Abstract: The method is intended for heating water used in an appliance connected into a domestic water circuit comprising a feed branch for continuously feeding hot water to said appliance and a discharge branch for discharging the water from the appliance; it comprises a first stage in which a first quantity of heat withdrawn from the water passing through a first portion of said discharge branch is transferred to the water passing through a first portion of said feed branch, said first stage being carried out by means of a first heat exchanger traversed by the water of said feed and discharge branches, and a second stage in which a second quantity of heat given up by a fluid traversing the condenser of a heat pump is transferred to the water passing through a second portion of said feed branch which is downstream of said first portion, said second stage being carried out by means of a second heat exchanger traversed by the water of said feed branch and by said fluid, said second quantity of heat being partly supplie

Abstract: A heat exchange system for recycling waste heat, such as that leaving a building stack or flue, to supply heat where needed, such as to incoming fresh air or to tempered stored water of the building water storage system, wherein the building has a source of heat at a constant temperature (such as a furnace, a cooking facility, or a washing facility), from which waste heat is involved in the materials to be conveyed therefrom for discharge from the building, in which a closed circuit heat generated refrigerant flow type refrigeration system is established including a heat recovery coil in heat exchange relation to the waste heat, a heat discharge coil in heat transfer relation to the fluid to be heated at a level above that of the heat recovery coil, and a refrigerant receiver at a level adjacent the level of the heat recovery coil, with the system being charged with a halogenated hydrocarbon type refrigerant to bring the liquid level of the charge within the receiver above the level of the heat recovery coil

Abstract: An osmotically pumped environmental control system (10) comprises a closed circuit heat pipe (12) including an osmotic pump (13) with solvent and solution reservoirs (18, 14) separated from one another by a solvent permeable membrane (20). Heat is inserted into the closed path at an evaporator (22) from high temperature sources and heat is wihdrawn from the system by first and second stage cooling modules (38, 40) to withdraw heat therefrom. A further heat input (30) from low temperature sources slightly warms the condensate for return to a solvent reservoir (18).

Abstract: An apparatus and method are provided for removing deposits from material such as drill pipe by subjecting such material to extremely high temperatures in a flame fired furnace. Heated air passing over the material carries with it the volatized deposits and is recirculated within the furnace. As the deposit laden air is recirculated to the burner, the deposits are burned in the flame, thus substantially eliminating the exhaust of contaminants into the surrounding atmosphere.

Abstract: For a shower for a household, dormitory or the like, which typically has a limited volume of boiler-heated water available for use, the cold water input to the shower is passed in heat exchange with the discharging tepid water to thereby convert same to a lukewarm water source, the temperature change being typically a 15 to 25 degree rise, whereby significantly less boiler-heated water is required for preparing a suitable tepid water mixture confortable for showering. The aforesaid significantly prolongs the showering service use of the system and, since less boiler-heated water is consumed, correspondingly lessens the fuel consumption of the boiler.

Abstract: Recuperator burner for industrial furnaces with a central fuel tube which ads the gaseous fuel into a combustion chamber, which tube is concentrically surrounded by a combustion-air supply tube, the outer surface area of the combustion-air supply tube in the area of the recuperator being able to be applied with the exhaust gases which are guided in counterflow through an outer jacket tube and in which combustion-air supply tube there is arranged a first tubular separation wall. The separation wall first guides the combustion-air stream on the way to the combustion chamber along the central fuel tube up to the outlet-side end range of the fuel tube and then redirecting the combustion-air stream in reversed direction.

Abstract: Heat exchange is effected in a simple and economical manner by allowing natural flow, i.e., without mechanical compressors, pumps, etc., of a heat exchange fluid such as a conventional refrigerant liquid between two heat exchangers which are exposed to air at different temperatures. The two heat exchangers, which may conveniently take the form of fin-tube heat exchangers, for example, are arranged with one end at a higher elevation than the other, the upper ends of the two exchangers being connected in direct communication and the lower ends being likewise connected.

Abstract: A heat exchange apparatus is illustrated, which may be used as in a stream of solar heated air for heating flowing water, wherein an array of heat pipes is utilized in heat exchange relation with a manifold, wherein vapor medium is exchanged therebetween for conducting heat from one to the other.

