JPH043860A - Absorption freezer - Google Patents

Abstract

PURPOSE:To prevent any over-dropping in temperature at an outlet for cold water by a method wherein a refrigerant pump is operated when the temperature of cold water at the outlet port after elapsing of the second predetermined time is at least at the third predetermined temperature higher than the second predetermined temperature. CONSTITUTION:A refrigerant pump control device 42P for controlling an operation of a refrigerant pump 19P in response to a temperature at a cold water outlet from an evaporator 4 is provided. This refrigerant pump control device 42P stops the refrigerant pump 19P when the temperature of the cold water at the outlet is lower than the first predetermined temperature. After this operation, when the temperature of cold water at the outlet becomes the second predetermined temperature higher than the first predetermined temperature, the refrigerant pump 19P is operated for the first predetermined time, and after elapsing of the first discrimination time, the refrigerant pump 19P is stopped. After this operation, the refrigerant pump 19P is kept at its stopped state for the second predetermined period of time. The refrigerant pump 19P is operated when the temperature at the cold water outlet after elapsing the second predetermined time is at least at the third predetermined temperature higher than the second predetermined temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an absorption refrigerating machine, and more particularly to an absorption refrigerating machine equipped with a refrigerant pump for circulating and distributing refrigerant liquid to an evaporator.

(b) Conventional technology For example, Japanese Patent Application Laid-Open No. 63-129262 discloses a refrigerant pump that circulates and sprays the refrigerant liquid accumulated in the refrigerant receiving section at the lower part of the evaporator to the evaporator, and a control device for this refrigerant pump. Prepare,
This refrigerant pump control device discloses an absorption refrigerator having a mechanism for intermittent operation of the refrigerant pump when the chilled water load decreases and the chilled water outlet temperature from the evaporator decreases.

(c) Problems to be Solved by the Invention In the absorption chiller shown in the above-mentioned prior art, when the chilled water load decreases and the chilled water outlet temperature drops and the refrigerant pump operates intermittently at predetermined intervals, the intermittent operation As the time increases, the concentration of the absorption liquid increases and the refrigerant absorption capacity of the absorber increases, and the chilled water outlet temperature decreases rapidly during operation of the refrigerant pump. In addition, even if the refrigerant pump is stopped, refrigerant remains in the evaporator tray and is not completely sprayed, and refrigerant remains on the dripping heat transfer tube, so even after the refrigerant pump is stopped, the refrigerant remains undispersed. There is a possibility that the cold water outlet temperature decreases until the dripping completely stops, and the decrease in the cold water outlet temperature due to overshoot becomes large.

Furthermore, if the ON-OFF interval of the refrigerant pump is reduced in order to reduce the drop in the chilled water outlet temperature, the number of times the refrigerant pump starts and stops increases, which may deteriorate the durability of the refrigerant pump.

An object of the present invention is to prevent a significant drop in the temperature of the chilled water outlet of an absorption refrigerator and to avoid frequent starting and stopping of the refrigerant pump.

(d) Means for Solving the Problems In order to solve the above problems, the present invention provides a high temperature generator (1).
The condenser (3), the evaporator (4), and the absorber (5) are connected to form a refrigeration cycle, and a refrigerant pump ( 19P)
In the absorption refrigerator connected to the evaporator (4), the refrigerant pump (19P
), and this refrigerant pump control device (42P) controls the operation of the refrigerant pump (19
F), and then, when the cold water outlet temperature reaches a second predetermined temperature higher than the first predetermined temperature, the refrigerant pump (1
9P) is operated for a first predetermined time, and when this first predetermined time has elapsed, the refrigerant pump (19F) is stopped, and then,
The refrigerant pump (19P) is held in a stopped state for a second predetermined period of time, and when the chilled water outlet temperature after the elapse of the second predetermined period is equal to or higher than a third predetermined temperature higher than the second predetermined temperature, the refrigerant pump (
19P) is provided.

In addition, a water heater (35) is attached to the high temperature generator (1), and during hot water main control operation, the amount of heating of the high temperature generator (1) is adjusted according to the hot water outlet temperature from the water heater (35). Device (4
2) is equipped with a refrigerant pump control device (42P) that controls the operation of the refrigerant pump (19P) according to the chilled water outlet temperature, and this refrigerant pump control device (42P)
2P) is the refrigerant pump (19
P), then when the chilled water outlet temperature rises, the refrigerant pump (19P) is operated for a predetermined time, then the refrigerant pump (19F) is stopped for a predetermined time, and according to the chilled water outlet temperature at the time when the predetermined time elapses. This provides an absorption refrigerator that operates a refrigerant pump (19P).

