Patent Application
20140290305
The invention relates to a solar chiller. Although chillers consume a large amount of electrical current worldwide, so far solar cooling has not achieved a breakthrough. This is probably due to the complex requirements for such cooling machines:
The requirement A results in the fact that only a water-ammonia absorption chiller comes into consideration. From the requirements B and C follow the necessity to improve the solution concentrations used in the cooling cycle compared to the traditional ammonia-water absorption cycle. Claims D and E lead to operating the solution circulation movements also with thermal energy, since for this power range—especially for ammonia—there are only barely usable, durable and reasonably priced electric pumps. Requirement F applies not only to optimum efficiency by partially reusing the waste heat, but also to a construction design that is small, simple and suitable for mass production. Claim G results in the need for a kind of energy storage. The state of this technology is described in the sections 2.1. to 2.5. below.
The major concentration corrections in the ammonia-water absorption cycles occur at three different points of these cycles. Most frequently you will need ammonia as pure as possible for the evaporation in the cooling process (see 2.1.1.). But if you want to use the lowest possible heating temperature for the chiller (requirement B), the solution coming into the generator should have a very high concentration. If the back cooling temperature shall be very high (requirement C), the solution in the absorber must have a very low concentration. The latter two objectives are usually tackled jointly and are described in 2.1.2. and 2.1.3.
Not only ammonia vapor escapes the boiling water-ammonia solution but also water vapor. In the temperature range typical for absorption chillers the water content in the vapor is a few percent. So during the condensation of this vapor no pure ammonia is produced, but a highly concentrated ammonia solution. If cold shall be produced through evaporation of this liquid, it must be considered that this solution at a given pressure has a higher boiling point than pure ammonia. This means that the cooling temperature will be higher than expected.
To solve this problem many absorption chillers use rectifiers, which means that the mixed vapor from the boiler is led upward through a heat exchanger, where heat is removed at a temperature which must be higher than the condensation temperature, so the water condenses and will flow back into the boiler.
Rectifiers consume energy, space and create additional costs. Therefore, they are undesirable.
2.1.2. Two-Stage Machines with Associated Refrigeration System
A method to reach a very high generator solution concentration and to simultaneously achieve a very low concentration of absorber solution is to use two connected cycles, of which each has both a generator and an absorber. In the first cycle a relatively low concentration is used and the generator of the first cycle passes its ammonia vapor to the absorber of the second cycle, such that the second cycle gets a higher concentration. The second generator will then pass its vapor to the condenser, at which point the condensate enters the evaporator where the cooling effect takes place, and the resulting vapor passes back through the first absorber in the first cycle (see: AT 500935).
Another method to reach a very high generator solution concentration together with a very low absorber solution concentration is to continue boiling the solution coming from the generator at a lower pressure level and to bring the solution coming from the absorber in touch with this vapor before it is pumped into the generator. Thus a part of the ammonia does not circulate through the condenser and evaporator, but returns through a parallel path—the so called “bypass”—to the generator. Among others this method can be found in AT 506356. The total amount of ammonia, which evaporates and must be re-absorbed in this system without producing a cooling effect, is less than the two-step system described in 2.1.2., thus efficiency is better, as well. For details see http:/www.solarfrost.com/PDF/icebook.pdf.
The use of multi-level systems or the so-called bypass in combination with steam pumps is complicated and error-prone. In the two-step system, as well as with the bypass, parallel liquid streams have to be carried synchronously using two separate pumps. Unfortunately the pump performance of steam pumps can only be regulated poorly and with a rather large time delay. This leads to oscillation action—typical for reaction coupling that affects the efficiency of the system negatively.
Another type of automatic control of the parallel flows are electro-mechanical valves and/or float valves. Here, however, new wear parts come into play. It is difficult to integrate those components into the plate construction.
It is essential for every absorption chiller that solution is alternately heated and cooled again. Probably the easiest way is moving the solution back and forth between hot and cold zones. That works practically automatically from hot to cold, since the vapor pressure of a hot solution is bigger than that of a cold solution with a comparable concentration. But for the other way around, from cold to hot, work must be expended to move the solution. Most absorption chillers use mechanical pumps for this task. For machines with big output power, centrifugal pumps are used. For low power, it is a real problem to find cheap, efficient and durable mechanical pumps.
