Heat exchange device and control method for heat exchange between natural water source and heat exchange medium

Abstract

The present invention discloses a heat exchange device, which includes: an open tunnel structure, which has a slope formed along the length direction, and the slope drives natural water source water to flow therein; a plurality of tube-in-tube heat exchange units, which are arranged in the open tunnel structure along the length direction of the open tunnel structure, and heat exchange medium flows in the tubes; the heat exchange medium storage tank at the inlet end is respectively connected to each tube-in-tube heat exchange unit through an independent input pipeline to input heat exchange medium with the same temperature into each tube-in-tube heat exchange unit; each input pipeline is provided with a pump; the heat exchange medium storage tank at the outlet end is respectively connected to each tube-in-tube heat exchange unit through an independent output pipeline, and the heat exchange medium is output from each tube-in-tube heat exchange unit to the heat exchange medium storage tank at the outlet end; a heat pump system is respectively connected to the above two storage tanks; a control device is respectively connected to each pump to respectively control the heat exchange medium in each tube-in-tube heat exchange unit to have different flow rates. In addition, the present invention also discloses a control method for the above heat exchange device.

Description

Technical Field

[0001] The present invention relates to a heat exchange device and a control method, and in particular to a surface water heat exchange device and a control method. Background Art

[0002] As is known to all, the technical core of the surface water ground source heat pump system is the heat exchange between the natural water source and the heat exchange medium. In the prior art, for the surface water source off-body heat exchange system that extracts surface water source water body and exchanges heat in an independent natural water source and heat exchange medium heat exchange device, closed, standardized, miniaturized high-efficiency heat exchange equipment is usually used, and its common equipment includes: plate-type shell and tube heat exchange unit, shell and tube heat exchange unit, etc. When using plate-type shell and tube heat exchange unit and shell and tube heat exchange unit, it is usually selected to select a single or multiple shell and tube heat exchange unit, and the natural water source water and the heat exchange medium flow in the shell and tube heat exchange unit in the reverse direction. When using multiple shell and tube heat exchange units, the shell and tube heat exchange units are simply connected in parallel, that is, the natural water source water and the heat exchange medium flow in the reverse direction throughout the process.

[0003] In traditional heat exchange devices, the temperature of natural water source water gradually decreases from inlet to outlet, and the temperature of heat exchange medium gradually increases from inlet to outlet. Moreover, the temperature gradient of both along the direction of water flow from inlet to outlet is basically linear with distance, that is, the whole process is basically balanced intensity heat exchange, such as Figure 3 shown. Figure 3 The diagram schematically shows how the temperature of the heat exchange medium and natural water source water in a traditional heat exchange device changes with flow distance throughout the entire process.

[0004] In the existing traditional heat exchange device, the whole process is basically balanced intensity heat exchange. Balanced intensity heat exchange in the whole process means that the natural water source water and the heat exchange medium are basically in isothermal heat exchange during the whole process heat exchange, which makes the natural water source water at its corresponding outlet the lowest temperature, and the heat exchange medium at its corresponding inlet the lowest temperature. Assumption: The freezing point of natural water source water is 0℃, the temperature of the heat exchange medium at the inlet end of the heat exchange medium, that is, the outlet end of the natural water source water, is controlled at -10℃, and the temperature of the natural water source water at the outlet end of the natural water source water, that is, the inlet end of the heat exchange medium, is controlled at 4℃, and the heat exchange temperature difference in this area is 14℃; the temperature of the heat exchange medium at the outlet end of the heat exchange medium, that is, the inlet end of the natural water source water, is controlled at -4℃, and the temperature of the natural water source water at the outlet end of the natural water source water, that is, the inlet end of the heat exchange medium, is set at 10℃, and the heat exchange temperature difference in this area is also 14℃. Under this condition, at the inlet of the natural water source, although the heat exchange temperature difference is 14°C, the corresponding heat exchange medium is -4°C, and the lowest temperature of the heat exchanger wall, i.e., the natural water source heat exchange interface, is -4°C. The ability of the heat exchange interface to form phase change ice is very low. At the same time, the temperature of the natural water source reaches 10°C, that is, under this condition, the water-ice phase change will basically not occur at the heat exchange interface at the inlet of the natural water source; at the outlet of the natural water source, although the heat exchange temperature difference is also 14°C, but the corresponding heat exchange medium is -10°C, and the lowest temperature of the heat exchanger wall, i.e., the natural water source heat exchange interface, is -10°C. The ability of the heat exchange interface to form phase change ice is very strong. At the same time, the temperature of the natural water source is only 4°C, that is, under this condition, the water-ice phase change is very easy to occur at the heat exchange interface at the outlet of the natural water source.

[0005] Therefore, under the conditions of balanced intensity heat exchange between natural water source water and heat exchange medium in the whole process of traditional shell and tube heat exchange unit, the water-ice phase change first occurs at the outlet of natural water source water, and gradually extends to the inlet of natural water source water as the thickness of ice layer at the outlet of natural water source water increases. Moreover, in the process of extending to the inlet of natural water source water, it is very likely that the thickness of ice layer at the outlet of natural water source water has reached the level that can block the flow of natural water source water.

[0006] In addition, under the traditional full-process balanced intensity heat exchange conditions, the water-ice phase change in the heat exchange device mainly occurs at the outlet of the natural water source. The number of phase changes that can occur is limited, and the amount of phase change heat is very small, which has limited impact on the overall heating supply and cannot be used for peak-valley regulation. Moreover, the outlet of the natural water source is an area where water-ice phase change is extremely likely to occur. The heat exchange intensity of this area cannot be adjusted, which will become a bottleneck in determining the heat exchange intensity of the entire process of the heat exchange device.

[0007] If the heat exchange intensity can be increased in the high-temperature section of the natural water source water (the inlet of the natural water source water) until a controllable thickness of ice layer is produced on the wall of the tube heat exchange unit, the heat exchange of the low-temperature section of the natural water source water (the outlet of the natural water source water) can be reduced, that is, the heat exchange intensity can be reduced. Under low heat exchange intensity, the same heat exchange medium inlet temperature allows the natural water source water to be discharged at a lower temperature at the outlet, and the ice layer produced on the wall of the tube heat exchange unit does not block the normal flow of the natural water source water, that is, the thickness of the ice layer is also within the control range, and the temperature at the outlet of the natural water source water can be controlled at a lower temperature above the freezing point. If this control method is adopted, a water-ice phase change with controlled ice layer thickness can be produced in the entire process of heat exchange in the heat exchange device, and a huge number of phase changes can occur. The huge amount of phase change heat has a great impact on the overall heating supply and can be used for peak and valley regulation. The low outlet temperature of the natural water source water means that the heat energy that can be extracted from the natural water source water is increased.

[0008] Based on this, in order to overcome the defects in the above-mentioned prior art, under the guidance of the above-mentioned non-balanced intensity heat exchange theory, the inventor, from the perspective of engineering thinking, changed the heat exchange device between natural water source water and heat exchange medium in the surface water heat exchange system from equipment to component, and creatively designed a new heat exchange device for heat exchange between natural water source and heat exchange medium. The heat exchange device realizes the concept of non-balanced intensity heat exchange of natural water source water in the entire process from inlet to outlet. Summary of the invention

[0009] The object of the present invention is to provide a heat exchange device for heat exchange between a natural water source and a heat exchange medium, in which the whole process of the natural water source water from the inlet to the outlet is a non-balanced intensity heat exchange, which can control the flow rate and outlet temperature of the heat exchange medium delivered to each shell and tube heat exchange unit so that the temperature change gradient of the natural water source water during the heat exchange process is within a set range, and by controlling the temperature change gradient of the natural water source water, the outer wall surface of each shell and tube heat exchange unit produces controllable slight phase change freezing, and the thickness of the generated ice layer is controlled, so that the natural water source water can keep flowing forward when discharged near the freezing point, thereby achieving the maximum extraction of energy from the natural water source water.

