JPH06159741A - Heat-medium transporting control method and apparatus for district cooling/heating - Google Patents

Abstract

PURPOSE:To enable a low load pumping power in particular to be reduced by a method wherein when a heat-medium is transferred from a plurality of parallel connected heat source plants, one or more of pumps of each of the heat source plants can be driven in variable speed and the number of rotations of the pump and the like can be controlled according to the load. CONSTITUTION:A cold water pumping system is provided with a plurality of (n) sets of parallel connected heat source plants A having a flow rate controller 4c installed in a bypassing pipe passage for bypassing a freezer 1 in addition to the freezer 1 and a cold water pump 2 and the like. Cold water generated at the heat source plants A is supplied to a cooling or heating target region B where the number of (m) of the receiving facilities 10 are arranged in parallel. In this case, one cold water pump 21 is driven by an inverter motor 5 and the other cold water pump is driven by an ordinary induction motor. Then, under a high load operation time, an appropriate number of pumps 2 are operated at a specified speed in such a way that a utilization differential pressure of a receiving facility 10 placed near an end of a regional pipe B1 is kept constant and in turn under a low load state, only the cold water pump 21 is operated at a variable speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plurality of heat medium receiving facilities (which are connected to a subsequent air conditioner or the like) provided in a region,
District heating and cooling (also called district heat supply) that circulates (supply and recover) heat medium (cold water, hot water, steam, etc.) from a heat source plant that has multiple pumps and heat source equipment (refrigerator, heat pump, heat exchanger, etc.) ) Is related to the transfer of the heat medium.

[0002]

2. Description of the Related Art In recent years, in some urban areas, cold water, hot water, steam, etc. are centrally supplied to a plurality of buildings from one location to improve urban functions and effectively use energy. A district heating and cooling system is provided.

Generally, in a district heating and cooling system, a refrigerator, a heat pump, a heat exchanger, etc., which are heat source devices, are incorporated in a heat source plant together with a pump for a heat medium, and these are connected to a receiving facility in each building. It is configured to be connected to piping. As the circulation system of the heat medium, there are an open system in which a part is connected to a heat storage tank or the like and the heat medium is once opened to the atmosphere, and a closed system in which there is no open portion to the atmosphere. However, in the case of an open system, pump power is increased because it is necessary to lift the heat medium from atmospheric pressure, and the heat medium contains a large amount of oxygen in contact with air in the atmosphere-opened portion, causing corrosion in pipes and the like. Since it is likely to occur, a closed system without such inconvenience is often adopted.

In the heat source plant, a plurality of heat source devices and a plurality of pumps are usually installed in parallel. This is because it is difficult to meet the demand for heat medium in the area with only one unit, but mainly because it is easy to respond to seasonal demand changes. That is, the maximum heat load of the district heating and cooling system occurs in summer or winter, which determines the facility capacity of the heat source plant, but the heat load (demand) is low during the middle seasons (spring / autumn) and at night, so the equipment to be operated It was possible to reduce energy consumption by reducing the number of vehicles.
The heat load during the mid-season and at night is extremely smaller than the maximum heat load described above, and since such a period is long, energy consumption can be significantly reduced during this period depending on the method. In particular, when the heat medium is water (cold water or hot water), a large transport power is required. Therefore, it is important to reduce not only the heat energy of the heat source device but also the power energy of the pump.

FIG. 5 shows a system diagram of a conventional typical district heating and cooling system. In the heat source plant A, a plurality of sets (n sets. Refrigerators (heat source devices) 1, pumps 2 and the like.
(Indicated by subscripts ₁ , ₂ , ..., _N ) are connected in parallel, and a plurality (m) are connected via the collective pipe A1 in the plant A.
set. Similarly, the receiving equipment 10 (with subscript) is connected to the pipe B1 in the area B connected in parallel. The symbol A2 is
Bypass piping for adjusting the difference between the flow rate of cold water (heat medium) supplied by the plant A and the flow rate used on the side of the area B, and reference numeral 6 is for maintaining the pressure of the cold water returned from the area B constant. It is a pressurized tank.

