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CN-122015531-A - Suspension floating type self-stress relief cryogenic heat exchange device

CN122015531ACN 122015531 ACN122015531 ACN 122015531ACN-122015531-A

Abstract

The invention relates to the field of low-temperature process machinery and automatic control, in particular to a suspension floating type self-stress relief cryogenic heat exchange device, which solves the problems that a traditional rigid fixed tube plate heat exchanger is easy to generate low-cycle fatigue failure and flow field dead zone scale under the cold and hot impact of a peak regulation station. The device comprises a pressure-bearing heat-insulating shell and the heat exchange core is immersed in the water. The top of the core body is fixed through a single-point suspension mechanism, an axial thermal compensation gap is reserved between the bottom and the shell, a zero-stress static topology with 'hanging upwards and floating downwards' is formed, and structural constraint stress caused by thermal expansion difference is thoroughly eliminated. The heat exchange tube bundle adopts a spiral winding structure and is configured to induce fluid in the tube to generate dean vortex secondary flow, the self-cleaning of the tube wall is realized by using high shearing force, and the bottom of the shell is provided with an inverted cone-shaped dirt collecting groove for on-line separation of solid impurities precipitated by phase change. The device has the characteristics of long fatigue life and high-efficiency heat transfer.

Inventors

  • WANG FANYU
  • WANG YAOWU
  • DU LIXIA

Assignees

  • 陕西融科低温设备有限公司

Dates

Publication Date
20260512
Application Date
20260313

Claims (8)

  1. 1. A suspended floating self-stress relief cryogenic heat exchange device is characterized in that, Comprises a pressure-bearing heat insulation shell (10), a stress decoupling type heat exchange core body (20) and a suspension floating support mechanism (30): The pressure-bearing heat-insulating shell (10) is internally limited with a sealed containing cavity capable of bearing preset pressure, and the bottom of the pressure-bearing heat-insulating shell (10) is provided with an inverted cone-shaped dirt collecting groove (15) for physically separating solid impurities; The stress decoupling heat exchange core body (20) is coaxially immersed in the sealed containing cavity, and the stress decoupling heat exchange core body (20) comprises a central cylinder (21) and a spiral heat exchange tube bundle (22) wound on the central cylinder; The suspension floating support mechanism (30) adopts a statically determined design, and positions and supports the stress decoupling type heat exchange core (20) through a unique rigid constraint point; The stress decoupling type heat exchange core body (20) is provided with a bottom free floating end, the bottom free floating end is positioned at the bottom end of the stress decoupling type heat exchange core body (20), and an axial thermal compensation gap (32) is reserved between the bottom free floating end and the inner bottom wall of the pressure-bearing heat insulation shell (10); the axial dimension of the axial thermal compensation gap (32) is configured to be greater than the theoretical amount of cold shrinkage of the stress decoupling heat exchange core at a maximum design temperature differential.
  2. 2. The apparatus of claim 1, wherein the device comprises a plurality of sensors, The hydrodynamic structure of the stress decoupling type heat exchange core body (20) is characterized in that the spiral heat exchange tube bundle (22) is formed by coaxial and tight winding of a plurality of layers of pipelines, the geometric parameters of a spiral angle (beta) and a winding curvature radius (R) of the spiral heat exchange tube bundle are configured to meet the hydrodynamic condition that the fluid Dien number in the pipe is greater than 100, so that symmetrical double-cell secondary vortex is formed on the section of the pipe, longitudinal distance strips (23) are arranged between the pipe layers of the spiral heat exchange tube bundle (22), and an arch baffle plate for transversely blocking fluid is not arranged in a sealing containing cavity, so that a dead-zone-free flow field which flows unidirectionally along the axial direction is formed, and solid impurities precipitated in a cryogenic working medium are prevented from being detained in a shell side.
  3. 3. The apparatus of claim 1, wherein the device comprises a plurality of sensors, The suspension floating support mechanism (30) further comprises a radial limiting guide assembly (35), wherein the radial limiting guide assembly (35) comprises a plurality of low friction coefficient sliding blocks (36) circumferentially and uniformly distributed at the bottom of the stress decoupling type heat exchange core body (20), and guide surfaces (37) correspondingly arranged on the inner wall of the pressure-bearing heat insulation shell (10), a preset radial micro-gap (0.5 mm-2.0 mm) is reserved between the low friction coefficient sliding blocks (36) and the guide surfaces (37), and the radial limiting guide assembly is configured to limit radial swing amplitude of the stress decoupling type heat exchange core body (20) while allowing the stress decoupling type heat exchange core body (20) to axially and freely stretch so as to prevent fluid induced vibration.
  4. 4. The apparatus of claim 1, wherein the device comprises a plurality of sensors, The inverted cone-shaped sewage collecting tank (15) is structurally characterized in that the inverted cone-shaped sewage collecting tank is located at the bottommost end of the pressure-bearing heat-insulating shell (10), the cone angle of the inverted cone-shaped sewage collecting tank is configured to be larger than the repose angle of solid impurities in cryogenic liquid, for example, typical values of millimeter-sized dry ice spherical particles in liquid CO 2 are 32-45 degrees, irregular particles can reach 45-50 degrees, a sewage draining outlet and a low-temperature sewage draining valve (16) are arranged at the bottommost point of the inverted cone-shaped sewage collecting tank (15), and the inverted cone-shaped sewage collecting tank is configured to collect and periodically drain high-concentration impurity slurry which is settled down from a dead-zone-free flow field above based on Stokes settlement principle.
  5. 5. The apparatus of claim 1, wherein the device comprises a plurality of sensors, The pressure-bearing heat-insulating shell (10) actually forms a phase-change thermodynamic clamping cavity, wherein the phase-change thermodynamic clamping cavity is connected to an external pressure regulating system (40) through a gas phase outlet, and the external pressure regulating system (40) is configured to apply physical hard constraint on the temperature of the outer wall surface of the tube of the spiral heat exchange tube bundle (22) by regulating the gas phase pressure in the phase-change thermodynamic clamping cavity under the full-immersion working condition and utilizing the corresponding relationship between saturation pressure and temperature determined by the Clausius-kelapel equation so as to prevent the temperature from being lower than the freezing point of fluid in the tube.
  6. 6. The apparatus of claim 1, wherein the device comprises a plurality of sensors, The spiral heat exchange tube bundle (22) is manufactured by the steps that pretension is applied to the spiral heat exchange tube bundle (22) in the manufacturing process, two ends of the spiral heat exchange tube bundle (22) are converged to a header at the top through a flexible transition section, a second heat exchange tube bundle or an electric heating element for introducing external heating gas is not contained in the pressure-bearing heat insulation shell (10), and the antifreezing function of the spiral heat exchange tube bundle is only dependent on thermal coupling and pressure control of fluid.
  7. 7. The apparatus of claim 1, wherein the device comprises a plurality of sensors, The dimension H gap of the axial thermal compensation gap (32) satisfies the following mathematical relationship: Wherein k is a safety coefficient greater than 1.2, L is the characteristic length of the stress decoupling heat exchange core body (20), alpha (T) is the linear expansion coefficient of the material, T hot is the ambient temperature, and T cold is the cryogenic working medium temperature.
  8. 8. The apparatus of claim 1, wherein the device comprises a plurality of sensors, The stress decoupling type heat exchange core (20) and the pressure-bearing heat insulation shell (10) adopt a core-pulling type connection structure, and the whole stress decoupling type heat exchange core (20) and the suspension floating support mechanism (30) can be integrally moved out of the pressure-bearing heat insulation shell (10) through disassembling the suspension flange assembly (31) of the pressure-bearing heat insulation shell (10), so that the overhaul and the scale removal are convenient.

