JP2000241039A - Controller for absorption refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a parallel solution circulation system double effect absorption refrigerating machine in which a coefficient of performance can be increased as high as possible while avoiding crystallization. SOLUTION: The controller for absorption refrigerating machine has a mechanism for regulating the ratio of flow rate between a solution being distributed from a low temperature heat exchanger 5 to a high temperature heat exchanger 4 and a solution being distributed from the low temperature heat exchanger 5 to a low temperature regenerator 12. Circulation of solution is controlled such that the concentration of a high concentration solution flowing from the low temperature heat exchanger 5 toward an absorber 22 has a specified crystal margin for the crystallization concentration corresponding to the solution temperature and the distribution ratio of solution is regulated depending on the refrigeration load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-effect absorption refrigerator, and more particularly to a low-concentration solution supplied from an absorber which flows into a high-temperature regenerator through a low-temperature heat exchanger and a high-temperature heat exchanger. Also, the present invention relates to a parallel solution circulation type double effect absorption refrigerator in which a part of a solution flowing out of a low temperature heat exchanger flows into a low temperature regenerator.

[0002]

2. Description of the Related Art As shown in FIG. 1, a double effect absorption refrigerator comprises an upper body comprising a condenser (11) and a low temperature regenerator (12), an evaporator (21) and an absorber (22). Lower body, high temperature regenerator (3) with built-in burner (31), high temperature heat exchanger (4), low temperature heat exchanger
(5), etc. are connected to each other by piping, and the solution pump (6)
The solution (absorbent) is circulated between the high temperature regenerator (3), the low temperature regenerator (12) and the absorber (22) to realize a refrigeration cycle.

Here, as shown in the figure, a low-concentration solution supplied from an absorber (22) flows into a high-temperature regenerator (3) through a low-temperature heat exchanger (5) and a high-temperature heat exchanger (4). At the same time, a part of the solution flowing out of the low-temperature heat exchanger (5) is
While flowing into 2), high-temperature heat exchanger (3)
The high-concentration solution supplied via (4) is supplied to the low-temperature regenerator (12)
There is known a double solution absorption refrigerator of a parallel solution circulation type in which a solution flowing out of a chiller flows into an absorber (22) through a low-temperature heat exchanger (5).

The absorption chiller generally has a higher coefficient of performance when the concentration of the solution circulating in the refrigerator is higher. However, as the solution concentration increases, the risk of crystallization increases. Therefore, in order to avoid crystallization and to secure the highest possible coefficient of performance, the solution concentration and temperature are monitored at the places where the risk of crystallization is highest. It is necessary to control the amount of circulating solution so as to always keep a certain margin.

[0005]

In the double-effect absorption refrigerator of the parallel solution circulation system, there is a possibility that the solution flowing out from the low-temperature heat exchanger (5) to the absorber (22) is crystallized. Since the temperature is high, the concentration and temperature of the solution at the outlet of the low-temperature heat exchanger (5) (hereinafter referred to as the low-temperature heat exchanger outer tube outlet) are monitored. It is necessary to control the solution circulation amount so as to keep a margin.

At this time, in the absorption refrigerator of the parallel solution circulation system, the solution flowing out of the high-temperature heat exchanger (4) to the low-temperature heat exchanger (5), that is, the solution at the outlet of the high-temperature heat exchanger tube. Attention must also be paid to the crystallization of. In order to reduce the risk of crystallization, the flow rate of the solution distributed from the low-temperature heat exchanger (5) to the high-temperature heat exchanger (4) should not be changed from the low-temperature heat exchanger (5) to the low-temperature regenerator (12). ) May be set to a small ratio (hereinafter, referred to as a solution distribution ratio) of the solution to be distributed, but this will lower the coefficient of performance. Conversely, when the solution distribution ratio is set large, the coefficient of performance increases, but the risk of crystallization increases. Thus, in the relationship between the coefficient of performance and the crystallization, how to set the solution distribution ratio becomes a problem.

