ITRM20130240A1 - SOLAR RADIATION COOLING UNIT. - Google Patents

Description

â € œSOLAR RADIATION COOLING UNITâ €

Description

Technical sector

The present invention refers in general to the sector of cooling and air conditioning devices and can be applied in general in offices, hotels, villas, homes in tourist villages, shops, etc., or for applications cooling in the small-sized commercial sector (liquid refrigeration, etc.).

More particularly, the present invention relates to a solar cooling unit of the type of an absorption chiller.

The inventor of the present patent application has actually invented a solar radiation cooling unit, interesting from a commercial point of view and usable for uses / applications of modest dimensions, for air conditioning.

In 2011 the same applicant filed a patent application (PA 2011 70396) with the Danish Patent Office (DK PTO) for an invention relating to a process or a method of cooling a building, this document being considered included herein for any reference. This patent was extended as a PCT application on July 18, 2012 (WO 2013/010549 A2), which is also considered to be included in this document for any reference.

State of the art

The state of the art includes different types of cooling units that exploit the solar energy collected by the already known thermal solar panels, to cool the water to be used for air conditioning, through an evaporation cycle and absorption of a refrigerant.

Some examples of such units are provided by the following documents:

US 6,539,738 B2, WO 2009/093979 A1, WO 2011/028186 A2.

In particular WO 2009/093979 A1 and the previously cited WO 2013/010549 A2 (the same applicant of the present application) describe systems in which the working solution itself (working fluid) passes through the thermal solar panels differently from what happens in US 6,539,738 B2, in which the solar panels are only crossed by water and belong to a distinct circuit of the system, used for the collection of solar energy (distinct from the real absorption cooler, see figure 7 of US 6,539,738 B2).

Now WO 2013/010549 A2 (the same applicant of the present application) dealt with the project as a whole, the solar cooling unit, while the present invention focuses on the design / design of the specific components, to obtain a project as much as possible reliable and efficient for the working fluid.

Therefore, there is still a need to further improve the functionality of a solar absorption chiller.

Description of the invention

The purposes of the present invention consist in realizing a solar radiation cooling unit for applications / uses of small dimensions for air conditioning which is reliable, compact, which has a better performance and which can operate in various solar irradiation conditions. .

Furthermore, another object of the present invention is to recover at least part of the heat from the absorber, in suitable ways.

These objects are achieved as defined in the appended claims.

By providing a backup power source that directly heats the working solution inside the separator, it is possible to operate the solar cooling unit for example at night and on cloudy days. In this way, the air conditioning effect is always available. Simple valve means, for example a three-way valve, can be used to bypass the solar thermal panels in this case. Thus, it is possible to eliminate energy losses in thermal solar panels when they are not irradiated by the sun. A combined operation, which partly exploits the (in this case weak) radiation on the panels produced by the sun (which acts as a preheating energy source) and partly the reserve energy source (heating coil in the separator), is just as possible.

The correct operation of the cooling unit is guaranteed by the fact that the panels are always filled (i.e. full) with the working solution, thanks to a process control system (PCS) even during operation with the reserve energy source. This is an economical and reliable way to prevent the gaseous refrigerant from flowing back to the solar thermal panels and condensing within them. This system reduces costs as no non-return valve (or similar) will be required to prevent backflow, and there will also be no damage to the performance of the solar cooling unit due to pressure losses inside the separator. . However, if desired, the present invention does not exclude further use of a non-return valve.

The best performance of the solar cooling unit also derives - among other things - from the specific design / design of its absorber. According to this aspect of the invention, the absorber contains a working fluid distributor having two effects:

1) evenly distribute the incoming liquid (strong solution) between a plurality of vertical absorber tubes;

2) evenly distribute this liquid (after it enters a single tube) around the circumference of the internal wall of the respective tube.

A further important feature of the present invention, which concerns the reliability of operation, concerns the management of the concentration of the working fluid. It is known that the crystallization of the absorption medium occurs at certain temperatures and concentrations of the absorption medium in the working fluid. The present invention uses temperature sensors which measure the temperatures of the refrigerant vapor and of the liquid solution respectively, instead of adopting (for managing the concentration of the working fluid) conductivity sensors, pressure transmitters, etc. The present invention is more reliable since the temperature sensors are â € œnon invasiveâ € (they do not produce leaks or leaks in the system). The invention provides an indirect method for determining the concentration of the absorption medium (LiBr) in the solution of the working fluid. By means of equilibrium diagrams relating to the specific liquid solution that is adopted, and by means of a corresponding `` look up table '', the process control system (PCS) is able to immediately obtain the values of the saturation pressure and concentration of the absorbent medium. If this concentration is too high, the PCS will act appropriately to lower the risk - or even eliminate any risk - of crystallization. Other objects and / or advantages of the present invention are contained in the following detailed description or may be immediately / easily deduced by the expert in the field, or may derive from the practical implementation of the present invention.

