U.S. patent number 3,774,374 [Application Number 05/151,349] was granted by the patent office on 1973-11-27 for environmental control unit.
This patent grant is currently assigned to Gas Developments Corporation. Invention is credited to Raymond James Dufour, William F. Rush.
United States Patent |
3,774,374 |
Dufour , et al. |
November 27, 1973 |
ENVIRONMENTAL CONTROL UNIT
Abstract
The application discloses an improved environmental control unit
using in unitary combination a heat pipe as the heat source for the
regeneration of the L-wheel. The heat pipe contains sodium metal
which is vaporized by heating one end of the pipe in a firebox
remote from the environmental control unit. The other end of the
heat pipe extends into the heating section just upstream from the
L-wheel. There, the air passing over the heat pipe surface, which
optionally may be finned, causes sodium vapor in the pipe to
condense, thus giving up its latent heat of condensation to the air
stream, heating it to a temperature sufficient to dry the wheel.
The improved heat pipe is efficient, safe, easily controllable and
self-adjustable.
Inventors: |
Dufour; Raymond James (Wheaton,
IL), Rush; William F. (Arlington Heights, IL) |
Assignee: |
Gas Developments Corporation
(Chicago, IL)
|
Family
ID: |
22538361 |
Appl.
No.: |
05/151,349 |
Filed: |
June 9, 1971 |
Current U.S.
Class: |
96/112; 126/99R;
96/125; 55/312; 62/94; 165/7; 165/58; 165/104.21; 237/17 |
Current CPC
Class: |
F24F
3/1423 (20130101); F24F 2203/1072 (20130101); F24F
2203/1012 (20130101); F24F 2203/1084 (20130101); F24F
2003/1464 (20130101); F24F 2203/1008 (20130101); F24F
2203/1032 (20130101); F24F 2203/102 (20130101); F24F
2203/1064 (20130101); F24F 2203/104 (20130101); F24F
2203/1016 (20130101) |
Current International
Class: |
F24F
3/147 (20060101); F24F 3/12 (20060101); B01d
053/06 () |
Field of
Search: |
;55/34,163,208,269,390,77,222,233,270,312,316,388 ;165/6,7,105
;62/94,271 ;237/17 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Talbert, Jr.; Dennis E.
Claims
We claim:
1. An environmental control unit comprising a housing; baffle means
disposed within said housing, dividing it into an inlet section and
a regeneration section having a regeneration air stream passing
therethrough; an S-wheel and an L-wheel disposed in said housing to
rotate between said inlet section and said regeneration section; a
heating section disposed in siad regeneration section and between
said L-wheel and said S-wheel, which further includes:
a a plurality of heat pipes, each heat pipe having an evaporative
section, a condenser section and an intermediate portion connecting
said evaporative and condenser sections,
b each of said heat pipes being disposed with its condenser section
in said heating section in a vertical plane in vertical, spaced
apart alignment with each of the other condenser sections,
c means defining a firebox disposed exteriorly of said regeneration
section and having disposed therein a fuel gas burner creating a
flame in contact with and in heat transfer relation with the
evaporative section of each of said heat pipes, such evaporative
sections being spaced apart from each other horizontally in said
fire box,
d said firebox being disposed with relation to said regeneration
air stream to isolate the burner combustion products from said air
stream,
e a flue for exhausting combustion products from said burner
exteriorly of said regeneration section and without passing through
said regeneration section,
f louver means comprising a plurality of pivotally mounted louvers
disposed in the heating section upstream of the condenser sections
of the heat pipes for controlling the volume of air flowing through
said regeneration section and to provide laminar air flow over said
heat pipes in a predetermined path,
g said fuel gas burner having a fuel gas line provided with a valve
means for regulating the flow of fuel gas to said fuel gas
burner,
h temperature sensing means disposed in said regeneration section
adjacent the outlet side of said L-wheel for sensing the
temperature of the gas in said regeneration section exiting said
L-wheel,
i operating means operatively connected to said louver means for
adjustable pivoting said louvers for adjustably regulating air flow
over said condenser sections,
j actuating means coupled between said temperature sensing means
and said valve means for controlling the flow fo fuel gas to said
fuel gas burner in response to the temperature sensed by said
temperature sensing means, and
k said actuating means being further coupled between said
temperature sensing means and said operating means for controlling
the position of said louvers in response to the temperature sensed
by said temperature sensing means, and
l said louver means, condenser sections and said heating section
being so operatively constructed and arranged that all of the air
passing between the louvers flows in laminar air flow heat exhange
relationship over said condenser sections in said predetermined
path,
Whereby said heat pipes provide a relatively uniform heating of
said regeneration air stream and are thermally selfadjusting and
rapidly responsive to temperature and volumetric air flow changes
in said regeneration air stream.
