Apparatus for collecting and transporting heat energy

The invention is an apparatus for collecting and transporting thermal energy as vaporized fluid. The vapor will flow from a heat absorption chamber and through a conduit to a point of use where it is condensed. The heat absorption chamber includes a sump in its lower portion to hold a puddle of fluid. A heat source directed against the chamber vaporizes the fluid therewithin and a replacement fluid supply connects with the chamber to maintain the level of the puddle during vaporization. The chamber of the preferred embodiment of the invention is an elongated heat absorption pipe mounted horizontally to maintain the puddle at the lower portion of the pipe. The heat absorption pipe is mounted in a solar collector to receive concentrated solar energy as from a reflector system.

The present invention relates to the collection and transfer of thermal 
energy, and more particularly to collectors of solar energy which reflect 
and concentrate the sun's rays against a heat absorption device such as a 
heat pipe. 
The present invention is a development from and an improvement over U.S. 
Pat. No. 3,875,926 issued Apr. 8, 1975 to Matthew William Frank, 
co-inventor in the present application. That patent discloses a solar 
energy collection system wherein the collector reflects concentrated solar 
energy against a section of a conduit similar to a heat pipe, with the 
lower end of the conduit being submerged in a fluid source, normally 
water, and with an internal wick to flow the fluid by capillary action to 
the pipe section being heated by the concentrated solar energy. The vapor 
generated in this heated section of the pipe flows through the pipe to the 
point of use such as at a condensor and heat exchanger arrangement. 
It was contemplated that the primary use for that solar energy collection 
system was for lifting water from a supply bay to move the vapor above the 
bay as to a condensor. Such a system was proposed for applying solar heat 
to buildings such as houses, but it was found that significant 
modifications and rearrangements of the components would be desirable 
although the generic concept of externally supplying water to a heat pipe, 
heated by concentrated solar energy to vaporize the water and move the 
vapor to a point of use would not be changed. In the first place, a 
reservoir or bay was necessarily replaced by a water line to bring water 
to the section of pipe being heated since the water supply would normally 
be remote from the solar energy source. To meet the energy demand for 
different types and sizes of buildings, it was found undesirable to custom 
design each system but more expedient to provide a selected number of unit 
collector modules which could be combined into a common system. Such a 
system had to be versatile for it would be used on various types of 
buildings and structures. The system could be installed upon a flat roof, 
an inclined roof or even a vertical wall. It also follows that there is a 
need to devise and to develop improved and simplified piping systems for 
the water supply and vapor transport lines which can be used with any of 
these different arrangements of unit collector modules. 
With the foregoing and other considerations in view, the present invention 
was conceived and developed and comprises, in essence, one or more unit 
collector modules arranged in conjunction with a water supply line and a 
vapor transport conduit from the unit collector modules. Each unit 
collector module, hereinafter referred to as "collector," provides for a 
heat absorption pipe which receives the concentrated solar energy as from 
a reflector. The heat absorption pipe has a diameter sufficient to provide 
a sump of water at its lower portion throughout the reach of the pipe. 
When heated, this water will evaporate into its upper portion of the pipe. 
Preferably, a circumferential capillary wick is located in this heat 
absorption pipe to lift the water as a thin film to the upper portion of 
the pipe. The water supply line includes a trap arrangement to maintain a 
proper water level in the lower portion of the horizontal heat absorption 
pipe, that is, in the sump. The vapor transport conduit connects with the 
upper portion of the heat absorption pipe of each collector in the system 
and extends to a suitable heat exchanger. The water supply line and the 
vapor transport conduit are strategically cross-connected to maintain a 
suitable pressure balance throughout the system to assure a proper 
continuous operation as will be exemplified in the detailed description 
hereinafter set forth. 
It follows that an object of the present invention is to provide a novel 
and improved energy collection system wherein a plurality of collectors 
are integrated to function together in an effective, efficient manner to 
vaporize water provided from a supply line and to transport this vapor 
through a conduit to a point of use where the vapor is condensed and the 
latent heat of vaporization is recovered. 
Another object of the invention is to provde in such an energy collection 
system, a simple, effective piping arrangement to supply a controlled flow 
of water to the collectors, at a rate and in such a manner as to replace 
water as it is vaporized. 