Brief description of the drawings

The present invention will now be described in more detail by way of example only, and without any intention of limitation thereof. The attached drawings together with the following detailed description illustrate possible embodiments of the invention, which facilitate an expert in the field who would like to reproduce the same, in which:

Figure 1 shows a general schematic view of the fundamental components of the solar radiation cooling unit (so called solar cooler or â € œsolar chillerâ €) according to the present invention during operation with thermal solar panels;

Figure 2 is similar to Figure 1 but shows the operation of the solar cooling unit according to the present invention, through the backup power supply (when solar radiation is not available);

Figure 3 shows a possible design / design of the separator according to the present invention, in which Fig. 3 (a) is a side view, Fig. 3 (b) a front view, and Fig. 3 (c) a plan view and the dashed lines represent the internal parts of the separator;

Figure 4 shows a front view (in Fig. 4 (a)), a side view (in Fig. 4 (b)), and a cross section (A-A) of an absorber tube (in Fig. 4 (c )), of the main part of the absorber (absorption unit) according to the present invention;

Figure 5 is an illustration or a representation of the recovery of heat lost by the absorber according to the present invention;

Figure 6 is an equilibrium diagram for LiBr / H2O (for example: solution temperature 70 ° C and refrigerant gas temperature 40 ° C, which is equivalent to a pressure of 75 kPa and a concentration of 53% by weight LiBr), used to monitor the concentration of the solution and avoid crystallization using only temperature sensors;

Figure 7 is a representation of the configuration of the evaporator according to the present invention, which shows the various temperatures and various flows of chilled water (inlet and outlet), cold vapor of the refrigerant, and condensed refrigerant;

Figure 8 shows a shell for chilled water, equipped with a coil, which is part of the evaporator of Fig. 7.

Description of favorite realizations

The solar-powered air conditioner according to the present invention is designed to reduce costs, to have a compact size, and to be reliable. All these advantages are obtained by properly designing the components of the so-called â € œabsorption chillerâ €. A further advantage is given by the recovery of the heat lost by the absorber. The present invention indicates two efficient ways of recovering this heat. It is obvious that the solar energy cooling unit according to the present invention, in applying the solar energy cooling principle, can work indifferently with very different types of working fluids. Therefore, for convenience only, this document will repeatedly mention in the following only an aqueous solution of lithium bromide (LiBr) as a â € œworking fluidâ € or â € œworking solutionâ €.

The key components of the solar radiation cooling unit and their connections are shown in Fig. 1.

With 1 is indicated a solar thermal panel (or more panels of this type) irradiated (normally) by the sun. The "mentioned" solution, that is the "working fluid" (here: LiBr / H2O), is heated by the radiation and exits from panel 1. Then, it reaches the separator 2 (described in 0 below). Note that the arrows with dashed lines indicate the flow of the refrigerant, while the arrows with solid lines indicate the flow of the solution (for the strong solution or for the weak solution). A separator 2 separates the hot refrigerant vapor from the working fluid solution, and this refrigerant vapor then enters a condenser 4. In an evaporator 6 (described below) the condensed refrigerant evaporates at a relatively low temperature and pressure low. Evaporator 6 is used to produce chilled water, to be used for air conditioning of a building etc. (note that the respective chilled water ducts extending from and to evaporator 6 respectively are not shown in figures 1 and 2).

A housing unit 7 (to be described below) according to the present invention is associated with an absorber (absorption unit) 5 in this particular non-limiting embodiment of the invention. The absorption unit or absorber 5 (described below) has the usual function of absorbing the refrigerant vapor in countercurrent with the concentrated or strong solution of LiBr which arrives from the base of the separator 2 passing through a conventional heat exchanger 3 of energy recovery. A circulation pump 8 is arranged downstream of the housing unit 7 and upstream of the heat exchanger 3, to pump the diluted aqueous solution of LiBr towards the heat exchanger 3, after the absorption of the cold refrigerant vapor by the concentrated solution inside the absorber tubes (see below). A three-way valve 9 is provided to direct the non-concentrated solution (weak solution) towards the lower part of the panels or of the solar thermal panel 1, so as to repeat the cycle when the sun is present (operation represented in Fig. 1).

Reduction valves are inserted or mounted in the circuit or system upstream of evaporator 6 and absorber 5, respectively.

Now, with reference to Figure 2, it shows the operation of the solar energy cooling unit according to the present invention, in the absence of solar radiation. In this case, a reserve or backup source (see below) directly heats, according to the present invention, the working solution inside the separator 2. In this case, the three-way valve 9 is set so as to divert the flow of working solution in the direction of the separator 2 instead of towards the lower part of the solar thermal panel 1. For this purpose the separator 2 has a bypass inlet 16 (compare figures 1 and 2) which will be described afterwards.

A single fan 10, shown in Figures 1 and 2, is used to disperse the heat from the absorber and condenser, in a way (series configuration) already illustrated in the previous patent application of the same applicant WO 2013/010549 A2 (cited over).

An essential design parameter for the operation of the solar cooling unit (so-called â € œsolar chillerâ €) is the design of the absorber and auxiliary components used to separate and respectively absorb the refrigerant from the work. This will be described below.

Separator with power reserve (backup)

The solar powered air conditioning unit according to the present invention must provide a cooling effect with or without solar radiation. As for the operation when solar radiation is limited or even absent, a backup energy source must carry out the separation of the refrigerant from the working fluid. Fig. 2 shows the fundamental components and flow directions during operation based on the backup power supply. To separate the coolant from the mixture of working fluid and coolant, when the sun is present, the present invention applies a separator (reference number 2 in Fig. 1) which is represented in Fig. 3 in three orthogonal views. The same separator is also used when operating with the backup power source.

In general, the purpose of the separator 2 represented in Fig. 3 is to separate the refrigerant from the working fluid (for example lithium bromide and water) before the absorber 5.