In order to reduce the risk of crystallization,
It is sufficient to increase the margin of solution concentration at the outlet of the low-temperature heat exchanger tube, but this reduces the coefficient of performance. vice versa,
When the concentration margin value of the solution outside the low temperature heat exchanger tube is reduced, the coefficient of performance increases, but the risk of crystallization increases. Thus, in the relationship between the coefficient of performance and crystallization, how to set the concentration margin value becomes a problem.

It is an object of the present invention to provide a control device capable of obtaining a high coefficient of performance while avoiding crystallization in a double-effect absorption refrigerator of a parallel solution circulation system.

[0009]

FIG. 4 shows a parallel solution circulation type double effect absorption refrigerating machine in which the concentration margin value of the solution at the outlet of the low temperature heat exchanger tube is constant irrespective of the refrigeration load. The relationship between the refrigeration load and the coefficient of performance when the solution circulation amount is controlled is expressed using the solution distribution ratio as a parameter. As shown in the drawing, the coefficient of performance generally increases as the solution distribution ratio increases, but the difference in the coefficient of performance due to the solution distribution ratio is very small in a small range of the refrigeration load.

This is for the following reason. That is, the coefficient of performance is greatly affected by the amount of heat consumed as sensible heat for warming the solution flowing into the high-temperature regenerator to the saturation temperature. Therefore, if the refrigeration load is the same, the coefficient of performance generally increases as the amount of solution flowing into the high-temperature regenerator decreases. If the solution distribution ratio is different, the amount of the solution flowing into the high-temperature regenerator naturally differs, so that the coefficient of performance also differs. However, when the refrigeration load is small, the entire solution circulation amount is small, so that the difference in the amount of inflow into the high-temperature regenerator due to the difference in the solution distribution ratio is smaller than that when the refrigeration load is large. As a result, the difference in the coefficient of performance becomes smaller.

FIG. 5 is a plot of the concentration and the temperature at the outlet of the low-temperature heat exchanger and at the outlet of the high-temperature heat exchanger when the same control as in FIG. 4 is performed. When the solution distribution ratio on the low-temperature regenerator side is small, the concentration and temperature of the solution at the outlet of the high-temperature heat exchanger tube move from the crystal line to the safe side, and the risk of crystallization is reduced.

From the above, the solution distribution ratio on the low-temperature regenerator side is set to be large when the refrigeration load is large, and to be small when the refrigeration load is small. That is, as the load changes,
As shown by the thick line in FIG. 6, the concentration and the temperature of the solution are changed. As a result, as shown by the thick line in FIG.
A high coefficient of performance can be ensured over the entire refrigeration load, and the risk of crystallization can be suppressed at low loads.

In the double-effect absorption refrigerator of the parallel solution circulation type according to the present invention, the flow rate of the solution distributed from the low-temperature heat exchanger (5) to the high-temperature heat exchanger (4) and the low-temperature heat exchanger ( 5)
Equipped with a solution distribution ratio adjusting mechanism for adjusting the ratio of the flow rate of the solution distributed to the low-temperature regenerator (12) from the low-temperature heat exchanger (5) to the absorber (22) The circulation amount of the solution is controlled and the solution distribution ratio is adjusted according to the refrigeration load so that the concentration of the high-concentration solution has a certain crystallization margin with respect to the crystallization concentration corresponding to the temperature of the solution.

[0014] Specifically, the low-temperature heat exchanger (5) to the absorber
(1) first calculating means for calculating the crystallization concentration of the high-concentration solution flowing out toward (22), and calculating the target concentration by adding a predetermined margin to the calculated crystallization concentration. A second calculating means for calculating a deviation of the concentration of the solution flowing out from the low-temperature heat exchanger (5) toward the absorber (22) from the target concentration, and a third calculating means for calculating the deviation based on the calculated deviation. First control means for controlling the amount of circulating solution, and depending on the refrigeration load,
A second method for controlling a solution distribution ratio, which is a ratio of a solution flow rate from the low-temperature heat exchanger (5) to the low-temperature regenerator (12) to a solution flow rate from the low-temperature heat exchanger (5) to the high-temperature heat exchanger (4). Equipped with control means.

