JP2009068758A - Ice making method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the amount of water of 0°C or more supplied to an inner wall surface of a connection pipe functioned as a diffusion preventer, constant even when brine pressure is fluctuated by pulsation of a pump and the like when a gasket-type plate heat exchanger is applied as a supercooler. <P>SOLUTION: The gasket-type plate heat exchanger is operated in a state of adjusting differential pressure between plates of brine and water in advance in the supercooler 4. The differential pressure is the differential pressure between plates for making a resistance coefficient of a water flow channel in the supercooler 4 constant regardless of pressure fluctuation and flow rate fluctuation of the water or brine by adjusting a pressure of the brine flowing into the supercooler 4 in a state of circulating the water while setting the water and the brine to the flow rates necessary for making the supercooled water. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, a gasket type plate heat exchanger is used as a supercooler, brine and water are exchanged countercurrently to produce supercooled water, and the supercooled water is exposed to the atmosphere through a connecting pipe. The present invention relates to a method for producing ice without being sent to a closed supercooler.

In order to prevent the phase change when the supercooled state is released by the closed type releaser from propagating to the upstream side connection pipe, the applicant firstly connects the connection pipe that functions as a propagation preventing device. An ice production method was proposed in which a liquid film of water of 0 ° C. or higher was formed on the wall surface (Patent Document 1).
As a result, in the production of ice by releasing the supercooling by the so-called closed system, no special heating energy or special processing on the end surface of the connecting pipe is required, and the releaser can be stably connected to the connecting pipe for a long period of time. The propagation of the phase change could be prevented.

  In such a case, a separate water source is secured by branching from the introduction pipe connected to the inlet side of the supercooler, bypassing the supercooler, and being connected to the external container. In addition, the temperature of the water to be poured is suitable, or even if it is heated, an effect that only a small amount of heat is required can be obtained.

JP 2003-106716 A

  By the way, a gasket-type plate heat exchanger is used for the subcooler, and the water injection pipe is branched from the introduction pipe connected to the inlet side of the subcooler, bypassing the supercooler, and 0 ° C or more on the connecting pipe wall surface. When the water liquid film is formed, for example, when the pressure of the brine fluctuates, the plate may be displaced in accordance with the change in the pressure difference between the brine and the water (differential pressure between the plates).

  In the gasket type plate heat exchanger, in order to prevent mixing between two fluids (water and brine) and leakage to the outside, a gasket is used for the partition between the outer periphery of the plate and the two fluids. The gasket is crushed by tightening the end plate located at a position to obtain a predetermined sealing ability. Gaskets are usually designed so that a predetermined sealing ability can be exerted with a pressing force smaller than the pressing force with which the plate surfaces completely come into contact with each other, so that there is a gap between the plates (between peaks and valleys on the plate surface). ing. On the other hand, the plate used for a plate-type heat exchanger uses a very thin metal processed into a corrugated plate for the purpose of improving heat transfer.

  As described above, in a plate heat exchanger that employs a plate in which there is a gap between the plates and a thin metal is processed into a corrugated plate shape, for example, brine pressure or water is generated by pump pulsation or automatic valve opening / closing. When the pressure of the plate fluctuates, it is considered that the displacement occurs due to movement and deformation of the plate surface in response to the variation.

  And when the displacement of the plate occurs in this way, the flow rate of water (bypass flow rate) or bypass flow rate ratio (bypass flow rate and water flowing through the subcooler) that bypasses the plate heat exchanger and is supplied to the connecting pipe. The flow rate) changes.