Abstract: A heat pipe heat exchanger in which heat is transferred from hot fluid in duct 12 to cold fluid in duct 14 by a continuous cycle of evaporation and condensation of a liquid contained in heat pipe 26. Should the heat pipe not function properly, the transfer of heat to that portion of the heat pipe lying in the duct for cold fluid will be reduced partially or completely. This reduction in temperature at the end of the heat pipe lying in the duct for the cold fluid is immediately sensed by a thermocouple 54 and indicated upon a gauge 56 which is adapted to identify a particular heat pipe. Repair or replacement of a faulty heat pipe will return each heat pipe to its maximum effectiveness.

Abstract: The system described is useful in connection with a gas compressor that has a heat exchanger. Water conduits, a water pump and water control valve and cooler are connected in such a manner that the water circulated through the heat exchanger is directed to an energy consumption device wherein the heat is extracted to heat a room, office or the like. The control valve and cooler are arranged in the conduit so that the energy consumption device can be selectively bypassed by all or a portion of the water, depending on the heating demand.

Abstract: A continuous process for heating a fluid by recovering heat from a heated, pumpable aqueous slurry of granular material wherein the slurry is passed through an indirect heat exchanger to heat the fluid and then passed to a second indirect heat exchanger to preheat water for forming of further heated, pumpable slurry, with the slurry next passed to a third indirect heat exchanger to heat makeup water to the system and then to a thickener wherein the granular material is separated and the water recovered from the thickener is returned to the system.

Abstract: A system for air cooling a fluid which has been heated through use in an industrial process in a plant and utilizing the air used for cooling, which has now been heated, for providing heated, make up air within a desired temperature range to that plant.

Abstract: A self-contained service module incorporates a water cooled internal combustion engine as a primary power source which drives a low-pressure, high volume forced air ventilation system; a water cooled, high-pressure air compressor; and an alternator. Large diameter steel tubing is utilized as a basic framework for the system and provides a dual function by supporting the primary components of the system and by serving as a reservoir for the high-pressure air. A heat exchange radiator is provided to remove heat from the engine and air compressor cooling liquid and heat the low-pressure air in the ventilation system. When heated air is not required, the radiator is moved to a second position so that air passing therethrough is exhausted from the unit and fresh air at ambient temperatures is provided by the ventilation system.

Abstract: There is disclosed a process and apparatus for the recovery of heat from exhaust or waste gases having a temperature of from about 500.degree. F. to about 2500.degree. F. generated in a process operation having at least two heat recovery assemblies, each utilizing like or different intermediate heat transfer mediums to recover heat at higher heat temperature levels.

Abstract: A self-contained service module incorporates a water cooled internal combustion engine as a primary power source which drives a low-pressure, high-volume forced air ventilation system; a water-cooled, high-pressure air compressor; and an alternator. Large diameter steel tubing is utilized as a basic framework for the system and provides a dual function by supporting the primary components of the system and by serving as a reservoir for the high-pressure air. A heat exchange radiator is provided to remove heat from the engine and air compressor cooling liquid and heat the low-pressure air in the ventilation system. When heated air is not required, the radiator is moved to a second position so that air passing therethrough is exhausted from the unit and fresh air at ambient temperatures is provided by the ventilation system.

Abstract: A heat exchanger and process having multiple fluidized beds for heat exchange between two gas streams of different temperatures. The apparatus and process provides a compact high efficiency warm air furnace especially adapted for energy conservation for the heating of modern highly insulated residential buildings by gas fired furnaces of relatively low rated gas input.

Abstract: To prevent the formation of ice at the inlet portal of a mine and to heat air during the winter season, air is heated and forced into the mine shaft near the entrance portal at a pressure greater than atmospheric.

Abstract: Method and device for defrosting or deicing heat exchangers of the type in which a stream of warm, moist gas, such as warm, used ventilating air--so-called exhaust air--exchanges heat with a cooler medium, such as incoming fresh air, in a contact apparatus, and in which the two media flow through a large number of parallel layers separated from each other by thin walls.

Abstract: A heating and cooling system utilizing solid waste for selectively heating and cooling a confined area. The heating and cooling system comprises a pyrolytic incinerator which is capable of combusting the solid waste in an oxygen lean atmosphere. A fan is used to supply outside air to the pyrolytic incinerator to support combustion therein. The fan is also used to exhaust the flue gases through an exhaust system. An afterburner is located in the exhaust duct of the incinerator to allow further combustion of waste gases which have become mixed with the outside air during combustion of the solid waste. A heat exchanger is located in the exhaust duct downstream of the afterburner and transfers the heat of the outside air and waste gas combustion products to heating water passing through the heat exchanger.

