KR20010005554A - Improved control for absorption chillers - Google Patents

Abstract

In the first embodiment, the absorption chiller comprises a generator 26 and an absorber 24 and has at least one absorbing solution flow flowing from the generator 26 to the absorber 24. Separated flow of absorbent solution is distributed to surface contact 24a and reservoir 24c of absorber 24. The capacity of the chiller can be controlled by varying the ratio of absorbent solution flowing into the reservoir to the surface contact 24a of the absorber 24. The controller 118 adjusts the flow ratio of the absorbent solution to achieve the required cooling capacity. In the second embodiment, a crystallization detection and recovery method of the two-phase absorption chiller 400 is provided. Crystallization in the cold heat exchanger 426 is detected by a temperature comparison between these absorbing solution streams. The recovery sequence includes removing crystallization and preventing a series of occurrences. Finally, in a third embodiment, a control system 500 is provided that controls overshoot in response to the setpoint input 515 for the control system 500. The control system 500 receives a feedback loop 505 connected to the control system 500 via a synthesis node 508 and a setpoint input 515 and is filtered through the aggregation node 508 to the control system. And a two-name filter 310 arranged to provide a point output value 520.

Description

Control unit for absorption chiller {IMPROVED CONTROL FOR ABSORPTION CHILLERS}

Related devices using absorption refrigerants, cooling, heat pumps, and complex refrigerants circulated through a refrigeration loop are well known. The cooling loop includes a generator, a condenser, an evaporator and an absorber. Various complex cooling systems can be used in such devices. Examples include ammonia / water systems and lithium bromite / water systems.

The external energy source heats the absorbing solution and the complex refrigerant in the generator. The generator distills off the vapors of many volatile refrigerants (e.g., ammonia vapors for ammonia / water refrigerants and water for lithium bromide / water systems), leaving behind a weakly volatile concentrated absorbent solution. The concentrated absorbent component is removed by an absorber.

The condenser receives the vaporized refrigerant from the generator and condenses it in liquid form. Heat released by condensation of steam is rejected by cooling towers, cooling water, other external heat sinks, or other cooling devices.

The evaporator recovers heat from the heat load (ie, building air, cooler content, coolant, or other liquid or object the system is trying to cool) by evaporating the condensed liquid refrigerant in direct or indirect contact with the heat load.

The absorber contacts the refrigerant vapor leaving the evaporator with the condensation absorption solution leaving the generator. This contact process generates heat when the vapor is reabsorbed into a less volatile solution. This heat is rejected by cooling towers, cooling water, other external heatsinks, or other cooling devices. The original complex refrigerant and absorbent solution are reformed in the absorber and then returned to the generator to complete the cycle.

In a conventional absorption heat exchanger, the evaporator and absorber are located in a single vessel, so that the refrigerant vapor generated in the evaporator can easily pass through the absorber for resorption. In a typical apparatus in which an evaporator and an absorber are combined, the contacting process includes spraying the condensed absorbent solution in contact with the refrigerant vapor. Treatment of the condensation solution at low temperatures produces saturated vapor pressure in the absorber, which pressure is slightly lower than the saturation pressure in the evaporator. Pressure equilibrium causes refrigerant vapor to flow from the evaporator to the absorber and reabsorb into the solution. Chiller cooling capacity is directly related to the rate at which evaporated refrigerant flows from the evaporator to the absorber since it is a function of the rate at which the refrigerant evaporates in the evaporator.

The cooling capacity of the absorption chiller is preferably changed to accommodate the change in load applied to the chiller. The most common method of controlling the cooling capacity is to change the concentration of the absorbent solution injected into the absorber at a constant rate. Increasing the concentration of the absorbent solution in the absorber spray results in significant pressure equilibrium in the absorber, allowing more cooling vapor to flow from the evaporator to the absorber, thus increasing the cooling capacity as the refrigerant evaporates at a high rate in the evaporator. Conversely, decreasing the concentration of the absorbent solution in the absorber spray reduces the cooling capacity.

The absorbent solution concentration in the absorber spray is varied by changing the flow rate of the concentrated absorbent solution flowing from the generator to the absorber. As the flow from the generator varies, the chiller maintains a constant flow to the absorber by mixing the diluted complex solution from the absorber sump with the concentrated absorbent from the generator. The device then passes the mixture through an absorber spray. When the flow rate from the generator is low, for example, the recycle flow rate is high and the initial concentrated absorbent solution entering the absorber will be diluted.

Theoretically, if the absorbent solution flow from the generator is reduced to zero, the chiller capacity will also be zero (in this case, the flow to the absorber spray is configured to be recycled from the absorber collector). In practice, however, the device must maintain a minimum flow through the generator to prevent flow congestion and crystallization in the chiller heat exchanger. In order to reduce the cooling capacity below a certain level, the apparatus must further dilute the absorbent solution flowing from the generator by mixing the absorbent solution with a large amount of excess refrigerant. However, using excess refrigerant in front of the absorber to dilute the absorbent solution increases the response time of the cooling device and also requires a large amount of refrigerant storage tank. In residential, office and industrial heat exchangers, users need absorption chillers that accept low cooling loads but respond quickly to load changes.

For example, the controller cannot change the office building chiller quickly between high and low cooling capacity by changing the concentration of the absorbent solution in the absorber spray. If the cloud partly obscures the sun on a partly cloudy day, the system circulates from the low cooling capacity to a significant cooling capacity that the sun shines through the office window when the cloud blocks the sun, increasing the internal temperature. At low capacities, the office chiller system will flood the absorbent solution flow with excess refrigerant to reduce its concentration. When a subsequent sudden increase in office air temperature will require a significant increase in cooling capacity, the generator will boil off excess refrigerant from the composite solution to rebuild the concentrated absorbent. The absorbent must be reformed in the generator before the cooling device regains its high capacity. However, when the cooling capacity is stored, the sun will again hide behind the clouds. At this point, the system must reduce the cooling capacity again because the sun no longer heats the office.

Thus, techniques for controlling the cooling capacity of an absorption chiller by varying the absorption solution concentration are known, but existing systems are insufficient when operating in low cooling ranges because of their long response times. In addition, to operate even in the low cooling capacity range, such systems require large refrigerant storage tanks.

FIELD OF THE INVENTION The present invention relates to two-phase absorption cooling apparatus, and more particularly to a control system for the detection and recovery of crystallization in a system heat exchanger. During the operation of a two-phase absorption chiller, if an accident or the functioning of the device does not operate normally, crystallization or solidification of the absorbent solution may occur when passing through the device. The most common place for crystallization is the concentrated solution passage of the concentrated solution heat exchanger. In this position, the absorbent solution is concentrated by the generator and forcedly returned to the absorber. Between the generator and absorber, the concentrated solution dilutes the absorbent solution pumped from the absorber to the generator by releasing heat through the heat exchanger. If for some reason the absorbent solution is too concentrated or cooled below the crystallization temperature, the concentrate will flow through the blocked passage and eventually become completely sealed, resulting in crystallization. This condition is known to have a very short cycle and occurs in less than one minute.

Various conditions result in crystallization of the concentrated absorbent solution in the heat exchanger. For example, the presence of air or other inert gas in the absorber prevents dilution of the absorbent solution. This will increase the concentration of the concentrated absorbent solution. As the solution is supersaturated, crystallization begins again. If the condenser water suddenly became colder than the normal operating temperature, the temperature of the diluted absorbent solution leaving the absorber will drop. This will lower the temperature of the absorbent solution concentrated in the heat exchanger below the crystallization point and shut off the heat exchanger again. Over-operation of the generator due to oversaturation of the absorbent solution results in blocking crystallization of the heat exchange passage.

It is preferable to prevent any of the above-mentioned conditions from occurring. However, due to an accident or malfunction, it is impossible to prevent crystallization in the heat exchanger. When crystallization and heat exchange blocking occur, a conventional practical method of removing heat exchanger passages is to heat them with an external heat source to liquefy the absorbent solution. However, such a solution cannot be tolerated as it requires a significant shutoff in the absorption device operation. Other conventional detection and prevention systems use mechanical floating valves in the concentrated absorbent solution flow passages, which operate when the flow is reversed due to crystallization. However, such mechanical systems have proved to be very expensive and unreliable.

Finally, the present invention relates to a control system, and more particularly to a control system with a binomial setpoint filter capable of eliminating overshoot without reducing the response to processing disturbances.

Control systems are useful for observing and controlling virtually all systems and devices. Control systems are often used for economic reasons. For example, the ability to support processing close to the required operating state is desirable. This control increases the stability and efficiency of the system.

There are two basic control systems. One form is a regular control system. This type of control system is mainly used to respond to changes and failures in the system. Embodiments of the device controlled by a regular control system include a water chiller used to provide coolant for comfortable cooling.

