Heat exchange system for recycling waste heat

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 and below the level of the heat discharge coil. The heat transferred to the refrigerant at the heat recovery coil is utilized as the sole means for freely cycling the refrigerant through the system heat pump fashion, with a liquid phase portion of the refrigerant being continuously recirculated between the receiver and the heat recovery coil, and heat charged vaporized refrigerant being supplied from the receiver to the heat discharge coil and returned in heat depleted liquid phase form to the receiver.

This application discloses improvements in the heat exchange system 
disclosed in Anthony A. Guiffre U.S. Pat. No. 4,216,903 granted Aug. 12, 
1980. 
This invention relates to providing for recycling some of the waste heat, 
such as that passing out of a building stack or flue, to make use of such 
heat, such as, for instance, for the purpose of heating incoming air or 
tempering stored water of the building water system, and more 
particularly, to a refrigeration arrangement of the heat generated 
refrigerant flow type which achieves that end. 
The present high cost of energy sources to produce heat have made it 
important to minimize wasting heat in the broad sense. More specifically, 
facilities that require more or less continuous supply of heat to perform 
their functions are now requiring, from a practical standpoint, 
incorporation of ways and means to harness heat that might otherwise be 
discharged into the atmosphere or sewer system along with the waste 
materials involved, to perform useful heating functions. 
For instance, buildings housing restaurant facilities and the like 
customarily are equipped to provide for forced air ventilation of the 
cooking facilities through a stack or other suitable discharge duct, with 
fresh air being drawn into the building through suitable ducting for 
ventilating and air replacement purposes. In many instances, and 
especially in the short order field, the cooking facilities, such as 
griddles and the like, are in intensive use for long periods of time each 
working day. As is common knowledge, the discharge from the building stack 
or flue contains much waste heat which is therefore lost to the 
atmosphere. The operation of furnaces for building heating and/or general 
purpose use presents similar waste heat problems as furnace products of 
combustion are discharged through stacks or flues to the atmosphere. 
The same type of heat loss problem is obviously involved in connection with 
the discharging of the water charges of washing machines and the like into 
sewer drains after washing procedures have been completed. 
On the other hand, many commercial facilities require the bringing into the 
building of fresh air as part of the ventilating system involved, and when 
the fresh air is brought into the building when outside ambient 
temperatures are well below room temperature, heating of the incoming air 
is usually desirable. The cost of supplying the requisite heat for 
incoming air has become a very significant item of expense, especially in 
the case of buildings housing restaurant facilities and the like where 
forced air ventilation in northern climates is required. 
Commercial and residential facilities commonly have a hot water system 
built into same for supplying hot water for general purpose use, with the 
water system being supplied with water from municipal mains or the like; 
of course, this water must be heated to provide the desired hot water. Hot 
water heaters are commonly employed for this purpose with the requisite 
heat usually being supplied using natural gas fuel or electrical energy 
type heating systems that both involve considerable attendant expense that 
can be alleviated or reduced by preheating or tempering of main water 
before it is taken into the water heater. 
A principal object of the present invention is to provide for simple but 
effective means and methods for recycling some of the waste heat that 
would otherwise be lost by discharge of waste gases from flues or stacks, 
or waste liquids into sewer systems, and utilizing same for useful 
purposes, such as to heat incoming fresh air where outside ambient 
temperatures require this, or tempering stored water of a hot water 
system. 
Another principal object of this invention is to provide a closed circuit 
heat generated refrigerant flow refrigerant system for recycling waste 
heat, for such commonly needed purposes of heating incoming fresh air or 
tempering the stored water of the hot water system, in which the 
refrigeration system is free of pumps or compressors, and is arranged to 
provide for rapid recycling of the refrigerant to the system for maximized 
efficiency. 
A more general object of the invention is to provide a refrigerant type 
heat transfer system of the heat generated refrigerant flow type that is 
appliable to transfer heat from any heat source to a heat sink at a 
temperature that is lower than the heat source. 
A more specific object of the invention is to provide a system for 
continuous recycling of waste heat having thermostatically operated 
controls for switching the supply of the waste heat between different 
objectives, such as, for instance, providing for supply of the recycled 
heat to incoming fresh air where outside ambient temperatures are below 
predetermined level, and alternately supplying the recycled heat to a 
water tempering tank when the outside ambient temperature is above said 
predetermined level, or for merely temporarily discontinuing the supply of 
the waste heat for temperature control or other purposes. 
Other objects are to provide a waste heat recycling system that is of few 
and simple parts, that is economical to install and operate, and that is 
long lived and reliable in use. 
In accordance with an illustrated embodiment of the invention, which is 
disclosed for illustrative purposes as applied to a restaurant facility of 
the type indicated, a closed circuit heat generated refrigerant flow type 
refrigeration system is established in operative association with the 
building stack, the building fresh air intake duct, and the building hot 
water system storage tank whereby an evaporator in the form of a heat 
recovery coil is mounted in the stack and in heat exchanger relation with 
the waste heat bearing gases passing through the stack and condensers in 
the form of heat transfer coils are mounted in heat transfer relation to 
the incoming fresh air and the water of the storage tank. The heat 
transfer coils are disposed at levels above the horizontal level of the 
heat recovery coil. The refrigeration system includes a refrigerant 
receiver that provides a chamber located adjacent to the level of the heat 
recovery coil in which the vapor phase of the refrigerant is separated 
from its liquid phase to define a refrigerant liquid level in the chamber 
that is above the level of the heat recovery coil and below the level of 
the heat transfer coils. 
The refrigerant outflow conduiting communicates between the upper side of 
the receiver and the respective heat transfer coils for exposing heat 
charged refrigerant from the receiver to the respective heat transfer 
coils, and return conduiting communicating between the respective heat 
discharge coils and the lower side of the receiver is provided for 
returning under gravity heat depleted liquid refrigerant from the level of 
the respective heat transfer coils. 