The circulation amount of the solution is controlled by decreasing the circulation amount when the target concentration is higher than the solution concentration, and increasing the circulation amount when the target concentration is lower than the solution concentration. Control of the solution distribution ratio is as follows:
When the refrigeration load is large, the solution distribution ratio is set large, and when the refrigeration load is small, the solution distribution ratio is set small. As a result, a high coefficient of performance can be secured for the entire refrigeration load, and at the time of a low load, the risk of crystallization can be suppressed.

FIG. 9 shows a solution circulation control in a double-effect absorption refrigerator of a parallel solution circulation type such that a margin of concentration of the solution at the outlet of the low-temperature heat exchanger tube is constant regardless of the refrigeration load. Is a graph showing the relationship between the refrigeration load and the coefficient of performance at the time of performing. As shown in the drawing, the coefficient of performance generally increases as the concentration margin value decreases, but in a small range of the refrigeration load, the difference in the coefficient of performance due to such concentration margin value is extremely small.

This is for the following reason. That is, the coefficient of performance is greatly affected by the amount of heat consumed as sensible heat for warming the solution flowing into the high-temperature regenerator to the saturation temperature. Therefore, if the refrigeration load is the same, the coefficient of performance generally increases as the amount of solution flowing into the high-temperature regenerator decreases. If the concentration margin value is large, the solution circulation amount increases in an attempt to reduce the solution concentration as a whole. Therefore, the amount of the solution flowing into the high-temperature regenerator also increases, and the coefficient of performance decreases. However, when the refrigeration load is small, the total amount of the solution circulated is small, so the difference in the amount of inflow into the high-temperature regenerator due to the difference in the concentration margin value is smaller than that when the refrigeration load is large. As a result, the difference in the coefficient of performance also decreases.

FIG. 10 is a plot of the concentration and temperature at the outlet of the low-temperature heat exchanger and at the outlet of the high-temperature heat exchanger when the same control as in FIG. 2 is performed. When the concentration margin of the solution at the outlet of the low-temperature heat exchanger tube is large, the concentration and temperature of the solution at the outlet of the high-temperature heat exchanger tube move from the crystal wire to the safe side, and the risk of crystallization is reduced. .

From the above, it can be seen that the margin of concentration of the solution at the outlet of the low-temperature heat exchanger tube is small when the refrigeration load is large,
Increase when the refrigeration load is small. That is, as the load changes, the concentration and temperature of the solution change as shown by the thick line in FIG. As a result, as shown by the thick line in FIG. 12, a high coefficient of performance can be secured for the entire refrigeration load, and at the time of a low load, the risk of crystallization can be suppressed.

In the parallel solution circulation type double effect absorption refrigerator according to the present invention, the low-temperature heat exchanger (5) is connected to the absorber.
The circulation amount of the solution is controlled so that the concentration of the high-concentration solution flowing out toward (22) has a certain crystallization margin with respect to the crystallization concentration corresponding to the temperature of the solution, and the refrigeration load is adjusted. To change the crystal margin.

Specifically, from the low-temperature heat exchanger (5) to the absorber
(1) first calculating means for calculating a crystallization concentration of the high-concentration solution flowing out toward (22), and second calculating means for calculating a crystal margin based on a refrigeration load. Third calculating means for calculating a target concentration based on the crystallization concentration and the crystal margin, and calculating a deviation of the concentration of the solution flowing from the low-temperature heat exchanger (5) toward the absorber (22) with respect to the target concentration. And a control means for controlling the solution circulation amount based on the calculated deviation.