In the power range of interest, from 1 to 10 KW, the solution should therefore solely be moved by thermal energy. For this purpose there are steam pumps available. The type of absorption chiller for which these pumps shall be used must be distinguished. On the one hand, there are so-called diffusion-absorption cooling machines that use an inert auxiliary gas, mostly hydrogen, so that there is almost the same total pressure in the generator and the absorber, although the respective ammonia vapor pressure is very different. On the other hand, there are machines without auxiliary gas, where the pressure difference between the generator and absorber is some bar of pressure. In the first case, a simple bubble pump is sufficient for the thermally driven solution movement, similar to those steam pumps, which are known from filter coffee makers. In the second case, a different pump must be used to overcome a large pressure difference. It will be described in the following sections.
In principle, it seems logical to assume that it is very simple to move an ammonia-water solution by means of induced temperature differences, because its ammonia vapor pressure rises sharply when heated. So by heating this kind of solution, you can emit it from a vessel, and you may assume that by cooling it you can reach a corresponding suction. But this is possible only with some restrictions: Cooling off a motionless ammonia-water solution in a closed vessel, the pressure in the gas bubble on top of the solution reduces much less than what would be expected from the vapor pressure curve.
Although the cold solution absorbs ammonia vapor at the surface, it creates a thin floating boundary layer at high concentration, with a density much lower than that of the solution below it. Thus, a further absorption through the boundary layer is mostly prevented.
Any system in which an ammonia-water solution is circulated sustainably through heat, should also be able to absorb the vapor originated during the heating process. Generally special equipment is necessary for pressure reduction.
In general, one could define a pressure reducer as a device with which the ammonia-water solution is turned into a state where the ammonia vapor can simultaneously penetrate from the side or from below into the solution, so that no horizontal barrier can develop. This is to be accomplished, for example, by letting the solution flow through a gas chamber from top to bottom utilizing gravity.
You can also build a pressure reducer so that it is activated in a precisely defined moment. So it will be possible that a part of the solution periodically raises and lowers its pressure by several bar, which enables the construction of pumps without moving parts regardless of the utilized check valves.
Such steam pumps are found for example in WO03095844 A, AT500935 and AT504399.
In the classical water-ammonia chiller, usually a solution heat exchanger is installed between the hot generator and the cold absorber, so that the boiled out hot solution is carried from the generator in counter current to the enriched strong solution from the absorber. In this way, the already pre-heated solution enters the generator, and the absorber is fed with cold solution.
As important as this type of heat recovery is, it affects only a part of the amount of heat which is lost in most of the absorption chillers in the form of absorption heat.
In the ammonia-water absorption cooling process, almost exactly the same amount of heat that must be used for the evaporation process of the ammonia will be released again as waste heat during the subsequent absorption process. Both the heat necessary for expelling and the heat generated are not tied to a fixed temperature. Instead, the boiling temperature of the solution increases during expelling (for a fixed condensing pressure) steadily and in the same way the absorption temperature (for a fixed absorption pressure) decreases steadily. The temperature intervals for evaporation and for absorption overlap normally, so that a part of the resulting absorption heat can be used again for evaporation, which leads to a remarkable increase of the efficiency (COP) of such a machine.
It is important to point out that such an absorption heat recovery is only possible jointly and simultaneously with the mentioned solution heat exchange. When separating the generator from the absorber and with a solution heat exchanger in-between, then cold solution flows into the absorber and the absorption heat is generated at low temperature, which cannot be recycled for the generator process.
An example of such an absorption heat recovery can be found in: AT 504399. Here the liquid heating medium first gives off a big part of its heat in a generator, which is built as a high-performance heat exchanger in counter current to the ammonia-water solution, and then it receives a part of the absorption heat in an absorber, which is also built as a high-performance heat exchanger in counter current back to the solution.
The principle of absorption heat recovery described in AT 504399 fulfils the requirements, but not optimally, because the recycled heat is conducted through two separation layers, one from the absorber in the heating medium and one from the heating medium in the generator.
It would of course be better, to pass the warmer part of the absorber heat directly through a single high-performance heat exchanger to the cooler part of the generator. In doing so it is difficult to guarantee the required counter-current: As the boiled solution of the generator is specifically heavier than the highly concentrated inflowing solution, it is advantageous if the solution in the generator flows from the top down and if it releases the resulting vapor continuously during this process. But, on the other hand, it is easier on the absorber if its solution is flowing from top to bottom just like in a pressure reducer. Therefore, due to this, a heat exchanger in counter-current is excluded.
The task of the generator is to provide heat to the solution, so that ammonia can evaporate. Usually this is a vessel, which is continuously fed with the solution and heat, while also continuously creating a boiled solution and the steam flow off. If the generator is used together with a steam pump, one could theoretically speak of a periodically repeated batch process, because the pump strokes of the steam pump last typically from one to several minutes. But it does not make sense to go off the definition of continuity in such a case, because the generator pressure and also the emission of vapor and the boiled solution almost remain constant. This is not the case in the present invention (see below). So, as a real batch process, it is different to such quasi-continuous systems.