Another object of the invention is to provide in such an energy collection 
system, a simple piping arrangement which includes a water supply line to 
the collectors and a vapor transport conduit which is capable of 
controlling the water and vapor movements through the system in a 
recirculating, regulated manner without disruption as by an occurrence of 
unbalanced pressures or the like. 
Another object of the invention is to provide a novel and improved energy 
collection system which combines a plurality of unit collector modules to 
produce a system having any specified capacity. 
Another object of the invention is a simple, reliable method of flushing 
deposited minerals and preventing scale in the vaporizer section of open 
heat pipes which are being supplied with fluids containing dissolved 
impurities. 
Another object of the invention is to provide a novel and improved energy 
collection system having a combined plurality of unit collector modules 
which can be effectively mounted in several different ways as upon flat, 
sloping and vertical surfaces. 
Other objects of the invention are to provide in such an energy collection 
system, arrangements and components which are effective, efficient, 
reliable, economical, rugged and durable.

Referring more particularly to the drawing, a system using the improved 
collectors C is diagrammatically illustrated at FIG. 1. Four collectors C 
are illustrated as being arranged in sequence. A water supply line L and a 
vapor transport conduit V connects with these collectors as hereinafter 
described. The collectors may be mounted upon various structures or 
supports and will ordinarily be mounted upon the roof or wall of a 
building. Thus, the collectors will be above the water supply source and 
water to the collectors C must be provided from a supply tank 20 through a 
pump 21 in the line L. The waterflow is continuous during operation and 
the line L includes a circulation return 22 to the tank 20. The quantity 
of water used by the collectors is not large and the flow will only 
partially fill the line L at the reach where the collectors tap the line 
as hereinafter described. Thus, the pump is preferably a constant volume 
type, such as a gear pump. If a centrifugal pump is used, it will be 
necessary to provide a regulating valve 23 in the line L to control the 
amount of water flowing through the line. Other features are provided in 
the line L such as a drain 24 to empty the lines if necessary. Also, 
manometers and vents and bypass lines regulate the air pressure in the 
line L especially where the water supply line L connects with the 
collectors as hereinafter described in detail. 
The vapor transport conduit V extends from connections at the collectors C 
to a heat exchanger 25 which may be coils within a hot water storage tank 
26. The vapor is condensed in the heat exchanger 25 where its' latent heat 
energy is released and a return line 27 returns the condensate produced by 
the condensed vapor to the supply tank 20. The heat storage tank 26 will 
normally be full of water which is heated by the heat exchanger 25. The 
hot water will be transported through a service line 28 to sinks, 
appliances or the like where the hot water is used. A replacement line 29 
connecting with the bottom of the tank 26 will replace the transported 
water with fresh water, to the storage tank 26 as water is drawn from the 
tank 26 through the service line 28. A bypass line 30 may be provided 
between the hot water service line 28 and the replacement line 29 with a 
thermal mixing valve 31 at the junction with service line 28 and line 30 
to limit the temperature of hot water flowing in the service line. 
A supply line 32 is shown as being connected with the replacement line 29 
to extend into the water supply tank 20 and a float valve control 33 to 
keep a minimum amount of water in the supply tank 20. An overflow 34 
controls the maximum amount of water which will be in the supply tank 20 
and also functions as an air vent. 
A heat sensor 35 is placed at a collector C to restrict the operation of 
the pump to times when there is sufficient sunlight to start vaporizing 
the water in the collector. An electrical immersion heater and a 
thermostat 36 in the hot water storage tank may be also provided to allow 
backup heating of the hot water when there is not sufficient sunlight to 
meet the energy demand. Electrical leads from the heat sensor 35 are 
connected to a control box 37 which includes suitable relays and other 
components to operate the pump 21 and permit flow from the storage tank 
20. 
An air vent line 38 is connected to the several collectors to prevent a 
buildup of air pressure within the optical cavity of these units, since 
the air volume will vary as the collectors are heated and cooled. A filter 
39 is placed at the end of this line to keep moisture and dust out of the 
interior of the modular units. 
It is to be understood that the system, shown at FIG. 1 and the components 
of the system hereinabove described, is illustrative of one preferred 
arrangement to connect with a group of solar energy collectors C and that 
other arrangements are possible using similar components to those 
described. 
