KR20140076035A - absoption system and a controlling method of the same - Google Patents

Abstract

The present invention relates to an absorption system and a control method thereof. More specifically, the present invention relates to an absorption system and a control method thereof, wherein the absorption system is operated at optimal efficiency. The absorption system according to an embodiment of the present invention comprises an evaporator, an absorber, a high-temperature regenerator, a low-temperature regenerator, and a pump supplying an absorption liquid from the absorber to the high-temperature regenerator, and includes a control part calculating the frequency value of the inverter of the pump through a feedback control, and controlling a temperature difference between the inlet and the outlet of cold water to be maximized by applying the calculated frequency value of the inverter to the pump, wherein the temperature difference is proportional to the efficiency (COP) of the absorption system.

Description

Absorption system and a control method thereof

The present invention relates to an absorption system and a control method thereof. More particularly, to an absorption type system operating at an optimum efficiency and a control method thereof.

Absorption systems can be said to include absorption chillers, absorption chillers, and medium temperature water chillers.

Specifically, the absorption type system absorbs, regenerates, condenses and evaporates a refrigerant (for example, distilled water) using an absorption liquid (for example, lithium bromide (LiBr) aqueous solution) with a gas or a fuel such as LPG or LNG as a heat source (For example, an indoor unit) in the course of the cycle, and uses cooling water or cooling water circulating the load side (for example, indoor unit) for cooling and heating and cooling.

1 is a schematic diagram of a general absorption type system 1 according to the prior art.

As shown, the absorption system 1 may include a high temperature regenerator 20 and a low temperature regenerator 30. That is, two regenerators may be provided, which may be referred to as a "dual efficiency" absorption system. In addition, the absorption type system 1 may include a low-temperature heat exchanger 60 and a high-temperature heat exchanger 70 in which heat exchange is performed between the absorption liquids.

In particular, the absorption system 1 may comprise an absorber 10, a hot regenerator 20, a cold regenerator 30, a condenser 40 and an evaporator 50. These configurations and the up-and-down and left-right positions of the pipes to be described later may be substantially as shown in Fig.

The cycle of the absorption system 1 will now be described.

The low-concentration absorption liquid (that is, the absorption liquid containing a large amount of water) from the absorber enters the high-temperature regenerator 20 via the low-concentration pipe 13 via the low-temperature heat exchanger 60 and the high-temperature heat exchanger 70. As the low-concentration absorbing liquid entering the high-temperature regenerator 20 is heated by the burner 21 or the like, the refrigerant vapor in the absorbing liquid is evaporated and separated. That is, since the refrigerant vapor is separated and regenerated in the absorption liquid in the high temperature regenerator 20, the concentration of the absorption liquid becomes thick. This can be called the medium concentration.

That is, separating the absorption liquid from the refrigerant can be referred to as regeneration, and the regeneration includes separating the refrigerant vapor by evaporating the refrigerant. In addition, the regeneration may include further heating the separated refrigerant vapor to produce superheated steam.

The medium-concentration absorbent obtained in the high-temperature regenerator 20 heats the low-concentration absorbent coming into the high-temperature regenerator 20 via the high-temperature heat exchanger 70 via the medium-density pipe 22 in advance, and then flows into the low-temperature regenerator 30 . The refrigerant vapor regenerated in the high temperature regenerator 20 flows into the low temperature regenerator 30 through the refrigerant tube 23 while flowing in the heat exchanger tube group 31 arranged in the low temperature regenerator 30, ) Heats up the heavy concentration absorbent that has flowed into the inside. Therefore, the refrigerant vapor is regenerated in the medium-concentration absorption liquid, and a high-concentration absorption liquid is produced. The heat-exchanged refrigerant vapor is condensed in the heat transfer pipe group and flows into the condenser 40 through the outlet pipe 33.

The high-concentration absorption liquid generated in the low-temperature regenerator 30 flows into the absorber 10 after heating the low-concentration absorption liquid coming from the absorber 10 through the low-temperature heat exchanger 60 along the high-concentration pipe 32 in advance.

In the absorber 10, the high-concentration absorbing liquid absorbs the water vapor introduced from the evaporator 50 and becomes a low-concentration absorbing liquid. The absorption heat generated in the process is cooled by the absorber-side cooling water heat transfer tube group 11. Then, the low-concentration absorbing liquid which is lodged in the lower part of the absorber is discharged through the pump P1, and the above cycle is repeated.