The task of the absorber is to recirculate the ammonia vapor coming from the evaporator to the boiled solution in the generator and to dissolve this ammonia vapor in it. For this purpose the resulting solution heat must be withdrawn from the absorber. As in the classical ammonia water chillers, this may be achieved in such a way that the weak solution in an ammonia atmosphere trickles down pipes that are cooled from the inside or with the “falling-film” method where it runs in a vertical tube along the pipe wall that is cooled from the outside. The efficiency of the falling-film process can be increased by inserting a wire spiral fitting to the inner wall of the pipe.
In both cases the procedure of the pressure reducer defined in 2.2.1 is utilized. Both methods also imply a consistent cooling temperature for the absorption process. They are therefore not suitable for an absorption heat recovery. Absorption heat can only be effectively obtained if the absorption process takes place at a constant pressure and with continuous and steady cooling of the solution, with a simultaneous increase of the concentration.
Due to the problem of the pressure decrease in AT 504399, the high-performance heat exchanger for heat recovery was built as a tightly wound coil through which both the weak solution and the ammonia vapor were passed together, so that the two media could mix directly in the narrow tube coils and were able to dissolve into each other.
One of the biggest problems of absorption chillers compared to compression cooling is their relative size and resulting high cost. The problem is similar to chemical reactor building. Therefore in AT506358, a system consisting of flat plates was proposed, which could reduce the size of absorption chillers significantly. If we translate the design principle of a conventional ammonia-water absorption refrigeration machine in the form of such a plate pack with the same power, this results in only about 3% of its original volume.
A plate system as described in AT506358 is only feasible with some restriction for ammonia water absorption cooling machines. The main problem with ammonia is that the system must be completely tight under all possible conditions. This refers not only to the density for the outside but also to the inside of the system, between the constructed parts with different operating pressures. Following the principles of plate systems in an absorption cooling machine, there are usually zones with different operating pressures in direct vicinity to one other on the same plate.
Brazed plates typically withstand a pressure of up to 15 bar, and glued boards are even worse. Yet the operating pressure in ammonia-water chillers can be considerably higher—especially in hot climates (higher condenser temperature). Even if such a pack of plates, as proposed in AT506358, is pressed between thick outer plates at the borders, it can not be avoided that in the central section the plates are not tight, because inside a chiller of the typical size, the total force caused by the pressure is too strong. Especially if elastic plates are used in the pack of plates, small plate deformations occur—mainly due to the fact that the plates are not of a consistent shape, so that in the central section tiny divergences of the plates are inevitable.
Another possibility to connect the plates is welding. As there are different pressure zones on each plate in such a plate package, the weld must be made not only at the plate borders but almost in the whole area, which is expensive and would only be profitable for very large numbers.
A further problem is the heat transfer within the pack of plates. If such a pack is welded completely, it can not have insulation plates.
If the entire refrigeration unit is placed in a single block, which would be desirable, there will be hot and cold zones next to each other. The resulting thermal bridges would reduce the thermal efficiency of the machine remarkably.
The problem to use solar energy even if there is no sun is solved in most cases by thermally insulated hot water tanks or in some cases by latent heat storage. In any case, such a system increases the volume, the cost, and particularly the time and effort for the installation of a solar system considerably.
In comparing the requirements for an ideal solar cooling machine with the current state of the art, one derives the list of tasks of the present invention:
It should be noted that the invention shall not to be realized through a sequence of components where each component stands for a particular task, as it happens in conventional plant construction, but through a simple and homogeneous system, in which the various functions result out of the same basic idea and its design.
The tasks to build a single-stage ammonia-water absorption chiller with low heating temperature, high back cooling temperature and low cooling temperature, in a batch process without solution pump and without rectification, where all steps of the solution concentration optimization take place in the generator, is achieved in the invention by combining the generator together with a back-cooled input vessel and the pressure reducer in one structural and pressure unit, in which the pressure reducer lowers the generator pressure below the absorber pressure at the start of each working cycle, and from there solution flows through a check valve in the back cooled generator input vessel, fills it and from there, following gravity, the solution flows gradually into a hot zone, which advantageously but not necessarily can consist of an absorber preheated zone and an externally heated hot zone, which produces ammonia vapor, which is passed by a siphon pipe from below through the still in the generator input vessel where the remaining solution is located and where from the upper end of this generator input vessel a gas line leads through a check valve to the condenser, while the boiled solution coming from the hot zone is passed through the pressure reducer and through a check valve and a pressure reduction stage to the absorber.
