Abstrict
A hot-gas engine electric heater that is partially disposable in
a heat exchange tube of a hot-gas engine and supplies heat to a
working fluid in the hot-gas engine wherein the heat exchange tube
has a contour. The heater includes a thin and circular-shaped base,
at least one conically-shaped and outwardly tapering heating element,
and a voltage regulator. The thin and circular-shaped base conforms
to the contour of the heat exchange tube and has an outer surface
and an inner surface that is conformingly and sealingly abuttable
against the heat exchange tube and is disposable externally thereto.
The at least one conically-shaped and outwardly tapering heating
element is horizontally oriented and extends perpendicularly outwardly
from the inner surface of the thin and circular-shaped base and
receives a voltage for heating the working fluid and is enterable
into the heat exchange tube so as to be non-protruding from the
heat exchange tube and eliminate wasted heat. And, the voltage regulator
is disposed on the outer surface of the thin and circular-shaped
base and regulates the voltage received by the at least one conically-shaped
and outwardly tapering heating element and is disposable externally
to the heat exchange tube and receives a voltage.
Claims
The invention claimed is:
1. A hot-gas engine electric heater partially disposable in a heat
exchange tube of a hot-gas engine and supplying heat to a working
fluid in the hot-gas engine, wherein the heat exchange tube has
a contour, comprising:
a) a thin and circular-shaped base conforming to the contour of
the heat exchange tube and having an outer surface and an inner
surface being conformingly and sealingly abuttable against the heat
exchange tube and disposable externally thereto;
b) at least one conically-shaped and outwardly tapering heating
element being horizontally oriented and extending perpendicularly
outwardly from said inner surface of said thin and circular-shaped
base and receiving a voltage for heating the working fluid and being
enterable into the heat exchange tube so as to be non-protruding
from the heat exchange tube and eliminating wasted heat; and
c) a voltage regulator disposed on said outer surface of said thin
and circular-shaped base and regulating the voltage received by
said at least one conically-shaped and outwardly tapering heating
element and being disposable externally to the heat exchange tube
and receiving a voltage.
2. The heater as defined in claim 1, wherein each heating element
of said at least one conically-shaped and outwardly tapering heating
elements terminates in a hemispherically-shaped free end.
3. The heater as defined in claim 1; further comprising a heat
seal positionable between said thin and circular-shaped base and
the heat exchange tube to compensate for irregularities in abutting
surfaces.
4. The heater as defined in claim 1, wherein said at least one
conically-shaped and outwardly tapering heating element is at least
two conically-shaped and outwardly tapering heating elements.
5. The heater as defined in claim 4, wherein said at least two
conically-shaped and outwardly tapering heating elements are vertically
spaced apart and aligned along a diameter of said inner surface
of said thin and circular-shaped base.
6. The heater as defined in claim 1, further comprising a power
supply for supplying the voltage to said voltage regulator and being
disposable externally to the heat exchange tube.
7. The heater as defined in claim 6, wherein said power supply
is in electrical communication with said voltage regulator by an
electrical connector.
8. The heater as defined in claim 6, wherein said power supply
is at least one of a generator and a battery.
9. A method of heating a working fluid in a heat exchange tube
of a hot-gas engine wherein the heat exchange tube has a contour,
comprising the step of heating the working fluid by a hot-gas engine
electric heater which comprises:
a) a thin and circular-shaped base conforming to the contour of
the heat exchange tube and having an outer surface and an inner
surface being conformingly and sealingly abuttable against the heat
exchange tube and disposable externally thereto;
b) at least one conically-shaped and outwardly tapering heating
element being horizontally oriented and extending perpendicularly
outwardly from said inner surface of said thin and circular-shaped
base and receiving a voltage for heating the working fluid and being
enterable into the heat exchange tube so as to be non-protruding
from the heat exchange tube and eliminating wasted heat; and
c) a voltage regulator disposed on said outer surface of said thin
and circular-shaped base and regulating the voltage received by
said at least one conically-shaped and outwardly tapering heating
element and being disposable externally to the heat exchange tube
and receiving a voltage.
10. The method as defined in claim 9, wherein each heating element
of said at least one conically-shaped and outwardly tapering heating
elements terminates in a hemispherically-shaped free end.
11. The method as defined in claim 9; further comprising a heat
seal positionable between said thin and circular-shaped base and
the heat exchange tube to compensate for irregularities in abutting
surfaces.
12. The method as defined in claim 9, wherein said at least one
conically-shaped and outwardly tapering heating element is at least
two conically-shaped and outwardly tapering heating elements.
13. The method as defined in claim 12, wherein said at least two
conically-shaped and outwardly tapering heating elements are vertically
spaced apart and aligned along a diameter of said inner surface
of said thin and circular-shaped base.
14. The method as defined in claim 9; further comprising a power
supply for supplying the voltage to said voltage regulator and being
disposable externally to the heat exchange tube.
15. The method as defined in claim 14, wherein said power supply
is in electrical communication with said voltage regulator by an
electrical connector.
16. The method as defined in claim 14, wherein said power supply
is at least one of a generator and a battery.