As illustrative of another system configuration, the water supply from line 
L would be provided directly from an area water main and, diverted to the 
line L, as at bypass 61 which includes a flow regulator 62. In this case, 
the water main pressure lifts the water to the collectors. The water pump 
21, controller 37, thermostat 35, flow regulator 23, drain 24, float valve 
33 and make up water line 32 are then unnecessary and line 22 terminates 
at a drain line 63. The total solar system then operates with no need for 
electrical power or electrical devices and provides a small quantity of 
distilled water to the tank 60 as a byproduct of system operation. This 
distilled water can be removed from holding tank 20 and used for other 
purposes. 
The basic structure which incorporates the present invention will include 
the water supply line L and a pump 21 (or main supply 61) to provide a 
measured flow of water through the line to and past the collectors C. The 
basic structure will also include the vapor transport conduit V which is 
connected with the collectors to extend to a heat exchanger or any other 
device making use of the vapor. 
A group of unit collectors C may be mounted upon a roof, wall or other 
structure in a number of different ways, providing however, that each is 
essentially horizontal as hereinafter set forth. The mounting will, of 
course, be otherwise oriented so that they will receive a maximum exposure 
to sunlight. 
FIG. 2 illustrates one method of mounting two collectors C in a side by 
side alignment with the water circulating line L, the vapor transport 
conduit V and the air vent 38 being placed between the collectors. It is 
to be noted that this side by side arrangement may be further extended by 
joining additional collectors together, end to end. This is not shown 
because the connecting of one collector with another is essentially the 
same as increasing the overall length of a collector. The collectors C may 
be mounted in a parallel sequence upon a flat roof, a sloping roof or even 
a vertical wall as diagrammatically illustrated at FIGS. 3, 4 and 5. In 
each instance, it is to be noted that each collector will be inclined at a 
selected, optimum position to best receive the sun's rays, for as long a 
period during the day as possible. The different modes of mounting and 
aligning solar energy collectors is well known to the art and need not be 
discussed further. 
The general construction of a collector C is illustrated at FIGS. 6 and 7 
and it is to be noted that the water supply line L and the vapor transport 
conduit V will be located comparatively close to an end of the collector C 
and preferably, the same end. For efficient heat transport and freeze 
protection, both the line L and conduit V and their leads to the collector 
will be encased in an insulating pipe 40 having a diameter sufficient to 
prevent any significant heat loss. The air vent 38 may also be enclosed in 
this pipe 40. 
The collector itself is an elongated rectangular box, built in the general 
form of a half cylinder, with a glass covered opening, closed ends 41 and 
a longitudinally extended cylindrical undersurface 42. This undersurface 
42 is formed as an outer insulation layer to minimize heat losses within 
the collector. The inside of this undersurface is a cylindrical reflector 
43 to focus the solar energy against a longitudinally extended heat 
absorption pipe H within the collector. Such a reflector may be parabolic 
in form and the heat absorption pipe H may be at the focal point thereof. 
Practically, however, the reflector may be circular in form and regardless 
of the form, the focal point will shift from one position to another as 
the sun changes its position. Thus, to effectively receive and absorb all 
of the sun's rays from the reflector regardless of shifting of the focal 
point, the heat absorption pipe H is comparatively large in diameter and 
if necessary, longitudinal fins may be mounted on the heat absorption pipe 
in such a manner as to most effectively intercept all of the sun's rays 
falling into the collector and reflected from the mirror regardless of the 
sun's position. Various systems have been designed for this purpose and 
thus, the arrangement need not be described further in detail. In fact, it 
is to be noted that the invention herein disclosed can be effectively used 
with other sources of heat than solar energy. What is essential insofar as 
the present invention is concerned, is the provision of radiant or thermal 
energy to heat the heat absorption pipe H to produce a temperature 
sufficient to vaporize water, or any other selected fluid within the 
absorption pipe H. 
To complete the collector C, suitable brackets 44 are provided at the outer 
portion of the body to permit it to be mounted in any manner desired and 
the top opening of the box will be closed by one, or preferably, two 
layers of glass or plastic 45 to prevent heat loss by exterior currents of 
air striking the absorption heat pipe H. 