When the cooling device works with solar radiation (Fig. 1), the working fluid enters with a high speed through an inlet 11 of the working fluid, from the solar thermal panel 1, in the form of a fluid to two phases which includes the refrigerant and the absorption medium. Inlet 11 is designed as a tangential inlet to reduce flow velocity and reduce upward splashing. A protection against splashes and droplets (plate) 15 facilitates the gaseous refrigerant to enter the upper part of the separator 2 and to pass through an anti-fog (mist separator) 14 towards the condenser 4 (towards the outlet of the refrigerant 12 leading to the condenser 4). An example of anti-fog (fog separation device) 14 is given by a cylindrical-shaped mesh comprising a plurality of mesh / mesh layers.

The demisting device 14 is designed to retain extremely fine droplets which then reach the bottom of the separator 2 thus allowing the refrigerant gas to pass to the condenser 4 with a low pressure loss.

The concentrated working fluid (strong solution) leaves the separator 2 through a lower outlet 17 in the direction of the absorber 5.

When the cooling device (so called â € œchillerâ €) is operated only through the backup energy supply, i.e. when the sun is absent, a heating coil 13 supplies thermal energy to separate the refrigerant from the solution of work. By virtue of the low absolute pressure inside the separator 2, the working fluid boils at a low temperature, for example 50 ° C - 90 ° C, and the refrigerant gas follows the path described above for operation with the solar radiation.

As has already been mentioned, the three-way valve 9 is used to direct the working fluid to the panels 1 when solar-based operation is required (Fig. 1). When it is not feasible to use the thermal solar panels 1 for an energy input, then the three-way valve 9 instead directs the working fluid to the separator 2 instead of circulating the fluid through the panels (Fig. 2). Therefore, by adopting the three-way valve 9, it is possible to eliminate energy losses through the panels and to preserve the efficiency of the system.

Combined operation is also considered when solar energy is available but insufficient to provide nominal cooling capacity. In the latter case the reserve power supply (coil 13) provides an additional required heat input and operation is as shown in Fig. 1.

It should be noted that the heating coil 13 is connected, for example, to a boiler or the like.

Alternatively, although this is not the preferred way, the coil 13 could be replaced by another reserve energy source of an appropriate type, for example burners.

Prevention of refrigerant backflow towards the solar thermal panels During the operation of the cooling device when the sun is absent (Fig. 2), the energy is supplied by the heating coil 13 to the separator 2. In this case, the supply of working fluid does not take place from the thermal solar panels but can take place through the bypass inlet 16 of Fig. 3.

Thanks to the energy supply, the working fluid in the separator will boil and generate a gaseous refrigerant which must be guided towards the condenser 4 through the demister 14.

In this configuration shown in Fig. 2, since the separator 2 continues to be connected to the solar thermal panels 1, there is a risk that the gaseous refrigerant flows through the (tangential) working fluid inlet 11 which extends from thermal solar panels. If the solar panels 1 are empty and not heated by solar radiation, the gaseous refrigerant can condense in the panels. This would result in incorrect operation, as the refrigerant in this case could not be used to supply evaporator 6 and the pressure in the system could drop below that corresponding to the operating conditions in the separator 2.

To avoid such a situation, a process control system (PCS), not shown in the drawings, is designed to ensure that the solar thermal panels 1 are filled with working solution during operation in the absence of solar radiation. (Fig. 2). During the transition from the operating mode that uses the thermal solar panels (Fig. 1) to the operating mode with backup power supply (Fig. 2), or in the event that the operation starts using the power supply of backup (Fig. 2), the PCS will fill the thermal solar panels. The purpose of this characteristic is to provide an economical and reliable way to prevent the reflux of gaseous refrigerant in the thermal solar panels 1 and its condensation.

Distributors with film (layer) descending from the absorber

The absorber or absorption unit 5 in the so-called â € œsolar chillerâ € consists of a single-pass, parallel flow heat exchanger, with a descending film / layer inside its tubes.

In order to properly absorb the refrigerant vapor coming from evaporator 6 into the concentrated working fluid, it is essential to have a uniform distribution of concentrated working fluid in the absorber tubes. Furthermore, it is important to distribute the concentrated working fluid entering the absorber tubes well around the inner circumference of the tubes.

In other words, it is also necessary to evenly distribute the working fluid (the concentrated solution in this case) around the inner circumference (wall) of each single absorber tube.

Fig. 4 shows a design that ensures uniform distribution of the working fluid to the individual absorber tubes, as well as a device that distributes the fluid to the tube wall ensuring that the entire circumference is wet.

According to Figure 4, the working solution enters the inlet distributor 21 of the working fluid in the absorber, this distributor being included in the absorber 5 shown in Figs. 1 and 2.

A distribution plate 23 ensures that the fluid does not enter directly (forming splashes) in the tubes 25 of the absorber (only some of these tubes are indicated by the numerical references in Fig. 4), but flows along and across the distribution plate 23 up to the base 26 of the inlet distributor 21. When the liquid level in the horizontal inlet distributor 21 is sufficiently high, the concentrated working fluid flows inside the individual tubes 25 of the absorber.

However, it could happen that the distribution plate 23 located inside the absorber inlet distributor 21 is completely omitted. This happens when the system works with a manifold 21 which is substantially always full of working solutions, or almost. In this condition it is obvious that the distribution plate 23 would be useless, and a uniform film / layer can be generated by the descending film devices (see below) housed in each absorber tube.

Fig. 4 shows an embodiment of the invention in which the distributor plate 23 is present. In this case, shown in Fig. 4, the manifold 21 has a cylindrical shape. Then, a particular shape - that is a curved shape - of the upper end of the absorber tubes 25 ensures that they adapt (in this specific case) to the cylindrical configuration of the collector 21, and that they remain covered by the periphery of the distributor plate; in this way, the quantity of working fluid can be equally distributed among the tubes 25 of the absorber. It should be observed that if the distributor (manifold) 21 for entering the working fluid into the absorber assumes another (non-cylindrical) shape, then the upper ends of the absorber tubes 25 may also be straight.