(*) When the effect absorption chiller is operating or hot water main control is operating, when the chilled water load decreases and the chilled water outlet temperature stops, the refrigerant pump (19P) is stopped, and then the chilled water outlet temperature rises. When the predetermined temperature is reached, the refrigerant pump (19P) is operated for a predetermined time to circulate the refrigerant liquid to the evaporator (4), and then the refrigerant pump (19P) is stopped, and after the predetermined time elapses, the chilled water outlet temperature rises. Refrigerant pump (19P) when
The refrigerant pump (19P) continues to stop when the chilled water outlet temperature does not change or decreases, making it possible to reliably avoid an excessive drop in the chilled water outlet temperature. It is possible to prevent frequent operation and stop of the pump (19P) and stabilize the operation of the absorption refrigerator.

(F) Example Hereinafter, an example of the present invention will be described in detail based on the drawings.

The one shown in Figure 1 is an absorption chiller that is equipped with a water heater and can supply cold water and hot water at the same time (hereinafter referred to as an absorption chiller/heater).
This uses water (H, O) as a refrigerant and an aqueous solution of lithium bromide (LiBr) as an absorbent (absorbing liquid).

In Figure 1, (1) is a high temperature generator equipped with a burner (IB), (2) is a low temperature generator, (3) is a condenser, (3A)
is a refrigerant reservoir, (4) is an evaporator, (4A) is a tray for distributing refrigerant, (5) is an absorber, (6) is a low-temperature heat exchanger,
(7) is a high temperature heat exchanger, (8) or 14) is an absorption liquid pipe, (15) is an absorption liquid pump, <16) and (17) are refrigerant pipes, (18> is a refrigerant liquid flow down pipe, 19) is a refrigerant liquid circulation pipe, (19P) is a refrigerant pump, (2A) is an overblow pipe, (20) is a fuel supply pipe connected to the burner (IB), (21) is a heating amount control valve, (22) ) is cold water piping,
(23) is an evaporator heat exchanger, each of which is connected by piping as shown in FIG. Also, (A) is the upper torso,
(B) is the lower torso. Furthermore, (25) is a cooling water pipe, and an absorber heat exchanger (26) and a condenser heat exchanger (27> are provided in the middle of this cooling water pipe (25). ) is a refrigerant drain control valve provided in the refrigerant pipe (17).

(35) is a water heater attached to the high temperature generator (1), (3
6) is a hot water drain pipe that connects the lower part of the water heater (35) and the high temperature generator (1), and this hot water drain pipe (36)
A hot water drain control valve (37) is provided in the middle.

Also, (38) is a hot water pipe, and this hot water pipe (38)
A water heater heat exchanger (40) is provided in the middle.

(41) is a cold main/heat main switching device that switches between cold water main control and hot water main control, (42) is a heating amount control valve (21), a refrigerant drain control valve (30), and a hot water drain control valve (37). This is a control device that adjusts the opening degree, etc., and the control device (42) is provided with a refrigerant pump control device (42P) that controls operation and stop of the refrigerant pump (19F). Further, (43) and (44) are a cold water inlet temperature detector and a cold water outlet temperature detector respectively attached to the cold water pipes (22) on the inlet side and outlet side of the evaporator (4), (45) and (46). are a hot water inlet temperature detector and a hot water outlet temperature detector respectively attached to the hot water piping (38) on the inlet side and outlet side of the water heater (35). And the cold water inlet temperature detector (4
3) and the hot water inlet temperature detector (45) are connected to the cold main/heat main switching device (41), and the cold water outlet temperature detector (44) and the hot water outlet temperature detector (46) are connected to the control device (42). has been done. In addition, (47) is a cold main/warm main switching device (41
) is the switching circuit, (48) is the switching contact, and the switching contact (
48) is switched between the cold water main control side contact C and the hot water main control side contact H according to the cold water inlet temperature and the hot water inlet temperature, as shown in FIG.

