JP5140366B2 - Control method of absorption refrigerator - Google Patents

Description

  The present invention relates to an absorption refrigerator, and more particularly to a method for controlling a rare liquid pump for returning an absorbing liquid from an absorber to a high-temperature regenerator.

In general, absorption refrigerators are operated using lithium bromide as the absorbent and water as the refrigerant, and the low-concentration absorption liquid returned from the absorber to the high-temperature regenerator is heated by the high-temperature regenerator to separate the refrigerant vapor. Then, the absorption liquid having a medium concentration due to the separation of the refrigerant vapor is introduced into the low-temperature regenerator, and the refrigerant vapor separated by the high-temperature regenerator is passed through the low-temperature regenerator through a pipe line, and the medium-concentration absorption liquid is removed. After heating and re-separating the refrigerant vapor, it becomes a refrigerant liquid and is introduced into the condenser. Absorbed liquid whose concentration has been increased by re-separating the refrigerant vapor in the low-temperature regenerator is introduced into the absorber by the concentrated liquid pump, and the refrigerant vapor re-separated from the intermediate-concentrated absorbent is introduced into the condenser, and the pipeline The refrigerant is condensed by the cooling water passing through the condenser and becomes a refrigerant liquid, and the refrigerant liquid condensed when passing through the low-temperature regenerator is joined at the bottom of the condenser. The refrigerant liquid collected at the bottom of the condenser is introduced into the evaporator, and is sprayed from the spraying device on the top of the evaporator to the heat transfer pipe via the refrigerant pump, and cold / hot water passing through the evaporator via the heat transfer pipe ( Evaporates by heat exchange with working water. Thereby, the cold / hot water is cooled and introduced into a load to perform a cooling operation. On the other hand, the refrigerant vapor evaporated in the evaporator is introduced into the absorber, introduced from the low-temperature regenerator, and absorbed by the high-concentration absorbing liquid sprayed from the spraying device above the absorber. Then, the absorbing liquid that has become a low concentration by absorbing the refrigerant vapor is returned to the high-temperature regenerator by the dilute liquid pump. This type of absorption refrigerator is disclosed in Patent Document 1, for example.
JP2000-74521

  In the absorption refrigerator as described above, the combustion heating of the burner in the high-temperature regenerator is adjusted according to the fluctuation of the load, and the amount of refrigerant vapor generated by being separated from the low-concentration absorbent is controlled. Thereby, it controls so that the circulation amount of a refrigerant | coolant liquid becomes appropriate with respect to the fluctuation | variation of load. In addition, it is necessary to adjust the amount of the low-concentration absorbing liquid that is returned from the absorber to the high-temperature regenerator due to load fluctuations. For this reason, by changing the inverter motor frequency of the dilute liquid pump, the amount of low-concentration absorbent returned from the absorber to the high-temperature regenerator is adjusted so that the amount of circulated absorbent is appropriate for load fluctuations. I have control. In order to appropriately cope with the fluctuation of the load, a control line that graphs the relationship between the temperature of the high temperature regenerator and the inverter motor frequency of the rare liquid pump is provided, and the temperature sensor provided in the high temperature regenerator is used. The absorption liquid temperature was measured, the frequency of the inverter motor of the diluted liquid pump was determined from the control line based on the measured value, and the diluted liquid pump was controlled by the inverter frequency.

  However, in the conventional example as described above, since there is only one type of control line for determining the inverter frequency of the diluted liquid pump from the high temperature regenerator temperature, the inverter frequency of the diluted liquid pump is controlled with respect to load fluctuations. Even at a high temperature regenerator temperature, there was a difference between the high load operation and the low load operation, and it was not necessarily an appropriate control.

  Therefore, the present invention provides two types of control lines, one for high loads and one for low loads, so that the dilution pump can be controlled against load fluctuations during both high load operation and low load operation. An object of the present invention is to provide a control method for an absorption chiller in which the inverter frequency can be appropriately controlled.