  Such a change in the bypass flow rate may make the liquid film of water of 0 ° C. or higher formed on the inner wall surface of the connecting pipe unstable. That is, when the flow rate of the water flowing into the bypass pipe increases due to the fluctuation of the differential pressure between the plates, there is no actual damage to the operation, but when it decreases, 0 ° C. or higher should be formed on the downstream pipe inner wall. This is because the liquid film becomes unstable, and the upstream propagation suppression effect temporarily disappears. In addition, in the state of any differential pressure between plates within the range where displacement of the plate occurs, when the bypass flow rate is operated at a predetermined design flow rate, if the differential pressure between the plates becomes small, water easily flows into the subcooler. As a result, the bypass flow rate decreases and the predetermined design flow rate cannot be maintained.

  The present invention has been made in view of such points, and even when a gasket-type plate heat exchanger is employed as a subcooler, the amount of water of 0 ° C. or more supplied to the inner wall surface of the connecting pipe is reduced. The purpose is to maintain it constant so that the function as an anti-freezing propagation device can be stably exhibited.

  In order to achieve the above object, according to the present invention, a supercooling water is produced by exchanging heat between brine and water countercurrently using a gasket-type plate heat exchanger as a supercooler, and the supercooling is performed. When ice is produced by sending water through a connecting pipe to a closed supercooler without touching the atmosphere, the water is introduced into the supercooler at 0 ° C. or higher, that is, brine, and superheated. In the ice manufacturing method in which water at 0 ° C. or higher for manufacturing cooling water is partially branched and supplied to the inner wall surface of the connecting pipe by bypassing the supercooler, the plate heat exchanger An ice manufacturing method is provided, characterized in that the amount of water of 0 ° C. or higher supplied to the inner wall surface of the connecting pipe is kept constant by adjusting the differential pressure between the brine and water plates in advance. Is done.

  When producing supercooled water, the flow rate of water and brine is always maintained at a constant value by the regulator, so that the resistance coefficient and pressure loss of the plate heat exchanger are constant if there is no movement of the plate. However, as described above, since there is a gap between the plates, when the water side pressure is higher than the brine side pressure, the water side channel is widened and the brine side channel is narrowed. When the pressure on the side is higher than the pressure on the water side, the brine-side flow path is expanded to narrow the water-side flow path. According to the inventors' knowledge, if the absolute value of the differential pressure between the plates is not sufficiently large, the resistance coefficient of the plate heat exchanger changes depending on the differential pressure between the plates, and as a result, the pressure loss also changes. However, it has been found that there are places where the resistance coefficient is constant where the pressure difference between the plates is sufficiently large. Therefore, if the cooling brine or water pressure is adjusted to operate under such a differential pressure, the pressure loss can be kept constant, and even if the pressure fluctuation fluctuates during operation due to pump pulsation, etc. The deformation of the plate can be suppressed. Accordingly, the flow rate of water (bypass flow rate) and the bypass flow rate ratio (bypass flow rate to the flow rate of water flowing through the subcooler) supplied to the connecting pipe by bypassing the plate heat exchanger described above are maintained constant. It is possible.

  When adjusting the differential pressure as described above, for example, adjusting the pressure of the brine flowing into the plate heat exchanger in a state where water and brine are set to the flow rates necessary for the production of supercooled water and the water is circulated. And the resistance coefficient of the water flow path in the plate heat exchanger may be adjusted to the inter-plate differential pressure that is constant regardless of the pressure fluctuation or flow rate fluctuation of water or brine.

  And in adjusting the pressure difference between the brine and water plates in the plate heat exchanger in advance, the brine outlet pressure is made larger than the water inlet pressure to the plate heat exchanger, or the plate heat exchanger It can be proposed that the outlet pressure of water to be greater than the inlet pressure of the brine.

  The inventors have verified that, when heat is exchanged between water and brine in countercurrent, the outlet pressure of the brine is thus made larger than the inlet pressure of the water to the plate heat exchanger, or the plate type By making the outlet pressure of water to the heat exchanger larger than the inlet pressure of brine, the resistance coefficient of the water flow path in the plate heat exchanger can be changed regardless of pressure fluctuation or flow fluctuation of water or brine. It was found that the pressure difference between the plates was adjusted to be constant.