In controlling the solution circulation amount, the solution circulation amount is reduced when the target concentration is higher than the solution concentration, and the solution circulation amount is increased when the target concentration is lower than the solution concentration. When the refrigerating load is large, the crystal margin is set small, and when the refrigerating load is small, the crystal margin is set large. As a result, a high coefficient of performance can be secured for the entire refrigeration load, and at the time of a low load, the risk of crystallization can be suppressed.

[0023]

According to the double solution absorption refrigerator of the parallel solution circulation type according to the present invention, a high coefficient of performance can be obtained while avoiding crystallization.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Two examples in which the present invention is applied to a double solution absorption refrigerator of a parallel solution circulation type shown in FIG. 1 will be specifically described with reference to the drawings.

[0025]First embodiment  In the double effect absorption refrigerator of the present embodiment, as shown in FIG.
Thus, the solution distribution point at the outlet of the low-temperature heat exchanger (5) and the high-temperature heat
Low temperature heat exchange with control valve (7) interposed between exchangers (4)
Of solution to be distributed from heat exchanger (5) to high temperature heat exchanger (4)
Is distributed from the low-temperature heat exchanger (5) to the low-temperature regenerator (12)
Adjust the solution flow ratio.

FIG. 3 shows the control system and the flow of calculation of the absorption refrigerator of the present embodiment. The high-temperature regenerator solution inflow Wshw, the low-temperature regenerator solution inflow Wswl, the absorber pressure Pa, and the absorption pressure are shown. Reactor outlet solution temperature Tsa, high temperature regenerator pressure Phg, and high temperature regenerator outlet solution temperature Tshg, low temperature regenerator pressure Plg, low temperature regenerator outlet solution temperature Tslg, cold water inlet temperature Tci, cold water outlet temperature Tco, and cold water flow Wc It has a plurality of measuring instruments for measuring.

First, based on the measurement data obtained from these measuring instruments, the solution concentration outside the low-temperature heat exchanger tube, which is the monitoring point, is estimated. It is conceivable to directly measure the solution concentration, but since the concentration measurement device is expensive, estimation is performed by the following calculation.

(Operation 1) Absorber refrigerant pressure Pa is used to determine absorber refrigerant saturation temperature Trs, high temperature regenerator pressure Phg is used to determine high temperature regenerator refrigerant temperature Trsa, and low temperature regenerator pressure Plg is used to specify low temperature regenerator refrigerant saturation temperature Trslg. Is estimated. The relationship fp between the saturation pressure P and the saturation temperature Trs is given by, for example, the following tube equation.

[0029]

(Equation 1)

(Operation 2) From the absorber refrigerant saturation temperature Trsa and the absorber outlet solution temperature Tsa, the absorber outlet solution concentration Xsw
And the high temperature regenerator outlet solution concentration Xshg higher than the high temperature regenerator refrigerant saturation temperature Trshg and the high temperature regenerator outlet solution temperature Tshg, and the low temperature regenerator outlet solution lower than the low temperature regenerator refrigerant saturation temperature Trslg and the low temperature regenerator outlet solution temperature Tslg. The density Xslg is estimated. Relation fst between temperature Ts and concentration Xs of lithium bromide aqueous solution
Is expressed by the following relational expression using the saturation temperature Trs of water that balances the temperature and concentration (McNeely's expression).

[0031]

(Equation 2)

(Calculation 3) High-temperature regenerator solution inflow Wswh,
Absorber outlet solution concentration Xsw, high temperature regenerator outlet solution concentration Xsh
g, the low-temperature regenerator outlet solution flow rate Wshg, and the low-temperature regenerator solution inflow amount Wswl, the absorber outlet solution concentration Xsw, and the low-temperature regenerator outlet solution temperature Xslg are estimated. For the estimation, the following equation is used based on the fact that the amount of solution entering and leaving the high-temperature regenerator in the steady state is the same, and the amount of solution entering and exiting the low-temperature regenerator is the same.

