JP3306486B2 - Dilution control method for absorption chiller / heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dilution of a dilute solution, and more particularly to a dilution control method for an absorption chiller / heater suitable for preventing crystallization of a dilute solution when cooling operation is stopped.

[0002]

2. Description of the Related Art An example of a conventional absorption chiller / heater will be described with reference to FIG. A high-temperature regenerator 10 having a heating source 12 for heating the dilute solution, a separator 16 disposed above the high-temperature regenerator 10 and connected to the high-temperature regenerator 10 by a rising pipe 14;
A low-temperature regenerator 22 having a refrigerant vapor coil 23 connected at one end to the gas phase portion of the separator 16 is connected to the low-temperature regenerator 22 through a secondary refrigerant vapor pipe 28, and the other end of the refrigerant vapor coil 24 is connected thereto. A condenser 26 having a cooling water coil 50 therein, an evaporator 34 connected to the condenser 26 by a liquid refrigerant pipe 30 having a flow control valve 31 interposed therein, and having an evaporator coil 32 therein, An absorber 44 having a cooling water coil 46 therein in communication with a steam passage, a solution circulation pump 54 having a suction side connected to a bottom of the absorber 44 by a dilute solution suction pipe 52, and a discharge side of the solution circulation pump 54. The high-temperature solution heat exchanger 42, the high-temperature solution heat exchanger 36 connected to the dilute solution inlet of the high-temperature regenerator 10 via the low-temperature solution heat exchanger 42, and the high-temperature solution heat exchange with the liquid phase of the separator 16 Heating fluid in vessel 36 An intermediate concentrated solution pipe 20 for connecting the mouth,
The heating fluid outlet side of the high-temperature solution heat exchanger 36 and the low-temperature regenerator 22
, A concentrated solution pipe 40 connecting the bottom of the low-temperature regenerator 22 and the heating fluid inlet side of the low-temperature solution heat exchanger 42, and a heating fluid outlet side of the low-temperature solution heat exchanger 42. It comprises a concentrated solution pipe 41 connecting the upper part of the absorber 44 and a cooling water pipe 48 connecting the outlet of the cooling water coil 46 and the inlet of the cooling water coil 50. Cooling water coil 5
The outlet side of 0 is connected to a cooling tower (not shown), and the inlet side of the cooling water coil 46 is connected to the cooling tower via a cooling water pump (not shown).

[0003] The operation of the absorption chiller / heater of the above configuration during normal cooling operation will be described. The dilute solution in the high-temperature regenerator 10 is heated by the heating source 12, rises in the riser 14 in a gas-liquid two-phase flow state, and flows into the separator 16. The dilute solution in a gas-liquid two-phase flow state flowing into the separator 16 is separated into a refrigerant vapor and an intermediate concentrated solution, and the refrigerant vapor flows into the condenser 26 via the refrigerant vapor coil 23 provided in the low-temperature regenerator 22. The intermediate concentrated solution flows into the heated fluid side of the high temperature solution heat exchanger 36 via the intermediate concentrated solution pipe 20. The intermediate concentrated solution flowing into the high temperature solution heat exchanger 36 passes through the high temperature solution heat exchanger 36 while heating the dilute solution, flows into the low temperature regenerator 22 through the intermediate concentrated solution pipe 38,
It is sprayed on the refrigerant vapor coil 23. Refrigerant vapor coil 2
The refrigerant vapor flowing inside 3 heats the surrounding intermediate concentrated solution to evaporate the refrigerant to generate a secondary refrigerant vapor, which is itself cooled and condensed to form a gas-liquid two-phase flow into the condenser 26. . The secondary refrigerant vapor generated by the low-temperature regenerator 22 also flows into the condenser 26 through the secondary refrigerant vapor pipe 28, and the refrigerant vapor coil 2
The cooling water flowing through the cooling water coil 50 is condensed with the cooling water flowing through the cooling water coil 50 together with the refrigerant flowing through the cooling water 3 to become a liquid refrigerant.

