JP5601412B2 - Control method of heat supply system - Google Patents

Description

  The present invention relates to a method for controlling a heat supply system.

  As a heat supply system, a configuration is generally known in which the heat of steam generated by a boiler is transmitted to an object (see, for example, Patent Document 1). In addition, a configuration in which heat of a heat pump medium is transmitted to an object is known. It is known that a heat pump has a relatively high energy utilization efficiency by utilizing heat outside the cycle (heat of a low-temperature heat source).

JP-A-6-249450

  A system using a boiler has a relatively low primary energy efficiency. On the other hand, in a system using a heat pump, if the amount of heat and temperature supplied from a low-temperature heat source are unstable, there may be a situation where the heat demand cannot be sufficiently met.

  An object of this invention is to provide the control method of a heat supply system with high energy efficiency.

  According to the aspect of the present invention, the control method of the heat supply system that mixes the first fluid heated by the heat pump and the second fluid heated by the boiler in the mixing unit and supplies heat of the thermal fluid mixed in the mixing unit. In the above, after mixing with the heat pump based on the information on the temperature and flow rate of the low-temperature heat source supplied from the outside to the heat pump, the information on the heat demand, the outlet condition of the boiler, and the primary energy efficiency Provided is a control method of a heat supply system for controlling the flow rate and temperature of the first fluid supplied to the section and the flow rate and temperature of the second fluid supplied to the mixing section after being heated by the boiler Is done.

A first device including a heat pump for heating the first fluid; a second device for heating the second fluid; the heat of the first fluid heated by the first device; and the second device heated by the second device. An output device for transmitting the heat of the second fluid to the outside, and a control device for controlling the operation of the heat pump between a full load and a partial load, and controlling the supply amount of the second fluid heated by the second device And a heat supply system comprising:
According to this heat supply system, by optimizing the operation of the heat pump between the full load and the partial load, the combination of the first device including the heat pump and the other second device can be optimized. Efficiency is improved.

It is the schematic which shows 1st Embodiment. It is a figure which shows an example of the performance curve of the compressor in a heat pump. It is a figure which shows the relationship between the temperature of a low-temperature heat source, and partial load efficiency. It is a flowchart which shows an example of operation | movement of a heat supply system.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a heat supply system S1.

  As shown in FIG. 1, the heat supply system S1 includes a first heating device (first device) 12 having a heat pump (heat pump circuit) 20 and a second heating device (second device) 14 having a heating device other than the heat pump. And an output device 16 and a control device 18. The control device 18 comprehensively controls the entire system. The configuration of the heat supply system S1 can be variously changed according to design requirements.

  In the first heating device 12, the heat pump 20 is a device that pumps heat from a low-temperature object and applies heat to the high-temperature object by a cycle including evaporation, compression, condensation, and expansion processes. A heat pump generally has the advantage of relatively high energy efficiency and, as a result, relatively low emissions of carbon dioxide and the like.

  In the present embodiment, the heat pump 20 has a heat absorption part 21, a compression part 22, a heat radiation part 23, and an expansion part 24, which are connected via a conduit. In the heat pump 20, the working fluid flows in the conduit. In the present embodiment, the heat pump 20 heats the fluid to be heated (water) flowing through the output device 16 using the heat of the working fluid.

  In the heat absorption part 21, the working fluid flowing through the main path 25 absorbs heat from a heat source outside the cycle (low temperature heat source). In this embodiment, the heat absorption part 21 of the heat pump 20 includes an evaporator that is thermally connected to the heat radiating pipe 91 of the external device 90 and in which the working fluid evaporates. The heat of the medium (refrigerant, etc.) flowing through the heat radiating pipe 91 is absorbed by the heat absorbing part 21 of the heat pump 20. It is also possible to use the exhaust heat of the external device 90 as a heat source. The heat absorption part 21 can also be configured to absorb the heat of other heat sources such as the atmosphere.

  The compression unit 22 compresses the working fluid by a compressor or the like. At this time, the temperature of the working fluid usually increases. The compression unit 22 can have a single-stage compression structure or a multistage compression structure that compresses the working fluid into a plurality of stages. The number of compression stages is set according to the specification of the heat supply system S1, and is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more. Among the various compressors such as an axial flow compressor, a centrifugal compressor, a reciprocating compressor, and a rotary compressor, a compressor suitable for compressing the working fluid is applied. Power is supplied to the compressor. In the compression unit 22 having a multistage compression structure, a multiaxial compression structure or a coaxial compression structure can be applied.

  The heat radiating part 23 has a conduit through which the working fluid compressed by the compressing part 22 flows, and gives heat of the working fluid flowing in the main path 25 to a heat source (heated fluid) outside the cycle. The number of heat radiation units is set according to the specification of the system S1, and is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more.

