JP2015040662A - Method for supplying heat source liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use pulsation when a heat source liquid such as water or brine is supplied to heat exchangers in an identical multi-load connection type piping system, and thereby pump power is reduced.SOLUTION: A piping system is configured such that a plurality of identically configured heat exchangers A, B are connected in parallel to outgoing pipes 12 and incoming pipes 13 through supply branch pipes 14 and feedback branch pipes 15, and heat source liquid is supplied to each heat exchanger A, B by a pump 11. In the piping system, the plurality of heat exchangers are divided into two groups of Ato Aand Bto Bby half number, and control valves MV are provided to the supply branch pipes 14 of each group. A flow rate of the heat source liquid flowing to the supply branch pipes 14 is periodically changed and pulsation is generated. Also, the periods of pulsation are shifted by half cycle between the groups of Ato Aand Bto B.

Description

  The present invention provides a piping system (hereinafter referred to as “same multi-load connection type piping system”) in which a large number of heat exchangers having the same configuration are connected in parallel and water and brine are uniformly supplied to branch pipes connected to each heat exchanger. In other words, the present invention relates to a heat source liquid supply method for reducing the power of a pump used to circulate these liquids.

  In the same multi-load connection type piping system, there is a direct return method in which a constant flow valve with the same set flow rate is installed in each branch pipe, or a reverse return method in which the pipe length connecting the supply source pump and each branch pipe is equal. Although there is a circulation flow rate in any method, water and brine in the pipe are turbulent.

  On the other hand, when the fluid is transferred through the same piping system, the fluid is periodically pressurized and repeatedly accelerated and decelerated to generate “pulsation”, bringing the fluid flow from a turbulent state to a laminar state, Conventionally, it has been proposed to reduce the frictional resistance coefficient between the wall and the fluid and reduce the conveyance power (Patent Documents 1 and 2).

WO2009 / 044744 JP 2012-202681 A

  However, in the above-mentioned conventional document, although the basic principle for supplying fluid from one supply source to one supply destination through one pipeline is disclosed, However, there was no special disclosure. Therefore, for example, a snow melting system installed on the side of a railway line used in high-speed railways in cold districts, etc. For a large number of heat exchangers (loads), heat source water passes from one main pipe to each heat exchanger through branch pipes. The problem is how to use the pulsation to reduce pump power when supplying the pump. For example, when laminarization of the main pipe is attempted, the flow rate and the pipe diameter of the main pipe differ depending on the location, and therefore there is no appropriate value for the cycle of laminar flow or the flow velocity fluctuation range. On the other hand, if the main pipe flow rate is pulsated by 0.5 to 1.5 times, for example, in order to achieve laminar flow of each branch pipe, the reverse return system enables laminar flow of the branch pipe itself. However, since the flow rate fluctuation in the main pipe is large, the pressure loss in the main pipe becomes extremely large.

  This invention is made | formed in view of this point, When supplying heat source liquids, such as water and a brine, using a pump with respect to the heat exchanger in the above same multi-load connection type piping system Another object is to reduce the power of the pump using pulsation.

  To achieve the above object, the present invention provides a piping system in which a plurality of heat exchangers having the same configuration are connected in parallel to a main pipe through branch pipes, and a heat source liquid is supplied to each heat exchanger by a pump. The plurality of heat exchangers are divided into two groups each having a half, and the flow rate of the heat source liquid flowing in the branch pipes of each group is periodically changed to generate pulsation. It is characterized by the fact that it is shifted by half a period between them.

  In the present invention, a plurality of heat exchangers of the same multi-load connection type piping system are divided into two groups each having a half, and the pulsation is generated by periodically changing the flow rate of the heat source liquid flowing in the branch pipes of each group. The cycle of the pulsation is shifted by a half cycle between each group, so that the flow rate of the main pipe is not changed, so that the pressure loss of the main pipe remains unchanged, and each branch pipe has a pulsating flow in the branch pipe. The conveyance power of the pump can be reduced by reducing the frictional resistance coefficient between the pipe inner wall and the heat source liquid.

  The plurality of heat exchangers are preferably arranged so that heat exchangers belonging to different groups are alternately arranged.