[0010] In order to achieve the above object, the present invention proposes a heat exchange device for heat exchange between a natural water source and a heat exchange medium, which comprises:

[0011] An open tunnel structure having a slope formed along a length direction, wherein the slope drives natural water source water to flow in the open tunnel structure;

[0012] A plurality of tube-in-tube heat exchange units connected in parallel to each other are arranged in the open tunnel structure along the length direction of the open tunnel structure, and heat exchange medium flows in the tubes of the tube-in-tube heat exchange units;

[0013] The heat exchange medium storage tank at the inlet end is connected to each tube-in-tube heat exchange unit through an independent input pipeline to input heat exchange medium with the same temperature into each tube-in-tube heat exchange unit; each input pipeline is provided with a pump;

[0014] The heat exchange medium storage tank at the outlet end is connected to each tube-in-tube heat exchange unit through an independent output pipeline, and the heat exchange medium is output from each tube-in-tube heat exchange unit to the heat exchange medium storage tank at the outlet end;

[0015] A heat pump system, which is connected to the inlet end heat exchange medium storage tank and the outlet end heat exchange medium storage tank respectively;

[0016] The control device is connected to each pump to control the heat exchange medium in each tube heat exchange unit to have different flow speeds, so as to control the phase change ice within a set thickness range to be generated on the outer wall of each tube heat exchange unit.

[0017] In the above technical scheme of the present invention, the present invention provides an open structure heat exchange device including: an open tunnel structure, a plurality of tube-in-tube heat exchange units, an inlet heat exchange medium storage tank, an outlet heat exchange medium storage tank, a heat pump system and a control device to address the deficiencies in the prior art. The heat exchange device realizes the concept of non-balanced intensity heat exchange of natural water source water from the inlet to the outlet. In the present invention, the tube-in-tube heat exchange units are immersed in the natural water source water in the open tunnel structure in parallel, and the inlet heat exchange medium storage tank simultaneously transports the heat exchange medium to each tube-in-tube heat exchange unit through an independent input pipeline. After heat exchange in the open tunnel structure, the heat exchange medium is collected in the outlet heat exchange medium storage tank. The heat exchange medium in the two storage tanks is connected to the heat pump system to form a surface water source heat pump system.

[0018] The heat exchange device described in the present invention can control the flow rate and outlet temperature of the heat exchange medium in each tube-in-tube heat exchange unit, so that the outer wall surface of each tube-in-tube heat exchange unit can produce phase change ice with controllable thickness, control the amount of ice layer thickness generated, and overcome the increase in the flow resistance of natural water source water caused by ice formation only by increasing the pressure increase caused by the height difference of natural water source water at the inlet and outlet of the tunnel, so as to maintain stable and reliable operation of the heat exchange device described in the present invention.

[0019] In the heat exchange device described in the present invention, the natural water source water flows from the inlet of the open tunnel structure to the outlet of the open tunnel structure, and its temperature gradually decreases. Since the temperature of the heat exchange medium output by the heat exchange medium storage tank at the inlet end to each tube heat exchange unit is the same, the tube heat exchange unit close to the inlet of the open tunnel structure is in a condition of high natural water source water temperature and high temperature difference heat exchange (the temperature difference between the heat exchange medium and the natural water source water is large). At this time, the heat exchange device can control the pump through the control device to increase the speed of the heat exchange medium flowing in the tubes of the corresponding tube heat exchange unit, and use the method of increasing the flow speed of the heat exchange medium to perform high-intensity heat exchange until a phase change occurs on the outer wall of the tube heat exchange unit to form a thin ice layer. The tube heat exchange unit far away from the tunnel inlet of the open tunnel structure is in a condition of low natural water source water temperature and low temperature difference heat exchange. At this time, the heat exchange device can control the pump through the control device to reduce the speed of the heat exchange medium flowing in the tubes of the corresponding shell-and-tube heat exchange unit, and use the method of reducing the flow speed of the heat exchange medium to perform low-intensity heat exchange, which can also cause phase change on the outer wall of the corresponding shell-and-tube heat exchange unit to form a thin ice layer, thereby realizing non-balanced intensity extraction of heat energy in the entire tunnel.

[0020] It should be noted that, in the present invention, the comprehensive heat transfer coefficient K of the shell and tube heat exchange unit can be expressed as:

[0021]

[0022] In the above formula, σ represents the wall thickness of the shell and tube heat exchange unit, λ1 represents the thermal conductivity of the shell and tube heat exchange unit (depending on the material of the shell and tube heat exchange unit), σ w Indicates the thickness of the fouling layer on the wall of the shell and tube heat exchange unit, λ w Indicates the thermal conductivity of dirt (depends on the chemical properties of the dirt material). The above four parameters are physical quantities related to the material and thickness of the shell and tube heat exchange unit, and the water quality (affecting the thickness of the dirt layer on the wall of the shell and tube heat exchange unit and the chemical properties of the dirt material), and they remain basically unchanged after the heat exchange device is determined.

[0023] Accordingly, h f It represents the convective heat transfer coefficient of the heat transfer medium, h w It represents the convective heat transfer coefficient outside the shell and tube heat exchange unit (natural water source water), which is not only related to the characteristics of the natural water source water, but also closely related to the flow rate of the natural water source water.

[0024] Convective heat transfer coefficient h w The calculation is as follows (taking the outside of the shell and tube heat exchange unit as an example):

[0025]

[0026] In the above formula, λ w is the thermal conductivity of the natural fluid outside the shell-and-tube heat exchange unit, which is a parameter determined by the characteristics of the natural water source; d wis the equivalent diameter of the natural fluid flow outside the tube heat exchange unit. In the heat exchange device described in the present invention, this technology depends on the open tunnel structure. The smaller the cross-sectional area of ​​the natural water source flowing through the open tunnel structure, the smaller the cross-sectional area of ​​the natural water source flowing through the open tunnel structure. w The smaller h w The larger the open tunnel structure is, the greater the aspect ratio is. w The smaller it is, the corresponding natural water source water flow rate V w From this relationship, it can be seen that: w With V w Directly proportional.

[0027] The Reynolds number is a similarity criterion number that characterizes the effect of viscosity in fluid mechanics. The Reynolds number can be used to distinguish whether the flow of a fluid is laminar or turbulent. It can also be used to determine the resistance to the flow of an object in a fluid. The relevant parameters for calculating the Reynolds number are as follows:

[0028] In the above formula, μ w represents the dynamic viscosity of the natural fluid outside the shell and tube heat exchange unit; ρ w V represents the natural fluid density outside the shell and tube heat exchange unit; w Represents the natural fluid flow rate outside the shell and tube heat exchange unit.

[0029] μ w , w It is a parameter determined by the characteristics of natural water source, V w That is, the flow rate of natural water source water. In the heat exchange device described in the present invention, this technology depends on the open tunnel structure. The smaller the cross-sectional area of ​​the natural water source water flowing through the open tunnel structure, the larger the aspect ratio of the open tunnel structure is, and the larger the corresponding natural water source water flow rate is, that is, V w From this relationship, the actual result is: w With V w is proportional to the 0.8 power.

[0030] The Prandtl number is a dimensionless number (i.e., dimensionless parameter) composed of fluid physical parameters, indicating the relationship between the temperature boundary layer and the flow boundary layer, and reflecting the influence of the fluid physical properties on the convective heat transfer process. The relevant parameters for calculating the Prandtl number are as follows:

[0031] In the above formula, C w is the mass heat capacity of the natural water source outside the shell and tube heat exchange unit, μ w : Dynamic viscosity of the natural fluid outside the shell and tube heat exchange unit, λ w is the thermal conductivity of the natural fluid outside the shell-and-tube heat exchange unit, which is a parameter determined by the characteristics of the natural water source. From this relationship, it can be seen that: h wIt is proportional to the nth power of the Prandtl number, and the value of n is selected according to V w Closely positively correlated, V w The larger the n value, the higher the n value.

