Absorption refrigerating apparatus control method

To eliminate great increases in regeneration temperature and pressure and prevent the stoppage of an absorption refrigerating apparatus for safety upon a rise in the temperature of cooling water as well as to prevent crystallization and reduce fuel costs upon a reduction in the temperature of cooling water, the absorption refrigerating apparatus comprises a controller 34 which is constituted such that the opening of a fuel control valve 21 is controlled to a range of 0 to 100% to control the amount of heating in a high-temperature regenerator 1 when the inlet temperature T2 of cooling water is between a variable low-temperature set value and a variable high-temperature set value.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an absorption refrigerating apparatus control 
method for controlling the amount of heating in a regenerator based on the 
outlet temperature of cold water to be taken out of an evaporator. 
2. Background Art 
Japanese Utility Model Laid-open publication No.62-6449, for example, 
discloses an absorption refrigerating apparatus controller in which the 
amount of heating in a regenerator by the outlet temperature of cold water 
in an evaporator is compensated for by the inlet temperature of cold water 
to be supplied to an absorber and the opening of a fuel control valve is 
controlled by raising a set value of the cold water outlet temperature as 
the temperature of cooling water drops from 32.degree. C. to 20.degree. C. 
However, in the above prior art, when the inlet temperature of cooling 
water becomes high and the load on cold water is large, the amount of 
heating in the regenerator becomes large, the regenerating temperature and 
pressure of a refrigerant increases and hence, there is the possibility 
that an absorption refrigerating apparatus may stop operation for safety. 
Further, when the inlet temperature of cooling water becomes low due to a 
drop in the temperature of the outside air, the amount of heating in the 
regenerator increases, the consumption of fuel becomes larger than 
necessary, and the concentration of a concentrated solution becomes high, 
whereby there is the possibility that crystallization may occur. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to eliminate great 
increases in regeneration temperature and pressure and prevent the 
stoppage of an absorption refrigerating apparatus for safety when the 
inlet temperature of cooling water to be supplied to an absorber rises as 
well as to prevent crystallization and reduce fuel consumption when the 
inlet temperature of cooling water drops. 
Further, it is another object of the present invention to make it possible 
to tune an absorption refrigerating apparatus suited to a recipient by 
making variable set values of the inlet temperature of cooling water which 
limits the maximum amount of heating so that it can match the temperature 
of cooling water on the site. It is still another object of the present 
invention to carry out stable operation without stopping the apparatus for 
alarming with a reduced capacity by tuning the refrigerating apparatus 
again when the refrigerating apparatus deteriorates according to secular 
changes and hardly exhibits its capacity. 
To solve the problems of the prior art, the present invention provides an 
absorption refrigerating apparatus control method for controlling the 
amount of heating in a regenerator, which constitutes a refrigerating 
cycle by connecting an absorber, a condenser, an evaporator and the like 
by pipes, based on the outlet temperature of cold water to be taken out of 
the evaporator, wherein the maximum amount of heating is restricted based 
on the inlet temperature of cooling water when the inlet temperature of 
cooling water to be supplied to the absorber is higher than a variable 
high-temperature set value or lower than a variable low-temperature set 
value and the amount of heating is controlled based on the outlet 
temperature of cold water independent of the inlet temperature of cooling 
water until the amount of heating becomes maximal. 
The present invention also provides an absorption refrigerating apparatus 
control method for controlling the opening of a control valve for 
controlling the amount of heating in a regenerator, which constitutes a 
refrigerating cycle by connecting an absorber, a condenser, an evaporator 
and the like by pipes, based on the outlet temperature of cold water to be 
taken out of the evaporator, wherein the maximum opening of the control 
valve is restricted based on the inlet temperature of cooling water when 
the inlet temperature of cooling water to be supplied to the absorber is 
higher than a variable high-temperature set value or lower than a variable 
low-temperature set value, and the opening of the control valve is 
controlled based on the outlet temperature of cold water independent of 
the inlet temperature of cooling water until the opening of the control 
valve becomes maximal. 