  When the flow rate of the heat source liquid flowing in the branch pipes is periodically changed, the flow rate adjustment valve provided in each branch pipe may be controlled by opening degree control.

  In periodically changing the flow rate of the heat source liquid flowing in the branch pipes, the flow rate of the heat source liquid may be controlled by controlling individual pumps provided in the branch pipes.

  Furthermore, for a pair of two adjacent heat exchangers belonging to different groups, water is taken from the main pipe through one branch pipe, a three-way valve is provided in the branch pipe, and the other is connected to the three-way valve. Are connected to each heat exchanger of the heat exchanger pair, and the flow rate of the heat source liquid flowing through the two pipes is shifted periodically by half a cycle by controlling the opening of the three-way valve. You may make it make it.

  According to the present invention, when supplying the heat source liquid to a plurality of heat exchangers of the same multi-load connection type piping system, the pressure loss of the main pipe remains as it is, and the branch pipes in the branch pipes due to the pulsating flow remain in each branch pipe. The conveyance power of the pump can be reduced by reducing the frictional resistance coefficient between the wall and the heat source liquid.

It is explanatory drawing which shows the outline of a structure of the hot water supply system to which embodiment was applied. It is a table | surface which shows the target flow rate instruction | indication example of each branch pipe in the hot water supply system concerning embodiment. It is explanatory drawing of the pressure distribution in the case of the structure which flows a fluid in each pipe | tube without generating a pulsation. It is explanatory drawing of the pressure distribution in this embodiment which generated the pulsation in each branch pipe. It is explanatory drawing of a structure when shifting a pulsation in each branch pipe by a half cycle using a shunt type three-way valve. It is explanatory drawing of a structure when shifting a pulsation in each branch pipe by a half cycle using a mixed type three-way valve.

  FIG. 1 shows an outline of the configuration of a hot water supply system 1 to which the embodiment is applied. High temperature water generated by a boiler 2 is supplied to a heat exchanger 4 by a pump 3, and the heat exchanger 4 The supplied hot water (heat source water) is generated by exchanging heat with water.

The hot water leaving the heat exchanger 4 is supplied to the heat exchangers A _{1 to} A _N and B _{1 to} B _N (N is an arbitrary natural number) serving as loads by the pump 11. The return is made through the return pipe 13. In the present embodiment, a plurality of heat exchangers A and B are installed, that is, a total of 2N heat exchangers A and B.

The heat exchangers A _{1 to} A _N and B _{1 to} B _N have the same configuration and the same rating, and correspond to, for example, snow melting panels connected to each other. The heat exchanger having the same configuration refers to a heat exchanger having a pipe diameter and a pipe shape that are substantially the same. For convenience of control, these heat exchangers A _{1 to} A _N and B _{1 to} B _N are grouped into A group heat exchangers A _{1 to} A _N and B group heat exchangers B _{1 to} B _N. The A group heat exchangers A _{1 to} A _N and the B group heat exchangers B _{1 to} B _N are alternately arranged as shown in FIG.

Each of the heat exchangers A _{1 to} A _N and B _{1 to} B _N takes hot water from the outgoing pipe 12 through the supply branch pipe 14, discharges heat to the outside in the heat exchangers A and B, and then returns. The hot water cooled through the branch pipe 15 is returned to the return pipe 13.

As can be seen from FIG. 1, in this embodiment, each of the heat exchangers A _{1 to} A _N and B _{1 to} B _N is the same multi-load connection type pipe of the so-called reverse return type with respect to the heat exchanger 4. constitute a system, pipe length between the heat exchangers _{a 1 ~A N, B 1 ~B} N and the heat exchanger 4 is piped to have the same length. Each supply branch pipe 14 is provided with a continuously variable control valve MV for controlling the flow rate by opening and closing.

  The outgoing pipe 12 near the outlet of the heat exchanger 4 is provided with a temperature sensor t 1 for measuring the temperature of the fluid in the outgoing pipe 12, and the return pipe 13 near the inlet of the heat exchanger 4 is provided in the return pipe 13. A temperature sensor t2 for measuring the temperature of the fluid is provided. The measurement data of these temperature sensors t1 and t2 are output to the control device C.