Another type of control system is a tracking control system. This type of control tracks changes in setpoints or associated inputs. Such a control system can improve the control of the device. For example, an initial setpoint may be introduced into a system or device, and the control system tracks deviations from the device to maintain the device's operation at the required setpoint.

In brief, the closed loop control system includes a measurement unit of the control variable and a controller that compares the actual measured value with the required value and automatically adjusts one input value to the process using the deviation therebetween. Physical systems to be controlled are electrical, thermal, hydraulic, pneumatic, gas, mechanical and other physical and chemical treatments.

In general, control systems are designed to serve one of two purposes. First, the servo mechanism is designed to follow the change in set point as much as possible. Many electrical and mechanical control systems are servomechanisms. Second, the regulator is designed to keep the output constant despite load or other failures. Regular control is widely used to control chemical processing. In general, the tracking control system observes set point changes and makes appropriate adjustments. The regular control system is adjusted to compensate for processing disturbances.

Stability, accuracy, and system response speed are determined by analyzing steady state and transition performance. It is desirable to achieve a steady state in the shortest possible time and to keep the output within certain limits. Steady-state performance is evaluated based on the accuracy with which the output is controlled for a particular input. Transition performance, i.e., the behavior of the output variables when the system changes from a steady state to another, is evaluated according to the maximum overshoot, and amounts such as rise time and response time.

Numerous factors affect control quality, including failures caused by setpoint changes and processing load changes. The setpoint and processing load are limited by the settings of the final control element to maintain the control variables at the setpoint. They therefore reposition the final control element. Other obstacles such as, for example, changes in inlet treatment solution temperature and cooling water temperature in the water chiller.

In many control systems, the step input response results in overshoot. However, step input is used to analyze many reasons. First of all, testing is easy. Secondly, the step input is the most serious obstacle, and the response to the step input represents the maximum possible error. Characteristics of transition performance include the presence and magnitude of maximum overshoot, and the frequency of transition oscillation and response time.

In this state, the output variable overshoots its required steady state conditions, resulting in transition oscillation. The first overshoot is the biggest and the effect is of interest to the designer. The main considerations for limiting this maximum overshoot are (1) to prevent damage to processing steps or devices due to excessive travel of control variables beyond those specified by the command signal, and (2) to provide high underdam system and Avoid excessive settling time involved.

As described above, the control system is used as a process regulator or tracking control. For example, absorption chillers are used for industrial purposes. In this application, the chiller control performs more tracking control functions. The water chiller control for comfortable cooling mainly controls the regulator. The cooling unit controls the coolant effluent evaporator to an unchanged set point. In these applications it is desirable to use a very high integral gain in the PID control loop to eliminate errors in the water temperature left behind by processing disturbances. Typically, high integrated gain is advantageous because the control system responds faster to load failures. However, one problem with large integrated gain usage is the control overshoot setpoint when started. Another problem with high integrated gain is shooting at low temperatures.

This overshoot problem has already been referred to as "softloding" in the control function. During or during the setpoint change, the chiller system will experience intermediate and substantial changes. The typical response of a cooling system is up to 100% to respond to changes. To compensate for this major change, the soft landing limits the output commanded from the controller at startup to slow loading onto the chiller.

However, the soft landing has various problems. Softlanding, for example, is arranged at the rear end of the control system, making it difficult to achieve its function. Because softlanding performs the function of limiting the commanded output rather than the input, the way in which the output is restricted changes different types of control systems in different devices. For example, to limit the water temperature change, the soft landing function must limit the command to control the water temperature. In addition, the command limiting method is a function of being controlled. For each system, this requires the command to be twisted for all systems. In addition, a lot of empirical work is required to obtain a response that works well.

Additional control occurs in many cases where the remaining water temperature set point needs to be changed. In addition, large overshoot can be obtained by a large amount of integrated gain. In addition, there is a comfortable cooling system in which the cooled water setpoint changes with the daily data. For example, the temperature rises at night and falls during the day. This regular change also causes the overshoot problem described above.

Therefore, in regulator control, it is desirable to increase the integrated control in order to speed up the system response. This increased integral control typically works fine until a setpoint change is needed. Thereafter, the increased integrated gain in the setpoint opportunity will be excessive and result in overshoot. However, when the same system performed tracking control, an overshoot will occur. As a result, a control system is desired that eliminates overshoot without reducing the response to processing failures.

The present invention relates to a control unit for an absorption chiller. According to one embodiment, the invention relates to an absorption heat exchanger for removing a heat sink from a heat load, and more particularly to an improved method of changing the capacity of an absorption heat exchanger. According to another embodiment, the invention relates to a two-state absorption refrigeration apparatus, and more particularly to a control system for crystallization detection and recovery in a system heat exchanger. Finally, according to another embodiment, the present invention is directed to a control system having a binary setpoint filter capable of eliminating overshoot without reducing the response to processing disturbances.

1 is a block diagram of an absorption cooling apparatus according to the present invention.

2 is a schematic view of a portion of an absorption chiller according to an embodiment of the present invention.

3 is a schematic view of a portion of an absorption chiller according to a second embodiment of the present invention.

4 is a schematic diagram of a two-phase absorption chiller employing an embodiment of the present invention.

5 is a flow diagram illustrating a recovery control system in accordance with the present invention.

6 is a block diagram of a control system of the present invention showing a second order second name filter for filtering set points in a control system.

7 is a graph showing the response of the first and second order filters to the step input.

FIG. 8 is a graph showing coolant leaving temperature over time for two-name filtered setpoints in a control system.

FIG. 9 is a graph showing cooling water leaving temperature over time for two-name filtered setpoints by change in setpoint in a control system operated in accordance with the apparatus and method of the present invention.

10 is a block diagram of an embodiment of a process control system showing an absorber chiller having a second secondary name filter for filtering set points in a control system operated in accordance with the apparatus and method of the present invention.

It is therefore an object of the present invention to provide a fast method of varying the cooling capacity of a chiller in response to load changes, processing disturbances, and other reasons for changing the melt of the absorption chiller.

Another object of the present invention is to provide a fast method of changing the responsiveness of a chiller when operating at low cooling capacity.

It is yet another object of the present invention to provide a method that can increase the cooling operating range of a chiller without sacrificing responsiveness or increasing the chiller size.

A feature of the present invention includes a variable capacity absorption chiller. The cooling device includes a generator for generating a concentrated absorbent solution and a refrigerant, an absorber including a surface contact portion in which the concentrated absorbent solution is in contact with the refrigerant, and a reservoir. The cooling device comprises at least one conduit (e.g., tube, pipe, passageway) which directs the flow of concentrated absorbent solution from the generator to the surface contact of the swelling and transfers another stream of concentrated absorbent solution from the generator to the reservoir. Or conventional containers). Finally, the chiller includes a fluid flow regulator (e.g. a valve or pump) that changes the ratio of the two flows coming from the generator.

According to another feature of the invention, a method of varying the cooling capacity of an absorption chiller is provided. This method is carried out in generators, absorbers and reservoirs. The concentrated absorbent solution flows from the generator to the surface contact of the absorber. Another stream of concentrated absorbent solution is provided from the generator to the reservoir. The required cooling capacity is determined by the cooling device, and the flow ratio of the two flows coming from the generator is varied to provide the required cooling capacity.

The present invention has several advantages as follows. In other words, the time to respond to load changes or processing disturbances is significantly reduced. In addition, the chiller operating range has the advantage that it can be extended to low capacity regions without sacrificing responsiveness or requiring extended equipment (such as large cooling reservoirs).

It is therefore an object of the present invention to provide an apparatus which is reliable and inexpensive to manufacture, and which provides a method for detecting crystallization of concentrated absorbent solutions in a heat exchanger of a two-phase absorption chiller.

Another object of the present invention is to provide an apparatus and method for recovering crystallization of a concentrated absorbent solution without the use of an external heat source once crystallization is detected.

According to another feature of the invention, a controller, an absorber, an evaporator and a high temperature generator, a low temperature generator, a condenser, a concentrated absorbent solution from a high and low temperature generator and a dilute absorbent solution from a heat exchanger A first passage for passing the low temperature heat exchanger, the concentrated absorption solution through the low temperature heat exchanger, a second passage for passing the concentrated absorption solution from the low temperature generator to the first passage, and a first passage of the concentrated absorption solution from the high temperature generator A third passage passing through the furnace, a fourth passage passing the concentrated absorption solution from the low temperature generator to the high temperature generator, a second passage temperature sensor for detecting the temperature of the concentrated absorption solution in the second passage, and a third passage; A third passage temperature sensor for detecting the temperature of the concentrated absorbent solution in the passage, and a third passage temperature sensor for detecting the temperature of the concentrated absorbent solution in the fourth passage The method for detecting crystallization in a two-phase absorption chiller system comprising a fourth passage temperature sensor is provided.