The inlet temperature of cooling water to be supplied to the absorber 
changes according to temperature variations. In the case of the control 
method of the first aspect of the present invention, when the inlet 
temperature of cooling water is higher than a high-temperature set value 
or lower than a low-temperature set value which has been preset, the 
amount of heating in a high-temperature regenerator is controlled based on 
the outlet temperature of cold water taken out of the evaporator 
independent of the inlet temperature of cooling water until the amount of 
heating becomes the maximum value which is restricted based on the inlet 
temperature of cooling water. Therefore, a great increase in the load of 
cold water can be handled swiftly. 
When the amount of heating based on the outlet temperature of cold water 
exceeds the maximum value, great increases in regeneration temperature and 
pressure can be prevented because the amount of heating is limited to a 
value lower than the maximum value determined by the inlet temperature of 
cooling water. Thereby the stoppage of an absorption refrigerating 
apparatus for safety can be prevented. 
Since the amount of heating in a high-temperature regenerator is limited, 
the consumption of fuel can be reduced and crystallization can be 
prevented because the concentration of an absorption solution flown from 
the high-temperature regenerator is reduced. 
Further, it is possible to deliver and install a refrigerating apparatus in 
which the high-temperature set value and the low-temperature set value 
have been matched with the temperature of cooling water on the site, and 
stable operation can be effected by tuning the apparatus again without 
stopping it for alarming with a reduced capacity when it hardly exhibits 
its capacity due to its deterioration caused by secular changes. 
In the case of the control method of the second aspect of the present 
invention, when the inlet temperature of cooling water is higher than a 
high-temperature set value or lower than a low-temperature set value, the 
amount of heating is controlled based on the outlet temperature of cold 
water to be taken out of the evaporator independent of the inlet 
temperature of cooling water until the opening of the control valve for 
controlling the amount of heating in the regenerator becomes the maximum 
value which is limited based on the inlet temperature of cooling water. 
Therefore, a great increase in the load of cold water can be handled 
swiftly. 
Since the opening of the control valve is limited to a value smaller than 
the maximum opening determined by the inlet temperature of cooling water 
when the opening of the control valve based on the outlet temperature of 
cold water exceeds the maximum value, great increases in regeneration 
temperature and pressure can be prevented, thereby preventing the stoppage 
of an absorption refrigerating apparatus for safety. 
As the opening of the control valve is restricted, fuel consumption can be 
reduced and crystallization can be prevented because the concentration of 
an absorption solution flown from the high-temperature regenerator is 
reduced. 
It is possible to deliver and install a refrigerating apparatus in which 
the high-temperature set value and the low-temperature set value have been 
matched with the temperature of cooling water on the site, and stable 
operation can be effected by tuning the apparatus again without stopping 
it for alarming with a reduced capacity when it hardly exhibits its 
capacity due to its deterioration caused by secular changes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A preferred embodiment of the present invention according to the present 
invention is described in detail hereinunder with reference to the 
accompanying drawings. 
In FIG. 1, there is shown a double-effect absorption refrigerating 
apparatus which uses water (H.sub.2 O) as a refrigerant and a lithium 
bromide (LiBr) aqueous solution as an absorption agent (absorption 
solution). 
In FIG. 1, reference numeral 1 is a high-temperature regenerator equipped 
with a burner 1B, 2 a low-temperature regenerator, 3 a condenser, 4 an 
evaporator, 5 an absorber, 6 a low-temperature heat exchanger, 7 a 
high-temperature heat exchanger, 8 to 12 absorption solution pipes, 15 an 
absorption solution pump, 16 to 18 refrigerant pipes, 19 a refrigerant 
pump, 20 a gas pipe connected to the gas burner 1B, 21 a fuel control 
valve provided as means for controlling the amount of heating by adjusting 
the flow rate of a gas to be supplied as fuel, and 22 a cold water pipe 
(load pipe), all of which are arranged and connected by pipes as shown in 
FIG. 1. 
