Apparatus for cooling brine

An apparatus for cooling brine comprising a plurality of refrigerating units connected to a slow-current tank for brine in such a manner said refirgerating units are associated with successive portions of brine in said slow-current tank from the downstream side to the upstream side of said tank, one by one. The number of said refrigerating units taking part in the cooling work is increased and decreased in accordance with the temperature of said brine in said slow-current tank. The connection of said refrigerating units is selectively switched from series to parallel and vice versa with one another, with respect to the brine flow in said slow-current tank. Said means for switching the connection of said refrigerating units from series to parallel and vice versa are constituted by fluid element type shunting devices.

The present invention relates to an apparatus for cooling brine having a 
plurality of refrigerating units. 
In the field of deep-sea fishery, a large amount of brine of a temperature 
between -20.degree. and -40.degree. C. is used for the purpose of cold 
storage of fishes. Usually, for cooling the large amount of brine to such 
a low temperature, a plurality of refrigerating units are used, each of 
which having a compressor, condenser, expansion valve and evaporator. 
These refrigerating units are operated in such a manner that the 
compressors bear equal share of load, so that it is difficult to control 
the brine temperature when the load fluctuates largely. 
In order to overcome above described problem, the present invention 
provides in its one aspect an apparatus for cooling brine having a 
plurality of refrigerating units, wherein the plurality of refrigerating 
units are arranged in a slow-current tank of the brine in series with 
respect to the direction of the flow of the brine, the number of 
refrigerating units actually used and the cooling power of each 
refrigerating unit are increased or decreased by means of a controller 
associated with a temperature detector provided in the slow-current tank, 
in accordance with the fluctuation of the load, so as to cope with the 
load fluctuation over a wider range. 
Although the above stated cooling apparatus can sustain a large load 
fluctuation, there still remains a problem unsolved. Namely, since the 
temperature of the brine in the slow-current tank varies such that it is 
relatively high at the brine-inlet side of the tank and relatively low at 
the brine-outlet side, the refrigerating units which are disposed in 
series with respect to the flow of brine are subjected to different 
thermal conditions. More specifically, the refrigerating units located at 
the downstream side have to take colder brine than those which are located 
at the upstream side. This means that the refrigerating units associated 
with the brine residing at the downstream side of the tank are subjected 
to smaller thermal loads, and the efficiencies in their evaporators are 
inconveniently deteriorated. 
To avoid this inconvenience, according to another aspect of the invention, 
the aforementioned cooling apparatus in accordance with the first aspect 
of the invention is further improved such that at least two refrigerating 
units are connected in parallel with each other at their brine-intake 
side, so that the cooling power of the apparatus is increased as a whole. 
According to still another aspect of the invention, the cooling apparatus 
as stated in connection with the second aspect is further improved to have 
means for switching the manner of mutual connection of the regrigerating 
units with respect to the flow of brine in the slow-current tank from 
series to parallel and vice versa, the switching means being constituted 
by a fluid-element type shunting device so as to render the construction 
of the apparatus simple, as compared with apparatus having switching means 
constituted by electromagnet valves, electrically driven valves or the 
like.

Referring at first to FIG. 1, the brine to be cooled is adapted to flow 
gently through a slow-current tank 1, from inlet 2 to the outlet 3. A 
plurality of refrigerating units 4.sub.1, 4.sub.2 . . . 4.sub.n are 
associated with the slow-current tank 1 in the manner described later. 
Each of the refrigerating units consists of a compressor 5, condenser 6, 
expansion valve 7 and an evaporator 8, as shown in FIG. 2. 
The evaporator of each refrigerating unit is connected to the slow-current 
tank 1 through a brine suction pipe 9 having a brine pump 11 and a brine 
discharge pipe 10, so that a heat exchange may be performed between the 
coolant circulated through the evaporator 8 and the brine taken into the 
evaporator by the brine pump 11. 