According to the invention, in each tube 25 of the absorber a descending film device 24 is positioned, located in the center of the tube, to allow the formation of a uniform film thickness which flows downwards in the tube 25 of the tube. absorber. The diameter of the device 24 is designed in such a way as to allow the formation of a specific film thickness, ensuring that the fluid is distributed equally around the inside of the absorber tube wall.

The descending film device 24 can be a sphere 24, as shown, positioned in the axial center of the various absorber tubes, or connecting tubes 25. In the drawings of Fig. 4, the absorber tubes 25 have three deformations support 27 (see the cross-sectional view of Fig. 4c) for a correct positioning of the descending film distributor 24. In general, a certain number of deformations 27 (obtained from a deformation process of the same material that forms the tube, yes to guarantee an economic process) are located below the descending film distributor 24, while other deformations (obtained by the same process) are obtained above the distributor 24 and guarantee a correct position of the distributors 24 in each tube 25 ( see Fig.4a).

It can be noted that the devices 24 made available by the present invention and the distributor plate 23 guarantee a uniformly distributed flow between the various pipes and a uniform distribution around the circumference / internal wall of the various pipes, for the working solution (concentrated solution ) which enters the horizontal inlet distributor 21, from an inlet of the working fluid 22 in the absorber. All this increases the performance of the solar radiation cooling unit according to the present invention.

Use of the heat lost by the absorber

The absorption unit or absorber 5 constitutes a significant source of thermal energy lost by the refrigeration system, as it transmits an amount of energy corresponding to the evaporative cooling capacity and to the energy supplied by the thermal solar panels or by the reserve power supply (backup). In most cases, this amount of energy is transferred to the surrounding air, which acts as a cooling medium. The air flow (see arrows in Fig. 5) generated by a fan 30 which cools the absorber 5, is directed towards the rear part of the thermal solar panels 1 and therefore increases the efficiency of the thermal solar panels 1, as it reduces heat losses.

If this is convenient, the heat lost by the absorber can also be used to produce, for example, low temperature heating water for the production of hot tap water, for central heating or for other applications / uses.

In these cases, again according to the present invention and as shown in Fig. 5, the heat lost by the absorber 5 is collected using a coil 31 located inside the containment unit 7 (housing unit) under the € ™ absorber 5.

Management of the concentration of the working fluid

A further aspect of the present invention relates to monitoring the concentration of the working fluid. This aspect is also directly connected to the general performance and reliability of the solar energy cooling unit according to the present invention.

Indeed, some working fluids, for example lithium bromide in water, can be subject to the risk of crystallization in the absorber 5 and in the housing unit 7, and this can affect the performance and operation of the refrigeration system. .

The risk of crystallization is related to the concentration of the working fluid and the temperature of this fluid.

In a commercially attractive solar-powered cooling unit, where transmitters (sensors) can represent a significant cost component as well as a risk of leakage / leak in the system operating at substantially lower pressure than atmospheric conditions, it is preferable to reduce the number of transmitters that measure pressure, conductivity or other properties of the fluid.

The present invention applies a concentration management system based on non-invasive temperature transmitters, to control or limit the risk of crystallization.

For most working fluids, equilibrium data or diagrams are available, and Figure 6 is an example based on lithium bromide and water. (The term â € œequilibriumâ € refers to the substantially stationary conditions existing during a period of operation of the solar cooling unit, within a specific component such as the separator).

By measuring the outlet temperatures of the gaseous refrigerant and the outlet temperature of the working fluid in separator 2, the process control system (PCS) is able to determine the pressure in the separator 2 as well as the concentration.

With reference to Fig. 6, the temperature of the solution indicated on the x axis represents the outlet temperature of the working fluid from the separator, while the temperature of the refrigerant is measured as the temperature of the gaseous refrigerant.

By mapping the equilibrium diagram of Fig. 6 in a so-called look up table and applying the interpolation of the two temperatures, the process control system (PCS) will be able to calculate the pressure and concentration based on simple, non-invasive temperature transmitters. It has been verified that this methodology for determining the concentration of the working fluid and the pressure is essential for the manufacture of reliable refrigeration systems of considerable commercial interest, as it reduces the costs of instrumentation such as pressure transmitters, conductivity or other properties of fluids.

If the concentration of the working fluid increases, the risk of crystallization also increases. Based on the methodology described above for the calculation of the concentration, which uses temperature measurements, the process control system can intervene immediately to prevent crystallization. For the purposes of process control, a similar methodology can be applied to estimate or evaluate the evaporation pressure and concentration in the containment unit 7, using the same calculation procedure, this time based on the outlet temperature from the absorber 5 and on the evaporation temperature.

As an example, Fig. 6 shows, for the LiBr / H2O equilibrium diagram for a solution temperature of 70 ° C and for a gas refrigerant temperature of 40 ° C, a pressure of 75 kPa and a concentration equal to 53 % by weight of LiBr, at the orthogonal intersection point between the two dark lines starting from the two respective temperatures.

Evaporator configuration

The evaporator 6 of the solar energy refrigeration system according to the present invention is designed to suit the requirements of low pressure losses, which would significantly reduce performance and increase the areas / surfaces required for heat transfer and mass in the absorber (absorption unit).

The evaporator principle of the invention for the solar-powered refrigeration system is illustrated in figure 7.