The horizontally disposed heat absorption pipe H has a sufficient external 
diameter, or is otherwise proportioned to intercept the sun's rays 
entering the collector as mentioned. The heat absorption pipe has an 
internal diameter sufficient to provide for an elongated puddle of water W 
in the lower sump portion of the pipe H and an elongated vaporizing 
chamber K in the upper portion of the pipe as best shown at FIGS. 9 and 
10. This diameter should be large enough to permit small errors in 
leveling which may occur when a collector is installed on a roof or a 
wall. If not level, or nearly so, the puddle of water W will not be at one 
end of the pipe and the other end will be filled with water. 
For a collector having a length of approximately four feet, the inside 
diameter of the heat absorption pipe H is preferably in the range of one 
to two inches. When the collector operates, the reflector will heat the 
pipe H to a temperature sufficient to vaporize the water in the lower 
portion of the pipe. Preferably, a wick 46 of a suitable synthetic or 
natural fiber may be fitted into the heat absorption pipe H to lift water 
by capillary action to the surface of the pipe at the vaporizing section K 
above the puddle W. The wick 46 may be formed as a flat strip formed as 
tubular member which extends into the pipe H to engage the inner walls 
thereof. 
As illustrated, a water inlet tube 47 and a vapor outlet tube 48 are 
provided at one end of the pipe H. The water inlet tube connects at the 
bottom of the pipe H where the puddle W forms and the vapor outlet tube 48 
connects at the top of the pipe H in the chamber K. Both tubes at one end 
of the pipe H is the preferred arrangement but it is to be understood that 
the water inlet tube 47 could be at one end of the pipe H and the vapor 
outlet tube 48 at the opposite end without changing the operation of the 
collector. Water must flow into the pipe H to replace water as evaporation 
occurs and to keep the elongated puddle W full. For collectors of normal 
proportions this water flow is small and may be in the range of one to 
five liters per hour during the day, but it will be even less in the 
morning and evening of a day. 
To provide a reliable infeed for this small varying demand of water, a 
continuous flow of water is maintained in the supply line L and whatever 
is needed by the pipe H will flow into the inlet tube 47. The remainder of 
the flow in the supply line L, will continue to the next collector, or 
collectors, in line and thence to the return 22 (or to drain line 58). 
This flow through the inlet tube 47 and into the pipe H is basically, a 
simple gravity flow. To accomplish this, the supply line L at the 
collector, where the connection with tube 47 is located, is at the level 
of the puddle W and the capacity of the pump 21 (or flow regulator 62) is 
such that there is only sufficient water flowing through the supply line L 
to keep it about half full. For an effective, disturbance-free flow 
communication between the supply line L and the pipe H, and to prevent 
vapor flow out of pipe H to supply line L, the water inlet tube includes a 
trap 49, an inverted siphon, having a downturn 50 connecting with the 
water inlet tube 47 and a riser 51 connecting with the bottom of the 
supply line L. 
The flow in the water supply line L will normally be in the nature of an 
open channel flow, that is, with a free surface in the upper portion of 
this line as mentioned. For the quantities of water involved, it was found 
that the diameter of the pipe could be 1/2 to 3/4 inches for most 
installations to permit the desired open channel flow and to supply water 
to the puddle W in the pipe H of each collector. In this manner the water 
level at each trap 49 adjacent to a collector C is always properly 
controlled. 