  In order to carry out such adjustment specifically, for example, a closed expansion tank is attached to the piping of the brine, and the static pressure of the brine is adjusted by adjusting the gas pressure in the closed expansion tank. Make the outlet pressure of the brine larger than the inlet pressure of the water to the cooler to exchange heat by countercurrent, or select the head of the brine pump to be larger than the rated flow and the resistance of the piping system. Adjusting the rated flow rate by restricting the valve installed at the brine outlet, the brine outlet pressure is made larger than the water inlet pressure to the supercooler, and heat is exchanged in countercurrent, or even the supercooler The supercooler installation position is manufactured by the supercooling water from the supercooler so that the outlet pressure of water is higher than the sum of the waterside pressure loss and the brine side loss pressure of the supercooler. As an example, it can be installed at a position lower than the water surface of the ice heat storage tank that stores the collected ice, and the water outlet pressure to the supercooler is made larger than the inlet pressure of the brine to exchange heat in countercurrent. .

  According to the present invention, when producing supercooled water using a plate heat exchanger, even if pressure fluctuation occurs for some reason in brine or water, the deformation of the plate is suppressed and the inner wall surface of the connecting pipe is suppressed. The amount of water supplied at 0 ° C. or higher can be maintained constant, and the function as a freeze propagation preventer can be stably exhibited.

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 shows an overview of an entire ice heat storage system in which an ice manufacturing method according to an embodiment is carried out, and after ice cores are completely removed by a preheating device 2 from water taken from an ice heat storage tank 1. The water is sent by the pump 3 to the supercooler 4 constituted by a plate heat exchanger. And the said water is heat-exchanged with the low temperature brine sent with the pump 6 from the refrigerator 5, and the water taken from the ice thermal storage tank 1 turns into 0 degreeC or less supercooled water.

  The supercooled water is converted into slurry-like ice water through the propagation preventing device 7, for example, by a closed supercooling release device 8, and returned to the ice heat storage tank 1 again. Ice water is separated from the specific gravity difference between ice and water in the ice heat storage tank 1. By repeating this cycle, the water in the ice heat storage tank 1 is converted to ice, and cold heat is stored. As the subcooler 4, a plate heat exchanger as shown in FIG. 2 is used.

  That is, the supercooler 4 has a structure in which a large number of plates 11 are laminated between end plates 13 and 14 at both ends with a gasket 12 in between, and the end portion of the shaft 15 penetrating the plate 11 and the gasket 12 is the end. They are integrated by tightening with nuts 16 from the outside of the plate 14. And the water from the water flow path 17 which penetrates the upper end vicinity of each plate 11 and the brine from the brine flow path 18 which penetrates the lower end vicinity of each plate 11 are in the space formed by each plate 11 and the gasket 12. The two flow alternately, and both are heat-exchanged via the plate 11.

  Next, the system around the subcooler 4 will be described with reference to FIG. For this supercooler 4, a water piping system 20 that circulates between the ice heat storage tank 1 and the supercooler 4, a brine piping system 30 that circulates between the refrigerator 5 and the supercooler 4, Is piped. In this example, heat is exchanged between brine and water by countercurrent.

  The water piping system 20 includes a connecting pipe 21 that forms a water outgoing pipe from the supercooler 4 through the propagation preventing device 7 to the supercooling release device 8, and ice that has been released from the supercooling state by the supercooling release device 8. -It has the ice conveyance pipe | tube 22 which conveys water slurry to the ice thermal storage tank 1. FIG. Further, the water piping system 20 has a water return pipe 23 and 23 which are directed to the supercooler 4 via the preheating device 2 and the pump 3 described above.

  The connecting pipe 21 is provided with a first pressure gauge 24 that measures the pressure at the outlet side of the cooling water from the supercooler 4 and the supercooling release device 8 described above. In addition to the preheating device 2 and the pump 3 described above, the water return pipe 22 is provided with a valve 25 and a flow meter 26 for measuring the flow rate of water. The flow rate of water measured by the flow meter 26 is output to the control device 29, and the control device 29 controls the valve 25 so that a predetermined flow rate value is obtained based on this.

