JP5091590B2 - Absorption type water heater - Google Patents

Description

  The present invention relates to an absorption chiller / heater, and more particularly, to an absorption chiller / heater equipped with a liquid refrigerant proportional valve that controls the flow rate of liquid refrigerant sent from a condenser to an evaporator.

  An absorption chiller / heater forms an absorption refrigeration cycle by connecting a regenerator, a condenser, an evaporator, an absorber, and the like. For example, the liquid refrigerant and the load fluid are exchanged in the evaporator to exchange the liquid refrigerant. The load fluid is cooled by latent heat of vaporization.

  In such an absorption chiller / heater, as described in Patent Document 1, in the cooling mode, a liquid refrigerant proportional valve is provided in the refrigerant flow path between the condenser and the evaporator, and the detected temperature of the evaporator It is known to control the valve opening of the liquid refrigerant proportional valve according to the above. This is to control the amount of refrigerant in the liquid refrigerant storage chamber by adjusting the flow rate of refrigerant to the evaporator by controlling the valve opening, thereby controlling the solution concentration and the absorption capacity in the absorber due to this. It is.

  For example, if the temperature of the absorber decreases due to a decrease in the temperature of the cooling water that exchanges heat with the solution in the absorber and the absorption power increases, thereby reducing the pressure and temperature of the evaporator, In order to suppress freezing or the like, the liquid refrigerant flow rate is increased by increasing the valve opening of the liquid refrigerant proportional valve in accordance with a decrease in the evaporator temperature. Then, since the solution concentration is lowered by reducing the amount of refrigerant in the liquid refrigerant storage chamber, the absorption capacity of the absorber is reduced, the evaporator temperature is increased, and the predetermined evaporator temperature is reached.

  On the other hand, for example, when the temperature of the evaporator rises due to an increase in the temperature of the cooling water, in order to maintain the cooling capacity, the liquid refrigerant flow rate is reduced by reducing the liquid refrigerant flow rate by reducing the liquid refrigerant proportional valve opening. Increase the amount of refrigerant in the chamber. As a result, the solution concentration increases, the absorption capacity of the absorber increases, and the evaporator temperature decreases.

JP-A-8-247469

  However, the technique described in Patent Document 1 leaves room for further improvement in stabilizing the cooling capacity.

  That is, the temperature of the cooling water is different between, for example, summer and intermediate periods such as spring and autumn, and if the cooling water temperature is different, the absorption capacity of the absorber is also different. Thus, even if the target temperature of the evaporator is the same, the appropriate valve opening is different.

  On the other hand, the technique of Patent Document 1 captures the absorption power of the absorber only by the evaporator temperature, and sets the valve opening corresponding to the detected evaporator temperature to the preset evaporator temperature and valve opening. Control is based on the correlation with. However, in order to ensure the cooling capacity when the cooling water temperature is high and to perform appropriate control so that the refrigerant does not freeze when the cooling water temperature is low, the change in the valve opening relative to the evaporator temperature change (control (Sensitivity) increases, and the liquid refrigerant proportional valve opening greatly changes due to a change in the evaporator temperature, resulting in poor stability. As a result, the cooling capacity may not be stable.

  Then, this invention makes it a subject to improve the stability of the cooling capability of an absorption-type cold / hot water machine.

  In order to solve the above problems, an absorption chiller / heater of the present invention includes a regenerator that heats a dilute solution to generate refrigerant vapor and a concentrated solution, and a condenser that condenses the refrigerant vapor generated by the regenerator. And an evaporator that cools the load fluid by exchanging heat between the refrigerant liquid condensed in the condenser and the load fluid, and the refrigerant evaporated in the evaporator is absorbed by the concentrated solution generated in the regenerator. An absorption refrigeration cycle is formed by connecting an absorber that generates a solution and a solution circulation pump that sends a dilute solution generated by the absorber to a regenerator. In addition, a liquid refrigerant proportional valve that is provided in the refrigerant flow path connecting the condenser and the evaporator and adjusts the refrigerant flow rate, detects the temperature of the evaporator, and sets the valve opening corresponding to the detected temperature to the evaporator temperature in advance. Control means for controlling the valve opening degree of the liquid refrigerant proportional valve based on the correlation in which the valve opening degree is set in correspondence.