[0033]

(Equation 3)

(Operation 4) The solution concentration Xsh at the outlet of the high temperature regenerator
g, the low-temperature regenerator outlet solution concentration Xsm, the high-temperature regenerator outlet solution flow rate Wshg, and the low-temperature regenerator outlet solution flow rate Wslg are used to estimate the low-temperature heat exchanger out-of-tube solution concentration Xsm. For the estimation, the following equation is used based on the fact that the amount of the solution that flows in and out of the low-temperature heat exchanger tube in the steady state is the same.

[0035]

(Equation 4)

(Calculation 5) From the temperature at the outlet of the low-temperature heat exchanger tube, the crystallization concentration corresponding thereto is estimated.

(Operation 6) A target concentration is determined by subtracting a preset concentration margin value from the crystallization concentration outside the low temperature heat exchanger tube.

(Operation 7) A deviation exsm obtained by subtracting the low-temperature heat exchanger outside-tube solution concentration Xsm from the target concentration is input to the first controller (8), and the solution pump is adjusted so as to approach the target concentration.
The rotation frequency of (6) is controlled to adjust the solution circulation amount.
That is, when the solution concentration is lower than the target concentration, the solution circulation amount is decreased, and when the solution concentration is higher than the target concentration, the solution circulation amount is increased. If the first controller (8) is a PID controller, the rotation frequency fspu of the solution pump
Is determined by the following equation. Here, Kp ₁ , Ki ₁ and Kd ₁
Is a PID parameter, which is given an appropriate value in advance.

[0039]

(Equation 5)

Simultaneously with the control of the solution circulation amount, the solution distribution ratio is controlled as follows. (Operation 8) The solution distribution ratio Dlg is estimated from the high-temperature regenerator solution inflow Wswh and the low-temperature regenerator solution inflow Wswl. The following formula is used for estimation.

[0041]

(Equation 6)

(Operation 9) The refrigeration load factor Lc is estimated from the chilled water inlet temperature Tci, the chilled water outlet temperature Tco, and the chilled water flow rate Wc. For the estimation, the following equation is used, where Cpw is the chilled water specific heat, and Q is the rated refrigeration capacity.

[0043]

(Equation 7)

(Operation 10) A target solution distribution ratio is determined from the refrigeration load factor Lc. Target value rDlg of solution distribution ratio
Is, for example, changed in proportion to the refrigeration load factor Lc, the relationship frdlg is as follows.

[0045]

(Equation 8)

(Operation 11) A deviation edlg obtained by subtracting the solution distribution ratio target value Dlg from the solution distribution ratio target value rDlg is input to the second controller (81), and the control valve (so that the solution distribution ratio approaches the target value). Adjust the opening of 7). That is, when the refrigeration load is large, the solution distribution ratio is set large, and when the refrigeration load is small, the solution distribution ratio is set small. If the second controller (81) is a PID controller, the valve opening degree V is determined by the following equation. Here, Kp ₂ , Ki ₂ and Kd ₂ are P
This is an ID parameter, and an appropriate value is given in advance.

[0047]

(Equation 9)

The setting of the target concentration is not limited to the method of calculating the target concentration X2 by subtracting a certain concentration margin value Dx from the crystallization concentration X1 determined from the measured temperature as shown in FIG. Instead, a method that takes into account both the concentration allowance and the temperature allowance can be adopted. In this case, the difference between the temperature measurement value T1 and the crystal temperature T2 determined from the target concentration X2 is used.
When (T1−T2) is larger than the predetermined temperature margin value Dt, the target density X2 is adopted, but the temperature difference (T1−T2) is used.
When T2) is equal to or smaller than the predetermined temperature margin value Dt, the target concentration X3 having the temperature margin value Dt for the crystal line is set.

According to the above-described control, the concentration and temperature of the solution change as shown by the thick line in FIG. 6 with the change of the refrigeration load, and as a result, as shown by the thick line in FIG. A high coefficient of performance can be ensured over the entire load, and the risk of crystallization can be suppressed at low loads.