In order to achieve the above-mentioned object, claim 1 of the present invention is such that the absorption liquid having a low concentration by absorbing the refrigerant vapor by the absorber is returned to the high-temperature regenerator and heated by the high-temperature regenerator. The refrigerant vapor is separated, and the absorbing liquid having a medium concentration is introduced into the low temperature regenerator, and the refrigerant vapor separated in the high temperature regenerator passes through the low temperature regenerator via a pipe, After the refrigerant vapor is re-separated by heating the concentration absorption liquid, the refrigerant liquid is introduced into the bottom of the condenser as a refrigerant liquid, and the refrigerant liquid is re-separated by the low-temperature regenerator to increase the concentration of the absorption liquid. The refrigerant vapor introduced into the absorber by the pump and re-separated by the low-temperature regenerator is introduced into the condenser, and condensed into the refrigerant liquid by the cooling water passing through the condenser through the pipeline, This refrigerant liquid merges with the refrigerant liquid at the bottom of the condenser and evaporates. In addition to being introduced into the heat transfer pipe through the refrigerant pump from the evaporator spraying device and passing through the heat transfer pipe and supplied to the cooling load, it becomes refrigerant vapor, The refrigerant vapor is introduced into the absorber, and the high-concentration absorbing liquid introduced from the low-temperature regenerator in this absorber is sprayed from the spraying device of the absorber to absorb the refrigerant vapor. In the absorption chiller configured to be returned to the high-temperature regenerator via a rare liquid pump,
The rare liquid pump selects one of the plurality of inverter frequency control lines using the absorption liquid temperature of the high-temperature regenerator and the cooling water temperature as parameters according to the load state of the absorption refrigerator. The inverter frequency is controlled , based on the operating conditions determined from the factors of the amount of heating in the burner of the high temperature regenerator, the absorption liquid temperature of the high temperature regenerator, and the concentration of the high concentration absorption liquid, It is determined which inverter frequency control line is used, the inverter frequency is calculated from a predetermined function equation using the high temperature regenerator temperature and the cooling water temperature, and the operation frequency of the dilute liquid pump is controlled by the inverter frequency. With
A change from the currently selected inverter frequency control line to another inverter frequency control line due to a change in the operating conditions; and
When the inverter frequency of the diluted liquid pump decreases, a value obtained by subtracting a predetermined value from the current operating frequency is compared with a frequency value calculated by a predetermined function formula, and the larger value is set to the diluted liquid pump. As compared with the case where only the frequency calculated by the predetermined function equation is used, the operation frequency of the dilute liquid pump is controlled to be gradually decreased.
When the inverter frequency of the diluted liquid pump increases, the inverter frequency is used as the operating frequency of the diluted liquid pump so that the operating frequency of the diluted liquid pump is gradually decreased when the inverter frequency decreases. Compared to the control in the case of controlling to the above, by immediately increasing the operation frequency of the dilute liquid pump, it is controlled so as to become the capacity output of the refrigerator corresponding to a sudden load increase,
The gist of the control method of the absorption chiller is characterized by this.

According to a second aspect of the present invention, in the absorption refrigerator according to the first aspect, the function equation gives a relationship between the high temperature regenerator temperature and the frequency F1, and is between the minimum and maximum frequencies. A specific function form in which the temperature coefficient k in the temperature region before and after the high temperature regenerator temperature at the inflection point is different, that is,
F1 = {X (hg) + Y (ci)} × k
Where X (hg); high temperature regenerator temperature
Y (ci); cooling water temperature
And having
The deflection point can be changed.
The temperature coefficient k changes the increase / decrease of the frequency of the rare liquid pump according to the high temperature regenerator temperature.
It is characterized by that.

  According to the first aspect of the present invention, the high temperature regenerator and the low temperature regenerator are provided, the low concentration absorbent is returned from the absorber to the high temperature regenerator by the rare liquid pump, and the refrigerant vapor is separated by heating with the high temperature regenerator. In the absorption refrigerating machine in which the refrigerant vapor is passed through a low temperature regenerator and the medium concentration absorbing liquid introduced from the high temperature regenerator to the low temperature regenerator is heated to re-separate the refrigerant vapor. Since the pump is a method of selecting and controlling any one of the plurality of inverter frequency control lines using the absorption liquid temperature of the high-temperature regenerator and the cooling water temperature as parameters, during high load operation In either case of low load operation, the inverter frequency of the dilute liquid pump can be appropriately controlled with respect to load fluctuations. Thereby, the efficiency improvement of an absorption refrigerator and improvement of COP (coefficient of performance) can be aimed at.