2. An improved environmental control unit as in claim 1 which
includes baffles disposed in association with the configuration of
said pipe to direct air flow thereover in a predetermined
manner.
3. An environmental control unit as in claim 1 wherein said heat
pipe contains a material selected from sodium, mercury or water as
the heat transfer material.
4. An environmental control unit as in claim 1 wherein said means
defining a firebox is located exteriorly of said environmental
control unit housing.
Description
BACKGROUND AND FIELD OF THE INVENTION
This invention relates to environmental control units which provide
cooling in the summer, heating in the winter, and year round
control of humidity with effective removal of dust and pollen. In
particular, the unit of this invention employs an improved heating
section utilizing a heat pipe for providing highly uniform heat
transfer to the air stream passing thereover, and which is
self-adjusting to variations in the air stream temperature and
volumetric flow.
Environmental control units of the so-called Munters type
(hereinafter called MEC units) operate on the principle that dry,
warm air can be simultaneously cooled and humidified by contacting
it with water. In geographic areas where the air is both warm and
humid, it must be dried before it can be cooled by evaporation. The
MEC unit incorporates both these cooling and drying functions in an
assembly which utilizes a gas burner in conjunction with a rotating
desiccant wheel to remove moisture from the outside air. During the
heating season, an MEC unit can be used to warm and humidify cold,
dry air by making minor changes in the unit's operating cycle.
Typical examples of these units are shown in Munters U.S. Pat. Nos.
2,926,502 and 3,009,540 and in the patent to Pennington 3,398,510
and patents cited therein.
The essential parts of an MEC unit are two, treated rotating
asbestos wheels, one operating as a desiccant support and the other
as a heat exchanger. The wheels employed in the system are
basically rolls of corrugated material, wound so that there are
thousands of passages aligned parallel to the axis of the wheel and
to permit the free flow of air therethrough. These wheels are
spaced apart laterally and operate in combination with a gas burner
for air drying and a water curtain for cooling and
rehumidification.
During the cooling operation, outside ambient air is continuously
drawn into the rotating, desiccant-treated L-wheel where moisture
is removed. The wheel is so named because it removes moisture from
the air and liberates latent heat of absorption and adsorption to
the air passing therethrough. Thetemperature of incoming air is
thus considerably increased. Heat is then removed from this air by
the rotating S-Wheel, so named because it removes the sensible heat
from the incoming air. The air exits from the S-wheel as tempered,
dry air. This tempered, dry air then passes through a water
curtain, ordinarily in the form of an E-pad structure, named such
after its function as an evaporative pad. The air is further cooled
by evaporation and rehumidified to the desired condition by passage
through the E-pad before it is delivered to the conditioned
space.
The second half of the cycle is that of regeneration, which is
accomplished by exhausting air from the conditioned space through
the water curtain in the E-pads where it is further cooled by
evaporation. This cooled exhaust air provides the means for
thermally regenerating the S-wheel which has rotated now into the
regenerative half of the unit. The exhaust air picks up heat from
the S-wheel which correspondingly is cooled and rotates into the
incoming stream, there to pick up heat from the incoming air and
thus completing its aspect of the cycle. The exhaust air which has
been warmed by the S-wheel is then conventionally further heated by
means of a gas burner placed in the heating section of the unit,
which heating section is disposed between the S-and the L-wheels.
The burner raises the temperature of the regenerating air to a high
value, on the order of 500.degree. F, and it is thus relatively
dry. This relatively dry, hot air and the flue products pass
through the L-wheel. Because the air is relatively dry, it removes
the moisture from the desiccant material adsorbed onto the L-wheel,
thus effecting moisture regeneration of the L-wheel so that it can
continuously remove moisture from the outside air which is taken
into the system by rotation of the L-wheel into the incoming side
of the machine.
For the heating season, an MEC unit has a capability of delivering
heated, filtered and humidified air to the conditioned space.