In the system as shown in FIG. 5, the refrigerator 1 and the pump 2 are normally operated at the rated flow rate because the temperature control of the cold water is easy, and the cold water flow rate on the plant A side is the individual rated flow rate. Is the sum of On the other hand, since only the flow rate corresponding to the cooling demand circulates in the region B, the difference from the flow rate on the heat source plant A side flows in the bypass pipe A2 as the bypass flow rate. A flow rate (opening) control valve 9 is provided in the bypass pipe A2 for the purpose of ensuring a necessary pressure (use differential pressure) in each receiving facility 10, and the opening is controlled as follows. That is, plant A, which is the cold water supply point
Internal pipe A1 (or plant A of regional pipe B1)
Pressure gauges 7 and 8 are provided at both the forward and backward points (at a point closer to each other) so that the difference between the detected pressures of the two (hereinafter referred to as the supply differential pressure because of the differential pressure at the source point) is constant. So that the pressure controller 11 operates the control valve 9.
Since the pressure of the cold water returned from the region B is kept constant in the pressure tank 6, it may be controlled based on only the forward pressure (supply pressure or water supply pressure) by the pressure gauge 7.

When the demand for cold water in region B is low,
The number of operating groups of the refrigerator 1 and the pump 2 is reduced, and in the middle season and the like, while only one set of the refrigerator 1 and the pump 2 is operating at the rated flow rate, the bypass flow rate is adjusted in the same manner as above to adjust the supply and demand. to keep balance. Furthermore, when the flow rate from the plant A exceeds the demand in the region B even when the bypass flow rate is fully adjusted, the pump discharge valve 4 is operated by the action of the flow meter 3 and the flow rate controller 4c to supply the supply differential pressure (or supply pressure). ) Is adjusted so that it becomes constant. Such a control method is also described in JP-A No. 62-116846.

[0008]

The conventional method for adjusting the supply and demand of the heat medium in the district heating and cooling system having the closed circulation system has the following disadvantages.

A) Even when the heat medium demand in the area is very small, at least one pump operates at the rated flow rate,
The power required for the pump is large. In other words, no matter how small the heat medium demand is, the power consumption for one pump is inevitably generated, and it cannot be said that the energy saving is sufficient.
Such a loss cannot be ignored because the period when the demand for the heat medium is small extends over a considerable period as described above.

(B) The flow rate on the heat source plant side is reduced by throttling the pump discharge valve (Japanese Patent Laid-Open No. 62-116).
No. 846), it is not very effective in terms of reducing pump power. This is because the pump power is proportional to the product of the capacity (flow rate) and the head when the pump efficiency is constant, but when the capacity is reduced by the pump discharge valve, the head is slightly increased on the contrary.

It should be noted that, among the closed circulation systems, FIG.
In addition to the one-pump system that uses a common pump to circulate heat on the heat source plant side and the circulation on the regional side as described in Section 2, there is a two-pump system (not shown) in which pumps are provided on the heat source plant side and the regional side. However, even in the latter case, the primary pumps on the heat source plant side still have the disadvantages of the above a) and b). Not only that, but because of the large number of pumps, there is a new inconvenience that the equipment cost is high.

[0012] The present invention provides a control method and apparatus capable of reducing the pump power under a low load more than ever before, in regard to heat medium transfer for district heating and cooling.

[0013]

According to the heat medium transfer control method of the present invention (claim 1), a plurality of heat source devices and pumps are connected in parallel for the purpose of district cooling and heating (of which the operating number depends on the local demand). The heat source between the plant side and the regional side regarding the circulation of the heat medium from the heat source plant to multiple receiving facilities via regional piping without passing through the open air part (that is, in a closed circulation system). It is a control method that adjusts the supply and demand of the medium, and is characterized by the following A) and B). That is, A) One or more of the above pumps can be driven at variable speeds, and B) Utilization differential pressure of the receiving equipment near the end of the regional piping (hereinafter referred to as the terminal differential pressure for the supply differential pressure mentioned above) In order to keep it constant: a) At high load, the pump (suitable number of them) is operated at a constant speed, and the bypass flow rate that does not pass through the regional piping is adjusted, and b) At low load, the above-mentioned variable speed drive pump is possible. Only drive and adjust its speed.