Evaporator 6 produces chilled water and comprises an evaporator chamber 32 (or evaporation chamber) surrounded by a shell 33 occupied by chilled water. The gaseous refrigerant (refrigerant gas) coming from the separator 2 described above is condensed inside the condenser 4, thus producing liquid refrigerant at a pressure corresponding to the pressure existing in the separator 2. The reducing valve 34 between the condenser 4 and evaporator 6 allows the refrigerant to evaporate at low temperatures and could be designed in the form of an orifice, a capillary tube or a conventional reducing valve, controlled by the evaporation temperature The evaporator, the superheat temperature Ts superheat, and the evaporation pressure calculated by the process control system as described in the previous section.

The chilled water, in the evaporator 6, is in countercurrent with respect to the evaporator chamber 32 as it enters from the top, cooling the top of the evaporator chamber 32. The chilled water then flows around the evaporator chamber 32 towards the lower side, where the surface temperature is lower, thus leaving the evaporator 6 and heading towards the application / use (not shown) .

Inside the evaporator 6 shell 33, which contains the chilled water, it is important to obtain a satisfactory heat transfer coefficient to reduce the size and material consumption for this component. In order to achieve this objective, the chilled water is guided through a coil 35 (see Fig. 8) which guarantees a satisfactory speed of the fluid through the heat transfer surface 37 towards the evaporation chamber 32. This configuration a coil with integrated guides for chilled water is applied to both sides of evaporator 6 (above and below). Observe the representation of the coil 35 in the shell 36 of the evaporator, in Fig. 8.

Evaporator 6 is designed for low pressure losses as the absorption cycle operates at a low absolute pressure. An accidental increase in pressure between evaporator 6 and absorber 5 would lead to a reduced performance of the absorber. For this reason the evaporator is designed as an evaporation chamber 32 bearing a thin layer (not shown) of liquid refrigerant on the bottom of the chamber 32 itself. The film is obtained by increasing the surface roughness of the evaporator chamber 32 by increasing the heat transfer coefficient.

Since the outside of chamber 32 is surrounded by chilled water, the heat transferred from the chilled water to the refrigerant will cause the refrigerant to evaporate inside chamber 32. The entire internal surface of the chamber Evaporator 6, including the upper part of chamber 32, will be active in carrying out the cooling.

Note that chilled water flows around the lateral sides of chamber 32, without guides, to reduce pressure losses. This reduces the work required by the pumps due to pressure losses inside the upper and lower shells, while maintaining a good heat transfer coefficient towards the evaporator chamber.

It should be noted that the aspects of the present invention regarding the new absorber configuration and the new evaporator configuration could also be applied directly to a solar radiation cooling unit without a backup power source in the separator. In this case, the three-way valve 9 and the bypass duct 16 would be superfluous and the general architecture of the solar radiation cooling unit could be similar to that illustrated in Fig. 1 of application WO 2013/010549 A2 .

The detailed description provided above with reference to the accompanying drawings is not to be construed restrictively. Conversely, each innovative medium or feature that has been described could be protected (claimed) separately from the others or in combination with the others.

Important points / items

1. Solar radiation cooling unit for small applications / uses, for air conditioning and refrigeration in general, comprising: one or more thermal solar panels (1) for the collection of solar energy, through which can be fed a working solution consisting of an absorption medium and a refrigerant, to heat them during operation,

a separation means, connected to a first end of said one or more solar thermal panels (1), for separating a concentrated solution and a hot refrigerant vapor from the working solution which has been heated,

a condenser (4), connected downstream of the separation medium, to condense the hot refrigerant vapor in order to produce liquid refrigerant,

an evaporator (6) connected downstream of said condenser (4), to evaporate the refrigerant liquid coming from the condenser (4) and thus produce cold to be used directly or indirectly for said applications,

an absorption unit (5), connected downstream of the evaporator (6) to cause the absorption of the cold refrigerant vapor coming from the evaporator (6) in said concentrated solution coming from the separation medium,

a heat exchanger (3), connected between said absorption unit (5) and said separation means, on one side, and between a second end of said one or more thermal solar panels (1) and the absorption unit (5), on the other,

reduction valve means connected upstream of the evaporator (6) and of the absorption unit (5) respectively,

circulation means (8) to circulate the working solution inside the solar radiation cooling unit,

characterized in that it further comprises valve means (9) for selectively interrupting and re-establishing the flow of working solution through said one or more thermal solar panels (1), re-establishing or selectively interrupting at the same time the flow of working solution work through a bypass inlet (16) towards the separation medium, and by the fact that said separation means forms a separator (2) which includes protection means (14, 15) from splashes and droplets of working solution towards the condenser (4), and a backup energy source (13) that can be used to heat the working solution inside the separator (2) at least when solar radiation is absent.

2. Solar radiation cooling unit according to point 1, characterized in that it further comprises a process control system which selectively operates said valve means (9) and at the same time ensures that said one or more thermal solar panels (1) are filled with the working solution when the flow of working solution through said one or more solar thermal panels (1) is interrupted.

3. Solar radiation cooling unit according to point 1 or 2, characterized in that said absorption unit (5) comprises a container (21) substantially horizontal and of elongated shape, constituting an inlet distributor (21) for the work, equipped with a distributor plate (23), which ensures that said concentrated solution (22) coming from the separator (2) does not enter directly or form splashes in a plurality of substantially vertical tubes (25) of the absorption unit, and from the fact that the distributor plate (23) is located above the upper ends of said substantially vertical tubes (25) of the absorption unit, but below an inlet (22) for the concentrated solution.

