TECHNICAL FIELD
[0001] The present invention relates to the field of radiant energy or heat collector assemblies.
More particularly, it refers to methods and systems for recovering or capturing heat
in the form of radiant energy and using the recovered energy for further purposes
such as heating of buildings, electricity production or steam generation. The heat
capturing device can be applied in industries such as in steel mills, metallurgy,
furnaces or glass production or any other energy intensive industry with high radiant
emissions.
STATE OF THE ART
[0002] The European patent application
EP2403668 (A2) discloses a heat retrieving system in which heat is retrieved via conduction and
convection. This patent application uses the transportation rollers as heat exchangers.
The patent application
DE3019714 (A1) discloses a heat collection arrangement comprising water containing tubes. The prior
art is silent on heat collection devices especially configured for capturing heat
transferred by radiation. It is therefore required a technical arrangement recovering
radiant energy or heat from an object or objects being at temperature higher than
500° C.
[0003] There is the general belief that optimal dimensions of the heat capturing device
collecting energy tend to be minimum. However, the present application proves it is
not necessarily the case because the dimensions or the size of a device collecting
more energy than the known devices or systems depend on several factors. The present
application achieves the unexpected technical effect of finding which are the dimensions
of the heat capturing device that enable collecting more energy from an object at
high temperature than the systems or devices in the prior art.
DESCRIPTION OF THE INVENTION
[0004] The present application overcomes the drawbacks of the prior art and allows higher
energy or heat retrieval of the heat or energy radiated by an object or group of objects.
[0005] Claim 1 discloses the scope of the present realization. Preferred realizations are
disclosed in claims 2-16. The described heat capturing device comprises an upper side
and lateral sides connected to the upper side, said connected sides defining an energy
capturing space. The device further comprises an energy insulating layer, an intermediate
energy reflecting layer and an inner energy capturing layer capturing energy from
at least a radiation emitting object (hereinafter referred to as "object") located
at least partly in the energy capturing space. The inner energy capturing layer comprises
at least one material containing structure. The material may be a heat transfer fluid
(hereinafter referred to as fluid), for example a liquid such as silicon based thermal
oil, for capturing energy. The material containing structure may be at least a tube
having preferably a circular cross-section. The dimensions of the inner energy capturing
layer (width and height of the inner energy capturing layer), and thus, the dimensions
of the heat capturing device as a whole including the intermediate energy reflecting
layer, the energy insulating layer and the energy capturing space defined, are based,
at least, on the dimensions of the at least an object in the energy capturing space
and based on at least a further parameter. Said further parameter may be at least
one of: at least one further parameter of said at least an object or at least one
parameter of the inner energy capturing layer or at least one parameter of the energy
capturing space or a combination of said further parameters. Said further parameter
or parameters of the inner energy capturing layer may be intrinsic parameters of the
surface of the inner energy capturing layer defining the energy capturing space.
[0006] In the heat capturing device, the energy insulating layer may entirely cover the
intermediate energy reflecting layer, and the intermediate energy reflecting layer
may entirely cover the inner energy capturing layer.
[0007] A further plate or plates may be located at the entrance or exit of the energy capturing
space for better retaining and/or reflecting the radiant heat or energy of the object
or objects inside the energy capturing space. The plate or plates located at the entrance
and/or exit of the energy capturing space may be made of a heat or energy reflecting
material. The energy insulating layer may be covered with an outer casing or outer
cover for protecting and encapsulating the heat capturing device. The described layers
may be different layers which may be separated from each other. The heat capturing
device may be connected to a bottom layer or plate or surface made of either reflecting
or insulating heat material.
[0008] The parameter or parameters defining the width and the height of the inner energy
capturing layer may be, for example, at least one of: the convection coefficient of
the air inside the energy capturing space, the emissivity and absorptivity of at least
one of the surfaces of the object, the emissivity and absorptivity of at least one
of the surfaces of the inner energy capturing layer or a combination of said parameters.
The emissivity and absorptivity of a surface are magnitudes indicating its effectiveness
in emitting or absorbing (respectively) thermal radiation. Quantitatively, they are
described as the ratio between the thermal radiation emitted/absorbed by a surface
compared to the radiation emitted/absorbed by an ideal black body at the same temperature
(which is maximum).