[0032] After the open tunnel structure, the heat exchange capacity of the natural water source water, i.e. the water volume of the natural water source and the temperature difference between the inlet and outlet, are determined, V w It is also determined that other parameters are all related to the characteristics of natural water source water, so the convective heat transfer coefficient on the outside of the shell and tube heat exchange unit (natural water source water) is also determined, that is, the heat exchange conditions on the natural water source water side cannot be controlled and adjusted by process.

[0033] Similarly, the convective heat transfer coefficient of the heat transfer medium h f It is also the flow velocity V of the heat exchange medium in the tubes. f The present invention is closely positively correlated. Each tube heat exchange unit is immersed in the natural water source water of the open tunnel structure in parallel, and each heat exchange medium is output by a water pump with frequency conversion control, so that the heat exchange conditions on the heat exchange medium side can be process controlled and adjusted. In particular, the parallel tube heat exchange units are located at different positions of the open tunnel structure and the corresponding natural water source water temperatures are different, so the medium temperature difference on both sides of the tube heat exchange unit wall is different, and the corresponding heat exchange conditions are different.

[0034] Therefore, by controlling the flow rate and outlet temperature of the heat exchange medium delivered to each shell and tube heat exchange unit, it can be ensured that the temperature change gradient of the natural water source water is within the set range. By controlling the temperature change gradient of the natural water source water, the entire process of the natural water source water is under a state of non-equilibrium intensity heat energy extraction. The wall surface of each shell and tube heat exchange unit produces controllable slight phase change freezing, and the thickness of the generated ice layer is controlled. The increase in the flow resistance of the natural water source water caused by freezing can be overcome only by increasing the pressure increase caused by the height difference of the natural water source water at the inlet and outlet of the tunnel, so as to achieve the goal of maintaining the forward flow of the natural water source water when it is discharged near the freezing point, thereby achieving the maximum extraction of energy from the natural water source water.

[0035] Furthermore, in the heat exchange device described in the present invention, the control device includes a variable frequency controller.

[0036] Furthermore, in the heat exchange device described in the present invention, the slope is ≤2%.

[0037] In the above technical solution of the present invention, the open tunnel structure in the heat exchange device of the present invention is provided with a natural slope. The potential energy difference formed by the natural slope as the power of natural flow should overcome the total resistance of the natural water source water flow resistance, dirt resistance, heat exchange wall ice resistance, etc. Therefore, in some embodiments, the slope can be preferably ≤2%. In addition, in order to increase the flow rate of natural water source water in the tunnel, in some embodiments, the open tunnel structure can adopt a high aspect ratio structure, and the aspect ratio of the open tunnel structure can be preferably controlled to be ≥50.

[0038] Furthermore, in the heat exchange device described in the present invention, the aspect ratio of the open tunnel structure is ≥50, and the aspect ratio is the ratio of the flow distance of natural water source water to the diameter of a circle of equal area converted to the effective cross-sectional area of ​​natural water source water.

[0039] Furthermore, in the heat exchange device described in the present invention, the shell and tube heat exchange unit includes a plurality of tube rows arranged in parallel and / or in series, and each tube row includes a plurality of tube rows arranged parallel to each other or a plurality of tube sections parallel to each other formed by bending a single tube.

[0040] In some embodiments, the shell-and-tube heat exchange unit may be formed by a plurality of tube banks connected in series, or may be formed by a plurality of tube banks connected in parallel. In other embodiments, a plurality of tube banks may be connected in series to form a tube bank group, and then a plurality of tube bank groups may be connected in parallel to form a shell-and-tube heat exchange unit. Alternatively, a plurality of tube banks may be connected in parallel to form a tube bank group, and then a plurality of tube bank groups may be connected in series to form a shell-and-tube heat exchange unit.

[0041] Furthermore, the heat exchange device of the present invention further comprises a plurality of first temperature detectors which are arranged along the length direction of the open tunnel structure to respectively detect the temperature change state of the water flowing in the open tunnel structure.

[0042] Furthermore, the heat exchange device of the present invention also includes a second temperature detector and a third temperature detector, which respectively detect the temperature of the heat exchange medium output from the inlet heat exchange medium storage tank and the temperature of the heat exchange medium input to the outlet heat exchange medium storage tank.

[0043] Correspondingly, another object of the present invention is to provide a control method for the above-mentioned heat exchange device, which is implemented based on the above-mentioned heat exchange device of the present invention and is used to control the above-mentioned heat exchange device.

[0044] In order to achieve the above object, the present invention proposes a control method for the above heat exchange device, which comprises the steps of:

[0045] Set the temperature drop gradient of natural water source water from the entrance to the exit of the open tunnel structure;

[0046] The control device controls each pump to control the heat exchange medium in each tube heat exchange unit to have different flow speeds, thereby achieving a set temperature drop gradient and causing phase change ice within a set thickness range to form on the outer wall of each tube heat exchange unit.

[0047] Furthermore, in the control method of the heat exchange device described in the present invention, the temperature drop gradient of the natural water source water is set to be nonlinear.

[0048] Furthermore, in the control method of the heat exchange device described in the present invention, the flow rate of the heat exchange medium in the shell and tube heat exchange unit at the entrance of the open tunnel structure is higher than the flow rate of the heat exchange medium in the shell and tube heat exchange unit in the middle section of the open tunnel structure, and the flow rate of the heat exchange medium in the shell and tube heat exchange unit in the middle section is higher than the flow rate of the heat exchange medium in the shell and tube heat exchange unit at the exit of the open tunnel structure.

[0049] The heat exchange device and control method for heat exchange between a natural water source and a heat exchange medium described in the present invention have the following advantages and beneficial effects compared with the prior art:

[0050] In the heat exchange device for heat exchange between a natural water source and a heat exchange medium described in the present invention, the entire process of the natural water source water flow from the inlet to the outlet is a non-balanced intensity heat exchange, which controls each pump through a control device to respectively control the heat exchange medium in each shell and tube heat exchange unit to have different flow rates, so as to generate phase change ice within a set thickness range on the outer wall of each shell and tube heat exchange unit.

[0051] The heat exchange device described in the present invention can effectively control the heat exchange intensity of each area, so that the outer wall surface of each tube heat exchange unit can produce a controllable phase change to form an ice layer of a certain thickness. The resistance caused by the thickness of the ice layer can be overcome only by relying on the water potential energy difference of the natural water source in the open tunnel structure. The outer wall surface of each tube heat exchange unit in the entire tunnel can produce a controllable phase change, that is, a huge amount of phase change heat is generated. The huge amount of phase change heat has a great influence on the overall heating and can be used to adjust the peak and valley of heating.

[0052] In addition, in certain embodiments, under the condition of a certain total heat exchange amount, the tube heat exchange unit in the area near the natural water source water inlet is in a high natural water source water temperature and high temperature difference heat exchange condition; when the natural water source water and the heat exchange medium are in a high temperature difference heat exchange interval, the control device can control the pump set on the input pipeline here to moderately increase the flow rate of the heat exchange medium in the corresponding tube heat exchange unit, and use a high-intensity heat exchange method to extract more heat. Correspondingly, the tube heat exchange unit in the area near the natural water source water outlet only needs to extract a small amount of heat, that is, low-intensity heat exchange is used. Although the natural water source water temperature in the natural water source water outlet area is low, due to the use of a low-intensity heat exchange method, it can make the outer wall of the tube heat exchange unit only produce a slight phase change and only form a thin ice layer or no ice layer, thereby ensuring the reliable operation of the heat exchange device. Alternatively, if the area near the natural water source water outlet produces an ice layer with the same thickness as the heat energy balanced intensity extraction in the entire tunnel, the natural water source water outlet area is allowed to have a lower natural water source water temperature, that is, the total heat exchange capacity is improved, and the natural water source water can even be discharged near the freezing point, thereby achieving the maximum extraction of natural water source water energy.