In addition, when the switching contact piece (48) is closed to the cold water main control side contact C, that is, during the cold water main control, the control device (42) operates the heating amount control valve according to the temperature detected by the cold water outlet temperature detector (44). (21) Opening degree is PID controlled (proportional actuator integral operation +
The hot water drain control valve (37) is adjusted according to the temperature detected by the hot water outlet temperature detector (46).
) is adjusted by P control (proportional control). Further, when the switching contact piece (48) is closed to the hot water main control side contact H, that is, during hot water main control, the control device (42) detects the detected temperature of the cold water outlet temperature detector (44) (hereinafter referred to as the cold water outlet temperature). The opening degree of the refrigerant drain control valve (30) is adjusted by P control according to the temperature (hereinafter referred to as "hot water outlet temperature"), and the opening degree of the heating amount control valve (30) is adjusted according to the temperature detected by the hot water outlet temperature detector (46) (hereinafter referred to as "hot water outlet temperature").
21) is adjusted by PID control. Further, the refrigerant pump control device (42P) controls operation and stop of the refrigerant pump (19P) according to the cold water outlet temperature.

During operation of the absorption chiller/heater configured as described above, when the cold water inlet temperature is, for example, 10.0°C and the hot water inlet temperature is, for example, 57.0°C, the cold main/heat main switching device (41)
The switching contact piece (48) is switched to the cold water main control side contact C. Therefore, the control device (42) inputting the signal from the cold main/heat main switching device (41) performs the main control of the chilled water as described above, and switches the heating amount control valve (21) according to the chilled water outlet temperature.
An opening signal is output to the control valve (21), and the opening of the control valve (21) is adjusted by PID control. Further, the control device (21) outputs an opening degree signal to the hot water drain control valve (37) according to the hot water outlet temperature, and the opening degree of the hot water drain control valve (37) is adjusted by P control. Further, the control device (42) outputs a fully open signal to the refrigerant drain control valve (30), and outputs a fully open signal to the refrigerant drain control valve (30).
0) is fully open. In addition, the absorption liquid pump (15) and cold tofu pump (19F) are operated, and the absorption liquid and refrigerant are circulated in the same way as in conventional absorption chiller/heating machines, and the cold water whose temperature has been lowered in the evaporator heat exchanger (23) is supplied to the load. Then, as described above, the opening degree of the heating amount control valve (21) is adjusted by PID control according to the cold water outlet temperature, and the heating amount of the high temperature generator (1) changes, so that the cold water outlet temperature is almost the set temperature. The change in the cold water outlet temperature is small.

In addition, a part of the refrigerant vapor separated from the absorption liquid in the high temperature generator (1) flows to the water heater (35), and is transferred to the water heater heat exchanger (40).
) to exchange heat with flowing hot water and condense. The condensed refrigerant liquid then returns to the high temperature generator (1) via the hot water drain pipe (36) and the hot water drain control valve (37).

Moreover, the hot water whose temperature has been increased by the water heater heat exchanger (40) can be completely supplied to the load. At this time, the opening degree of the hot water drain control valve (37) is adjusted by P control according to the hot water outlet temperature as described above. When the hot water outlet temperature decreases, the opening degree of the hot water drain control valve (37) increases in proportion to the decrease, and the refrigerant liquid level in the water heater (35) decreases. When the refrigerant liquid level decreases, the heat exchange area of the water heater heat exchanger (40) increases, the amount of heat exchange increases, and the hot water outlet temperature increases.

Further, when the hot water outlet temperature rises, the opening degree of the hot water drain control valve (37) decreases in proportion to the rise, and the refrigerant liquid level of the water heater (35) rises. When the refrigerant liquid level rises, the heat exchange area of the water heater heat exchanger (40) decreases, the amount of heat exchange decreases, and the hot water outlet temperature decreases.