The refrigerating units 4.sub.1, 4.sub.2, . . . 4.sub.n are arranged in 
series with respect to the flow of the brine, i.e., in such a manner that 
the unit 4.sub.1 is positioned at the downstream side of the tank 1 and 
the unit 4.sub.n is at the upstream side of the tank 1 as viewed in the 
direction of the flow of brine through the slow-current tank 1. 
The refrigerating units 4.sub.1, 4.sub.2 . . . 4.sub.n, as well as the 
brine pumps 11.sub.1, 11.sub.2 . . . 11.sub.n are connected to a 
temperature controller 12 which is associated with a temperature detector 
13 inserted into the slow-current tank 1 at the brine outlet side 3 of the 
latter 1. The temperature controller 12 is adapted to function 
electrically, in accordance with a deviation of the detected temperature 
of the brine from a predetermined temperature set in the temperature 
controller 12, so as to put the combinations of the refrigerating unit and 
the brine pump into operation, in such a manner that at first the 
combination of the refrigerating unit 4.sub.1 and the brine pump 11.sub.1 
is started and then the number of combinations under operation is 
gradually increased until the last combination of the refrigerating unit 
4.sub.n and the brine pump 11.sub.n comes into operation, depending on the 
magnitude of the above-mentioned deviation of the temperature. 
As mentioned before, the refrigerating units 4.sub.1, 4.sub.2 . . . 4.sub.n 
are arranged in series with respect to the flow of the brine, from the 
downstream to the upstream sides in the mentioned order, i.e., in 
accordance with the order in which these units are brought into operation. 
More specifically, the brine suction pipe 9.sub.1, brine discharge pipe 
10.sub.1, the brine suction pipe 9.sub.2, the brine discharge pipe 
10.sub.2 . . . the brine suction pipe 9.sub.n and the brine discharge pipe 
10.sub.n are arranged in accordance with the order in which the associated 
refrigerating units are brought into operation, from the downstream to the 
upstream sides of the slow-current tank 1, at a suitable pitch. 
In operation, as the temperature of the brine flowing into the slow-current 
tank 1 through the brine-inlet side 2 comes higher than the temperature 
set at the controller 12, the first combination of the refrigerating unit 
and the brine pump, i.e., the refrigerating unit 4.sub.1 and the brine 
pump 11.sub.1, is turned on. The cooling power of the refrigerating unit 
4.sub.1 is increased in accordance with the increase in the thermal load, 
so as to keep the temperature of brine flowing out of the slow-current 
tank 1 through the brine-outlet side end 3 constant. 
A further increase of the temperature of brine flowing through the brine 
inlet side 2 causes the refrigerating unit 4.sub.1 to function to negate 
the temperature deviation, and, finally, the refrigerating unit 4.sub.1 
comes to be obliged to perform its full-load operation. 
As the temperature of the brine further gets higher, or the flow rate of 
the brine through the inlet side 2 is increased, the controller 12 acts to 
start the second combination of the refrigerating unit and the brine pump, 
i.e., the refrigerating unit 4.sub.2 and the brine pump 11.sub.2. 
Therefore, the brine discharged from the brine discharge pipe 10.sub.1 of 
the first unit 4.sub.1 is sucked into the second unit 4.sub.2 which is 
situated at the upstream side of the first unit 4.sub.1. The brine cooled 
by the second refrigerating unit 4.sub.2 is discharged to a portion in the 
slow-current tank 1 by the upstream side of the suction pipe 9.sub.1 of 
the first refrigerating unit but downstream side of the suction pipe 
9.sub.2 of the second refrigerating unit 4.sub.2, so that the first 
refrigerating unit 4.sub.1 may take the brine which has been cooled 
already by the second refrigerating unit 4.sub.2. 
Referring to another embodiment as shown in FIG. 3, the slow-current tank 1 
for the brine is devided into a plurality of sections 14.sub.1, 14.sub.2 . 