[0053] Correspondingly, the control method of the heat exchange device for heat exchange between a natural water source and a heat exchange medium described in the present invention is implemented based on the above-mentioned heat exchange device, which also has the above-mentioned advantages and beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 The heat exchange flow chart of the heat exchange device according to one embodiment of the present invention is schematically shown.

[0055] Figure 2 A schematic diagram showing the temperature variation of the heat exchange medium and natural water source water in the traditional heat exchange device with the flow distance throughout the entire process.

[0056] Figure 3 The schematic diagram schematically shows the temperature change of the heat exchange medium and natural water source water in the heat exchange device of the present invention with the flow distance in the whole process. DETAILED DESCRIPTION

[0057] The heat exchange device and control method for heat exchange between a natural water source and a heat exchange medium described in the present invention will be further explained and illustrated below in conjunction with the drawings and specific embodiments of the specification. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0058] Figure 1 The heat exchange flow chart of the heat exchange device according to one embodiment of the present invention is schematically shown.

[0059] like Figure 1As shown, in this embodiment, the heat exchange device of the present invention may include: an open tunnel structure 1, a tube heat exchange unit 2, an inlet heat exchange medium storage tank 3, an outlet heat exchange medium storage tank 4, a heat pump system 5 and a control device (not shown in the figure). The open tunnel structure 1 in the heat exchange device has a slope formed along the length direction, and the slope can drive the natural water source water to flow in the open tunnel structure 1. The natural water source water can enter the tunnel from the open tunnel structure inlet 11 and flow out from the open tunnel structure outlet 12.

[0060] In the heat exchange device described in the present invention, the shell-and-tube heat exchange units 2 are arranged in the open tunnel structure 1 along the length direction of the open tunnel structure 1, and heat exchange medium flows inside the shells of the shell-and-tube heat exchange units 2; the inlet end heat exchange medium storage tank 3 is respectively connected to each shell-and-tube heat exchange unit 2 through an independent input pipeline 31 to input heat exchange medium with the same temperature into each shell-and-tube heat exchange unit 2; wherein each input pipeline 31 is provided with a pump 32; the outlet end heat exchange medium storage tank 4 is respectively connected to each shell-and-tube heat exchange unit 2 through an independent output pipeline 41, and the heat exchange medium is output from each shell-and-tube heat exchange unit 2 to the outlet end heat exchange medium storage tank 4; the heat pump system 5 is respectively connected to the above-mentioned inlet end heat exchange medium storage tank 3 and the outlet end heat exchange medium storage tank 4; the control device is respectively connected to each pump 32 to respectively control the heat exchange medium in each shell-and-tube heat exchange unit 2 to have different flow speeds, so as to generate phase change ice within a set thickness range on the outer wall of each shell-and-tube heat exchange unit 2.

[0061] It can be seen that the pumps 32 provided on each input pipe can drive the flow of the heat exchange medium in the tube-in-tube heat exchange units 2 connected in parallel with each other under the control of the control device, and the tube-in-tube heat exchange units 2 rely on the pump 32 to drive the circulating heat exchange medium to exchange heat with the natural water source water flowing naturally outside the tube-in-tube heat exchange unit 2. Among them, the tube-in-tube heat exchange unit 2 in the heat exchange device can be provided with a plurality of tube-in-tube heat exchange units 2 according to the needs of the specific actual situation. In some embodiments, the control device of the present invention can use a variable frequency controller.

[0062] In the present invention, the heat exchange medium output from the heat exchange medium storage tank 3 at the inlet end to each shell-and-tube heat exchange unit 2 is controlled by each water pump 32 controlled by the control device. The water pump 32 can control the flow rate of the heat exchange medium in the shell-and-tube heat exchange unit 2 to be different, which will cause the intensity of heat energy extracted from the natural water source water by each shell-and-tube heat exchange unit 2 to be different. The shell-and-tube heat exchange unit 2 with a high heat exchange medium flow rate has a high heat energy extraction intensity, and the shell-and-tube heat exchange unit 2 with a low heat exchange medium flow rate has a low heat energy extraction intensity. In the heat exchange device described in the present invention, the heat exchange temperature difference between the heat exchange medium in each shell-and-tube heat exchange unit 2 and the natural water source water is different, and the whole process of the natural water source water presents a state of non-balanced intensity heat energy extraction.

[0063] Under the state of non-balanced intensity heat energy extraction of the whole process of natural water source water, increasing the flow rate of the heat exchange medium in each shell-and-tube heat exchange unit 2 or reducing the input temperature of the heat exchange medium can increase the heat extraction of the natural water source water by the shell-and-tube heat exchange unit 2, so that the outer wall of each shell-and-tube heat exchange unit 2 produces phase change ice with controllable thickness. The huge water-ice phase change heat generated by the outer wall of all the tubes in the heat exchange device can be extracted, and used to buffer the insufficient heat supply of the circulating water body when the heat exchange device is at the peak of heating; when the heat exchange device is at the low point of heating, the reverse operation is performed to reduce the heat extraction of the natural water source water by the shell-and-tube heat exchange unit 2, and ice-water phase change occurs, resulting in thinning or even elimination of the ice layer, thereby reserving ice layer growth space, i.e., heating buffer capacity, for the next heating peak, thereby realizing heating peak and valley buffering and regulation.

[0064] At the same time, in the device described in the present invention, the thickness of the phase change ice produced by the natural water source water on the outer wall surface of each shell and tube heat exchange unit in the whole process is controllable, which can ensure that the natural water source water maintains a smooth flow when discharged near the freezing point, thereby achieving the maximum extraction of the energy of the natural water source water.

[0065] It should be noted that, in the heat exchange device of the present invention, a plurality of first temperature detectors (not shown in the figure) may be provided along the length direction of the open tunnel structure 1 to respectively detect the temperature change state of the water flowing in the open tunnel structure 1. Of course, in some embodiments, the heat exchange device of the present invention may further include a second temperature detector (not shown in the figure) and a third temperature detector (not shown in the figure), which may respectively detect the temperature of the heat exchange medium output from the heat exchange medium storage tank 3 at the inlet end and the temperature of the heat exchange medium input to the heat exchange medium storage tank 4 at the outlet end.

[0066] In the heat exchange device described in the present invention, the heat exchange device described in the present invention adopts a wide gap flow method for natural water source water, and the gap for the natural water source water to flow through the open tunnel structure 1 is no longer narrow, which can ensure the safety and reliability of system operation. The tunnel adopts an open structure design because: the open structure can not only realize manual or mechanical online dredging, cleaning moss, and knocking out adsorbed shell molluscs, but also allow the water level to fluctuate up and down to overcome resistance fluctuations.

[0067] It should be noted that the open tunnel structure in the heat exchange device described in the present invention can be a civil construction structure of a concrete structure. In some embodiments, in order to reduce the flow resistance, the inner side of the open tunnel structure can be smoothed and a smooth layer can be attached to its surface. The attached smooth layer can be a plate layer, a stainless steel plate layer and a paint layer.