An important feature of the present invention is that the refrigerant 
system receiver and the heat recovery coil are connected by recycle 
conduiting for supplying the heat depleted refrigerant liquid to the heat 
recovery coil and returning all of the refrigerant passing through the 
heat recovery coil to the receiver, including both liquid and gaseous 
phase refrigerant, to establish a liquid refrigerant recirculation between 
the heat recovery coil and the receiver that provides for improved heat 
transfer characteristics at the heat recovery coil and eliminates hot 
spots and superheating of the vapor within the heat recovery coil. 
The conduiting that communicates the refrigerant from the respective heat 
transfer coils for return to the receiver is formed adjacent the level of 
the receiver to define a liquid refrigerant trap of the gravity induced 
type, which, however, is free of any obstructions to free flow of the 
liquid refrigerant through the conduiting involved for return to the 
receiver. The trap is arranged so that gravity acting on the liquid 
refrigerant overcomes the pressure differential between the receiver and 
the heat transfer coils for liquid flow of the refrigerant back into the 
receiver. 
The system is fully charged with a halogenated hydro-carbon type 
refrigerant to establish the liquid level of the refrigerant within the 
receiver whereby the heat recovery coil is fully flooded with refrigerant. 
Operatively associated with the exemplary heat recycling system as 
described above are thermostatically operated control valves that are 
arranged for alternate isolation of the respective heat transfer coils 
from the heat recovery coil, in accordance with the predetermined ambient 
air temperature exteriorily of the building, whereby the heat recovered 
from the stack is supplied to the incoming fresh air when the exterior 
ambient temperature is below the selected level, and when the exterior 
ambient temperature is above the selected level, the recovered stacked 
heat is applied to water to be tempered. 
The heat supplied to the refrigerant system at the heat recovery coil is 
utilized in conjunction with gravity return of the heat depelted liquid 
refrigerant from the heat transfer coils, as the sole means to freely 
cycle the refrigerant through the system free of mechanical pumping action 
on the refrigerant. The application of heat to the heat recovery coil not 
only vaporizes liquid refrigerant in the heat recovery coil, but starts a 
recycling flow of the liquid refrigerant between the heat recovery coil 
and the receiver that has the effect of inducing a rapid refrigerant flow 
through the heat recovery coil which eliminates hot spot and vapor 
superheating problems and speeds up heat transfer characteristics. 
At the receiver, the lighter vaporized refrigerant rises above the level of 
the liquid refrigerant and due to the pressure build up of the vaporized 
refrigerant in the system, flows through the outflow conduiting to the 
locale of the respective heat transfer coils for communication therewith, 
as controlled by the control valves where present. The refrigerant 
liquifies on giving up its heat at the heat transfer coils and returns 
under gravity through the return conduiting, the liquid refrigerant trap, 
and to the lower side of the receiver. 
As long as stack heat is available for application to the heat recovery 
coil, the refrigerant system will remain in operation under the control of 
the indicated control valves, with the refrigerant continuously recycling 
through the system under the heat generated refrigerant outflow and 
gravity induced return employed in practicing the invention. 
Alternatively, the heat transfer systems employed may be simplified to 
eliminate the indicated control valves and supply the stack heat only for 
one purpose use, such as for heating the incoming fresh air, or for 
heating water to be tempered, or heating a basement area, or any general 
purpose use where heat is to be transferred from a heat source to a heat 
sink that is at a temperature lower than that of the source. 
Also, a modified theremostatically operated control valve arrangement may 
be employed to redirect the refrigerant flow in such a manner that the 
supply of liquid refrigerant to the heat recovery coil is cut off without 
having to shut down the sourse of heat. 
A special feature of the invention is that the heat transferred to the heat 
recovery coil and the heat transferred at the heat transfer coil are what 
motivate the cycling of the refrigerant through the system and provide a 
refrigeration system type heat transfer action between the heat recovery 
coil and the respective heat transfer coils involved that is free of 
mechanical pumping requirements. The liquid traps that are in the return 
conduiting of the system in addition to providing for overcoming of the 
pressure differential between the receiver and the heat transfer coils 
resist reverse flow of the refrigerant so that there is a smooth and 
continuous run-around type movement of the refrigerant through the coils, 
conduiting, and receiver, that are involved in the refrigeration system, 
with refrigerant return flow from the system condenser or condensers being 
under gravity. 
It is an important feature of the invention that, as temperature 
differentials between the heat source at the heat recovery coil forming 
the system evaporator (which heat source is preferably of constant 
temperature for any given application), and the heat discharge point or 
points of the system (the condenser or condensers forming the heat sink) 
are increased, recycling of the refrigerant through the refrigeration 
system accelerates without the need for any mechanical pumping action on 
the refrigerant being required. This accelerating effect reaches a maximum 
that will depend on the refrigerant employed in the system, the heat input 
at the heat recovery coil, the size of the piping employed to provide the 
conduiting required, and the refrigerant employed in the system. 
Other objects, uses, and advantages will be obvious or become apparent from 
a consideration of the following detailed description and the application 
drawings in which like reference numerals indicate like parts throughout 
the several views.

However, it is to be distinctly understood that the specific drawing 
illustrations provided are supplied to comply with the requirements of the 
Patent Laws, and that the invention is susceptible of other embodiments 
that will be obvious to those skilled in the art, and which are intended 
to be covered by the appended claims. 
