JPS5823542B2 - Method for controlling the refrigeration capacity of a hot water heating absorption chiller according to the refrigeration load - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot water heating absorption refrigerator using lithium salt as an absorbent and water as a refrigerant.

More specifically, the concentration of the absorbent aqueous solution circulating to the generator is changed in response to fluctuations in the amount of heat input to the generator.

The present invention relates to a method for controlling the refrigeration capacity of a hot water heating absorption refrigerator that includes a concentration adjustment chamber for increasing the temperature in accordance with fluctuations in the refrigeration load with a good coefficient of performance (hereinafter referred to as efficiency).

FIG. 1 is a system diagram for explaining the configuration of this type of hot water heating absorption refrigerator, in which 1 is a generator for heating an aqueous absorbent solution, and 2 is a system diagram for converting water vapor generated in the generator 1 into a concentrated absorbent refrigerating machine. 3 is a condenser that condenses the water vapor from separator 2; 4 is an evaporator that evaporates the condensed water; 5 is a concentrated water vapor that is separated from the water vapor from evaporator 4 by separator 2; an absorber for absorbing into an absorbent aqueous solution; 6 is a heat exchanger;
7 is a concentrated solution tank provided in the heat exchanger 6; 8 is a liquid lift pipe connecting the generator 1 and the separator 2; 9.10, 11°12.1
3 is a pipe connecting each part, 14 is a condenser 3, an absorber 5,
and a cooling water pipe for introducing cooling water into the concentration adjustment chamber 20, 15 a heating hot water pipe for heating the absorbent aqueous solution in the generator 1, 16 an evaporator coil introduced into the evaporator 4, and 17 a cooling water pipe for introducing cooling water into the concentration adjustment chamber 20; A U-shaped pipe provided between the condenser 3 and the evaporator, 18 is a pipe for guiding water from the condenser 3 to the U-shaped pipe,
19 is a conduit for guiding the refrigerant in the U-shaped pipe 17 to the evaporator;
20 is a concentration adjustment chamber connected to one end of the U-shaped tube 17 and maintained at a constant pressure; 21 is a cooling water coil for keeping the pressure in the concentration adjustment chamber constant; 22 is the pressure of the separator 2 (generator 1) to the other end of the U-shaped tube 17 that is not connected to the concentration adjustment chamber 20;
23 is an orifice for maintaining a pressure difference between the evaporator 4 and the U-shaped tube 17, and 24 is an orifice for suppressing rapid inflow and outflow of refrigerant.

The refrigeration action of a hot water heating absorption refrigerator equipped with such a concentration adjustment chamber and the function of the concentration adjustment chamber are disclosed in detail in Japanese Patent Application Laid-Open No. 51-34446, filed by the same applicant, and are therefore omitted here. .

Generally, in this type of refrigerator, when the refrigeration load fluctuates, the efficiency decreases if the amount of heat input to the generator 1 is kept constant.

Conventionally, as a countermeasure for this, the outlet temperature (or inlet temperature) of the secondary refrigerant (hereinafter referred to as cold water) in the evaporator 4 is detected, and the circulation of hot water for heating (hereinafter referred to as heat medium) to the generator 1 is thereby controlled. The amount of heat input was controlled using an ON-OFF method or a flow rate variation method.

However, these methods have the following drawbacks.

(1) Due to the ON-OFF system, the generator, the solution heat exchanger, and the pipes connecting each part are at high temperatures, and the practical efficiency decreases by the amount of heat released when the system is OFF.

(2) Disadvantages of flow rate variation method This will be explained with reference to FIG.

In Figure 2, the horizontal axis is the chilled water outlet temperature of the evaporator, and the vertical axis is the efficiency (upper) and refrigeration capacity (lower). It is a graph showing the relationship between cold water outlet temperature and efficiency or refrigerating capacity using the flow rate of a heating medium as a parameter.

In the graph, Vn represents the flow rate, and is Vn Vn 1.

As is clear from the graph in Figure 2, a decrease in the flow rate of the heat medium leads to a decrease in the amount of heat input, and therefore the maximum refrigerating capacity decreases, and the concentration adjustment chamber functions to increase the concentration of the absorbent solution circulating inside the refrigerator. As a result, the absorption capacity of the absorber decreases, and the refrigerating capacity diagram shifts diagonally downward to the right and the efficiency diagram shifts to the right.

Here, control is performed so that the chilled water outlet temperature is always a constant temperature T1, that is, if the chilled water outlet temperature TX is T1>Tx, the heat medium flow rate is decreased, and in the opposite state, the flow rate is increased. When this is done, for example, the cooling load Q is balanced by the heat medium flow rate vn and the chilled water dust temperature.
2 decreases to Ql, the cold water outlet temperature T1
It becomes stable at a heat medium flow rate V indicating the refrigerating capacity of Ql -1.

However, in this case, c, o, and p decrease from η2 to η1Vc, and T in the vn state even without controlling the heat medium flow rate.

Since it is stable at the temperature of c, o,
The result is that p is the same, and this control method is 0N
-OFF is eliminated, and the effect is only to prevent a decrease in efficiency caused by this, and it is not possible to prevent a decrease in the coefficient of performance due to a decrease in the cooling load.

Therefore, in order to eliminate such problems, either the set cold water outlet temperature T1 should be set to a high value, or the set temperature should be shifted depending on the heat medium flow rate, that is, the set temperature should be set high when the cooling load is small.

However, keeping the set temperature constantly high is not desirable due to the balance of the heat sink on the load side.
Furthermore, the method of shifting the set temperature according to the flow rate of the heat medium also complicates control, which is also not desirable.

