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BACKGROUND OF THE INVENTION
The present invention relates generally to a heating system for vehicles
having an internal combustion engine and more particularly to a heating
system comprising means for introducing heated air into the interior of
the vehicle.
Various types of heating systems for heating vehicle passenger compartments
are known, and in some cases such heating systems have the capability of
heating the vehicle interior independently of the operating condition of
the vehicle engine. That is, in many cases known heating systems are
capable of providing heat to the vehicle passenger compartment when the
engine is not running or is operating in a cold condition.
Such heating systems are generally considered as supplemental heat sources
inasmuch as they can be operated independently of or in addition to the
heating system of the vehicle engine. Generally, such known heaters
consist of a combustion chamber capable of burning therein a liquid fuel
for generating the necessary heat energy. These heaters usually include
means for introducing combustion air and ignition means for igniting the
fuel mixtures. There may also be provided a heat exchanger which surrounds
the combustion chamber of such a heating system in order to heat the air
which is supplied to the vehicle interior. Usually a heated air blower is
provided for blowing or drawing the heated air through conduit means for
delivery to the vehicle passenger compartment.
In some known heating systems, the heating units are operated by means of
the engine exhaust gases. In such systems, the heating process is
accomplished without utilization of a combustion chamber, but rather by
utilizing the vehicle exhaust pipe as a heat source in place of a
combustion chamber. A heat exchanger may be provided through which the air
to be heated flows in heat exchange relationshiop with a portion of the
engine exhaust pipe.
Although systems such as those previously mentioned may provide many
advantages, it will be seen that several disadvantages nevertheless arise.
In a system where a separate combustion source must be provided, there is
required provision of a liquid fuel, such as gasoline or diesel oil, in
addition to the fuel which must be provided for engine operation.
Furthermore, such a heating system must provide a separate exhaust system
of its own.
In heating systems operated by the exhaust gases of the vehicle,
disadvantages arise due to the requirement of expensive safety measures.
In such systems, there must be provided assurance that no exhaust gases
will reach the air heating system and, consequently, the interior of the
vehicle.
In heating technologies normally involving applications other than
vehicles, for example, home or living space heating applications, there is
known the principle of utilizing heat storage means wherein stored heat
may be conserved for utilization when desired. Such heating systems may
employ a heat storage medium such as transformer oil or ceramic compounds
which are heated preferably by means of electrical energy with the stored
heat being tapped as needed by means of a blower or other similar device.
It is known that liquids, such as transformer oil, are capable of storing
heat. Furthermore, in nuclear energy plants, for example, liquid sodium is
used as a heat transfer medium. It has been found that certain principles
and knowledge which normally find application in living space heating
technology and which involve use of heat storage devices, may be developed
to provide a heating system for a vehicle having an internal combustion
engine.
The present invention is directed toward adapting such principles to use in
vehicle heating applications. By means of the present invention, a heating
system for a vehicle having an internal combustion engine may be developed
which functions by utilization of a heat storage principle deriving heat
energy by utilizing the vehicle exhaust gases as a heat source. With the
present invention, certain advantages of known heating technologies may be
provide in vehicle heating applications while avoiding many of the
disadvantages of known vehicle heating systems.
SUMMARY OF THE INVENTION
Briefly, the present invention may be described as a system for heating the
interior of a vehicle having an internal combustion engine including
exhaust gas means, said system comprising heat reservoir means adapted to
store heat energy therein, heat absorption means for enabling absorption
of heat energy from said exhaust gas means of said engine by said heat
reservoir means, means for supplying air to the interior of said vehicle,
and means for controlling heat emission from the reservoir means, said
heat emission controlling means including means for selectively enabling
emission of heat energy stored in said reservoir means to air supplied to
the interior of said vehicle by said air supplying means.
The heat emission controlling means may comprise insulating means, such as
a vacuum chamber formed about the reservoir means, to produce a heat
insulating effect obstructing transfer of the heat energy stored in the
reservoir means. Heat transfer means for selectively overcoming the heat
insulating effects of the vacuum chamber while enabling selective transfer
of stored heat energy from the reservoir means may comprise a source of a
fluid heat transfer medium which may be selectively introduced into the
vacuum chamber to enable selective heating of the heating air by means of
the heat stored in the reservoir means.