. . 14.sub.n. These sections are connected in series through passages 15, 
such that the first section 14.sub.1 is located at the outlet side, while 
the final section 14.sub.n is located at the inlet side, in connection 
with the brine flow. Thus, the brine outlet side end of the first section 
14.sub.1 forms the brine outlet port 3, while the brine inlet side end of 
the n th section 14 constitutes the brine inlet port 2 of the slow-current 
tank. 
Brine suction pipes 9.sub.1, 9.sub.2 . . . 9.sub.n leading from upstream 
side portions of respective sections 14.sub.1, 14.sub.2 . . . 14.sub.n are 
connected, through respective brine pumps 11.sub.1, 11.sub.2 . . . 
11.sub.n, to corresponding refrigerating units 4.sub.1, 4.sub.2 . . . 
4.sub.n. Brine discharge pipes 10.sub.1, 10.sub.2 . . . 10.sub.n leading 
from respective units are connected to the downstream side portions of 
respective sections 14.sub.1, 14.sub.2 . . . 14.sub.n. A temperature 
detector or a sensor 13 is inserted into the outlet-side end section 
14.sub.1, near the brine outlet port 3, and is connected to temperature 
controller 12. This arrangement is substantially same as that of the 
embodiment of FIG. 1. 
The cooling apparatus of this second embodiment functions almost in the 
same manner as the first embodiment. 
However, since the slow-current flow tank is divided into sections 
14.sub.1, 14.sub.2 . . . 14.sub.n corresponding to the refrigerating units 
4.sub.1, 4.sub.2 . . . 4.sub.n, with the brine suction and discharge pipes 
9.sub.1, 9.sub.2 . . . 9.sub.n and 10.sub.1, 10.sub.2 . . . 10.sub.n of 
respective units connected to the corresponding slow-current tank 
sections, the refrigerating units are free from the influence of other 
refrigerating units. Consequently, the refrigerating units 4.sub.1, 
4.sub.2 . . . 4.sub.n are stably controlled in accordance with orders 
given by the controller 12. 
Referring now to still another embodiment as shown in FIG. 4, this cooling 
apparatus has a construction substantially same as that of the embodiment 
of FIG. 3, excepting that the brine discharge pipes 10.sub.n . . . 
10.sub.2 from respective refrigerating units 4.sub.n . . . 4.sub.2 lead to 
the neighbouring downstream side tank sections 14.sub.n-1, . . . 14.sub.1. 
This apparatus functions in the similar manner with the embodiment of FIG. 
3. However, this embodiment is characterized in that the temperature 
differential between the inlet and outlet side ends in each tank section 
14.sub.1, 14.sub.2 . . . 14.sub.n becomes large as it gets closer to the 
outlet side end of the tank. 
In the foregoing embodiments, the refrigerating units 4.sub.1, 4.sub.2 . . 
. 4.sub.n and associated brine pumps 11.sub.1, 11.sub.2 . . . 11.sub.n are 
arranged in the mentioned order from the downstream to the upstream sides 
of the slow-current tank, it is to be noted here that the sequence or 
order in which the refrigerating units 4.sub.1, 4.sub.2 . . . 4.sub.n are 
brought into operation can be optionally changed by the switching in the 
controller 12. It will be seen that concentration of work to specific 
refrigerating unit can be avoided, and the operation times of all units 
are equalized, by periodically switching the operation order of the 
refrigerating units. 
Hereinafter, an explanation will be made with specific reference to FIGS. 5 
to 8, as to an embodiment which is arranged to allow a parallel connection 
of the refrigerating units to each other, with respect to the slow-current 
tank of the brine. 
In FIG. 5, a brine slow-current tank 1 is shown to be divided by throttling 
walls 16, into a plurality of sections 14.sub.1, 14.sub.2, 14.sub.3 which 
are connected in series through a communication passage 15. A plurality of 
refrigerating units 4.sub.1, 4.sub.2, 4.sub.3 are associated with and 
connected to respective one of the sections 14.sub.1, 14.sub.2, 14.sub.3. 