Description BACKGROUND OF THE INVENTION
The present invention relates to a hot-gas engine electric heater.
More particularly, the present invention relates to a hot-gas engine
electric heater that is partially disposable in a heat exchange
tube of a hot-gas engine and supplies heat to a working fluid in
the hot-gas engine wherein the heat exchange tube has a contour.
The heater includes a thin and circular-shaped base, at least one
conically-shaped and outwardly tapering heating element, and a voltage
regulator. The thin and circular-shaped base conforms to the contour
of the heat exchange tube and has an outer surface and an inner
surface that is conformingly and sealingly abuttable against the
heat exchange tube and is disposable externally thereto. The at
least one conically-shaped and outwardly tapering heating element
is horizontally oriented and extends perpendicularly outwardly from
the inner surface of the thin and circular-shaped base and receives
a voltage for heating the working fluid and is enterable into the
heat exchange tube so as to be non-protruding from the heat exchange
tube and eliminate wasted heat. And, the voltage regulator is disposed
on the outer surface of the thin and circular-shaped base and regulates
the voltage received by the at least one conically-shaped and outwardly
tapering heating element and is disposable externally to the heat
exchange tube and receives a voltage.
The most common type of hot-gas engine is the Stirling engine which
is an external-combustion engine that uses the closed Stirling cycle.
Stirling machines are energy conversion devices that operate over
a closed, regenerative thermodynamic cycle. The single-phase working
fluid is typically a gas such as helium or air.
Two configurations are commonly used. In one a piston varies the
working gas volume and a displacer shuttles the gas within the machine,
in the other configuration two pistons perform these tasks.
The gas is shuttled within the engine so that most of the gas is
in the compression space when the piston compresses the gas, and
most of the gas is in the expansion space when the piston allows
the gas to expand.
If heat is supplied to the expansion space, then the Stirling machine
acts as an engine, creating mechanical energy from thermal input.
If the piston, however, is driven by supplied mechanical energy,
then the Stirling machine acts as a cooler or heat pump.
The Stirling engine has pistons that move up and down in cylinders,
uses a fixed volume of a working fluid that constantly back and
forth between a hot top space and a cold bottom space in a cylinder,
and relies on continuous external combustion of a fuel that supplies
heat to the working fluid through the upper wall of a cylinder.
Stirling engines are often compared to internal combustion engines,
since both have pistons that reciprocate. In many ways Stirling
engines, however, are more similar to Rankine and closed-cycle Brayton
machines, because the thermal source and sink are outside the metal
walls that contain the working fluid. There are several advantages
to isolating the thermal source from the thermodynamic cycle. Namely,
a variety of heat sources can be utilized, such as concentrated
solar energy, radioisotopes, combustion, etc. If combustion is utilized,
it can occur in a steady-state process that can be efficient, low
in atmospheric and thermal emissions, and quiet, and the closed
cycle can use effective thermal regeneration which tends to increase
efficiency.
Rotary Rankine and closed-cycle Brayton machines scale well to
large sizes, but are less effective at lower power levels where
the rotor tip clearance becomes significant compared to the turbine
diameter, and blowby losses become relatively large. It is at these
lower power levels, hundred of watts and less, where Stirling engines
have a significant advantage in terms of conversion efficiency.
Stirling coolers are of interest because they can be efficient
over a large operating temperature range and mechanically quite
and simple compared to other low temperature refrigeration systems.
The potentially high performance is an attribute of the closed-cycle
regenerative thermodynamic cycle.
The operating temperature range is large compared to vapor-compression
type systems because phase change from vapor to liquid is not part
of the Stirling cycle.
Stirling coolers typically use helium, which is gaseous above 4.degree.
K. Stirling coolers can achieve liquid nitrogen temperatures (77.degree.
K) in a single displacer/regenerator stage and 10.degree. K in two
to four cascaded displacer/regenerator stages. Another advantage
is that the vibration at the cold end of the cooler can be quite
low. The cold end can be isolated from the compressor portion of
the machine through flexible tubing, and the displacer can be balanced,
or replaced by a pulse tube scheme to achieve even lower vibration
levels.
The theoretical efficiency of the Stirling engine is substantially
higher than that of diesel and other internal-combustion engines.
Robert Stirling, a Scottish clergyman, patented an external-combustion
engine in 1816. The first model was in use in 1818 for pumping water
out of a quarry. This engine and later ones designed by him used
air as the working fluid, and thus the Stirling engine also was
called a hot-gas engine.
Thousands of small Stirling engines were used in industry in the
19th century, but they fell into disuse.
In the late 1930's the N. V. Philips company in Eindhoven, Netherlands,
started research and development of engines working on the principle
of the Stirling engine.
By the early 1970's there was keen interest in Philips Stirling
engines because of their potential for reducing environmental pollution.
These engines have low emission of harmful exhaust gases, a low
noise level, a lower fuel consumption than that of gasoline engines,
and no oil consumption. Also, a 4-cylinder double-acting Stirling
engine runs as smoothly as a 16-cylinder gasoline engine. Philips
has built a number of laboratory-model and prototype Stirling engines
in sizes ranging from a few 10th's of a horsepower (hp) to 500 hp
per cylinder.