  A bypass pipe 41 is provided between the propagation preventing device 7 and the water return pipe 23 in the water piping system 20, and the bypass pipe 41 includes a bypass flow meter 42 that measures the flow rate of water flowing through the bypass pipe 41, A valve 43 is provided. The bypass pipe 41 is made of a highly rigid material such as a steel pipe, a hard PVC pipe, a stainless steel pipe, or a copper pipe.

  As shown in FIG. 3, the connecting pipe 21 is divided at a right angle with respect to the axial direction so as to create a gap d in the outer container 45 covering the outer periphery of the connecting pipe 21 in an annular shape. It is divided into a pipe 21a and a downstream connecting pipe 21b. Therefore, when water is poured from the bypass pipe 41 into the outer container 45, the water that has entered the connecting pipe 21 from the gap d flows along the inner wall surface of the downstream connecting pipe 21b along the flow in the connecting pipe 21. The liquid film of the injected water is uniformly formed on the inner peripheral wall of the downstream connecting pipe 21b.

  The brine piping system 30 includes a brine forward pipe 31 from the subcooler 4 toward the refrigerator 5 and a brine return pipe 32 from the refrigerator 5 toward the supercooler 4. The brine outgoing pipe 31 is provided with a valve 33 and the pump 6 described above. The brine return pipe 32 is provided with a flow meter 35 for measuring the flow rate of the brine flowing into the subcooler 4 and a pressure gauge 36 for measuring the pressure on the inlet side of the brine flowing into the subcooler 4. An expansion tank 37 is provided in the piping between the pump 6 and the subcooler 4 in the brine outgoing pipe 31 (that is, on the suction side of the pump 6). The brine flow rate measured by the flow meter 35 is output to the control device 38, and the control device 38 controls the valve 33 so as to obtain a predetermined flow rate value based on the brine flow rate.

  The ice heat storage system shown in FIG. 1 has the above-described configuration. Next, how to obtain a differential pressure at a level at which the plate does not deform or move due to pressure fluctuation in this system will be described.

First, set the set values of the water and brine control devices 29 and 38 to the flow rates necessary for the production of supercooled water and brine, circulate the water, and operate the valve 25 to gradually increase the water flow rate. , ΔP (measured value of the pressure gauge 36−measured value of the pressure gauge 23) and the bypass flow meter when the differential pressure ΔP (that is, the difference between the brine pressure and the water pressure on both surfaces of each plate 11) is gradually reduced. 42 measurements _{(G 1)} and the flow meter 26 of the measuring values the relationship _{(G 2)} is recorded. The measurement results are plotted in a small circle on the graph of FIG. 4, and the curve based on the results is shown in FIG.

Left vertical axis of FIG. 4, after adjusting the _G 1 / _{G 2} to the rated flow rate _(G 10 / G ₂₎ in the right [Delta] P in FIG. _{(G 10} is rated flow of _{G 1)} went lowered, [Delta] P for _shows a decrease ratio of _{G 1 / G 2 {(G} 1 / G 2) / (G 10 / G 2)}. Here, since G ₂ (flow rate of water) is controlled to 700 L / min, the decreasing rate of G ₁ / G ₂ is expressed as “G ₁ / G ₁₀ ”.

According to this, the _G 1 _{/ G 10} In region (1) and the region (3) does not change, it can be seen that area (2) _{where G} 1 _{/ G 10} in conjunction with a change in the differential pressure is changed. This means that in the region (2), the plate in the subcooler 4 which is a plate heat exchanger moves and deforms as the differential pressure varies. From this, it can be seen that the operating pressure should be selected in the regions (1) and (3) in order to prevent the movement and deformation of the plate even if the pressure difference between the plates occurs.