Conversion of an MEC unit from cooling to heating is accomplished
very simply by stopping rotation of the S-wheel and increasing the
speed of rotation of the L-wheel. Unlike most air conditioning
systems, in both the heating and cooling cycles, an MEC unit can
utilize 100 percent outside air. In addition, because of the use of
the water curtain, removal of dust and pollen from the air can be
achieved before it enters the conditioned space.
These units are not without their problems. For one, they are
relatively large and heavy and consume both water and gas, as well
as an electric power source for rotation of the wheels and air
handling by means of fans.
It is typical in conventional MEC units to utilize an open burner
system in the heating section to provide the heat input to the
regenerating air for drying of the L-wheel. However, this open
burner system has many serious drawbacks. Primary among these is
the possiblity that flue products will enter the incoming air. This
occurs in two ways: first, if the air pressure in the regeneration
half of the unit is greater than the pressure in the incoming half,
gas leakage onto the incoming side might occur between the baffles
and seals dividing the unit into the two halves, the incoming and
regeneration halves. The second manner in which the flue products
might enter the incoming air is due to the fact that as the L-wheel
rotates into the incoming side from the regneration side, a small
amount of gas is trapped in the actual passages through the
wheel.
A second drawback to the open burner system is that reaction can
occur between the flue products and the salts used as drying agent
desiccants in the L-wheel. Typical salts are lithium bromide or
chloride. However, the high temperatures and flue products
components could react with such salts, liberating halogen which
even in a few parts per million would not be tolerable in the
conditioned space. Further, an open flame is both difficult to
modulate and requires relatively complex ignition systems because
the burner is located in a moving air stream.
Still further, the S-wheel typically is of asbestos coated with a
wax overcoat to prevent moisture absorption or adsorption thereon.
However, the typical wax coating is highly flammable, and the
flammability of this coating requires the S- and L-wheels to be
spaced relatively far apart, thus increasing the size of the
unit.
In the case of large MEC units, for example, on the order of 3-ton
sizes used for residential air conditioning, it is difficult to
house a burner delivering the required 100,000 BTU/hr. capacity in
a reasonably sized unit.
Open-flame burners also suffer from the fact that a uniform heat
flux is very difficult to impart to the regenerating air stream
because of the changes in the air flow patterns. The primary prior
art approach to the solution of these problems has been to provide
indirect heat sources in the form of burner tubes. These are shown
typically in U. S. Pat. Nos. 3,144,901 to Meek and 3,251,402 to
Glav. Typically, these burner tubes are inverted U-shaped tubes,
one end of which is flared to receive a gas burner therein. The gas
burner is oriented so that the flame extends into the tube.
Typically, the opposite end of the tubes is either open, or holes
are drilled along the length of the tube to provide flue gas a heat
outlet. The open end of the tube or the holes provide, in coaction
with the moving air stream, a negative pressure which helps
aspirate the burner and draw the flame around the U-shape of the
tube. In addition, complex fin patterns of unequal spacings are
disposed along the tubes to compensate for non-uniform air flow.
However, in some systems the tubes are still open for exhausting
the flue products into the regenerating air stream. Thus, the
possibility still exists for flue products to enter the incoming
air and for reaction to occur between flue products and the
haologenated salts used as drying agents on the L-wheel.
Further, where such conventional indirect heaters are used, the
heat transfer is very inefficient and thermal response is quite
slow. Thus, in the case where outside conditions can change
relatively rapidly, the amount of heat required for adequate drying
of the L-wheel may increase or decrease faster than the heating
tubes can adjust to the changed requirements. Where the heat output
is required to be rapidly increased and the indirect heaters are
too slow in response, the L-wheels do not adequately dry and the
temperature of air delivered to the interior rises rapidly.
Conversely, where the heat required is lowered because outside air
is drier, the indirect sources may deliver too much heat, thus
causing breakdown of the halogenated salts, liberating noxious
bromine or chlorine, in part into the incoming air stream.
THE INVENTION
Objects
It is among the objects of our invention to provide an improved
environmental control unit having a more efficient, safer, and more
easily controllable heat transfer unit.
It is another object of this invention to provide an improved
apparatus and method for regenerating the L-wheel in an
environmental control unit.
It is still another object of our invention to provide a heat
source which overcomes the difficulty present in the prior art with
open-flame heat sources and indirect heat units.