The cooling water flows into the absorber 10 along the cooling water pipe 81 and flows in the group of cooling water heat pipes 11 in the absorber 10 to cool the high concentration absorbing liquid and flow into the condenser 40. The cooling water flows through the cooling water heat transfer tube group 41 in the condenser, condenses the refrigerant vapor flowing from the low temperature regenerator 30, and then is discharged from the condenser through the cooling water pipe 81. Therefore, the cooling water flowing into the absorption type system 1 is caused to rise in temperature along the cooling water pipe 81.

Specifically, the refrigerant vapor regenerated from the medium concentration absorber in the low temperature regenerator 30 passes through the eliminator 35 between the low temperature regenerator 30 and the condenser 40 and flows into the condenser 40. The refrigerant vapor introduced into the condenser 40 (including the refrigerant vapor flowing through the outlet pipe 33) is condensed by the cooling water heat transfer pipe group 41. The condensed water condensed in the condenser 40 and the condensed water flowing through the outlet pipe 33 may be stored in the lower portion of the condenser 40.

The condensed water from the condenser 40 flows into the evaporator 50 through the condensed water pipe 42 and the cold water flowing through the cold water heat pipe group 51 inside the evaporator 50 while the condensed water evaporates in the evaporator 50 . The refrigerant, which has been accumulated in the evaporator, is dispersed in the upper portion of the evaporator again through the refrigerant circulation pipe (52), and evaporation is continuously induced.

The refrigerant vapor generated in the evaporator 50 passes through the eliminator 15 disposed between the evaporator 50 and the absorber 10 and enters the absorber 10 to be absorbed in the high concentration absorber dispersed in the absorber 10 . The absorption heat generated in this process is cooled by the group of cooling water heat transfer tubes 11 on the absorber side.

Specifically, the cold water is introduced into the absorption type system 1 through the cold water pipe 53 and then discharged. Since the cold water pipe 53 includes the cold water heat pipe group 51 inside the evaporator, the cold water flows along the cold water heat pipe group 51 and the temperature is lowered.

Thus, the absorption system can be frozen or cooled / warmed through cold water having a lower temperature or cooling water having a higher temperature. In other words, a latent heat generated through the circulation cycle of regeneration (separation of the refrigerant in the absorption liquid), condensation of the refrigerant vapor, evaporation of the refrigerant, and absorption is used.

In general, the efficiency of the absorption system is expressed by COP (Coefficient of Performance), and COP is expressed by the ratio of the refrigerating capacity (calories) to the amount of heat input to the regenerator. Therefore, the higher the COP, the better the efficiency of the system.

However, the COP generally means system efficiency at full load, i.e., system efficiency at maximum cooling capacity operation. Therefore, the COP does not represent the system efficiency in partial load operation.

In the field where the actual system is installed, the frequency at which the system operates at partial load (for example, 25%, 50% or 75% of maximum load) is greater than the frequency at which the system is operated at full load.

The system efficiency considering this partial load is called Integrated part load value (IPLV). Therefore, it is important to increase the system efficiency at the part load, that is, the IPLV.

As shown in FIG. 2, the absorption system operates the pump P1 with an inverter frequency set as a function of the hot regenerator and the cooling water inlet temperature. That is, the temperature of the high-temperature regenerator indirectly related to the efficiency of the system and the temperature of the cooling water are detected to control the circulation amount of the absorption liquid.

Here, the circulation amount of the absorption liquid means a flow rate which is substantially transferred to the high-temperature regenerator through the low-concentration absorption liquid through the pump P1. Therefore, ideally, the flow rate which is optimal for the current load must be transferred to the high-temperature regenerator through the pump P1.

However, in the conventional absorption type system, when the partial load operation is performed, there is a problem that the efficiency of the partial load is remarkably reduced because the pump P1 is operated in an arbitrary circulating amount state. That is, there is a problem that the flow rate optimal for the current load can not be transferred to the high-temperature regenerator through the pump P1.

Specifically, the conventional absorption type system is operated with uniformly determined absorption liquid circulation amount through the function shown in FIG. 2 even when the characteristics of each model, for example, the COP, the capacity, and the operation conditions are different. That is, the inverter frequency is determined in an inverter frequency map, that is, a look-up table, which is determined by the temperature of the cooling water inlet to be sensed and the temperature of the high temperature regenerator. Of course, it can be said that the lookup table is created based on the function shown in FIG.