The task that the batch process runs automatically without external control or regulation and shall be repeated periodically, is inventively achieved by connecting the cooled generator input vessel to three siphon systems:
Siphon or lifter, consisting of a narrow pipe leading from the bottom of the input vessel up to maximum height of fill of this vessel, there again turns downward and empties below the input vessel, and in a small vessel to the upper side, the vented reservoir empties. From this reservoir a tight pipe, in which a regulating element may be integrated, leads into the heated generator zone below it.
Siphon or lifter, consisting of a pipe which leads from the upper part of the heated generator zone upward to above the top of the cooled input vessel, there again turns down and leads to the bottom of the cooled input vessel into which it empties.
Siphon or lifter, consisting of a pipe leading from the upper part of the cooled input vessel down to the entrance of the hot zone of the generator, where it empties into a small reservoir.
The task of building a pressure reducer, which is activated at the end of the cycle by changing from solution to gas and which, once the generator has absorbed enough solution, interrupts the action of pressure reducing, can inventively be solved by two re-cooled vessels, one on top of the other, that are connected by two or more pipes or siphons, where during the generator process, the way of the solution with respect to the gas goes from the lower to the upper vessel and from there through a check valve to the absorber. Based on this idea various construction methods can be found for the pressure reducer:
1. The upper and lower vessel are connected by two pipes to each other, where the first pipe connects the bottom of the upper vessel to the bottom of the lower vessel and the second pipe, starting from the top of the lower container, first leads down, then just above the bottom of the lower container, turns up and then empties into the floor area of the upper container.
2. Like the first version, except that a third pipe is added, which branches off in about the middle of the downward leading part of the second pipe and leads up, then in the top of the lower vessel turns downwards and empties into the lower part of the upper vessel leading part of the second pipe.
3. Like the first or the second version, but in this case the first pipe does not empty directly into the bottom of the lower vessel but forms a U-tube below this vessel. The apex of the tube must be the deepest point of the whole pressure reducer. The second pipe is interrupted by a control valve in its upward moving part. Furthermore there is a second check valve, parallel to the first one at the upper outlet of the upper vessel in the flow direction to the absorber, supplied by two parallel tributaries namely a fourth and a fifth pipe, where the fourth pipe leads from the bottom of the lower vessel directly upward to the second check valve, while the fifth pipe, starting from shortly above the bottom of the lower vessel, first descends, then shortly above the bottom of the lower vessel turns up and then also leads to the second check valve.
4.4. Absorber with Upward Flowing Solution and with Outlet Reservoir
The task to build an absorber with upward flowing solution for absorption heat recovery is achieved by an absorber consisting of two sections and an outlet reservoir, where in the first section hot, weakly concentrated solution flows upward and at the same time ammonia vapor is absorbed and releases the resulting heat to the preheating zone of the generator. Then the cooled solution reaches a second section above the first one, which is cooled from the outside, where the solution flows downward following gravity. From the cold section, the solution runs down to the bottom of a solution reservoir below it, which is back-cooled by a liquid medium.
4.5. Absorber Outlet Vessel with Starter
The task of the thermal start device is inventively achieved in such a way that at the inflow of back cooling medium to the cooling jacket of the absorber outlet reservoir, there is a three-way valve which allows to send a hot medium temporary through the cooling jacket, which is connected to this solution storage.
The task to recover a big part of the resulting waste heat is achieved inventively with two methods which complement each other.
1. Since the pressure reducer only functions with the cold solution, but heat recovery from the absorber is only possible when the hot solution with generator temperature flows into the absorber, one element of the pressure reducer is a heat exchanger. The hot solution coming from the generator is led to its primary side and cooled down, and on its secondary side, the solution flowing from the pressure reducer to the absorber is heated up again.
2. The hot zone of the generator has a preheating zone, in which the evaporation can take place, where heat from the hot part of the absorber is absorbed, and an actual heating zone, where heat is provided from the outside. For absorption heat recovery, the hot zone of the absorber converts to the primary side of the heat exchanger while the preheating zone of the generator serves as the secondary side of it.
An external heat storage can inventively be avoided, by integrating a reservoir with a lockable exit to the condenser exit in front of the valve, which leads the liquid ammonia to the evaporator. A second storage vessel, where in- and outflow also must be lockable, will be placed between the pressure reducer stage between generator and absorber and the actual absorber. The local position of this second storage vessel shall be above the absorber. This second vessel will be connected to the absorber outlet vessel by a ventilation pipe, so that both vessels hold the same pressure.