The absorption chiller comprises an evaporator spray pump for dispensing the diluted refrigerant from the evaporator refrigerant collector to the at least one evaporator spray nozzle, an absorber spray pump for dispensing the concentrated absorbent solution to the at least one absorber spray nozzle, and a concentrated absorbent solution. A fifth passage passing from the low temperature heat exchanger to the absorber, a sixth passage for passing the diluted absorbent solution from the collector to the absorber spray pump, and a sixth passage disposed in the sixth passage for And a valve to control the flow. The fifth passage temperature sensor detects the temperature of the absorbing solution in the fifth passage between the low temperature heat exchanger and the absorber.

In normal operation, the temperature detected by the fourth passage temperature sensor is equal to the temperature detected by the second passage temperature sensor, and the value in the sixth passage is closed. When crystallization begins to block the first passage, the temperature detected by the second passage temperature sensor begins to exceed the temperature detected by the fourth temperature sensor. According to this crystallization detection method, when the temperature detected by the second passage temperature sensor is equal to the average value of the temperature detected by the fourth passage sensor and the temperature detected by the third passage temperature sensor, crystallization takes place. This temperature is called the trip temperature. When the detection temperature of the second passage temperature sensor meets or exceeds the trip temperature, that is, when crystallization is detected in the low temperature heat exchanger, the control system returns to the crystallization recovery mode.

According to this aspect of the invention, the control system in the crystallization recovery mode completes the following steps.

1. In low temperature and high temperature generators, the concentration of the absorbing solution is temporarily stopped by blocking the heat to the heat source.

2. The circulation of the absorbent solution is temporarily stopped by deactivating all system pumps.

3. The valve in the sixth passage between the evaporator and the absorber spray pump opens to allow the diluted absorbent solution to flow from the collector to the absorber spray pump.

4. After 3 minutes of inactivation, the low temperature generator and the high temperature generator pump are restarted for about 5 minutes and partially pour out the highly concentrated absorbent solution resulting in crystallization.

5. The low temperature generator and high temperature generator pump are again operated for about 3 minutes to thwart any crystallization that may occur during the solution flushing operation.

6. All system pumps are restarted, the valves are closed, and the control system adjusts the heat input to the hot and cold generators, so that the temperature of the concentrated absorbent solution between the cold heat exchanger and the absorber is crystallized in the concentrate in this region. The deviation between temperature and actual temperature is maintained at a level that is increased by about 5 ° F. (about 3 ° C.) over the previous deviation.

The control system automatically proceeds twice in a recovery cycle. When crystallization is detected in three times, all operation of the absorption chiller will be stopped, which means a system problem that must be corrected.

To this end, another embodiment of the present invention provides a control system capable of eliminating an overshoot without reducing the response to a processing failure. In particular, embodiments of the control system include a two-name setpoint filter to filter setpoint changes that provide a more gradual response that eliminates overshoot.

The present invention provides a method of controlling a water chiller that provides a supply of coolant at a set temperature indicating a two-name setpoint of a system. The water chiller includes a control system with an input. This method is executed as follows. Nominal setpoint temperature is selected. The setpoint temperature is filtered using a two-name filter to provide a filtered setpoint temperature. The filtered setpoint temperature is provided at the input of the control system. The filtered setpoint temperature is a function of time and temperature. The filtered setpoint temperature is the current temperature of the original coolant, which changes as a function of time to approach the nominal setpoint temperature without showing any signs.

A general feature of the present invention is a control system including a system input, a feedback loop, a two-name filter having a setpoint input and a filtered setpoint output. The feedback loop is connected to the system via a summation node. The two-name filter is arranged to accept a nominal setpoint at its setpoint input and provide an output to the system via the summation node in response to the filtered setpoint.

Another feature of the present invention provides a method of reducing overshoot in a control system. The control system is provided to have an input. Nominal set point is selected. The nominal setpoint is filtered using a nominal filter to provide a filtered setpoint. The filtered setpoint approaches the nominal setpoint, thus reducing or eliminating the overshoot of the nominal setpoint.

The advantage of a control system with a two-name setpoint filter is that using a filtered setpoint to provide a filtered setpoint allows more integrated gain in the control system to respond quickly to load failures and result in overshoot. You can respond to start and setpoint changes without having to.

The advantage of a control system with a two-name setpoint filter is that it is very simple to use a filtered filter for softlanding. For example, instead of limiting the output command, the filter operates on the front end to drive the control response to follow the required trajectory. According to one embodiment, the precisely damped secondary response is the required trajectory obtained using a secondary secondary name filter. This binomial filter provides a gradual rise instead of a sudden rise to the required setpoint as in the absence of a filter or with a first order filter.

Embodiments of a control system having a two-name setpoint filter have the advantage that by filtering the setpoint the control system cannot see the staged input as the temperature setpoint is changed. In contrast, the response is a series of small processing obstacles.

Another advantage of a control system having a two-name setpoint filter is that already closed loop control is used for the remaining water temperature control since the two-name setpoint filtration is performed at the front end or input side of the control system.

Other objects, features and advantages of the present invention will be more clearly understood by the following detailed description with reference to the accompanying drawings.

No particular refrigerant is mentioned in the description of the present invention. Those skilled in the art will recognize refrigerant systems useful for devices using the method of the present invention. The same or different refrigerants as described above may be used in the related device.

This description generally relates to typical absorption cooling liquids, volatile refrigerants or refrigerant vapors (sometimes referred to as condensed vapors in liquid form) and weakly volatile absorbent components. These components may coexist in solution and are separable by applying heat to the solution, so that volatile refrigerants can be distilled and they may be recombined to reconstitute the solution or remove heat. The vapor is condensed to remove heat or evaporated to receive heat. It is also possible to use absorption coolants which operate in other ways but which are usable in comparable devices.

1 is a block diagram illustrating the transfer of heat and refrigerant in an absorption cooling system.

System 10 is used to transfer heat from heat load 12 to heat sink 14. As is known, this heat transfer is performed even when the heat load 12 is at the same temperature as the heat sink 14 or at a high or low temperature.

Heat from the load 12 enters the evaporator 16 of the apparatus through the passage 18 (all heat transfer from or to the element is shown in FIG. 1 by the letter Q following the arrow indicating the direction of transfer. ). The evaporator 16 is in direct heat transfer contact with the heat load 12, or the heat exchanger connects the evaporator 16 with the heat load 12 to achieve this heat stage.

Heat Q entering the evaporator 16 evaporates the condensed cooling steam entering the evaporator 16 through the passage 20. The effluent of the evaporator 16 across the passage 20 is cooling steam that withstands heat from the heat load 12.

The contact of absorber 24a receives cooling vapors through passage 22 and contacts them with concentrated less volatile absorbent solution received from generator 26 via passages 28 and 28a. The final absorption of the cooling vapor into the absorption solution condenses the vapor whose heat of vaporization has been released and releases the heat of decomposition in accordance with the absorption treatment. Final heat Q is rejected to heatsink 14 through passage 30. The reconstituted complex cooling solution is released to reservoir 24c through passage 24b, where it is mixed with the concentrated absorbent solution received from generator 26 through passages 28 and 28b. In a typical absorption chiller, the reservoir 24c is an absorber collector. However, other vessels for containing the solution can also be operated effectively in the cooling apparatus described above. The reservoir solution passes through the passage 34 and the heat exchanger 35 to the generator 26. The heat exchanger 356 preheats the complex refrigerant traversing the passage 34 before entering the generator 26 using heat to escape from the generator through the concentrated absorbent solution passage 28.

The temperature sensor 116 detects the temperature of the heat exchange solution flowing downstream of the evaporator 16 along the passage 18. Control line 13 connects temperature sensor 116 to controller 118. Another control line 15 connects the controller 118 and the flow regulator 111. Once the input has been received from the temperature sensor 116, the controller 118 thus controls the flow regulator 111 and flows through the passages 28, 28b through the passages 28, 28a along with the passages 28, 28b. The proportion of concentrated absorbent solution from generator 26 flowing to the contacts of absorber 24a is controlled. The controller 118 directs the flow rate by directing the flow regulator 111 to branch through the passage 28b all concentrated absorbent solution flowing from the generator 26 to the reservoir 24c through the passage 28. It can also be reduced to zero. The fluid flow regulator 111 consists of a pump, a valve, a series of pumps or valves, or any other device that can be adjusted to vary the flow along the passages 28a, 28b as described above.