In addition, the hot water load is large and the hot water inlet temperature is, for example, 55.2.
℃, and when the cold water inlet temperature is, for example, 9.0℃,
The switching contact piece (48) of the cold/warm main switching device (41) has been switched to the hot water main control side contact H. Therefore, the control device (42) inputting the signal from the cold main/heat main switching device (41) controls the hot water main control and outputs an opening signal to the heating amount control valve (21) according to the hot water outlet temperature. and heating amount control valve (21
) is adjusted by PID control. Alternatively, the control device (42) controls the refrigerant drain control valve (3) according to the chilled water inlet temperature.
0), and the opening degree of the refrigerant drain control valve (30) is adjusted by P control. Also, a control device (42)
outputs a fully open signal to the hot water drain control valve (37), and the hot water drain control valve (37) is fully open. When the chilled water outlet temperature rises, the opening degree of the refrigerant drain control valve (30) increases in proportion to the rise. The amount of refrigerant flowing from the high temperature generator (1) through the refrigerant pipes (16), (17) and the low temperature generator (2) to the condenser (3) increases, and also in the low temperature generator (2). The amount of refrigerant vapor generated increases. For this reason, the amount of refrigerant flowing from the condenser (3) to the evaporator (4) increases, and the temperature at the outlet of the chilled water from the evaporator (4) decreases.Also, when the outlet temperature of the chilled water decreases, the temperature increases proportionally. Then, the opening degree of the refrigerant drain control valve (30) becomes smaller.Then, contrary to the case where the chilled water outlet temperature increases, the amount of refrigerant liquid flowing from the condenser (3) to the evaporator (4) decreases. As a result, the cold water outlet temperature increases.

Further, the opening degree of the heating amount control valve (21) is adjusted by PID control according to the hot water outlet temperature, so that the hot water outlet temperature is maintained at approximately the set temperature, and the change in the hot water outlet temperature is slight.

Hereinafter, the control of the absorption chiller/heater when the chilled water load decreases and the chilled water outlet temperature decreases when the absorption chiller/heater is operated under hot water main control will be explained based on FIGS. 2 and 3. As shown in Figure 2, when the chilled water outlet temperature decreases to 8°C or less, the control device (42) operates, and the opening degree of the refrigerant drain control valve (3o) decreases as the chilled water outlet temperature decreases. , the amount of refrigerant flowing through the refrigerant pipes (16) and (17) to the condenser (3) is reduced. Then, when the cold water outlet temperature reaches a second predetermined temperature, for example, 6.0° C., the refrigerant drain control valve (30) closes. Thereafter, when the chilled water load further decreases and the chilled water outlet temperature becomes lower than the first predetermined temperature, for example 5.5°C, the refrigerant pump control device (42P
) outputs a stop signal to the refrigerant pump (19P), and the refrigerant pump (19P) stops. And tray (4A) 1
7) When the refrigerant liquid runs out, the refrigerant liquid is no longer distributed to the evaporator heat exchanger (23) of the evaporator (4). Thereafter, the refrigerant pump (19P) is stopped, and if the cold water load continues to be small, the cold water outlet temperature increases. When the chilled water outlet temperature reaches a second predetermined temperature, for example 6.0°C, the refrigerant pump control device (42P) operates, and the refrigerant pump (19
Outputs the operation signal to P). At the same time, the timer device (T) provided in the refrigerant pump control device (42P) starts measuring time. Refrigerant pump (19P) depending on the operation signal
When the evaporator (4) starts operating, the refrigerant liquid accumulated in the evaporator (4) is sent to the tray (4A) of the evaporator (4).
When the refrigerant liquid accumulates in the tray (4A), the refrigerant liquid flows into the tray (4A).
A) to the evaporator heat exchanger (23).

When the refrigerant pump (19P) starts operating and a first predetermined period of time, for example, 10 seconds has elapsed, the timer device (T) stops measuring time and resets it.

In addition, the refrigerant pump control device (42P) controls the refrigerant pump (19
A stop signal is output to P), and the refrigerant pump (19P) stops. Thereafter, the refrigerant liquid accumulated in the tray (4A) is continuously sprayed to the evaporator heat exchanger (23). Also, at the same time as the refrigerant pump (19P) stops, the timer device (T) is reset and starts counting time again. If the chilled water load has increased when the refrigerant pump (19P) stops operating, the chilled water outlet temperature gradually increases as shown in (■) in FIG. In addition, if the chilled water load is small or zero, the refrigerant pump (19
After P) is stopped, the cold water outlet temperature hardly changes or the cold water outlet temperature gradually decreases.