Therefore, there is a problem that unnecessary increase in energy and cost is required beyond the point that the efficiency of the system becomes optimum. This is because the inverter frequency is not determined according to the above-described model-specific characteristics or operating conditions, and the inverter frequency is determined simply by the cooling water inlet temperature and the high temperature regenerator temperature.

On the other hand, there is a problem that it takes a lot of cost and time to design and test each model for controlling the circulation amount having such an optimum point.

Therefore, there is a need to provide an absorption system or a control method thereof that can improve the efficiency of an absorption system, particularly IPVL. In addition, it is necessary to provide a circulation amount control method that can be applied to a general purpose irrespective of a model, rather than a circulation amount control method that varies depending on the model.

The present invention basically aims to solve the above-mentioned problems.

Through the embodiments of the present invention, it is intended to provide general control logic that can be applied to an absorption system. Therefore, it is desirable to reduce the necessity of newly developing control logic for controlling the amount of absorption liquid circulation for each model.

Through the embodiments of the present invention, it is intended to provide an absorption system capable of effectively improving the IPLV of an absorption system and a control method including the same.

An embodiment of the present invention is to provide an absorption system capable of continuous feedback control and more precisely controlling the amount of circulation and a control method including the same.

It is an object of the present invention to provide an absorption type system and a control method including the same that can perform safety control according to the variation of the internal liquid level of the high temperature regenerator, thereby improving reliability and efficiency.

To achieve the above object, according to an embodiment of the present invention, there is provided an evaporator comprising: an evaporator; A cold water pipe for introducing cold water into the evaporator and discharging the cold water from the evaporator after heat exchange; An absorber for absorbing the refrigerant vapor introduced from the evaporator into the absorption liquid; A high-temperature regenerator for heating the low-concentration absorbent introduced from the absorber to separate and regenerate the absorbent liquid into a refrigerant vapor and a medium-concentration absorbent; A pump for supplying the low concentration absorbing liquid from the absorber to the high temperature regenerator; A low-temperature regenerator for heating the medium-concentration absorbent introduced from the high-temperature regenerator to separate the regeneration medium into a refrigerant vapor and a high-concentration absorbent; And a control unit for variably controlling the inverter frequency value of the pump so that the temperature difference between the inlet and outlet through the inlet and outlet temperature difference of the cold water pipe satisfies a predetermined temperature difference.

The control unit may calculate the frequency value through feedback control and apply the calculated frequency value to the pump. In addition, the feedback control may be a PID control.

The temperature difference may be a linearly continuous value rather than a specific value. Thus, the temperature difference to be fed back may be a continuous value. Of course, there may be a problem of how much the difference between the lowest temperature difference and the highest temperature difference is broken down. If the degree of granularity is large, more precise control will be possible.

It is possible to continuously calculate frequency values through such continuous temperature difference values. Therefore, the PID control can be performed, and it becomes possible to more precisely control the amount of circulation.

According to an embodiment of the present invention, there is provided an absorption system including an evaporator, an absorber, a high temperature regenerator, a low temperature regenerator, and a pump for supplying an absorption liquid from the absorber to the high temperature regenerator, And a controller for controlling the frequency value to be a maximum value by calculating the frequency value through feedback control and applying the calculated inverter frequency value to the pump to maximize the cold water inlet and outlet temperature difference proportional to the COP of the absorption system .

According to an embodiment of the present invention there is provided an absorption system comprising an evaporator, an absorber, a high temperature regenerator, a low temperature regenerator, and a pump for supplying an absorbent from the absorber to the high temperature regenerator, And a control unit for calculating the inverter frequency value of the pump through feedback control and controlling the pump frequency to be controlled by the pump so as to control the circulation amount of the absorption liquid so that the cold water inlet / outlet temperature difference proportional to the COP is maximized .

The feedback control is preferably a PID control.

According to an embodiment of the present invention, there is provided a control method of an absorption system including an evaporator, an absorber, a high temperature regenerator, a low temperature regenerator, and a pump for supplying an absorbing liquid to the high temperature regenerator from the absorber, The operating phase of the high temperature regenerator; A temperature judging step of judging a temperature difference between an inlet and an outlet of a cold water pipe for introducing cold water into the evaporator and discharging the cold water from the evaporator after heat exchange; And a frequency control step of calculating an inverter frequency value of the pump through feedback control and applying the calculated inverter frequency value to the pump.

Preferably, the temperature determination step and the frequency control step are repeated at predetermined time intervals.

Preferably, the inlet temperature of the cold water pipe is fixed to a predetermined value at the beginning of the operation step and before a predetermined time elapses, and the temperature determination step is performed.