The showing of FIG. 1 is provided to diagrammatically illustrate a typical 
practical application of the principles of this invention in which 
reference numeral 10 generally indicates a building housing a restaurant 
type cooking facility generally indicated by reference numeral 12 and 
shown in block diagram form, which is intended to represent a griddle or 
other type of open cooking that in use is intended to be in continuous 
operation for a long period of time during the work day. Typically, the 
building 10 is equipped with a stack or flue 14 provided with a suitable 
blower apparatus 16 for impelling air outwardly of the stack and through 
stack discharge opening 18 suitably formed in the roof of the building 10, 
whereby air ambient to the cooking facility 12 is drawn into the stack 14 
through suitable stack intake opening 19 and discharged to the atmosphere 
through stack opening 18. 
The building 10 is also typically equipped with a fresh air intake duct 21 
having a suitable blower apparatus 23 mounted therein for impelling fresh 
incoming air into the building 10 for the usual ventilating purposes. 
In accordance with the invention, the building 10 is equipped with the 
closed circuit heat generated refrigerant flow type heat exchange system 
comprising the invention, the basic arrangement of which is 
diagrammatically illustrated in FIG. 2 and indicated by reference numeral 
20. The system 20 generally comprises evaporator 22 (forming the system 
heat source) that may be in the form of one of the heat recovery or 
absorption coils illustrated in other figures of the drawings, suitably 
mounted in stack 14 and cooperatively related by incorporation in the 
system 20 to transfer, from the evaporator, heat to condenser 25 (forming 
the system heat sink) which may take the form of heat transfer coil 24 of 
FIGS. 1 and 3 suitably mounted in the air intake duct 21 in heat discharge 
relation thereto, or heat transfer coil 26 (arranged as indicated in FIG. 
4) suitably mounted in heat discharge relation to the water of water 
holding tank 28 (which is assumed to be the building water storage tank) 
suitably supported in the building 10. The water of tank 28, in accordance 
with the invention, for water tempering or preheating purposes, is 
connected to refrigerant receiving water tempering chamber 29 which the 
coil 26 is mounted, as more specifically illustrated in FIG. 4, by 
suitable inflow and outflow conduits 30 and 32 that are series connected 
to coil 26 for conducting the water flow therethrough to and from tank 28, 
the diagrammatic illustration of which is provided in FIG. 4. 
In the diagrammatic showing of FIG. 1, the conduiting of the heat exchange 
systems that may be employed in accordance with the invention is not shown 
to simplify the drawing, with the other figures of the drawings being 
provided to show the essentials of the system layouts involved. 
The coils 22, 24, 26 may be of any type suitable for use as evaporators and 
condensers for refrigeration system type heat exchange and heat transfer 
purposes. They thus may take the familiar form illustrated for coils 22 
and 24 in FIGS. 3-5 and thus comprise lengths of copper tubing shaped to 
have the sinuous rounded shaping indicated, that is usually associated 
with heat exchange coils. Coil 22 is shown in another familiar form in 
FIG. 4 comprising intake end manifold 40 and discharge or outflow end 
manifold 48 connected by spaced grid pipes 43. Therefore, the term "coil" 
as used in this disclosure and appended claims is intended to mean these 
well known types of heat exchangers and their equivalents that may be used 
for evaporator and condenser purposes. 
In accordance with the basic principles of the invention, as 
diagrammatically illustrated in FIG. 2, the evaporator takes the form of 
one of the heat exchange coils 22 serving as a heat recovery coil that may 
be mounted in heat transfer relation with the source of heat, as by being 
mounted as indicated in stack 14. The heat recovery coil serving as 
evaporator 22 should be mounted at a lower level in the building 10 below 
the horizontal levels of the heat transfer coils 24 and 26. Suitably 
mounted adjacent the level of the heat recovery coil 22 is receiver 50 
that in its preferred form is cylindrical in configuration and elongate 
longitudinally of its longitudinal axis, with the receiver being disposed 
so that its longitudinal axis is horizontally disposed, as indicated in 
FIG. 2. Receiver 50 is formed to define refrigerant receiving chamber 52 
that has its length dimension proportioned to exceed its height dimension 
by a proportion on the order of 4 to 1. Refrigerant outflow conduit 54 
communicates the receiver chamber 52, from the upper or top side 53 of the 
receiver, with the intake end 56 of the condenser 25, while return conduit 
58 connects the outlet end 60 of the condenser 25 with the receiver 
chamber 52 through the lower or bottom side 62 of the receiver through the 
liquid trap formed in conduit 58 where indicated at 64. 
Supply conduit 66 communicates the receiver chamber 52 through the lower 
side 62 thereof to the intake end 68 of the evaporator and the outlet or 
outflow end 70 of the evaporator communicates with the receiver chamber 52 
by recycle conduit 72 through the lower side 62 of the receiver. 
In practicing the invention, assuming that the basic component parts of the 
refrigeration system as illustrated in FIG. 2 are installed for practical 
operation, the refrigeration system 20 is fully charged with refrigerant 
that is preferably of the halogenated hydrocarbon type (of which the 
Freons are an example) by suitably evacuating the system as at the 
receiver, and through a suitable check valve 74, after which the 
refrigerant in its liquid phase is pumped into the system through check 
valve 76 to bring the liquid level of the liquid refrigerant within the 
system 20 up to and within receiver 50, as indicated at 78. This is done, 
of course, when the heat source is not operating. 
In this connection, it is important that the receiver 50, in being disposed 
adjacent the level of the evaporator 22, it should be so elevationally 
related to the evaporator 22 that the liquid level of the liquid 
refrigerant within the receiver chamber 52 be above the horizontal level 
of the outlet or outflow end 70 of the evaporator 22 in the dormant 
condition of the system; the receiver 50 should also be positioned 
relative to the condenser so that the liquid level 78 in the receiver 50 
is sufficiently below the outlet or outflow end 60 of the condenser 25 in 
the dormant condition of the system, such that liquid refrigerant will 
return under gravity by liquid flow through return conduiting against the 
pressure within receiver 50, as explained in detail hereinafter. 