[0009] The parameter or parameters defining the height and width of the heat capturing device
may be based on some intrinsic properties of the objects which are to be received
in the energy capturing space or transported through the energy capturing space. The
objects can be for example a slab, billet or beam resulting from a production process
such as a metallurgic production process or preferably a piece of hot glass (e.g.
bottle shaped glass) produced by a glass production factory. Said production processes
may serially produce objects such as slabs or hot pieces of glass, and some properties
of said serially produced objects or pieces are known. The objects may be solid or
partly solid objects. The objects are preferably at a temperature higher than 500°
C. The fact that the characteristics of the production of the object or objects are
known in advance, means that the properties of the product after the production process
and before entering the energy capturing space are known. The fact that the heat capturing
device of the present application allows a modular construction permits the customization
of the size or dimensions of the heat capturing device or tailoring the size of the
heat capturing device according to the properties of the objects, thus allowing to
capture the radiated heat from the objects when the objects are partly or completely
in the energy capturing space or even slightly outside the energy capturing space.
The width and the height of the inner energy capturing layer can be selected based
on said properties of the object, which implies that the width and height of the heat
capturing device as a whole is selected based on at least the properties of the objects
or parameters taking into consideration the properties of the object. The heat capturing
device and its size may be configured before the production process of the objects
start. The modularity of the heat capturing device permits the heat capturing device
to be assembled and/or remove parts of the heat capturing device easily.
[0010] The inner energy capturing layer, for example a tube bundle, may cover an inner surface
of a tunnel-shaped surface defined by the energy capturing space or may have a tunnel-shaped
arrangement, and the diameter of the tubes of the bundle may be the same or similar.
The dimensions or the size of the tube bundle are defined in such a way that the heat
captured by the heat capturing device is maximized, mainly the heat transmitted by
radiation. The arrangement of the tube bundle may be perpendicular or parallel to
the direction of movement of the objects being transported (e.g. objects entering,
leaving or being transported through the energy capturing space or objects remaining
for some time in the energy capturing space). Heat losses due to convection and radiation
of the surfaces of the heat capturing device (e.g. the tubes of the bundle) are minimized
using insulating materials. The heat capturing device, and more particularly the inner
energy capturing layer may be designed to operate with the fluid flowing through the
tubes at a medium fluid temperature around 350° C. In some examples and depending
on the temperature of the objects from which radiated heat is going to be captured,
the fluid may be at a temperature that satisfies a heat demand with temperatures between
600 and 140° C. In some other examples, the fluid may be at a temperature that satisfies
a heat demand with temperatures between 140 and 40° C.
[0011] The tubes of the bundle may be separated from each other. More preferably, the distance
between the center of two consecutive tubes may be between 1,25 and 2 times the external
diameter of a tube of the bundle.
[0012] The bundle of tubes may be connected, e.g. welded, to at least two headers. The headers
may be to feed the fluid to the inner energy capturing layer with the fluid being
at a first temperature, to distribute the fluid through the inner energy capturing
layer such the fluid may increase its temperature from the first temperature to a
second temperature by absorbing heat from the object or objects, and to remove the
fluid from the inner energy capturing layer with the fluid at the second temperature.
In some examples, the second temperature may be higher than the first temperature.
The headers may transport the fluid from/to a fluid storage or to any other device
that may reuse the recovered energy for similar or different purposes such as heating
of buildings, electricity production or steam generation.
[0013] The external surface of the bundle of tubes, i.e., the surface of the bundle of tubes
facing the object, may be covered with a high absorptivity coating or with a high
absorptivity paint. The paint may have as much absorptivity as possible in near and
mid-infrared spectrum, and at least higher than the corresponding values of the base
material of the inner capturing layer. For example, the paint may have an absorptivity
around 0,97 for a wavelength between 2-3 microns.
[0014] The intermediate energy reflecting layer may have a flat structure such as a plate
or a corrugated shaped structure or surface or layer behind the bundle of tubes. The
corrugated shaped structure may be a sinus shaped surface or sinus shaped structure.
The convex part of the corrugated shaped structure is located in correspondence with
at least one of the tubes of the bundle and the concave part of the corrugated shaped
structure is located in correspondence with at least one of the separations between
the tubes. The corrugated or wavy or sinus shaped structure is designed to better
focus the reflected heat towards the rear part of the tubes for allowing better heat
or energy absorption of the reflected heat, thus allowing an enhanced heat exchange
with the rear part of the tubes.
[0015] The heat capturing device may comprise an energy insulating layer surrounding the
intermediate energy reflecting layer. The energy insulating layer may be made of ceramic
fiber. The insulating layer may be a separate layer from the other layers.
[0016] The heat capturing device may further comprise an outer casing covering the energy
insulating layer. The outer casing, that may be made of metal, contains and protects
the heat capturing device.