It is preferable that the absorption liquid level in the high temperature regenerator is sensed and either the operation stop of the pump, the re-operation, the frequency control of the pump, and the operation stop of the entire absorption system are performed according to the sensing result.

When the absorption liquid level is sensed at the maximum liquid level, the operation of the pump can be stopped.

After the pump is stopped, when the absorption liquid level is sensed at the intermediate liquid level, the pump can be reactivated.

When the absorption liquid level is sensed at the lowest liquid level, the operation of the entire absorption type system can be stopped.

In operation of the pump, when the absorption liquid level is sensed between the highest liquid level and the lowest liquid level, the pump is preferably operated through frequency control.

Therefore, the control logic in the steady state and the control logic in the abnormal state can be performed in parallel.

Through the embodiments of the present invention, it is possible to provide general control logic that can be applied to an absorption system. Therefore, it is possible to reduce the necessity of newly developing the control logic for controlling the circulation amount of the absorption liquid for each model.

Through the embodiments of the present invention, it is possible to provide an absorption system capable of effectively improving the IPLV of the absorption system and a control method including the same.

It is possible to provide an absorption type system and a control method including the absorption type system that can control the circulation amount more precisely by enabling continuous feedback control through embodiments of the present invention.

It is possible to provide an absorption type system and a control method including the absorption type system that can perform safety control according to the variation of the internal liquid level of the high temperature regenerator through the embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an absorption system that may be applied to an embodiment of the prior art or of the present invention; FIG.
2 is a graph showing an inverter frequency map for a conventional pump control;
3 is a graph showing a correlation between a circulation amount and a cold water inlet / outlet temperature difference;
4 is a simplified block diagram of an absorption system in accordance with an embodiment of the present invention;
5 is a control system diagram of an absorption type system according to an embodiment of the present invention; And
Figure 6 is a control flow chart of an absorption system in accordance with an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

An embodiment according to the present invention relates to a method for controlling the amount of circulation of an absorption liquid and an absorption system using the same. Therefore, in this embodiment, it is basically possible to use the same or similar configurations as the above-described absorption type system configurations. Thus, a redundant description of each configuration may be omitted.

COP can be expressed by the ratio of the amount of freezing heat to the amount of heat input to the regenerator, as described above. The amount of heat input to the regenerator means the amount of heat input to the regenerator, and the amount of freezing heat means the amount of heat required to generate cold water.

Specifically, it can be said that the amount of freezing heat is directly proportional to the cold water flow rate and the cold water inlet / outlet temperature difference (cold water inlet temperature-cold water outlet temperature). Therefore, cold water inlet / outlet temperature difference can be considered as a factor directly related to the COP, that is, the efficiency of the system.

In the embodiment of the present invention, a control method capable of improving the efficiency of the system based on the cold water inlet / outlet temperature difference and an absorption system using the control method can be provided. That is, the system efficiency can be directly increased because it is based on the cold water inlet / outlet temperature difference which is directly related to the temperature of the regenerator, which is indirectly related to the efficiency of the system, and not the cooling water temperature.

3 is a graph showing the relationship between the circulating amount of absorption liquid and the cold water inlet / outlet temperature difference in the absorption type system.

The circulation amount of the absorption liquid may be a mass per unit time (Kg / sec) of the absorption liquid supplied to the high temperature regenerator 20 through the pump P1 shown in FIG. The cold water inlet / outlet temperature difference may be the difference between the cold water temperature flowing into the evaporator 50 and the cold water temperature discharged from the evaporator 50 (° C). That is, it can be said that it is the difference between the inlet temperature and the outlet temperature of the cold water pipe 53 for the evaporator 50.

As shown in FIG. 3, the cold water inlet / outlet temperature difference increases as the circulation amount increases, but tends to decrease after a certain value. That is, the optimum point (A) exists in the optimum section in which the temperature difference between the cold water inlet and outlet is the largest according to the circulation amount. This is a unique characteristic of the system irrespective of the model or operating conditions of the system.

This means that the cold water inlet / outlet temperature difference deviates from the optimum range when the circulation amount is excessive or excessive. In addition, the fact that the cold water inlet / outlet temperature difference is small means that the COP is small as described above. Therefore, in order to increase the COP, it is necessary to control the circulation amount so that the temperature difference between the cold water inlet and outlet is in the optimum range.

3 shows the relationship between the coolant inlet / outlet temperature difference and the circulation amount under the operating conditions for the specific load. That is, as the operating conditions change, the graph can be moved to the left and right, and thus the amount of circulation having the optimum section can also be changed.