It is another object of our invention to provide an improved
heating means for heating the regeneration air stream, which is
self-adjustable and responsive to varying conditions of the air
passing in contact therewith.
Still further and other objects of our invention will be evident
from the description, which has reference to the following
figures:
FIG. 1 is a schematic perspective view of our invention;
FIG. 2 is a plan view of the invention shown in FIG. 1; and
FIG. 3 is a view of the heating section of one embodiment of our
invention taken along the line 3--3 in FIG. 1.
SUMMARY
We provide an improved environmental control unit which employs a
bank of heat pipes in the heating section of the unit. One end of
the heat pipes extends into the regenerator heating region and
delivers heat to the air passing through the regenerative half of
the unit. The other ends of the heat pipes extend into a separately
enclosed fire box wherein there is disposed a gas burner. The
burner is in flame contact with the evaporative end of the heat
pipe. The heat evolved by the burner first melts, and then
vaporizes, a heat transfer material, such as sodium, mercury or
water contained within the sealed heat pipe. The vapor then
migrates to the condenser end of the heat pipe disposed in the
heating section of the environmental control unit. Air passing over
the condenser into the pipes extracts heat therefrom causing the
vapor of sodium, mercury or water to condense on the walls and flow
back as liquid sodium, mercury or water to the evaporative end
wherein the cycle is repeated.
The heat pipes are self-adjusting because they are responsive to
the total heat quantity required by the air. Thus, as the air
temperature drops, or the volume of air increases in a given
section, the pipe in that region becomes relatively cooler and more
sodium vapor will condense at that point. As the sodium condenses,
it returns as liquid sodium to the evaporative end of the pipe. At
the same time, more hot sodium vapor will migrate to the cold spot,
thus delivering up more latent heat of condensation as the vapor
condenses. Conversely, where the air flow is lower or the air is
warmer, less vapor will condense. Thus, the air downstream of the
heat pipe, entering the L-wheel, is relatively more uniformly
heated than with ordinary open flames or indirect heat sources. The
mercury or water-containing heat pipes operate the same way.
It should be understood that the heat pipe is a unique device, and
although not per se part of this invention, it is not to be
confused with an indirect heat source. In indirect heat sources,
there is no simple means of rapid thermal response and the indirect
heat sources are not selfregulating, as just above described with
respect to the heat pipe. Typically, heat pipes are sealed tubes
containing a material which at ordinary room temperatures is a
solid or a liquid (such as water or mercury) but which may be
heated through at least one phase change, e.g., from the liquid to
the vapor phase. The heat pipe is completely sealed and only
partially filled with the heat transfer material, so that upon
vaporizing the pipe may retain the pressure of the vapor. The
temperature of the evaporative end of the heat pipe is ordinarily
adjusted so that it is slightly above the boiling point of the heat
transfer material. Thus, the heat transfer is ordinarily that of
the change in phase from vapor to liquid at the condenser end of
the pipe, rather than the transfer of the heat capacity of the
vapor itself. Preferably, the heat transfer material has a high
latent heat of condensation to provide effective thermal transfer
to the air. Optionally, the heat pipe may have fins for control of
air flow thereover, or for efficient heating of the tube in the
evaporative end. The burner, being in its own firebox, vents the
flue products directly to the outdoors rather than into the
regenerating air stream, thus obviating the difficulties of flue
products reacting with the desiccant materials or escaping into the
incoming air stream.
DETAILED DESCRIPTION
Turning now to the figures, and particularly with reference to
FIGS. 1 and 2, MEC unit 1 is enclosed in a housing 2 which
comprises an L-wheel 3 and an S-wheel 4 laterally displaced, but
axially aligned as indicated. Baffles 20, 20' disposed
perpendicular to the central axes 21, 21' of the wheels divides the
housing into an inlet half 5 and a regenerative half 6. Outside air
is drawn into the unit 1 by means of fan 10 wherein it passes
through the input side of the L-wheel 3. The air is dried and its
temperature raised by the latent heat of absorption. The heated,
dehumidified air in inlet side 5 than passes through the S-wheel 4
where it is cooled and remains relatively dry. Thereafter, the air
passes through the inlet side evaporative pad 9, and thence through
the conditioned air inlet 7 into the room to be conditioned. The
E-pad 9 further cools the air and humidifies it to the desired
degree for use in the conditioned space.