  That is, in the range (ΔPmin to ΔPmax) of the region (2) in FIG. 4, the displacement of the plate (water channel width) changes according to the change in the inter-plate differential pressure ΔP, and the bypass flow rate ratio G1 / in FIG. G2 (the ratio of the flow rate G1 of water supplied to the connecting pipe 21 bypassing the supercooler 4 and the flow rate G2 of water flowing through the supercooler 4) changes. Such a change in G1 makes the liquid film of water at 0 ° C. or more formed on the inner wall surface of the connecting pipe 21 unstable. Now, when operating at a predetermined flow rate (a flow rate of about 2 to 3% of G2 as described above) in an arbitrary ΔP state within the range of region (2) in FIG. When becomes smaller, the flow path width of the water becomes larger and water easily flows into the subcooler 4, so that G1 decreases and the predetermined flow rate cannot be maintained.

  In order to prevent such a change in G1, even if ΔP changes in FIG. 4, ΔPw (pressure of water flowing into the subcooler 4) does not change (1) or region ( What is necessary is just to set the pressure of a brine and water so that a driving | running state can be limited within the range of 3), ie, below (DELTA) Pmin, or (DELTA) Pmax.

  The other method for determining the differential pressure between the plates described above is to observe the movement and deformation of the plate from the change in the flow rate ratio between the subcooler 4 and the bypass pipe 41 which are plate heat exchangers. In such a measurement system, the water flow path is connected in parallel with the subcooler 4 and the bypass pipe 41, but the plate heat exchanger constituting the subcooler 4 and the bypass flow path are separated by a plurality of throttles. When considered as a kind of constructed labyrinth flow path, each resistance coefficient ξ and loss head h is generally expressed by the following equation (1).

That is, h _i = a _i · ξ _i · v _i ² / 2g (1)
i = 1 (flow path of bypass pipe 41) or 2 (water side flow path of subcooler 4) (a: dimensionless constant (constant according to the shape of the flow path), v: flow velocity, g: gravitational acceleration) It is.
Therefore, the loss head h ₁ of the bypass pipe 41 is
h ₁ = a ₁ · ξ ₁ · v ₁ ² / 2g,
The head loss h ₂ water side flow passage of the subcooler 4,
h ₂ = a ₂ · ξ ₂ · v ₂ ² / 2g,
It becomes.

Further, assuming that the cross-sectional area and flow velocity of the inlet of the subcooler 4 and the bypass pipe 41 of the plate heat exchanger are v and A, respectively, the respective flow rates G are expressed by Expression (2).
G _i = v _i · A _i (2)
i = 1 (flow path of the bypass pipe 41) or 2 (water side flow path of the subcooler 4).
That is,
Flow rate _{G 1} of the bypass pipe 41,
G ₁ = v ₁ · A ₁
Flow rate G ₂ water side flow passage of the subcooler 4,
G ₂ = v ₂ · A ₂
It becomes.

In this measurement system, the loss heads of the subcooler 4 and the bypass pipe 41, which are plate heat exchangers, are always the same (h ₁ = h ₂ ). Therefore, from the equations (1) and (2), the equation (3 ) Is obtained.

  In addition, since the cross-sectional area of the inlet of the subcooler 4 of the plate heat exchanger and the inlet of the bypass pipe 41 is constant, b is a constant as shown in Expression (4).

Here, since the bypass pipe 41 is made of a highly rigid material, the resistance coefficient ξ ₁ does not change. For this reason, if G ₁ and G ₂ are measured, it is possible to detect a change in the resistance coefficient ξ ₂ accompanying the movement and deformation of the plate in the plate heat exchanger.
That is, the variation in the measurement of G ₁ and G ₂ is caused by the change in the resistance coefficient ξ ₂ , and the change in the resistance coefficient ξ ₂ is nothing but an indication that the plate is deformed or moved. Therefore, the differential pressure between the plates such that the resistance coefficient ξ ₂ shows a constant value is used as the operating condition of the subcooler 4, and then the ice storage system is operated in accordance with the differential operating condition. .