After the refrigerant pump (19P) stops, a second predetermined time,
For example, after 30 seconds have elapsed, the timer device (T) stops measuring time and resets it. If the cold water outlet temperature at this time is higher than the third predetermined temperature, for example 6.5°C, the refrigerant pump control device (42P) operates and outputs an operation signal to the refrigerant pump (19P), Refrigerant pump (1
9F> starts operating, and refrigerant liquid is sprayed into the evaporator heat exchanger (23). Moreover, when the second predetermined time period has elapsed,
When the cold water outlet temperature is 6.5° C. or lower, the refrigerant pump control device (42P) does not output an operation signal to the refrigerant pump (19P), and the refrigerant pump (19P) continues to be in a stopped state. Then, when the chilled water outlet temperature rises due to an increase in the chilled water load and becomes higher than 6.5°C as described above, the refrigerant pump control device (42P) outputs an operation signal to the refrigerant pump (19P). When the refrigerant pump (19F) starts operating, the refrigerant liquid is distributed to the evaporator heat exchanger (23), and cold water whose temperature has been reduced is supplied from the evaporator (3) to the load. Also, as mentioned above, when the refrigerant pump (19P) is operating or stopped, the chilled water outlet temperature is 6.
．． When the temperature rises above 0°C, the opening degree of the refrigerant drain control valve (30) is controlled according to the chilled water outlet temperature.

Thereafter, when the cold water outlet temperature becomes 5.5°C or less again, the operation of the refrigerant pump (19P) is controlled as described above. When the hot water load decreases, or when the cold water load increases and the cold water inlet temperature and hot water inlet temperature enter the range of cold water main control, the cold main/heat main switching device (41) operates, and the hot water main control starts. Switched to chilled water main control.

According to the above embodiment, during hot water main control operation, for example, when the cold water load remains low for a long time and the cold water outlet temperature drops to 6.0°C, the refrigerant drain control valve (30) closes. Furthermore, when the chilled water outlet temperature decreases to 5.5°C, the refrigerant pump control device (42P) operates and the refrigerant pump (
19P) stops operation. After that, when the chilled water outlet temperature rises to 6.0°C, the refrigerant pump (19P) is operated for a predetermined time, and then the refrigerant pump (19F) is allowed to stop for a predetermined time, causing a large chilled water load. When the chilled water outlet temperature after a predetermined period of time is higher than 6.5°C, the refrigerant pump (19P) is operated and the chilled water load is only 6.5°C.
When the temperature is below C, do not operate the refrigerant pump (19P),
The operation of the refrigerant pump (19P) is stopped until the chilled water outlet temperature becomes higher than 6.5°C.
) can avoid an excessive drop in the chilled water outlet temperature when the operation is started after the operation has stopped, and as a result, the operation of the absorption chiller/heater can be stabilized. Further, it is possible to avoid frequent stoppage and repeated operation of the refrigerant pump (19P) due to a large change in the cold water outlet temperature, and it is possible to use the refrigerant pump (19F) for a long period of time.

Further, in the above embodiment, an absorption chiller/heater was explained, but for example, an absorption chiller that does not have a water heater (35) attached to the high temperature generator (1) and takes out only cold water can also be used in the same manner as in the above embodiment. When the chilled water load is small and the chilled water outlet temperature drops significantly, the refrigerant pump (19P) is stopped, and when the chilled water outlet temperature rises to, for example, 6.0°C, the refrigerant pump (19P) is operated. Then, for example, after 10 seconds, the cold tofu pump (19P) is stopped, and after 30 seconds, if the chilled water outlet temperature is higher than, for example, 6.5°C, the refrigerant pump (19F) is operated, and 6.
If the temperature is below 5°C, then the cold water outlet temperature will be 6.5°.
By stopping the refrigerant pump (19P) until the temperature becomes higher than C, when the refrigerant pump (19P) starts operating, it is possible to avoid an excessive drop in the chilled water outlet temperature, and
It is possible to prevent the refrigerant pump (19P) from repeatedly starting and stopping the refrigerant pump (19P), and to use the refrigerant pump (19P) for a long period of time.

In addition, when the chilled water outlet temperature drops, the refrigerant pump (19P)
The temperature of the cold water outlet to stop, then the refrigerant pump (19P
) to operate the chilled water outlet, then the refrigerant pump (1
The first predetermined time period during which the refrigerant pump (19P) is operated, the second predetermined time period during which the refrigerant pump (19P) is forcibly stopped after the first predetermined time period, etc. are set at the temperature or time shown in the above example. It is not limited, and is set depending on the capacity of the absorption chiller/heater, etc., the capacity of the refrigerant pump, etc.