After the system is charged with the refrigerant as indicated, the receiver 
50 is suitably sealed and the system is suitably vented to removed trapped 
air from the system. This may be done by employing the high point vent 
arrangement indicated at 80 in FIG. 2 in which the outflow conduiting 54 
is provided with a high point portion 82 equipped with a suitable vent 84 
controlled by suitable off-on valve 86, which valve 86 is closed to seal 
the system 20 after initial air venting. 
In operation, assuming that the evaporator 22 is exposed to the source of 
heat, and the condenser 25 is exposed to the fluid to be heated or other 
heat sink, the heat input at the evaporator 22 starts vaporization of the 
liquid refrigerant in the evaporator with the result that the refrigerant 
in the evaporator becomes lighter than the liquid refrigerant in the 
receiver and the evaporator supply conduit 66, so that a liquid 
refrigerant circulation system starts whereby refrigerant leaving the 
evaporator 22 through conduit 72 is in mixed liquid-gaseous form and 
enters the receiver 50, thereby inducing liquid refrigerant flow from the 
lower side 62 of the receiver through supply conduit 66 and back into the 
evaporator at its intake or inflow end 68. This recirculation of the 
refrigerant between the evaporator and the receiver continues during 
operation of the refrigerant system. 
The vaporized refrigerant entering the receiver rises to and through the 
liquid level 78 of the refrigerant in the receiver and builds up pressure 
in the receiver to the point that the heat charged vaporized refrigerant 
passes through outlet flow conduit 54 into the intake or inflow end 56 of 
the condenser 25, thence through the condenser where the refrigerant 
condenses to give off its heat and leaves the condenser in liquid form at 
the condenser outflow end 60 for return under gravity through conduit 58 
to receiver 50 for recycling through the system. 
The liquid refrigerant trap 64 through which the heat depleted refrigerant 
returns to the receiver comprises a bight portion 90 formed in the 
conduiting 58 that is of upright U configuration comprising upstanding leg 
portions 92 and 94 serially connected by connecting portion 96. The 
conduiting portions 92, 94 and 96 are fully opened throughout the length 
of same to provide for free flow therethrough of the liquid refrigerant 
under the head that exists on the liquid refrigerant in the return 
conduiting 58 by reason of the elevation of the condenser 25 above the 
receiver 50. However, the quantity of liquid refrigerant that is retained 
by the action of gravity within the trap 64 resists refrigerant reverse 
flow tendencies that may occur in the system during operation of same and 
insures that the refrigerant flow rates and efficiency desired for a 
particular installation are obtained. 
In accordance with the present invention, the horizontal level of the 
liquid trap 64 is adjacent the level of the receiver 50, with the 
connecting conduit portion 96 disposed below the lower or under side 62 of 
the receiver 50. The length of the trap connecting portion 96 is not 
critical and may be of substantial length; however, the upstanding leg 
portion 92 on the condenser side of the trap extends adequately above the 
top side 53 of the receiver 50 to fully resist refrigerant reverse flow 
tendencies in the direction of the condenser 25; thus, the trap leg 
portion 92 exceeds the length of the trap leg portion 94 on the receiver 
side of the trap. 
In the practice of the invention in the diagrammatically illustrated 
structural environmental background shown in FIG. 1, it is preferred that 
the temperature at the locale of the heat recovery coil 22 within the 
stack 14 be preferably in the range of from approximately 200 degrees F. 
to approximately 300 degrees F. It is to be understood that numerous other 
practical applications of the system are possible, however, using lower or 
higher temperature heat sources that may lie in the wider range of from 
approximately 100 degrees F. to approximately 600 degrees F. (as will be 
hereinafter referred to), though for most Freons, the recommended maximum 
continuous operating temperature for the refrigerant is 225 degrees F. 
(this in practice being subject to a number of variables, such as the 
materials from which the evaporator and condenser coil are made, the 
cleanliness of the system, and the specific refrigerant being used). 
It will be found in practice that the refrigerant of the system 20 cycles 
through the coils forming the evaporator 22 and condenser 25 in a 
run-around type relation, with the recycling accelerating in proportion to 
the differences in the temperature at the locales of the evaporator 22 and 
the condenser 25. This acceleration effect reaches a maximum that will 
depend upon the refrigerant employed in the system, the heat input to the 
system at the heat recovery coil 22, and the heat outflow from the system 
at the condenser 25, and the size of the conduiting employed. 
More specifically, on start up of the system, liquid refrigerant evaporates 
in the evaporator as heat is absorbed by it, and passes together with the 
liquid refrigerant recirculating flow through conduit 72 to receiver 50. 
The vaporized refrigerant rises to the top side of the receiver and passes 
through conduit 54 to condenser 25 where it condenses to give up its 
stored heat and returns in liquid phase form under gravity through the 
return conduit 58 and its trap 64 to receiver 50. As the refrigerant 
system goes into operation, a pressure differential builds up between the 
outflow end 60 of the condenser and the pressure within the receiver; this 
pressure differential and the speed of the refrigerant cycling through the 
system will increase, as the temperature at the locale of the evaporator 
22 rises relative to the temperature at the locale of the condenser 25, 
until a balance point, or maximum pressure difference level is reached, to 
provide the optimum or maximum speed of refrigeration cycling within the 
system 20 for a given installation. This balance point will depend upon 
the specific refrigerant employed, the amount of liquid level head between 
the level 78 of the refrigerant liquid in receiver 50 and the level of the 
liquid refrigerant at the condenser, the amount of heat input to the 
system at the evaporator, the amount of heat output of the system at the 
condenser, and the size of the piping employed to form the illustrated 
conduiting. Generally speaking, the refrigerant vapor flow action to the 
condenser is proportional to the heat recovery achieved. 