  The correlation in which the valve opening is set in association with the evaporator temperature is set in correlation with the temperature of the cooling water that exchanges heat with the concentrated solution in the absorber. The valve opening degree of the liquid refrigerant proportional valve is controlled based on the correlation according to the detected temperature of the cooling water.

  That is, in the present invention, the valve opening degree of the liquid refrigerant proportional valve is controlled in consideration of not only the temperature of the evaporator but also the temperature of the cooling water that exchanges heat with the concentrated solution of the absorber. In other words, the correlation between the evaporator temperature and the valve opening is set in correlation with the temperature of the coolant that exchanges heat with the concentrated solution of the absorber, and the valve opening with respect to the temperature change of the evaporator. The degree of change (control sensitivity) is appropriately set. Therefore, by controlling based on the detected temperature of the evaporator and the correlation between the appropriate evaporator temperature corresponding to the detected temperature of the cooling water and the valve opening, the liquid refrigerant proportional valve It can suppress that the opening degree changes greatly and the stability deteriorates, and as a result, the stability of the cooling capacity can be improved.

In this case, the correlation between the evaporator temperature and the valve opening is that the evaporator temperature is the set temperature (t ₁ ) Below, the valve opening is set to a preset maximum value, and the set temperature (t ₁ ) In the above, the valve opening is set to a correlation that decreases as the evaporator temperature increases from the maximum value, and when the coolant temperature is high in correlation with the coolant temperature that exchanges heat with the concentrated solution of the absorber The maximum value is set small, and the maximum value is set large when the cooling water temperature is low.

  That is, for example, the higher the temperature of the cooling water in summer, the lower the cooling capacity of the concentrated solution and the higher the solution concentration, so the valve opening is set smaller. In addition to this, the change in the evaporator pressure when the cooling water temperature is changed is, for example, about 5 to 7 mmHg, whereas the change in the condenser pressure is, for example, about 35 to 55 mmHg, and the temperature of the cooling water is increased. As the differential pressure between the condenser and the evaporator increases, the valve opening is set small.

  In addition, the correlation in which the valve opening is set in correspondence with the evaporator temperature has a slope where the valve opening decreases with a constant slope as the evaporator temperature increases, and is correlated with the coolant temperature. The correlation thus set is desirably set so that the inclination becomes smaller as the temperature of the cooling water becomes lower.

  The capacity of the absorber increases as the temperature of the cooling water decreases. Since the capacity of the absorber is high and the differential pressure between the condenser and the evaporator is small, if the sensitivity of the change in the valve opening relative to the temperature change of the evaporator is high, it will follow a sudden change in the valve opening. Since the evaporator temperature changes greatly, the stability is poor, and as a result, the cooling capacity is not stable. Therefore, as the cooling water temperature decreases, the gradient in the correlation between the evaporator temperature and the valve opening becomes smaller, that is, the sensitivity is lowered, so that the rapid change in the valve opening and the rapid temperature change in the evaporator. Can be suppressed to stabilize the cooling capacity.

  Moreover, in order to solve the said subject, the other aspect of the absorption chiller-heater of this invention forms the absorption refrigeration cycle similar to the above-mentioned aspect, and the refrigerant | coolant flow path which connects a condenser and an evaporator A liquid refrigerant proportional valve for adjusting the refrigerant flow rate, and a control means for controlling the valve opening degree of the liquid refrigerant proportional valve. The control means detects the temperature of the evaporator and the temperature of the cooling water that exchanges heat with the concentrated solution of the absorber, and determines the valve opening degree of the liquid refrigerant proportional valve based on the detected evaporator temperature and cooling water temperature. It is characterized by controlling.

  According to the present invention, the stability of the cooling capacity of the absorption chiller / heater can be improved.

  Hereinafter, an embodiment of an absorption chiller / heater to which the present invention is applied will be described. In addition, although this embodiment demonstrates as what is called a double effect absorption chiller / heater as an example, this invention is not limited to this, It is also possible to apply to a single effect or a triple effect absorption chiller / heater. is there.