In the generator 26, the heater 36 heats the complex cooling solution to sufficiently evaporate the more volatile cooling vapors, leaving a less volatile concentrated pig absorbing solution. The refrigerant vapor is distributed to the condenser 40 through the passage 38. The concentrated absorbent solution is moved through the passages 28, 28a, 28b to the contact of the absorber 24a with the reservoir 24c.

The condenser 40 condenses the refrigerant vapor introduced through the passage 38. Heat of condensation Q is rejected and flows along the passage 42 to the heat sink 14. The condensed refrigerant vapor escapes the condenser 40 through the passage 20 and returns to the evaporator 16, thereby completing the cycle. Thus, heat from heater 36 and heat load 12 enters the loop, and heat leaves the loop from absorber 24 and condenser 40. Unlike the heat dissipated that is lost, all heat taken from the heat load 12 and the heater 36 goes to the heat sink 14.

With reference to FIG. 2 a method and apparatus will be described which act as or as an integral part of the apparatus shown in FIG. The parts in FIG. 2 correspond to the parts in FIG. 1 and are therefore given the same reference numerals.

2 shows an embodiment of the absorption cooling system 10 of the present invention.

The system 10 includes an evaporator 16, an absorber 24, a generator 26, a condenser 40, a heat load 12, a heat sink 14, and a heat exchanger 35. Include. The generator 26 includes a dilute absorbent inlet 75, a refrigerant vapor outlet 55, and a concentrated absorbent outlet 85.

Evaporator-absorber cell 23 combines portions of evaporator 16 and absorber 24. The evaporator 16 includes a refrigerant spray 21, a heat load coil 18, an evaporator fan 17, a refrigerant storage tank 99, and a pump 102. The absorber 24 includes an absorber spray 101, a heat exchange coil X, a contact portion 24a, and an absorber collector portion 24c. The contact portion 24a of the absorber 24 is in volume with the surface of the evaporator-absorber cell 23 in which the refrigerant vapor is in contact with the absorbing solution. In this embodiment, the contact area is the volume covered by the spray 101 and the surface of the heat exchange coil X. The evaporator-absorber cell comprises a refrigerant refrigerant 107 connected to the passage 34, an absorber port 130 connected to the passage 28b, and a passage 95 from the outlet 93 of the evaporator fan 17. A refrigerant storage inlet (97) for receiving the refrigerant, a refrigerant storage outlet (100) for transferring refrigerant from the refrigerant storage tank (99) to the refrigerant spray through the passage (96), and the pump (102), and the condensation from the passage (20). An inlet 144 for receiving the refrigerant vapor.

The system 10 provides the sensors 115, 116, 117 like the controller 118 and the adjustable frequency drive 120. The system also includes three pumps. The pump 102 is connected to the refrigerant storage tank 99 as described above. The pump 103 is connected to the absorber collector and the composite refrigerant outlet 107 via a line 34, and the collector 111 is connected to the junction 131 between the passages 28, 28a, 28b.

In the generator 26, the complex refrigerant solution flows into the dilute absorbent inlet 75 and is sufficiently heated to evaporate the volatile refrigerant vapor and leave a less volatile concentrated absorbent solution. The refrigerant vapor is distributed to the condenser 40 via the refrigerant vapor outlet 55 and the line 38 to condense. The concentrated absorbent solution is distributed to absorber 24 via concentrated absorbent outlet 85 and line 28. As the concentrated absorbent solution moves through line 28 toward absorber 24, the absorbent solution passes through heat exchanger 35 where cooling is achieved by transferring heat to the complex refrigerant solution flowing through line 34. do.

Condensed refrigerant vapor from condenser 40 enters evaporator fan 17 through inlet 144 across line 20. The condensed refrigerant vapor flows from the evaporator fan 17 to the refrigerant storage tank 99 via outlet 93, line 95 and refrigerant storage inlet 97. The pump 102 withdraws the refrigerant present in the refrigerant storage tank 99 through the refrigerant storage outlet 100, and pressurizes the refrigerant into the refrigerant spray 21 through the line 96. The condensed refrigerant vapor is sprayed from the refrigerant spray 21 on the heat load line 18. The remaining spray, which remains in liquid form, is collected by the evaporator fan 17 and mixed with additional condensed refrigerant vapor entering the inlet 144 and line 20. The condensed refrigerant vapor in the evaporator fan 17 is retracted back to the refrigerant storage tank 99, and the above-described cycle is repeated.

Heat entering the evaporator 16 enters the heat load 12 and crosses the heat load line 18. Heat traversing the heat load line 18 is in heat exchange contact with the evaporator 16 to evaporate the condensed refrigerant that is sprayed into the evaporator 16 via the refrigerant spray 21 and line 96. The effluent of the evaporator 16 is the refrigerant vapor in the evaporator-absorber cell 23, which flows to the absorber 24 which withstands heat from the heat load 12.

The concentrated absorbent solution enters the contact 24a of the absorber 24 through the absorber spray 101 and enters the absorber collector 24c through the absorbent port 130. In this embodiment, the ratio of the absorbent collector 24c to the concentrated absorbent solution entering the contact 24a is controlled as follows. The flow of concentrated absorbent solution across line 28 enters junction 131 where the line 28a connected via pump 111 and line 28b connected to absorber collector 24c converge. do. The pump 111 is a variable displacement pump that meteres the concentrated absorbent solution to the absorber spray 101.

When pump 111 is operated at a capacity higher than the flow rate through passage 28, the collection liquid from absorber port 130 through line 28b is concentrated and absorbed from line 28 at junction 131. Combined with the solution. The combined solution is withdrawn to pump 111 and then pressurized through line 28a to absorber spray 101. When the pump 111 is shut down or operating at a capacity lower than the flow rate through the passage 28, the concentrated absorbent solution crossing the line 28 enters the junction 131 and then the line 28b and absorbent. It is moved to the absorber collector 24c through the port 130. When pump 111 is fully deactivated, the flow of absorbent solution through absorber spray 101 through line 28a is stopped, thereby reducing the flow rate to zero. Another way of controlling the ratio of the concentrated absorbent solution entering the contact 24a and the absorber collector 24c is to provide a pump to line 28b rather than line 28a, or to separate lines Is to use a pump. By varying the pump capacity, the flow to the absorber is controlled in the manner as described above.

Refrigerant vapor from evaporator 16 is in contact with the concentrated absorbent solution when leaving absorber spray 101. The final absorption of the refrigerant vapor into the less volatile liquid is to release the heat of evaporation to condense the vapor and release the heat of decomposition by the absorption treatment. The final row is rejected to heat sink 14 via line 30.

The pump 103 retracts the reconstructed composite refrigerant through the composite refrigerant outlet 107 and presses it to the generator 26 via the line 34. Heat exchanger 35 preheats the composite refrigerant across line 34 using heat that may escape from the generator through concentrated absorbent solution line 28 before entering generator 26.

Heat from the heat load 12 enters the evaporator 16 of the apparatus via the heat load line 18. Evaporator 16 is in heat transfer contact with heat load 12 to complete this heat transfer. The temperature sensor 115 detects the temperature of the fluid crossing the heat load line 18 as the fluid flows from the heat load 12. The temperature sensor 116 detects the temperature of the fluid crossing the heat load line 18 as the fluid flows into the heat load 12. Control line 133 and control line 135 connect sensors 115 and 116 to adjustable frequency driver 120, respectively. The control line 139 connects the adjustable frequency driver 120 to the pump 111. The frequency driver 120 controls the pumping rate of the pump 111 according to the frequency of the AC power source supplied to the driver 120.

The controller 118 is connected to the sensor 117 by the control line 140. Temperature sensor 117 detects the temperature in line 30 where heat is transferred from absorber 24 to heat sink 14. The controller 118 uses the temperature in the line 30 detected by the temperature sensor 117 to control the adjustable frequency drive 120.

When the controller 118 detects a change in the required heat load through the temperature sensors 115, 116, 117, the pump 111 is also modulated by modulating the frequency driver 120. If the controller 118 detects an increase in heat load, for example, the frequency of the frequency drive 120 is increased and thus the speed of the pump 111 is also increased, whereby the concentrated absorbent solution to the absorber spray 101 is increased. The flow is increased, which causes refrigerant vapor to flow from the evaporator 16 to the absorber 24 causing the refrigerant to evaporate at a high rate in the evaporator 16, thus rapidly increasing the cooling capacity of the system 10. Conversely, if the controller 118 detects a decrease in heat load, the speed of the pump 111 is reduced to reduce the cooling capacity of the system 10. If the controller 118 has reduced the speed of the pump 111 and hence the flow rate to zero, all flow to the absorber spray 101 is stopped, effectively reducing the cooling capacity to zero.