The Stirling engine is expected to find growing use in special
applications. It may be employed to haul ore in mines, where its
nontoxic emission and low noise level would be valuable.
A Stirling engine using radioisotopes for its heat supply may be
used to power an artificial heart.
In many respects the engine is technically able to replace gasoline
and diesel engines. Thus, if its cost could be reduced sufficiently,
it might even become widely used as a power plant in automobiles,
trucks, and buses.
In operation the Stirling engine produces a surplus of work in
the same way as the familiar gasoline or diesel engine does. The
working fluid in a cylinder is compressed at a low temperature,
heated rapidly, and then allowed to expand at a high temperature.
A gasoline or diesel engine, however, is an internal-combustion
engine, whereas a Stirling engine is an external-combustion engine.
In the internal-combustion engine, the rapid heating of the working
gas (air) takes place by the combustion of fuel inside the cylinder.
In contrast, however, the working gas of the Stirling engine obtains
its heat by the combustion of a fuel outside the cylinder. The heat
liberated by combustion is transmitted through the cylinder wall
to the working gas. In this case, the working gas does not take
part in the combustion. Consequently, the working gas does not need
to be air but can be helium or some other gas chosen for optimum
engine performance.
Numerous engine configurations for accomplishing the Stirling process
have been designed. The most promising are the displacer system
and the double-acting system.
In the displacer system, the rapid heating and subsequent cooling
of the working gas take place by means of a two-piston system that
makes the gas flow back and forth through two heat exchangers, respectively
called a heater (constant high temperature) and a cooler (constant
low temperature). To prevent wasteful loss of heat a third heat
exchanger, called a regenerator, is inserted between the heater
and the cooler.
The most progress has been made with a displacer system using a
rhombic drive for two output shafts, one of which rotates clockwise
and the other counterclockwise.
Stirling machines are classified by the type, arrangement and motion
control of the moving components. The types of moving component
include pistons, which have seals and cause volume and pressure
changes as they move, and displacers, which transfer gas between
the hot and cold sections of the machine without causing an overall
volume change.
The alpha configuration features two pistons, each in its own cylinder.
The beta configuration has a piston and a displacer in the same
cylinder. The gamma configuration has a piston and a displacer,
each in its own cylinder.
The double-acting configuration has multiple cylinders and elongated
power pistons, and can be considered as coupled alpha engines, where
the thermodynamic cycle takes place between the top of one piston
and the bottom of the next piston. Liquid-piston engines can be
considered to be of the alpha configuration.
The motions of the moving components can be controlled by connecting
rods (kinematic) or the result of gas forces and spring/mass dynamics
(free-piston). The Ringbom engine has a kinematic piston and a free-displacer.
The Martini-Ringbom has a kinematic displacer and a free piston.
As shown in FIG. 1, which is a diagrammatic representation of a
prior art typical Stirling engine utilizing a double acting system,
the double-acting system 11, invented by Philips as early as 1942,
contains a hot space (expansion space) 12 at the top 13 of each
cylinder 14 and a cold space (compression space) 15 at the bottom
16 of each cylinder 14.
The hot space 12 of a cylinder is connected to the cold space 15
of an adjacent cylinder through a heat exchange tube 17, that contains
a heater 18, a regenerator 19, and a cooler 20.
The pistons 21 in the cylinders 14 move with suitable phase shift
between them. In the case of 4 cylinders, the shift is 90 degrees.
It now seems feasible to attain a double-acting engine with an
engine weight per brake horsepower (bhp) that approaches that of
the gasoline engine (four pounds per bhp).
Stirling engine technology has come a long way in the last 50 years.
Highly efficient, durable engines have been demonstrated at several
power levels. Improvements are still needed in several areas.
Engine designs tend to be based largely on rigorous computer codes.
These codes attempt to model oscillating flows and non-steady heat
transfer that is not well understood. The codes cannot be fundamentally
verified, since it is not possible at present to make the high speed
measurements necessary. Analysis improvements are steadily being
made, which will lead to more optimized engine performance.
High efficiency, high power density engines use a pressurized working
fluid. Effective seals are crucial, especially if helium or hydrogen
are the working fluid. Mechanical seals have been used successfully,
but may not be suitable for long life operation. Gas bearings/seals
tend to reduce the efficiency of the engine, but may be the long-term
solution.
The bulk of the cost for a mass-produced Stirling engine will be
due to the heat exchangers, especially the regenerator. The cost
is high because the suitable materials tend to be expensive and
hard to machine, and because the heat exchanger designs tend to
be intricate. Development of ceramic technology may be needed.