Further, the heat medium carrier of the present invention (claim 2)
Is a heat source plant in which a plurality of heat source devices and pumps are connected in parallel (the number of operating units is determined according to local demand) and a regional pipe connecting a plurality of heat medium receiving facilities are not provided with an atmosphere opening portion. (That is, as a closed system), and a device in which a bypass pipe that does not pass through a regional pipe is partially provided and connected, and is characterized by the following items. That is, a means for detecting the differential pressure used in the receiving facility (that is, the differential pressure at the end) is placed near the end of the regional piping, and at least one of the pumps in the heat source plant is driven by an inverter motor. There is provided a control means for selectively adjusting the flow path opening degree of the bypass pipe and controlling the rotation speed of the inverter motor according to the same output.

According to a third aspect of the present invention, there is further provided a heat medium transfer device, wherein parallel pumps are collectively connected to form a collective pipe, and parallel heat source devices are collectively connected to form a collective pipe.
Both collecting pipes are connected.

[0016]

The control method (Claim 1) of the present invention, when under high load,
That is, when the heat medium demand on the local side is high, a) in B) above
As described in, while adjusting the bypass flow rate, operate the constant number of pumps according to demand. This is B)
Although it is different from the conventional method (Fig. 5) in which the supply differential pressure is made constant in that the terminal differential pressure of the regional piping is made constant as described at the beginning of the above, there is no difference in the drive of the pump and the power consumption thereof. .

However, at the time of low load, that is, when the demand for the heat medium on the side of the area is low, and only the pump capable of variable speed driving of the rated operation (for example, one pump) is still supplied with the heat medium on the side of the heat source plant, In this way, the pump power can be reduced very effectively.

The first reason that the pump power can be reduced is
A pump capable of variable speed drive as described in A) above is used in b) above in B).
As described above, the heat medium flow rate is controlled (variable flow rate control) by adjusting the rotation speed. That is, since the pump discharge valve is not throttled, the lift does not rise. Also,
Generally, the power of a pump is proportional to the cube of the number of revolutions, so if the number of revolutions is reduced to reduce the flow rate, the power can be greatly reduced.

The second reason that the power can be reduced is that the flow rate control as described above is performed so that the terminal differential pressure in the regional piping becomes constant as described in B). The use differential pressure required in the receiving equipment can be secured by the control based on the supply differential pressure as described above (example of FIG. 5), but in that case, pressure loss (pressure loss) in piping etc. Maintains the same supply differential pressure even at low flow rates. Then, the receiving equipment connected toward the end is subjected to a higher use differential pressure than necessary at a low flow rate rather than at a high flow rate. On the other hand, if the control is performed based on the differential pressure at the terminal as described above, the pressure at the supply point will be reduced by that amount when the pressure loss of the piping is low, while the usage differential pressure for the receiving equipment near the terminal is kept constant. , The pump power is not consumed more than necessary.

The heat medium carrier of the present invention (claim 2) can be directly used for carrying out the above-mentioned control method. That is, first, when the load is high, the required number of pumps are operated at a constant speed while adjusting the flow passage opening of the bypass pipe (that is, adjusting the bypass flow rate) by the control means described in (1). Then, after reducing the number of pumps to be driven by only the inverter motor drive, the control means is switched and the inverter (frequency change) is used to make the terminal differential pressure detected by the detection means constant. By controlling the rotation speed of the pump, the pump power is reduced.

In addition to the above, the heat medium carrier according to the third aspect has an advantage that the heat source device operated at a low load can be arbitrarily selected. That is, if a plurality of pumps and a plurality of heat source devices are connected via a collective pipe like this device, even if the number of operating pumps is reduced and only pumps driven by an inverter motor are used, the heat source to be operated The device can be freely selected from a plurality of devices. This cannot be done when the pump and heat source equipment are connected in a one-to-one correspondence, and the life of the heat source equipment does not deviate to a specific one even when the load is low. Besides this, it has the advantage that operation can be continued even if one of the devices fails.