[0068] In addition, it should be noted that in this embodiment, the open tunnel structure 1 in the heat exchange device of the present invention is provided with a natural slope. The potential energy difference formed by the natural slope as the power of natural flow should overcome the total resistance of the natural water source water flow resistance, dirt resistance, heat exchange wall ice resistance, etc. Therefore, in some embodiments, the slope can be preferably ≤2%. In addition, in order to increase the flow rate of natural water source water in the tunnel, in some embodiments, the open tunnel structure 1 can adopt a high aspect ratio structure, and the aspect ratio of the open tunnel structure can be preferably controlled to be ≥50, where the aspect ratio is the ratio of the flow distance of natural water source water to the diameter of the equal area circle converted to the effective cross-sectional area of ​​natural water source water.

[0069] Accordingly, in the present invention, the shell-and-tube heat exchange unit 2 described in the present invention may include a plurality of tube rows arranged in parallel and / or in series, and each tube row includes a plurality of tubes arranged in parallel to each other or a plurality of tube sections parallel to each other formed by bending a single tube.

[0070] In some embodiments, the shell-and-tube heat exchange unit 2 may be formed by a plurality of tube banks connected in series, or may be formed by a plurality of tube banks connected in parallel. In other embodiments, a plurality of tube banks may be connected in series to form a tube bank group, and then a plurality of tube bank groups may be connected in parallel to form the shell-and-tube heat exchange unit 2. Alternatively, a plurality of tube banks may be connected in parallel to form a tube bank group, and then a plurality of tube bank groups may be connected in series to form the shell-and-tube heat exchange unit 2.

[0071] Continue reading Figure 1 It can be seen that when using the heat exchange device described in the present invention, the temperature drop gradient of natural water source water entering the tunnel from the open tunnel structure inlet 11 and flowing out from the open tunnel structure outlet 12 can be preset in advance, and then the pump 32 set on each input pipe 31 is controlled by the control device in the heat exchange device to respectively control the heat exchange medium in each shell and tube heat exchange unit 2 to have different flow speeds, thereby achieving the set temperature drop gradient and causing phase change ice to form on the outer wall of each shell and tube heat exchange unit 2.

[0072] In the heat exchange device of the present invention, the temperature of the natural water source water gradually decreases during the process of entering the tunnel from the open tunnel structure inlet 11 and flowing out from the open tunnel structure outlet 12. Near the natural water source water entering the open tunnel structure inlet 11, the temperature of the natural water source water is relatively high, and the natural water source water and the heat exchange medium are in a high temperature difference heat exchange range, which is a high-intensity heat exchange condition; near the natural water source water leaving the open tunnel structure inlet 11, the temperature of the natural water source water is relatively low, and the natural water source water and the heat exchange medium are in a low temperature difference heat exchange range, which is a low-intensity heat exchange condition.

[0073] For example, Figure 1As shown, assuming that the open tunnel structure 1 is 54 meters long, a tube heat exchange unit 2 is arranged every 18 meters, and the first tube heat exchange unit, the second tube heat exchange unit and the third tube heat exchange unit are arranged from left to right. The total temperature drop of the natural water source water is set to 9°C. After the heat exchange device of the present invention is used to perform the non-equilibrium intensity heat energy extraction method, the heat energy extraction intensity gradually decreases from the first tube heat exchange unit to the third tube heat exchange unit. For example, the temperature drop of the first tube heat exchange unit near the inlet 11 of the open tunnel structure may be 4.5°C, corresponding to the high temperature difference heat exchange interval, that is, the high intensity heat energy extraction interval; the temperature drop of the third tube heat exchange unit near the outlet 12 of the open tunnel structure may be 1.5°C, corresponding to the low temperature difference heat exchange interval, that is, the low intensity heat energy extraction interval.

[0074] When the natural water source water and the heat exchange medium are in the high temperature difference heat exchange zone, the control device can control the pump 32 set on the input pipe 31 here to moderately increase the flow rate of the heat exchange medium in the corresponding shell and tube heat exchange unit 2, that is, to increase the Reynolds number of the heat exchange medium in the shell and tube heat exchange unit 2, improve the heat exchange intensity, reduce the residence time of the heat exchange medium in the shell and tube, increase the total flow rate, obtain more heat exchange, and also cause phase change ice to form on the outer wall of each shell and tube heat exchange unit 2.

[0075] When the natural water source water and the heat exchange medium are in the low temperature difference heat exchange interval, although the temperature of the natural water source water is low, it is not necessary to extract too much heat, and a low-intensity heat energy extraction method can be used. The control device can control the pump 32 set on the input pipe 31 here to moderately reduce the circulation speed of the heat exchange medium, that is, reduce the Reynolds number of the heat exchange medium in the tube-and-tube heat exchange unit 2, and reduce the heat exchange intensity. Under the condition that the inlet and outlet temperature difference of the heat exchange medium of each tube-and-tube heat exchange unit 2 is basically the same, the residence time of the heat exchange medium can be controlled to increase and the total flow rate can be reduced to obtain less heat exchange. The outer wall of each tube-and-tube heat exchange unit 2 can be controlled not to undergo high-intensity phase change to produce a thick ice layer, but only to undergo low-intensity phase change to produce an ice layer of controllable thickness, that is, the near-freezing point discharge of the natural water source water can be achieved, and it can be ensured that the ice on the outer wall surface of the tube-and-tube heat exchange unit 2 near the outlet of the natural water source water will not block the circulation of the natural water source water, thereby achieving the maximum extraction of the energy of the natural water source water.

[0076] Figure 2 A schematic diagram showing the temperature variation of the heat exchange medium and natural water source water in the traditional heat exchange device with the flow distance throughout the entire process.

[0077] Figure 3 The schematic diagram schematically shows the temperature change of the heat exchange medium and natural water source water in the heat exchange device of the present invention with the flow distance in the whole process.

[0078] Combination Figure 2 and Figure 3It can be seen that in the existing traditional heat exchange device, the temperature of the natural water source water gradually decreases from the natural water source water inlet to the natural water source water outlet, and the temperature of the heat exchange medium gradually increases from the heat exchange medium inlet to the heat exchange medium outlet, and both flow along the movement direction from their respective inlets to outlets, and their temperature change gradient basically shows a linear relationship with distance, that is, the whole process is basically balanced intensity heat exchange.

[0079] In the heat exchange device described in the present invention, the entire process of the natural water source water flowing from the open tunnel structure inlet 11 to the open tunnel structure outlet 12 is a non-balanced intensity heat exchange, and the set temperature drop gradient of the natural water source water is nonlinear. It can control the flow rate and outlet temperature of the heat exchange medium delivered to each shell and tube heat exchange unit 2 so that the temperature change gradient of the natural water source water during the heat exchange process is in a set range. By controlling the temperature change gradient of the natural water source water, controllable slight phase change freezing is generated on the outer wall of each shell and tube heat exchange unit 2.

[0080] For example: the heat exchange interface of the shell and tube heat exchange unit is set to a smooth aluminum alloy plate, the high temperature side is natural water source water with a temperature greater than 0°C, and the low temperature side is antifreeze with a temperature less than 0°C. Under this heat exchange condition, the natural water source water side will produce phase change ice on the aluminum alloy plate (i.e., on the outer wall of the shell and tube heat exchanger unit), and the thickness of the ice layer depends on the temperature difference between the natural water source water and the antifreeze, the temperature of the antifreeze, and the flow rate of the heat exchange medium on both sides of the aluminum alloy plate.

[0081] To simplify the condition setting: the natural water source is set as pure water, with a flow rate of 1m / s and a freezing point of 0℃; the antifreeze temperature is an alcohol-containing aqueous solution at -10℃. The thickness of the ice layer formed on the wall of the heat exchanger on the natural water source side is tested at different natural water source temperatures and antifreeze flow rates, as shown in Table 1.

[0082] Table 1 shows the thickness of the ice layer formed on the wall of the heat exchanger on the natural water source side at different natural water source temperatures and antifreeze flow rates.