On the regenerative half of the cycle, air from the space to be
conditioned passes through the exhaust outlet 8, through E-pad 9'
where it is further cooled and its humidity increased. The air then
passes through the S-wheel which has rotated counter-clockwise as
shown in FIG. 1. The wheel, having picked up heat from the incoming
air, is thus relatively hot and is cooled by the relatively cool,
moist air passing through the evaporative pad 9'. The cooled
S-wheel is thus regenerated for return to the incoming side of the
unit to complete its portion of the cycle. The air passing through
the S-wheel is heated. This relatively warm, moist air then passes
in contact with the condenser end 12 of the heat pipe 13 disposed
in the heating section 11 of the unit. The heat picked up from the
heat pipe raises the temperature of the air so that it is quite hot
and therefore relatively dry. This relatively dry, hot air then
passes through the moist L-wheel 3 which has rotated
counterclockwise from the inlet half of the unit to the
regenerative half. The hot air, being relatively dry, picks up more
moisture from the wheel, thus drying out the wheel for return to
the inlet side and thus completing its half of the cycle. The
exhaust air is drawn out from the regenerative half by fan 10' and
exhausted to the outdoors as very hot, very moist air.
Disposed in firebox 16 adjacent to the MEC unit housing 2 is burner
15 in flame contact with the evaporative end 14 of heat pipe 13.
The condenser end 12 and evaporative end of the heat pipe is
connected by an intermediate section which provides for the
migration of the vapor of the heat transfer material in the heat
pipe. The burner 15 is provided with fuel gas line 22, and the
firebox is provided with flue 17. As can be seen from FIG. 1, the
flue 17 does not communicate with the exhaust air in the
regenerative half of the MEC unit. In a preferred embodiment, as
shown in FIG. 2, the firebox will be disposed out-of-doors so that
the flue 17 can exhaust directly thereto. However, it should be
understood that the firebox may be integrated within the MEC unit
housing 2 so long as the burner is not exposed to the moving air
stream and the flue does not exhaust to the regenerative air stream
or the inlet side of the MEC unit.
As can be seen by comparing FIGS. 1 and 2, the evaporative end of
the heat pipes may be disposed spaced apart horizontally, while the
condenser end may be disposed vertically in the same plane, but
spaced apart from each other. Thus, the heating section of the MEC
unit can be made substantially smaller since it needs to be only
sufficiently wide to accommodate the condenser end of the heat
pipes and not the burner section. Optionally, the fuel gas line 22
may be provided with valve 23 which, via electrical connection or
line 24, is responsive to the temperature downstream of the L-wheel
on the regenerative half of the unit, as by thermocouple 25. As the
temperature is sensed by thermocouple 25, the flow of fuel to the
burner may be increased or decreased as desired in any preset
cycle. The thermocouple 25 may be replaced by a humidity sensor,
and the burner likewise controlled in relation thereto, if
desired.
Referring to FIG. 3, the L-wheel is shown disposed within housing 2
from a position upstream of the heat pipe 13 disposed in the
heating section 11. In this particular embodiment, the condenser
end of the heat pipe 12 is finned to provide for laminar air flow
thereover. Likewise, the evaporative end of the heat pipe also has
fins 18 thereon for a good thermal contact and heat transfer from
the burner 15 disposed in firebox 16. Alternatively, as shown in
FIG. 2, upstream louvers 28, pivoted on pins 29 may adjustably
regulate the air flow over the condenser ends of the heat pipes.
The fins or louvers 28 may be adjusted by link 32 actuated by
solenoid or other actuating means 33 in response to downstream
conditions via line 31, or in response to the gas flow to the
burner via line 30.
In addition to, or instead of, the fins, the baffles 19 may be
disposed to cover a portion of the regenerative half of the L-wheel
for control of the air flow or air amount. It should be understood
that while baffling 20, 20' divides the L-wheel in half, the input
or regeneration "half" of the wheel need not be a 180.degree.
section of the wheel and may be more or less than that amount. In
addition, as seen in FIG. 3, a portion 19' of the baffles may
extend into the input side to provide for proper exhausting of the
L-wheel as it rotates into the input side. In addition, this will
prevent the very hottest portion of the L-wheel from being used,
permitting it to be temperature equilibrated before use in drying
the incoming ambient air.