4. Solar radiation cooling unit according to any one of the preceding points, characterized in that said absorption unit (5) comprises a container (21) substantially horizontal and of elongated shape, constituting an inlet distributor (21) for the work, equipped with an inlet (22) for the concentrated solution and a plurality of substantially vertical tubes (25) of the absorption unit, each tube (25) of the absorption unit carrying at least one distributor (24 ) of descending film formed by a sphere or by an analogous body, which occupies a substantial part of the cross section of the tube (25) so as to generate a film or a uniform layer of concentrated solution all around an internal wall of the relative tube (25) of the absorption unit; in which, each of said distributors (24) of descending film is held inside a tube (25) of the absorption unit by means of a positioning and holding device (27).

5. Solar radiation cooling unit according to point 4, characterized in that said positioning and holding device (27) comprises a plurality of deformations (27) located below and above the respective descending film distributor (24).

6. Solar radiation cooling unit according to any one of the preceding points, characterized in that said protection means (14, 15) against splashes and droplets of working solution comprise an anti-fog device (14) and a perforated protection (15) from splashes and droplets, the anti-fog device (14) preferably positioned adjacent to an outlet (12) of the hot refrigerant vapor and the perforated protection (15) from splashes and droplets being positioned above an inlet (11) of the working solution coming from said thermal solar panels (1), above a heating coil (13) constituting said reserve energy source, above an outlet (17) for the direct concentrated solution towards the absorption unit (5), as well as above said bypass inlet (16) to bypass said one or more thermal solar panels (1) when solar radiation is absent.

7. Solar radiation cooling unit according to any of the previous points, characterized by the fact that the absorption unit (5) also includes a containment unit (7) at its base, which forms a single unit with the previous one, and is in fluidic communication with the absorption unit (5) proper, and by the fact that a coil (31) arranged inside the containment unit (7) is used for recover part of the heat lost by the absorption unit.

8. Solar radiation cooling unit according to any of the previous points, characterized by the fact that a part of the lost heat, generated by the absorption unit (5), is recovered by a flow of air generated through the absorption (5) by a fan (30) and directed towards a rear side of said one or more thermal solar panels (1) to increase the efficiency of the thermal solar panels (1) by reducing heat losses.

9. Solar radiation cooling unit according to any of the preceding points, characterized in that a process control system of the cooling unit is used for one or more of the following purposes: a) obtaining the evaporation pressure, and the concentration of the absorption medium in the working solution inside the separator (2), starting from temperature values detected by means of temperature transmitters, for the hot refrigerant vapor and for the concentrated solution at their respective outlets ( 12 and 17) from the separator (2);

b) obtain the evaporation pressure, and the concentration of the absorption medium in the working solution inside the containment unit (7), on the basis of the temperature values that are detected by further temperature transmitters positioned at the Outlet of the actual absorption unit (5) and at the outlet of the evaporator respectively;

c) intervene with timely action when the concentration in cases a) and / or b) is too high and crystallization could occur in the absorption unit and in the containment unit;

d) controlling said reduction valve means connected upstream of the evaporator (6) and of the absorption unit (5), respectively, in which in the case of the reduction valve (34) connected upstream of the evaporator (6) the command can take place on the basis of the values assumed by the evaporation temperature, an overheating temperature, and an evaporation pressure inside the evaporator;

and by the fact that

in the previous cases a) and b), the process control system uses a reference table obtained from the mapping of a known equilibrium diagram, specific for the working solution that is used, and applies the interpolation of the values temperature measured.

10. Solar radiation cooling unit according to any of the previous points, characterized by the fact that the evaporator (6) comprises a completely enclosed evaporator chamber (32), i.e. surrounded by an evaporator shell (33) which contains the chilled water used for cooling applications / uses, this evaporator shell (33) comprising a lateral portion of the shell, an upper portion of the shell, and a lower portion of the shell, called upper and lower portions of the shell being in fluid communication with a chilled water inlet and a chilled water outlet respectively, and by the fact that inside the upper and lower portions of the shell, the chilled water it is driven at high speed within a respective coil of the upper shell and within a respective coil of the lower shell.

11. Solar radiation cooling unit according to point 10, characterized by the fact that the evaporator chamber (32) has a thin layer of liquid refrigerant at its base, obtained by accentuating the surface roughness of an internal wall of the evaporator chamber, and from the fact that said coils of the upper shell and respectively of the lower shell have the shape of spirals.

12. Solar radiation cooling unit according to any of the preceding points, characterized in that the working solution is an aqueous solution, preferably an aqueous solution of LiBr.

13. Separator (2) for solar radiation cooling units of the type of absorption refrigeration systems, characterized in that it comprises protection means (14, 15) to prevent splashes and droplets of working solution from heading towards a condenser (4) of the solar radiation cooling unit, and by the fact that it also includes a backup energy source (13) that can be used to heat the working solution inside the separator (2) at least when the solar radiation It is absent, and a bypass inlet (16) to bypass the solar thermal panels (1) of the cooling unit; said bypass inlet (16) and said reserve energy source (13) being arranged below said protection means (14, 15) from splashes and droplets of working solution.

14. Absorption unit, or absorber, for solar radiation cooling unit of the type of absorption refrigeration systems, characterized in that said absorption unit (5) comprises a substantially horizontal container of elongated shape (21) constituting a distributor inlet (21) of the working fluid, having a plurality of substantially vertical tubes (25) of the absorber, and by the fact that each tube (25) of the absorber has inside at least one descending film distributor (24 ) formed by a sphere or a similar body, which occupies a substantial portion of the cross section of the absorber tube (25), generating a film or a uniform thin layer of concentrated solution all around an internal wall of the relative absorber tube (25); and by the fact that the absorber can also include a distributor plate (23).

