes in said space air heat exchanger while passing said space air across fins coupled to said tubes, said space air moving counter-flow to a direction of said water in said tubes so that said space air is heated to a temperature of 120° F. or more and said water is cooled to a temperature below said elevated dew point of said combustion products; and conveying said water from said space air heat exchanger in a loop back to said recuperative heat exchanger to be reheated by dew point elevated combustion products.

Claim 19

A method for heating space air, comprising the steps of: providing a first heat exchanger having fins surrounding a tube having an inlet disposed above a corresponding outlet; providing a second heat exchanger having fins surrounding a tube having an inlet disposed above a corresponding outlet; recirculating water in a loop between said first and second heat exchangers wherein said water enters said respective tube inlets of said first and second heat exchangers and flows in a downwardly direction to said respective tube outlets; directing hot combustion products upwardly across said fins of said first heat exchanger so that sensible heat and heat of condensation are transferred from said combustion products to said water flowing downwardly in said first heat exchanger tube; directing said space air upwardly across said fins of said second heat exchanger so that said space air is heated by said water in said second heat exchanger tube and said water is thereby cooled below the natural dew point of said combustion products; and raising the dew point of said combustion products before entry into said first heat exchanger thereby providing sufficient condensation within said first heat exchanger to maintain said fins in a substantially continuous wet state.

Claim 20

A method for heating space air, comprising the steps of: providing a first heat exchanger having fins surrounding a tube having an inlet disposed above a corresponding outlet; providing a second heat exchanger having fins surrounding a tube having an inlet disposed above a corresponding outlet; recirculating water in a loop between said first and second heat exchangers wherein said water enters said respective tube inlets of said first and second heat exchangers and flows in a downwardly direction to said respective tube outlets; directing hot combustion products upwardly across said fins of said first heat exchanger so that sensible heat and heat of condensation are transferred from said combustion products to said water flowing downwardly in said first heat exchanger tube; directing said space air upwardly across said fins of said second heat exchanger so that said space air is heated by said water in said second heat exchanger tube and said water is thereby cooled below the natural dew point of said combustion products; and raising the dew point of said combustion products before entry into said first heat exchanger thereby providing sufficient condensation within said first heat exchanger to maintain said fins in a substantially continuous wet state.

Claim 35

A method of heating space air, comprising the steps of: providing a recuperative heat exchanger having fins surrounding a tube which has an inlet to said heat exchanger that is located above a corresponding outlet; providing a space air heat exchanger having fins surrounding a tube which has an inlet and a corresponding outlet; recirculating water in a loop between said recuperative heat exchanger and said space air heat exchanger, said water entering said respective inlets of said tubes and flowing to said respective outlets; locating a water reservoir below said recuperative heat exchanger; contacting hot combustion gases with said water in said reservoir to elevate the dew point and lower the temperature of said hot combustion gases; directing said dew point elevated combustion gases upwardly across said recuperative heat exchanger in counterflow to said water in said tube of said recuperative heat exchanger, said dew point elevated combustion gases being provided at a given dew point and temperature where said liquid in said tube within said recuperative heat exchanger cools said combustion gases such that a substantial majority of the water vapor in said combustion gases condenses on said recuperative heat exchanger wherein a steady state cycle of condensation and evaporation is maintained where condensate flows back downward said fins in said recuperative heat exchanger into said reservoir at the same time said hot combustion gases reevaporate water in said reservoir for subsequent condensing on said heat exchanger; and directing a flow of space air across said fins in said space air heat exchanger in counter-flow to said water in said tube of said space air heat exchanger to heat said space air and cool said liquid to a temperature substantially below the natural dew point of said combustion products.

Claim 36

A method of heating space air, comprising the steps of: providing a recuperative heat exchanger having fins surrounding a tube which has an inlet to said heat exchanger that is located above a corresponding outlet; providing a space air heat exchanger having fins surrounding a tube which has an inlet and a corresponding outlet; recirculating water in a loop between said recuperative heat exchanger and said space air heat exchanger, said water entering said respective inlets of said tubes and flowing to said respective outlets; locating a water reservoir below said recuperative heat exchanger; contacting hot combustion gases with said water in said reservoir to elevate the dew point and lower the temperature of said hot combustion gases; directing said dew point elevated combustion gases upwardly across said recuperative heat exchanger in counterflow to said water in said tube of said recuperative heat exchanger, said dew point elevated combustion gases being provided at a given dew point and temperature where said liquid in said tube within said recuperative heat exchanger cools said combustion gases such that a substantial majority of the water vapor in said combustion gases condenses on said recuperative heat exchanger wherein a steady state cycle of condensation and evaporation is maintained where condensate flows back downward said fins in said recuperative heat exchanger into said reservoir at the same time said hot combustion gases reevaporate water in said reservoir for subsequent condensing on said heat exchanger; and directing a flow of space air across said fins in said space air heat exchanger in counter-flow to said water in said tube of said space air heat exchanger to heat said space air and cool said liquid to a temperature substantially below the natural dew point of said combustion products.