Numerous innovations for heat engines have been provided in the
prior art that will be described. Even though these innovations
may be suitable for the specific individual purposes to which they
address, however, they differ from the present invention in that
they do not teach hot-gas engine electric heater that is partially
disposable in a heat exchange tube of a hot-gas engine and supplies
heat to a working fluid in the hot-gas engine wherein the heat exchange
tube has a contour. The heater includes a thin and circular-shaped
base, at least one conically-shaped and outwardly tapering heating
element, and a voltage regulator. The thin and circular-shaped base
conforms to the contour of the heat exchange tube and has an outer
surface and an inner surface that is conformingly and sealingly
abuttable against the heat exchange tube and is disposable externally
thereto. The at least one conically-shaped and outwardly tapering
heating element is horizontally oriented and extends perpendicularly
outwardly from the inner surface of the thin and circular-shaped
base and receives a voltage for heating the working fluid and is
enterable into the heat exchange tube so as to be non-protruding
from the heat exchange tube and eliminate wasted heat. And, the
voltage regulator is disposed on the outer surface of the thin and
circular-shaped base and regulates the voltage received by the at
least one conically-shaped and outwardly tapering heating element
and is disposable externally to the heat exchange tube and receives
a voltage.
FOR EXAMPLE, U.S. Pat. No. 4,126,995 to Asselman et al. teaches
a hot-gas engine in which the transfer of heat from the heat-source
to the meltable material of a heat storage reservoir is effected
exclusively indirectly via the working medium in order to prevent
overheating, fast corrosion, and cracking of the reservoir walls.
ANOTHER EXAMPLE, U.S. Pat. No. 4,715,183 to Meijer et al. teaches
an external heating system for a heat engine such as a Stirling
cycle engine which permits thermal energy to be provided by solar
energy or fuel combustion sources. The system employs a complexly
shaped heat pipe evaporator section having an enclosed cavity for
receiving solar energy and another section forming hollow fins which
is exposed to hot combustion gasses. Accordingly, either heat source
may be used to evaporate working fluid within the heat pipe which
is transferred to the associated heat engine.
STILL ANOTHER EXAMPLE, U.S. Pat. No. 4,768,342 to Darooka teaches
a Stirling engine heater head that is constructed to provide an
annular heat exchange region defined between a pressure vessel sidewall
and the engine displacer cylinder. From an external manifold, through
which a heated fluid flows, either heat exchange tubes are sealingly
introduced into the heat exchange region. Thermal energy is thus
transferred to the engine working fluid, while the heated fluid
is maintained isolated from the vessel walls and the displacer cylinder.
For a compound Stirling engine configuration, thermal energy is
introduced from a common heated fluid manifold to the heat exchange
regions of a pair of axially aligned Stirling engine modules via
heat pipes or heat exchange tubes. This manifold may be sealingly
joined with the pressure vessel to create a chamber which is pressurized
to pressure balance the vessel walls.
YET ANOTHER EXAMPLE, U.S. Pat. No. 4,894,989 to Mizuna et al. teaches
a heater for use with a Stirling engine and a method for heating
a working fluid for a Stirling engine. The heater has a burner,
heater tubes disposed in the burner, a space formed around the heater
tubes which is filled with the heat-storing material, and a high-temperature
heat source. The heat-storing material is sealed by a seal member.
Heat produced by the high-temperature heat source is supplied to
the heater tubes via the heat-storing material, hence the heat-storing
material acts as a secondary heat source. Heat is stored in the
heat-storing material in the form of sensible heat or latent heat,
or a chemical reaction is employed.
FINALLY, STILL YET ANOTHER EXAMPLE, is the STM 4-120 Stirling Engine
manufactured by Stirling Thermal Motors, inc., 275 Metty Drive,
Ann Arbor, Mich. 48103 USA, Phone: (313) 995-1755, Fax: (313) 995-0610.
The STM 4-120 Stirling Engine is the result of 15 years of Stirling
engine development at Stirling Thermal Motors, Inc. (STM) in Ann
Arbor, Mich., USA. This engine converts any form of heat of sufficient
high temperature to either mechanical or electrical power.
The four cylinder, double acting STM 4-120 engine, is designed
to meet industrial as well as automotive specifications. Double
acting means that each piston acts as both power and displacer piston
and there is only one piston in each cylinder.
This engine has demonstrated performance and fuel efficiency equivalent
to a Diesel engine, with ultra-low emissions and up to 90% less
noise than a Diesel engine.
The industrial version of the STM 4-120 engine is derated to operate
at lower speed and temperature to assure a long service free life
(60,000 hours). The automotive version operates at higher speed
and temperature and is capable of producing up to 100 kW (134 hp).
The engine's environmentally friendly qualities has generated interest
in manufacturing and marketing this engine for commercial applications.
These qualities include multi-fuel capability, ultra-low exhaust
emissions, low noise, vibration level, and long service free life.
The use of a variable swash plate changes the stroke, which in
turn changes the power at constant working gas pressure, results
in exceptional part-load performance where the maximum efficiency
is maintained over a broad load range, fast transient response wherein
the power changes from idle to full load in a 1/3 of a second, and
compact design with constant thrust load on the swash plate, constant
torque, and very low vibration.
The measured power output for the industrial version is 40 kW (40
hp) at 1800 rpm. The measured fuel to shaft efficiency is 36% using
either natural gas or gasoline (including the efficiency of the
complete combustion system). This shaft efficiency corresponds to
a measured thermal efficiency of 42% which is based on the heat
into the engine heater head (receiver) to shaft power.