According to the invention of the claim 1, wherein the plurality of inverter frequency control lines, there is any one of the inverter frequency control lines are selected by the load state of the absorption chiller, the high temperature generator It is determined which inverter frequency control line is used based on the operating conditions determined from the factors of the amount of heating in the burner, the absorption liquid temperature of the high-temperature regenerator, and the concentration of the high concentration absorption liquid, and the rare liquid Since it is a method of controlling the inverter frequency of the pump, it is possible to perform appropriate control in accordance with actual operation.

According to the invention of the first aspect, the change of the operating conditions, the inverter frequency control line that is currently selected, if it is changed to another inverter frequency control lines, the inverter frequency of the rare pump In this case, since the inverter frequency is controlled to gradually decrease, the COP during the low load operation can be improved while maintaining the stability of the operation state.

According to the invention of the first aspect, the change of the operating conditions, the inverter frequency control line that is currently selected, if it is changed to another inverter frequency control lines, the inverter frequency of the rare pump In this case, since the inverter frequency is controlled to increase immediately, the capacity output of the absorption chiller corresponding to a sudden load can be obtained.

  Next, an embodiment of a control method for an absorption refrigerator according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an absorption chiller for explaining a control method of the absorption chiller according to the present invention. In FIG. 1, 1 is a high-temperature regenerator, 2 is a low-temperature regenerator, 3 is a condenser, 4 is an evaporator, and 5 is an absorber, which uses lithium bromide as an absorbent and water as a refrigerant. This is an absorption refrigerator.

  In this absorption refrigerator, the low-concentration absorbing liquid that has absorbed the refrigerant vapor in the absorber 5 is returned to the high-temperature regenerator 1 by the dilute pump 6, but the high-temperature regenerator 7 and the high-temperature regenerator are in the middle of the pipeline R4. It passes through the heat exchanger 8.

  In the high temperature regenerator 1, the low concentration absorbent returned from the absorber 5 is heated by the burner 1 a to separate the refrigerant vapor. The refrigerant vapor separated by the high-temperature regenerator 1 passes through the low-temperature regenerator 2 via the pipe R1 and is introduced to the bottom of the condenser 3 via the refrigerant drain heat recovery unit 9. A flow rate variable means 12 including a flow rate control valve 10 and a bypass pipe 11 is provided on the downstream side of the refrigerant drain heat recovery unit 9.

  In the flow rate varying means 12, the flow rate control valve 10 is opened during high load operation. As a result, the refrigerant liquid flows through both the pipe line on the flow rate control valve 10 side and the bypass pipe line 11, and an appropriate amount of refrigerant liquid can be introduced into the condenser 3 during high load operation. On the other hand, the flow control valve 10 is closed during low load operation. As a result, the refrigerant liquid flows only on the bypass pipe line 11 side, and a refrigerant liquid amount suitable for the low load operation can be introduced into the condenser 3. In this way, it is possible to circulate an appropriate amount of refrigerant liquid by controlling the amount of refrigerant liquid for high load and low load.

In the low-temperature regenerator 2, the medium concentration absorbing liquid generated by the separation of the refrigerant vapor in the high-temperature regenerator 1 is introduced into the low-temperature regenerator 2 after passing through the high-temperature heat exchanger 8 via the pipe R2. Heated by the refrigerant vapor passing through the low temperature regenerator 2, the refrigerant vapor is separated again. The refrigerant vapor re-separated by the low-temperature regenerator 2 is introduced into the condenser 3 and is cooled and condensed by the cooling water passing through the condenser 3 through the pipe line R3 to become a refrigerant liquid. Accumulate at the bottom. This refrigerant liquid merges with the refrigerant liquid introduced into the bottom of the condenser 3 through the flow rate varying means 12 as described above.

  In the evaporator 4, the refrigerant liquid accumulated at the bottom of the condenser 3 is introduced through the pipe R 6, and is sprayed from the sprayer 4 a disposed in the upper part of the evaporator 4 by the coolant pump 13. Heat exchange is performed with cold / hot water passing through the evaporator 4 via the path R7. As a result, the refrigerant liquid evaporates and cools the cold / hot water, and the cooled cold / hot water is introduced into the load to perform a cooling operation.