The exhaust pipe of the engine may be utilized as a heat source and the
heat absorption means may comprise a heat exchange pipe involving liquid
sodium as the heat transfer medium. In view of the fact that sodium will
evaporate only when a sufficiently high temperature is reached, heat
transfer between the reservoir means and the exhaust gases may be limited
to a certain predetermined minimum exhaust gas temperature. Furthermore,
while utilizing a liquid transfer medium such as freon, the reservoir
means may be maintained within a vacuum chamber to prevent escape of the
stored heat therefrom, with selective introduction of the gaseous freon
into the vacuum chamber operating to heat the air introduced into the
vehicle passenger compartment when desired.
Thus, in accordance with the present invention there may be accomplished
utilization of a heat reservoir as a heat source for a vehicle heating
system which receives heat energy from the exhaust gases of the internal
combustion engine. It has been shown that a heating system of this type
can be provided with a relatively simple design while offering maximum
safety and sufficient heat capacity for warming the vehicle interior at
minimal operating cost. Transfer of heat from the exhaust gases to the
heat reservoir may be accomplished with minimal losses. In order to effect
transfer of the heat from the exhaust gases to the heat reservoir, a heat
pipe of known construction may be used which may be substantially fully
enclosed and insulated and then evacuated and filled with a certain
quantity of a liquid heat transfer medium. The inner surface of such a
device may be provided with a capillary structure and its heat condition
in operation may prove to be approximately 10,000 times better than that
of copper.
It has been found expedient to utilize heat absorption means between the
heat reservoir and the exhaust pipe which limit the occurrence of heat
transfer to exhaust gas temperatures of a predetermined minimum value. In
a preferred embodiment of the invention, this predetermined minimum is
selected to be about 650.degree. C. This may be accomplished, by way of
example, by utilizing a liquid sodium heat transfer medium in the heat
absorption means. As a result, when the exhaust gases are at a temperature
level above the predetermined minimum, heat absorption by the reservoir
means occurs. Heat stored in the reservoir means will be retained when
exhaust gas temperatures drop below the predetermined minimum thereby
enabling the stored heat to be later utilized as a source of heat energy
for the heater air.
In order to maintain optimum heat storage capacity in the reservoir means,
particularly in cases where longer storage periods are required, it has
been shown to be expedient, in accordance with a further preferred
embodiment of the invention, to arrange the heat reservoir so that it is
enclosed by a heat transfer jacket which establishes an evacuated chamber
between the jacket and the reservoir means. The evacuated chamber, which
provides a vacuum space surrounding the reservoir means, operates to
provide a heat insulating effect.
The heat reservoir means may comprise a tank or container filled with a
eutectic mixture of fluorides of alkali and earth alkali metals which
operate to absorb and store heat. The heat absorption means comprising the
liquid sodium transfer medium may be configured in the form of a heat pipe
extending between the exhaust gas conduit and the reservoir means with the
heat-emitting end of such heat pipe protruding into the reservoir means.
The filling of the heat pipe, in accordance with the present invention,
with a substance of high thermal capacity and of a high specific heat of
fusion will enable a particularly large amount of heat to be stored.
It is preferred to provide a heat reservoir having a thermal capacity such
that a sufficient amount of heat energy may be stored to heat a passenger
compartment or an internal combustion engine for a sufficient time at
least until the engine has sufficiently warmed to be, itself, a source of
heat. This heat storage capacity should be preferably in the order of
approximately 1000 kcl.
Inasmuch as the reservoir means is surrounded by a vacuum insulation
chamber, means must be provided to effect heat transfer to the heating air
when desired. It has been found to be particularly advantageous to provide
such heat transfer by means of an evaporation chamber which contains an
evaporable liquid adapted to be brought into the evacuated space of the
insulating vacuum chamber to establish a heat transfer path when it is
desired to tap the heat energy of the reservoir means. The evaporation
chamber may be provided with an electrical heating element which may heat
the liquid, which may preferably be freon, thereby causing evaporation of
the liquid medium whereby a heat-conducting vapor may be caused to flow
through the insulating vacuum chamber to enable heat from the reservoir
means to be transmitted to the heating air. By establishing a flow
connection between the insulating vacuum chamber arranged around the heat
reservoir tank and the evaporation chamber containing the evaporable heat
transmitting liquid medium it is possible to render the insulating vacuum
spacing selective heat-conducting. When heat conductivity is desired the
heat transfer medium may be caused to flow into the insulating vacuum
space by applying heat to evaporate the liquid. However, when no heat
transfer is desired, as when the heat stored in the reservoir means is to
be retained therein, the heat transfer medium may be removed from the
vacuum insulating space by condensation of the heat transfer fluid.