The refrigerant preferred for practicing the invention are the halogenated 
hydrocarbons, familiar commercial examples of which are the Freons, such 
as Freon 11, 12, 21, 22, 113, and 114; these Freons or combinations of 
same are non-toxic, non-corrosive, and non-flammable and are thus highly 
suitable for practice of the invention, with the specific refrigerant 
employed depending on the application. As indicated in the drawings, the 
system 20 is of the closed, non-mechanical pump, refrigeration type in 
which the flow of the refrigerant through the system is generated by the 
application of heat to the evaporator 22 and a gravity return from the 
condenser that operates with sufficient head to overcome the pressure in 
the receiver for continuous liquid refrigerant return to the receiver. Of 
course, the conduiting heat exchange coils comprising the evaporator and 
condenser, the conduits and chambers through which the refrigerant flow, 
and the various connections involved should be fluid tight throughout the 
system 20 in operation of the system to keep the refrigerant charge of 
constant amount and free of impurities. 
The recirculating liquid refrigerant flow that occurs between the 
evaporator 22 and the receiver 50 during operation of the system has the 
effect of effecting forced flow of the refrigerant through the evaporator 
and thereby achieves a continuous movement of the refrigerant through the 
evaporator at a rate faster than the refrigerant would normally move as a 
result of the movement rate being solely induced by evaporation at the 
evaporator such that the refrigerant would leave the evaporator fully 
vaporized. The liquid refrigerant flow through and from the evaporator 
carries with it the vaporized refrigerant, thereby eliminating the 
formation of undesirable hot spots and prevents undesirable superheating 
of the vaporized refrigerant, thereby resulting in speeded up heat 
transfer characteristics and uniform heat absorption at the evaporator. 
It is fundamental to this system that the level of the liquid refrigerant 
at the condenser be sufficiently above the level of the liquid level 78 in 
the receiver 52 such that the pressure in the receiver will be overcome by 
the "head" of the liquid refrigerant involved, for liquid refrigerant flow 
under gravity into the receiver. The liquid refrigerant head involved is 
the vertical distance between the liquid level 78 in the receiver and the 
corresponding liquid level of the refrigerant, represented by dimension 
"X" of FIG. 2, and this head must exceed that which would balance against 
the pressure in the receiver. Thus, the level of the liquid refrigerant on 
the condenser side of the trap 64 must be sufficiently above the receiver 
liquid level 78 so that the head X of the liquid involved will more than 
balance against the pressure in the receiver (which must be greater than 
the pressure in the evaporator to effect vapor flow to the evaporator, 
with the pressure differential involved ordinarily being somewhat less 
than one psi; thus, the head X must exceed that which would equal the 
pressure differential between pressures within the receiver and the 
condenser. 
The horizontal disposition of the receiver 50 relative to its longitudinal 
axis disposes the liquid level 78 of the refrigerant across the dimension 
of maximum area of the chamber 52. Since the level 78 is more or less 
aligned with the horizontal axis of receiver 50, and the receiver 50 is in 
cylindrical form, the area of the liquid level 78 roughly corresponds to 
the area of a horizontal plane intersecting the longitudinal center axis 
of the receiver 50, as delineated by the internal side and end wall 
surfacing of the receiver that defines the chamber 52. This maximized area 
of the liquid level 78 minimizes the vertical fluctuation of the level 78 
within receiver 50 and makes for increased stability of the head X. 
In the showing of FIG. 3, system 20A is basically the same as system 20, 
with the valving 76 and 74 omitted as well as the high point venting 
arrangement 80, for simplicity of illustration. The coil 22 is shown 
applied to stack 14. In the form of FIG. 3, the coil 22 is of the sinuous 
rounded shaping type incorporated in a suitable frame 100 that is suitably 
mounted in stack 14 in the path of the fluid flow through stack 14. 
The coil 24 representing the condenser 25 of FIG. 2 is also of the sinuous 
rounded shaping type and is suitably incorporated in suitable frame 112 
that is appropriately mounted within the duct 21 in the path of the fluid 
flow through duct 21. 
The remaining components of FIG. 3 bear reference numerals corresponding to 
the already described components of the basic system shown in FIG. 2. 
In practicing the invention as represented by the embodiment of FIG. 3, the 
instituting of heat flow out of the stack 14 by the operation of the 
cooking equipment 12 and the operation of blowers 16 and 23 effects the 
aforedescribed operation of the refrigeration system whereby the heat 
recovery coil 22 absorbs heat from the stack 14 and releases heat to the 
incoming air of duct 21 at heat discharge coil 24, as the refrigeration 
20A cycles. 
Another example of the utility of system 20A is its adaption to supply heat 
to the basement of a residence from the residence furnace stack or flue. 
In such an arrangement, coil 22 is mounted in the flue as suggested in 
FIG. 3, and the coil 24 is exposed to the ambient air of the basement, 
which is preferably blown against the coil 24 by a fan for maximizing the 
heat discharge at the condenser, comparable to the showing of the coil 24 
in FIG. 1. 
In the system 20B of FIG. 4, the refrigeration system involved supplies 
recovered stack heat to temper the water of chamber 29, and thus to coil 
26. The coil 26 is suitably mounted within the chamber 29 in a convenient 
manner for intimate heat transfer relation with the water supplied to 
chamber 29 from water storage tank 28 through the conduits 30 and 32 that 
are connected to the intake and discharge ends 120 and 122 of the coil 26. 
The refrigerant outflow conduit 54 has its discharge end suitably 
connected to the intake 56 of chamber 29 and the refrigerant return 
conduit 58 has its intake end suitably connected to outlet 60 of the 
chamber 29 so that the coil 26, which is mounted within the chamber 29, is 
fully blanketed and immersed in the refrigerant flow passing through the 
interior of chamber 29 between the conduits 54 and 58. The refrigerant 
within chamber 29 is thus in heat transfer relation to the coil 26 through 
which the water from tank 28 flows for being heated within the chamber 29 
for water tempering purposes. 