The liquid refrigerant generated in the condenser 26 flows into the evaporator 34 via the liquid refrigerant pipe 30 and is sprayed on the evaporator coil 32 provided in the evaporator. The refrigerant evaporates by removing heat, becomes refrigerant vapor again, and flows into the absorber 44 via the vaporized refrigerant vapor passage. The heat medium that has been deprived of heat and cooled is guided to a cooling load, performs cooling, and then returns to the evaporating coil 32 again. Low temperature regenerator 2
The intermediate concentrated solution obtained by evaporating the refrigerant as the secondary refrigerant vapor in Step 2 becomes a concentrated solution, and flows into the heated fluid inlet side of the low-temperature solution heat exchanger 42 via the concentrated solution pipe 40. The concentrated solution that has flowed into the low-temperature solution heat exchanger 42 passes through the low-temperature solution heat exchanger 42 while heating the dilute solution, and passes through the concentrated solution pipe 41 to the absorber 44.
Flows into. The concentrated solution that has flowed into the absorber 44 is sprayed on the cooling water coil 46 and absorbs refrigerant vapor flowing from the evaporator 34 to become a dilute solution. The heat of absorption generated when the concentrated solution absorbs the refrigerant vapor is transferred to the cooling water flowing in the cooling water coil 46 and is carried to the cooling tower.

The dilute solution generated by the absorber 44 is sucked into a solution circulation pump 54 via a dilute solution suction pipe 52, pressurized, and flows into the low temperature solution heat exchanger 42 on the side of the fluid to be heated. The dilute solution flowing into the low-temperature solution heat exchanger 42 is heated by the concentrated solution flowing on the heating fluid side while the low-temperature solution heat exchanger 42
And flows into the heated fluid side of the high temperature solution heat exchanger 36. The dilute solution flowing into the high-temperature solution heat exchanger 36 passes through the high-temperature solution heat exchanger 36 while being heated by the intermediate concentrated solution flowing on the heating fluid side, and flows into the high-temperature regenerator 10. The dilute solution flowing into the high-temperature regenerator 10 repeats the above cycle again.

The cooling water from which the heat of absorption is taken out by the cooling water coil 46 and the heat of condensation taken out by the cooling water coil 50 flows into the cooling tower, and releases the carried heat of absorption and heat of condensation to the atmosphere. During normal operation, the above-described cycle is repeated.

Next, the case where the cooling load is reduced and the cooling operation is stopped will be described. When the cooling operation of the absorption chiller / heater is stopped, the solution circulation pump 54 is operated intermittently, and the high-temperature regenerator 10, the low-temperature regenerator 22, the high-temperature solution heat exchanger 36, and the low-temperature solution heat exchanger 42 having a high solution concentration are used. (See JP-A-1-123960).
As shown in FIG. 7, in the dilution operation, constant dilution control is performed by performing an intermittent operation for a predetermined operation time t, for example, about 30 minutes. Depending on the amount of heat, the solution concentration during operation varies,
The concentration of the solution to be crystallized also varies depending on the outside air temperature when the operation is stopped. Therefore, it is necessary to change to the required dilution operation time.However, in the dilution operation with predetermined control, crystallization occurs due to insufficient decrease in the solution concentration, or the dilution operation is performed more than necessary, and the cavitation of the solution circulation pump is performed. Alternatively, power consumption is likely to increase.

[0008]

In the conventional dilution control method of the absorption chiller / heater, a constant dilution control is performed for a predetermined operation time. The concentration of the solution during operation varies depending on the amount of heat input to the regenerator, and the concentration of the solution to be crystallized also varies depending on the outside air temperature when the operation is stopped. Therefore, if the required dilution operation time is not changed, there is a problem that crystallization occurs due to insufficient decrease of the solution concentration, cavitation of the solution circulation pump or an increase in power consumption due to an excessive dilution operation is liable to occur.

An object of the present invention is to provide a dilution control method for an absorption chiller / heater which can appropriately correct a dilution operation time of a solution circulation pump for diluting a dilute solution when cooling operation is stopped.

[0010]

In order to achieve the above object, a method for controlling dilution of an absorption chiller / heater according to the present invention comprises a high-temperature regenerator, a low-temperature regenerator, a high-temperature solution heat exchanger, and a low-temperature solution heat exchanger. The condenser, the evaporator, the absorber and the solution circulation pump are connected, and when the cooling operation is stopped, the solution circulation pump is operated intermittently for a predetermined dilution time, and the solution circulation pump passes through each solution heat exchanger and the high temperature regenerator. In the dilution control method of the absorption chiller-heater that dilutes the diluted solution fed to, at least the preset values of the temperature and the dilution time are stored in advance, and at least the measured value of the temperature is input immediately before the cooling operation is stopped, and the dilution time is It is configured to correct according to each measurement value.

[0011] The measured values are the heat input of the high-temperature regenerator and
It consists of the cooling water temperature of the absorber and the outside air temperature, and the dilution time is corrected by the ratio of the measured value of the heat input and the cooling water temperature to the set value, and when the measured value of the outside air temperature is less than the set value. Alternatively, a configuration may be used in which correction is made based on the deviation.