[0083] Table 1.

[0084] Natural water source temperature (℃) 10 8 6 4 2 Antifreeze flow rate 1m / s, ice thickness (mm) 0.02 0.1 0.2 0.6 1 Antifreeze flow rate 2m / s, ice thickness (mm) 0.1 0.3 0.4 1 1.4 Antifreeze flow rate 3m / s, ice thickness (mm) 0.2 0.6 1 2 3

[0085] It can be seen from Table 1 that when the antifreeze flow rate is 1 m / s, the natural water source temperature is 4°C, which is the same as the ice thickness calculated when the antifreeze flow rate is 3 m / s and the natural water source temperature is 8°C.

[0086] In the present invention, the control method of the heat exchange device of the present invention specifically includes the following steps:

[0087] Step (1): setting a temperature drop gradient of natural water source water from the entrance to the exit of the open tunnel structure;

[0088] Step (2): The control device controls each pump to control the heat exchange medium in each shell-and-tube heat exchange unit to have different flow rates, thereby achieving a set temperature drop gradient and causing phase change ice to form on the outer wall of each shell-and-tube heat exchange unit.

[0089] It should be noted that, in the heat exchange device of the present invention, the comprehensive heat exchange coefficient K of the shell and tube heat exchange unit can be expressed as:

[0090]

[0091] In the above formula, σ represents the wall thickness of the shell and tube heat exchange unit, λ1 represents the thermal conductivity of the shell and tube heat exchange unit (depending on the material of the shell and tube heat exchange unit), σ w Indicates the thickness of the fouling layer on the wall of the shell and tube heat exchange unit, λ w Indicates the thermal conductivity of dirt (depends on the chemical properties of the dirt material). The above four parameters are physical quantities related to the material and thickness of the shell and tube heat exchange unit, and the water quality (affecting the thickness of the dirt layer on the wall of the shell and tube heat exchange unit and the chemical properties of the dirt material), and they remain basically unchanged after the heat exchange device is determined.

[0092] Accordingly, h f Indicates the convective heat transfer coefficient of the heat transfer medium, h w It represents the convective heat transfer coefficient outside the shell and tube heat exchange unit (natural water source water), which is not only related to the characteristics of the natural water source water, but also closely related to the flow rate of the natural water source water.

[0093] Similarly, the convective heat transfer coefficient h w The calculation is as follows (taking the outside of the shell and tube heat exchange unit as an example):

[0094]

[0095] In the above formula, λ w is the thermal conductivity of the natural fluid outside the shell-and-tube heat exchange unit, which is a parameter determined by the characteristics of the natural water source; d w is the equivalent diameter of the natural fluid flow outside the shell and tube heat exchange unit. In the heat exchange device described in the present invention, this technology depends on the open tunnel structure. The smaller the cross-sectional area of ​​the natural water source flowing through the open tunnel structure, the smaller the cross-sectional area of ​​the natural water source flowing through the open tunnel structure. w The smaller h w The larger the open tunnel structure is, the greater the aspect ratio is. w The smaller it is, the corresponding natural water source water flow rate V w From this relationship, the actual result is: w With V w Directly proportional.

[0096] The Reynolds number is a similarity criterion number that characterizes the effect of viscosity in fluid mechanics. The Reynolds number can be used to distinguish whether the flow of a fluid is laminar or turbulent. It can also be used to determine the resistance to the flow of an object in a fluid. The relevant parameters for calculating the Reynolds number are as follows:

[0097] In the above formula, μ w represents the dynamic viscosity of the natural fluid outside the shell and tube heat exchange unit; ρ w V represents the natural fluid density outside the shell and tube heat exchange unit; w Represents the natural fluid flow rate outside the shell and tube heat exchange unit.

[0098] μ w , w It is a parameter determined by the characteristics of natural water source, V w That is, the flow rate of natural water source water. In the heat exchange device described in the present invention, this technology depends on the open tunnel structure. The smaller the cross-sectional area of ​​the natural water source water flowing through the open tunnel structure, the larger the aspect ratio of the open tunnel structure is, and the larger the corresponding natural water source water flow rate is, that is, V w From this relationship, the actual result is: w With V w is proportional to the 0.8 power.

[0099] The Prandtl number is a dimensionless number (i.e., dimensionless parameter) composed of fluid physical parameters, indicating the relationship between the temperature boundary layer and the flow boundary layer, and reflecting the influence of the fluid physical properties on the convective heat transfer process. The relevant parameters for calculating the Prandtl number are as follows:

[0100] In the above formula, C w is the mass heat capacity of the natural water source outside the shell and tube heat exchange unit, μ w represents the dynamic viscosity of the natural fluid outside the shell and tube heat exchange unit, λ w is the thermal conductivity of the natural fluid outside the shell-and-tube heat exchange unit, which is a parameter determined by the characteristics of the natural water source. From this relationship, it can be seen that: h w It is proportional to the nth power of the Prandtl number, and the value of n is selected according to V w Closely positively correlated, V w The larger the n value, the higher the n value.

[0101] After the open tunnel structure, the heat exchange capacity of the natural water source water, i.e. the water volume of the natural water source and the temperature difference between the inlet and outlet, are determined, V w It is also determined that other parameters are all related to the characteristics of natural water source water, so the convective heat transfer coefficient on the outside of the shell and tube heat exchange unit (natural water source water) is also determined, that is, the heat exchange conditions on the natural water source water side cannot be controlled and adjusted by process.

[0102] Similarly, the convective heat transfer coefficient of the heat transfer medium h f It is also the flow velocity V of the heat exchange medium in the tubes. f The heat exchange units of the present invention are immersed in the natural water source of the open tunnel structure in parallel, and each heat exchange medium is output by a water pump with frequency conversion control, so that the heat exchange conditions on the heat exchange medium side can be controlled and adjusted. In particular, the parallel heat exchange units are located at different positions of the open tunnel structure and the corresponding natural water source water temperatures are different, so the medium temperature difference on both sides of the wall of the heat exchange unit is different, and the corresponding heat exchange conditions are different.

[0103] The temperature of the natural water source water at the entrance of the open tunnel structure is high, and the heat exchange power between the natural water source water and the heat exchange medium is large, which can obtain a greater heat exchange speed and heat exchange amount. The heat exchange medium inlet temperature below the freezing point of the natural water source water leads to a low temperature on the outer wall of the tube heat exchange unit, so that an ice layer formed by the natural water source water will be generated on the outer wall of the tube heat exchange unit on the side of the natural water source water. In the same case, the higher the heat exchange intensity, the thicker the ice layer, but the high-temperature natural water source water can also effectively suppress the thickness of the ice layer under high-intensity heat exchange conditions. Using a high-flow rate heat exchange medium for heat exchange at the entrance of the open tunnel structure, on the one hand, effectively utilizes the favorable conditions of the high-temperature natural water source water and extracts more heat energy. On the other hand, even if high-intensity heat exchange conditions are used, the high-temperature natural water source water effectively suppresses the thickness of the ice layer, which can ensure that the water flow channel resistance is within the allowable range.

[0104] High-intensity heat exchange conditions are used on the inlet side of the natural water source water to extract more heat energy. Under the premise of maintaining a certain amount of heat exchange, the heat exchange required on the outlet side of the natural water source water can be reduced. On the one hand, the low temperature on the outlet side of the natural water source water reduces the heat exchange power between the natural water source water and the heat exchange medium, and it is impossible to obtain the same heat exchange speed and heat exchange as the inlet side. Furthermore, the lower heat exchange demand in this area allows the heat exchange medium to exchange heat at a lower heat exchange intensity. Therefore, the use of low-flow heat exchange medium on the inlet side of the natural water source water effectively avoids the unfavorable conditions of low-temperature natural water source water, and only extracts a small amount of heat energy. On the other hand, low-temperature natural water source water cannot suppress the formation of ice on the natural water source water side of the outer wall of the shell-and-tube heat exchange unit, but the use of low-intensity heat exchange conditions can also suppress the growth of ice thickness, so that the water flow channel resistance formed by the ice thickness is within the allowable range.