For example, if the graph of Fig. 3 shows the relationship between cold water inlet and outlet temperature difference and circulation amount at a partial load of 50%, the graph can be moved to the right at a partial load condition of 75%. Likewise, at 25% partial load conditions, the graph can be moved to the left. This is because, as the load increases, the amount of circulation generally increases.

Therefore, it is preferable to control the circulation amount so that the system is operated in the optimum section in which the cold water inlet / outlet temperature difference is the largest, even if the operating conditions and the model are changed. This is because the cold water inlet / outlet temperature difference is largest because COP directly increases in each operating condition.

In practice, absorption systems are often operated with partial loads rather than peak loads. Therefore, it is important to increase the IPLV in consideration of this. The integrated part load value (IPLV), ie, the system efficiency considering partial load, can be calculated by multiplying the efficiency at each partial load by the frequency of operation.

For example, it is 0.01 (1% duty cycle) for maximum load (100%), 0.42 (42% duty cycle) for 75% partial load, 0.45 (45% duty cycle) for 50% partial load and 0.12 (12% frequency of use), respectively, to calculate the IPLV. Therefore, it can be seen that the system efficiency in the operating conditions with a large number of frequencies has a greater influence on the IPLV. Furthermore, it can be seen that if the maximum efficiency is achieved at each partial load, IPLV is also maximized.

According to the embodiments of the present invention, the optimal COP can be obtained even in each partial load, so that the optimum IPLV can be obtained as a whole.

4 shows a simplified block diagram of a system for implementing an embodiment of the present invention.

The controller 100 controls the combustion of the high temperature regenerator to regenerate the refrigerant in the high temperature regenerator.

The high temperature regenerator 20 may be provided with a liquid level sensor 200 for sensing the liquid level of the absorbing liquid. The controller 100 can control the operation of the pump P1 or the operation of the entire system according to the liquid level sensed by the liquid level sensor 200. [ Specifically, the pump and the system operation control according to the liquid level sensor are related to the safety of the system, and details thereof will be described later.

The control unit 100 controls the inverter frequency of the pump P1 to control the amount of absorption liquid to be supplied to the high temperature regenerator 20 through the pump P1, that is, the circulation amount. Specifically, the inverter frequency of the pump P1 can be variably controlled based on the cold water inlet / outlet temperature difference.

To this end, a temperature sensor 400 for sensing the inlet temperature of the cold water pipe 53 and a temperature sensor 300 for sensing the outlet temperature of the cold water pipe 53 may be provided. The control unit 100 calculates the temperature difference between the inlet and outlet through the temperature sensed by the sensors 300 and 400. Then, the control unit 100 controls the circulation amount so that the temperature difference becomes the maximum value using the calculated temperature difference. That is, the inverter frequency of the pump is variably controlled to control the circulation amount so as to have the maximum efficiency under the current operating condition.

If the pump is operated at a specific inverter frequency to obtain the optimum circulation amount, the specific inverter frequency may be fixed unless the operating conditions are varied. Then, when the operation condition is changed, that is, the increase or decrease of the load occurs, the inverter frequency can be variably controlled so as to have the optimum circulation amount again.

A method of controlling the inverter frequency of the pump so as to have the optimum circulation amount can be explained with reference to FIG.

First, when the circulation amount is excessively small, the controller 100 may control the pump P1 so that the circulation amount gradually increases. Of course, after the temperature difference is fed back, it is possible to control the amount of circulation to gradually increase until the temperature difference reaches the maximum value.

Conversely, when the circulation amount is excessive, the control unit 100 can control the pump P1 so that the circulation amount gradually decreases. Similarly, after the temperature difference is fed back, it is possible to control the amount of circulation to gradually decrease until the temperature difference reaches the maximum value.

Here, the amount of circulation is excessively small or excessive can be easily grasped through the correlation between the feedback temperature difference and the frequency variable. For example, if the temperature difference is small despite increasing the frequency, it can be seen that the circulation amount is excessive. In addition, if the temperature difference is small even though the frequency is decreased, it can be seen that the circulation amount is inferior.

Therefore, the circulation amount can be variably controlled so that the temperature difference increases, and the operation of the pump can be controlled so that the circulation amount having the maximum temperature difference can be obtained.

The frequency control of the pump, that is, the frequency control of the pump based on the cold water inlet temperature difference, is preferably performed during steady state operation. In other words, it is preferable that the driving logic in an abnormal state is parallel with the steady state driving logic through the frequency control of the pump.