Reference numeral 25 is a cooling water pipe along which an absorber heat 
exchanger 26 and a condenser heat exchanger 27 are provided. Reference 
numeral 28 is a cooling tower and 30 a cooling water pump, both of which 
are connected to the cooling water pipe 25 to constitute a cooling 
circuit. 
Reference numeral 31 is temperature detection means (to be referred to as 
"first temperature sensor" hereinafter) for detecting the outlet 
temperature T1 of cold water provided on the outlet side of the evaporator 
4 of the cold water pipe 22, and 32 temperature detection means (to be 
referred to as "second temperature sensor" hereinafter) for detecting the 
inlet temperature T2 of cooling water provided on the cooling water pipe 
25 on the inlet side of the absorber 5. 
Reference numeral 34 is a controller constituted to incorporate a 
microcomputer, which receives temperature signals from the first and 
second temperature sensors 31 and 32 and outputs a desired opening signal 
to the fuel control valve 21. 
During the operation of the above double-effect absorption refrigerating 
apparatus, the refrigerant evaporated in the high-temperature regenerator 
1 enters the condenser 3 through the low-temperature regenerator 2, heat 
exchanges with water running through the condenser heat exchanger 27 to be 
condensed and liquified, and flows into the evaporator 4 through the 
refrigerant pipe 17. Thereafter, the refrigerant solution heat exchanges 
with water in the cold water pipe 22 to be evaporated and thereby the 
water in the cold water pipe 22 is cooled by the heat of evaporation. The 
refrigerant evaporated by the evaporator 4 is absorbed into the absorption 
solution in the absorber 5. 
The absorption solution whose concentration is reduced by absorbing the 
refrigerant is supplied to the high-temperature regenerator 1 through the 
low-temperature heat exchanger 6 and the high-temperature heat exchanger 7 
by the operation of the absorption solution pump 15. The absorption 
solution which has entered the high-temperature regenerator 1 is heated by 
the gas burner 1B, the refrigerant is thereby evaporated, and the 
absorption solution now having an intermediate concentration flows into 
the low-temperature regenerator 2 through the high-temperature heat 
exchanger 7. 
The absorption solution which has entered the low-temperature regenerator 2 
is heated by the refrigerant vapor flown from the high-temperature 
regenerator 1 through the refrigerant pipe 16, whereby the refrigerant is 
evaporated and separated to increase the concentration of the absorption 
solution. The absorption solution now having a high concentration (to be 
referred to as "concentrated solution" hereinafter) is heat exchanged in 
the low-temperature heat exchanger 6 to reduce its temperature, flows into 
the absorber 5 and is sprayed. 
When the inlet temperature T2 of cooling water detected by the second 
temperature sensor 32 is between a variable low-temperature set value, for 
example, 28.degree. C. and a variable high-temperature set value, for 
example, 32.degree. C., the amount of heating in the high-temperature 
regenerator 1 is controlled by adjusting the opening of the fuel control 
valve 21 to a range of 0 to 100%. However, when the inlet temperature T2 
of cooling water exceeds a high temperature set value of 32.degree. C. due 
to a reduction in the radiating capacity of the cooling tower 28 caused by 
a rise in the outside temperature during the summer period, or when the 
inlet temperature T2 of the cooling water falls below a low-temperature 
set value of 28.degree. C. due to an increase in the radiating capacity of 
the cooling tower 28 caused by a reduction in the outside temperature 
during the winter period, as shown by a solid line in FIG. 2, the 
controller 34 is constituted such that the maximum value of the amount of 
heating in the high-temperature regenerator 1 is restricted by limiting 
the maximum opening Y of the fuel control valve 21 to a small value. 