(G) Effects of the Invention The present invention is an absorption refrigerating machine configured as described above, and includes a refrigerant pump control device that controls the operation of the refrigerant pump according to the chilled water outlet temperature. The refrigerant pump is stopped when the outlet temperature becomes equal to or lower than the first predetermined temperature, and when the chilled water outlet temperature rises to a second predetermined temperature, the refrigerant pump is operated for a first predetermined time, and then the The absorption chiller It is possible to prevent an excessive drop in the temperature of the chilled water outlet during operation, and to avoid frequent operation and stop of the refrigerant pump, thereby stabilizing the operation of the absorption refrigerating machine.

In addition, in an absorption chiller equipped with a water heater attached to the generator and a control device that adjusts the heating amount of the generator according to the hot water outlet temperature of the water heater when operating under hot water main control, a refrigerant pump control device that controls the operation of the refrigerant pump, and the refrigerant pump control device stops the refrigerant pump when the cold water outlet temperature becomes equal to or lower than a first predetermined temperature during hot water main control operation; Thereafter, when the chilled water outlet temperature reaches a second predetermined temperature higher than the first predetermined temperature, the refrigerant pump is operated for a first predetermined time, and then the refrigerant pump is kept stopped for a second predetermined time, and the refrigerant pump is operated for a second predetermined time. When the chilled water outlet temperature after the lapse of the second predetermined time is equal to or higher than the third predetermined temperature, which is higher than the second predetermined temperature, the refrigerant pump starts operating. Even if it continues for a long time, it is possible to prevent the cold water outlet temperature from dropping excessively, and also to avoid frequent operation and stop of the refrigerant pump, making it possible to stabilize the operation of the absorption refrigerator.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram of an absorption chiller/heater showing an embodiment of the present invention; Fig. 2 is an explanatory diagram of the relationship between the chilled water outlet temperature, the opening degree of the refrigerant drain control valve, and the operation and stop of the refrigerant pump; FIG. 3 is a flowchart illustrating the control of the refrigerant pump when the cold water outlet temperature decreases. (1)...High temperature generator, (2)...Low temperature generator,
(3)... Condenser, (4)... Evaporator, (5
)...Absorber, (35>...Water heater, (42P)
)... Refrigerant pump control device.

Claims (1)

[Claims] 1. A generator, a condenser, an evaporator, and an absorber are connected to form a refrigeration cycle, and a refrigerant pump for circulating and distributing refrigerant liquid to the evaporator is connected to the evaporator. The absorption refrigerating machine connected to the evaporator is equipped with a refrigerant pump control device that controls the operation of the refrigerant pump according to the cold water outlet temperature from the evaporator, and the refrigerant pump control device controls the cold water outlet temperature to be below a first predetermined temperature. The refrigerant pump is stopped when the temperature reaches the second predetermined temperature, and the refrigerant pump is operated for a first predetermined time when the chilled water outlet temperature reaches a second predetermined temperature higher than the first predetermined temperature, and The refrigerant pump is stopped when a predetermined time has elapsed, and the refrigerant pump is then operated when the chilled water outlet temperature at the elapse of the second predetermined time is equal to or higher than a third predetermined temperature higher than the second predetermined temperature. absorption refrigerator. 2. Attached to the high temperature side of the refrigeration cycle to extract cold water from the evaporator by connecting the generator, condenser, evaporator, absorber, and refrigerant pump for circulating and distributing refrigerant liquid to the evaporator. In an absorption refrigerating machine configured to take out hot water from a hot water heater, the cold water outlet is The refrigerant pump control device is equipped with a refrigerant pump control device that controls the operation of the refrigerant pump according to the temperature, and this refrigerant pump control device stops the refrigerant pump when the cold water outlet temperature becomes equal to or lower than a first predetermined temperature during hot water main control operation. Then, when the chilled water outlet temperature reaches a second predetermined temperature higher than the first predetermined temperature, the refrigerant pump is operated for a first predetermined time, and when the first predetermined time has elapsed, the refrigerant pump is operated. An absorption refrigerating machine characterized in that the refrigerant pump is operated when the chilled water outlet temperature after a second predetermined time period is equal to or higher than a third predetermined temperature higher than the second predetermined temperature.