  In the absorber 5, as described above, after the high-concentration absorbing liquid from the low-temperature regenerator 2 passes through the low-temperature heat exchanger 7 through the conduit R 8 by the concentrated liquid pump 14, it is sprayed from the sprayer 5 a of the absorber 5. Is done. The high-concentration absorbing liquid sprayed from the sprayer 5a is cooled by exchanging heat with the cooling water passing through the absorber 5 through the pipe R3, and absorbs the refrigerant vapor introduced from the evaporator 4. The absorption liquid whose concentration has been reduced by absorbing the refrigerant vapor is returned to the high-temperature regenerator 1 after passing through the low-temperature heat exchanger 7 and the high-temperature heat exchanger 8 through the pipe R4 by the dilute liquid pump 6 as described above. It is.

  In the absorption refrigerator having such a configuration, control is performed to increase the circulation amount of the refrigerant liquid and the absorption liquid at a high load, and to reduce the circulation amount of the refrigerant liquid and the absorption liquid at a low load. Therefore, based on the control line formed by calculating the inverter frequency of the rare liquid pump using the absorption liquid temperature of the high temperature regenerator (hereinafter simply referred to as the high temperature regenerator temperature) and the cooling water temperature as parameters, The inverter frequency of the rare liquid pump is determined and controlled from the high temperature regenerator temperature that changes according to the fluctuation.

  In the present embodiment, two types of control lines for high load and low load are prepared as the control line, and one of them is selected to control the inverter frequency of the rare liquid pump. .

  In addition, whether one of the plurality of control lines is selected is selected depending on whether the operating condition of the absorption chiller is in a low load state as shown in FIG. It has become. Specifically, whether or not it is in the low load operation state is detected by the high temperature regenerator temperature, the combustion amount of the burner 1a that supplies heat to the high temperature regenerator 1, or the concentration sensor SC. The determination is based on whether or not the concentration of the high-concentration absorbing liquid is equal to or higher than a predetermined value. The concentration of the high-concentration absorbing liquid can be calculated from the outlet temperature of the condenser 3 and the concentrated liquid temperature sensor LG without providing the concentration sensor SC.

  FIG. 3 is an example of a flowchart showing whether to select high load control or low load control. In this case, the low-load flowchart is employed only in the cooling operation when 30 minutes or more have elapsed after the (burner) ignition and the dilution operation is not being performed. Then, two types of dilute liquid pump control contents, a high load flowchart and a low load flowchart, are provided, and these control contents are selected according to the above conditions.

FIG. 6 is a graph showing details of the control line at the time of high load operation, FIG. 7 is a graph showing details of the control line at the time of low load operation, and the rare liquid pump 6 is shown in FIG. 6 and FIG. The operation frequency is controlled from the minimum frequency Fmin to the maximum frequency Fmax based on such calculation results. For example, when the cooling water inlet temperature is high, the lower control line is selected, and when the cooling water inlet temperature is low, the upper control line is selected (in the actual control example, the lowermost control line has a cooling water inlet temperature of, for example, 32 ° C. In the case, the uppermost control line is for example when the cooling water inlet temperature is 22 ° C.).

  An inflection point is provided between the minimum frequency and the maximum frequency, and the coefficient calculated by the before and after the inflection point is switched. Note that this inflection point can be changed.

  FIG. 4 shows an example of a flowchart for high load control. In this flowchart, a1 is a predetermined value set as the high temperature regenerator temperature, and F1 is a parameter using the high temperature regenerator temperature and the cooling water inlet temperature as parameters. The frequency of the dilute liquid pump obtained from the arithmetic expression is as shown in FIG. In addition, (F1 = {X1 (hg) + Y1 (ci)} × k) shown in FIG. 4 is a function equation obtained by experiment, but is programmed as a calculation equation to a control device (not shown) of the absorption refrigerator. Or the values shown in FIG. 6 may be stored in the control device as a database, and the inverter frequency of the rare liquid pump 6 may be obtained from the high temperature regenerator temperature and the cooling water temperature. Is possible.