Abstract: A system for recovering and utilizing, to a controlled and variable extent, waste heat from a coolant fluid. The amount of heat recovery varies in proportion to the marginal costs associated therewith. Heat laden coolant passes through an interior heat exchanger where heat may be extracted in varying amounts from the coolant by a thermostatically-controlled air mover, the air mover admitting outside air past the interior heat exchanger. The coolant proceeds to an exterior wet surface heat exchanger where residual heat is concurrently extracted from the coolant by a thermostatically-controlled combination of ambient air, recirculated ambient air, and water spray. The coolant then returns to the beginning of its cycle. The temperature of outside air is the principal variable determining the proportion of heat recovered by the interior heat exchanger and the proportion extracted by the exterior heat exchanger. The total heat extracted reduces the coolant temperature to a predetermined operating level.

Abstract: A system for heating and ventilating objects and spaces surrounded by an outer covering, such as rooms in buildings. The system includes a heat pumping device for converting low-temperature energy to high-temperature energy useful for heating purposes. The condenser as well as the evaporator of the heat pumping device are divided into several series-connected sections operating at progressively or step-wise decreasing condenser temperatures and progressively increasing evaporator temperatures. The outer covering of the space or object to be heated contains an air inlet system and an air outlet system, each of said systems having several series-connected sections located at different distances from the outer surfaces of the covering, thus being subjected to different temperatures related to the temperature gradient through the outer covering.

Abstract: A method for making a heat pipe panel comprising the steps of forming parallel furrows in a sheet metal plate, covering the sheet metal plate with another plate, bonding the plate together around the edges and between the furrows, to form parallel cavities between the plates, charging the cavities with working fluid and sealing the cavities to form individual heat pipes in the panel. The furrows may be filled with wicking material, and capillary grooves may be cut in the furrows before bonding the plates together. The cover plate also may have furrows formed therein. A header furrow may be provided for the fluid charging operations.

Abstract: A closely coupled two phase heat exchanger. The heat is transferred between gas streams by multiple intermediate fluid paths. Each of the several intermediate fluid paths passes alternately between the hot and the cold gas stream many times during its travel from the pump. The heat exchanger is designed so that the intermediate fluid vaporizes in the hot and condenses in the cold section each time, thereby minimizing the quantity of liquid necessary to transfer the heat. The pumping action for the intermediate fluid exchanger is accomplished by either mechanical or vapor pumps. An added feature of the heat exchanger is automatic control of the minimum temperature to which the hot gas is cooled. This is accomplished by shutting off one of several intermediate fluid paths at the cool end of the gas being cooled. The shutoff is accomplished either on the basis of temperature of the cooled gas or on the formation of condensates at the cool end of the gas flow path.

Abstract: Apparatus for controlling the relative rates of flow of gases through a pair of ducts including a bellows chamber defining a substantially enclosed interior and a partition member movably mounted within the chamber dividing the interior thereof into first and second partial volumes which are fluidly sealed from each other. The first partial volume is in fluid communication with a first duct in which a gas flows while the second partial volume is in fluid communication with a second duct in which a gas flows such that a change in the rate of flow of a gas through one of the ducts changes the pressure in the associated partial volume whereby the partition member will move to accommodate the same. A linkage is associated with the partition member for transmitting the movement thereof to a damper located in one of the ducts such that the gas flow opening provided by the damper in the duct is regulated by the extent of movement of the partition member.

Abstract: Bidirectional heat exchangers and elements for use therein are provided for application in buildings and other enclosures to introduce fresh outside air and to remove exhaust air while coincidently recovering heat from the warmer air and using it to adjust the temperature of the cooler air.

Abstract: In an apparatus for making wood and/or paper products from raw wood, the exhaust gas from the boiler that is employed for generating steam is used to heat the drying gas that is passed through the dryer. An air-to-air heat exchanger is used to transfer the heat energy from the exhaust gas to the drying gas.

Abstract: In a system having an electrical apparatus dissipating thermal energy, an apparatus compartment is provided to substantially surround the apparatus, and a blower, disposed in an inlet air compartment, forces air through the apparatus compartment to an exiting air directing assembly where the heated air is selectively directed to a building structure, or to the outside atmosphere. A temperature responsive control assembly selectively directs a portion of the exiting air to the building structure. Suction air to the blower is selectively provided from the building structure or from outside air, the selection of which is selected by another temperature responsive control assembly.