It follows that the reach of the water supply L past the collectors must be 
downsloped and the reach will commence at a high point 52, where the flow 
starts. The slope of the supply line L will necessarily correspond to the 
arrangement of the collectors on a roof, and whenever these collectors are 
set upon a flat roof, it is contemplated that they will be arranged with a 
small slope, as by adjusting the collector mounts 44. Thus, the first 
collector to be serviced will be higher than the others. Even though the 
slope of the line L between the collectors will be comparatively small, 
and nearly flat, the desired open-channel type of flow in the reach of 
line L is easy to maintain. Where the collectors are set upon an inclined 
roof, the slope will be much steeper, but it was found that the system 
would work just as well and the open channel type of flow in the line L 
could be easily maintained. This sloping line L is shown at FIGS. 14 and 
15. If desired, the portion of the line L approaching a collector may 
level off as at 53, then continue at a steeper slope a short distance 
beyond the trap 49 connecting with the collector. Finally, after the line 
L passes the last collector, it will constitute the return 22 and extend 
to the supply tank 20. There will be provided somewhere in the return 
reach 22 a trap 54, or manometer, with a vent 55 at the downstream side of 
the trap to provide for any pressure or vacuum release in the downstream 
side of the manometer 54 and especially to prevent any siphoning of the 
liquid out of the manometer. The manometer 54 is placed in the line in 
order that the liquid may freely flow through the line but the air also in 
line 53 will be trapped. This trapped air in line 53 is used to slightly 
pressure the water supply in the line in order to prevent the operating 
vapor pressure in pipe H from depressing the level of puddle W. The 
manometer can be located anywhere in the line and ordinarily, it will be 
placed inside the building where the chance for freezing of water in the 
trap is minimized. 
The vapor outlet tube 48 from the top of the heat pipe may turn upwardly as 
a riser 56 to connect with the vapor transport conduit V, with the use of 
the riser 56 depending upon the location of the outlet tube 48 with 
respect to transport conduit V. 
It is desired that a pressure balance be maintained between the water 
supply line and the vapor transport conduit V. This pressure balance is 
needed when the system starts up and air is exhausted from the vapor line 
and during operation of the system to prevent any positive vapor pressure 
in pipe H from depressing the level of puddle W. Accordingly, a pressure 
equalization bypass line 57 is connected to the vapor tube 58 and to the 
top of the water supply line L at one or more points in the system. 
This bypass line drops from the vapor tube 48 above the water line L and it 
is desirable to keep this line full of air rather than having vapor flow 
into the upper position of the water supply line L. A restrictive 
diaphragm 58 may be located in the bypass line adjacent to the connection 
with the vapor outlet tube. There is a small orifice 59 in this diaphragm 
to minimize the flow therethrough, and yet provide for balanced pressures 
in the several lines. Since the environment will be water vapor, where 
some condensation can occur, it was undesirable to permit drops of water 
to seal off this orifice and such can be accomplished by a simple fiber 
wick or thread 60 in the orifice as illustrated. 
Operation of the system is simple and essentially automatic. To initiate 
operation, as in the morning, there is no water in the supply line L 
except possibly at the traps 49 and 54. The vapor transport line is full 
of air. As soon as the sun commences to heat the absorption pipe H, the 
sensor 35 initiates flow of water through the water supply line L to 
maintain water puddles W in the sump portion of the pipe H. As vapor is 
generated, air is discharged from the vapor transport line, except where 
it is trapped for thermal isolation purposes, such as in the pressure 
equalization bypass 57. As the vapor enters the heat exchanger it is 
condensed to water, releasing its latent heat of vaporization. The 
condensate returns through line 27, to the supply tank 20. As water is 
heated in the storage tank 26, it may be used for various purposes. The 
entire system is balanced at all times with a maximum efficiency of 
operation. 
In applications in which the water supply is provided by area mains, the 
concentration of dissolved solids will be increased in the collector heat 
absorption pipes H as the water is vaporized. If some means is not 
provided to remove these dissolved solids, the concentration will increase 
until they precipitate to form scale in the pipe H, to reduce the thermal 
efficiency of the collector and eventually block the flow of water into 
the pipe H. The water in the heat absorption pipe H can be periodically 
flushed to remove the dissolved solids. However, a more simple procedure 
is possible by permitting a continuous flow of water through the line L 
both during operating and non-operating periods. Then there is at all 
times a direct coupling of the water supply in line L and the water puddle 
in the heat absorption pipe, as through the water inlet tube 47. Since 
most solubles in water form mutually repellant ions, the higher 
concentration of solubles in the heat absorption pipe will hasten the 
diffusion of the solubles out of the heat pipe and into flowing water in 
the supply line L. 
We have now described our invention in considerable detail. However, it is 
obvious that others skilled in the art can build and devise alternate and 
equivalent constructions which are nevertheless within the spirit and 
scope of our invention. Hence we desire that our protection be limited not 
by the constructions illustrated and described, but only by the proper 
scope of the appended claims.