  FIG. 5 shows an example of a flowchart for low load control. In this flowchart, F1 is a dilute solution obtained from an arithmetic expression using the high-temperature regenerator temperature (refrigerant vapor) and the cold / hot water inlet temperature as parameters. It is the inverter frequency of the pump. When the high load control flowchart is used (F1 = {X1 (hg) + Y1 (ci)} × k), the specific numerical values are as shown in FIG. When F is used (F1 = {X2 (hg) + Y2 (ci)} × k), the values are as shown in FIG. Here, (F1 = {X2 (hg) + Y2 (ci)} × k) is a function equation obtained by experiment, but is assumed to be programmed to a control device (not shown) of the absorption refrigerator as an arithmetic expression. Alternatively, the value shown in FIG. 6 may be stored in the control device as a database, and the inverter frequency of the rare liquid pump 6 may be obtained from the high temperature regenerator temperature and the cooling water temperature. In the high-load control flowchart and the low-load control flowchart, an inflection point (can be changed) is provided, and the increase / decrease in the frequency of the rare liquid pump is changed by the high-temperature regenerator temperature. The arithmetic expression (F1 = {X1 (hg) + Y1 (ci)} × k) in the flowchart is the same as the arithmetic expression in the flowchart for high load control. Here, hg is the high temperature regenerator temperature and ci is the cooling water temperature.

  Further, in this low load control flowchart, a comparison of (A-a16> F1) is performed. This is a selection between the high load control flowchart and the low load control flowchart shown in FIG. In the case of shifting from low load control to low load control, the operation frequency of the dilute liquid pump 6 is lowered on average. At this time, the change of the operation frequency A obtained by the above flow chart is gradually changed to dilute the dilute liquid. (Low-concentration absorption liquid) The rapid decrease in the circulation rate is suppressed. That is, the value obtained by subtracting the predetermined value a16 from the current operating frequency A is compared with the calculated frequency F1, and the larger value is adopted as the operating frequency of the rare liquid pump. As a result, the high-load control is shifted to the low-load control, and even if the calculation result in the flowchart is a low value that is far from the current operating frequency, the frequency is gradually reduced as actual control. On the contrary, when the operation is shifted from the low load control to the high load control and the operation frequency increases, this control is not performed to improve the followability.

  As described above, when the control line is changed from a high load to a low load, the calculated value of the inverter frequency of the rare liquid pump also changes, but when it decreases, it is gradually lowered. “A-a16> F1?” In the flowchart of FIG. 5 is that portion, and is decreased by a16 (Hz). On the other hand, when it rises, it is made to operate immediately as the inverter frequency. The effect of this is that when the inverter frequency is lowered, it is gradually lowered, so that the COP (coefficient of performance) at the time of low load operation can be improved while maintaining the stability of the operation state. . In addition, since the inverter frequency is increased immediately, it is possible to output the capacity of the absorption chiller corresponding to a sudden load increase.

  3 to 5, there is a flowchart of FIG. 3 as the control of the present embodiment. Depending on the operating condition of the absorption refrigerator (“During dilution operation?” Or the like of FIG. 3), One of the low-load flowcharts shown in FIG. 5 is selected. In other words, the flowcharts shown in FIGS. 4 and 5 are subroutines of the flowchart shown in FIG.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a refrigerating type refrigerator, and by appropriately using two types of control lines for high load and low load, the inverter motor frequency of a rare liquid pump can be appropriately and finely adjusted. It becomes possible to control.

It is a schematic block diagram of the absorption refrigerator for demonstrating the control method of the absorption refrigerator which concerns on this invention. In the control method of an absorption refrigerating machine concerning the present invention, it is a graph which shows an example of two kinds of control lines for high load and low load. It is an example of the flowchart which shows which is selected for high load control or low load control in the control method of the absorption refrigerator which concerns on this invention. In the control method of an absorption refrigerating machine concerning the present invention, it is an example of a flow chart for high load control. In the control method of an absorption refrigerating machine concerning the present invention, it is an example of a flow chart for low load control. In the control method of an absorption refrigerating machine concerning the present invention, it is a graph which shows the details of the control line at the time of high load operation. In the control method of an absorption refrigerating machine concerning the present invention, it is a graph which shows the details of the control line at the time of low load operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High temperature regenerator 1a Burner 2 Low temperature regenerator 3 Condenser 4 Evaporator 4a Spreader 5 Absorber 6 Diluted liquid pump 7 Low temperature heat exchanger 8 High temperature heat exchanger 9 Refrigerant drain heat recovery device 10 Flow control valve 11 Bypass line 12 Flow rate variable means 13 Refrigerant pump 14 Concentrate pump