[0017] The heat capturing device may comprise one or several sensors. The sensors may be
of the same type or may be a combination of different types of sensors. The sensors
may be: one or more sensors for measuring the temperature of the object or objects,
one or more sensors for measuring the temperature of the energy capturing space, one
or more sensors for measuring the temperature inside the tubes or the temperature
of the fluid within the tubes, one or more sensors for detecting the object either
entering into, or exiting out of or remaining in the energy capturing space or any
combination of said sensors. The sensors may be connected to control means, such as
a controller or processor or group of processors for processing the information received
from the sensors. The control means may process the data received form the sensors
and may issue instructions or control data based on the sensed data as provided by
one or more of said sensors, based on the processed data or based in a combination
of the data as received and the data after being processed.
[0018] The heat capturing device may comprise transport means for moving the object or objects
relative to the energy capturing space. The transport means may be managed by control
means, the control means configured to control the transport of the object from or
to the energy capturing space. The heat capturing device automatically transports
the object to or from the energy capturing space based on a certain temperature captured
by at least one or more sensors exceeding or being below a predetermined threshold.
Said threshold may define a temperature threshold. The transport means may transport
the object through the energy capturing space or may leave the object in the energy
capturing space for a predetermined time interval so that the inner energy capturing
layer captures heat from the object. The transport means transport the object or objects
through the energy capturing space in case the tunnel-shaped heat capturing device
or tunnel-shaped inner energy capturing layer is open on both sides, that means no
plate or door is placed at the entry and exit of the tunnel-shaped heat capturing
device. In case a plate or door is located at the exit of the tunnel-shaped heat capturing
device, the transport means use the open entry for entering and removing the object
or objects to/from the energy capturing space.
[0019] The device may comprise further control means, wherein the control means are configured
for controlling the quantity of fluid and/or the speed of the fluid circulating in
the bundle of tubes, wherein the control means automatically control said quantity
and/or speed of fluid based on the data captured by at least one of the sensors. The
control means may process the data received from the sensors and based on said processing,
the control means may issue instructions or control data. The instructions may control
the transport means such as its speed, start and stop functions, may control the quantity
of fluid circulating in the bundle of tubes, may control the quantity of fluid in
the headers and may control the speed of fluid circulating in the tubes or in the
bundle of tubes. The transport means are preferably controlled for transporting the
object or objects such that the objects or objects are symmetrically placed or located
inside the energy capturing space or symmetrically placed or located while being transported
through the energy capturing space. The control means may control the transport means
and the speed of transport of the object or objects entering or leaving the energy
capturing space. This may be useful in cases in which the object or objects are transported
through the energy capturing space. Moreover, the control means may control the time
period an object or objects remain the energy capturing space and it can be implemented
by the control means controlling the transport means for stopping and starting the
transport means.
[0020] The instructions of the control means may control the transport means and all devices
regulating the flow and/or temperature of fluid in the tubes or headers.
[0021] The distance of the respective lateral sides of the object to the respective corresponding
closest surface or sides of the inner energy capturing layer (e.g. bundle of tubes)
is preferably the same, or equal or almost the same, while the object (or objects)
is in the energy capturing space.
[0022] A method for capturing energy as indicated by the heat capturing device may be implemented.
[0023] The heat captured by the inner energy capturing layer, and more particularly by bundle
of tubes, may be defined as follows:
[0024] Wherein the nomenclature is the following:
Fij View factor from surface "i" to surface "j" (according to figure 4).
Ai Area of the different surfaces.
Ti Temperature of the different surfaces.
εi Emissivity of the different surfaces.
αi Absorptivity of the different surfaces.
σ Stefan-Boltzman constant 5,67.10-8 W/m2K4.
hconv Convection coefficient of the air inside the energy capturing space (tunnel).
Subscripts:
[0025]
- 1 Object.
- 2 Inner energy capturing layer or heat capturing device.
- 3 Surface that closes the energy capturing space.
[0026] A heat capturing system is further described. Said heat capturing system comprises
a heat capturing device as previously described and at least one object located at
least partly in the energy capturing space. In such system, the heat capturing device
is configured to capture heat from the at least one object that is inserted into the
energy capturing space defined by the upper side and lateral sides connected to the
upper side of the heat capturing device. The at least one object is cooled by capturing
the heat irradiated from the object by the inner energy capturing layer of the heat
capturing device.
[0027] Additional advantages and features of the invention will become apparent from the
detailed description that follows and will be particularly pointed out in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] To complete the description and in order to provide for a better understanding of
the invention, a set of drawings is provided. Said drawings form an integral part
of the description and illustrate an embodiment of the invention, which should not
be interpreted as restricting the scope of the invention, but just as an example of
how the invention can be carried out. The drawings comprise the following figures:
Figure 1 shows a schematic representation of a system for carrying out the method
of the invention.