Brine suction pipes 9.sub.1 and 9.sub.2 are connected to each other 
through a connection pipe 19 having a connection valve 17, while the brine 
suction pipes 9.sub.2 and 9.sub.3 are also connected to each other, 
through a connection pipe 20 having a connection valve 18. The brine 
suction pipes 9.sub.1 and 9.sub.2 are provided with respective suction 
valves 21 and 22 at their portions upstream sides of points at which they 
join the connecting pipes 19, 20. These connection valves 17, 18 and 
suction valves 21, 22 are operatively connected to the controller 12. The 
controller 12 is adapted to optionally close the connection valves 17, 18 
and to open the suction valves 21, 22 to put the refrigerating units 
4.sub.1, 4.sub.2, 4.sub.3 in series to each other, and to open the 
connection valve 17, 18 and close the suction valves 21, 22 for putting 
the units in parallel with one another with respect to the slow-current 
tank. 
This cooling apparatus functions in the following manner. 
A sensor 13 provided at the outlet side of the slow-current tank 1 is 
adapted to input a signal to the controller 12. Supposing that the 
detected temperature deviates from the set temperature of the brine to the 
higher side, the combination of the brine pump 11.sub.1 and the 
refrigerating units 4.sub.1 is started to commence the cooling of the 
brine. It is assumed here that the suction valves 21, 22 are opened and 
the connection valves 17, 18 are closed. The capacity of the compressor is 
further increased, when the deviation of the brine temperature is still in 
the higher side. It will be seen that the control of the cooling rate is 
effected through varying the capacity of the compressor, since the brine 
pump 11.sub.1 is electrically driven at a fixed speed to intake the 
correspondingly fixed rate of brine. Thus, the refrigerating unit 4.sub.1 
comes to perform a full-load operation. If the signal demanding the 
further increase of the cooling capacity is still issued, the 
refrigerating unit 4.sub.2 located at the upstream side of the working 
unit 4.sub.1 is turned on, so that the refrigerating units 4.sub.1 and 
4.sub.2 may exert a total output to cope with the thermal load. In this 
condition, the refrigerating units 4.sub.1 and 4.sub.2 are operated 
keeping a serial connection to each other, with respect to the brine 
slow-current tank 1, since the brine suction pipe 9.sub.2 is located at 
the upstream side of the refrigerating unit 4.sub.1. 
When this serial operation of the refrigerating unit cannot sustain the 
thermal load, even by the full-load operation of the refrigerating units 
4.sub.1 and 4.sub.2, the connection valve 17 which has been closed is 
opened, whereas the suction valve 21 which has been opened is closed. 
Then, the brine pump 11.sub.1 of the first refrigerating unit 4.sub.1 
comes to suck the brine in the slow-current chamber, through the suction 
pipe 9.sub.2, suction valve 22 and the connection valve 17. Consequently, 
the refrigerating units 4.sub.1 and 4.sub.2 are brought into parallel with 
each other at their brine-inlet sides, with respect to the slow-current 
tank 1. Since the refrigerating unit comes to suck the brine of a higher 
temperature, the total cooling capacity is much increased by this parallel 
connection, than in the serial connection of the refrigerating units. 
When the refrigerating unit 4.sub.3 is started, this is put in series to 
the parallel connection of the units 4.sub.1 and 4.sub.2. Then, as the new 
unit 4.sub.3 comes to perform its full-load operation, three units are 
connected in parallel with each other, by closing the suction valves 21, 
22 and opening the connection valves 17, 18, with respect to the 
slow-current tank 1, by a common use of the suction pipe 9.sub.3. In the 
described embodiment, the switching of the valves 21, 22 and 17, 18 are 
effected at each time the newly joined refrigerating unit comes to perform 
its full-load operation. However, it is possible to control in such a 
manner that the valves are sequentially operated after putting the three 
units in series, so as to progressively establish the parallel connection. 
More specifically, after putting the three units in series, two of them 
are put in parallel with each other, and then, the remainder one unit is 
put in parallel with the two parallel units. However, such a control is 
not recommended, although it is simple to perform, from the view point of 
cooling effect. 