  FIG. 1 is a diagram illustrating an overall configuration of an absorption chiller / heater according to the present embodiment. The absorption chiller / heater 10 includes a high temperature regenerator 12, a separator 14, a low temperature regenerator 16, a condenser 18, an evaporator 20, an absorber 22, a solution circulation pump 24, a high temperature and a low temperature solution. The heat exchangers 26, 28 and the like are connected by piping to form an absorption refrigeration cycle.

  In the cooling operation mode, the high-temperature regenerator 12 heats a dilute solution composed of, for example, water as a refrigerant and lithium bromide (LiBr) as an absorbent by a heat source supplied from the outside, and the separator 14 is heated. The dilute solution is separated into refrigerant vapor and intermediate concentrated solution. The high temperature solution heat exchanger 26 cools the separated intermediate concentrated solution by heat exchange with the diluted solution sent by the solution circulation pump 24, and the low temperature regenerator 16 separates the cooled intermediate concentrated solution by the separator 14. The refrigerant vapor is heated again to generate refrigerant vapor to produce a concentrated solution. The low temperature solution heat exchanger 28 lowers the temperature by exchanging heat of this concentrated solution with the dilute solution sent by the solution circulation pump 24.

  Refrigerant vapor generated by heating the intermediate concentrated solution again in the low temperature regenerator 16 and refrigerant vapor lowered in temperature by exchanging heat with the intermediate concentrated solution in the low temperature regenerator 16 flow into the condenser 18. Further, the condenser 18 is supplied with cooling water after passing through an absorber 22 described later, whereby the refrigerant vapor is condensed, and the condensed liquid refrigerant is a liquid provided in the condenser 18. The refrigerant is stored in the refrigerant storage chamber 30. The evaporator 20 is provided with a liquid refrigerant distributor 32 and a temperature sensor 33, and the liquid refrigerant that has flowed in from the condenser 18 is dropped from the liquid refrigerant distributor 32 and sprayed onto the evaporator heat transfer tube. Thereby, the liquid refrigerant evaporates by taking heat from the load fluid such as water to be cooled flowing in the evaporator heat transfer tube, and the load fluid is cooled by the latent heat of evaporation.

  The absorber 22 is produced by the low-temperature regenerator 16 and then dripped while the concentrated solution heat-exchanged by the low-temperature solution heat exchanger 28 is cooled with the cooling water supplied to the absorber 22, thereby evaporating the evaporator 20. The refrigerant evaporated in step 1 is absorbed to form a dilute solution. The solution circulation pump 24 sends the dilute solution generated by the absorber 22 to the high temperature regenerator 12 through the low temperature solution heat exchanger 28 and the high temperature solution heat exchanger 26. In addition, the temperature sensor 35 detects the inlet temperature of the cooling water flowing through the absorber 22.

  Further, the liquid refrigerant storage chamber 30 and the liquid refrigerant distributor 32 are connected via refrigerant flow paths 34 and 36, and the refrigerant flow path 36 is provided with a liquid refrigerant proportional valve 38 for adjusting the refrigerant flow rate. Yes. Furthermore, a control means 40 for controlling the valve opening degree of the liquid refrigerant proportional valve 38 while detecting the temperature of the evaporator 20 and the temperature of the cooling water inlet is provided. The valve opening degree of the liquid refrigerant proportional valve 38 is controlled according to a command from the control means 40, and thereby the liquid level height H of the liquid refrigerant in the liquid refrigerant storage chamber 30 is controlled. The control means 40 calculates the valve opening based on the evaporator temperature and the cooling water inlet temperature.

  Next, a specific configuration of the liquid refrigerant proportional valve 38 will be described with reference to FIG. As shown in FIG. 2, the liquid refrigerant proportional valve (proportional valve) 38 includes an annular coil 42, a hollow cylindrical rotor 44 that is accommodated in the coil 42 and can be moved up and down, and a lower end of the rotor 44. An annular female screw 46 fixed to the inner screw 46, a hollow cylindrical male screw 48 meshing with the female screw 46, a valve rod 50 fixed to the upper end of the rotor 44 and inserted through the male screw 48, and fixed to the lower end of the valve rod 50. A valve 52, a nozzle 54 opened and closed by the vertical movement of the valve 52, a fluid inlet 56 provided below the nozzle 54 and connected to the liquid refrigerant storage chamber, and a liquid refrigerant distributor provided above the nozzle 54 Formed by a fluid outlet 58 or the like connected to the.