Figure 2 shows a rectangle to rectangle in a perpendicular plane; all boundaries are
parallel or perpendicular to x and ξ boundaries.
Figure 3 shows a rectangle to rectangle in a parallel plane; all boundaries are parallel
or perpendicular to x and ξ boundaries.
Figure 4 shows a rectangular heat capturing device's and object's surfaces listed.
Figure 5 shows a view factor of the object's wall to heat capturing device's roof.
Figure 6 shows a view factor of the object's wall to heat capturing device's wall.
Figure 7 shows a view factor of the object's top wall to heat capturing device's wall.
Figure 8 shows a view factor of the object's top wall to heat capturing device's roof.
Figure 9 shows all heat transfer phenomena in the energy capturing space.
Figures 10-12 show a graphical representation of the listed cases 1-8 mentioned in
the following Table 1, in which the heat capturing device and the object in the heat
capturing device are represented. The representation may be considered as a proportional
representation of the dimensions of the heat capturing device relative to the dimensions
of the object.
Figure 13 shows a perspective view of an example tunnel-shaped heat capturing device
using the tubes and the energy insulating layer, the tubes being positioned substantially
perpendicular to the direction of displacement of the at least one object relative
to the tunnel-shaped heat capturing device.
Figure 14 shows a cross-sectional representation of the tunnel-shaped heat capturing
device and the further layers of the tunnel-shaped heat capturing device of figure
13.
Figure 15 shows a perspective view of another example tunnel-shaped heat capturing
device using the tubes and the energy insulating layer, the tubes being positioned
substantially parallel to the direction of displacement of the at least one object
relative to the tunnel-shaped heat capturing device.
Figure 16 shows a cross-sectional representation of the tunnel-shaped heat capturing
device and the further layers of the device of figure 15.
Figure 17 shows a perspective view of an example inner energy capturing layer.
Figure 18 shows a representation of an example architecture of some tubes of the tube
bundle forming the inner energy capturing layer and a representation of the corrugated
intermediate energy reflecting layer.
DESCRIPTION OF A WAY OF CARRYING OUT THE INVENTION
[0029] The present description represents exemplary embodiments on how to carry out the
present invention.
Equation development for calculating the size and shape of the heat capturing device
[0030] The heat capturing device's geometry (see figure 1), in particular the width (A)
and the height (B) of the inner energy capturing layer; the object's (or objects')
geometry, in particular the height (C) and the width (D) of the object, considering
that the object or objects are assimilated to a parallelepiped of smaller volume that
can contain them; and the spatial relationship between the heat capturing device and
the at least one object, in particular, the height of the position of the heat capturing
device relative to the at least one object, influence the thermal behavior of the
heat capturing device. The length (L) is the length to be covered in the process with
one or more heat capturing devices lined up next to each other (not the length of
an individual heat capturing device).
[0031] In the following lines it is explained the procedure carried out to reach an equation
that gives the optimal geometry of the inner energy capturing layer, and thus of the
heat capturing device as a whole, for some given conditions. This optimal geometry
will maximize the heat flow absorbed by the inner energy capturing layer of the heat
capturing device.
[0032] To obtain the equation some assumptions may be considered (see Figure 1):
- In the calculation of the view factors, the heat capturing device 2 and the at least
an object 1 have been considered as 3D bodies, where they have a finite length (L).
This has been done as the heat capturing device could, in some cases, have a length
short enough to make considerable the radiation that is lost at the ends;
- The heat capturing device is in a symmetrical position to the centre of the at least
an object;
- For the heat balance equation, it has been considered that the heat capturing device
is perfectly insulated from behind (face not exposed to the radiation from the at
least one object) due to the intermediate energy reflecting layer and the energy insulating
layer included in the heat capturing device design;
- It may have to be specified:
∘ the average temperatures (T) of the objects' surface (the surface and the kernel
temperature of the object are different), the heat capturing device and the ambient
inside the energy capturing space (in the space between the piece and the heat capturing
device);
∘ the optical properties of the at least one object surfaces and heat capturing device
surfaces;
∘ the dimensions of the objects considered as the parallelepiped of smaller volume
that can contain them (C and D);
∘ the height (Hzl) of the position of the heat capturing device relative to the lower
surface of the piece (or object) (in case there is any restriction that avoids that
both systems are over the same plane);
∘ the length (L) to be covered in the process with one or more heat capturing devices;
∘ the maximum and minimum dimensions (height and width) the heat capturing device
could have due to process constraints;
∘ the estimated convection heat transfer coefficient (hconv) of the air between the objects and the heat capturing device.