The pump 103, which retracts the reconstituted composite refrigerant from the absorber collector 24c and presses it to the generator 26, changes the flow rates of the absorbent solution and the composite refrigerant flowing into the absorber 24, thereby changing the cooling capacity of the apparatus. It is a variable displacement pump that changes additionally. Another way to keep changing the cooling capacity in this manner is to provide a variable capacity pump in line 28 rather than line 34 or provide separate pumps for each line.

3 illustrates another embodiment of the present invention. In FIG. 3, the controller 118 is connected to the flow regulator valve 111 via the control line 138. Flow regulator valve 111 flows a constant flow of concentrated absorbent solution from generator 26 through line 28 to absorber spray 101 through line 28a and line 28b and absorbent port 130. Branch to flow to the absorber collector 24c. The controller 118 controls the flow regulator valve 111 to vary the ratio of the concentrated absorbent solution flowing from the generator 26 to the absorber spray 101 and the flow flowing from the generator 26 to the absorber collector 24c. . The flow regulator valve 111 is a proportional valve of simple structure located in lines 28a and 28c as a proportional valve or a valve separated in each line.

In this embodiment, when controller 118 detects a change in heat load, it adjusts flow regulator valve 111 accordingly. If the controller 118 detects an increase in heat load, for example, adjust the flow regulator valve 111 to branch some or all of the concentrated absorbent solution across line 28 to the absorber collector 24c. And subsequently reduce the flow of the absorbent solution to the absorber spray 101, thereby reducing the pressure variation in the absorber 24 so that the refrigerant vapor flows from the evaporator 16 to the absorber 24, thereby allowing the refrigerant to evaporate ( In 16) it is allowed to evaporate at low rates, which in turn allows for a small cooling capacity.

Thus, the cooling capacity of the absorption cooling device responds to load changes faster than the systems and methods described above, especially when the device is operating at low cooling capacity. In addition, the apparatus described above operates in an extended operating range without compromising responsiveness or requiring an extended cold storage tank. In order to achieve a low capacity operating range without modulating the flow to the absorber spray as described above, a similar system would require a refrigerant storage tank about three times larger. Such devices and methods will respond faster than conventional devices and methods without significantly increasing the reservoir size.

4 shows a second feature of the invention. The two-phase absorption refrigerant device 400 includes a low temperature generator 401 and a condenser 402 surrounded by the first fluid sealing cell 403. The second fluid sealing cell 404 includes an evaporator 405 and an absorber 406. The high temperature generator 407 is surrounded by a third fluid sealing cell 408. The absorber 406 includes a heat exchanger 409 that receives cooling fluid through a passage 410 that passes from the cooling fluid source (not shown) through the condenser 402. Cooling fluid leaves absorber heat exchanger 409 through passage 410 and enters condenser heat exchanger 411 and returns to a cooling fluid source (not shown).

Various types of refrigerants and absorbents may be used in the two-phase absorption device of the present invention. In refrigerants such as water, lithium bromide absorbent solutions are preferred. "Concentrated solution" means a solution concentrated in an absorbent. "Diluted solution" means a solution diluted in an absorbent.

Steam flows from a source such as a boiler (not shown) through the steam passage 413 to the high temperature generator heat exchanger 412 of the high temperature generator 407. The steam passage 413 returns the condensate to a steam source through the condensate heat exchanger 414. Of course, it should be appreciated that other suitable heating sources may be used to concentrate the absorbent solution in the high temperature generator 407 (eg, the high temperature generator may be directly heated by the burner). Heat from the condensation steam in the high temperature generator heat exchanger boils the refrigerant solution in the high temperature generator 407, thereby producing refrigerant vapor and concentrating the absorbent solution.

The refrigerant vapor generated in the high temperature generator 407 is directed to the low temperature generator heat exchanger 456 through the refrigerant vapor passage 415 to condense in the condenser 402. The dilute solution in the low temperature generator is boiled into the refrigerant vapor in the refrigerant vapor passage 415 through the heat exchanger and condensed in the condenser 402. At least a portion of the concentrated solution produced in the low temperature generator 401 is distributed to the high temperature generator pump 417 through the third passage 416 and pumped to the high temperature heat exchanger 419 through the passage 418. In the high temperature heat exchanger 419, at least a portion of the concentrated solution in the passage 418 is preheated in the passage to the high temperature generator 407 via heat exchange with the hot concentrate flowing into the passage 420. A portion of the concentrate flowing into the passage 418 is directed to the condensation heat exchanger 414 through the passage 421 and associated with the solution in the passage 418 before condensate passage 413 before being distributed to the high temperature generator 407. Heat exchange with condensate at

The hot concentrate is directed from hot generator 407 to hot concentrate accumulator 422 through hot heat exchanger 419 through hot passage 420. The hot concentrate from accumulator 422 is mixed through a third passage with the cold concentrate leaving the cold generator 401 through second passage 424 at mixing point 425. From the mixing point 425, the combined concentrate directs the low temperature heat exchanger 426 through the first passage 427, the fifth passage 428, the absorber spray pump 429, and the passage 430. Through the absorber 406.

Liquid refrigerant from the condenser 402 is transferred to the evaporator 405 through the passage 431. This liquid refrigerant evaporates in the evaporator 405 and thus removes heat from the cooling fluid flowing through the passage 432 through the evaporator heat exchanger 433. The cooling fluid is circulated to a heat load such as a building requiring cooling.

Absorber 406 is vapor-connected with evaporator 405, and the absorbent solution removes heat from the evaporator portion by absorbing the absorbent solution from evaporator 405. At least a portion of the refrigerant liquid falling from the evaporator heat exchanger 433 is collected in the collector 434. The refrigerant liquid flows from the collector 434 through the passage 435 to the storage container 436. Through passage 437, refrigerant liquid is dispensed from storage vessel 436 to evaporator spray pump 438, which distributes refrigerant liquid through passage 439 to evaporator 405 through nozzle 440. do.

Dilution solution from absorber 406 flows through passage 441, cold generator pump 442, passage 443, cold heat exchanger 426, and passage 444 to cold generator 401. . In the low temperature heat exchanger 426, the concentrate is moved to exchange heat with the diluent from the absorber 406 which is distributed to the low temperature generator 401, so that the diluent is preheated.

From the high temperature heat exchanger 426, the concentrate flows through the fifth passage 428 to the absorber spray pump 429. The concentrate is pressurized by the absorber spray pump 429 through the passage 430 and discharged to the absorber 406 through the absorber spray nozzle 445. A passage 446 is disposed between the reservoir 436 and the absorber spray pump 429. The flow between the reservoir 436 and the absorber spray pump 4289 is controlled by a normally closed valve.

When crystallization occurs in the concentrate in the high temperature heat exchanger 426, the concentrate in the first passage is reversed due to the crystallization barrier. This effect makes it possible to detect crystallization by observing the solution temperature.

The fourth passage temperature sensor 448 detects the concentrate temperature between the high temperature generator pump 417 and the low temperature generator 401 in the fourth passage. The second passage temperature sensor 449 detects the concentrate temperature of the second passage 424 between the low temperature generator 401 and the mixing point 425. The third passage temperature sensor 450 detects the hot concentrate temperature in the third passage 423. The fifth passage temperature sensor detects the concentrate temperature in the fifth passage 428.

The operation of the absorption chiller is effected by a controller 453 having a processing circuit such as, for example, a microprocessor. The controller 453 takes the form of a feedback using an input signal receiver 454 and an output signal generator 455. The output control signal is generated by the signal generator 455 in response to the input signal received by the input signal receiver 454.

During normal stable operation, the temperature detected by the fourth passage temperature sensor is approximately equal to the temperature detected by the second passage temperature sensor 449, and the control system modulates the heat input to the high temperature generator 407. The concentrate temperature in the fifth passage detected by the fifth passage temperature sensor 451 is maintained at 15 ° F., which is higher than the concentrate crystallization temperature.

When concentrate crystallization in the cold heat exchanger 426 occurs, the flow through the first passage 427 begins to reverse due to the blockage. Therefore, the temperature detected by the second passage temperature sensor 449 exceeds the temperature detected by the fourth passage temperature sensor 448. According to the present invention, a crystallization alarm is made, wherein the temperature detected by the second passage temperature sensor 449 is detected by the third passage temperature sensor 450 and the temperature detected by the fourth passage temperature sensor 448. The correction operation determined by the following equation is displayed when it meets or exceeds the mathematical mean value of the temperature.

T _TRIP = (T ₃ + T ₄ ) / 2

T ₃ is the temperature detected by the third passage temperature sensor,

T ₄ is the temperature detected by the fourth passage temperature sensor,

This temperature value is referred to as the trip temperature.

If the temperature detected by the second passage temperature sensor 449 meets or exceeds the trip temperature, the control system is activated to restore crystallization of the concentrate in the low temperature heat exchanger 426.