15. Solar radiation cooling unit according to any one of points 1 - 12, characterized in that said valve means (9) form a simple three-way valve (9).

16. Solar radiation cooling unit according to any one of points 1 - 12 and 15, characterized in that said reduction valve means can comprise a reduction valve, an orifice, or a capillary tube.

17. Solar radiation cooling unit according to any one of points 1 - 12 and 15 - 16, characterized in that said anti-fog device is a cylindrical roll of knitted material and said perforated protection (15) against splashes and droplets it constitutes a rigid material in the form of a perforated flat plate.

18. Evaporator (6) for solar radiation cooling units of the type of absorption refrigeration systems, characterized in that it comprises an evaporation chamber (32) completely enclosed, i.e. surrounded by a shell (33) of the evaporator containing the Chilled water used for cooling applications, the evaporator shell (33) comprising a lateral portion of the shell, an upper portion of the shell, and a lower portion of the shell, said upper and lower portions of the shell being in communication fluidics with a chilled water inlet and a chilled water outlet respectively, and by the fact that inside the upper and lower portions of the shell, the chilled water is driven at high speed within a respective coil of the upper portion of the shell and within a respective coil of the lower portion of the shell.

19. Evaporator according to point 18, characterized by the fact that the evaporator chamber (32) has a thin layer of liquid refrigerant at its base, obtained thanks to a greater surface roughness of an internal wall of the evaporator chamber, and by the fact that said coils of the upper and lower portions of the shell are spiral-shaped.

20. Evaporator (6) according to points 18 - 19, characterized in that said lateral portion of the shell is crossed by an inlet for the liquid refrigerant and said lower portion of the shell is crossed by an outlet for the cold refrigerant vapor.

21. Method for the operation of a solar radiation cooling unit, according to any of the previous points 1- 12 and 15 - 17, characterized by the fact that:

a) in a first position of the valve means (9) the working solution is made to flow inside the thermal solar panels (1) and

(i) the backup power source (13) is switched off when the solar radiation is sufficient to provide the nominal cooling capacity, or

(ii) the backup energy source (13) is activated to provide an additional amount of heat to reach the nominal cooling capacity, if the solar radiation is insufficient,

b) in a second position of the valve means (9), when the solar radiation is absent, the working solution is guided in such a way as to bypass the thermal solar panels (1) making it flow from the absorption unit (5) or from the containment unit (7) towards the heat exchanger (3), and then towards said bypass inlet (16) of the separator (2).

22. Method for the operation of a solar radiation cooling unit, according to point 21, characterized by the fact that a process control system ensures that the thermal solar panels (1) are filled with said solution or working fluid , when the operating mode is switched from an operation using the thermal solar panels (1) to an operation with a backup power supply, or in the event that operation starts using the reserve power supply.

Claims (14)