The heat generated by solar energy using a concentrator is absorbed
by the engine receiver inside the aperture. Thus, for solar applications,
thermal efficiency will vary dependent upon the solar concentrator
characteristics.
A higher concentration ratio, combined with an even flux pattern
results in higher engine efficiency, and vice versa.
Compared to fossil fuel receivers, direct insulating solar receivers
will have slightly lower thermal efficiency while sodium heat pipe
receivers will have slightly higher efficiency.
Independent analysis projects STM 4-120 engine costs to be equal
to a similar sized IC-engine (diesel or gasoline) in volume production.
The STM 4-120 engine has fewer components and moving parts than
an IC-engine of similar size.
The STM 4-120 engine can be used for a broad variety of applications
by simply changing the receiver/heater head to use various heat
sources such as combusting liquid, gaseous and biomass fuels or
concentrated solar energy. This commonality results in a mass produced
base engine with lower manufacturing costs.
STM Power Conversion Systems are 25 kWe generator sets operating
on natural gas, LP gas, or diesel fuel. They provide environmentally
friendly and socially accepted distributed electric power for urban
or rural applications, off-grid or on-grid.
______________________________________ Technical Specifications
of the STM 4-120 Stirling Engine ______________________________________
Engine size (swept volume) 0.48 liter Rated Power Industrial Version
30 kW/1800 rpm Specific Power: Industrial Version 60 kW/liter Automotive
Version 200 kW/liter (268 hp/liter) Weight 124 kg (273 lbs) Working
Gas Helium or Hydrogen Working Gas hermetically sealed within the
cylinders by bellows ______________________________________
It is apparent that numerous innovations for heat engines have
been provided in the prior art that are adapted to be used. Furthermore,
even though these innovations may be suitable for the specific individual
purposes to which they address, however, they would not be suitable
for the purposes of the present invention as heretofore described.
SUMMARY OF THE INVENTION
ACCORDINGLY, AN OBJECT of the present invention is to provide a
hot-gas engine electric heater that avoids the disadvantages of
the prior art.
ANOTHER OBJECT of the present invention is to provide a hot-gas
engine electric heater that is simple and inexpensive to manufacture.
STILL ANOTHER OBJECT of the present invention is to provide a hot-gas
engine electric heater that is simple to use.
YET ANOTHER OBJECT of the present invention is to provide a hot-gas
engine electric heater that eliminates the need for liquid and gas
fuels, solar power, nuclear power, dry fuel.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that is non-polluting, such as
from batteries, oil, gas, carbon dioxide, and conforms to the zero-emissions
power plant mandate for 1998.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that has unlimited use as a power
plant.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that can be retrofitted to existing
hot-gas engines.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that eliminates the need to charge
batteries.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that is energy efficient.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that is partially disposable in
a heat exchange tube of a hot-gas engine and supplies heat to a
working fluid in the hot-gas engine wherein the heat exchange tube
has a contour.
BRIEFLY STATED, STILL YET ANOTHER OBJECT of the present invention
is to provide a hot-gas engine electric heater that includes a thin
and circular-shaped base, at least one conically-shaped and outwardly
tapering heating element, and a voltage regulator.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein the thin and circular-shaped
base conforms to the contour of the heat exchange tube and has an
outer surface and an inner surface that is conformingly and sealingly
abuttable against the heat exchange tube and is disposable externally
thereto.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein the at least one conically-shaped
and outwardly tapering heating element that is horizontally oriented
and extends perpendicularly outwardly from the inner surface of
the thin and circular-shaped base and receives a voltage for heating
the working fluid and is enterable into the heat exchange tube so
as to be non-protruding from the heat exchange tube and eliminate
wasted heat.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein the voltage regulator is
disposed on the outer surface of the thin and circular-shaped base
and regulates the voltage received by the at least one conically-shaped
and outwardly tapering heating element and is disposable externally
to the heat exchange tube and receives a voltage.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein each heating element of
said at least one conically-shaped and outwardly tapering heating
elements terminates in a hemispherically-shaped free end.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that further includes a heat seal
that is positionable between the thin and circular-shaped base and
the heat exchange tube to compensate for irregularities in abutting
surfaces.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein the at least one conically-shaped
and outwardly tapering heating element is at least two conically-shaped
and outwardly tapering heating elements.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein the at least two conically-shaped
and outwardly tapering heating elements are vertically spaced apart
and aligned along a diameter of the inner surface of the thin and
circular-shaped base.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater that further includes a power supply
for supplying the voltage to the voltage regulator and being disposable
externally to the heat exchange tube.
YET STILL ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein the power supply is in
electrical communication with the voltage regulator by an electrical
connector.
STILL YET ANOTHER OBJECT of the present invention is to provide
a hot-gas engine electric heater wherein the power supply is at
least one of a generator and a battery.
YET STILL ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the heat exchange tube has a contour.
STILL YET ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine that includes the step of heating the working fluid
by a hot-gas engine electric heater.