[0033] Other parameters used in the following calculation are Ai (area of the different
surfaces) and α (absorptivity of different surfaces), Ti (temperature of the different
surfaces), ε
i (Emissivity of the different surfaces), α
i (aabsorptivity of the different surfaces), σ (Stefan-Boltzman constant 5,67.10
-8 W/m
2K
4) and h
conv (convection coefficient of the air inside the energy capturing space (tunnel). Sub-index
1 refers to the object, sub-index 2 refers to the heat capturing device and sub-index
3 refers to the surface that closes the energy capturing space (see figure 4).
Obtention of the view factor equation
[0035] Using these equations, the view factor between the heat capturing device and the
object has been calculated. During the procedure the nomenclature from Figure 4 has
been used.
[0037] The coordinates x, y, a and b are represented graphically in the Figures 5-8.
Once the auxiliary variables are known, the view factor equations can be posed:
Object's side wall to heat capturing device's side wall:
[0038] View factor from one object's side wall to the opposite heat capturing device walls
(11-21 or 13-23). As figure 4 is symmetrical, the view factors from one object's side
wall to its opposite heat capturing device's side wall and from the other object's
side wall to its opposite is the same:
[0039] From the equation above:
[0041] Finally:
Object's side wall to heat capturing device's roof:
[0042] As well as in the previous case, as the figure 4 is symmetrical, the view factor
from one object's side wall to the heat capturing device's roof or tunnel's ceiling
is the same as the view factor from the other object's side wall to the heat capturing
device's roof:
[0043] From the equation above:
[0044] Where:
[0045] Finally:
Object's upper wall to heat capturing device's wall:
[0046] In this case also due to the symmetrical shape of the heat capturing device, the
view factor from the object's upper wall to any of the heat capturing device's walls
is the same:
[0047] From the equation above:
[0048] Where:
[0049] Finally:
Object's upper wall to heat capturing device's roof:
[0050] From the equation above:
[0052] Finally:
Total view factor:
[0053] With the previous equations it is possible to calculate the total expression for
the view factor from the object to the tunnel defined by the heat capturing device:
[0054] Developing the expression:
Obtainment of the equation of the net heat flow to the heat capturing device.
[0057] The optimal geometry of the heat capturing device is the one that maximizes the amount
of net heat reaching the heat capturing device. The equation that quantifies the amount
of heat reaching the heat capturing device is obtained from the energy balance of
the heat capturing device, where:
[0058] Figure 9 shows the different heat fluxes considered. The heat capturing device is
assumed to be perfectly insulated from the back.
[0059] For the calculation of the net heat flux transferred through radiation the object
1 and the heat capturing device 2 are considered as grey bodies (a body that emits
radiation at each wavelength in a constant ratio less than unity to that emitted by
a black body at the same temperature) and the surface 3 is considered a black body
(a body that absorbs all incident electromagnetic radiation, regardless of frequency
or angle of incidence, an ideal emitter that at every frequency emits as much or more
thermal radiative energy as any other body at the same temperature).
[0060] Solving the energy balance for the radiation, it is calculated the net heat flux
transmitted to the heat capturing device:
[0061] Where:
[0062] As the surface 3 that closes the energy capturing space behaves as a black body:
[0063] The Qnet_radiation is calculated clearing Q2_net radiation resulting in:
[0064] The next step is to calculate the energy transferred to the internal ambient through
convection (Qnet_convection).
[0065] The value of the convection heat transfer coefficient (h
conv) may be introduced by the user.
[0066] Finally, the equation for the total net heat flux to the heat capturing device is
presented below:
Results
[0067] The optimal design is obtained by solving an optimization problem. This is formulated
as the maximization of the total heat transferred between the piece (object) and the
heat capturing device (more particularly the bundle of tubes of the inner energy capturing
layer), subject to the physical and manufacturing constraints.
[0068] It should be noted that the minimum width and height that the heat capturing device
can have (since in real processes these dimensions must leave a safety margin) are
also input parameter.
[0069] The model-based optimization approach was used to formulate the design optimization
problem. The supporting model was developed in Python 3.6 based on physics equations.
Regarding the optimizer, the proposed solution is based on the L-BFGS-B algorithm
implemented in the Scipy (v1.1.0) optimization package.
[0070] The following table presents different cases in which the input parameters of the
system have been varied. Depending on the value of these, the optimum geometry of
the heat capturing device varies.
