US3884292A - Air-o-space heater means for recovering heat from a fluid steam - Google Patents

Abstract

The present invention constitutes a means for effectuating the partial recovery of heat normally lost through a flue pipe or exhaust stack of a domestic or industrial heating system. Use is made of a plurality of heat pipes secured in a fixed mutual relationship. Said plurality is partially extended into the flue pipe. Heat is axially transferred from the flue pipe and into an air duct that is equipped with a fan. The fan creates convection currents which serve to advance the recovered heat within the heat duct and ultimately back to either the industrial plant or residence wherein the recovered heat may be utilized for whatever heating purpose is desired.

Description

United States Patent 1 1 1111 3,884,292

Pessolano et al. 1 1 May 20, 1975 15 1 AIR-O-SPACE HEATER MEANS FOR 3,779,310 12/1973 Russell 165/105 RECOVERING HEAT FROM A FLU) 3,788,388 l/l974 Barkmann 165/105 X STEAM FOREIGN PATENTS OR APPLICATIONS V [75] inventors: Richard L. Pessolano. Sparta; Robin 554,345 6/1943 United Kingdom 165/105 B. Rhodes, Parsippany, both of NJ. 73 Assignee; [Sahel-mics Inc" Augusta NJ Primary liraminer-Albert W. Davis, Jr.

Attorney, Agem, or Firm-Mel K. Silverman, Esq.

' [22] Filed: June 22, 1973 1211 Appl. No.: 372,525 57 ABSTRACT The present invention constitutes a means for effecl l tuating the partial recovery of heat normally lost 6/l0l through a flue pipe or exhaust stack of a domestic or [51] int. Cl. F28d 15/00 industrial heating system. Use is made of a plurality of Field of Search heat pipes secured in a fixed mutual relationship. Said 237/8, 17; 219/370; 236/1 1, 49; 126/10] plurality-is partially extended into the flue pipe. Heat is axially transferred from the flue pipe and into an air [56] References Cited duct that is equipped with a fan. The fan creates con- UNITED STATES PATENTS vection currents which serve to advance the recovered 1 546 450 7 1925 Meaker 165/179 x heat within the heat duct W ultimately P to either 1 3, 8/1929 the industrial plant or res1dence wherem the recov- 2,092,658 9/1937 ered'heat may be utilized for whatever heating pur- 2,362,940 1 1/1944 pose is desired.

2,529,915 ll/l950 1 Claim, 3 Drawing Figures In I jllll l AIR-O-SPACE HEATER MEANS FOR RECOVERING HEAT FROM A FLUID STEAM BACKGROUND OF THE INVENTION what might be termed a method of heat recycling or of energy conservation.

The theoretical basis of the present invention rests upon developments in an area of heat exchange technology which relate to isothermal devices. One isothermal device which has received considerable note in recent years is a device which is popularly known as a heat pipe. A heat pipe is, in its simplest form, a closed container, normally metallic, employing on its inner surface a capillary wick structure which is essentially saturated with the liquid phase of a working field. The capillary structure may be comprised of grooves, of single or multiple layers of wire screen, or of any other suitable system of capillaries capable of moving the liquid-phase working fluid from a condenser or heat sink end of the heat pipe to an evaporator or heat source end.

The container is also filled with the vapor of the working fluid, and the container is sealed under a partial vacuum such that the vapor and liquid phases of the working fluid are in equilibrium. The heat pipe transfers heat from one area on the external surface of the container to another area by a vaporizationcondensation cycle.

In addition, the heat pipe is a totally closed, mechanically static device capable of axially transporting large quantities of heat in an essentially isothermic fashion. In addition it is not dependent upon gravity for its operation.

The present invention presents, as will be shown below, a novel use of the heat pipe in order to effect the recovery of heat from a fluid steam and, more particularly, from exhaust gases in residential and industrial heating systems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for the recovery of heat from waste gases produced by residential and industrial heating processes.

Another object is to provide a means of conservation of thermal energy.

A yet further object is to provide a means of increasing the efficiency of an otherwise conventional heating system.