  The expansion unit 24 expands the working fluid by a pressure reducing valve, a turbine, or the like. At this time, the temperature of the working fluid usually decreases. When a turbine is used, power can be taken out from the expansion unit 24, and the power may be supplied to the compression unit 22, for example. As a working fluid used in the heat pump 20, various known heat media such as a fluorocarbon medium (HFC 245fa, R134a, etc.), ammonia, water, carbon dioxide, air, and the like are selected according to the specifications and heat balance of the system S1. Used. At least a part of the working fluid flowing through the heat radiating portion 23 of the heat pump 20 may be in a supercritical state.

  In this embodiment, the 2nd heating apparatus 14 has the boiler 40 as heating apparatuses other than a heat pump. In this embodiment, the boiler 40 burns fuels, such as oil and gas, and heats a to-be-heated fluid (water) with the combustion heat. Various known forms can be applied as the boiler 40. Additionally or alternatively, the second heating device 14 can have other heating devices such as an electric heater.

  The output device 16 transmits the heat of the fluid heated by the first heating device 12 and the heat of the fluid heated by the second heating device 14 to the outside. In the present embodiment, the output device 16 includes a first heating unit 61, a second heating unit 62, a mixing unit 63, and an output unit 64. The output device 16 further includes a conduit through which water as a fluid to be heated flows, a valve for fluid control, and the like.

  The first heating unit 61 includes a conduit that is thermally connected to the heat radiating unit 23 of the heat pump 20 in the first heating device 12 and through which water flows. The heat exchanger 31 is configured including the first heating unit 61 and the heat dissipation unit 23. The heat exchanger 31 can have a countercurrent heat exchange structure in which a low-temperature fluid (water in the output device 16) and a high-temperature fluid (working fluid in the heat pump 20) face each other. Alternatively, the heat exchanger 31 may have a parallel flow type heat exchange structure in which a high-temperature fluid and a low-temperature fluid flow in parallel. In the present embodiment, various known heat exchange structures of the heat exchanger 31 can be employed. The conduit of the heat radiating unit 23 and the conduit of the first heating unit 61 are disposed in contact with or adjacent to each other. For example, the conduit of the heat radiating unit 23 can be disposed on the outer peripheral surface or inside of the conduit of the first heating unit 61. In the first heating unit 61, the temperature of the water in the conduit rises due to the heat transferred from the heat radiating unit 23 of the heat pump 20.

  The second heating unit 62 includes a conduit that is thermally connected to the second heating device 14 and through which water flows. In the present embodiment, the second heating unit 62 is thermally connected to the combustion chamber of the boiler 40. In other embodiments, the second heating unit 62 can be thermally connected to an electric heater. In the second heating unit 62, the water in the conduit evaporates into steam due to the heat transferred from the combustion chamber of the boiler 40.

  At least the thermal fluid heated by the first heating unit 61 and the thermal fluid heated by the second heating unit 62 flow into the mixing unit (mixer) 63. In the mixing part 63, those hot fluids can be mixed. In the present embodiment, as described above, the thermal fluid from the first heating unit 61 is water (high temperature water), and the thermal fluid from the second heating unit 62 is steam. The mixing unit 63 can include a fluid drive device such as a pump. In the present embodiment, pressurized water (compressed water) can be output from the mixing unit 63.

  The output unit 64 has a conduit (heat radiating pipe) through which the thermal fluid from the mixing unit 63 flows, and discharges the heat of the thermal fluid to the outside. The number of output units 64 (radiating tubes) is set according to the specification of the system S1, and is 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 or more. In the present embodiment, the output unit 64 is thermally connected to an endothermic tube 96 through which a predetermined medium flows. The heat of the thermal fluid flowing through the output unit 64 is absorbed by the medium flowing through the heat absorption tube 96. The medium whose temperature has increased through the heat absorption tube 96 is supplied to a predetermined external device 95. In other embodiments, the heat sink tube of a given external device 95 can be thermally connected to the output unit 64.

  A heat exchanger 65 is configured including the conduit of the output unit 64 and the heat absorption pipe 96. The heat exchanger 65 can have a countercurrent heat exchange structure in which a low-temperature fluid and a high-temperature fluid flow oppositely. Alternatively, the heat exchanger 65 may have a parallel flow type heat exchange structure in which a high-temperature fluid and a low-temperature fluid flow in parallel. In the present embodiment, various known heat exchange structures for the heat exchanger 65 can be employed. The conduit of the output unit 64 and the heat absorption tube 96 are arranged in contact with or adjacent to each other. For example, the endothermic tube 96 can be disposed on the outer peripheral surface or inside of the conduit of the output unit 64.