YET STILL ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the hot-gas engine electric heater includes
a thin and circular-shaped base, at least one conically-shaped and
outwardly tapering heating element, and a voltage regulator.
STILL YET ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the thin and circular-shaped base conforms
to the contour of the heat exchange tube and has an outer surface
and an inner surface that is conformingly and sealingly abuttable
against the heat exchange tube and is disposable externally thereto.
YET STILL ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the at least one conically-shaped and outwardly
tapering heating element is horizontally oriented and extends perpendicularly
outwardly from the inner surface of the thin and circular-shaped
base and receives a voltage for heating the working fluid and is
enterable into the heat exchange tube so as to be non-protruding
from the heat exchange tube and eliminate wasted heat.
STILL YET ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the voltage regulator is disposed on the
outer surface of the thin and circular-shaped base and regulates
the voltage received by the at least one conically-shaped and outwardly
tapering heating element and is disposable externally to the heat
exchange tube and receives a voltage.
YET STILL ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein each heating element of the at least one
conically-shaped and outwardly tapering heating elements terminates
in a hemispherically-shaped free end.
STILL YET ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine that further includes a heat seal that is positionable
between the thin and circular-shaped base and the heat exchange
tube to compensate for irregularities in abutting surfaces.
YET STILL ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the at least one conically-shaped and outwardly
tapering heating element is at least two conically-shaped and outwardly
tapering heating elements.
STILL YET ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the at least two conically-shaped and outwardly
tapering heating elements are vertically spaced apart and aligned
along a diameter of the inner surface of the thin and circular-shaped
base.
YET STILL ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine that further includes a power supply for supplying
the voltage to the voltage regulator and being disposable externally
to the heat exchange tube.
STILL YET ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the power supply is in electrical communication
with the voltage regulator by an electrical connector.
YET STILL ANOTHER OBJECT of the present invention is to provide
a method of heating a working fluid in a heat exchange tube of a
hot-gas engine wherein the power supply is at least one of a generator
and a battery.
The novel features which are considered characteristic of the present
invention are set forth in the appended claims. The invention itself,
however, both as to its construction and its method of operation,
together with additional objects and advantages thereof, will be
best understood from the following description of the specific embodiments
when read and understood in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
The figures on the drawing are briefly described as follows:
FIG. 1 is a diagrammatic representation of a prior art typical
Stirling engine utilizing a double acting system;
FIG. 2 is an enlarged diagrammatic representation of a heat exchange
tube utilizing the present invention, which would be substituted
in the area indicated by arrow 2 enclosed by the dotted ellipses
in FIG. 1;
FIG. 3 is a diagrammatic side elevational view of the present invention
taken on line 3--3 of FIG. 2; and
FIG. 4 is a diagrammatic cross sectional view, with parts broken
away taken on line 4--4 of FIG. 2.
______________________________________ LIST OF REFERENCE NUMERALS
UTILIZED IN THE DRAWING ______________________________________ 11
double-acting system 12 hot space (expansion space) in the top 13
of the cylinder 14 of the double-acting system 11 13 top of the
cylinder 14 of the double-acting system 11 14 cylinder of the double-acting
system 11 15 cold space (compression space) in the bottom 16 of
the cylinder 14 of the double-acting system 11 16 bottom of the
cylinder 14 of the double-acting system 11 17 heat exchange tube
of the double-acting system 11 18 heater in the heat exchange tube
17 of the double-acting system 11 19 regenerator in the heat exchange
tube 17 of the double-acting system 11 20 colloer in the heat exchnage
tube 17 of the double-acting system 11 21 pistons in the cylinder
14 of the double-acting system 11 30 hot-gas engine electric heater
of the present invention 32 working fluid in the double-acting system
11 34 thin and circular-shaped base of the hot-gas engine electric
heater 30 36 base outer surface of the thin and circular-shaped
base 34 of the hot-gas engine electric heater 30 38 base inner surface
of the thin and circular-shaped base 34 of the hot-gas engine electric
heater 30 40 three conically-shaped and outwardly tapering heating
elements of the hot-gas engine electric heater 30 41 heating element
hemispherically-shaped free end of each heating element of the three
conically-shaped and outwardly tapering heating elements 40 of the
hot-gas engine electric heater 30 42 voltage regulator of the hot-gas
engine electric heater 30 44 power supply of the hot-gas engine
electric heater ______________________________________ 30
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the figures in which like numerals indicate like
parts, and particularly to FIG. 2, which is a diagrammatic representation
of a heat exchange tube utilizing the present invention, the hot-gas
engine electric heater of the present invention is shown generally
at 30 adapted to the heat exchange tube 17 with the regenerator
19 and the cooler 20 therein and heating a working fluid 32 therein.
The configuration of the hot-gas engine electric heater 30 can
best be seen in FIGS. 2-4; which are an enlarged diagrammatic representation
of a heat exchange tube utilizing the present invention, which would
be substituted in the area indicated by arrow 2 enclosed by the
dotted ellipses in FIG. 1; a diagrammatic side elevational view
of the present invention taken on line 3--3 of FIG. 2; and a diagrammatic
cross sectional view, with parts broken away taken on line 4--4
of FIG. 2; respectively, and as such will be discussed with reference
thereto.