The chamber 29 may be in the form of a suitable refrigerant confining 
container or vessel 124 suitably mounted in the building 10 and having the 
coil 26 suitably supported in same for the indicated connection with the 
conduits 30 and 32. The container 124 is thus hollow for refrigerant fluid 
flow therethrough between the inlet 56 and the outlet 60 whereby the coil 
26 is thus immersed in fluid refrigerant that bears the recovered heat for 
transmittal through the tubing walls defining the coil 26 to the water 
flowing therethrough via the conduits 30 and 32. 
In the showing of FIG. 4, the water storage tank 28 is shown supplied with 
water through conduit 128, which leads from connection to the usual water 
mains. When system 20B is operating, suitable pump 134 operated by motor 
136 pumps the incoming water from pipe 128 through conduit 30, coil 26, 
and conduit 32 and thence to the storage tank 28. Conduit 138 leads to the 
hot water heater. 
In the system 20B, the heat recovery coil 22 is of the spaced grid pipe 
type already described and is suitably mounted in stack 14. The system 20B 
functions as described in connection with the showing of FIG. 2 to supply 
heat charged refrigerant to the chamber 29 which serves as the means for 
exposing the heat charged refrigerant to heat transfer coil 26 for 
tempering the water of storage tank 28. Manifestly, the water tempering 
temperature achieved for the water of storage tank 28 by the operation of 
system 20B reduces the heating requirements for hot water heating of the 
water passed to the building hot water heater through conduit 138. 
In the refrigeration system 20C of FIGS. 5 and 6, the systems 20A and 20B 
are combined for alternate operation under the control of the 
thermostatically operated control arrangement 140 of FIG. 6. For this 
purpose, the refrigerant outflow conduit 54 has a branch 142 that is 
connected to the intake or inflow end of the coil 24, and a branch 144 
that is connected to the chamber 29 at its refrigerant inlet 56. The 
outlet flow conduit branches 142 and 144 are suitably coupled together by 
suitable joint 146. 
Return conduit 58 has connected to same a return conduit 58A, as at 
connection fitting 150, with the inflow end of the conduit 58A being 
connected to the outflow end 60 of the coil 24. 
The return conduits 58 and 58A are each formed with a liquid trap, 
indicated at 64A and 64B, that has the same component parts as trap 64 of 
system 20, as indicated by corresponding reference numerals. In the form 
illustrated in FIG. 5, the trap 64A of conduit 58 is spaced from the 
receiver 50 and connected thereto by horizontal line portion 160 to which 
the leg portion 94 of trap 64B is connected by fitting 150, whereby the 
heat depleted liquid refrigerant returns to receiver 50 from the 
respective coils 24 and 26 when the latter are in operation. 
In accordance with the embodiment of FIG. 5, it is intended that the heat 
recovered at coil 22, from the waste heat leaving stack 14, be released at 
either coil 24 or 26, depending on temperature conditions of the ambient 
air external to the building 10. For this arrangement, the 
thermostatically operated control arrangement 140 of FIG. 6 (or its 
equivalent) is employed, which is largely block diagram illustrated, and 
for purposes of illustration is shown to comprise a solenoid operated 
off-on valve 182 incorporated in the conduit branch 142, and a similar 
solenoid operated off-on valve 184 incorporated in conduit branch 144; the 
valves 182 and 184 are electrically operated from thermostatically 
operated control box 186 that is electrically and thermostatically 
arranged so that when the temperature of the ambient air externally of the 
building 10 is above a predetermined level, such as 60 degrees F., the 
valve 182 closes the discharge coil 24 from communication with the heat 
recovery coil 22, while the valve 184 opens and maintains the chamber 29 
(in which is mounted heat discharge coil 26) in open communication with 
the heat recovery coil 22. When the temperature of the ambient air 
externally of the building 10 is below such selected level, the positions 
of the valves 182 and 184 are reversed by the operation of box 186. 
The control box 86 may be of any suitable type that includes suitable means 
for sensing or being responsive to the temperature of the ambient air 
externally of the building 10, and that includes suitable means for 
alternately connecting the valves 182 and 184 (in response to said sensing 
means) to the suitable source of electrical energy that is to be made 
available for this purpose through connection thereto by suitable lead 
lines 190 and 192. 
FIG. 6 shows the condition where the ambient temperature externally of the 
building is above the predetermined temperature level, whereby the control 
device arrangement 140 connects the chamber 29 to heat recovery coil 22 to 
expose the refrigerant flow to coil 26 for purposes of tempering the water 
of tank 28. When the ambient temperature level referred to drops below the 
predetermined level, the positions of the valves 182 and 184 reverse to 
disconnect the chamber 29 from coil 22 and connect the coil 24 to the coil 
22 for refrigerant fluid flow thereto for application of the recovered 
heat to the fresh air being taken into the building through conduit 21. 
The valves 182 and 184 each comprise, in the simplified form shown, a 
suitable valve body 200 defining valve chamber or bore 202 that 
reciprocably receives valve stem 204 formed with aperture 206 that is to 
be disposed in the position of valve 184 to permit communication between 
the upstream and downstream portions of the respective conduit branches 
142 and 144, and that is to be disposed in the position of the valve 182 
to block communication between the upstream and downstream segments of 
such conduit branches. For this purpose, the valve stems 204 are shown 
operably associated with suitable solenoid coils 207 and arranged in the 
manner indicated for energization of the coils 207 to move the respective 
valve stems 204 to the flow blocking positions indicated against the 
action of biasing springs 208. 