Inasmuch as the evaporable heat transfer fluid is heated by means of an
electrical heating element arranged adjacent the evaporation chamber
containing the heat transfer fluid, selective energization of this
electrical heating element may provide selective heat transfer from the
reservoir means. By selectively flowing the heat transfer fluid to within
the insulating vacuum chamber, heat may be transferred to the medium which
is to be heated, such as air or water, and the heat may thus be supplied
to the interior of the vehicle.
In this connection, it has been proven to be particularly advantageous for
the evaporation chamber to be filled, at least in part, with freon
inasmuch as freon is a particularly suitable evaporable fluid.
If the system of the present invention is to be operated as a heating unit
for the vehicle passenger compartment, an air blower may be provided to
conduct air past the heat reservoir means and through appropriate conduits
into the passenger compartment.
The various features of novelty which characterize the invention are
pointed out with particularity in the claims annexed to and forming a part
of this disclosure. For a better understanding of the invention, its
operating advantages and specific objects attained by its use, reference
should be had to the accompanying drawings and descriptive matter in which
there is illustrated and described a preferred embodiment of the invention
.
DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a schematic diagram illustrating the various components of a heat
storage heating system in accordance with the present invention; and
FIG. 2 is a wiring diagram pertaining to the system illustrated in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the illustration of FIG. 1, an internal combustion engine
1 is structured to include exhaust gas means comprising an exhaust
manifold 2 and an exhaust pipe 4 with an adapter 3 being provided therein.
The heating system of the present invention comprises as its major
component heat reservoir means 6 which are adaptable to have absorbed and
stored therein heat energy from the exhaust gas means of the engine 1.
Connected to extend between the adapter 3 of the exhaust gas means and the
heat reservoir 6 there is provided heat absorption means in the form of a
heat pipe 5 one end of which protrudes into the adapter 3 and the other
end of which is in heat conducting relationship with the heat reservoir 6.
Thus, heat of the exhaust gases passing through the manifold 2 and exhaust
pipe 3 of the engine exhaust gas means may be absorbed into the heat
reservoir 6 through the absorption means 5 extending to the adapter 3.
The heat reservoir 6 is formed with a heat transfer jacket 8 disposed
thereabout with the jacket 8 being welded tight on all sides. The jacket 8
is spaced from the reservoir 6 and defines therebetween a chamber 9. The
chamber 9 may be evacuated and the vacuum thus formed may operate to
produce a heat insulating effect about the reservoir 6. Thus, heat energy
delivered or absorbed into the reservoir 6 from the engine exhaust gases
will be retained and heat losses will be obstructed by means of the vacuum
formed in the chamber 9.
When the heating system of the invention is to be used to heat the interior
of the vehicle by delivery thereto of heated air, the heating system may
be formed as depicted in FIG. 1 to include an outer heater jacket 13 which
may operate as a conduit for air passing in the direction of the arrows
from left to right in FIG. 1. The heater air may be pumped by an air
blower 14 driven by a motor 16. Accordingly, it will be seen that
operation of the blower 14 will cause heater air to flow around the jacket
8 which surrounds the reservoir 6 and outwardly of the outer jacket 13 in
the direction of the arrow A whereupon it may be delivered, through
suitable conduit means (not shown) to the vehicle interior.
When it is desired to transfer heat from the reservoir 6 to the heater air
flowing about the outer jacket 8, a suitable heat transfer medium is
introduced into the chamber 9 thereby to overcome the insulating effects
of the vacuum formed therein.
For this purpose there is provided an evaporation chamber 11 having
contained therein a suitable heat transfer medium such as an evaporable
fluid. A heating element 12 may be operated to selectively evaporate the
heat transfer fluid contained in the evaporation chamber 11 thereby
causing the fluid to flow into the vacuum chamber 9 to thereby overcome
its insulating effects and to provide a heat transfer medium to enable the
heat energy stored in the reservoir means 6 to be transmitted to the
heater air.
The evaporation chamber 11 is connected in flow communication with the
vacuum chamber 9 by a suitable conduit 10. The electrical heating element
12 is provided with a pair of terminals 17 through which the element 12
may be selectively energized to selectively cause evaporation of the heat
transfer fluid within the evaporation chamber 11.
Accordingly, it will be seen that heat emission from the heat reservoir 6
may be selectively controlled by injecting and withdrawing the fluid heat
transfer medium to and from the vacuum chamber 9. When no heat transfer is
desired, and when it is desired to maintain the heat stored in the
reservoir 6 from being emitted therefrom, the vacuum chamber 9 may be
emptied of the fluid heat transfer medium by allowing the fluid to
condense and to flow into the evaporation chamber 11. However, when heat
emission from the reservoir 6 is desired, heating of the evaporation
chamber 11 and of the fluid heat transfer medium stored therein will cause
the fluid medium to evaporate and to flow into the vacuum chamber 9
thereby enabling heat emission from the reservoir 6 to the surrounding
heater air. Thus, selective operation of the heat emission control means
will enable selective emission of the heat from the reservoir 6.