4.8. Construction with Hydraulic Pressure Cushion and Moulding Plates with Protruding Sealing Elements
A small, inexpensive, pressure-tight construction without thermal bridges which is suitable for this cooling machine inventively consist of a pack of moulding plates placed alternately one after the other, made of an elastic sealing material, with holes and canal-like cut-outs, and which serve for the conduction of liquids or gases, and dividing plates made of sheet metal, in which holes are drilled for the conduction of liquids and gases crosswise to the plate level. The pack of plates is pressed together with screws, clamps or other mechanics methods, in a way that between every two moulding plates there is one diving plate and between every two dividing plates there is one moulding plate, with an exception that in an optional place of the pack of plates there is a hydraulic pressure cushion instead of the moulding plate between two dividing plates, which consists of an elastic sealing stripe, which is pinched glued at the plate borders between these two dividing plates, so that between these two dividing plates that are fixed together, a hydraulic liquid or a bonding liquid resin can be filled in with high pressure. Furthermore in the whole pack of plates there are different pressure zones on each moulding plate which are separated from each other by linear, elastic sealing elements protruding out of the plate level, which can be done either by gluing elastic sealing stripes on each moulding plate or by cutting out narrow canals on each moulding plate along the lines which are designed for sealing, into which sealing strings are placed. In this pack plate, the components of the cooling machine are arranged in such a way that the hot part of the generator is on the lowermost place in the pack, above which there is the heat exchanger for the heat recovery, where the temperature runs from the bottom to the top from hot to cold, above which follow the back cooled parts of the absorber, the generator and the pressure reducer, and at the top there is the cold evaporator, where at the border between the back cooled zone and the cold evaporator zone holes are cut in the metal dividing plates and outer plates, which only leave narrow connection bridges on those places where it is necessary for the solidness of the construction with respect to where canals in the moulding plats connect the evaporator with the rest of the cooling machine.
The construction of the solar cooling machine in the form of a single stage ammonia-water absorption chiller heated and re-cooled by liquids in a batch process without solution pump and without rectification, consisting of an absorber, a condenser, an evaporator and a generator, which contains an automatic solution concentration optimization and a pressure reducer, which allows it to absorb solution automatically, to process it and then press it into the absorber, has the effect, that at each cycle from the absorber a portion of solution of medium concentration is absorbed, where the first part of this solution begins to boil at very low pressure as soon as it reaches the hot generator zone, because the resulting ammonia vapor is immediately absorbed by the remainder of the cold solution, which is still in the input vessel. In this phase of the process the concentration in this input vessel rises slowly, and thus also the pressure in the generator, while at the same time solution from this vessel flows into the hot zone. Since this solution in this process boils at a low pressure, its final concentration is lower than in a solution, which would have been boiled at full condensator pressure and at the same temperature. In the further course of the process, the generator pressure rises to the level of the condenser pressure and then the meanwhile highly concentrated solution comes from the input vessel to the hot zone. Because of its high concentration, it can also evaporate ammonia at a relatively high condenser pressure (e.g. at a high ambient temperature of the machine), which is then used for cooling, even if the generator heating temperature not very high. The concentration of the boiled solution is at the end of the process slightly higher than at the beginning, but on average, the concentration of the solution provided for the absorber is significantly lower than without the passage of the generator vapor through the cooled input vessel. Consequently, the cooling temperature of this cooling machine is lower than without this invention. Since the entire ammonia vapor is passed through the back cooled input vessel, the steam going from the generator to the condenser is cold and contains only very small amounts of water vapor, so a rectifier is not necessary in this case. It should be noted that the non-absorbable ammonia vapor can not condense in the back cooled input vessel, because its temperature is always a few degrees above the condensation temperature due to the absorption heat released there. Directing the boiled solution through the pressure reducer is done due to the following reason: a pressure reducer that activates after each terminated generator process, must be triggered by the change, if not solution but gas is transported. As in this course, weak solution shall absorb the excess gas from the generator, it is advantageous to use the boiled solution of the generator for this purpose. It follows that the exit path of the generator to the absorber has to run directly through the pressure reducer, because only in this manner can it be ensured that the solution in the pressure reducer is renewed after each cycle.