  In the present embodiment, the output device 16 further includes a control valve 161 and a bypass path 162. A relatively cold fluid (cold water) can flow through the bypass path 162. For example, by controlling the control valve 161, the amount of low-temperature water supplied to the mixing unit 63, that is, the flow rate ratio between the first heating unit 61 and the bypass path 162 can be controlled. In the present embodiment, the output device 16 further includes a control valve 163 that controls the amount of steam supplied from the second heating unit 62 to the mixing unit 63.

  In the heat quantity complementation only with steam, the exit condition of the mixing unit 63 may be steam (wet steam). When the heat exchanger 65 is designed on the premise of pressurized water, by supplying low temperature fluid (low temperature water, feed water) to the first heating unit 61 and supplying it to the mixing unit 63 as necessary, The outlet condition of the mixing unit 63 can be pressurized water.

  In the present embodiment, the system S1 has a return path 70 for reusing the fluid after heat output. The fluid after radiating heat from the output unit 64 flows through the return path 70. The fluid (water) from the return path 70 is input again to the first heating device 12 (heat pump 20). Or it is thrown into the 2nd heating apparatus 14 (boiler 40) again. Excess fluid from the output unit 64 can be appropriately discharged to the outside. By reusing the fluid, the operation cost can be reduced.

  In the present embodiment, the system S1 includes heat demand information (required temperature, required flow rate) in the external device 95, output information (temperature, pressure, etc.) of the boiler 40, and low-temperature heat source information for the heat pump 20 (exhaust heat in the external device 90). Sensors for detecting information, etc.) as necessary. The control device 18 can comprehensively control the entire system S1 based on various information. In the present embodiment, the control device 18 can control the operation of the heat pump 20 between the full load and the partial load. According to the present embodiment, the control including the partial load operation of the heat pump 20 and the backup by the boiler 40 can improve the energy efficiency of the entire system S1.

  Moreover, in this embodiment, steam and high temperature water are mixed in the mixing part 63, and the mixed thermal fluid is used for heat supply. By mixing the fluids of a plurality of phases, for example, compared with in-phase mixing of high-temperature water and high-temperature water, a thermal fluid according to demand can be created flexibly. The multi-phase type mixing unit 63 is also advantageous in simplifying the system configuration. Furthermore, since the low temperature water via the bypass path 162 can be input to the mixing unit 63, the flexibility for further heat demand can be improved. As a result, the thermal fluid can be supplied to the output unit 64 so as to simultaneously satisfy the flow rate and temperature required from the demand side. Thus, according to the present embodiment, it is possible to flexibly cope with a relatively severe demand on the demand side.

  Here, the following formulas (1) and (1 ′) hold from the energy conservation law at the inlet and outlet of the mixing unit 63. G: mass flow rate [kg / s], h: enthalpy [J / kg / K], p: pressure [Pa], T: temperature [K], W: heat quantity [J / s]. The subscripts in B are: B; boiler, BP: bypass, D: demand (demand), h: heat pump.

  Moreover, the following formula | equation (2) is formed from the mass conservation law in the inlet of the mixing part 63, and an exit.

  The following formulas (3) and (4) are derived from the formulas (1) and (2).

  From the above formulas (3) and (4), it can be seen that GB = 0 and GBP = 0 are obtained by supplying heat with the heat pump 20 such that hH = hD and GH = GD.

  The following examples can be considered for each enthalpy; hB: enthalpy of saturated vapor at 150 ° C., hBP: enthalpy of liquid at 50 ° C., hD: enthalpy of saturated liquid at 150 ° C., hH: saturated liquid at 150 ° C. Enthalpy.

  Actually, TH (that is, the same as hH) and GH are influenced by the temperature and flow rate of a low-temperature heat source in the heat pump 20, for example. In the present embodiment, even when the flow rate and temperature of the low-temperature heat source fluctuate, the heat is supplemented with steam from the boiler 40, and the heat pump 20 is controlled to operate externally between the full load and the partial load, thereby being stabilized to the outside. Heat can be supplied.

In the primary energy evaluation of the system S1, the following values can be considered as examples; COP (Coefficient of Performance): 3, power generation efficiency: 40%, boiler efficiency: 90%. In this case, basically, the primary energy efficiency of the heat pump 20 is 120%, and it is advantageous to increase the operating rate of the heat pump 20.
Primary energy efficiency = COP x power generation efficiency x WH / WD + boiler efficiency x WB / WD
= 3 x 0.4 x 100/100 + 0.9 x 0/100
= 1.2
However, in the heat pump 20, as shown in FIGS. 2 and 3, there are cases where the partial load efficiency is higher than the constant load efficiency. Specifically, when the temperature of the low-temperature heat source is high, that is, when the pressure ratio is small, the partial load efficiency may be relatively high. By controlling the entire system S1 including the partial load operation of the heat pump 20, the energy efficiency can be improved. For example, in the heat pump 20 having a COP of 3 in the entire operation (100 kW) in the above example, the COP of the partial load operation (50 kW) is 5. In this case, the primary energy efficiency of the heat pump 20 is 145%.
Primary energy efficiency = COP x power generation efficiency x WH / WD + boiler efficiency x WB / WD
= 5 x 0.4 x 50/100 + 0.9 x 50/100
= 1.45

FIG. 4 is a flowchart illustrating an example of the operation of the system S1.
As shown in FIG. 4, first, information such as information related to heat demand (temperature and flow rate), outlet conditions (temperature and pressure) of the boiler 40, water supply conditions, and low-temperature heat source conditions (temperature and flow rate) for the heat pump 20 are input. (Steps 201, 202, 203).