In contrast, the present invention constantly obtains high c, o, and p by changing the splitting ratio of cooling water flowing in parallel in the absorber and condenser of the refrigerator.

That is, the present invention includes a generator that boils an absorbent aqueous solution by heating it with hot water, a separator that separates water vapor generated in the generator from a concentrated absorbent aqueous solution, and a water vapor sent from the separator that is condensed into water. A condenser, an evaporator in which the water obtained in the condenser is vaporized again by taking heat from other fluids through heat exchange, and a separator in which the water vapor generated in the evaporator is absorbed by a concentrated aqueous absorbent solution that is separated. The refrigeration capacity of the hot water heating absorption refrigerator includes an absorber that converts the absorbent aqueous solution into an aqueous solution, and a concentration adjustment chamber that changes the concentration of the absorbent aqueous solution circulating to the generator according to fluctuations in the amount of heat input to the generator. The method for controlling according to the load is characterized in that the flow rate ratio of the cooling water flowing through the condenser and the absorber is changed according to the refrigeration load.

The present invention provides a method for controlling the refrigeration capacity of a hot water heating absorption refrigerator according to the refrigeration load.

The method of the present invention will be described in detail with reference to FIGS. 3 and 4.

According to the inventor's experiments, it has been confirmed that the relationship among the cold water outlet temperature, the ratio of the amount of cooling water between the absorber and the condenser (VA/VC), and the coefficient of performance or refrigeration capacity is as shown in Figure 3. It was done.

Figure 3 shows the ratio of the amount of cooling water between the absorber and the condenser, with the horizontal axis representing the chilled water outlet temperature, the temperature and flow rate of the heating medium entering the generator being constant, and the total flow rate of cooling water being constant. a/
3 is a graph showing the relationship between coefficient of performance and refrigeration capacity as vo parameters.

ν Here, when Vc is decreased, the condensation temperature increases and the amount of heat input decreases, so the maximum refrigerating capacity decreases.

However, in this case, the refrigerant is stored in the concentration adjustment chamber due to the increase in internal pressure accompanying the increase in condensation temperature, and the concentration of the absorbent aqueous solution in the system increases.

Furthermore, the amount of cooling water to the absorber increases by the amount of decrease in the amount of cooling water to the condenser.

Therefore, the absorption capacity increases synergistically due to these two phenomena.

Therefore, due to the decrease in VC, the refrigerating capacity diagram is diagonally downward to the left.
The graph of the coefficient of performance will shift to the left.

Therefore, the cooling water distribution ratio is controlled so that the chilled water outlet temperature becomes a constant temperature T1, that is, the chilled water outlet TX is kept at the set temperature T1.
When controlling the flow rate to the condenser so that it decreases if T1>TX for 1 and increases it under the opposite conditions, for example, when changing from a state where the split ratio is 1:1 and the cooling load Q2 to Ql, When the chilled water outlet temperature is T1, it becomes stable in the state of η2:1, which indicates the refrigerating capacity of Ql.
The coefficient of performance also increases slightly due to the increase in absorption capacity, and may remain constant depending on the conditions), and the decrease in the coefficient of performance does not occur due to the decrease in the cooling load as described above.

FIG. 4 is a schematic diagram of a preferred embodiment of the method of the present invention, in which the same numbers as in FIG. 1 indicate the same parts.

In this example, the temperature of the cold water coming out of the evaporator 4 is evaporated.

The temperature is detected by the temperature detector 31 provided on the vessel coil 16, and this signal is sent to the control circuit 32, which rotates the motor 33 appropriately and adjusts the flow divider 34 to control the absorber 5 and condenser 3.
This is done by changing the amount of cooling water supplied to the system.

As described above, in the method of the present invention, the refrigeration capacity can be varied in response to the variation in the refrigeration load in a hot water heating absorption refrigerator including a concentration adjustment chamber, without at least impairing the coefficient of performance.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a hot water heating absorption refrigerator including a concentration adjustment chamber, and Figure 2 is the relationship between the heat medium flow rate, chilled water outlet temperature, and refrigerating capacity or coefficient of performance in a conventional method using the heat medium flow rate as a parameter. FIG. 3 is a graph showing the relationship between the ratio of cooling water amounts, the chilled water outlet temperature, and the refrigerating capacity or coefficient of performance in a method in which the ratio of the amounts of cooling water flowing through the absorber and condenser is a parameter according to the present invention.
The figure is a schematic diagram showing a specific example suitable for carrying out the method of the invention. 1... Generator, 2... Separator, 3...
... Condenser, 4 ... Evaporator, 5 ...
・Absorber, 20... Concentration adjustment room, 31...
...Temperature detector, 32... Control circuit, 33...
...Motor, 34...Diversion valve.

Claims (1)

[Claims] 1. A generator that boils the absorbent aqueous solution by heating it with hot water, a separator that separates the water vapor generated in the generator from the concentrated absorbent aqueous solution, and a condenser that condenses the water vapor sent from the separator into water. , an evaporator in which the water obtained in the condenser is vaporized again by taking heat away from other fluids through heat exchange, and an absorbent aqueous solution in which the water vapor generated in the evaporator is absorbed into a concentrated aqueous absorbent solution separated in a separator. The refrigeration capacity of the hot water heating absorption chiller, which includes a concentration adjustment chamber that changes the concentration of the absorbent aqueous solution circulating to the generator according to fluctuations in the amount of heat input to the absorber and generator, is adjusted to the refrigeration load. The method of controlling the refrigerating capacity of the hot water heating absorption refrigerator according to the refrigerating load is characterized in that the flow rate ratio of the cooling water flowing through the condenser and the absorber is changed according to the refrigerating load. How to control