JPH0320671B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for preventing crystallization of a solution in an absorption refrigerator. [Prior Art] In conventional absorption refrigerators, there is a risk that the solution will crystallize, for example, when there is a large change in cooling water temperature or when there is a large change in condensation temperature. To give an example of a large change in cooling water temperature, when used as a heat pump, the cooling water temperature at startup is significantly different from the cooling water temperature during steady operation.
For this reason, even if the same heat source temperature, for example the same steam temperature, is used, the amount of heat transfer in the generator will vary greatly, and at startup, a large amount of refrigerant will be released from the generator, and the solution at the generator outlet will be extremely concentrated, resulting in the risk of crystal formation. There is. [Problem to be solved by the invention] In a conventional absorption refrigerator, for example, the example shown in FIG.
In a LiBr-H ₂ O-based absorption heat pump designed to operate at a temperature of about 0.degree. C., the cycle shown in A occurs during steady operation, and the solution at the generator outlet balances at a concentration of 63%. The cooling water temperature will be low for a while even at startup (especially if a heat storage tank is used or the cooling water temperature will be low for a while).
In other words, if there is a large amount of hot water, it will take a long time).
If the condensing temperature has only risen to about 40℃, the heat source is the same, and the steam pressure is constant, for example, and the generator outlet temperature is 120℃ or higher, the cycle will be as shown in B, and the generator At the outlet, the concentration of the solution exceeds 70°C, reaching about 73%, and by the time it returns to the absorber it reaches the crystal line K and crystallizes. Even in cases where there is a large change in condensing temperature, if the cooling water system is dirty and a large amount of scale is expected to adhere, the refrigerator is designed to produce a specified capacity even with scale attached. In such cases, there is a large change in condensation temperature before and after scale adhesion, and at the beginning of installation or immediately after scale removal, the condensation temperature is low and a large amount of refrigerant is generated, increasing the solution concentration and causing the risk of crystal formation. When the temperature of the heat source for heating the vessel changes drastically, there are also problems such as a large amount of refrigerant being generated during intense heating, increasing the concentration of the solution and causing the risk of crystal formation. The present invention eliminates these conventional drawbacks and provides a method for preventing crystallization of an absorption refrigerator, which prevents the solution from being overconcentrated even when overload occurs, such as at startup or at the beginning of installation, and eliminates the risk of crystallization. The purpose is to provide [Means for Solving the Problems] The present invention has an absorber, a generator, a condenser, an evaporator solution heat exchanger, and a solution path and a refrigerant path that connect these devices. In the method for preventing crystallization of an absorption refrigerator having a heat source heat amount control valve that controls the heat source heat amount of This is a method for preventing crystallization in an absorption refrigerator, which is characterized by limiting the amount of crystallization. [Example] The present invention will be described with reference to the drawings in accordance with an example. As shown in Fig. 2, an absorber A, a generator G, a condenser C, an evaporator E, a solution heat exchanger
SP, a refrigerant pump RP are provided, pipes 1, 2, 3, 4, 5, a spray pipe 6, and an overflow pipe 7 are provided as a solution path, and pipes 8, 7 are provided as a refrigerant path.
9, a spray pipe 10, and a pipe 11 connect the above-mentioned devices to form a refrigeration cycle. In the figure, 12 is a heating tube, and 13 is a heat source heat amount control valve. The cooling water system includes a cooling water pump 14, piping 15, cooling water pipe 16, piping 17, cooling water pipe 18,
Although piping 19 is provided to cool the absorber A and the condenser C, there is also a method of cooling with air instead of this cooling water. In this case, a cooling fan is used instead of the cooling water pump 14. 20 is a cold water pipe which guides cold water to the evaporator E through pipes 21 and 22. 23 is a temperature detector that detects the cold water outlet temperature;
4 is a temperature detector that detects the outlet temperature of the cooling water of condenser C; 26 is a temperature detector that detects the condensation temperature in condenser C; 25 is a controller that is temperature detector 2;
3, 24, and 26 to operate the heat source heat amount control valve 13. The operation of this control mechanism will be explained. For example, when performing a cooling cycle, during steady operation, the temperature of the cold water is controlled by adjusting the opening degree of the heat source heat amount control valve 13 via the controller 25 in response to a signal of the cold water outlet temperature from the temperature detector 23. During heating or when the heat pump is operating, the temperature of the hot water is controlled based on the hot water outlet temperature signal from the temperature detector 24. If the cooling water temperature is low or the heat transfer coefficient of the cooling water pipe 18 is high and an overload is applied at startup or at the beginning of installation, the amount of refrigerant condensed in the condenser C increases and the solution concentration increases. . At this time, the concentration of the solution at the outlet of the generator C is detected, and if there is a risk of crystal formation, the heat source heat amount control valve 13 is operated in the direction of closing to reduce the amount of heating. In this case, in order to prevent hunting, it is preferable that the set value has a certain width Δξ. Within this range of Δξ, the controller 25 operates the valve in the closing direction based on the input signal, but it is safer if the controller 25 does not operate the valve in the opening direction. The preferred location for detecting the concentration of the solution is near the outlet of the generator G.There is also a method of estimating the cycle concentration from the liquid level height of the evaporator E, but this method only estimates the average concentration, so the crystallization In order to avoid this, it is necessary to know the local concentration at a place where the concentration is high, and the generator outlet satisfies this condition and is even more preferable because it shows the current concentration. The concentration detection method is as follows: (1) Determine the concentration from the specific gravity and temperature using a hydrometer (generator outlet system). (2) Determine the concentration from the saturation pressure (or the dew point relative to the saturation pressure, that is, the saturation temperature relative to the pressure) and the solution temperature (generator outlet). The latter (2) will be explained below. The generator outlet solution is approximately in equilibrium between pressure and solution temperature. Therefore, the concentration can be determined from this relationship. The dew point and condensing temperature are almost the same. In the case of LiBr-H ₂ O system, when the solution concentration is in the range of ξ=0.60 to 0.70 (LiBr/LiBr+H ₂ O), ξ=[1.15×T- W+2.6/90.57+0.72×T] ^0.55
Represented by ⁶ . The error is about ±0.005 in the range of T=20 to 170°C. In addition, as a simple method for determining the concentration, the solution temperature T
The table below can be considered based on the difference between ΔT and dew point (condensation temperature) W, ΔT=T−W.