  Next, based on the input information and information on the performance of the heat pump 20, the output (temperature and flow rate) of the heat pump 20 is determined so as to satisfy the heat demand (step 204).

  Next, it is determined whether or not the heat demand can be satisfied only by the output of the heat pump 20 (step 205). When the heat demand is satisfied, a condition is set in which no fluid is supplied from the boiler 40 and the bypass path 162 (step 206). When the heat demand is not satisfied, the fluid supply amount from the boiler 40 and the bypass path 162 is determined using the equations (3) and (4) (step 207). When the heat demand is not satisfied, (1) the heat supply flow rate from the system S1 is insufficient, (2) the heat supply temperature is insufficient, and (3) the heat supply flow rate and the heat supply temperature are insufficient. If included.

  Next, the primary energy efficiency of the entire system S1 is calculated based on the determined heat flow distribution (step 208). Further, the evaluation of the primary energy, economic efficiency, and environmental performance of the system S1 can be evaluated (step 209). For this evaluation, for example, a predetermined index relating to economic efficiency and environmental performance can be used.

  Also, in step 209, it can be determined whether optimization has been completed with respect to heat flow distribution. If not completed, the output of the heat pump 20 can be changed (step 210). In this case, the primary energy efficiency is calculated in the same manner as described above for the predetermined load state of the heat pump 20 between the full load and the partial load. Calculation is performed for a plurality of load states of the heat pump 20, and as a result, optimum values can be obtained for the load state of the heat pump 20 and the heat flow distribution. That is, the control device 18 can optimize the load ratio of the heat pump 20 and the flow rate ratio of the high temperature water, steam, and low temperature water to the mixing unit 63.

  The above series of flows can be performed, for example, when the heat demand or the low temperature heat source conditions change. The system S1 can implement stable heat supply with high energy efficiency based on the optimum conditions.

  According to the trial calculation, when the performance of the heat pump 20 in the partial load operation is higher than that of the full load, it is confirmed that the energy efficiency of the entire system S1 can be improved by the partial load operation of the heat pump 20. .

  In the present embodiment, it is assumed that not only the flow rate of the thermal fluid from the heat pump 20 but also the temperature deviates from the rated value. In this case, by using steam from the boiler 40 and cold / hot water from the bypass path 162, the thermal fluid output from the heat pump 20 can be easily matched to the temperature and flow rate required from the demand side. As a result, the system S1 has a wide degree of freedom of the heat pump 20, and can obtain a substantial maximum efficiency in a wide range.

  As described above, according to the present embodiment, even if the amount of heat and temperature supplied from the low-temperature heat source are unstable, it is possible to stably meet the heat demand. Moreover, optimization of the output ratio of the heat pump 20 and the boiler 40 is achieved, and as a result, it can contribute to reduction of primary energy.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said embodiment. The numerical value used in the above description is an example, and the present invention is not limited to this. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention. The present invention is not limited by the above description, but only by the appended claims.

S1: heat supply system, 20: heat pump, 12: first heating device (first device), 14: second heating device (second device), 16: output device, 18: control device, 40: boiler, 61: First heating unit, 62: second heating unit, 63: mixing unit (mixer), 64: output unit, 70: return path, 90, 95: external device, 161, 163: control valve, 162: bypass path.

Claims (3)

In the control method of the heat supply system in which the first fluid heated by the heat pump and the second fluid heated by the boiler are mixed in the mixing unit, and the heat of the thermal fluid mixed in the mixing unit is supplied.
Based on information on the temperature and flow rate of the low-temperature heat source supplied from the outside to the heat pump, information on heat demand, outlet conditions of the boiler, and primary energy efficiency, after being heated by the heat pump, in the mixing unit The control method of the heat supply system which controls the flow volume and temperature of the said 1st fluid supplied, and the flow volume and temperature of the said 2nd fluid supplied to the said mixing part after heating with the said boiler. The control method of the heat supply system according to claim 1, further controlling a supply amount of the first fluid supplied to the mixing unit by bypassing the heat pump. The control method of the heat supply system according to claim 1 or 2, wherein the flow rate and the temperature in the first fluid and the second fluid are controlled so that the primary energy efficiency is maximized.

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