Claims (2)

Absorbing liquid that has absorbed refrigerant vapor at the absorber and has a low concentration is returned to the high-temperature regenerator, and the refrigerant vapor is separated by heating with this high-temperature regenerator, and the absorbing liquid that has reached a medium concentration is the low-temperature regenerator. And the refrigerant vapor separated by the high-temperature regenerator passes through the low-temperature regenerator via a pipe line, and then the refrigerant vapor is re-separated by heating the medium concentration absorbing liquid. Into the bottom of the condenser,
The absorption liquid having a high concentration by re-separating the refrigerant vapor in the low-temperature regenerator is introduced into the absorber by a concentrated liquid pump,
Refrigerant vapor re-separated by the low-temperature regenerator is introduced into a condenser, and is condensed by cooling water passing through the condenser through a pipeline to become a refrigerant liquid.
This refrigerant liquid joins with the refrigerant liquid at the bottom of the condenser and is introduced into the evaporator, and is spread from the spraying device of the evaporator to the heat transfer pipe via the refrigerant pump,
It becomes refrigerant vapor by exchanging heat with cold / hot water that passes through this heat transfer tube and is supplied to the cooling load,
This refrigerant vapor is introduced into the absorber,
In this absorber, the high concentration absorbent introduced from the low-temperature regenerator is sprayed from the spraying device of the absorber to absorb the refrigerant vapor,
In the absorption refrigerator having a configuration in which the absorption liquid having a low concentration is returned to the high-temperature regenerator via a dilute pump,
The rare liquid pump selects one of the plurality of inverter frequency control lines using the absorption liquid temperature of the high-temperature regenerator and the cooling water temperature as parameters according to the load state of the absorption refrigerator. The inverter frequency is controlled , based on the operating conditions determined from the factors of the amount of heating in the burner of the high temperature regenerator, the absorption liquid temperature of the high temperature regenerator, and the concentration of the high concentration absorption liquid, It is determined which inverter frequency control line is used, the inverter frequency is calculated from a predetermined function equation using the high temperature regenerator temperature and the cooling water temperature, and the operation frequency of the dilute liquid pump is controlled by the inverter frequency. With
A change from the currently selected inverter frequency control line to another inverter frequency control line due to a change in the operating conditions; and
When the inverter frequency of the diluted liquid pump decreases, a value obtained by subtracting a predetermined value from the current operating frequency is compared with a frequency value calculated by a predetermined function formula, and the larger value is set to the diluted liquid pump. As compared with the case where only the frequency calculated by the predetermined function equation is used, the operation frequency of the dilute liquid pump is controlled to be gradually decreased.
When the inverter frequency of the diluted liquid pump increases, the inverter frequency is used as the operating frequency of the diluted liquid pump so that the operating frequency of the diluted liquid pump is gradually decreased when the inverter frequency decreases. Compared to the control in the case of controlling to the above, by immediately increasing the operation frequency of the dilute liquid pump, it is controlled so as to become the capacity output of the refrigerator corresponding to a sudden load increase,
A control method of an absorption refrigerator characterized by the above. The function formula gives the relationship between the high temperature regenerator temperature and the frequency F1, and the temperature before and after the high temperature regenerator temperature at the inflection point provided between the minimum and maximum frequencies. Inherent functional form with different temperature coefficient k in the region, i.e.
F1 = {X (hg) + Y (ci)} × k
Where X (hg); high temperature regenerator temperature
Y (ci); cooling water temperature
And having
The deflection point can be changed.
The temperature coefficient k changes the increase / decrease of the frequency of the rare liquid pump according to the high temperature regenerator temperature.
The method for controlling an absorption refrigerator according to claim 1.

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