In other words, it is preferable to determine whether the current system is operating in a normal state or an abnormal state, and control the system operation by either the steady state operation logic or the abnormal state operation logic according to the determined result.

Fig. 5 shows the control logic of the absorption system in the steady state and in the abnormal state.

In the dual effusion absorbing system, the liquid level of the heavy concentration absorbent in the high temperature regenerator 20 should be controlled within a certain range. As described above, the absorption liquid is circulated through the pump P1. The flow rate of the absorbing liquid supplied through the pump P1 should be adjusted so that the circulating amount corresponding to the steady state is ideally transferred from the absorber 10 to the high temperature regenerator 20 because the circulating amount varies depending on the operating condition.

However, since the high-temperature regenerator 20 is generally a high-temperature environment, continuous liquid level measurement is very difficult. Therefore, a liquid level switch that detects only a specific position is applied to an actual product.

Specifically, as shown in Fig. 5, a liquid level switch for detecting three liquid levels in general can be used. A liquid level switch capable of detecting the highest (first level), middle (second level) and lowest (third level) can be used. Such a liquid level switch can be realized by using an electrode rod. The details of such a liquid level switch will be obvious to those skilled in the art, so a detailed description thereof will be omitted.

The liquid level information through the liquid level switch is transmitted to the controller 100, and the controller 100 can control the operation of the pump P1 and the entire system based on the liquid level information.

Steady state means that the liquid level runs between maximum and minimum. In the steady state, the inverter frequency of the pump is varied to operate the pump based on the cold water inlet temperature difference described above. Therefore, the circulation rate can be controlled so that the cold water inlet temperature difference directly related to the system efficiency is maximized.

However, the liquid level information is not continuously fed back. In other words, only the three liquid level information can be grasped through the liquid level information. Specifically, continuous liquid level information between the maximum liquid level and the minimum liquid level can not be grasped.

Therefore, in the steady state operation, an error between the flow rate supplied to the high temperature regenerator and the flow rate discharged from the high temperature regenerator can be accumulated. However, according to the present embodiment, the error can be remarkably reduced as compared with the conventional steady state operation mode (using the frequency map according to the cooling water inlet temperature and the high temperature regenerator temperature). This is because there is a very strong correlation between the maximum efficiency and the optimum flow rate as shown in Fig.

On the other hand, when the error is accumulated and the liquid level in the high temperature regenerator reaches the maximum liquid level, the controller 100 stops driving the pump P1. That is, when the level 1 is sensed, the control unit 100 stops driving the pump P1. After the pump stops driving, the liquid level gradually decreases, and the liquid level reaches the level 2. That is, when the level 2 is sensed, the controller 100 restarts the pump P1, and then performs steady state operation, that is, pump frequency control, as described above.

In addition, the error can accumulate and the liquid level in the high temperature regenerator can reach the lowest liquid level. This can be said to be an abnormality in the system. Accordingly, when the lowest level (level 3) is sensed, the control unit 100 stops driving the system premise.

As described above, according to the embodiment of the present invention, the inverter frequency of the pump is variably controlled on the basis of the cold water inlet temperature difference under the steady state. In addition, based on the level of liquid level in the high-temperature regenerator, the pump is shut down, restarted, and system operation under abnormal conditions. Of course, the steady state can also be determined based on the level of the liquid in the high temperature regenerator.

As shown in FIG. 5, the controller 100 can control operation of the pump and the system through switching according to the liquid level information. That is, the system can be operated differently through a simple switching circuit.

That is, the frequency control in the on state of the pump P1 or the on state of the pump P1, the off state of the pump P1 and the shutdown of the system can be easily implemented.

Hereinafter, the control flow for steady-state operation according to the embodiment of the present invention will be described in detail with reference to FIG.

When the system operation starts (S10), the operation of the high temperature regenerator is started. That is, the high temperature regenerator starts burning the fuel to regenerate the refrigerant (S20). Of course, at this time, the pump will start to drive at the inverter frequency of the initially set pump.

After the start of the combustion and the start of the pump, the inlet / outlet temperature of the cold water is detected after a predetermined time (S30) (S40). That is, the respective temperatures are detected through the cold water pipe outlet temperature sensor 300 and the cold water pipe inlet temperature sensor 400. Then, the cold water inlet / outlet temperature difference is calculated through the detected temperatures (S50). This may be referred to as a temperature judgment step (S40, S50).