  The control device C has an output from the differential pressure gauge 16 that measures the differential pressure between the pressure measurement points P1 and P3, that is, a differential pressure dP between the outgoing pipe 12 and the return pipe 13 (in other words, in the supply branch pipe 14). Pressure loss) is input.

  The control device C determines the flow of liquid from the pipe diameter of each branch pipe (supply branch pipe 14 and return branch pipe 15), the set flow rate, and the liquid temperature of the main pipe (average value of the main pipe forward pipe t1 and return pipe t2) t. A pulsation period T and a flow velocity fluctuation width (amplitude of flow velocity / average flow velocity) are calculated, and a target flow rate for each time set in a predetermined schedule is calculated. Then, the control device C instructs the respective control valves MV to open continuously (for example, once per second) so as to realize the pulsation cycle T, the flow velocity fluctuation range, and the flow rate at each time (target flow rate). To do. At this time, for example, the flow fluctuations of the branch pipes (the supply branch pipe 14 and the return branch pipe 15) of the A group and the B group are shifted by a half cycle (the phase of the pulsating flow is shifted 180 degrees), and the forward pipe 12 and the return pipe 13 is controlled so as not to change the flow rate of the main pipe constituted by 13.

  The hot water supply system 1 according to the embodiment has the above configuration, and a control example thereof will be described next.

First, the given conditions are as follows.
N = 1000 (ie, the branch pipe is treated as one in the pair of the supply branch pipe 14 and the return branch pipe 15, and the total of the A group and the B group is 2000),
Set flow rate q _S = 7 [L / min] = 1.17 × 10 ⁻⁴ [m ³ / s] of each branch pipe (supply branch pipe 14 and return branch pipe 15),
Pipe inner diameter d × tube length = 0.02 [m] × 55 [m] of each branch pipe (supply branch pipe 14 and return branch pipe 15),
Average flow velocity u [m / s] = flow rate [m ³ / s] / (π × (inner diameter d [m] / 2) ² ) = 0 in each branch pipe (supply branch pipe 14 and return branch pipe 15) = 0. 37 [m / s]

And water was used as a heat source liquid, and the temperature t was 10 degreeC. Therefore, when t = 10 [° C.], the liquid density ρ = 1000 [kg / m ³ ] and the kinematic viscosity ν = 1.33 [mm ² / s] of the liquid.

And assuming the Reynolds number Re = 5600 in the branch pipe (average value of one period in the branch pipe) and the degree of laminarization due to pulsation, the average pressure gradient of one period is 49 [Pa / m]. One cycle average wall friction stress τ _w = d / 4 × (one cycle average pressure gradient) = 0.24 [Pa] was obtained. When the pulsation cycle T was obtained by setting the conditions for laminarization as T ^* = 10, for example, T = 10 × d / 2 / (τ _w / ρ) ^0.5 = 6.4 [s] was obtained. For example, when a flow velocity fluctuation width (= (flow velocity amplitude / average flow velocity)) such that α _a = (average pressure gradient in acceleration period / average pressure gradient in one cycle) = 4 is obtained, 1.22 is obtained. It was. The above calculation is described in WO 2009/044764 and “Experimental Investigation of Pump Control for Drag Reduction in Pulsating in Pulsing Turbo Pipe Flow” (Proc. Of the Sixth Int. 765, 2009). The target flow rate instruction for each branch pipe based on this result is as shown in the table of FIG.

Then, for example, each branch pipe (supply branch pipe) is controlled by controlling the opening degree of the control valve MV of each branch pipe (supply branch pipe 14) of the A group and the B group so that the target flow rate instruction value of FIG. 14, the turbulent flow in the return branch pipe 15) can be made close to laminar flow, and accordingly, the frictional resistance coefficient between the inner wall of the branch pipe and the heat source liquid is reduced, thereby reducing the conveyance power of the pump 11. be able to. Note that the power reduction ratio [R _W ] _T obtained using [Equation 8] of WO2009 / 044744 was 61.5%.