Table 1
|
Case 1 |
Case 2 |
Case 3 |
Case 4 |
Case 5 |
Case 6 |
Case 7 |
Case 8 |
A minimum |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.455 |
B minimum |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.455 |
0.255 |
C |
0.155 |
0.155 |
0.155 |
0.155 |
0.155 |
0.155 |
0.355 |
0.155 |
D |
0.155 |
0.155 |
0.155 |
0.155 |
0.155 |
0.155 |
0.155 |
0.355 |
H |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
L |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
ε1 |
0.8 |
0.8 |
0.8 |
0.8 |
0.95 |
0.65 |
0.8 |
0.65 |
ε2 |
0.96687 |
0.96687 |
0.7 |
0.7 |
0.7 |
0.7 |
0.7 |
0.7 |
α1 |
0.8 |
0.8 |
0.8 |
0.8 |
0.95 |
0.65 |
0.8 |
0.65 |
α2 |
0.9664 |
0.9664 |
0.7 |
0.7 |
0.7 |
0.7 |
0.7 |
0.7 |
T1 |
900 |
900 |
900 |
900 |
900 |
900 |
900 |
900 |
T2 |
400 |
400 |
400 |
400 |
400 |
400 |
400 |
400 |
T3 |
24 |
24 |
24 |
24 |
24 |
24 |
24 |
24 |
hconv |
10 |
0 |
10 |
5 |
10 |
10 |
10 |
10 |
A optimum |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.255 |
0.455 |
B optimum |
0.255 |
0.73581 |
0.36354 |
0.59339 |
0.44862 |
0.27763 |
0.81044 |
0.32206 |
[0071] Figures 10-12 show a graphical representation of the listed cases 1-8 mentioned in
the following Table 1. In particular such figures show a schematic representation
of the size ratio between the object and the heat capturing device (named as collector
in the figures for clarity purposes).
[0072] Case 1 (see Table 1) has been selected as a reference case where the optimal solution
for the heat capturing device geometry matches with the minimal dimensions defined
for it. As can be seen in cases 1 to 6 (see Table 1) with the same minimum values
for the dimensions of the heat capturing device the optimal solution is affected by:
the operating conditions: case 2 and case 4 with lower convection losses;
the absorptivity and emissivity of the inner surfaces of the heat capturing device:
case 3 and 4 with lower absorptivity and emissivity than the reference case 1;
the absorptivity and emissivity of the object: case 5 has high values (such as the
ones corresponding to glass pieces) and case 6 has lower values; and
cases 7 and 8 illustrates also the effect of the shape of the object with the same
operating conditions as the reference Case 1.
[0073] As can be seen although intuitively it might seem that the optimal dimensions of
the heat capturing device will always tend to be the minimum, the results show how
this is not so. This is a surprising and unexpected technical effect achieved by the
claimed scope.
Conclusions
[0074] As seen in the previous section, with the optimization procedure it is possible to
obtain the best geometric solution for the heat capturing device in many situations.
These situations can be extrapolated to many industrial processes that produce high
temperature pieces from which emitted radiation is captured for the heat capturing
device herein described.
[0075] Figure 13 shows a perspective view of an example tunnel shaped heat capturing device
30 wherein the inner energy capturing layer comprises a bundle of tubes 31. The tubes
31 may have preferably a circular cross section. The heat capturing device 30 may
be implemented using tubes 31 having other cross sections such as square or elliptical
cross sections. The tubes 31 are connected to the represented headers 32. The tubes
31 of the bundle may be welded to the headers 32. The inner energy capturing layer
31 is covered by an intermediate energy reflecting layer 33 that in turn is covered
by an energy insulating layer 34, preferably made of ceramic fiber with low thermal
conductivity. The energy insulating layer 34 is covered by an outer casing 35, preferably
made of a metal. The headers 32 transport the heat captured by the fluid inside the
tubes of the heat capturing device 30 to either a heating station or to a heat exchanger
(not shown). The heat capturing device 30 comprises control means which may control
the flow of fluid in the tubes 31 of the bundle and may control at least one pump,
cooling means and/or valves (not shown). The control means of the heat capturing device
30 may control the cooling means or control one or more heat exchangers for regulating
the temperature of the fluid flowing in the tubes 31. The control of the pump and/or
valves by the control means allow to control the quantity or volume of fluid circulating
in the tubes 31. The fluid circulating in the tubes 31 of the bundle may be water,
an organic thermal oil or silicone based thermal oil.
[0076] The objects introduced in the energy capturing space 36 are at high temperatures,
such as typically greater than 500°C. The heat capturing device is designed to operate
with medium temperatures in the fluid around 350° C.
[0077] Figure 14 shows a cross-sectional cut of the heat capturing device 30 of figure 13.