[0050]Second embodiment  FIG. 8 shows the control system of the absorption refrigerator of this embodiment and the flow of calculation.
And the same plurality of measuring instruments as those in the first embodiment.
Based on the measurement data obtained from these measuring instruments
Then, the following control is performed.

First, the solution concentration outside the tubes of the low-temperature heat exchanger, which is the monitoring point, is estimated. Although it is conceivable to directly measure the solution concentration, since the concentration measuring device is expensive, estimation is performed by the following calculation.

(Operation 1) Absorber refrigerant saturation temperature Trs from absorber pressure Pa, high-temperature regenerator refrigerant saturation temperature Trshg from high-temperature regenerator pressure Phg, and low-temperature regenerator refrigerant saturation temperature Trslg from low-temperature regenerator pressure Plg. Is estimated. Note that the relationship fp between the saturation pressure P and the saturation temperature Trs is given by, for example, the above equation (1).

(Operation 2) From the absorber refrigerant saturation temperature Trsa and the absorber outlet solution temperature Tsa, the absorber outlet solution concentration Xsw is calculated as follows:
The high-temperature regenerator refrigerant saturation temperature Trshg, the high-temperature regenerator outlet solution concentration Xshg from the high-temperature regenerator outlet solution temperature Tshg, the low-temperature regenerator refrigerant saturation temperature Trslg, and the low-temperature regenerator outlet solution concentration Xslg from the low-temperature regenerator outlet solution temperature Tslg. Is estimated. The relationship fst between the temperature Ts and the concentration Xs of the aqueous lithium bromide solution is obtained by using the saturation temperature Trs of water that balances the temperature and the concentration.
It is represented by the McNeely equation of Equation 2 above.

(Calculation 3) High-temperature regenerator solution inflow amount Wswh,
Absorber outlet solution concentration Xsw, high temperature regenerator outlet solution concentration Xsh
g, the low-temperature regenerator outlet solution flow rate Wshg, and the low-temperature regenerator solution inflow amount Wswl, the absorber outlet solution concentration Xsw, and the low-temperature regenerator outlet solution concentration Xslg are estimated. Equation 3 is used for the estimation.

(Operation 4) The solution concentration Xsh at the outlet of the high temperature regenerator
g, the low-temperature regenerator outlet solution concentration Xsm, the high-temperature regenerator outlet solution flow rate Wshg, and the low-temperature regenerator outlet solution flow rate Wslg are used to estimate the low-temperature heat exchanger out-of-tube solution concentration Xsm. The above equation is used for estimation.
Is used.

(Operation 5) From the temperature of the solution at the outlet of the low-temperature heat exchanger tube, a crystallization concentration corresponding thereto is estimated.

(Operation 6) The refrigeration load factor Lc is estimated from the chilled water inlet temperature Tci, the chilled water outlet temperature Tco, and the chilled water flow rate Wc. Equation 7 is used for the estimation.

(Operation 7) A concentration margin value is determined from the refrigeration load factor Lc. Assuming that the concentration margin value xofs changes linearly with respect to the refrigeration load factor, for example, the relation fxo
fs is expressed by the following equation.

[0059]

(Equation 10)

(Calculation 8) The target concentration is determined by subtracting the concentration margin value set in (Calculation 7) from the crystallization concentration outside the low temperature heat exchanger tube.

(Operation 9) A deviation exsm obtained by subtracting the low-temperature heat exchanger outside-tube solution concentration Xsm from the target concentration is calculated by the controller (8).
Input to 2), and adjust the solution circulation amount by controlling the rotation frequency of the solution pump so as to approach the target concentration. That is, when the solution concentration is lower than the target concentration, the solution circulation amount is decreased, and when the solution concentration is higher than the target concentration, the solution circulation amount is increased. If the controller (82) is a PID controller, the rotation frequency fspu of the solution pump can be determined by the above (5).