The control unit 100 calculates an inverter frequency for driving the pump P1 based on the calculated temperature difference (S60). That is, the inverter frequency is calculated so that the calculated temperature difference becomes maximum. Then, the calculated frequency is applied to the pump P1 (S70) to control the operation of the pump. Therefore, it is possible to calculate the inverter frequency value of the pump and apply the calculated inverter frequency value to the pump in the frequency control step (S60, S70).

Here, the frequency operation S60 may be performed through feedback control. That is, the frequency can be varied so as to maximize it through the temperature difference fed back.

For example, a cold water inlet temperature can be detected at 12 ° C and a cold water outlet temperature can be detected at 9 ° C. In this case, the calculated temperature difference is 3 ° C. At this time, the control unit 100 may calculate the frequency value applied to the pump to increase by a predetermined value, and apply the calculated frequency value to the pump P1 so that the temperature difference becomes higher based on the calculated temperature difference.

The pump P1 is operated at the calculated frequency value, and the temperature difference can be fed back again after a predetermined time (S30). In this case, the fed cold water inlet / outlet temperature difference may be 4 ° C.

Therefore, it is preferable that the temperature determination step and the frequency control step described above are repeated at predetermined time intervals. In other words, it is preferable that the detection of the cold water inlet temperature and the cold water outlet temperature is performed after a predetermined time elapses.

The variable operating frequency of the pump means that the amount of circulation is variable. Therefore, it takes a sufficient time to change the variable of the circulation amount to the variable of the inlet / outlet temperature difference of the cold water. That is, sufficient time is required until the variation of the circulation amount sufficiently affects the system. For this purpose, the temperature determination step and the frequency control step are preferably repeated at predetermined time intervals.

The repetition of the temperature determination step and the frequency control step may be performed until the temperature difference becomes maximum. The maximum temperature difference may be preset to 5 [deg.] C, and may vary depending on the system. In addition, depending on other factors or the load conditions of the system, the temperature difference at which the efficiency becomes the optimum point may be less than 5 占 폚. Therefore, the maximum temperature difference may be determined to be a different value by varying the frequency value in the current load.

The load of the system can be varied without being fixed. For example, the operation condition may be changed to a 50% partial load after being operated at a partial load of 75%, and the increase or decrease of the load may repeatedly occur.

Therefore, it is preferable that the temperature judging step and the frequency controlling step are continuously repeated at predetermined time intervals in a steady state. The predetermined time may vary depending on the scale of the system, the model, the operating environment (variable frequency of load, etc.).

The time determination step (S30) for determining whether or not the predetermined time has elapsed can be performed in a different form depending on whether the operation is started or not.

That is, immediately after the initial stage of the operation of the system (S10, S20), the cold water inlet / outlet temperature difference may not represent the efficiency of the present system. This is because the operation of the system is before the steady state is reached.

Therefore, it is preferable that the cold water inlet temperature is set to 12 deg. C (S35), and the cold water inlet / outlet temperature difference is calculated (S50). This is because, at the beginning of operation, the cold water inlet temperature may be much higher than the normal cold water inlet temperature of 12 ° C. Accordingly, when the temperature difference is calculated using the actual cold water inlet temperature and the frequency value is calculated using the temperature difference, the error of the frequency value can be remarkably increased. In order to prevent such a problem in advance, it is preferable to calculate the temperature difference by fixing the cold water inlet temperature at 12 占 폚 at the beginning of the operation stage.

Meanwhile, when the system is operated in a steady state, it is preferable to determine whether the predetermined time has elapsed after varying the frequency value in the time determination step S30. Therefore, the variable input of the frequency value can be repeated every predetermined time.

After the frequency control step (S60, S70), a step S80 for judging whether or not operation is performed may be performed.

The operation determination step may be regarded as a step of determining whether or not the vehicle is in an abnormal state, as described above. In addition, it may be regarded as a step of determining whether or not it is in a normal state.

When the liquid level of the high temperature regenerator 20 is detected between the minimum and the maximum, the temperature determination steps S40 and S50 and the frequency control steps S60 and S70 described above may be performed. That is, if it is determined as a normal state, the temperature determination steps S40 and S50 and the frequency control steps S60 and S70 may be repeatedly performed.

When the liquid level of the high temperature regenerator 20 is detected to the minimum, the driving of the system is stopped (S90).

On the other hand, when the liquid level of the high temperature regenerator 20 is detected at the maximum, the driving of the pump is stopped. When the second level is detected in the determination step S80 after the lapse of time, the operation of the pump can be resumed through the immediately preceding frequency or the initial set frequency.