It can be appreciated that all layers, namely the outer casing 35, the energy insulating
layer 34, the intermediate energy reflecting layer 33 and the inner energy capturing
layer 31 (e.g. the tubes) have a tunnel shape as shown which indicates that said layers
also define the ceiling and the sides of the tunnel shape arrangement. All said layers
may also be at least partly disposed in the floor of said tunnel shaped structure,
such that the tubes 31 are also able to capture heat or energy from the floor side
of the structure.
[0078] In some embodiments, the outer casing 35 may be disregarded, and it is not installed.
[0079] Preferably, the tubes 31 are not in direct contact with the intermediate energy reflecting
layer 33 or reflecting plate, i.e., the inner energy capturing layer 31 (e.g. tubes)
and the intermediate energy reflecting layer 33 are separated by air or some gas.
In some embodiments the inner energy capturing layer 31 may contact the intermediate
energy reflecting layer 33. The intermediate energy reflecting layer 33 may be in
direct contact with the energy insulating layer 34, or both layers (intermediate energy
reflecting layer 33 and energy insulating layer 34) may be separated by a chamber
of air or gas or insulating fluid. The energy insulating layer 34 may be in contact
with the outer casing 35 or may be separated by air.
[0080] The outer casing 35 may be made of steel or other metal or may be made of refractory
material or heat resistant material.
[0081] Figure 15 shows a perspective view of another example tunnel-shaped heat capturing
device 40 with the tubes 41 being positioned substantially parallel to the direction
of displacement of the two objects 47 relative to the energy capturing space 46 defined
by the tunnel-shaped heat capturing device 40. While Figure 15 shows two identical
objects placed parallel to each other, any number of objects with any different shape
and spatial relationship to each other could be placed in the energy capturing space
46.
[0082] In such example, the tubes 41 of the bundle may have preferably a circular cross
section although any other cross sections such as square or elliptical cross sections
may be implemented. The tubes 41 are connected to the represented headers 42 (not
shown in this figure). The headers may be positioned at both openings of the tunnel
such that their geometry corresponds to the geometry of the openings.
[0083] In such example, the intermediate energy reflecting layer 43 is attached to the inner
surface of the outer energy insulating layer 44. The energy insulating layer 44 is
located between the intermediate energy reflecting layer 43 and the outer casing 45.
The energy insulating layer 44 may be made of ceramic fiber with low thermal conductivity.
[0084] Figure 16 shows a cross-sectional representation of the tunnel-shaped heat capturing
device and the further layers of the device of figure 15.
[0085] Figure 17 shows a perspective view of an example inner energy capturing layer 50.
In such example, the inner energy capturing layer 50 is formed by a bundle of tubes
51 for circulating the heat transfer fluid, a first header 52 and a second header
53. The tubes 51 are placed in parallel to each other and have the same diameter.
Besides, the distance between two consecutives tubes 51 is the same along the entire
inner energy capturing layer 50. The fluid 54 ingress in the tubes 51 via the first
header 52 through a first opening 55. The first header 52 is divided in sections 56
wherein each section is communicated to a set of tubes 51 but isolated from the contiguous
sections 56 within the first header 52. The second header 53 is divided in sections
57 wherein each section is communicated to a set of tubes 51 but isolated from the
contiguous sections 57 within the first header 53. In such example, the fluid 54 that
enters into the first section 56a of the first header 52 circulates through the tubes
51 connected to this first section 56a until the first section 57a of the second header
53, which in turn is connected to other tubes for keeping circulating the fluid towards
a second section 56 b of the first header, and so on, until the fluid reaches the
last section of the first header 53 through which the fluid 54 exits the inner energy
capturing layer 50 via a second opening (not shown in this figure).
[0086] Figure 18 shows a representation of an example architecture of some tubes of the
tube bundle forming the inner energy capturing layer and a representation of the corrugated
intermediate energy reflecting layer.
[0087] In such example, the distance (d1) between the centers of two consecutive tubes is
1.25 times the outside diameter of one of the tubes. All tubes have the same diameter.
The minimal distance (d2) between the outer surfaces of two consecutives tubes is
0.25 times the diameter of one of the tubes. Due to the particular pattern of the
corrugated intermediate energy reflecting layer the radiation going through the existing
space between tube is reflected in the reflective corrugated surface and directed
back to the collecting tubes.
[0088] The invention is obviously not limited to the specific embodiments described herein,
but also encompasses any variations that may be considered by any person skilled in
the art (for example, as regards the choice of materials, dimensions, components,
configuration, etc.), within the general scope of the invention as defined in the
claims.