The measured value is composed of the pressure and temperature of the high-temperature regenerator and the cooling water temperature of the absorber. The solution concentration at the outlet of the high-temperature regenerator is calculated based on the pressure and temperature of the high-temperature regenerator. The correction value may be added based on the ratio between the calculated solution concentration and the set value, and the correction value may be added when the cooling water temperature is 20 ° C. or less.

Further, in the absorption chiller / heater, the dilution control method of any one of the absorption chiller / heater is used.

[0014]

1 and 2 show an embodiment of the present invention.
This will be described with reference to FIG. As shown in FIGS. 1 and 2,
The dilute solution is heated by the heating source 12 in the high-temperature regenerator 10 and separated into refrigerant vapor and an intermediate concentrated solution.
The intermediate concentrated solution sent to the low temperature regenerator 22 through the above is reheated by the refrigerant vapor to generate a concentrated solution, and the concentrated solution is supplied to the absorber 44 via the low temperature solution heat exchanger 42 to condense the refrigerant vapor. The refrigerant is condensed into a liquid refrigerant in the evaporator 26, the liquid refrigerant is evaporated in the evaporator 34, and the evaporated refrigerant is absorbed into a concentrated solution by the absorber 44 to generate a dilute solution. High temperature regenerator 1 via solution heat exchangers 42 and 36
0, and when the cooling operation is stopped, the solution circulation pump 54 is intermittently operated according to the dilution time t to control the dilution of the dilute solution. The set value is stored in the controller 1 in advance, and at least a measured value of the temperature is input to the controller 1 immediately before the cooling operation is stopped, and the dilution time t is corrected according to each measured value. The solution circulation pump 54 is configured to operate intermittently.

The measured values are the heat input I of the heating source 12 of the high-temperature regenerator 10, the cooling water temperature Tc at the inlet of the absorber 44 measured by the temperature sensor 2, and the outside air temperature measured by the temperature sensor 3. To and dilution time t
Is corrected by the controller 1 to the dilution time to by the ratio of the measured values I and Tc of the heat input amount and the cooling water temperature to the set values Is and Tcs of the heat input amount and the cooling water temperature stored in the controller 1 in advance. At the same time, the dilution time to is corrected to the dilution time ta by the deviation when the measured value To of the outside air temperature is equal to or less than the set value Tos.

That is, the cooling operation is stopped (procedure 101).
And the measured values of the heat input amount I, the cooling water temperature Tc, and the outside air temperature To of the high temperature regenerator 16 immediately before the stop are input to the controller 1 (procedure 102). The dilution time to is calculated by (step 103), and to = t × (I / Is) × (Tc / Tcs) (1) Here, the measured value To of the outside air temperature is compared with the set value Tos, and To < When Tos (procedure 104) is NO, ta = to is set (procedure 105), and To <Tos (procedure 104) is Y.
In the case of ES, the dilution time ta is calculated by equation (2) (step 106). ta = to × (Tos−To) (2) The solution circulation pump starts the intermittent operation at the dilution time ta, and the start point is point A shown in FIG.

Next, the operation of this embodiment will be described. First, when the cooling operation stop signal is output, the temperatures Tc and To and the heat input I immediately before the cooling stop are input to the dilution program.
Here, when the heat input amount I is smaller than the set value Is and when the cooling water temperature Tc is lower than the set value Tcs, the intermittent operation time ta of the solution circulation pump is shortened by the deviation.
Conversely, when the heat input amount I is larger than the set value Is and when the cooling water temperature Tc is higher than the set value Tcs, the intermittent operation time ta of the solution circulation pump is extended due to the deviation. Further, a correction based on the deviation of the outside air temperature is added.

Hereinafter, a specific example will be described. The set value of the heat input is 50% of the rating, and the set value of the cooling water temperature is 27 ° C.
Here, the measured value at the time of cooling stop is 30% heat input, and when the cooling water temperature is 24 ° C, the solution concentration is small because the heat input is small.
It is determined that the concentration is small and the dilution operation time can be short.
In addition, since the dilution effect of the entire system is performed due to the low cooling water temperature, the concentration of the solution is reduced, and it is determined that the dilution operation time may be short. Therefore, when the operation time of the solution circulation pump is calculated from the deviation between each measured value and each set value, the operation is performed with a dilution time of about 60% (30/50 × 24/27) of the set value. Further, the outside air temperature To when the cooling is stopped is detected, and when the temperature is lower than the set value (here, 20 ° C.), the correction time (correction value) is added to the above-mentioned operation time to reliably prevent crystallization at the stop. Control. When the heat input during shutdown is 70% and the cooling water temperature is 30 ° C,
Since the solution concentration has a large amount of heat input, the concentration is advanced and the concentration is higher than the set concentration, so that it is determined that the dilution operation time is required to be long. Also, since the cooling water temperature is higher than the set value,
Since the solution concentration of the entire system has also shifted to the higher concentration side, it is determined that a longer dilution operation time is required. Therefore, the dilution operation time needs to be as long as about 150% of the set time. The outside air temperature correction is the same as described above. In addition, it is necessary to determine the optimal values for the set value of the dilution operation time of the solution circulation pump and the set values of the heat input amount, the cooling water temperature, and the outside air temperature depending on each model.