In recovery mode, the control system goes through the following steps.

1. The heat sources to the low temperature generator 401 and the high temperature generator 407 are deactivated to stop the production of the concentrate. In the embodiment shown in FIG. 4, this is done by shutting off the steam valve 452 to shut off the steam supply to the high temperature generator 407.

2. The circulation of the absorbent solution is stopped by deactivating the high temperature generator pump 417, the low temperature generator pump 442, the absorber spray pump 429 and the evaporator spray pump 438.

3. The solution at the absorber may be diluted with the diluent by opening valve 447 to allow diluent from storage tank 436 to flow into absorber spray pump 429.

4. After 3 minutes, the crystallized concentrate flows down by restarting the low temperature generator pump 442 and the high temperature generator pump 417 for about 5 minutes.

5. The low temperature generator pump 442 and the high temperature generator pump 417 are again deactivated for about 3 minutes (this is done because the reactivation of the pump according to step 4 above results in temporary recrystallization).

6. The heat source to the high temperature generator 407 is restarted. However, since the control system regulates the heat input to the high temperature generator 407 and the low temperature generator 401, the temperature of the concentrate leaving the low temperature heat exchanger 426 through the fifth passage 428 is the crystallization of the concentrate in this region. The deviation between temperature and actual temperature is maintained at a level that increases to about 5 ° F. (3 ° C.) over the previous control deviation.

7. Three minutes after step (5) has elapsed, all pumps are restarted.

The control system allows the system to go through two recovery sequences, for example a set number of times. If crystallization is detected more than this set number of times, the control system shuts down all operations of the absorber, so that the maintenance necessary to correct the regenerated crystallization can be performed.

5 is a flowchart showing a recovery sequence of the present invention described above.

Other features of the invention will be described below. The main function of the control system applied to the water chiller is, for example, treatment control. The process control includes maintaining the cooled remaining water at the required temperature. Thus, the control system must respond quickly to processing failures to minimize the magnitude and duration of deviations between the remaining water temperature and the required set point. To minimize this deviation, the control response can be adjusted to assist in integral operation.

As mentioned above, problems can arise in many cases. For example, if a setpoint change is made during setup, the high integral gain allows the system to overshoot the setpoint heavily. By filtering setpoint changes, overshoot can be eliminated without reducing the response to processing failures.

Thus, the setpoint filter of the present invention has other functional advantages. During the prestart sequence of the chiller, the filtered set point initializes the current water temperature. When closed loop control is followed, the initial error in the remaining water temperature is zero. When the filtered setpoint approaches the required setpoint, a small error will be detected by the closed loop control. The control system will track the filtered set point as time changes. The time to take the filtered setpoint to reach the required setpoint is the settling time. By allowing the settling time as an adjustable input value, the filtered setpoint will replace the new one known as "soft landing". The advantage of using filtered setpoints for softlanding at the front end of the control system is the use of closed loop control already in place for the remaining water temperature control. This simplifies the performance and verification of the function.

An embodiment of a second order binomial filter designed to prefilter the control set point is shown in FIG. 6. The control system is shown at 500. The control system 500 includes a feedback loop 505 with a sum node 508. Also shown in FIG. 6 is a two-name filter 510. The two-name filter 510 is connected and arranged to accept a setpoint input 515. The two-name setpoint filter 510 provides the output of the filtered setpoint 520. The filtered setpoints are connected as inputs to the control system 500 and the feedback loop 505 via the summation node 508. As shown in FIG. 6, a two-name setpoint filter 510 is disposed at the input side of the control system 500.

7 shows the response to the step input. For example, the ideal response of the control system to the step input is precisely damped with respect to the slightly underdamped second order function (FIG. 7). The filter accepts a step input (typically the remaining water temperature is varied) and outputs a finely damped secondary output. If the settling time of the filter is small enough that the cutoff frequency is within the bandwidth of the open loop system, prefiltering of the setpoint will not increase the settling time.

As shown in FIG. 7, the input is a step input represented by the letter I. FIG. The response curve of the first order filter is shown by the letter (F). The first order filter response F has a steep slope close to the original value, resulting in a sudden discontinuity at the start of the step input. Unlike the first order response, the second order response curve is shown by the letter S. As shown in FIG. 7, the second order response curve S has a gradual slope at the beginning of the curve and provides a smooth transition in response to the step input. As shown in detail in FIG. 7, the primary response F converges to the step input I slightly earlier than the secondary response S. FIG. However, the secondary response S is within the acceptable response time limit.

8 shows a series of curves. The curve shows the operation of the two-name setpoint filter 510 in an absorption water cooling system operated according to the apparatus and method of the present invention. In FIG. 8, the vertical axis shows temperature and the horizontal axis shows elapsed time.

As shown, the first few minutes include the start of the burner and pump in the chiller. During the first 12 minutes, the chiller is warmed up and the system is running for the indicated time period. For about 12 minutes, control is released and the two-name setpoint filter 510 is initially set equal to the remaining water temperature. Once control is released, the system follows the filtered set point as shown in FIG.

In FIG. 8, the water starts at about 82 ° F. and the filter set point, denoted FS, reaches up to 44 ° F. The coolant outflow evaporator curve CWL is close to the downward filtered setpoint FS as shown in FIG. 8. The error between the filtered setpoint FS and CWL is the feedback to the control system. 8 shows that the cooling device is not larger than when started at cooling water temperatures of 44 ° and 80-83 °. Thus, the two-name set point filtered in an embodiment of the present invention eliminates the occurrence of large errors at initial startup. Two-point filtration of the set point lowers the coolant temperature at a more gradual rate. Also, as shown in FIG. 8, there is no overshoot of the coolant outflow evaporator curve CWL to the filtered setpoint curve FS. Cooling water inlet evaporator curves (CWE) are also shown. The coolant inlet evaporator curve (CWE) shows that the loop controller attempts to maintain its temperature once it reaches the 51 ° level as shown in FIG. 8. 8 shows a fine overshoot bit in the coolant inlet evaporator. The load is added as the water temperature drops.

Since the two-name setpoint filter 510 is disposed at the front end or input of the control system, unlike at the output, the response is progressive as shown in FIG. The absorber chiller will cause the load to increase to 100% due to the 44 ° setpoint deviation without the two-name filter 510. Since the water temperature comes at a high rate, the chiller will try to limit the load. In this slow system, the sequence does not work well because the chiller accepts full load before the water temperature changes. Thus, conventional softlanding is much more reactive and difficult to operate. Alternatively, two-name setpoint prefiltration at the input stage of the control system overcomes this problem as described above.

Fig. 9 shows a state in which, for example, the absorption chiller has a constant load and descends to the set point. In FIG. 9, the descent is about 55 ° to 49.5 °. Also shown is a cooling water inlet evaporator according to CWE. 9 is similar to the response shown in FIG. 7 except for the inversion scheme.

9 shows a state in which the operator resets the water temperature in the morning, for example after setting the cooling device temperature for comfortable cooling at a high temperature setpoint at night. Therefore, the user needs to lower the cooling water temperature during the day.

Thus, FIG. 9 shows that the setpoint has been reduced from 55 ° F. to 49,5 ° F. A second order response of a two-name setpoint filter similar to FIG. 7 is shown. The water temperature proceeds at an almost constant rate to reach the set point. The dashed line shows the coolant outflow evaporator. Even without two-name setpoint filtration, the initial decrease in water temperature results in a temperature error of 60 ° F. at a time. However, filtration of the setpoint using the two-name setpoint of the present invention only increases a series of small changes instead of pulling the finely indicated load to full load of the chiller. Thus, the present invention acts like a series of processing faults instead of one opposing jump to bring the chiller to 100% operating state. As a result, the present invention avoids an additional increase of 100% in the chiller, and then quickly lowers the temperature.

The actual filter set point converges at the settling time, but nothing is done to reset it until the device is stopped. The chiller is set to the actual effluent temperature. Otherwise, the chiller will follow the actual set point.

Another advantage of the present invention is that the present invention works well in the opposite state, for example when changing the setpoint from 49 ° F to 55 ° F. For example, in well-known chillers, deviation stops are known to be important. If you attempt to raise the setpoint above a certain amount indicating a deviation stop, the device will stop immediately due to the distortion of the maximum deviation stop. However, as mentioned above, due to the gradual nature of the two-name setpoint filter, a chiller operated in accordance with the principles of the present invention will increase the load and raise the outflow water temperature without shutdown.

10 illustrates another embodiment of the present invention. 10 shows an absorber chiller as part of a larger process. For example, the absorber shown in FIG. 10 includes a two-name setpoint filter 510 as described above. In this application, the absorber chiller is only part of the overall system of large scale. At this time, the cooling device control unit is required to perform more tracking control functions as shown in FIG. At this time, the response of the cooling device is defined by the two-name setpoint filter 510. This makes the design of the process control part shown in FIG. 10 easy because the dynamics of the cooling device are already good.