1. Heat capturing device comprising:
an upper side and lateral sides connected to the upper side, said connected sides
define an energy capturing space, the device further comprising:
an energy insulating layer;
an intermediate energy reflecting layer; and
an inner energy capturing layer capturing energy from at least one object located
at least partly in the energy capturing space;
wherein the dimensions of the inner energy capturing layer are based on the dimensions
of the at least one object and based on a further parameter, said further parameter
being at least one of: at least a second parameter of the at least one object, at
least one parameter of the inner energy capturing layer, at least one parameter of
the energy capturing space and any combination thereof.
2. The device according to claim 1, wherein the second parameter of said at least one
object is selected from a group comprising the emissivity of at least one or more
of the surfaces of the at least one object, the absorptivity of at least one or more
of the surfaces of the at least one object and a combination thereof, said second
parameter of said at least one object defining the width of the inner energy capturing
layer.
3. The device according to any one of claims 1-2, wherein the further parameter defines
the weight and the height of the inner energy capturing layer, said further parameter
being at least one of: the convection coefficient of the air inside the energy capturing
space, the emissivity of at least one of the surfaces of the object, the absorptivity
of at least one of the surfaces of the object, the emissivity of at least one of the
surfaces of the inner energy capturing layer, the absorptivity of at least one of
the surfaces of the inner energy capturing layer and any combination thereof.
4. The device according to any one of claims 1-3, wherein the inner energy capturing
layer is a bundle of tubes, the bundle of tubes covers a tunnel-shaped surface, wherein
at least of one or more of the tubes of the bundle comprises a heat transfer fluid.
5. The device according to claim 4, wherein the distance between the center of two consecutive
tubes is between 1,25 and 2 times the external diameter of a tube of the bundle.
6. The device according to any one of claims 4-5, wherein the bundle of tubes is connected
to at least two headers to distribute the heat transfer fluid through the bundle of
tubes and wherein the heat transfer fluid is feed to the bundle of tubes at a first
temperature and removed at a second temperature, the second temperature being higher
than the first temperature.
7. The device according to any of claims 4-6, wherein the external surface of the bundle
of tubes is covered with high absorptivity coatings or high absorptivity paint.
8. The device according to any of claims 1-7, wherein the energy absorbed is heat and
the heat absorbed by the inner energy capturing layer is defined as follows:
Wherein the nomenclature is the following:
Ai Area of the different surfaces
Ti Temperature of the different surfaces, wherein T1 is the temperature of the object, T2 is the temperature of the fluid circulating through the heat capturing device, T3 is the ambient temperature in the energy capturing space
εi Emissivity of the different surfaces
αi Absorptivity of the different surfaces
hconv Convection coefficient of the air inside the tunnel.
Fij View factor from surface i to surface j (according to figure 4).
σ Stefan-Boltzman constant 5,67.10-8 W/m2K4.
Subscripts/Sub-index:
1 Object
2 Inner energy capturing layer
3 Surface that closes the energy capturing space
9. The device according to any one of claims 4-8, wherein the intermediate energy reflecting
layer comprises a corrugated shaped surface behind the bundle of tubes, wherein the
convex part of corrugated shaped surface is located in correspondence with at least
one of the tubes of the bundle and the concave part of said surface is located in
correspondence with at least one of the separations between the tubes.
10. The device according to any one of claims 4-9, wherein the device comprises at least
one sensor for measuring the temperature of the at least one object, or at least one
sensor for measuring the temperature of the energy capturing space, or at least one
sensor for measuring the temperature inside the tube or the temperature of the fluid
within the tube, or at least one sensor for detecting the object either entering into,
or exiting out of or remaining in the energy capturing space or a combination of said
sensors.
11. The device according to any one of claims 1-10, wherein the energy insulating layer
covers the intermediate energy reflecting layer, and the intermediate energy reflecting
layer covers the inner energy capturing layer, and wherein the device further comprises
an outer casing covering the energy insulating layer.
12. The device according to any one of claims 1-11, wherein the device comprises transport
means and control means, the control means configured to control the transport of
the object from or to the energy capturing space, wherein the device automatically
transporting the object to or from the energy capturing space based on a certain captured
temperature measured by at least one or more said sensors, said certain temperature
exceeding or being below a predetermined threshold.
13. The device according to any one of claims 11 or 12, wherein the control means are
configured for controlling the quantity of fluid and/or the speed of the fluid circulating
inside the bundle of tubes, wherein the control means automatically control said quantity
and/or speed of fluid based on the data measured by at least one of the sensors.
14. The device according to any one of claims 1-13, wherein the device comprises a modular
structure permitting to add parts to the device or remove parts from the device.
15. A heat capturing system comprising:
a heat capturing device according to any one of claims 1 to 14; and
at least one object located at least partly in the energy capturing space;
wherein the heat capturing device is configured to capture radiated heat from the
at least one object by the inner energy capturing layer.