The hot-gas engine electric heater 30 includes a thin and circular-shaped
base 34 that conforms to the contour of the heat exchange tube 17
and has a base outer surface 36 and a base inner surface 38 that
is conformingly and sealingly abuttable against the heat exchange
tube 17 and disposable externally thereto.
It is to be understood, however, that a heat seal may be provided
between the thin and circular-shaped base 34 and the heat exchange
tube 17, if necessary to compensate for irregularities in abutting
surfaces.
The hot-gas engine electric heater 30 further includes three conically-shaped
and outwardly tapering heating elements 40 that are horizontally
oriented and vertically spaced apart and extend perpendicularly
outwardly from the base inner surface 38 of the thin and circular-shaped
base 34, aligned along a diameter thereof, and are enterable into
the heat exchange tube 17 for heating the working fluid 32 therein
so as to be non-protruding from the heat exchange tube 17 and eliminate
wasted heat.
Each heating element of the three conically-shaped and outwardly
tapering heating elements 40 terminates in a heating element hemispherically-shaped
free end 41.
The significance of the configuration of the three conically-shaped
and outwardly tapering heating elements 40 can best be understood
from the discussion presented, infra.
Heat convection is the term applied to the heat transfer mechanism
that occurs when a fluid of some known temperature flows past a
solid surface at some different temperature. The flow of heat between
the surface and the fluid is expressed in terms of the heat coefficient
h.
The determination of the heat coefficient h necessitates the solution
of the governing equations of a viscous, heat-conducting fluid.
These equations in their general form, however, are not solvable
analytically. The problem is simplified by the utilization of boundary
layer theory.
In this simplified form, the fundamental equations to be solved
near the body surface are expressed, infra, for an incompressible
fluid:
Conservation of mass: ##EQU1##
Equation of motion: ##EQU2##
Conservation of energy: ##EQU3## wherein: x=the coordinate measured
parallel to the body surface
y=the coordinate measured normal to x
v.sub.x =the fluid velocity in the direction of x
v.sub.y =the fluid velocity in the direction of y
.rho.=the fluid density
p=the pressure
C.sub.p =the specific heat
.beta.=the coefficient of volume expansion
T.sub.f =the fluid temperature, to distinguish it from temperatures
within the solid, and is generally a function of position within
the fluid (i.e. a function of x and y)
.tau.=the shear stress within the fluid domain
q/A=the heat flux within the fluid domain
For laminar flow .tau. and q/A are expressed in terms of the gradients
of velocity and temperature within the fluid by utilization of the
hypothesized rate laws, infra: ##EQU4## wherein: v=the kinematic
viscosity
.alpha.=the thermal diffusivity
In the instance when turbulent flow exists in the fluid, it is
customary to augment these rate coefficients with their turbulent
counterparts, the so-called eddy viscosity and eddy diffusivity.
In the equation of motion discussed, supra, the last term represents
buoyant forces arising from temperature gradients in the fluid and
may be absent in cases of pure forced convection. Likewise, in the
conservation of energy equation discussed, supra, the first term
on the right-hand side represents the rate of dissipation of kinetic
energy into thermal energy through viscous action, and it may in
certain cases be negligible.
In general, the solution to a particular convection problem consists
of the simultaneous solution of the conservation of mass equation,
the equation of motion, and the conservation of energy equation
discussed, supra, under the appropriate boundary conditions, for
the fluid temperature T.sub.f (x,y). The heat transfer coefficient
is then determined by utilization of Fourier's law at the surface:
##EQU5## wherein: s=the surface
Usually, the solutions referred to, supra, are expressed in dimensionless
form. If the conservation of mass equation, the equation of motion,
the conservation of energy equation, the rate law equations, and
the Fourier's law at the surface equation discussed, supra, are
nondimensionized by introducing a characteristic velocity U and
a characteristic dimension L, the dependance implied, supra, of
h on the other parameters may be expressed as:
In the equation, supra, the quantities shown are dimensionless
groupings of variables that bear the following designations:
Nusselt number: ##EQU6##
Reynolds number: ##EQU7##
Grashoff number: ##EQU8##
Eckert number: ##EQU9##
Prandtl number: ##EQU10##
Thus it is apparent that convection is a function of surface geometries
and hydrodynamic boundary conditions. The region in which the velocity
and temperature of the fluid changes occur in the boundary layer.
Because velocity and temperature gradients both approach zero at
the outer edge of the boundary layer, there is no heat flow out
of the boundary layer by conduction or convection.
An accounting of all of the energy streams entering and leaving
a small volume in the boundary layer during steady-state conditions
yield: ##EQU11## wherein: .kappa.=the thermal conductivity of the
fluid
w=the weight density of the fluid
c.sub.p =the specific heat at constant pressure of the fluid
u=the velocity component of the fluid in the x direction
v=the velocity component of the fluid in the y direction
The equation, supra, states that the net energy conducted into
the element equals the increase in energy of the fluid leaving (convected)
over what it had entering.