The three siphon systems, with which the cooled generator input vessel is connected, show the following the effects:
1. The first siphon or lifter is used to allow an evacuation of the generator input vessel in the direction of the heated generator zone only when this vessel is full as a result of the generator absorber process, because while the generator absorbs solution, the solution which is already in the generator may not yet be heated, because this would interrupt the absorber process. As this siphon pipe must be very thin to allow the flow of liquid towards the hot zone on the one hand and to limit it on the other hand, there is the risk like with any liquid lift with a very small, that gas bubbles are stuck in the down-stream after the apex of the siphon which impede the flow. The vented reservoir and the fact that the lifter tube constricts just below this reservoir serve to avoid this effect. Once the input vessel has filled in the absorber process, solution passes through the apex of the siphon so quickly into the vented reservoir that all gas bubbles are swept from the upper part of the lifter such that the lifter is fully functional. The flow of the siphon is limited by the narrower channel only below the reservoir.
2. The second siphon or lifter is used to carry the ammonia gas produced in the heated zone from below through the input vessel, but at the same time it prevents the solution from passing directly in this way into the heated zone, whereby the first siphon would be short-circuited.
3. The third siphon or lifter is used for absorbing gas from above the input vessel during the absorber phase of the pressure reducer, so that no solution remainders can pass in the heated zone during this phase. At the same time, this siphon must prevent the ammonia gas produced in the heated zone from spilling from the top into the input vessel. This is achieved by the small solution reservoir at the entrance to the heated zone of the generator: The gas pressure of the heated zone presses from above on the liquid of this solution reservoir and lets solution rise up in the channel of the third siphon, until the resulting hydraulic pressure is as high as the pressure that counteracts the second siphon if it is to carry gas below the solution in the cooled input vessel.
All pressure reducers of the three described types, especially in the first version, have the effect that as soon as the solution flow from the generator is stopped and the generator discharges only gas, a large gas bubble forms first in the lower vessel and then the solution of the upper vessel empties into the bottom vessel, where a turbulence between solution and gas happens, which absorbs the excess gas from the generator. Once it has again absorbed solution from the generator, this solution runs through the hot generator zone and closes shortly afterwards the access to the pressure reducer, such that new solution from the bottom now enters and fills the two vessels.
In the second version of the pressure reducer, the effect of the third pipe is that the absorption process of the pressure reducer is stopped faster after refilling the generator input vessel with solution, which reduces the cycle time, thus increasing the specific power of the machine per volume.
In the third version of the pressure reducer the effect of the fourth and fifth line and the second check valve is that, after the formation of the gas bubble in the lower vessel, the pressure reducer does not immediately allow the flow of solution from the upper to the lower vessel, but first lets most of the excess gas from the generator directly pull off into the absorber and only then absorbs the rest of the gas.
While the first two versions of pressure reducers depending on their dimensions are only suitable for certain ambient- and heating temperatures, the third version can be used for all possible cases.
5.4. Absorber with Upwards Streaming Solution and with Exit Vessel
The construction of the absorber consisting of two sections, a hot one with solution flowing upward and a cold one with solution flowing downward, has the following effects: Due to the falling solution, a vacuum is created in the entire cold section that absorbs the ammonia vapor coming from the evaporator and the hot solution through the hot section upwards. The final back-cooled absorber output reservoir, where in the bottom side cold solution and any unabsorbed gas from the second section of the absorber flow, strengthens this effect. The hot, upwardly flowing and gas absorbing solution in the first section (exothermic process) runs in counter current to the generator solution, which following gravity flows through the hot zone of the generator and produces vapor (endothermic process). Thus, this particular design of the absorber allows the use of a counter current heat exchanger, which gives out a part of the resulting absorption heat to the generator.
In the absorber exit reservoir, the solution accumulates before it is absorbed through a check valve by the generator.
5.5. Absorber Exit Vessel with Starter
Since the machine has no autonomous solution pump, there is a risk that it will not start by itself when turning on the heater, because there is just not enough solution in the generator. The three-way valve, through which briefly hot medium can be passed to the cooling jacket of the absorber outlet vessel, allows to increase the pressure in the absorber output reservoir, so that solution is pressed into the generator, and subsequently the machine starts.
If the boiled solution from the generator is used to reduce the pressure, it must first be cooled. The heat which has to be withdrawn for it should be returned to the system. The heat exchanger, where on the primary side hot solution of the generator is cooled and on the secondary side the solution flowing from the pressure to the absorber reducer is warmed, has the effect that only cold solution is provided to the pressure reducer, which is required for the absorption of the remaining gas from the generator, but that nevertheless only hot solution with low concentration is provided to the absorber, so that the absorption process can take place there at the respective highest possible temperature, so this absorption heat can be returned from the hot part of the absorber to preheating zone of the generator.