Thus, the present invention uses filtration of set points to avoid overshoot while maintaining a response to processing failures. As mentioned above, although a first order filter may be used, a comparison of the response of FIG. 7 and the first and second order filters shows that the second order filter has a smooth initial response. In contrast, the initial response of the first order filter is rather abrupt.

The primary filter or secondary filter is digitally operated. This is because the mathematical expression of the filter and the digital manipulation are made easy using a computer. This programming also allows the use of microprocessors in the control system. The method described below is used to develop a separate representation of the primary digital filter. As noted above, the result is in a form that can be easily programmed using a microprocessor.

First, a first order Laplace function is used.

G (s) = a / (s + a)

A is the cutoff frequency of the filter.

The shock transfer function is then calculated as follows.

Γ (s) = Σ Is the rest.

Is a zero-place Laplace transform with s replaced by p.

The pools of are 0 and -a. Thus, the shock transfer function is

The conversion to the Z domain is performed by substituting as follows.

Finally, switching to the programmable form is performed by:

Thus, the equation can be manipulated digitally in a form programmable on a computer or microprocessor. Likewise, the binary filter may be provided in a programmable form. Two-name filters are limited to those that have ideal and practical poll positions. The two-name filter also has a slow response with no overshoot. The programmable form of the second name filter is determined in the same basic manner as described for the first order filter. The main equation is described as follows.

Laplace form:

Z transform

An algorithm for an embodiment of the second order filter 510 is as follows.

Cutoff Frequency = 5 / Settling Time ^＊ 60

α = e ^{Δt, cutoff frequency}

The calculation of the coefficient α can be made accurate by a series of expansions. The first three terms of expansion yield appropriate results.

α = 1-Δ2t ^＊ Cutoff Frequency + Δt ^＊ Δt ^＊ Cutoff Frequency ^＊ Cutoff Frequency / 2

Thus, the two-name filter provided in the programmable form is as follows.

Filtered set point n =

In addition, the primary plant with the PID controller will act as a secondary function. Thus, the system will naturally follow the second setpoint. The response of the second order function can be specified by specifying a natural function and damping this function. By choosing a two-name function, the response is precisely damped, which means that the response is damped as quickly as possible without overshooting. Thus, only one variable feels the need to set the settling time.

By prefiltering the setpoint, the control system does not see a sudden large error in the outflow water temperature as the setpoint changes. When there is a step change in the effluent water temperature setpoint, the filtered setpoint changes a small fraction of every control cycle, so the control system sees only a small error in the effluent water temperature and reacts accordingly. As the filtered set point continues to change, the control system will see a small, continuous error cycle and will continuously change the effluent water temperature. The filtered setpoint will begin to approach the actual setpoint gradually. Since the filtered setpoint approaches the actual setpoint slowly, control will act to prevent (or at least minimize the overshoot) the effluent water temperature overshooting the required setpoint.

The present invention has been described with reference to the preferred embodiments, and is not limited thereto, and one of ordinary skill in the art should recognize that various modifications and changes can be made to the present invention without departing from the appended claims.

Claims (36)