According to this embodiment, the dilution time of the solution concentration when the cooling operation is stopped is set to an optimum operation time according to the operation state when the cooling operation is stopped and the outside air temperature, and the crystallization at the low outside air temperature is prevented. By reducing the dilution time at low cooling water temperature or low heat input, it is possible to reduce power consumption of the solution circulation pump and prevent cavitation due to excessive feeding of the dilute solution.

Another embodiment of the present invention will be described with reference to FIGS. The difference from the embodiment shown in FIG. 1 is that the measured value is composed of the pressure P of the high-temperature regenerator 10, the temperature T of the high-temperature regenerator 10, and the cooling water temperature Tc of the absorber 46. The solution concentration N at the outlet of the high-temperature regenerator 10 is calculated from the pressure P and the temperature T, and the dilution time t is corrected to the dilution time t ₁ by the ratio between the calculated solution concentration N and the set value No. When the cooling water temperature Tc of the absorber 46 is equal to or lower than 20 ° C., a correction value is added to the dilution time t ₁ and corrected to the dilution time tb.

That is, the cooling operation is stopped (procedure 201).
And the measured value of the cooling water temperature Tc as a substitute for the pressure P, the temperature T and the outside air temperature of the high-temperature regenerator 10 immediately before the stop of the cooling operation, is input to the controller 1 (procedure 202), and the solution concentration N at the outlet of the high-temperature regenerator 10 The solution concentration N is calculated by an arithmetic unit (not shown) of the controller 1 by Expression (3) which is an approximate expression (Step 20).
3), N = f × (P, T) (3) The dilution time t ₁ is calculated by the ratio between the solution concentration N and its set value No shown in the equation (4) (procedure) 204), t ₁ = t × N / No (4) ￥ Here, the cooling water temperature Tc is set to 2 as the outside air temperature correction.
It is compared with 0 ° C. or less (step 205), and if it is not 20 ° C. or less and NO, the dilution time tb = t ₁ is set (step 20).
6) If the temperature is 20 ° C. or less and YES, the dilution time t
For b, the correction value is added by equation (5) (procedure 20).
7). tb = t ₁ + correction value... (5) The solution circulation pump starts intermittent operation at the dilution time tb, and this start point is point A shown in FIG.

Next, the operation of this embodiment will be described. First, when the cooling operation stop signal is output, the pressure P and the temperature T of the high temperature regenerator immediately before the stop of the cooling are input to the concentration calculation program. Here, the current concentration N is obtained by the concentration approximate expression (3) obtained from the pressure P and the temperature T, and the set concentration N is obtained.
The dilution time t ₁ is calculated from the deviation N / No from o. Further, when the outside air temperature is lower than the set temperature, the correction value is added to the dilution time t ₁ to obtain the final dilution time tb. Specifically, if the cooling water coil is contaminated and the high-temperature regenerator pressure is higher than the set pressure of 650 mmHg by a numerical value.
0mmHg pressure rises and temperature is set to 150 ℃
When the cooling operation is stopped in a state where the temperature rises by about 5 ° C., the solution concentration at the outlet of the regenerator, which is higher than the pressure and the temperature, is obtained by an approximate expression and becomes about 58%. This is about 1 for 57% of the set concentration.
%, And the time needs to be longer than in a normal dilution operation. Here, the dilution operation time t ₁ is determined from the concentration deviation from the set concentration by the set program. Further, if the set cooling water temperature is set to 20 ° C. and the cooling water inlet temperature at the time of stop is 20 ° C. or less, it is considered that the cooling water stops at a temperature lower than the set outside air temperature. The dilution time (t ₁ + correction value) is obtained by adding the proportional correction value. In addition, it is necessary to determine optimal values for the set value of the operation time of the solution circulation pump and the set values of the pressure, temperature and cooling water temperature of the high-temperature regenerator depending on the model.