FIG. 3 is a pressure distribution diagram in a comparative example in which the fluid is allowed to flow in each pipe without generating pulsation in the hot water supply system 1 shown in FIG. 1, and FIG. 4 shows pulsation generated in each branch pipe. It is a pressure distribution figure in this embodiment. In these drawings, the horizontal axis indicates N (branch pipe number, increases as the distance from the pump increases), and the vertical axis indicates pressure (pressure of water or brine in the pipe). The set flow rate of the fluid flowing through each branch pipe is set to the same amount in any case. Moreover, p1-p5 in FIG. 3, FIG. 4 has shown each pressure in the point of the following position P1-P5 shown in FIG. In the figure, a is the pressure loss of the heat exchanger 4, b is the pressure loss of the control valve MV, and c is the differential pressure of the pump 11.
Position P1: in往管12, upstream position of the connecting portion between the supply branch pipe 14 of the heat exchanger A ₁ closest to the heat exchanger 4 side P2: in往管12, farthest from the heat exchanger 4 Connection position P3 with a supply branch pipe 14 of a certain heat exchanger B _N : Connection position P4 with a return branch pipe 15 of the heat exchanger A ₁ located closest to the heat exchanger 4 in the return pipe 13: In the return pipe 13, the downstream side position P5 of the connection part between the return branch pipe 15 of the heat exchanger B _N located farthest from the heat exchanger 4 and the return pipe 13: In the vicinity of the inlet of the pump 11 in the return pipe 13

  The pressure at the position P1 to P5 is highest at the position P1 (N = 0) closest to the downstream side from the pump 11 and is p1. As N increases (away from the pump 11), the pressure decreases due to the pipe resistance, and the pressure in the outgoing pipe 12 has a distribution as shown by the line L1 in FIG. 3, and at the end (P2) of the outgoing pipe 12, the pressure p2 Become. In the supply branch pipe 14 connecting the outgoing pipe 12 and the return pipe 13, the pressure is reduced by (p1-p3) due to the pressure loss of the heat exchanger 4 and the control valve MV. Since the shapes of the supply branch pipes 14 are the same, the pressure drop amounts are the same regardless of the value of N, and the lines L1 and L2 in FIG. The pressure in the return pipe 13 is distributed as shown by the line L2 in FIG. 3, and is p4 at the end (P4). While returning from the end of the return pipe 14 to the pump 11, the pressure further decreases to p5 due to the piping resistance of the return pipe 14.

  On the other hand, when the pulsation is performed as in the embodiment, since the flow rate and the pipe diameter are not changed in the forward pipe 12 and the return pipe 13, the slopes of the line L1 and the line L2 are not changed. However, since there is a pressure loss reduction due to laminarization in the supply branch pipe 14, the distance between the line L1 and the line L2 (pressure drop amount in the supply branch pipe 14) becomes small. The pressure drop in the supply branch pipe 14 is caused by the control valve MV and the heat exchangers A and B (arrows “control valve pressure loss”, “heat exchanger pressure loss” in the figure), but is controlled by the adjacent supply branch pipes 14. The variation of the opening degree and flow rate of the valve MV is shifted by a half cycle. As a result, the pressure distribution as shown in FIG. 4 is obtained.

  In the above embodiment, since the differential pressure at two points close to the outgoing pipe 12 and the return pipe 13, that is, the differential pressure dP on the upstream and downstream of the branch pipe is measured, the “average pressure gradient of one cycle” is set to “ It may be calculated by replacing with “dP / length of each branch pipe”. In this case, the assumption of the degree of laminarization due to pulsation in the branch pipe becomes closer to the actual situation.

In the above-described embodiment, each supply branch pipe 14 is provided with a control valve MV so that the pulsation periods of the heat exchangers A _{1 to} A _N of the A group and B _{1 to} B _N of the B group are shifted by half a period. However, instead of this, a pump and a check valve are individually provided for each supply branch pipe 14, and pulsation is generated for each supply branch pipe 14 by the control of each pump (for example, inverter control). The pulsation cycles of the heat exchangers A _{1 to} A _N of the A group and the B _{1 to} B _N of the B group may be shifted by a half cycle. Such control is also performed by the control device C.