CLAIMS 1. Solar radiation cooling unit for small applications / uses, for air conditioning and refrigeration in general, comprising: one or more thermal solar panels (1) for the collection of solar energy, through which can be fed a working solution consisting of an absorption medium and a refrigerant, to heat them during operation, a separation means, connected to a first end of said one or more solar thermal panels (1), to separate a concentrated solution and a hot refrigerant vapor from the working solution which has been heated, a condenser (4), connected downstream of the separation medium, to condense the hot refrigerant vapor to produce liquid refrigerant, an evaporator (6) connected downstream of said condenser (4), to evaporate the refrigerant liquid coming from the condenser (4) and thus produce cold to be used directly or indirectly for said applications, an absorption unit (5), connected downstream of the evaporator (6) to cause the absorption of the cold refrigerant vapor coming from the evaporator (6) in said concentrated solution coming from the separation medium, a heat exchanger (3), connected between said absorption unit (5) and said separation means, on one side, and between a second end of said one or more thermal solar panels (1) and the absorption unit (5), on the other, reduction valve means connected upstream of the evaporator (6) and of the absorption unit (5) respectively, circulation means (8) to circulate the working solution inside the solar radiation cooling unit, characterized in that it further comprises valve means (9) for selectively interrupting and re-establishing the flow of working solution through said one or more thermal solar panels (1), re-establishing or selectively interrupting at the same time the flow of working solution through a bypass inlet (16) towards the separation means, and by the fact that said separation means forms a separator (2) which includes protection means (14, 15) from splashes and droplets of working solution towards the condenser (4), and a backup energy source (13) that can be used to heat the working solution inside the separator (2) at least when solar radiation is absent. 2. Solar radiation cooling unit according to claim 1, characterized in that it further comprises a process control system which selectively operates said valve means (9) and at the same time ensures that said one or more thermal solar panels (1) are filled with the working solution when the flow of working solution through said one or more solar thermal panels (1) is interrupted. 3. Solar radiation cooling unit according to claim 1 or 2, characterized in that said absorption unit (5) comprises a substantially horizontal and elongated container (21), constituting an inlet distributor (21) for the work, equipped with a distributor plate (23), which ensures that said concentrated solution (22) coming from the separator (2) does not enter directly or form splashes in a plurality of substantially vertical tubes (25) of the absorption unit, and from the fact that the distributor plate (23) is located above the upper ends of said substantially vertical tubes (25) of the absorption unit, but below an inlet (22) for the concentrated solution. 4. Solar radiation cooling unit according to any one of the preceding claims, characterized in that said absorption unit (5) comprises a substantially horizontal and elongated container (21), constituting an inlet distributor (21) for the work, equipped with an inlet (22) for the concentrated solution and a plurality of substantially vertical tubes (25) of the absorption unit, each tube (25) of the absorption unit carrying at least one distributor (24 ) of descending film formed by a sphere or by an analogous body, which occupies a substantial part of the cross section of the tube (25) so as to generate a film or a uniform layer of concentrated solution all around an internal wall of the relative tube (25) of the absorption unit; in which, each of said distributors (24) of descending film is held inside a tube (25) of the absorption unit by means of a positioning and holding device (27). 5. Solar radiation cooling unit according to claim 4, characterized in that said positioning and holding device (27) comprises a plurality of deformations (27) located below and above the respective descending film distributor (24). 6. Solar radiation cooling unit according to any one of the preceding claims, characterized in that said protection means (14, 15) against splashes and droplets of working solution comprise an anti-fog device (14) and a perforated protection (15) from splashes and droplets, the anti-fog device (14) preferably positioned adjacent to an outlet (12) of the hot refrigerant vapor and the perforated protection (15) from splashes and droplets being positioned above an inlet (11) of the working solution coming from said thermal solar panels (1), above a heating coil (13) constituting said reserve energy source, above an outlet (17) for the direct concentrated solution towards the absorption unit (5), as well as above said bypass inlet (16) to bypass said one or more thermal solar panels (1) when solar radiation is absent. 7. Solar radiation cooling unit according to any one of the preceding claims, characterized in that the absorption unit (5) also comprises a containment unit (7) at its base, which forms a single unit with the previous one, and is in fluidic communication with the absorption unit (5) proper, and by the fact that a coil (31) arranged inside the containment unit (7) is used for recover part of the heat lost by the absorption unit. 8. Solar radiation cooling unit according to any one of the preceding claims, characterized in that a part of the lost heat, generated by the absorption unit (5), is recovered by a flow of air generated through the absorption (5) by a fan (30) and directed towards a rear side of said one or more thermal solar panels (1) to increase the efficiency of the thermal solar panels (1) by reducing heat losses. Solar radiation cooling unit according to any one of the preceding claims, characterized in that a process control system of the cooling unit is used for one or more of the following purposes: a) obtain the evaporation pressure, and the concentration of the absorption medium in the working solution inside the separator (2), starting from temperature values detected by means of temperature transmitters, for the hot refrigerant vapor and for the concentrated solution at their respective outlets (12 and 17) from the separator (2); b) obtain the evaporation pressure, and the concentration of the absorption medium in the working solution inside the containment unit (7), on the basis of the temperature values that are detected by further temperature transmitters positioned at the Outlet of the actual absorption unit (5) and at the outlet of the evaporator respectively; c) intervene with timely action when the concentration in cases a) and / or b) is too high and crystallization could occur in the absorption unit and in the containment unit; d) controlling said reduction valve means connected upstream of the evaporator (6) and of the absorption unit (5), respectively, in which in the case of the reduction valve (34) connected upstream of the evaporator (6) the command can take place on the basis of the values assumed by the evaporation temperature, an overheating temperature, and an evaporation pressure inside the evaporator; and by the fact that in the previous cases a) and b), the process control system uses a reference table obtained from the mapping of a known equilibrium diagram, specific for the working solution that is used, and applies the interpolation of the values temperature measured. 10. Solar radiation cooling unit according to any one of the preceding claims, characterized in that the evaporator (6) comprises a completely enclosed evaporator chamber (32), i.e. surrounded by an evaporator shell (33) which contains the chilled water used for cooling applications / uses, this evaporator shell (33) comprising a lateral portion of the shell, an upper portion of the shell, and a lower portion of the shell, called upper and lower portions of the shell being in fluid communication with a chilled water inlet and a chilled water outlet respectively, and by the fact that inside the upper and lower portions of the shell, the chilled water it is driven at high speed within a respective coil of the upper shell and within a respective coil of the lower shell. 11. Solar radiation cooling unit according to claim 10, characterized in that the evaporator chamber (32) has a thin layer of liquid refrigerant at its base, obtained by accentuating the surface roughness of an internal wall of the evaporator chamber. 12. Solar radiation cooling unit according to any one of the preceding claims, characterized in that the working solution is an aqueous solution, preferably an aqueous solution of LiBr. 13. Separator (2) for solar radiation cooling units of the type of absorption refrigeration systems, characterized in that it comprises protection means (14, 15) to prevent splashes and droplets of working solution from heading towards a condenser (4) of the solar radiation cooling unit, and by the fact that it also includes a backup energy source (13) that can be used to heat the working solution inside the separator (2) at least when the solar radiation It is absent, and a bypass inlet (16) to bypass the solar thermal panels (1) of the cooling unit; said bypass inlet (16) and said reserve energy source (13) being arranged below said protection means (14, 15) from splashes and droplets of working solution. 14. Absorption unit, or absorber, for solar radiation cooling unit of the type of absorption refrigeration systems, characterized in that said absorption unit (5) comprises a substantially horizontal container of elongated shape (21) constituting a distributor inlet (21) of the working fluid, having a plurality of substantially vertical tubes (25) of the absorber, and by the fact that each tube (25) of the absorber has inside at least one descending film distributor (24 ) formed by a sphere or a similar body, which occupies a substantial portion of the cross section of the absorber tube (25), generating a film or a uniform thin layer of concentrated solution all around an internal wall of the relative absorber tube (25); and by the fact that the absorber can also include a distributor plate (23).