Thus, the safety control logic in the abnormal state and the pump control logic in the steady state can be performed in parallel.

According to the above-described embodiment, the inverter frequency of the pump can be controlled so that efficiency can be maximized in a steady state. Therefore, as the amount of circulation increases, the possibility that the liquid level is detected as the highest level is very low. In addition, the possibility that the liquid level is detected as the lowest level is also very low.

Therefore, the entire system can be stably operated, and safety control can be performed even if an abnormal state occurs.

10: absorber 20: high temperature regenerator
30: low temperature regenerator 40: condenser
50: Evaporator P1: Absorbent circulation pump
100: control unit 200: liquid level sensor
300: cold water pipe outlet temperature sensor 400: cold water pipe inlet temperature sensor

Claims (15)

evaporator;
A cold water pipe for introducing cold water into the evaporator and discharging the cold water from the evaporator after heat exchange;
An absorber for absorbing the refrigerant vapor introduced from the evaporator into the absorption liquid;
A high-temperature regenerator for heating the low-concentration absorbent introduced from the absorber to separate and regenerate the absorbent liquid into a refrigerant vapor and a medium-concentration absorbent;
A pump for supplying the low concentration absorbing liquid from the absorber to the high temperature regenerator;
A low-temperature regenerator for heating the medium-concentration absorbent introduced from the high-temperature regenerator to separate the regeneration medium into a refrigerant vapor and a high-concentration absorbent; And
And a control unit for variably controlling the inverter frequency value of the pump so that the inlet / outlet temperature difference satisfies a preset temperature difference through an inlet / outlet temperature difference of the cold water pipe. The method according to claim 1,
Wherein the control unit calculates the frequency value through feedback control and applies the calculated frequency value to the pump. 3. The method of claim 2,
Wherein the feedback control is a PID control. 1. An absorption system comprising an evaporator, an absorber, a high temperature regenerator, a low temperature regenerator, and a pump for supplying the absorbent from the absorber to the high temperature regenerator,
And a control unit for calculating the inverter frequency value of the pump through feedback control and applying the calculated inverter frequency value to the pump to control the cold water inlet / outlet temperature difference that is proportional to the efficiency (COP) of the absorption system to be a maximum Absorption system. 5. The method of claim 4,
Wherein the feedback control is a PID control. 1. An absorption system comprising an evaporator, an absorber, a high temperature regenerator, a low temperature regenerator, and a pump for supplying the absorbent from the absorber to the high temperature regenerator,
And a control unit for calculating an inverter frequency value of the pump through feedback control and applying the calculated inverter frequency value to the pump so as to control the circulation amount of the absorption liquid so that the cold water inlet / outlet temperature difference proportional to the COP of the absorption system is maximized. The method according to claim 6,
Wherein the feedback control is a PID control. A control method of an absorption system including an evaporator, an absorber, a high temperature regenerator, a low temperature regenerator, and a pump for supplying an absorbing liquid to the high temperature regenerator in the absorber,
Operating the high temperature regenerator;
A temperature judging step of judging a temperature difference between an inlet and an outlet of a cold water pipe for introducing cold water into the evaporator and discharging the cold water from the evaporator after heat exchange; And
And a frequency control step of calculating an inverter frequency value of the pump through feedback control and applying the calculated inverter frequency value to the pump. 9. The method of claim 8,
Wherein the temperature determination step and the frequency control step are repeated at predetermined time intervals. 9. The method of claim 8,
Wherein the temperature determining step is performed by fixing the inlet temperature of the cold water pipe to a predetermined value at an initial stage of the operation step and before a predetermined time elapses. 11. The method according to any one of claims 8 to 10,
A control method of an absorption type system in which the absorption liquid level in the high temperature regenerator is sensed and either the operation stop of the pump, the re-operation, the frequency control of the pump, or the operation stop of the entire absorption system is performed according to the sensing result . 12. The method of claim 11,
And stopping the operation of the pump when the absorption liquid level is sensed at the maximum liquid level. 13. The method of claim 12,
And when the absorption liquid level is sensed at an intermediate liquid level after the pump is stopped, the pump is restarted. 12. The method of claim 11,
And stopping the operation of the entire absorption system when the absorption liquid level is sensed at the lowest liquid level. 15. The method of claim 14,
Wherein the pump is operated through frequency control when the absorption liquid level is sensed between the highest liquid level and the lowest liquid level during operation of the pump.

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