The heat absorption means comprising the heat pipe 5 may be designed in a
known manner. The heat pipe 5 is evacuated and comprises an inner surface
which has a capillary structure and which is filled, for the above
described application, with a small amount of sodium which will evaporate
when heated thereby to effect a heat transfer operation virtually without
loss.
The heat reservoir 6 is preferably filled with a material having high
thermal capacity characteristics and a high specific heat of fusion. This
material, designated 7 in FIG. 1, may preferably comprise a eutectic
mixture of NaF.CaF2/MgF2.
The evaporation chamber 11 is, preferably, partially filled with freon
which may comprise the fluid heat transfer medium of the invention.
FIG. 2 depicts a simplified electrical wiring diagram for the heating
device of the invention. A switch 15 may be provided to activate the
blower motor 16 and the heating element 12 through its terminals 17. A
control light 18 may be provided to indicate energization of the system.
For temperature control, there may be connected in series with the line to
the blower motor 16, an NTC resistor 19 which is arranged within the hot
air flow path of the heating system to sense the temperature of air pumped
by the blower 14 thereby to control the speed of the blower motor 16 so
that the temperature of air at the outlet A of the heating system may be
maintained practically constant.
During the operation of the system of the present invention, when the
internal combustion engine 1 is running, there will flow in the exhaust
manifold 2 exhaust gases having a temperature of approximately 800.degree.
C. When a temperature of about 650.degree. C. is attained in the adapter 3
and hence at the heat-conducting end of the heat pipe 5, the evaporation
of the sodium in the heat pipe 5 will commence. The liquid vapor thus
produced will transfer the heat of the exhaust gases to the heat storage
metal 7 of the heat reservoir 6 with a conductivity level which is
approximately 10,000 times that of copper.
The heat thus stored in the heat storage metal 7 of the heat reservoir 6 is
protected from leakage and dissipation by the insulating vacuum produced
in the vacuum chamber 9. It is only when, due to operation of the
electrical heating element 12, the evaporating liquid in the chamber 11
fills the vacuum chamber 9 in gaseous form, thereby establishing a heat
flow path, that heat is transferred to the heat contact jacket 8 and thus
to the heating air pumped by the blower 14.
By selection of the proper heat transfer medium for the heat absorption
means 5, heat transfer between the exhaust gas means of the engine 1 and
the reservoir 6 may be restricted to temperature levels of the exhaust gas
above a predetermined minimum level. The utilization of sodium provides a
minimum heat transfer level of approximately 650.degree. C. due to the
fact that the sodium will not produce a heat transfer effect when the
exhaust gas temperature is below 650.degree. C. Thus, after the engine 1
has been operated for approximately ten minutes, and assuming that the
entire system has been shut down and is in a cold condition, the heat
reservoir will commence storing heat when the exhaust gas temperature
reaches approximately 650.degree. C. The heat reservoir 6 will store the
maximum amount of heat at approximately 750.degree. C-800.degree. C after
which it will effectively cease absorbing additional heat energy. If the
internal combustion engine is now shut down, some heat will flow back
through the heat pipe 5 into the adapter 3 from the reservoir 6. However,
this flow-back process will continue only until the heat pipe has reached
a temperature of approximately 650.degree. C., below which it no longer is
heat-conducting. After this minimum temperature has been reached, heat can
be transferred from the reservoir 6 only by heat conduction through the
thin sections of the heat pipe jacket itself. This heat conduction is
relatively small and thus the major portion of the heat energy stored in
the reservoir 6 will be maintained for approximately 10 to 20 hours. This
heat storage effect is enhanced by the insulating effects created by the
vacuum chamber 9 which, essentially, operates in a fashion similar to a
conventional Thermos bottle. Thus, when the heating system is turned on,
i.e. by energization of the blower 14 and of the heating element 12, the
stored heat may be drawn from the reservoir 6 and conducted to the heating
air flowing about the jacket 8 in order to provide heating of the vehicle
passenger compartment.
Of course, it will be understood that the present invention may be utilized
in applications other than as a system for heating air. For example, other
applications wherein a liquid medium is to be heated could conceivably be
devised within the knowledge of those skilled in the art.
While a specific embodiment of the invention has been shown and described
in detail to illustrate the application of the inventive principles, it
will be understood that the invention may be embodied otherwise without
departing from such principles.
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