In other words, the controller 34 operates such that, when the inlet 
temperature T2 of cooling water is between a low-temperature set value of 
28.degree. C. and a high-temperature set value of 32.degree. C., the 
maximum opening Y of the fuel control valve 21 is controlled to 100%, when 
the inlet temperature T2 of cooling water is higher than a 
high-temperature set value of 32.degree. C., the maximum opening Y of the 
fuel control valve 21 is reduced by 10% each time the inlet temperature T2 
of cooling water is increased by 1.degree. C., and when the inlet 
temperature T2 of cooling water is lower than a low-temperature set value 
of 28.degree. C., the maximum opening Y of the fuel control valve 21 is 
reduced by 10/9% each time the inlet temperature T2 of cooling water is 
reduced by 1.degree. C. 
The actual opening control of the fuel control valve 21 is carried out 
based on the outlet temperature T1 of cold water detected by the first 
temperature sensor 31 as shown in FIG. 3 and FIG. 4, for example. 
That is, since the opening of the fuel control valve 21 is controlled by 
proportional control based on the outlet temperature T1 of cold water 
until the outlet temperature T1 of cold water, rises to 7.degree. C. when 
the inlet temperature T2 of cooling water is 37.degree. C., for example, 
until the outlet temperature T1 of cold water rises to 7.4.degree. C. when 
the inlet temperature T2 of cooling water is 35.degree. C., for example, 
until the outlet temperature T1 of cold water rises to 7.6.degree. C. when 
the inlet temperature T2 of cooling water is 10.degree. C., for example, 
and until the outlet temperature T1 of cold water rises to 7.8.degree. C. 
when the inlet temperature T2 of cooling water is 19.degree. C., for 
example, an increase in the load of cold water can be handled swiftly. 
As described above, as the inlet temperature T2 of cooling water rises more 
beyond a high-temperature set value, the amount of heating in the 
high-temperature regenerator 1 is restricted by limiting the maximum 
opening Y of the fuel control valve 21 to a smaller value. Therefore, even 
if the inlet temperature T2 of cooling water becomes high, great increases 
in regeneration temperature and pressure can be eliminated, thereby 
preventing stoppage of an absorption refrigerating apparatus for safety. 
Since the maximum opening Y of the fuel control valve 21 is restricted more 
as the inlet temperature T2 of cooling water falls more below a 
low-temperature set value, for example, the maximum opening is restricted 
to 90% when the inlet temperature T2 of cooling water is 19.degree. C. and 
to 80% when it is 10.degree. C., the fuel consumption of the gas burner 1B 
is reduced when the inlet temperature T2 of cooling water becomes low. 
Since it is possible to reduce the concentration of the absorption solution 
flown from the high-temperature regenerator 1 by controlling the amount of 
heating to a small value, crystallization in the low-temperature heat 
exchanger 6 can be prevented by reducing the concentration of the 
absorption solution flown from the low-temperature regenerator 2. 
In addition, since the controller 34 comprises a switch for changing the 
high-temperature set value (to be referred to as "first changing switch" 
hereinafter) 34S1 and a switch for changing the low-temperature set value 
(to be referred to as "second changing switch" hereinafter) 34S2, it is 
possible to change both the high-temperature set value and the 
low-temperature set value by operating the first changing switch 34S1 and 
the second changing switch 34S2. 
That is, the first changing switch 34S1 has an up switch 35 for increasing 
the set value and a down switch 36 for reducing the set value. Like the 
first changing switch 34S1, the second changing switch 34S2 has an up 
switch 37 and a down switch 38. 
The first changing switch 34S1 and the second changing switch 34S2 are not 
limited to the above constitutions and may be dial type changing switches. 
For instance, when a refrigerating apparatus is installed in an area where 
the inlet temperature T2 of cooling water becomes low, as shown by a 
broken line in FIG. 2, it is possible to carry out the operation control 
of the refrigerating apparatus that has been matched with the temperature 
of actually used cooling water by changing the high-temperature set value 
from 32.degree. C. to 30.degree. C. and the low-temperature set value from 
28.degree. C. to 26.degree. C., for example. 