  In setting the above-described differential pressure between the plates, for example, by adjusting the gas pressure of the closed expansion tank 37 to adjust the static pressure of the brine, the outlet pressure of the brine is higher than the inlet pressure of the water to the subcooler 4. Or by selecting the head of the pump 6 larger than the rated flow rate and the resistance of the piping system, and adjusting the rated flow rate by restricting the valve installed at the brine outlet of the subcooler 4. It can be proposed that the brine outlet pressure be greater than the water inlet pressure for heat exchange. In addition, the installation position of the supercooler 4 is adjusted to store the ice temperature so that the outlet pressure of the water to the supercooler 4 is higher than the sum of the water-side loss pressure and the brine-side loss pressure of the supercooler 4. As an example, it can be installed at a position lower than the water surface of the tank 1 and the outlet pressure of the water with respect to the supercooler 4 is made larger than the inlet pressure of the brine to exchange heat by countercurrent.

  The present invention produces supercooled water using a gasket-type plate heat exchanger, and sends the supercooled water to a closed supercooler without touching the atmosphere through a connecting pipe to produce ice. Useful.

It is explanatory drawing which showed typically the outline | summary of the ice thermal storage system for implementing this invention. It is explanatory drawing which showed typically the structure of the gasket type plate-type heat exchanger used for the ice thermal storage system of FIG. 1, the figure of the left side shows the front, and the figure of the right side has shown the right side. It is a partial cross section side view which shows the mode of the inside of the connecting pipe used for the ice thermal storage system of FIG. It is a graph which shows the relationship between the brine outlet pressure-water inlet pressure in the supercooler of the ice thermal storage system of FIG. 1, water side pressure loss, and bypass flow rate / water flow rate of the subcooler.

Explanation of symbols

1 Ice storage tank 2, 6 Pump 4 Subcooler 5 Refrigerator 7 Propagation prevention device 7
8 Supercooling release device 11 Plate 12 Gasket 15 End plate 21 Connecting pipe 20 Water piping system 22 Water return pipe 24, 36 Pressure gauge 25, 33, 43 Valve 26, 35, 42 Flow meter 30 Brine piping system 31 Brine outgoing pipe 32 Brine return pipe 37 Expansion tank 41 Bypass pipe 42 Bypass flow meter 45 External container

Claims (3)

Using a gasket-type plate heat exchanger as the supercooler, brine and water are exchanged in countercurrent to produce supercooled water, and the supercooled water is sealed through the connecting pipe without being exposed to the atmosphere. When producing ice by sending it to the subcooler, the water at 0 ° C. or higher introduced into the supercooler is partially branched to bypass the supercooler and against the inner wall surface of the connecting pipe. In the ice manufacturing method to supply
The amount of water of 0 ° C. or higher supplied to the inner wall surface of the connecting pipe is kept constant by adjusting in advance the differential pressure between the brine and water plates in the plate heat exchanger. The ice manufacturing method. In pre-adjusting the differential pressure between the brine and water plates in the plate heat exchanger, the plate heat and water are circulated with the water and brine set to the flow rates required for the production of supercooled water. The pressure of the brine flowing into the exchanger is adjusted, and the resistance coefficient of the water flow path in the plate heat exchanger is adjusted to the inter-plate differential pressure that is constant regardless of the pressure fluctuation or flow rate fluctuation of water or brine. The method for producing ice according to claim 1. In pre-adjusting the differential pressure between the brine and water plates in the plate heat exchanger, the brine outlet pressure is made larger than the water inlet pressure to the plate heat exchanger, or the plate heat exchanger 2. The ice production method according to claim 1, wherein the water outlet pressure is larger than the brine inlet pressure.

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