  In addition, as shown in FIG. 5, for example, a pair of two adjacent heat exchangers Z1, Z2,. . . Heat exchangers A1 and B1, A2 and B2. . . On the other hand, water is taken from the main pipe 12 through one intake pipe 21, and a branch type three-way valve 22 is provided in the intake pipe 21, and the supply branch pipes 14 and 14 connected to the three-way valve 22 are respectively connected to the intake pipe 21. Heat exchanger pair Z1, Z2. . . Heat exchangers A1, B1, A2, B2. . . You may make it connect to. Further, as shown in FIG. 6, the heat exchanger pairs Z1, Z2,. . . Heat exchangers A1 and B1, A2 and B2. . . These return branch pipes 15 may be joined together and returned to the return pipe 13 via the mixed three-way valve 22. By doing so, the flow rate distribution ratio (in the case of the shunt type in FIG. 5) or the mixing ratio (in the case of the mixed type in FIG. 6) or the mixing ratio (in the case of the mixed type in FIG. 6) is changed by controlling the opening degree of the three-way valve 22. Each heat exchanger pair Z1, Z2. . . The pulsation of the flow rate of the heat source liquid flowing in the two supply branch pipes 14 and 14 may be shifted periodically by shifting by half a cycle. Control of the three-way valve 22 is also performed by the control device C.

In the hot water supply system 1 described above, an example in which 2N units of the heat exchangers A _{1 to} A _N of the A group and B _{1 to} B _N of the B group, that is, an even number of heat exchangers is shown. In this regard, for example, in the case of an odd number, that is, when using 2N + 1 heat exchangers A _{1 to} A _{N + 1} of the A group and B _{1 to} B _N of the B group, the flow rates of the A group and the B group When the pulsation is alternately pulsated, the flow rate of the main pipe is not constant, and the flow rate is changed by the amount flowing through one supply branch pipe 14. However, if the number of N is sufficiently large (for example, 10 or more, more preferably 100 or more), this variation does not have a significant effect, so that the present invention can be applied even if it is an odd number. . Therefore, in the present invention, the present invention is applied even if “half by half” is not strictly the same.

  The present invention is useful when supplying a heat source liquid to a heat exchanger in the same multi-load connection type piping system.

1 hot water supply system 2 boiler 3,11 pump 12 shuttle 13 Kaekan 14 supply branch pipe 15 feedback branch pipe 16 a differential pressure gauge 21 intake pipe 22 three-way valve _{A 1 ~A N, B 1 ~B} N heat exchanger C controller MV Control valve P1-P5 position

Claims (5)

In a piping system in which a plurality of heat exchangers having the same configuration are connected in parallel to a main pipe through branch pipes and a heat source liquid is supplied to each heat exchanger by a pump.
The plurality of heat exchangers are divided into two groups of half, and the flow rate of the heat source liquid flowing in the branch pipes of each group is periodically changed to generate pulsation,
The method of supplying a heat source liquid, wherein the pulsation period is shifted by a half period between each group. The heat source liquid supply method according to claim 1, wherein the plurality of heat exchangers are arranged so that heat exchangers belonging to different groups are alternately arranged. The supply of the heat source liquid according to claim 1 or 2, wherein the flow rate of the heat source liquid flowing in the branch pipes is periodically changed by opening control of a flow rate adjusting valve provided in each branch pipe. Method. The method for supplying a heat source liquid according to claim 1 or 2, wherein the flow rate of the heat source liquid flowing in the branch pipes is periodically changed by control of an individual pump provided in each branch pipe. In periodically changing the flow rate of the heat source liquid flowing in the branch pipes, for a pair of adjacent two heat exchangers belonging to different groups,
Water is taken from the main pipe through one branch pipe,
A three-way valve is provided on the branch pipe,
Connect the other two pipes connected to the three-way valve to each heat exchanger of the heat exchanger pair,
The heat source liquid supply method according to claim 2, wherein the flow rate of the heat source liquid flowing through the two pipes is shifted by half a period and periodically changed by controlling the opening of the three-way valve.

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