Even when the refrigerating capacity of an apparatus deteriorates due to 
secular changes, it is possible to continue stable operation by resetting 
a high-temperature set value and a low-temperature set value of the inlet 
temperature T2 of cooling water without stopping the operation of the 
apparatus for alarming while a reduced capacity is permitted. 
It is to be distinctly understood that the invention is not limited to the 
above embodiment but may be otherwise variously embodied without departing 
from the spirit and scope thereof. 
For example, in the case that a driving heat source is vapor, the same 
function and effect can be obtained by controlling the amount of heating 
in the regenerator by controlling a vapor control valve in the same manner 
as the above fuel control valve. 
In a single-effect refrigerating apparatus in which a driving heat source 
is low-temperature hot water, the same function and effect can be obtained 
by controlling the amount of heating in the regenerator by controlling a 
hot water control valve in the same manner as the above fuel control 
valve. 
The present invention is a control method for an absorption refrigerating 
apparatus constituted above. The maximum value of the amount of heating in 
the regenerator is controlled based on the inlet temperature of cooling 
water when the inlet temperature of cooling water to be supplied to the 
absorber is higher than a variable high-temperature set value or lower 
than a variable low-temperature set value, and the amount of heating in 
the regenerator is controlled based on the outlet temperature of cold 
water to be taken out of the evaporator independent of the inlet 
temperature of cooling water until the amount of heating in the 
regenerator becomes maximal. Therefore, great increases in regeneration 
temperature and regeneration pressure when the inlet temperature of 
cooling water rises are prevented, thereby avoiding the stoppage of the 
absorption refrigerating apparatus for safety due to a rise in the 
temperature of cooling water. 
When the inlet temperature of cooling water drops, the amount of heating in 
the regenerator is reduced and accordingly, the concentration of the 
absorption solution flown from the regenerator is lowered, thereby 
preventing crystallization. Due to a reduction in fuel consumption, 
operation costs can be reduced. 
Since the amount of heating in the regenerator is controlled based on the 
outlet temperature of cold water until the amount of heating in the 
regenerator becomes maximal, a change in the load of cold water can be 
handled swiftly. 
In addition, since it is possible to deliver and install an apparatus in 
which the high-temperature set value and low-temperature set value of the 
inlet temperature of cooling water have been matched with the temperature 
of cooling water on the site and to tune the apparatus again when it 
hardly exhibits its capacity due to its deterioration caused by secular 
changes, stable operation can be effected without stopping the apparatus 
for alarming with a reduced capacity. 
Since the present invention is a method for controlling the maximum opening 
of the fuel control valve provided in the regenerator based on the inlet 
temperature of cooling water when the inlet temperature of cooling water 
to be supplied to the absorber is higher than a variable high-temperature 
set value or lower than a variable low-temperature set value and for 
controlling the opening of the fuel control valve based on the outlet 
temperature of cold water to be taken out of the evaporator independent of 
the inlet temperature of cooling water until the opening of the fuel 
control valve becomes maximal, it is possible to prevent the stoppage of a 
refrigerating apparatus for safety due to great increases in the 
regeneration temperature and pressure of the refrigerant by reducing the 
amount of heating in the regenerator when the inlet temperature of cooling 
water rises or falls. 
Also in this control method, the amount of heating in the regenerator is 
reduced, thereby making it possible to prevent the production of crystals 
and cut the operation costs of an absorption refrigerating apparatus. 
Further, a change in the load of cold water can be handled swiftly. 
Since it is possible to deliver and install an apparatus in which a 
high-temperature set value and a low-temperature set value of the inlet 
temperature of cooling water have been matched with the temperature of 
cooling water on the site and tune the apparatus again when it hardly 
exhibits its capacity due to its deterioration caused by secular changes, 
stable operation can be effected without stopping the apparatus for 
alarming with a reduced capacity.