Abstract: A heat exchange system for recycling waste heat leaving a building stack to supply heat to incoming fresh air or temper stored water of the building water storage system, wherein the building has a source of heat at constant temperature, such as a cooking facility, from which air conveying waste heat is drawn and impelled through a stack in which a closed circuit heat generated refrigerant flow type refrigeration system is established including a heat recovery coil in the stack, heat discharge coils in heat transfer relation to the incoming fresh air and the stored water, liquid refrigerant traps that permit free flow therethrough of the refrigerant adjacent the heat discharge coils adjacent their discharge ends, and thermostatically controlled valves for alternately disconnecting the heat discharge coils from the heat recovery coil in accordance with a predetermined ambient air temperature exteriorally of the building.

Abstract: A heat exchanger operatively arranged, like a sliding drawer in a dresser, to be urged through opposite direction sliding movement to facilitate its positioning at and removal in relation to a heat exchange station within a flue, or the like, of a heating system, with the result that it is readily easy to service and maintain the unit clear of soot and other clogging materials. Since, as noted, the problems associated with clogging are significantly obviated, the heat exchanger, among other advantages, can embody in its construction closely spaced heat exchange fins to greatly enhance the amount of heat extracted from the exiting flue gases.

Abstract: The apparatus comprises a first container for receiving waste water. Inlet means in the upper portion of the first container are adapted to be connected to a drain pipe. Outlet means in the bottommost portion of the container are provided for draining the waste water from the container. Valve means are provided which are operable to control the outlet means in response to a waste water level and relative heat indicator in said first container, and a second container for receiving a liquid is adjacent but sealed from said first container. Heat pump means include heat exchanger means in said first container and communicate with heat exchanger means in the second container whereby heat is extracted from relatively warm waste water in the first container and can be transferred to the heat exchanger in said second container for warming a relatively cooler liquid in said second container.

Abstract: This invention relates to an improvement in a heat exchanger of the type using heat pipes which permits reduction in size of the heat exchanger and enhancement in heat exchange efficiency and more particularly to a cylindrical heat exchanger principally comprising a cylindrical or polygonal tubular casing provided with openings in the middle parts of its upper and lower sides and in its circumferential side, a transverse partition plate which divides the inside of the casing into upper and lower parts and a group of vertical heat pipes arranged to pierce through the peripheral portion of the partition plate in an annular plan configuration as a whole.

Abstract: A heat exchange system is provided which transfers the heat from a fluid discharged from a device that utilizes a heated fluid, to fresh fluid in order to increase the temperature of the fresh fluid prior to feeding it into a heating tank. Thus, less energy is required to heat the fluid in the heating tank prior to its introduction into the device which utilizes heated fluid. After the heat has been exchanged, the discharged fluid is then expelled from the system. A fluid trap controls the fluid level in the heat exchanger to assure maximum heat transfer capability. An antisiphon valve is provided in the fresh fluid input of the heat exchange coil in order to prevent discharged fluid from contaminating the fresh fluid source in the event of a rupture in the heat exchance coil.

Abstract: A heat exchange system in which sensible and/or latent heat is exchanged between a stream of incoming air into an enclosure and a stream of air leaving the enclosure, comprising a heat exchanger for the incoming air and a heat exchanger for the leaving air, each of said exchangers comprising a group of passages through which the incoming air stream and the leaving air stream, respectively, flow in heat exchange relationship with a liquid passing through a separate group of passages. The liquid is circulated in a closed circuit between the two exchangers in a duct leading from the heat exchanger for the incoming air to the heat exchanger for the leaving air, and, upon heat exchange with the leaving air, recirculated in a separate duct to the heat exchanger for the incoming air.

Abstract: A system for recovering the waste heat normally exhausted into the atmosphere by chemical or other processing plants. The invented system comprises a substantially self-contained apparatus for receiving hot exhaust gases and extracting the waste heat therefrom for some beneficial use, such as pre-heating inlet air in an inlet plenum. The system may include temperature and pressure controls which enhance the safety and efficiency of the system's operation, and further may include flow controls in a multiple burner installation so that the desired fuel air ratios and heat distribution may be achieved. By building the present invention as a substantially self-contained and self-supporting assembly, on site installation time and the required alteration of pre-existing on site equipment may be minimized, thereby affecting substantial economic savings by minimizing the resulting down time of the processing plant.