〔Effect of the invention〕

The present invention detects the concentration of solution at the outlet of the generator, and when the detected value exceeds a set value, limits the opening degree of the heat source heat amount control valve. It is possible to suppress the rise in the absorption chiller and safely operate the absorption refrigerator without the risk of crystallization, which has an extremely large practical effect.

[Brief explanation of the drawing]

Fig. 1 is a cycle diagram of an absorption refrigerator, Fig. 2 is a flow chart of an embodiment of the present invention, and Figs. 3, 4, and 5 are diagrams showing methods for determining respective set values. . A...absorber, G...generator, C...condenser,
E...Evaporator, X...Solution heat exchanger, SP...Solution pump, RP...Refrigerant pump, 1, 2, 3, 4,
5... Piping, 6... Spray pipe, 7... Overflow pipe, 8, 9... Piping, 10... Spray pipe, 11... Piping, 12... Heating tube, 13... Heat source heat amount control valve, 14 ...Cooling water pump, 15...
Piping, 16... Cooling water pipe, 17... Piping, 18...
...Cooling water pipe, 19...Piping, 20...Cold water pipe, 2
1, 22... Piping, 23, 24... Temperature detector,
25...Controller, 26...Temperature detector.

Claims (1)

[Claims] 1. It has an absorber, a generator, a condenser, an evaporator solution heat exchanger, and a solution path and a refrigerant path that connect these devices, and controls the amount of heat source heat for heating in the generator. A method for preventing crystallization in an absorption refrigerator having a heat source heat amount control valve, characterized in that the concentration of the solution at the outlet of the generator is detected, and when the detected value exceeds a set value, the degree of opening of the heat source heat amount control valve is limited. Method for preventing crystallization in absorption refrigerators. 2. The method of claim 1, wherein the detection of the generator outlet solution concentration is performed by determining the concentration based on the generator solution outlet temperature and the condensing temperature of the condenser. 3. The method according to claim 1, wherein the detection of the generator outlet solution concentration is performed by determining the concentration based on the difference between the generated solution outlet temperature and the condensing temperature of the condenser. 4. The method according to claim 1, wherein the set value is determined by detecting the outlet temperature of the solution on the heating side of the solution heat exchanger.