A further object is to provide a heat recovery means intended to reduce the cost of operationn of conventional heating systems.

The above objects are obtained'by the insertion of a plurality of heat pipes, disposed in fixed mutual relationship, into the heat exhaust channel of a heating system such as a furnace. Said plurality of heat pipes,

while in no way interfering with the exhaust function of the duct into which they are inserted, will effect the axial transfer of thermal energy through said heat pipes toward those ends of said heat pipes that are opposite to the ends inserted into said exhaust duct. Said opposite ends of said heat pipes, which receive the recovered heat, are enclosed by a second duct, separated by a solid fluid-tight wall from said exhaust duct.

Enclosed within said second duct is a fan. A source of cool air is received at the intake of said fan and advanced into said second duct, across the condenser ends of said heat pipes. The initially cool air is thereby heated by the thermal energy released at said condenser ends of the heat pipes. This heated air is then convected away from the heat pipes and fed back into the residential or industrial building for any use that may be desired.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of the present invention.

FIG. 2 is a perspective schematic view of the present invention inserted into the flue gas exhaust stack of a furnace.

FIG. 3 is a cross-sectional schematic view of the present invention.

DETAILED DESCRIPTION OF THE INVENTION A generalized schematic view of the concept utilized in the present invention is illustrated in FIG. 3. At the top of said figure is illustrated a hot flue gas ex haust duct 10. The duct 10 can be taken as representative of any hot gas exhaust duct coming from such systems as a furnace, an incinerator, a fossil fuel combustion system, a chemical sytem utilizing an exothermic reaction, or any other heat generating apparatus or system. In other words, the duct 10 is to be considered as a generalized hot fluid stream that, in a given instance, one may find exhausting from a residential or industrial structure.

One or more heat pipes 12, which may be mutually secured in what is termed a fin-plate configuration, are extended into the duct 10. The extended portions of the heat pipes 10 will, in most configurations, occupy less than 20 percent of the cross-sectional area of the duct 10. It is to be noted that flue gas temperatures in an oil-fired system can range from 400 F. to 900 F., depending upon the system efficiency as well as upon other factors.

Each heat pipe 10 absorbs a portion of this flue gas heat and transmits it through the solid wall 14 and outside of the exhaust duct 10. The wall 14 prevents any of the gases from escaping from the exhaust duct.

It is to be noted that the transfer of heat from the duct 10 to a second duct 16 occurs in an isothermal fashion. This is to say, because of the isothermal properties of heat pipes, the temperature gradients throughout the system are minimized. The engineering value of such an isothermal heat transfe rvis that thermal stresses within the elements of the present mechanism are reduced to a level not heretofore obtainable in heat transfer technology. Thermal stress, which is caused by large temperature gradients and by differing coefficients of expansion in adjoining materials, generally contributes to a decrease in the structural integrity, and therefore in the effective working life, of many heat transfer devices.

A fan 18 draws in cool air from the surrounding environment (see FIG. 3) and forces it over the length of the finned heat pipe portion 20. This procedure serves to heat the air within the duct 16, which can then be channelled for use in other areas of a house or plant. For example, in a residential application, the hot air duct 16 can easily be fed into the basement area of a house in order to provide additional warmth thereto and also to decrease the total heat load upon the furnace.

A unit of the above described class, when utilized in a flue pipe of a conventional residential furnace, can produce a recovered heat output of between 5,000 and 10,000 BTUs. Such a unit may be provided with a thermostat 22 which serves to control the fan 18. All of said components are UL-approved and may be easily installed into a 6-inch T-duct.

The unit can be used on steam, hot water and warm air systems and thus will operate with any heating system.

A notable feature of the present invention is the ease with which it can be installed, requiring little if any modification of the existing heating system. Once installed, the duct 16 can carry recycled heat to any given area. It will not only dry out dampness and eliminate odors in the basement but will also keep the first level floors more confortable than they would otherwise be.

Another utility of the present heat-recovery system lies in its use with warm air heating systems. In such systems, the recycled heat can be ducted into the return air intake of the furnace, thereby serving to preheat the air and thus increasing the total system efficiency by bringing more heat (if desired) to all parts of the home.