  When a pulse current corresponding to a command from the control means 40 is applied to the coil 42, the rotor 44 rotates and is guided by the male screw 48 to move up and down, so that the valve 52 opens and closes the nozzle 54. For example, the valve 52 is formed such that the apex of the conical shape is positioned on the lower side, and the flow area between the valve 52 and the nozzle 54 is linearly proportional to the amount of vertical movement thereof. The liquid refrigerant flow rate is controlled in proportion to the liquid level, and the liquid level height H is controlled. However, the configuration of the liquid refrigerant proportional valve (proportional valve) 38 is not limited to this, and various known proportional valves can be employed.

  Next, the control means 40 which is a characteristic part of the absorption chiller / heater of this embodiment will be described. First, conventional basic control of the valve opening degree of the control means 40 will be described with reference to FIG. In this figure, the horizontal axis represents the evaporator temperature, and the vertical axis represents the valve opening of the liquid refrigerant proportional valve. As shown in the figure, in the prior art, the valve opening is controlled in proportion to the evaporator temperature. That is, the correlation between the evaporator temperature and the valve opening is determined in advance, and if the detected evaporator temperature becomes lower than the set target temperature of the evaporator 20, the valve opening is increased. By increasing the liquid refrigerant flow rate, the liquid level height H in the liquid refrigerant storage chamber 30 is lowered to lower the solution concentration and reduce the absorption capacity of the absorber, thereby raising the evaporator temperature.

  On the other hand, if the detected evaporator temperature is higher than the target temperature, the liquid level height H in the liquid refrigerant storage chamber 30 is increased by reducing the valve opening and lowering the liquid refrigerant flow rate. This increases the absorption capacity of the absorber and lowers the evaporator temperature. In this way, the evaporator temperature is controlled so as to always reach the target temperature.

  However, in such liquid refrigerant proportional valve opening control, the change in valve opening (control sensitivity) with respect to the temperature change of the evaporator increases, and the liquid refrigerant proportional valve opening greatly changes due to the change in evaporator temperature. The stability may be poor, and as a result, the cooling capacity may not be stable.

  In other words, the temperature of the cooling water is different between the summer season and the intermediate period such as spring or autumn, and the absorption capacity of the absorber is different if the cooling water temperature is different. Thus, even if the target temperature of the evaporator is the same, the appropriate valve opening is different. Further, the change in the evaporator pressure when the cooling water temperature changes is, for example, about 5 to 7 mmHg, whereas the change in the condenser pressure is, for example, about 35 to 55 mmHg. -The pressure difference between the evaporators varies greatly.

  When the cooling water temperature is high, the differential pressure is large and the refrigerant flows easily. In order to maintain the cooling capacity, it is necessary to make the liquid refrigerant proportional valve opening smaller, and the evaporator temperature becomes high and stable. On the other hand, when the cooling water temperature is low, the differential pressure is small and the refrigerant hardly flows. Therefore, in order to prevent the refrigerant from freezing, it is necessary to increase the liquid refrigerant proportional valve opening, and the evaporator temperature is low and stable.

And since the difference in the stable temperature of the evaporator when the cooling water temperature is high and low is narrow, in order to ensure the cooling capacity when the cooling water temperature is high and not cause refrigerant freezing when the cooling water temperature is low, It is necessary to narrow the evaporator temperature range (between t ₁ and t _{2 in} FIG. 3) corresponding to the valve opening degree of 0 to 100%. Then, since the control sensitivity (slope) of the valve opening with respect to the temperature change of the evaporator becomes large, the liquid refrigerant proportional valve opening greatly changes with the change of the evaporator temperature and the stability is deteriorated. As a result, the cooling capacity is stabilized. do not do. The aspect of the control means 40 of this embodiment based on such a problem is demonstrated below.