The above stated manner of operation of this embodiment is well summarized 
in the following table 1. 
In the embodiment of FIG. 5, the suction valves 21, 22 and connection 
valves 17, 18 may be combined with each other, such that the suction valve 
21 and the connection valve 17 are combined to constitute a three-way 
valve, while the suction valve 22 and the connection valve 18 are combined 
to form another three-way valve. 
Referring now to FIGS. 6 through 8 showing still another embodiment, the 
slow-current tank 1 for the brine is sectioned by a partition wall 23 
which extends in parallel with the direction of brine flow and partition 
walls 24, 25 which are perpendicular to the direction of the brine flow. 
Switchable doors 26, 27 are provided at point where the partition wall 23 
merges the partition walls 24, 25 respectively. Passages 28, 29, 30 and 31 
are formed in the partition walls 23, 24, 25 so as to be opened and closed 
in accordance with the rotation of the switchable doors 26, 27. 
The brine suction pipes 9.sub.1, 9.sub.2, 9.sub.3 and discharge pipes 
10.sub.1, 10.sub.2, 10.sub.3 are connected to the slow-current tank 1 at 
opposite sides of the partition wall 23. Deflector plates 32.sub.1, 
32.sub.2, 32.sub.3 are provided to confront one sides of respective 
openings of the discharge pipes 10.sub.1, 10.sub.2, 10.sub.3. 
Table 1 
__________________________________________________________________________ 
No. 1 Unit 
No. 2 Unit No. 3 Unit 
Comp- 
Pump 
Comp- valve 
Valve Comp- 
Valve 
Valve 
Pump 11.sub.1 
ressor 
11.sub.2 
ressor 
17 21 Pump 11.sub.3 
ressor 
18 22 Operation Mode 
__________________________________________________________________________ 
0 0 0 0 close 
open 
0 0 close 
open 
stop 
start 
start 
" " " " " " " " No. 1 Unit start 
ca- 
" pacity 
" " " " " " " " Capacity Increases 
in- 
crease 
" Full 
" " " " " " " " No. 1 Unit full load 
load 
" " start 
start 
" " " " " " No. 2 Unit start 
Capaci- 
" " " ty in- 
" " " " " " Nos. 1, 2 Units Series 
crease 
" " " Full " " " " " " Nos. 1, 2 Units Full load 
load 
" " " " open 
" " " " " Series to Parallel 
" " " " " close 
" " " " Nos. 1, 2 Parallel 
" " " " " " start 
start 
" " No. 3 Unit start 
Ca- 
" " " " " " " pacity 
" " No. 3 series to 
increase parallel Nos. 1 and 2 
" " " " " " " Full " " Nos. 1,2,3 Full Load 
load 
" " " " " " " " open 
" No. 3 series to para. 
" " " " " " " " " close 
Nos. 1,2,3 Parallel 
" " " " " " " " " open 
Capacity Decrease 
__________________________________________________________________________ 
Other portions than described above are constructed in the similar manner 
with the embodiment of FIG. 5. 
In operation, referring at first to FIG. 6 which shows a state in which the 
refrigerating unit 4.sub.1 is solely operated, the switchable doors 26, 27 
are closing the passages 29 and 31. FIG. 7 shows the switchable doors 
switched for allowing the parallel operation of the refrigerating units 
4.sub.1 and 4.sub.2, after the unit 4.sub.2 has taken part in the work and 
has reached its full-load condition. FIG. 8 shows the condition of 
parallel connection of the refrigerating units 4.sub.1, 4.sub.2, 4.sub.3, 
working at their maximum power, after the third unit 4.sub.3 has taken 
part in the work in series to the parallelly connected two units 4.sub.1, 
4.sub.2 and then reached its full-load operating condition. It will be 
seen that the third unit 4.sub.3 is switched from series to parallel 
condition by closing the passage 30 by the switchable door 27. 
FIGS. 9 and 10 show still another embodiment, in which a fluid-element type 
shunting device is used for switching the connection of refrigerating 
units from series to parallel and vice versa, with respect to the brine 
slow-current tank. 