It is to be emphasized that the air coming out of the present heat recovery means 16 is as pure as the air going into the intake side at the fan 18. The design of the present device renders it impossible for contaminated air to be carried with the heat from the stack 10. Said metal barrier 14 seals the stack gases on one side while keeping the newly heated air on the other. Hence, there can be no air flow between the two ducts and 16.

It is to be noted that the first (in duct 10) and second (in duct 16) portions 12 and respectively of the heat pipes may be adjusted in their mutual relative lengths. This is achieved by providing the opening in the wall 14, through which the pipes pass, with an interior threading which is complementary to the exterior threading, or fin structure, of said pipes. Through the rotation of said pipes their axial location can be changed, thus altering the lengths of said first and second portions. Any increase in the length of the first portion 12 will increase the quantity of heat transferred from the duct 10; any decrease in length will reduce the quantity of heat transferred.

Also it is. to be noted that the cool air intake at fin 18 may be equipped with a volumetric flow control.

A particularly compelling aspect of the present heat recovery means is its economics: the only expense entailed in the operation of said means derives from the small amount of electricity which is needed to power the fan 18. Not only is no additional fuel required but, as aforestated, heat normally wasted is extracted by the heat pipes and returned into the basic system.

In a normal residential unti, the present heat recovery means can increase the efficiency of the heating system by approximately 10 percent. This figure is derived from conventional combustion efficiency measurements. It is believed that the expense saved in fuel alone would defray the retail cost of the present heat recovery means within a few months of installation. After such time the additional recovered heat would represent a complete and total savings to the user.

While there is hereby shown and described the preferred embodiments of the present invention, it will be understood that the invention may be embodied otherwise than as herein specifically illustrated or described, and that in the illustrated embodiments certain changes in the details of construction and in the form and arrangement of the parts may be made without departing from the underlying idea or principles of this invention within the scope of the appended claims.

Having thus described our invention, what we claim as new, useful and nonobvious, and accordingly secured by Letters Patent of the United States is:

v l. A means for recovering heat from a first fluid stream, said fluid stream having a defined heat content, comprising:

a. a heat pipe having a first portion and a second portion, said first portion extending into said fluid stream;

.b. a wall proximately disposed to said stream, said wall adapted to confine said stream in order to prevent heat and fluid leakage from said stream, said wall defining the division between said first and second portions of said pipe;

0. means for proving a second fluid stream, said second stream having a different temperature than said first stream, said second stream disposed in thermal contact with said second portion of said heat pipe, wherein heat transfer is effectuated from the fluid stream of higher temperature to the fluid stream of lower temperature;

d. exteriorly accessible means for mutually adjusting the relative lengths of said first and second portions of said heat pipe, wherein the total length of said heat pipe remains constant,

whereby the adjustment of the length of said first portion effectuates a regulation of the quantity of heat transferred between said first and second fluid streams; and

e. a blower control for said second flow stream said blower control serving to maintaining a desired rate of flow of said second flow stream with respect to said second portion of said heat pipe.

Claims (1)

1. A means for recovering heat from a first fluid stream, said fluid stream having a defined heat content, comprising: a. a heat pipe having a first portion and a second portion, said first portion extending into said fluid stream; b. a wall proximately disposed to said stream, said wall adapted to confine said stream in order to prevent heat and fluid leakage from said stream, said wall defining the division between said first and second portions of said pipe; c. means for proving a second fluid stream, said second stream having a different temperature than said first stream, said second stream disposed in thermal contact with said second portion of said heat pipe, wherein heat transfer is effectuated from the fluid stream of higher temperature to the fluid stream of lower temperature; d. exteriorly accessible means for mutually adjusting the relative lengths of said first and second portions of said heat pipe, wherein the total length of said heat pipe remains constant, whereby the adjustment of the length of said first portion effectuates a regulation of the quantity of heat transferred between said first and second fluid streams; and e. a blower control for said second flow stream said blower control serving to maintaining a desired rate of flow of said second flow stream with respect to said second portion of said heat pipe.

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