  As shown in FIG. 4, the control means 40 includes an input I / F (input interface) 60 for inputting the cooling water temperature Ts for exchanging heat with the concentrated solution in the absorber 22 and the evaporator temperature T, and an input I / F 60. A central processing unit 64 that calculates the valve opening degree of the liquid refrigerant proportional valve 38 based on the coolant temperature Ts and the evaporator temperature T that are input from the output, and an output I / F (output interface) that outputs the calculated valve opening degree ) 66 and the like. The central processing unit 64 calculates the valve opening according to the cooling water temperature Ts and the evaporator temperature T by executing an arithmetic expression by a software program stored in a storage means (not shown).

  Instead of executing the arithmetic expression, a table of the valve opening degree corresponding to the cooling water temperature Ts and the evaporator temperature T is stored in the storage means in advance, and the input cooling water temperature Ts and the evaporator temperature are stored. The corresponding valve opening may be read from T. When a value between the set values in the valve opening table is detected, it may be configured to appropriately interpolate.

  That is, the control means 40 controls the valve opening degree of the liquid refrigerant proportional valve based on the evaporator temperature and the cooling water that exchanges heat with the concentrated solution in the absorber. Specifically, as shown in FIG. 5, the correlation between the evaporator temperature and the valve opening is set in correlation with the cooling water temperature Ts. FIG. 5 is a diagram showing a correlation between the evaporator temperature and the valve opening degree as a representative example when the cooling water temperature is high and low for convenience of explanation.

  Thus, the correlation set in correlation with the temperature of the cooling water is set so that the valve opening degree associated with the evaporator temperature decreases as the temperature of the cooling water increases. That is, for example, when the coolant temperature is high, the maximum value of the liquid refrigerant proportional valve opening is set to 50% as shown in FIG. This is because, for example, the higher the temperature of the cooling water in summer, the lower the cooling capacity of the concentrated solution and the higher the solution concentration. In addition to this, the change in the evaporator pressure when the cooling water temperature is changed is, for example, about 5 to 7 mmHg, whereas the change in the condenser pressure is, for example, about 35 to 55 mmHg. As the pressure increases, the differential pressure between the condenser and the evaporator increases, so the valve opening is set small.

Furthermore, the evaporator correlation between the temperature and the valve opening is between t ₁ ~t ₂ slope portion (FIG. 5 where the valve opening degree at a constant gradient as the temperature of the evaporator is high is reduced, and t ₁ ~ Although those having a t between _3), as shown in FIG. 5, the gradient when the temperature of the cooling water is low, the temperature of the cooling water is set to be smaller than in the case high. This is because the cooling capacity of the concentrated solution increases as the temperature of the cooling water decreases, so that the absorption capacity increases and sufficient cooling capacity of the evaporator is obtained. In this case, the valve opening degree with respect to the temperature change of the evaporator is increased. If the sensitivity of the change is high, the valve opening degree changes abruptly and the evaporator temperature also changes greatly, so the stability is poor, and as a result, the cooling capacity is not stable.

  Therefore, as the cooling water temperature decreases, the gradient in the correlation between the evaporator temperature and the valve opening becomes smaller, that is, the sensitivity is lowered, so that the rapid change in the valve opening and the rapid temperature change in the evaporator. Can be suppressed to stabilize the cooling capacity.

  Next, the control flowchart of the control means 40 is demonstrated using FIG. When the cooling water inlet temperature Ts is detected (S1), the correlation between the evaporator temperature and the valve opening is obtained based on this (S2). Subsequently, the temperature of the evaporator 20 is detected (S3), and based on this temperature and the correlation between the evaporator temperature calculated in S2 and the valve opening, the valve opening is controlled by the valve opening proportional control. Calculated (S4). The valve opening command signal calculated in S4 is output to the liquid refrigerant proportional valve 38 (S5), and the liquid refrigerant proportional valve 38 controls the refrigerant flow rate based on this command signal.

  As described above, according to the present embodiment, the correlation between the evaporator temperature and the valve opening is set in correlation with the temperature of the cooling water that exchanges heat with the concentrated solution of the absorber. An appropriate correlation between the evaporator temperature corresponding to the detected temperature of the cooling water and the valve opening can be used. In this correlation, the change in the valve opening (control sensitivity) with respect to the change in the evaporator temperature is set appropriately, so that the liquid refrigerant proportional valve opening changes greatly with the change in the evaporator temperature and is stable. As a result, the stability of the cooling capacity can be improved.