In a MEC unit, the temperature of the regeneration air should be as
high as is necessary to produce the required degree of dryness in
the L-wheel, while at the same time it should not exceed
temperatures that will injure the wheel. This is true regardless of
the moisture load being handled by the drying wheel. At the same
time, in order to conserve heat, the temperature of air leaving one
section of the wheel should not reach its upper limit until that
section of the wheel approaches the very end of the regeneration
section as it rotates into the inlet side of the unit. This
combination of characteristics requires that a regeneration heating
means provide a stream of uniformly heated gases controlled at a
constant temperature measured before entering the wheel, and
controlled in volume in response to temperature sensed on the
outlet of the wheel section close to where the regeneration section
ends and the purge section, delimited by baffle 19' (in FIG. 3),
begins. The air used for regeneration is also that used to provide
some of the sensible heat removal from the dried air. With this
usage, a constant volume is necessary. Therefore, in regulating
regeneration, any throttling of air to control the L-wheel
temperature must be accompanied by the opening of the bypass to
provide a constant total air flow. For control of the air volume,
butterfly valve 26, rotatable on pivot 27, is provided to permit
air to bypass the L-wheel. This bypass and valve assembly may be in
a hollow central hub of the wheel shown as 34 in FIG. 3. BY
temperature sensing mechanism analogous to that shown for control
of valve 23 in association with the burner 15 and fuel line 22, the
opening of the valve can be adjusted responsive to a thermocouple
(not shown) disposed on the outlet side of the L-wheel near the
dividing line between the regeneration section and the purge
section, delimited by baffle 19'.
One advantage of our invention lies in the fact that the heat pipe
may be arranged to absorb the heat from a conventional atmospheric
gas burner without particular concern as to the uniformity of heat
distribution over the entire evaporative end of the heat pipe. In
addition, the use of an external atmospheric burner permits the use
of a simple ignition system which will be less likely to fail than
the complex ignition systems presently required to ignite a gas
burner located in the moving air stream. The heat dissipating, or
condenser, end 12 of the heat pipe 13 has a uniform temperature due
to the uniform pressure of the vapor in the tube. The tube may be
configured, as by bending as seen in FIG. 3, so that it will impart
uniform temperature to the flowing air. The creation of hot spots
or of general overheating is greatly reduced due to the
self-regulating nature of the condensation which occurs within the
tube. Temperatures below the drying wheel can be controlled by a
simple thermostat. The volume of regenerating air and consequent
exit temperature from the wheel can be regulated by the temperature
controlled bypass 26. Pressure differentials between the inlet half
5 and the regenerative half 6 are no longer critical since there is
no danger of contamination of room air by flue gases. Likewise,
there is no danger of contaminating or degrading the desiccant
material since the condenser end of the heat pipe is not a source
of flue gas exhausting therefrom. Likewise, there is no open flame
or direct radiation hazard to the S-wheel, thus preventing flame
hazards and providing for a shortening of the distance between the
L- and S-wheels.
These general principles are further shown by reference to the
following specific example which is meant to be illustrative and
not limiting of the invention.
SPECIFIC EXAMPLE
A 2-ton MEC unit is provided with a heat pipe having a condenser
end length of 30 inches in the configuration shown in FIG. 3.
Within the regenerative section, the effective outside surface
temperature of the heat pipe is 1200.degree. F, which provides an
average temperature of air leaving the heating section of
350.degree. F. This is an increase from the average temperature of
the air leaving the S-wheel of 180.degree. F for an air flow to the
heating section and heat pipes disposed therein of 2682 lb./hr. The
required heat input for the 2-ton unit is 80,000 BTU/hr., resulting
in a log mean .DELTA.t of 910.degree. R. The hA value is 88 BTU/hr.
-.degree. F. For laminar flow with low pressure drop, the h value
would be 30 BTU/hr.- ft..sup.2 -.degree. F. The area required would
thus be approximately 3 square feet. The 30 inch length heat pipe
in the condensing section provides 7.9 sq. ft. of primary area
which is more than twice required.
The heat conductive material in the heat pipe is sodium, which has
a designed thermal power output of 185 BTU/hr.-in.sup.2. For the
required heat input of 80,000 BTU/hr., 433 sq. in. of primary area
is required. This is easily satisfied by the 7.9 sq. ft. of primary
area which is 1140 sq. in. Thus, all conditions of the MEC unit are
met without overloading the heat pipe.
It should be understood that modifications and variations in the
specific embodiments of our invention described above can be made
without departing from the spirit thereof.
* * * * *