[0022]

EXAMPLE As a first example of the present invention, FIG. 1 shows a cold water pump system. A portion A (a portion on the left side of the pipe where the middle portion of the pipe is omitted) is a heat source plant, and is a refrigerator (such as an absorption refrigerator or a turbo refrigerator) 1 or a cold water pump 2.
Besides, a pressure tank 6 and the like for maintaining the return pressure are arranged. The refrigerator 1 and the chilled water pump 2 include a flow meter 3, a flow rate adjusting valve (pump discharge valve) 4, a flow rate controller 4c.
Are connected in a one-to-one correspondence with each other, and there are n sets (the devices of each set are suffixed with ₁ , ₂ , ..., _N )
Only connected in parallel.

Each chilled water pump 2 has the ability to cover the rated flow rate of the corresponding refrigerator 1, and is controlled simultaneously with the refrigerator 1 by the start / stop sequence of the refrigerator 1. In addition, it may be automatically stopped by a signal for controlling the number of refrigerators. This unit number control is performed in the cooling / heating target area B (m receiving facilities 10 ₁ , 10 ₂ , ..., 10 _m are arranged in parallel)
The flow rate and temperature of the cold water supplied to the area B and the temperature of the cold water returned from the area B are measured, and the refrigerator 1 and the cold water pump 2 of the heat source plant A are automatically operated so that both the heat quantity and the flow rate supplied to the area B are not insufficient. It starts and stops. It is also possible to control the number of units in combination with a heat load prediction system.

In this system, one of the n chilled water pumps 2 (No. 1 chilled water pump 2 ₁ ) is driven by the inverter motor 5, and the other is driven by a normal induction motor. In the above number control, 1 refrigerator 1 ₁ and No. ₁ 1 the operation of the chilled water pump 2 ₁ as the first priority, so that both are always activated during operation of the plant A. Reference numeral 9 is a chilled water flow rate control valve provided in the bypass pipe A2, and the regional pipe B
Based on the signal difference (that is, the terminal differential pressure, which corresponds to the differential pressure used for the receiving equipment 10 at the terminal end) of the pressure gauges 7 and 8 installed at the terminal end of 1, through the pressure controller 11 and the switching device 12. The difference between the chilled water circulation amount on the heat source plant A side and the chilled water circulation amount on the region B side is adjusted.

When the cooling load in the region B is high, the set of the refrigerator 1 and the chilled water pump 2 is operated by a number corresponding to the load by the signal for controlling the number of units, and the chilled water amount of each refrigerator 1 is No. 1. 1
The rated flow rate, including the refrigerator 1 _1. That is, No. 1
Rotational speed of the chilled water pump 2 ₁ inverter motor 5 is also constant. At this time, the flow rate of the bypass pipe A2 is controlled by the control valve 9 as described above so that the terminal differential pressure of the regional pipe B1 becomes constant (about 1.5 km).

FIG. 2 shows the pressure balance in the pipes A1 and B1 in the heat source plant A and the area B. This figure compares the case where the heat source plant A and the area B are installed on the same level plane, and the circled numbers on the horizontal axis ... Respectively indicate the chilled water pump 2, the control valve 4, ...
Each of the refrigerator 1, the control valve 9 (bypass pipe A2 part), and the receiving facility 10 _{m at} the end is shown. In this figure, the broken line shows the state at maximum load.