In the setting of the target concentration value, as in the first embodiment, a constant concentration margin value Dx is subtracted from the crystallization concentration X1 determined from the temperature measurement value as shown in FIG. , The temperature difference (T
When (1−T2) is larger than the predetermined temperature margin value Dt, the target concentration X2 is adopted, and when the temperature difference (T1−T2) is equal to or smaller than the predetermined temperature margin value Dt, the target concentration is further reduced with respect to the crystal line. The target density X3 having the temperature margin value Dt can be set.

According to the above-described control, the concentration and temperature of the solution change as shown by the bold line in FIG. 11 with the change of the load. As a result, as shown by the bold line in FIG. A high coefficient of performance can be ensured, and the risk of crystallization can be suppressed at low load.

In the above-described first embodiment, the control of the solution distribution ratio is not limited to the example of changing the refrigerating load in a linear function, but adopts various relations that increase monotonically with the refrigerating load. I can do it. Further, the control of the solution distribution ratio is not limited to a method in which the flow rate is continuously changed by a control valve (7) provided in a pipe extending toward the high-temperature heat exchanger (4), but is controlled by a low-temperature regenerator.
(12) Various methods such as a method using a control valve provided on a pipe extending to the side, a method using a control valve provided on both pipes, a method using a damper instead of the control valve, a method that changes the flow rate stepwise, etc. A scheme can be adopted. Further, as the control method, various control methods such as fuzzy control and feedforward control can be adopted. or,
Similarly, in the second embodiment, various relationships that monotonically decrease with respect to the refrigeration load can be used for controlling the concentration margin value with respect to the refrigeration load.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a configuration of a parallel solution circulation type double effect absorption refrigerator in which the present invention is implemented.

FIG. 2 is a diagram showing a control valve interposed between a low-temperature heat exchanger and a high-temperature heat exchanger.

FIG. 3 is a block diagram showing a configuration of a control system and a flow of calculation in the first embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a refrigeration load and a coefficient of performance.

FIG. 5 is a graph showing the solution concentration and the solution temperature at the outlet of the low-temperature heat exchanger tube and at the outlet of the high-temperature heat exchanger tube.

FIG. 6 is a graph showing changes in solution temperature and concentration in the first embodiment.

FIG. 7 is a graph showing a relationship between a refrigeration load and a coefficient of performance in the first embodiment.

FIG. 8 is a block diagram showing a configuration of a control system and a flow of calculation in a second embodiment of the present invention.

FIG. 9 is a graph showing a relationship between a refrigeration load and a coefficient of performance.

FIG. 10 is a graph showing the solution concentration and the solution temperature at the outlet of the low-temperature heat exchanger tube and the outlet of the high-temperature heat exchanger tube.

FIG. 11 is a graph showing the movement of the solution temperature and the concentration in the second embodiment.

FIG. 12 is a graph showing a relationship between a refrigeration load and a coefficient of performance in the second embodiment.

FIG. 13 is a graph illustrating a method for setting a target density.

[Explanation of symbols]

 (12) Low temperature regenerator (22) Absorber (3) High temperature regenerator (4) High temperature heat exchanger (5) Low temperature heat exchanger (6) Solution pump (7) Control valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshio Ozawa 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Masahiro Furukawa 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd. (72) Inventor Toshihiro Yamada 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 3L093 AA01 BB11 BB22 BB29 BB31 BB32 CC01 DD09 EE04 EE17 GG00 GG02 JJ02 JJ06 KK05

Claims (8)