5.7. Design of Plates with Hydraulic Pressure Cushion
The design of the machine with plates with a hydraulic pressure cushion has the effect that in the places, where at a moulding plate the adjacent moulding plates have analogue bridges at the corresponding positions, there is always the contact pressure necessary for sealing, even if the overall pressure of the unit is so big that the outer plates slightly bow outward in the centre. But at the plate positions where the adjacent moulding plate with another moulding plate do not have the same bridge assembly or where with the same bridge assembly different pressure zones occur between two moulding plates, slight bending of the intermediate dividing plates has to be expected (see
The inventive energy storage has the effect that even in times when there is no sun, it can be cooled, if in the sunshine phases enough weak concentrated solution and enough liquid ammonia were formed. You can always let the weak solution flow into the absorber and let ammonia flow in through the evaporator from the condensor exit tank. Then you can cool as long as the supplies last. The resulting highly concentrated solution is stored in the absorber exit tank until the next availability of sunshine. An additional effect is that when the cooling system uses the storage for ammonia and weak solution, the cooling effect occurs immediately, while an ammonia-water absorption cooling machine without this facility usually takes a long time until the cooling effect can be noticed.
The numbers in the drawings relate to the following terms:
You see a generator -1- with input vessel -3- and pressure reducer -29-, an absorber -14- with absorber output vessel -21-, a condenser -25 and an evaporator -24-. The arrows show the main flow direction of solution with respect to gas. Heating- and cooling media are not drawn in
Each process cycle starts with the filling of the generator input vessel -3- with highly concentrated solution from the absorber output vessel -21-, which is absorbed by the input check valve -2-, as soon as the generator pressure is lower than the absorber pressure. While the level of the solution in the generator input vessel -3- rises, it also rises in the first siphon or lifter -4-. As soon as the liquid level has reached the upper apex of the lifter -4-, firstly because of the gas resistance in the lifter pipe -4- only a small streamlet runs in the reservoir -5-, but thereby carries gas along, which accelerates the flow of the solution, so that it quickly fills the reservoir -5-, where the gas flows over the ventilation -6- back in the input vessel -3-. From the reservoir -5- the solution then slowly flows through a narrow connection canal -7-into the heated generator -1- . There the solution heats up to boiling and in this way evaporates ammonia, which is connected by the vapor tubes -13- and the second siphon or lifter -8- with the input vessel -3-. The ammonia vapor then bubbles from below through the cold solution, which is still in the input vessel -3-, at which in the starting phase of the cycle this vapor is completely absorbed in the solution. So the concentration rises and thus also the pressure in the generator system -1- and due to the connection with the check valve -27- also in the condenser -25. As soon as the process of liquefying of ammonia starts in the condenser -25-, no more ammonia is absorbed in the condenser input vessel -3-, since the solution is already saturated under these conditions. Additional ammonia vapor will therefore be completely passed on to the condenser -25-.
During this process solution runs from the input vessel -3-, through the lifter -4-, through the reservoir -5-, through the connection canal -7- and then through the solutions reservoir -10- to the entrance of the hot zone of the generator -1- where the solution boils off the majority of its ammonia, to the input -30- of the back cooled pressure reducers -29-, which is placed in the upper part of the vessel -32-. Usually both vessels -32- and -33- are filled with cold weakly concentrated solution. The hot solution flowing in through the input -30- cools down quickly. It then flows from the lower vessel -32- through the two pipes -34- and -36-into the upper vessel -33- and from there through the check valve -40- and the regulation valve -17- to the absorber -14-. As soon the entire solution from the input vessel -3- and the generator -1- is used, gas runs in the lower vessel -32- in place of the solution. A gas bubble forms in the lower vessel -32- and the solution level drops, while the solution is displaced through the pipe -34- in the upper vessel -33-. At the same time the solution level drops in the limbs of the siphon-pipe -36- which opens to the lower vessel -32-. As this part of the solution is connected hydrostatical with the solution in the lower vessel -32- with the deviation through the upper vessel -33-, the solution level in the pipe -36- and in the lower vessel -32- are always on the same level during this process of displacing, until the lower extreme point of the pipe -36- is reached. At this point—we call this the activation of the pressure reducers—gas enters upwards to the upper vessel -33- flowing limb of the pipe -36- and reaches the bottom of the upper vessel -33-. Following the drop of hydrostatic pressure, solution now flows from the upper vessel -33- through the pipe -34- in the lower vessel -32- and, in doing so, absorbs gas through the pipe -36- upwards. But as this gas is absorbed immediately in the cold solution of the vessel -33- (because it comes from below), the pressure in the pressure reducer -29- drops very quickly. The absorption effect transmits itself over siphon or lifter -9 in the generator input vessel -3-, so that new solution is absorbed. The check valve -40-impedes, then that solution from the absorber -14- is absorbed in the pressure reducer -29-. Through the check valve -40- and the regulation valve -17-, the weakly concentrated solution runs into the absorber -14-. In this simplest version of the machine, the flow direction in the absorber is always downward, following gravity. In the back cooled absorber -14-, the solution absorbs the ammonia vapor coming through the check valve -15-, after its condensation in the condenser -25- through the choke or pressure stage -26- has reached the evaporator -24- and there again is turned to gas, which results in the desired cooling effect.