The load of the area B is reduced, and the No. 1 which is the first priority is given by the signal for controlling the number of units. 1 refrigerator 1 ₁ and No. ₁ If the operation of only one cold water pump 2 _1, for the flow rate adjustment device, i.e. includes a pressure gauge 7, 8 and the pressure controller 11, switch 12, flow control valve 9 described above in FIG. 1, so to speak selection function with The control means interlock with it. That is, the switch 12 is switched so that the signal of the terminal differential pressure of the regional pipe B1 is kept constant (about 1.5 km). 1 performs rotational speed control of the chilled water pump 1 ₁ of the inverter motor 5,
The variable flow rate control is performed on the heat source plant A side. At this time, the bypass flow rate control valve 9 is fully closed or slightly opened (if it is slightly opened, it is possible to cope with a sudden increase in the flow rate of cold water on the region B side). The flow rate control valve 4 _first pump 2 ₁ on the discharge side becomes automatically fully opened for coolant flow rate is reduced. The pressure balance at this time is shown by the solid line in FIG.

As in the prior art (Japanese Patent Laid-Open No. 62-116).
The pressure balance in the case where the flow rate is adjusted by the flow rate adjusting valve 4 using a constant speed pump is shown in the same FIG. Even if the terminal differential pressure is controlled to be constant, since the pressure loss in the flow rate adjusting valve 4 is large, the pump 2 ₁
The required head is high.

Further, the signal of the cold water differential pressure (supply differential pressure) at the point of supplying from the heat source plant A to the area B is measured, and kept constant (the same as in the example of FIG. 5 up to this point), the cold water pump 2 for information on how to control the speed ₁ by an inverter motor 5, the pressure balance at the time of low load is as shown in two-dot chain line in FIG. 2, it is impossible to lower the lift of the cold water pump 2 ₁ enough embodiment. In this case, although the pressure loss in the pipe is small, the differential pressure at the cold water supply point (the point in FIG. 2) is made the same as that at the time of maximum load, so the terminal receiving facility 10 _m is considerably It will give a high (about double the required 1.5 km) differential pressure.
In the pump 2 _1, since not much volume reduced lifting height of which reduce (flow rate) (pressure), (indicated by also the two-dot chain line) as seen from the pump characteristic shown in FIG. 3, the inverter motor 5 and pump 2 ₁ It is not possible to significantly reduce the number of rotations of. Therefore, the reduction range of the pump power is small and the energy saving effect is not remarkable.

[0030] In that respect, the method of the present embodiment, at the time of low load, the lift well capacity chilled water pump 2 ₁ can be reduced even significantly (see FIG. 2) for, FIG. 3 (thick solid line)
Rotational speed of the pump 2 ₁ is lowered considerably (to 70% of rating), as. In general, the pump power is proportional to the cube of the rotation speed, so the energy saving effect in this case is extremely large.

Next, FIG. 4 shows a second embodiment of the present invention. In the system shown in FIG. 1, No. So that it operates a refrigerator 1 _1, in order to be able to operation In any chiller 1 at low load without changing the piping system it has been necessary to drive all of the chilled water pump 2 by the inverter motor 5 Will result in a considerable cost increase. The embodiment of FIG. 4 improves on this point.

In the system of FIG. 4, there are k cold water pumps 2 (2 ₁ , 2 ₂ , ...
・ 2 _k ) installed, and one of these pumps 2 ₁ is driven by the inverter motor 5, and these and n refrigerators 1 ₁ 1 ₂ ..... 1 _n are connected via a collective pipe Ax. Connected. For controlling the number of these units, the refrigerator 1
Control of the number of refrigerators 1 commensurate with the division of capacity of the
The number of pumps 2 is controlled in accordance with the capacity division. In this method, by changing the setting of the operation priority order for controlling the number of refrigerators 1, it becomes possible to operate any of the refrigerators 1 at a low load. The embodiment of FIG. 4 has no special difference from the embodiment of FIG. 1 except for the above points, and therefore common portions are denoted by the same reference numerals as those of FIG. 1 and description thereof is omitted.

Although the two embodiments have been introduced above, it goes without saying that the present invention is not limited to these embodiments. That is, the present invention can be implemented as follows, for example.

A) The detection of the differential pressure used in the receiving facility does not necessarily have to be performed at the extreme end of the regional piping. The closer to the end, the higher the effect, but even when detecting, for example, the receiving facility at an intermediate location, a more remarkable effect can be expected than when detecting and controlling the so-called supply differential pressure at a location near the heat source plant. .