At the surface, u=v=0 and d.sup.2 t/dx.sup.2 =dt/dx=0. Thus, .kappa.(d.sup.2
t/dy.sup.2)=0, and the equation, infra, is obtained: ##EQU12## wherein:
q=the time rate of flow through an infinitesimally thin layer dx
A=the cross-sectional area normal to the direction of flow
The equation, supra, shows that the heat transfer in the immediate
vicinity of the surface is accomplished by conduction through a
thin layer of the fluid which does not move relative to the surface.
At a very small distance from the surface, however, the velocity
becomes finite and some of the energy conducted normal to the surface
is convected parallel to it. This process causes the temperature
gradient to decrease, eventually to zero. The solution of a problem
requires determination of the temperature distribution throughout
the boundary layer. From this, the temperature gradient at the surface
and the rate of heat flow can be computed.
The effect of energy leaving a surface and remaining in the boundary
layer is a gradual increase in temperature of the fluid in the layer
as it moves therealong, and a diffusion of energy further from the
surface entraining more of the fluid in, and thickening, the boundary
layer.
Thus, it is apparent from the discussion, supra, that to maximize
heat transfer, the boundary layer on the surface must be maximized
while boundary layer separation from the surface must be minimized.
The use of the three conically-shaped heating elements accomplish
this.
The use of a circular-shaped cross section for each heating element
of the three conically-shaped and outwardly tapering heating elements
40 maximizes boundary layer size while it minimizes boundary layer
separation.
The use of three conically-shaped and outwardly tapering heating
elements 40 being horizontally oriented and vertically spaced apart
and aligned along a diameter of the base inner surface 38 of the
thin and circular-shaped base 34, allows the working fluid 32 heated
by one heating element of the three conically-shaped and outwardly
tapering heating elements 40 to be further heated by the next highest
heating element of the three conically-shaped and outwardly tapering
heating elements 40, as a result of the isotherms flowing vertically
and outwardly from the surface.
The conical shape of each heating element of the three conically-shaped
and outwardly tapering heating elements 40 and the hemispherical
shape of the heating element hemispherically-shaped free end 41
of each heating element of the three conically-shaped and outwardly
tapering heating elements 40 reduces impedance to the flow of the
working fluid 32 therepast so that turbulent flow is minimized and
laminar flow is maximized which further contributes to maximizing
boundary layer and minimizing boundary layer separation.
The choice for using three heating elements of the three conically-shaped
and outwardly tapering heating elements 40 is based on the fact
that in general, when an electric current i flows, heat H.sub.dissipated
is dissipated in all conducting elements owing to their ohmic resistance.
If the combined resistance of these is r, the Joulean heat production
in time d.tau. is given by: ##EQU13##
Since i may be taken as a constant, the heat dissipated H.sub.dissipated
for a given charge z passed therefore varies with r. Thus, it can
be seen that the use of the three heating elements of the three
conically-shaped and outwardly tapering heating elements 40 is an
ample number to maximize heat transfer by increasing the amount
of resistance while the spaces therebetween do not impede isotherm
development and flow between adjacent heating elements of the three
heating elements of the three conically-shaped and outwardly tapering
heating elements 40.
It is therefore apparent from the discussion, supra, that the configuration
of the three heating elements of the three conically-shaped and
outwardly tapering heating elements 40 is not merely a matter of
design choice but is significant and of critical importance. It
therefore must be considered in determining patentability, as was
decided in In re Dailey et al., 149 USPQ 47 (CCPA 1976), where the
Court held that the shape of a device must be considered in determining
patentability, if the shape is significant:
" . . . the configuration of the container is a `mere matter
of choice` not significantly novel . . . , [since] . . . Appellants
have provided no argument which convinces us that the particular
configuration of their container is significant . . . " [Emphasis
added]
The hot-gas engine electric heater 30 further includes a voltage
regulator 42 disposed on the base outer surface 36 of the thin and
circular-shaped base 34 and regulates the voltage supplied to the
three conically-shaped and outwardly tapering heating elements 40,
and is disposable externally to the heat exchange tube 17.
The hot-gas engine electric heater 30 further includes a power
supply 44 that is in electrical communication with the voltage regulator
42, by an electrical connector 46, and supplies voltage to the voltage
regulator 42, and is disposable externally to the heat exchange
tube 17.
It is to be understood that the power supply 44 may be a generator,
a battery, or a combination thereof that may be switched back and
forth, if so desired.
It will be understood that each of the elements described above,
or two or more together, may also find a useful application in other
types of constructions differing from the types described above.
While the invention has been illustrated and described as embodied
in a hot-gas engine electric heater, it is not limited to the details
shown, since it will be understood that various omissions, modifications,
substitutions and changes in the forms and details of the device
illustrated and its operation can be made by those skilled in the
art without departing in any way from the spirit of the present
invention.
Without further analysis, the foregoing will so fully reveal the
gist of the present invention that others can, by applying current
knowledge, readily adapt it for various applications without omitting
features that, from the standpoint of prior art, fairly constitute
characteristics of the generic or specific aspects of this invention.
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