According to the present embodiment, it is possible to cope with the existing pressure sensor and temperature sensor, and it is possible to cope without increasing the cost because a newly added sensor is unnecessary. Further, the solution concentration can be accurately measured by the pressure and the temperature, and the correction by the cooling water temperature is added, so that the response to the crystallization prevention due to the decrease in the outside air temperature is improved. In addition, density measurement can be performed without using an expensive densitometer. It is possible to prevent crystallization of the solution when the operation of the high temperature regenerator is stopped at elevated pressure and temperature due to contamination of the cooling water, and when the outside air temperature decreases due to winter cooling. Can be provided.

[0024]

According to the present invention, since the dilution time of the dilute solution at the time of stopping the cooling operation is corrected to the optimum operation time according to the operation state at the time of stopping the cooling and the outside air temperature, the crystallization at the time of the low outside air temperature is performed. In addition, by reducing the dilution time at low cooling water temperature or low heat input, it is possible to reduce power consumption of the solution circulation pump and prevent cavitation due to excessive feeding of the dilute solution. Further, there is an effect that crystallization of the solution can be prevented when the operation of the high-temperature regenerator is stopped in a state in which the pressure and the temperature are increased due to contamination of the cooling water or the like, and when the outside air temperature is decreased due to the cooling in winter.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart of the embodiment shown in FIG.

FIG. 3 is a diagram illustrating the operation of the present embodiment.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a flowchart of the embodiment shown in FIG.

FIG. 6 is a diagram showing a conventional technique.

FIG. 7 is a diagram illustrating the operation of the conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Controller 2 Temperature sensor 3 Temperature sensor 4 Pressure sensor 5 Temperature sensor 10 High temperature regenerator 11 Temperature detector 12 Heat source 14 Rise pipe 16 Separator 18 Refrigerant vapor pipe 20 Intermediate concentrated solution pipe 22 Low temperature regenerator 23 Refrigerant vapor coil 24 Condensed refrigerant vapor tube 26 Condenser 28 Secondary refrigerant vapor tube 30 Liquid refrigerant tube 31 Flow control valve 32 Evaporation coil 34 Evaporator 36 High temperature solution heat exchanger 38 Intermediate concentrated solution tube 40 Concentrated solution tube 41 Concentrated solution tube 42 Low temperature solution heat Exchanger 44 Absorber 46 Cooling water coil 48 Cooling water pipe 50 Cooling water coil 52 Dilute solution suction pipe 54 Solution circulation pump

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-101765 (JP, A) JP-A-7-190537 (JP, A) JP-A-1-123960 (JP, A) JP-A 57-107 202465 (JP, A) JP-A-2-213659 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 15/00 306

Claims (3)

(57) [Claims] 1. A high-temperature regenerator, a low-temperature regenerator, a high-temperature solution heat exchanger, a low-temperature solution heat exchanger, a condenser, an evaporator, an absorber and a solution circulation pump are connected. Is operated intermittently for a predetermined dilution time, and the solution circulation pump dilutes the dilute solution fed to the high-temperature regenerator through the respective solution heat exchangers. prestores time settings, enter the measurement values of temperatures including at least the outside air temperature just before the cooling operation stops, the dilution time, and be corrected in accordance with the respective measured values, the measured value is high
Heat regenerator heat input, absorber cooling water temperature, and outside air temperature
And the dilution time is determined by the heat input and the cooling water temperature.
While being corrected by the ratio of the measured value of the degree and the set value,
When the measured value of the outside air temperature is equal to or less than the set value,
Ri corrected dilution control method of the absorption chiller, characterized in that the. 2. A high-temperature regenerator, a low-temperature regenerator, a high-temperature solution heat exchanger, a low-temperature solution heat exchanger, a condenser, an evaporator, an absorber, and a solution circulation pump are connected. Is operated intermittently for a predetermined dilution time, and the solution circulation pump dilutes the dilute solution fed to the high-temperature regenerator through the respective solution heat exchangers. The set value of the time is stored in advance, at least the measured value of the temperature is input immediately before the cooling operation is stopped, and the dilution time is corrected according to each measured value, and the measured value is the pressure of the high-temperature regenerator. And the temperature, and the cooling water temperature of the absorber. The solution concentration at the outlet of the high-temperature regenerator is calculated based on the pressure and temperature of the high-temperature regenerator, and the dilution time is the ratio of the calculated solution concentration to the set value. Corrected by Together are, the cooling water temperature is 2
A dilution control method for an absorption chiller / heater, wherein a correction value is added when the temperature is 0 ° C. or lower. 3. An absorption chiller / heater using the dilution control method for an absorption chiller / heater according to claim 1 or 2 .