In the construction as shown in FIG. 9, the slow-current tank 1, 
refrigerating units 4.sub.1, 4.sub.2, 4.sub.3, brine pumps 11.sub.1, 
11.sub.2, 11.sub.3, and the temperature controller connected to the units 
and pumps are same as the embodiment of FIG. 5. 
Fluid-element type shunting devices 33, 34 are provided in the brine 
discharge pipes 10.sub.2, 10.sub.3 of the refrigerating units 4.sub.2, 
4.sub.3, respectively. 
As shown in FIG. 10, the fluid-element type shunting devices 33, 34 are 
constituted, respectively, by inlet flow pipes 35, 36 adapted to be 
connected to the discharge side of respective refrigerating units 4.sub.2, 
4.sub.3, shunting pipes 37, 38, 39, 40 adapted to direct the flow of brine 
from the inlet flow pipes 35, 36 in either one of two directions, and 
controlling pipes 41, 42, 43, 44 adapted to restrict the flow of brine to 
one of the two directions. The arrangement is such that the pressure in 
the chambers 45, 46 overcomes that in the chambers 47, 48, thereby to 
direct the brine flow through the inlet flow pipes 35, 36 to the left-hand 
side shunting pipes 39, 40, as viewed on the drawings, when the control 
pipes 41, 42 are opened to atmosphere and control pipes 43, 44 are closed. 
To the contrary, when the controlling pipes 41, 42 are closed and the 
other two 43, 44 are opened, the flow of brine is directed to the 
right-hand side shunting pipes 37, 38. 
One 39, 40 of the shunting pipes of each fluid-element type shunting device 
33, 34 is connected to each section 14.sub.2, 14.sub.3 of the tank, 
through the discharge pipe 10.sub.2, 10.sub.3, while the other shunting 
pipe 37, 38 in each shunting device is connected to the slow-current tank 
1 to open at portions of the latter close to the outlet port 3, through 
outlet pipes 49, 50. The discharge pipe 10.sub.1 of the refrigerating unit 
4.sub.1 opens also in the vicinity of the outlet port 3. 
Between the area at which the discharge pipes 49, 50, 10.sub.1 open and the 
outlet port 3, disposed is the temperatue senser 13 operatively connected 
to the temperature controller 12. The output circuits 51, 52, 53 of the 
controller 12 are connected to the compressors of the units 4.sub.1, 
4.sub.2, 4.sub.3 to control the capacities of the latter. The output of 
the controller 12 is connected also to the controlling pipes 41, 42, 43, 
44 of the fluid-element type shunting devices 33, 34. 
In operation, as the thermal load of the brine increases from the condition 
of FIG. 9, the resultant temperature rise of the brine is sensed by the 
temperature sensor 13, and is put into comparison with the set temperature 
in the controller 12. The first refrigerating unit 4.sub.1 and its 
associated brine pump 11.sub.1 are started in accordance with the 
temperature deviation, and the capacity of the compressor of the unit is 
gradually increased. When the full-load operation of the unit 4.sub.1 
cannot sustain the thermal load, the second unit 4.sub.2 and its 
associated brine pump 11.sub.2 are started, and the capacity of the 
compressor is gradually increased. In this state, since the controlling 
pipe 43 of the fluid-element type shunting device 33 is closed, while the 
other controlling pipe 41 is opened to atmosphere, the brine cooled by the 
second unit 4.sub.2 is discharged into the discharge pipe 10.sub.2 through 
the shunting pipe 39. Thus, in this condition, the first and the second 
refrigerating units 4.sub.1 and 4.sub.2 are in series relation to each 
other, through the slow-current tank 1. 