The biasing springs 108 serve the function of biasing the respective valve 
stems 204, when the respective coils 207 are deenergized, whereby at the 
apertures 206 of the respective stems 204 are aligned with the respective 
conduit segments 142 and 144 for permitting fluid flow therethrough. 
In practice, the control device 180 and its valves 182 and 184 may take the 
form of any conventional equipment that will provide the functions 
indicated. 
In operation, assuming that the ambient temperature externally of the 
building is below the selected level, on start up of the system, by 
instituting heat flow out of the stack 14, the heat discharge coil 24 is 
connected to the heat recovery coil 22 while the chamber 29 is 
disconnected therefrom by the operation of the control device 180 (thus 
isolating coil 26 from coil 22). The coils 22 and 24 and their associated 
parts function in the manner described with reference to system 20A of 
FIG. 3. For normal operation, the heat source for coil 22, represented by 
stack 14 in the illustrated embodiments, should be substantially constant 
for uniform operation of the heat pump type refrigeration system involved. 
The temperature in the locale of the heat recovery coil within the stack 
14 is preferably in the range of from approximately 300 degrees F. to 
approximately 600 degrees F. for the particular type of installation 
illustrated. In any event, the heat source represented by the stack 14 
should provide a temperature level in the locale of the coil 22, relative 
to the temperature levels to be expected at the locale of the coil 24, 
such that the maximum refrigerant cycling effect contemplated by this 
invention will be achieved. When this is observed, up to 80 percent of the 
input heat at coil 22, in terms of BTU's per unit of time, can be 
recovered from waste stack heat, depending on the heat draw up available 
to the system. 
As indicated, when the ambient air temperature external to the building 10 
rises to exceed the indicated predetermined level, the positioning of the 
valves 182 and 184 reverse to disconnect the coil 24 from coil 22 and 
connect the chamber 29 thereto. The system 20C then operates in the manner 
described with reference to FIG. 4 to supply heat to the water from the 
storage tank 28 passing through the coil 26, so long as the temperature of 
the ambient air externally of the building 10 remains at a level above the 
indicated predetermined level. 
The system 20D of FIG. 7 is essentially the same as system 20B, with the 
coil 22 that serves as the evaporator 22 of the basic arrangement shown in 
FIG. 1 being suitably mounted in a water collection tank 220 which is 
supplied with water containing waste heat from any source, such as an 
automatic dish washing machine or clothes washing machine, indicated in 
block diagram form at 222, through suitable conduit 224, under the pumping 
action of the automatic equipment represented at 222. Suitable outlet 
conduit 226 provides for removal of the waste water from the tank 220 to a 
suitable point of disclosure, such as a floor drain or the like leading to 
a sewer. 
The receiver 50 of system 20D is operably connected to chamber 29 in the 
manner indicated in FIGS. 4 and 7 for supplying heat to water being passed 
through chamber 29 from a storage tank 28. 
When the washing machine 222 discharges its waste water into tank 220, it 
displaces the water ahead of it out of the tank through outlet conduit 
226. The fresh supply of waste water in the tank 220 supplies the waste 
heat to be absorbed at the coil 22 for heating the water passing through 
the chamber 29 in the manner described with reference to FIG. 4. The 
system 20D functions when there is sufficient heat in the water within the 
tank 220 to vaporize the refrigerant in coil 22. When the temperature of 
the water in tank 220 drops below that level, the system 20D automatically 
shuts down, and automatically reactivates when a fresh supply of heated 
water is passed into the tank 220. The operation of the motor 136 of pump 
134 (see FIG. 4) may be controlled to be in suitable timed relation to the 
operation of washer 222. 
The system 20E of FIGS. 8 and 9 is a modified version of the basic system 
20, with like parts being indicated by like reference numerals. In 
addition, the evaporator 22 and the condenser 25 are represented in 
container form, appropriately labeled, to indicate parts that are occupied 
by a liquid refrigerant in the alternate conditions of operation of the 
system. The refrigerant conduits involved are also diagrammed to indicate 
liquid refrigerant phase content, to distinguish this from gaseous phase 
content. 
The system 20E in addition to the outflow conduiting 54, the return 
conduiting 58, and its liquid trap 64, supply conduit 66, and recycle 
conduit 72, includes a bypass conduit 240 extending from the upper side 53 
of the receiver to the condenser 25, and that is interrupted by the 
suitable three way valve 242 that is diagrammatically illustrated as 
including a rotor 244 being formed with a right angled conduit passage 246 
therethrough having arm portions 248 and 250. The valve rotor 244 is 
journalled in leak free relation in suitable housing 245. 
The return conduiting 58 is formed with a second liquid trap 64A that is 
generally similar to trap 64, as indicated by corresponding reference 
numerals, and that is connected to horizontal conduit portion 252 that is 
in turn connected to a vapor vent conduit 254 which extends to 
communication with the valve 242 in the manner indicated in FIGS. 8 and 9. 
Valve housing 245 is suitably ported for the indicated alignment of the 
rotor conduit passage with conduits 240 and 254. 
The general arrangement of the system 20E is to provide for a shut down of 
the heat pumping function of the refrigeration system when the temperature 
of the refrigerant leaving the evaporator reaches a predetermined low 
level. For this purpose, valve 242 is controlled thermostatically in any 
suitable manner to position the valve 242 as shown in FIG. 8 when the 
temperature level of the refrigerant leaving evaporator 22 is above the 
indicated temperature level, and to switch the valve 242 to the position 
of FIG. 9 when the indicated temperature drops below the indicated 
temperature level. 
Thus, in the normal functioning of the refrigeration system 20E, the 
upstream segment 260 of bypass conduit 240 is disconnected from its 
downstream segment 262, with the passage 246 of the valve rotor member 244 
connecting the conduit 254 with the bypass conduit downstream segment 262 
whereby vaporized refrigerant in the return conduit 58 may vent back to 
the condenser. 