Abstract: A waste heat recovery device particularly usable for heating the air traveling through a cold air return duct to a hot air gas heating furnace which includes an exhaust box securable to the wall of the furnace and adapted to receive exhaust gases therein to gather heat in the plenum chamber defined by the exhaust box, the exhaust box also including an exhaust gas outlet to expel gases to the existing heater stack or flue for venting, the plenum chamber including an exhaust coil being in fluid flow communication through a conduit to a return coil which is located within the cold air return, the conduit means being partially filled with a thermal transfer fluid such as water which will boil within the conduit in the exhaust coil means and will condense within the conduit in the return coil means and as such will effect rapid thermal transfer from the heated exhaust waste to the incoming cold air traveling through the cold air return and thereby achieve waste heat recovery.

Abstract: A waste heat recovery system and method for recovering heat from exhaust gases flowing through an exhaust stack or flue from a source of heat. The recovery system includes a heat exchanger located within a bypass assembly that includes a pair of conduits connected to the exhaust stack, and a blower for producing a flow of exhaust gases from the exhaust stack through one of the conduits and the heat exchanger and then back to the exhaust stack through the other of the conduits. The method of the present invention includes the moving of at least a portion of the exhaust gases in the exhaust stack through the bypass assembly and returning such portion back to the exhaust stack.

Abstract: A domestic sewage system discharges hot sewage from several sources in a building such as a home to a sewer. The home is here provided with a fan in the sewer vent to draw air from an air inlet in the sewer, through the sewer where the air becomes heated, and then through a heat exchanger where heat is removed from the air such as for room or water heating, and then out through the sewer vent.

Abstract: A building such as a barn with a heat exchanging ventilating system including an exhaust duct with a fan drawing spent air from the center of the building and a pair of intake ducts respectively located above and below said exhaust duct, there being conductive heat transfer walls common with the exhaust duct and respectively with the air intake ducts, the air intake ducts also having inlets for outside fresh air, and the outlet ends of the intake ducts extending horizontally to direct air to the outside walls in the building for circulating the fresh air to the outside walls.

Abstract: A hydro gas plant with utilization of the residual coke, comprising a gasifier into which raw coal is introduced for hydro gasification that results in the production of methane; a furnace for cracking the methane into hydrogen and carbon monoxide; and means for utilizing the combustion heat of the residual coke obtained during the operation of the gasifier, or a low-BTU gas produced from the coke, in at least the cracking furnace but optionally also in a steam generator. The use of exhaust gases from the cracking furnace is also suggested, namely in a preheater through which hydrogen is fed to the gasifier.

Abstract: A heat pipe recuperator for recovering heat from flue gas stacks is disclosed. The recuperator consists of a toroidal shell forming a fluid heating chamber having inlet and outlet fluid circulating ports. A plurality of heat pipes are mounted within the chamber and are attached to the inner wall of the shell such that the condensor sides of the pipe reside within the shell and the evaporator sides extend outside the shell into the center of the toroid. The recuperator is positioned in a flue gas stack wherein the hot flue gas stream contacts the heat pipes which transfer heat into the fluid heating chamber. Fluid, gas or liquid, is passed through the chamber resulting in a rise in temperature of the fluid.

Abstract: There is provided a heat exchanger system for transfer of heat in the warm exhaust air from a mine to the cold input air flow to the mine. In the system there is provided a heat supply means, which supplies heat, recovered from the exhaust air, to the input air heat exchanger when an exhaust air heat exchanger is disconnected for defrosting.

Abstract: A heat transfer device for transferring excessive waste heat from the upper portion of a fireplace to the room comprising a high temperature heat exchanger positioned above the fire grate between the fire and the flue of the fireplace. A mass transfer tube communicates between the heat exchanger and the low temperature heat exchanger positioned above the lintel on the fireplace. A heat transfer fluid is secured within the hollow high temperature heat exchanger such as trichloromonofluoromethane such that as the fluid boils, the heat of the fire the liquid turns to a gas and moves through the mass transfer tube to low temperature exchanger. The fluid cools and gives up its heat to the low temperature exchanger which in turn gives up the heat to ambient air. As the fluid cools, it becomes a liquid again and flows back down the transfer tube from which it came to the high temperature exchanger.

Abstract: A system for recovering the waste heat normally exhausted into the atmosphere by chemical or other processing plants. The invented system comprises a substantially self-contained apparatus for receiving hot exhaust gases and extracting the waste heat therefrom for some beneficial use, such as pre-heating inlet air in an inlet plenum. The system may include temperature and pressure controls which enhance the safety and efficiency of the system's operation, and further may include flow controls in a multiple burner installation so that the desired fuel air ratios and heat distribution may be achieved. By building the present invention as a substantially self-contained and self-supporting assembly, on site installation time and the required alteration of pre-existing on site equipment may be minimized, thereby affecting substantial economic savings by minimizing the resulting down time of the processing plant.