[Claims] 1. A low-concentration solution supplied from an absorber (22) flows into a high-temperature regenerator (3) through a low-temperature heat exchanger (5) and a high-temperature heat exchanger (4). While a part of the solution flowing out of the exchanger (5) flows into the low-temperature regenerator (12), the high-concentration solution supplied from the high-temperature regenerator (3) through the high-temperature heat exchanger (4) In a double solution absorption refrigerator of a parallel solution circulation type in which the solution flowing out of the regenerator (12) flows into the absorber (22) through the low-temperature heat exchanger (5),
Adjust the ratio of the flow rate of the solution distributed from the low-temperature heat exchanger (5) to the high-temperature heat exchanger (4) and the flow rate of the solution distributed from the low-temperature heat exchanger (5) to the low-temperature regenerator (12). For adjusting the concentration of the highly concentrated solution flowing out of the low-temperature heat exchanger (5) to the absorber (22) with respect to the crystallization concentration corresponding to the temperature of the solution. A control device for an absorption refrigerator, characterized in that the amount of circulating solution is controlled so as to have a certain crystal margin, and the solution distribution ratio is adjusted according to the refrigeration load. 2. A first calculating means for calculating a crystallization concentration of a high-concentration solution flowing out from a low-temperature heat exchanger (5) toward an absorber (22) based on a temperature of the solution. A second calculating means for calculating a target concentration by adding a predetermined margin to the crystallization concentration; and a deviation of the concentration of the solution flowing out from the low-temperature heat exchanger (5) toward the absorber (22) with respect to the target concentration. Third to calculate
Calculating means, first control means for controlling the amount of solution circulation based on the calculated deviation, and low temperature with respect to the solution flow rate from the low temperature heat exchanger (5) to the high temperature heat exchanger (4) depending on the refrigeration load. The control device for an absorption refrigerator according to claim 1, further comprising second control means for controlling a solution distribution ratio, which is a ratio of a solution flow rate from the heat exchanger (5) to the low temperature regenerator (12). 3. The control device for an absorption refrigerator according to claim 2, wherein when the target concentration is higher than the solution concentration, the solution circulation amount is decreased, and when the target concentration is lower than the solution concentration, the solution circulation amount is increased. . 4. The absorption chiller control apparatus according to claim 3, wherein the solution distribution ratio is set to be large when the refrigeration load is large, and to be small when the refrigeration load is small. 5. The low-concentration solution supplied from the absorber (22) flows into the high-temperature regenerator (3) through the low-temperature heat exchanger (5) and the high-temperature heat exchanger (4). While a part of the solution flowing out of the exchanger (5) flows into the low-temperature regenerator (12), the high-concentration solution supplied from the high-temperature regenerator (3) through the high-temperature heat exchanger (4) In the double-effect absorption refrigerator of the parallel solution circulation type in which the solution flowing out of the regenerator (12) flows into the absorber (22) through the low-temperature heat exchanger (5),
The solution is circulated so that the concentration of the highly concentrated solution flowing out of the low-temperature heat exchanger (5) to the absorber (22) has a certain crystallization margin with respect to the crystallization concentration corresponding to the temperature of the solution. A control device for an absorption refrigerator, wherein the amount is controlled and a crystal margin is changed according to a refrigeration load. 6. A first calculating means for calculating a crystallization concentration of a high-concentration solution flowing out from a low-temperature heat exchanger (5) toward an absorber (22) based on a temperature of the solution, and a refrigeration load. A second calculating means for calculating a crystal margin based on the calculated crystallization concentration and a third calculating means for calculating a target concentration based on the crystal margin; and a low-temperature heat exchanger (5) to the absorber (22). Calculating a deviation of the concentration of the solution flowing toward the target concentration from the fourth concentration.
The control device for an absorption refrigerator according to claim 5, further comprising a calculating means and a control means for controlling a solution circulation amount based on the calculated deviation. 7. The control device for an absorption refrigerator according to claim 6, wherein the circulating amount of the solution is decreased when the target concentration is higher than the solution concentration, and the circulating amount of the solution is increased when the target concentration is lower than the solution concentration. . 8. The control device for an absorption refrigerator according to claim 7, wherein the crystallization margin is set small when the refrigeration load is large, and the crystallization margin is set large when the refrigeration load is small.