[0105] The above analysis is a concept of non-balanced intensity heat exchange for the entire process of natural water source water from inlet to outlet proposed by the present invention. Therefore, by controlling the flow rate and outlet temperature of the heat exchange medium delivered to each tube heat exchange unit, it can be ensured that the temperature gradient of the natural water source water is in the set range. By controlling the temperature gradient of the natural water source water, the entire process of the natural water source water is in a non-balanced intensity heat energy extraction state. The wall surface of each tube heat exchange unit produces controllable slight phase change freezing, and the thickness of the generated ice layer is controlled. The increase in the flow resistance of the natural water source water caused by freezing can be overcome only by increasing the pressure increase caused by the height difference of the natural water source water at the inlet and outlet of the tunnel, so that the natural water source water can keep flowing smoothly when discharged near the freezing point, and the maximum extraction of the energy of the natural water source water can be achieved.

[0106] Compared with the prior art, the present invention follows the concept of non-equilibrium intensity heat exchange in the whole process. The whole process of natural water source water from the inlet of the open tunnel structure to the outlet of the open tunnel structure is divided into several sections by the parallel tube heat exchange units. Under the conditions of natural water source water flow rate, unit time, unit heat exchange area, and the same heat exchange capacity, the large open tunnel structure of the immersed tube heat exchange unit has higher heat exchange effect and heat exchange capacity than the traditional heat exchange device, which is reflected in the following two aspects:

[0107] The present invention gives full play to the positive effect of temperature difference factors in the heat exchange process. At the inlet of the open tunnel structure, the natural water source water and the heat exchange medium are in a high temperature difference heat exchange range, which belongs to a high-intensity heat exchange condition. The circulation speed of the heat exchange medium is moderately increased, that is, the Reynolds number of the heat exchange medium in the shell and tube heat exchange unit is increased, the heat exchange intensity is increased, the residence time of the heat exchange medium is reduced, the total flow rate is increased, and more heat exchange is obtained. The outer wall surface of the shell and tube heat exchange unit can also be controlled to produce slight phase change ice, so that the high temperature factor of the natural water source water at the inlet of the open tunnel structure is converted into an effective heat exchange power.

[0108] At the exit of the open tunnel structure, the natural water source water and the heat exchange medium are in the low temperature difference heat exchange range, which belongs to the low intensity heat exchange condition. The heat exchange medium circulation speed is moderately reduced, that is, the Reynolds number of the heat exchange medium in the shell and tube heat exchanger is reduced, and the heat exchange intensity is reduced. Under the condition that the inlet and outlet temperature difference of the heat exchange medium in each unit is basically the same, the residence time of the heat exchange medium is increased, the total flow rate is reduced, and less heat exchange is obtained. The outer wall of the shell and tube heat exchange unit can be controlled not to have a high-intensity phase change to produce a thick ice layer, but only a low-intensity phase change to produce a thin ice layer. It ensures the control of wall ice formation when the natural water source water is discharged at low temperature, and the forward flow is achieved, so as to achieve the purpose of extracting the energy of the natural water source water to the maximum extent.

[0109] In order to better illustrate the application of the heat exchange device and control method for heat exchange between a natural water source and a heat exchange medium described in the present invention, the present invention sets up a specific implementation method for analysis for further explanation.

[0110] Examples

[0111] In this embodiment, the heat exchange device of the present invention uses the sewage source of a sewage treatment plant as a heat source for urban heating. The sewage treatment plant discharges 30,000 tons of treated sewage per day, with a minimum discharge temperature of 12°C in winter, a freezing point of 0°C, and a density of 1000kg / m 3 , specific heat is 4.18 kj / kg, 4.18×10 6 J / m 3 .

[0112] After the wastewater source extracts heat energy, the minimum discharge temperature can reach 2°C, which is 2°C above the freezing point. The maximum value of the environmental heating power is [30000 / (24×3600)]×(12-2)×4.18×10 6 J / m 3 =1.451×10 7 W = 14.5 MW. In the system of Example 1, a centrifugal heat pump unit can be used for heating, and the heat pump main engine has a COP of 3.6, so the maximum heating power is 14.5×(3.6 / (3.6-1))=20.1 MW, that is, the maximum heating capacity is 20.1 MW.

[0113] In the heat exchange device of this embodiment, the natural water source is sewage, the heat exchange medium in the tube-in-tube heat exchange unit is an alcohol-containing aqueous solution, and the tube-in-tube heat exchange unit can be selected as a bare tube tube-in-tube heat exchanger made of aluminum alloy, and in this embodiment, 33 bare tube tube-in-tube heat exchangers are required, with a surplus coefficient of 1.42. Every 3 bare tube tube-in-tube heat exchangers are connected in series to form a tube-in-tube heat exchange unit, and 11 tube-in-tube heat exchange units are connected in parallel to each other and placed in an open tunnel structure.

[0114] It should be noted that the density of sewage is 1kg / m 3 , the freezing point is 0℃, the lowest sewage source water temperature is 12℃, the temperature corresponding to the maximum density of the sewage source is 4℃, the specific heat of the sewage source is 4.18kJ / (kg*℃), 4.18×10 6 J / (m 3 *℃), the theoretical maximum temperature drop of sewage source heat exchange is 12℃-2℃=10℃. Accordingly, in this embodiment, the density of the heat exchange medium alcohol aqueous solution is 1kg / m 3 , its freezing point is -15℃, the specific heat of the heat transfer medium is 4.18kJ / (kg*℃), 4.18×10 6 J / (m 3 *℃).

[0115] In this embodiment, the tube diameter d of the shell-and-tube heat exchanger used in the heat exchange device is 32 mm; the wall thickness σ of the shell-and-tube heat exchanger is 3 mm; the thermal conductivity λ1 of the shell-and-tube heat exchanger is 273 W / (m*K); the outer dimensions of the shell-and-tube heat exchanger are length×width×height=4000 mm×1000 mm×1250 mm; the shell-and-tube heat exchanger uses aluminum alloy light tubes that are bent 180° and repeatedly arranged, with a single row length of 1 m, folded 19 times, and a total length of a single tube of 20 m; 70 heat exchange tubes are arranged in parallel in each shell-and-tube heat exchanger; the total length of the tubes of the shell-and-tube heat exchanger is 1400 m; the heat exchange area of ​​each shell-and-tube heat exchanger is 1400×3.14×0.032=140.7 m 2 ; The heat transfer area of ​​the fins of the single tube heat exchanger is 135m 2 , then the comprehensive heat exchange area of ​​the single-body shell-and-tube heat exchanger is 140.7+135=275.7m 2 The comprehensive heat transfer coefficient of the single shell and tube heat exchanger is 300W / (m 2 *K); Therefore, in this embodiment, the total heat exchange area of ​​the heat exchange device of the present invention is S = 14.5MW / 300W / (m 2 *K) / 7.56K=6393m 2 .