a shows a pressure reducer in its simplest version. It consists of a lower -32- and an upper vessel -33-. Solution or gas is supplied at the input -30-, where it is advantageous, when the opening of this supply pipe is placed in the upper section of the vessel -32-. Normally, both vessels -32- and 33- are filled with cold weakly concentrated solution, where the solution from the lower vessel -32- flows through both pipes -34- and 36-into the upper vessel -33-, and from there through the check valve -40- to the output -31-. As soon as gas flows to the place of the solution in the lower vessel -32-, a gas bubble forms there and the solution level in the lower vessel -32- drops, while the solution through the pipe -34- in the upper vessel -33- is displaced. At the same time the solution level in the limb of the siphon-pipe -36- drops, which opens in the direction of the lower vessel -32-. As this part of the solution is connected hydrostatically to the solution in the lower vessel -32- via a deviation through the upper vessel -33-, the solution level in the pipe -36- and in the lower vessel -32- are always on the same level during this process of displacing, until the lowest point in the pipe -36- is reached. At this moment, gas enters upwards to the upper vessel -33-flowing limb of the pipe -36- and reaches the lower part of the upper vessel -33-. Following the drop in hydrostatic pressure, solution now flows from the upper vessel -33- through the pipe -34- in the lower vessel -32- and absorbs gas through the pipe -35- upwards. But, since this gas is absorbed immediately in the cold solution of the upper vessel -33- (because it comes from below), the pressure in the pressure reducer -29- drops very quickly.
b shows a pressure reducer, which is to a large extent identical with
c shows a pressure reducer, which is a further development of the simplest version (
Meanwhile, the liquid level in pipe -36- also drops to its lower apex, which is the literal activation of the process of pressure reduction. Since the main part of the gas has already passed off to the absorber, this process of pressure reduction now is remarkably quicker and more efficient.
The heat exchanger -62- serves to give the absorption heat from the warm part -18 of the absorbers to the preheating zone of the generator -11-.
The heat exchanger -63- serves to cool the hot solution, coming from the heated zone -12- of the generator and flowing to the pressure reducer -29-, and heat it up again after it makes its way through the pressure reducer -29-.
From the outside (not visible in the drawing), the pack of plates -50- is certainly wrapped in a layer of thermal insulation.
In the front on the pack of plates -50-, an outer plate -43- can be seen, which is thicker than the other plates. Like all other plates, it has screw holes -51- in the screwed version, so that with the relevant screws (not drawn), the necessary first installation pressure can be established. Furthermore, there are plate openings -53- in the area of the thermal insulation zone -57-. The pack of plates -50- is shown in two disassembled parts, where, in between, an example of an entire moulding plate -44- and an example of a dividing plate -49- can be seen. Different parts of the machine concept (see
On the representational drawing, the moulding plate -44- shows a part of the evaporator -24-, the upper vessel -33- and the lower vessel -32- of the pressure reducer -29-, a part of the heat exchanger -63- and a part of the heated generator zone -12-. The pressure reducer zone -29- is surrounded by a linear sealing -46-. The same applies for the transition holes -52- of the moulding plate -44-. The moulding plate -44- does not have plate openings -53-, as it is made of only poorly heat conductive material, whereas the dividing plate -49- has such plate openings -53-, as it is made of metal.
The lines A-B mark a cut which is displayed in
a, b, c, d all show the same detail from a pack of plates -50- along the cutting line A-B in
a shows a detail of 3 different dividing plates -49-, with moulding plates -44, 45- in-between. As the depicted cut is orthogonal to the plate level, you only see the crosscut bridges -45- from the moulding plates -44-. The cut face of dividing plates -49- appears as a vertical line. However, it is an idealized depiction, which is only then nearly correct, when there is the same pressure in all remaining spaces between the depicted moulding plate bridges -45-.
b shows the same detail as
c shows the same detail as
d also shows the same detail as
| Number | Date | Country | Kind |
|---|---|---|---|
| A 410/2011 | Mar 2011 | AT | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AT2012/000065 | 3/16/2012 | WO | 00 | 6/19/2014 |