However, when the indicated temperature level of the refrigerant leaving 
the evaporator 22 drops below the indicated predetermined temperature 
level, the position of the valve 242 changes to the position of FIG. 9, 
which connects the upstream segment 260 of the bypass conduit 240 to the 
vent line 254 via the passage 246 of the valve rotor 244. The downstream 
segment 262 of the bypass conduit 240 is thus cut off from the receiver 
50. In this condition of the system 20E, the vaporized refrigerant from 
receiver 50 is supplied directly into return conduit 58 under pressure, 
thus interrupting the liquid refrigerant return flow from the condenser 
and resulting in the holding of the liquid refrigerant in the condenser in 
which it builds up as the condenser continues to be supplied with 
vaporized refrigerant through outflow conduit 54. At the receiver, the 
level of the liquid refrigerant gradually drops until all the liquid 
refrigerant has disappeared from the receiver, and the evaporator, supply 
conduit 66, and recycle conduit 72, are filled with the liquid 
refrigerant, as well as the lower portion of the liquid trap 64, as 
indicated in FIG. 9. 
In this condition of the system 20E as represented by FIG. 9, the source of 
heat applied to the evaporator may continue but there will be no heat 
transfer function, as the condition of system 20E as shown in FIG. 9 will 
remain until the temperature level of the refrigerant in recycle conduit 
72 rises above the indicated temperature level, at which point the 
position of the valve 242 reverses to the position of FIG. 8 for 
recommencing of the heat transfer function of the system 20E. 
A specific application of the system 20E is for an application where the 
evaporator 22 is to be exposed to, for instance, a source of heat 
involving moist air at 100 degrees F., and the condenser is exposed to a 
low temperature, such as 0 degrees F. or below. Under these conditions, 
the temperature of the liquid refrigerant entering the evaporator 22 may 
very well be below water freezing temperatures, which can result in the 
moist air at the evaporator depositing on the evaporator coils in the form 
of frost or ice that would impede the heat transfer action. Under these 
conditions, the valve 242 and associated parts function in the nature of a 
defrost control that maintains the coils of the evaporator 22 free of 
icing by providing the necessary off-on control through the suitable 
thermostatically operated arrangement effecting the changing of the valve 
242 in the manner indicated. Operation of valve 242 may be effected by a 
suitable thermostatically controlled switching arranged suitably thermally 
associated with conduit 72, as will be apparent to those skilled in the 
art. Of course, valve 242 may be controlled for operation by temperature 
conditions at other sites, such as the temperature ambient to the 
condenser, depending on the application. 
It will therefore be seen that the invention provides a refrigeration 
system type heat exchange system for recycling waste heat, such as stack 
heat, to recover much of the waste heat and apply it in an efficient 
manner to fluid needing heat, such as water held in storage for supply to 
a hot water heater or the heating of incoming cold air, or heating 
basements, etc. The basic refrigerant system involved is free of any 
mechanical pumping or compressor requirements, with the refrigerant flow 
being induced by the heat at the heat source associated with the 
evaporator, and the action of gravity on the liquid refrigerant being 
relied on to return the refrigerant to the evaporator. 
The illustrated applications of the basic system are to be considered as 
indicating only a few of the practical applications of the basic system. 
From the standpoint of fundamentals, the same basic system will operate to 
transfer heat from any source that will accommodate an evaporator 28 and 
transfer the heat to any form of heat sink that will accommodate a 
condenser 25. Normally, for best results the heat source should be at a 
suitable constant temperature, which may be at any workable level 
considering the nature of the equipment involved, the refrigerant employed 
and its maximum recommended continuous operating temperatures, and the 
application. For instance, the heat source in practical application may 
vary from well below room temperature to about 600 degrees F., the basic 
requirement being that the heat source temperature be higher than the heat 
sink temperature, but not so high as to destroy or damage the evaporator. 
However, the heat source for some applications will be intermittent, as 
illustrated by the embodiment of FIG. 7. 
A basic characteristic of the system of this invention is that if the heat 
source temperature should drop below that at the heat sink, the heat 
transfer involved ceases and does not reverse. The basic system is also, 
in operation, the opposite of heat pump systems which require the energy 
input of a compressor to function. 
The basic system involved by its nature will operate continuously so long 
as the refrigerant conduiting involved remains open to the flow of 
refrigerant and the source of heat is maintained at a sufficient level to 
evaporate the refrigerant in the evaporator. However, the system is 
adapted for supplying heat to alternate sites, as indicated by the form of 
FIG. 5, and the form of FIGS. 8 and 9 permits a discontinuance of the heat 
pumping function of the system under the conditions indicated without 
having to shut down the source of heat acting on the evaporator. 
The arrangement of the system to provide the recycling of the refrigerant 
between the receiver and the evaporator makes a significant improvement in 
the heat transfer coefficient between the heating surfaces of the 
evaporator and the refrigerant due to the increased flow rates of the 
fluid involved as well as the turbulence occasioned by the mixed gaseous 
liquid refrigerant flow in the evaporator. 
The refrigerant system of the invention as installed is completely sealed 
and normally requires no addition of refrigerant or any provision for 
deareation. 
It will be apparent that in addition to the energy conservation 
applications that are illustrated, the basic system may be employed for 
pollution control purposes, as well as for providing for condensation of 
undesirable vapors by removal of heat therefrom, or for controlling 
industrial processes by providing for controlled heat transfer to or from 
a processing locale. 
The foregoing description and the drawings are given merely to explain and 
illustrate the invention and the invention is not to be limited thereto, 
except insofar as the appended claims are so limited, since those skilled 
in the art who have the disclosure before them will be able to make 
modifications and variations therein without departing from the scope of 
the invention.