A further increase of the thermal load causes the controlling pipe 43 to 
open to atmosphere and the controlling pipe 41 is closed. Consequently, 
the brine flowing through the inlet flow pipe 35 is discharged into the 
downstream-side end chamber 14.sub.1, through the shunting pipe 37 and the 
discharge pipe 49. It will be seen that the refrigerating units 4.sub.1 
and 4.sub.2 are now in parallel relation to each other to perform a larger 
cooling effort than could be obtained by series connection. This increase 
of cooling effort is attributed to the fact that the temperature 
differential in the heat exchanger (not shown) of the refrigerating unit 
4.sub.2 is increased to enhance the cooling capacity. 
It is impossible to effectively operate the refrigerating unit 
corresponding to the increasing thermal load, by solely switching the 
connection of the brine flow from series to parallel by means of the fluid 
element-type shunting device. Thus, it is necessary to increase the output 
of the refrigerating unit 4.sub.2, to an extent as high as that of the 
first unit 4.sub.1. 
Therefore, a discontinuity of control is caused at the time of switching 
from series to parallel. 
In general, since the first unit 4.sub.1 has reached its full-load 
condition and the second unit 4.sub.2 has also reached its full-load 
condition, but still cannot sustain the thermal load, at the time of 
switching from series to parallel. Therefore, the discontinuity of control 
is not so serious. 
However, when a more precise control is required, the discontinuity of the 
control can be negated by simultaneously controlling the compressors of 
the refrigerating units 4.sub.1, 4.sub.2 in such a manner that the 
capacity of the unit 4.sub.1 is decreased, while the capacity of the unit 
4.sub.2 is increased, to obtain a smooth transient characteristic at the 
time of switching from series to parallel. 
It will be clear to those skilled in the art that the fluid-element type 
shunting device 34 functions at first to connect the third refrigerating 
unit 4.sub.3 to the parallel units 4.sub.1 and 4.sub.2 and, then, in 
accordance with the increase of the load, functions to switch to connect 
the third unit 4.sub.3 in parallel with the parallel units, thereby to 
afford the full-power operation of the cooling apparatus. 
The switching from series to parallel may be effected by controlling the 
opening and closing of the controlling pipes 41, 42, 43, 44 of the 
fluid-element type shunting devices 33, 34 by a pumping pressure caused by 
the starting of the brine pumps 11.sub.1 or 11.sub.2 of the previous 
stage, insteadly of relying upon the direct control of the shunting 
devices by the temperature controller 12. 
At the same time, it is possible to operate the apparatus in such a manner 
that the first, second and the third units 4.sub.1, 4.sub.2 and 4.sub.3 
are successively put into series operation in the mentioned order and then 
successively changed into parallel operation, one by one. 
The flow circuit of the controlling pipe can be simplified by employing a 
mono-stable type fluid-element shunting device having only one controlling 
pipe, in place of the described bi-stable fluid-element type shunting 
device 33, 34 which is controlled by a pair of controlling pipes 41, 42; 
43, 44. 
The described cooling apparatus can be used for cooling liquids other than 
the mentioned brine. 
As has been described, according to the invention, there is provided a 
cooling apparatus in which a plurality of refrigerating units are disposed 
for communication with successive portions of a slow-current tank in 
order, from downstream side to the upstream side, the units being operated 
in series with respect to the brine flow in the slow-current tank, the 
number of units taking part in the work being increased and decreased as 
the thermal load is increased and decreased. 
Therefore, the apparatus of the invention can cope with a larger range of 
load fluctuation, than the conventional apparatus in which a plurality of 
refrigerating units are simultaneously operated at partial loads. 
In addition, by arranging such that the plurality of refrigerating units 
are connected in parallel one another with equivalent shares of load 
simultaneously, at the time of changing the number of units actually used, 
the variation of load on the units is fairly avoided to prevent the 
cooling capacity from being lowered by a too small-load application to a 
specific unit. 
At the same time, the fluid-element type shunting device used for switching 
the connection of the units from series to parallel and vice versa can be 
operated with an extremely small energy, since it has no sliding part as 
involved in the conventional switching means such as electromagnet valve 
and electrically driven valve, and, therefore, ensures a high speed of 
response, without the fear of water-hammering, contributing greatly to 
make the switching operation smooth and safe.