It is a figure which shows the whole structure of the absorption-type cold / hot water machine of this embodiment. It is a figure which shows the structure of a liquid refrigerant proportional valve. It is a figure explaining the control content of the conventional valve opening degree of a control means. It is a figure which shows the structure of a control means. It is a figure which shows the correlation with the evaporator temperature and valve opening degree when a cooling water temperature is high and low. It is a control flowchart of the valve opening degree of a control means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Absorption type cold / hot water machine 12 High temperature regenerator 14 Separator 16 Low temperature regenerator 18 Condenser 20 Evaporator 22 Absorber 24 Solution circulation pump 26 High temperature solution heat exchanger 28 Low temperature solution heat exchanger 30 Liquid refrigerant storage chamber 32 Liquid refrigerant Distributors 33 and 35 Temperature sensors 34 and 36 Refrigerant flow path 38 Liquid refrigerant proportional valve 40 Control means

Claims (3)

A regenerator that heats a dilute solution to generate refrigerant vapor and a concentrated solution, a condenser that condenses the refrigerant vapor generated in the regenerator, and a refrigerant liquid and a load fluid condensed in the condenser are heated. The evaporator that exchanges and cools the load fluid, the absorber that absorbs the refrigerant evaporated in the evaporator into the concentrated solution generated in the regenerator and generates the dilute solution, and the absorber that is generated in the absorber A liquid refrigerant proportional valve that is connected to a solution circulation pump that sends a dilute solution to the regenerator to form an absorption refrigeration cycle, and that is provided in a refrigerant flow path that connects the condenser and the evaporator; The temperature of the evaporator is detected, and the valve opening degree of the liquid refrigerant proportional valve is determined based on a correlation in which the valve opening degree is set in advance by associating the valve opening degree corresponding to the detected temperature with the evaporator temperature. An absorption chiller / heater comprising control means for controlling,
The correlation between the evaporator temperature and the valve opening is such that when the evaporator temperature is equal to or lower than a set temperature (t ₁ ), the valve opening is set to a preset maximum value, and the set temperature (t ₁ ). In the above, the valve opening is set to a correlation that decreases as the evaporator temperature increases from the maximum value, and further, the cooling water temperature is correlated with the cooling water temperature for heat exchange with the concentrated solution of the absorber. When the temperature is high, the maximum value is set small, and when the cooling water temperature is low, the maximum value is set large . The correlation in which the valve opening decreases as the evaporator temperature increases from the maximum value is set so that the valve opening decreases with a constant slope, and as the cooling water temperature decreases. The absorption chiller-heater according to claim 1 , wherein the inclination is set to be small. A regenerator that heats a dilute solution to generate refrigerant vapor and a concentrated solution, a condenser that condenses the refrigerant vapor generated in the regenerator, and a refrigerant liquid and a load fluid condensed in the condenser are heated. The evaporator that exchanges and cools the load fluid, the absorber that absorbs the refrigerant evaporated in the evaporator into the concentrated solution generated in the regenerator and generates the dilute solution, and the absorber that is generated in the absorber A liquid refrigerant proportional valve that is connected to a solution circulation pump that sends a dilute solution to the regenerator to form an absorption refrigeration cycle and that is provided in a refrigerant flow path that connects the condenser and the evaporator to adjust the refrigerant flow rate And an absorption chiller / heater comprising a control means for controlling the valve opening of the liquid refrigerant proportional valve,
The control means detects the temperature of the evaporator and the temperature of cooling water that exchanges heat with the concentrated solution of the absorber, and opens the liquid refrigerant proportional valve based on the detected evaporator temperature and cooling water temperature. The valve opening is controlled to a preset maximum value when the evaporator temperature is equal to or lower than a set temperature (t ₁ ), and the valve opening is equal to or higher than the set temperature (t ₁ ). Is controlled so as to decrease from the maximum value as the evaporator temperature increases, and the maximum value is decreased when the cooling water temperature is high, and the maximum value when the detected temperature of the cooling water is low. Absorption chiller / heater characterized by increasing the size .

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