[0116] Accordingly, in this embodiment, the interval between the heat exchangers in the heat exchange device in the open tunnel structure is 2m. The total tunnel length required to place 33 4m long shell and tube heat exchangers is 33×(4+2)=198m. The width of a single heat exchanger is 1m. The two sides of the open tunnel structure are controlled to have a 100mm gap with the single shell and tube heat exchanger, so the width of the open tunnel structure is set to 1.2m. The height of the single shell and tube heat exchanger is 1.25m. The upper part of the open tunnel structure is an open structure. In order to overcome factors such as ice formation, scaling, sedimentation, moss formed on the tube wall, and resistance fluctuations of adsorbed shell mollusks, and to reserve a certain amount of space for water level increase, the height of the open tunnel structure is designed to be 2m. In order to ensure smooth water flow, the tunnel is designed to have a slope of 2%, and the total water-facing surface area of ​​a single heat exchanger is 1.25m 2 The maximum area of ​​the tube facing the water is 0.608m 2 , then the minimum area for sewage to pass through the shell and tube heat exchanger is 0.642m 2 , the equivalent circle diameter is 0.9m, the effective heat exchange length of the tunnel is 33×4=132m, and the aspect ratio of the open tunnel structure is set to 147.

[0117] When the heat exchange device of the embodiment of the present invention is used for testing, sewage enters the open tunnel structure in the heat exchange device and flows in the open tunnel structure according to the slope of the tunnel. The normal water level in the tunnel is 1.5m, and the total area of ​​the water-facing surface is 1.8m. 2 The maximum water-facing surface area of ​​the tubes in a tube heat exchanger is 0.608m2 The minimum area of ​​sewage tunnel is 1.192m 2 The maximum design flow rate of sewage is 1.25×10 3 m 3 / h, the maximum flow rate through the cross-sectional area of ​​the open tunnel structure is 0.3m / s, the shortest residence time for effective heat exchange of natural water source water is 440s, and after the heat exchange is completed, the sewage that has undergone heat exchange is returned to the sewage source.

[0118] It should be noted that in the heat exchange device of the present invention, the cross-sectional area of ​​a single heat exchange tube is 0.013 2 ×3.14=0.00053m 2 The total number of heat exchange tubes in parallel is 11×70=770, and the total cross-sectional area of ​​the heat exchange tubes is 0.4081m 2 , the flow distance of the heat exchange medium in a single shell and tube heat exchange unit is 3×20=60m, then the flow velocity of the heat exchange medium in the shell and tube is 0.74m / s. During this process, the average residence time of the heat exchange medium in the shell and tube of a single shell and tube heat exchange unit is 81s.

[0119] When the sewage is input into the heat exchange device of the embodiment of the present invention for heat exchange, the minimum input water temperature of the sewage is 12°C; the minimum inlet temperature of the heat exchange medium is -7°C, which is 3°C lower than the freezing point of the sewage and 8°C higher than the freezing point of the heat exchange medium. In this embodiment, when the sewage is heat exchanged, the maximum flow rate of the heat exchange sewage is 0.347m 3 / s, the maximum flow rate of heat exchange medium is 1.09×10 3 m 3 / h. After the heat exchange of the heat exchange medium in the shell-and-tube heat exchange unit is completed, the average heat exchange temperature of the heat exchange medium rises by 11.5°C, the heat exchange temperature of the sewage source drops by 10°C, the average heat exchange temperature difference between the sewage source and the heat exchange medium is 7.56°C, the average outlet temperature of the heat exchange medium is 4.5°C, and the lowest outlet temperature of the sewage source is 2°C, which is 2°C higher than the freezing point.

[0120] In this embodiment, the control parameters of each tube-in-tube heat exchange unit in the heat exchange device are shown in Table 1.

[0121] Table 1.

[0122]

[0123] Accordingly, in this embodiment, when the heat exchange device is in the heat exchange peak and valley, the water-ice phase change will provide heat buffer, wherein the comprehensive heat exchange area of ​​the single-body shell-and-tube heat exchanger is: 140.7+135=275.7m 2 33 single-body shell-and-tube heat exchangers were selected, with a total heat exchange area of ​​33×275.7m 2 =9098.1m 2 .

[0124] The ice thickness of each single tube heat exchanger is set to 10mm, and the total ice thickness is 90m 3 , water-ice phase heat: 30096MJ, the maximum heating capacity of the system design is: 20.1MW, and the water-ice phase heat provides 10% peak-valley buffering capacity. Finally, at the peak of heating, the heating capacity of the heat exchange device in this embodiment is increased by 10%, and the delay is 4 hours.

[0125] It should be noted that the prior art in the protection scope of the present invention is not limited to the embodiments given in the present application documents. All prior art that does not contradict the scheme of the present invention, including but not limited to prior patent documents, prior public publications, prior public uses, etc., can be included in the protection scope of the present invention.

[0126] In addition, the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0127] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with the contents disclosed by those skilled in the art from the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A heat exchange device for heat exchange between a natural water source and a heat exchange medium, characterized in that: It includes: An open tunnel structure having a slope formed along a length direction, wherein the slope drives natural water source water to flow in the open tunnel structure; A plurality of tube-in-tube heat exchange units connected in parallel to each other are arranged in the open tunnel structure along the length direction of the open tunnel structure, and heat exchange medium flows in the tubes of the tube-in-tube heat exchange units; the tube-in-tube heat exchange units include a plurality of tube rows arranged in parallel and / or in series, and each tube row includes a plurality of tubes arranged in parallel to each other or a plurality of tube sections formed by bending a single tube and being parallel to each other; The heat exchange medium storage tank at the inlet end is connected to each tube-in-tube heat exchange unit through an independent input pipeline to input heat exchange medium with the same temperature into each tube-in-tube heat exchange unit; each input pipeline is provided with a pump; The heat exchange medium storage tank at the outlet end is connected to each tube-in-tube heat exchange unit through an independent output pipeline, and the heat exchange medium is output from each tube-in-tube heat exchange unit to the heat exchange medium storage tank at the outlet end; A heat pump system, which is connected to the inlet end heat exchange medium storage tank and the outlet end heat exchange medium storage tank respectively; A control device, which is connected to each pump to control the heat exchange medium in each tube heat exchange unit to have different flow speeds, so as to control the phase change ice within a set thickness range to be generated on the outer wall of each tube heat exchange unit; A plurality of first temperature detectors are arranged along the length direction of the open tunnel structure to respectively detect the temperature change state of water flowing in the open tunnel structure.

2. The heat exchange device according to claim 1, characterized in that: The control device comprises a variable frequency controller.

3. The heat exchange device according to claim 1, characterized in that: The slope is ≤ 2%.

4. The heat exchange device according to claim 1, characterized in that: The aspect ratio of the open tunnel structure is ≥50, and the aspect ratio is the ratio of the flow distance of natural water source water to the diameter of a circle of equal area converted to the effective cross-sectional area of ​​natural water source water.

5. The heat exchange device according to claim 1, characterized in that: It also includes a second temperature detector and a third temperature detector, which respectively detect the temperature of the heat exchange medium output from the heat exchange medium storage tank at the inlet end and the temperature of the heat exchange medium input to the heat exchange medium storage tank at the outlet end.

6. A control method for a heat exchange device according to any one of claims 1 to 5, characterized in that: Includes steps: Set the temperature drop gradient of natural water source water from the entrance to the exit of the open tunnel structure; The control device controls each pump to control the heat exchange medium in each tube heat exchange unit to have different flow speeds, thereby achieving a set temperature drop gradient and causing phase change ice within a set thickness range to form on the outer wall of each tube heat exchange unit.

7. The control method of the heat exchange device according to claim 6, characterized in that: The temperature drop gradient of the natural water source water is set to be nonlinear.

8. The control method of the heat exchange device according to claim 6, characterized in that: The flow rate of the heat exchange medium in the shell and tube heat exchange unit at the entrance of the open tunnel structure is higher than the flow rate of the heat exchange medium in the shell and tube heat exchange unit in the middle section of the open tunnel structure, and the flow rate of the heat exchange medium in the shell and tube heat exchange unit in the middle section is higher than the flow rate of the heat exchange medium in the shell and tube heat exchange unit at the exit of the open tunnel structure.

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