Abstract: A method for the thermodynamic assisted compression of gases wherein a gas is alternately compressed and expanded with addition of heat regeneratively. The basic method is applicable to a variety of uses such as gas compression, turbines and in heat temperature boosters. Working fluids may be either gases or vapors. Heat may also be removed during compression steps and added during expansion steps. Process can be used with both steady flow and non-flow apparatus.

Abstract: A paint spray booth which includes a system for supplying air thereto under controlled conditions, with a heat pump operated to produce cooling or heating adjustments to incoming air as required under summer or winter operating conditions. Heat is transferred into or out of filtered air exhausted from the booth into the evaporator or out of the condenser by various heat exchanger arrangements to improve the operating efficiency of the heat pump during heating or cooling, respectively. Dehumidification is achieved by cooling the incoming air to an appropriate dew point temperature and then reheating to achieve the proper supply temperature, which process is improved in efficiency by either an air-to-air heat exchanger which utilizes incoming air to reheat the air, or alternatively, by a pair of secondary air-to-liquid heat exchangers positioned on either side of the main heat exchanger to transfer heat from the incoming air to the dehumidified air.

Abstract: A heat recovery device for recovering waste heat from a hot gas that carries solid and precipitable contaminants of the type given off from the grill area of a fast food restaurant in which a heat exchanger is provided through which these gases are directed for heat exchange with a gas to be heated such as ambient air. The heated air may then be supplied to the interior of the restaurant or to ambient. The two gases are directed through sets of spaced passages in the heat exchanger in heat exchange relationship with each other. A filter is used ahead of the heat exchanger for filtering the hot gas. This filter is easily removed for cleaning. A liquid receiving container may be periodically used to replace the filter. This receives a liquid such as a hot detergent solution that may be used to clean the contaminated passages of the heat exchanger.

Abstract: A heat reclaim system for reclaiming waste heat from a material processing line by bleeding a portion of the heated air from one or more points on the material heat processing line and directing such heated air through an economizer containing a bank of serpentine coils. Water is pumped through the economizer coils to extract heat from the air, and the heated water leaving the economizer is piped to another heat exchanger where the reclaimed heat is extracted from the water for use in other processes. More than one economizer may be provided in each heat reclaim system for receiving bleed-off air from different points on the material heat processing line, with the economizers connected in series to obtain the highest temperature difference between the air and water.

Abstract: A method for recovering sensible heat from a thermally decomposed high temperature hydrocarbon gas product in the form of high pressure steam of from 40 to 100 kg/cm.sup.2 has been discovered. This method comprises pre-cooling at first the thermally decomposed gas product of high temperature by mixing said gas product with sprayed low temperature hydrocarbon oil as a quenching oil to a temperature of about 300.degree. to 400.degree. C.; and then passing the resulting mixture through the tubes of a shell-and-tube type heat exchanger so as to transfer the heat of said mixture into a high pressure water flowing through the space of the shell side thereof to recover a high pressure steam, followed by separating the condensed hydrocarbon oil from the mixture to reuse said oil by recirculation.

Abstract: A selected number of heat pipes, located in the front rows of a plurality of otherwise operable heat pipes which are disposed between intake and exhaust ducts, have liquid-trap sections extending into a switching section. During normal operation, reservoirs in the switching section are dry and the plurality of heat pipes operate in a conventional manner. However, if some of the heat pipes in the exhaust dust become frosted over or otherwise too greatly cooled due to excessive cold in the intake duct, thermostatically or command-controlled valves or louvres cause the fluid stream in the exhaust duct to warm up or defrost the excessively cooled heat pipes therein. Prevention of excessive cooling is used to avoid frost build-up in air conditioning equipment, or solidification of solids and condensation of corrosive liquids.

Abstract: The invention comprises a method and an exhaust hood for the removal of heated, fouled air from a defined work area in a room having air tempering equipment, and having a source of fouled air located in the defined work area. The hood comprises an enclosure having a lower opening, the enclosure being positioned above the source of heated, fouled air, and means for supplying make-up air to the hood at a first determined rate. The make-up air is directed downwardly toward the fouled air source at a predetermined angle, thereby causing the make-up air to mix with the convectively rising heated, fouled air. The mixture of make-up air and fouled air is then exhausted at a second predetermined rate, thereby establishing an air stream from the make-up air source to the exhaust area. Contaminants are removed from the air to be exhausted and the make-up air is pre-heated with heat from the exhaust air.