(B) If the flow rate of the cold water of the refrigerator is too low compared to the rated flow rate, there is concern about freezing of the cold water. Therefore, measures such as setting the control response of the inverter motor and the lower limit value of the output are taken. Good.

C) The connection of the pump, the refrigerator, etc. is not limited to the order shown in FIG. 1, but when it is necessary to reduce the pressure applied to the refrigerator, the flow meter 3, the refrigerator 1, the chilled water pump 2, the flow rate, etc. The regulating valve 4 may be connected in this order along the flow direction of the heat medium.

D) Although the cold water pump system has been described above, the same applies to the hot water pump system. In the latter system, the refrigerator 1 shown in FIGS.
Is replaced by a heat pump or hot water heat exchanger, but there is no other major difference. In a general district heating and cooling system, the cold water pump system and the hot water pump system described above are installed in parallel.

[0038]

The present invention (the method and apparatus according to claims 1 and 2) has the following effects. That is, 1) It is possible to significantly reduce the pump power when the load is low, that is, when the local demand is low. Moreover, since it does not require specially expensive facilities and equipment as compared with conventional ones, a large energy saving effect can be achieved with a small investment.

2) Since an appropriate utilization differential pressure can be always ensured for the receiving facility, a stable supply of the heat medium is possible.

3) Regarding the temperature control of the heat medium leaving the heat source device (refrigerator, heat pump, hot water heat exchanger, etc.), the conventional control means can be used as it is.

In the apparatus of claim 3, further, 4) there is an advantage in the life of the equipment and trouble measures because the heat source equipment to be operated can be arbitrarily selected when the load in the area is low.

[Brief description of drawings]

FIG. 1 is a system diagram showing a cold water pump system (heat medium carrier) as a first embodiment of the present invention.

FIG. 2 is a diagram showing pressure balance at various points in the system of FIG. 1 in comparison with those in other systems.

FIG. 3 is a diagram in which operating conditions of the pump in the system of FIG. 1 and operating conditions of the pump in other cases are superimposed on the characteristic curve of the pump.

FIG. 4 is a system diagram showing a cold water pump system (heat medium transfer device) as a second embodiment of the present invention.

FIG. 5 is a system diagram showing a conventional cold water pump system (heat medium transfer device).

[Explanation of symbols]

 A heat source plant A2 bypass piping Ax collective piping B area B1 area piping 1 refrigerator (heat source equipment) 2 pump 5 inverter motor 10 receiving facility

Claims (3)

[Claims] 1. Heat for circulating a heat medium from a heat source plant in which a plurality of heat source devices and pumps are connected in parallel for district heating and cooling to a plurality of receiving facilities via regional piping without passing through an open air portion. A method of controlling medium transport, in which one or more of the above pumps can be driven at variable speeds and the differential pressure used in the receiving equipment near the end of the regional piping is kept constant. While operating at high speed, adjust the bypass flow rate that does not pass through the regional piping,
b) A heating medium transfer control method for district cooling and heating, characterized in that only the pump capable of variable speed driving is operated at low load to adjust the rotation speed. 2. For district heating and cooling, a heat source plant in which a plurality of heat source devices and pumps are respectively connected in parallel and a regional pipe in which a plurality of heat medium receiving facilities are connected are provided without providing an atmosphere opening portion, and A heat medium transfer device in which a bypass pipe that does not pass through a regional pipe is partially provided and connected, wherein the means for detecting the differential pressure of the utilization of the receiving facility is arranged near the end of the regional pipe, and the pump in the heat source plant One or more of them are driven by an inverter motor, and the flow path opening of the bypass pipe is adjusted according to the output of the detection means, and the rotation speed control of the inverter motor according to the same output is selectively performed. A heating / cooling medium transfer device for district heating / cooling, comprising a control means. 3. The heat for district heating and cooling according to claim 2, wherein parallel pumps are collectively connected to form a collective pipe, and parallel heat source devices are collectively connected to form a collective pipe, and both collective pipes are connected. Medium transport device.