A generator for generating concentrated absorbent solution and refrigerant, An absorber having a surface contact for contacting the concentrated absorbent solution with the refrigerant, Storage tank, At least one conduit for transferring a first stream of concentrated absorbent solution from the generator to a surface contact of the absorber and a second stream of concentrated absorbent solution from the generator to a reservoir; And a fluid flow regulator for varying the flow ratio of the primary and secondary flows. 2. The variable displacement absorption chiller of claim 1 wherein the surface contact of the absorber comprises at least one spray. 2. The variable displacement absorption chiller of claim 1 wherein the surface contact of the absorber comprises at least one spray and at least one heat exchanger. 2. A variable displacement absorption chiller as recited in claim 1 wherein said absorber further comprises a collector. 5. The variable displacement absorption chiller of claim 4 wherein said reservoir is a collection of absorbers. The apparatus of claim 1, further comprising a temperature sensor at a control unit of the cooling device, wherein the fluid flow regulator is configured to change the first and second flow ratios according to the temperature detected by the temperature sensor. A variable capacity absorption chiller, operatively connected. The method of claim 1 wherein the concentrated absorbent solution is passed from the generator through the branched conduit from the generator to the absorber, the branched conduit passing the first flow to the surface contact of the absorber, and the second branch. And a second branch for delivering the secondary flow to the reservoir. 8. The variable displacement absorption chiller of claim 7 wherein said fluid flow regulator is located at a branch point of said branched conduit. 8. The variable displacement absorption chiller of claim 7, wherein the fluid flow regulator is located at a first branch of the branched conduit. 2. The variable displacement absorption chiller of claim 1 wherein the fluid flow regulator comprises at least one valve. 2. The variable displacement absorption chiller of claim 1 wherein the fluid flow regulator comprises at least one adjustable ratio pump. 2. The variable displacement absorption chiller of claim 1 further comprising at least one adjustable ratio pump to vary the overall flow ratio of the concentrated absorbent solution flowing from the generator to the absorber. In the method for changing the cooling capacity of the absorption chiller, Providing a generator for generating a concentrated absorbent solution and a refrigerant; Providing an absorber having surface contacts for contacting the concentrated absorbent solution with the refrigerant, Providing a reservoir, Providing a first stream of concentrated absorbent solution from the generator to the surface contact of the absorber and a second stream of concentrated absorbent solution from the generator to the reservoir; Determining the required cooling capacity of the device at a given time; Varying the flow ratio of the primary flow and the secondary flow to provide the required cooling capacity. The method of claim 13 wherein the concentrated absorbent solution is sprayed onto the surface contact of the absorber. 14. The method of claim 13, wherein the method of determining the required cooling capacity comprises providing a temperature sensor for measuring the temperature at a control point of the device, the method being required from the temperature detected at the control point at a given time. Calculating a cooling capacity. 14. The method of claim 13, further comprising using at least one flow control valve to vary the flow ratio of the primary flow and the secondary flow. 14. The method of claim 13, further comprising at least one adjustable ratio pump to vary the flow ratio of the primary and secondary streams. 14. The cooling capacity change of claim 13 wherein the cooling capacity of the device is further varied by providing at least one adjustable rate pump to change the total flow rate of the concentrated absorbent solution flowing from the generator to the absorber. Way. The method of claim 13 wherein the cooling capacity of the device reduces the flow ratio to zero. A controller, an absorber, an evaporator and a high temperature generator, a low temperature generator, a condenser, a low temperature heat exchanger for positioning the concentrated absorption solution from the hot and cold generators and the diluted absorption solution from the heat exchanger, and a concentrated absorption solution A first passage through which a low temperature heat exchanger passes, a second passage through which the concentrated absorption solution passes from the low temperature generator to the first passage, a third passage through which the concentrated absorption solution passes from the high temperature generator to the first passage, A fourth passage through which the concentrated absorption solution passes from the low temperature generator to the high temperature generator, a second passage temperature sensor for detecting the temperature of the concentrated absorption solution in the second passage, and a concentrated absorption solution in the third passage. A second passage temperature sensor for detecting temperature and a fourth passage temperature sensor for detecting the temperature of the concentrated absorbent solution in the fourth passage; In the method for detecting the crystallization of the phase absorption chiller, Detecting the temperature of the absorbent solution concentrated in the second passage, Detecting the temperature of the absorbent solution concentrated in the third passage; Detecting the temperature of the absorbent solution concentrated in the fourth passage; Concentration in the first passage when the temperature of the concentrated absorbent solution in the second passage is equal to or exceeds the average of the temperature of the concentrated absorbent solution in the third passage and the temperature of the concentrated absorbent solution in the fourth passage Generating a control signal alarm to monitor crystallization of the absorbed solution, The average value is T _mean = (T ₃ + T ₄ ) / 2, wherein T ₃ is the temperature of the concentrated absorbent solution in the third passage, and T ₄ is the temperature of the concentrated absorbent solution in the fourth passage. A crystallization detection method characterized by the above-mentioned. An apparatus for detecting crystallization in a two-phase absorption chiller, With the controller, With absorber, Evaporator, High temperature generator, With low temperature generator, With a condenser, A low temperature heat exchanger positioned to heat exchange the concentrated absorbent solution from the hot and cold generators and the diluted absorbent solution from the absorber, A first passage that directs the concentrated absorbent solution through a low temperature heat exchanger, A second passage directing the concentrated absorbent solution from the cold heat exchanger to the first passage, A third passage for directing the concentrated absorbent solution from the high temperature generator to the first passage, A fourth passage for directing the concentrated absorption solution from the low temperature generator to the high temperature generator, A second passage temperature sensor for detecting the temperature of the absorbent solution concentrated in the second passage; A third passage temperature sensor detecting a temperature of the absorbing solution concentrated in the third passage; A fourth passage temperature sensor detecting a temperature of the absorbent solution concentrated in the fourth passage; Crystallization in the absorbent solution concentrated in the first passage when the temperature of the absorbent solution concentrated in the second passage meets or exceeds the average of the temperature of the absorbent solution in the third passage and the temperature of the absorbent solution in the fourth passage Includes a signal generator for generating a control signal to display, The mean value is determined by T _mean = (T ₃ + T ₄ ) / 2, where T ₃ is the temperature detected by the third passage temperature sensor and T ₄ is the temperature detected by the fourth passage temperature sensor. Crystallization detection apparatus characterized by the above-mentioned. An evaporator with a controller, an absorber, a collector for collecting the diluted absorbent solution, a high temperature generator heated by a first heat source, a low temperature generator heated by a second heat source, and concentrated from a high and low temperature generator. A low temperature heat exchanger that heat exchanges the absorbent solution and the diluted absorbent solution from the absorber, a high temperature pump that distributes the concentrated absorbent solution from the low temperature generator to the high temperature generator, and a low temperature that distributes the diluted absorbent solution from the absorber to the low temperature heat exchanger. A generator pump, an evaporator spray pump that distributes the diluted refrigerant from the collector to the at least one evaporator spray nozzle, an absorber spray pump that distributes the concentrated absorbent solution to the at least one absorber spray nozzle, and concentrated through a low temperature heat exchanger. The first passage for directing the absorbent solution, and the concentrated absorbent solution A second passage that directs the group from the high temperature generator to the first passage, a third passage that directs the concentrated absorption solution from the high temperature generator to the first passage, a fourth passage that directs the concentrated absorption solution from the low temperature generator to the high temperature generator, A fifth passage for directing the concentrated absorbent solution from the low temperature heat exchanger to the absorber, a sixth passage for directing the diluted absorbent solution from the collector to the absorber spray pump, and a diluted absorbent solution disposed in the sixth passage in the sixth passage A method for detecting and restoring crystallization in a two-phase absorption chiller, comprising a valve for controlling the flow of Detecting the temperature of the absorbent solution concentrated in the second passage, Detecting the temperature of the absorbent solution concentrated in the third passage; Detecting the temperature of the absorbent solution concentrated in the fourth passage; Crystallization in the absorbent solution concentrated in the first passage when the temperature of the absorbent solution concentrated in the second passage meets or exceeds the average of the temperature of the absorbent solution in the third passage and the temperature of the absorbent solution in the fourth passage Detecting a control signal to be displayed; Transmitting the control signal to a controller in response to a control signal, The average value is determined by T _average = (T ₃ + T ₄ ) / 2, T ₃ is a temperature detected by the third passage temperature sensor, T ₄ is a temperature detected by the fourth passage temperature sensor, The controller generates and issues a response signal to complete a crystallization recovery sequence step, The crystallization recovery step, Deactivating the first and second heat sources; Deactivating the low temperature generator pump, the high temperature generator pump, the absorber spray pump, and the evaporator spray pump; Opening a valve for flowing the diluted absorbent solution from the collector through the sixth passage to the absorber spray pump, Reactivating the low temperature generator pump and the high temperature generator pump for 5 minutes; Stopping the cold generator pump and the high temperature generator pump after about 3 minutes; Reactivating the low temperature generator pump, the high temperature generator pump, the absorber spray pump and the evaporator spray pump; Sealing the valve, Reactivating and modulating the first and second heat sources such that a deviation between the crystallization temperature of the concentrated absorbent solution in the fifth passage and the temperature of the concentrated absorbent solution in the fifth passage increases by 5 ° F. Crystallization detection and recovery method. A crystallization detection and recovery apparatus in a two-phase absorber chiller, With the controller, With absorber, An evaporator with a collector for collecting the dilute absorbing solution, A high temperature generator heated by a first heat source, A low temperature generator heated by a second heat source, A low temperature heat exchanger for heat exchanging the concentrated absorbent solution from the hot and cold generators and the dilute absorbent solution from the absorber, A high temperature generator pump for distributing the concentrated absorption solution from the low temperature generator to the high temperature generator, A low temperature generator pump for dispensing the diluted absorbent solution from the absorber to the low temperature heat exchanger, An evaporator spray pump for dispensing the diluted refrigerant from the collector to the at least one evaporator spray nozzle, An absorber spray pump for dispensing the concentrated absorbent solution to at least one absorber spray nozzle, A first passage for directing the concentrated absorbent solution through a low temperature heat exchanger, A second passage for directing the concentrated absorption solution from the low temperature generator to the first passage, A third passage for directing the concentrated absorbent solution from the high temperature generator to the first passage, A fourth passage for directing the concentrated absorption solution from the low temperature generator to the high temperature generator, A fifth passage for directing the concentrated absorption solution from the low temperature heat exchanger to the absorber, A sixth passage for directing the diluted absorbent solution from the collector to the absorber spray pump, A valve controlled by a controller disposed in the sixth passage and controlling the dilute absorbing solution flow in the sixth passage; A second passage temperature sensor for detecting the temperature of the absorbent solution concentrated in the second passage; A third passage temperature sensor detecting a temperature of the absorbing solution concentrated in the third passage; A fourth passage temperature sensor detecting a temperature of the absorbent solution concentrated in the fourth passage; Crystallization in the absorbent solution concentrated in the first passage when the temperature of the absorbent solution concentrated in the second passage meets or exceeds the average of the temperature of the absorbent solution in the third passage and the temperature of the absorbent solution in the fourth passage A control signal generator for generating a control signal to be displayed; A control signal receiver for receiving a control signal to the controller in response to the control signal, The average value is determined by T _average = (T ₃ + T ₄ ) / 2, T ₃ is a temperature detected by the third passage temperature sensor, T ₄ is a temperature detected by the fourth passage temperature sensor, The controller generates and issues a response signal to complete a crystallization recovery sequence step, The crystallization recovery step, Deactivating the first and second heat sources; Deactivating the low temperature generator pump, the high temperature generator pump, the absorber spray pump, and the evaporator spray pump; Opening a valve for flowing the diluted absorbent solution from the collector through the sixth passage to the absorber spray pump, Reactivating the low temperature generator pump and the high temperature generator pump for 5 minutes; Stopping the cold generator pump and the high temperature generator pump after about 3 minutes; Reactivating the low temperature generator pump, the high temperature generator pump, the absorber spray pump and the evaporator spray pump; Sealing the valve, Reactivating and modulating the first and second heat sources such that a deviation between the crystallization temperature of the concentrated absorbent solution in the fifth passage and the temperature of the concentrated absorbent solution in the fifth passage increases by 5 ° F. Crystallization detection and recovery device. 24. The apparatus of claim 23, wherein said first and second heat sources comprise steam. 24. The apparatus of claim 23, wherein said first heat source comprises steam and said second heat source comprises a hot concentrated absorbent solution. 24. The apparatus of claim 23, wherein the at least one evaporator spray nozzle comprises a plurality of evaporator spray nozzles. 24. The apparatus of claim 23, wherein the at least one absorber spray nozzle comprises a plurality of absorber spray nozzles. 24. The apparatus of claim 23, further comprising a storage vessel for storing the diluent refrigerant, wherein the storage vessel is disposed between the collector and the absorber spray pump in fluid communication with the sixth passageway. In the water chiller system control method for providing the remaining water at a set temperature, Providing a control system for a water cooling system having an input; Filtering the setpoint temperature using a two-name filter to provide a filtered setpoint; Providing the filtered setpoint to an input of the control system. 30. The method of claim 29, further comprising initializing the filtered setpoint to be equal to the current temperature of the remaining water. 30. The method of claim 29, further comprising providing a gradual transition from the current temperature of remaining water to the required setpoint temperature. System inputs, A feedback loop connected to the system input through a sum node, And a two-name filter arranged to accept a setpoint input and provide a filtered setpoint output with a gradual initial response to the control system via the summation node. 33. The control system of claim 32, wherein the two-name filter provides through the summation node a filtered setpoint output value having a gradual initial response in response to the control system. In a method of reducing overshoot in a control system, Providing a control system having an input; Setting the setpoint, Filtering the setpoint using a two-name filter to provide a filtered setpoint, Providing the filtered setpoint to the input of the control system. 35. The method of Claim 34, further comprising initializing the filtered setpoint equal to a current control variable in the control system. 35. The method of Claim 34, further comprising providing a filtration setpoint having a gradual initial response in response to an input of the control system.