Description

Suspension floating type self-stress relief cryogenic heat exchange device Technical Field The invention belongs to the technical fields of cryogenic process equipment, extreme environment heat management and energy infrastructure safety. In particular to an integrated immersed heat exchange device which is applied to cryogenic fluid peak shaving stations, receiving terminals and space ground filling systems of liquefied natural gas, liquid hydrogen, liquid helium and the like and has full life cycle self-adaptive thermal stress elimination, microcosmic flow field self-cleaning and intrinsic safety antifreezing functions. The invention is particularly suitable for industrial scenes with intermittent task section and high-frequency large-amplitude thermal shock characteristics, and aims to solve the problems of structural fatigue failure and heat transfer performance attenuation of the traditional rigid heat exchange equipment under unsteady working conditions. Background In modern clean energy and aerospace engineering, cryogenic heat exchangers are known as the "heart" of energy conversion systems. The core function of the device is to establish a high-efficiency heat flow channel between two extreme temperature areas, namely a hot end is usually connected with a process pipe network with the ambient temperature (about 300K), and a cold end is immersed in cryogenic working media of liquid nitrogen (77.3K), liquefied natural gas (111K) and even liquid hydrogen (20.3K). This means that the apparatus body, in particular the pressure shell, tube sheet, heat exchanger tube bundle and the connection elements, have to withstand large radial and axial temperature differences of more than 220K and even 280K within extremely short geometrical distances. Unlike large petrochemical equipment (such as ethylene cracking furnace and base load type LNG liquefying plant) which pursues long-period continuous stable operation, the operation modes of the urban gas peak shaving station and the emergency gas source station have obvious pulse characteristics: (1) At the moment of starting, the temperature of the inner wall surface of the equipment needs to drop rapidly from the ambient temperature to a cryogenic temperature zone within a few minutes, and the temperature rate can reach more than 50K/min. (2) And (3) heat re-warming, namely evacuating residual liquid after the task is finished, and returning the equipment to normal temperature, or carrying out forced heating and purging when the equipment encounters frozen blockage. This frequent "quench-sub-zero run-re-warm" cycle places the heat exchanger in an unsteady thermal transient for long periods of time. According to the heat conduction equation: α▽2T Wherein T is temperature, unit K, T is time, unit s, alpha is thermal diffusion coefficient, the unit is m2/s, which represents the diffusion speed of heat in the material, 2 T is Laplacian, which represents the second-order change and curvature of temperature in space, and unit is K/m2. When the heat exchanger is in an unsteady state heat transient for a long time, a great transient temperature gradient V T is formed inside the material. Existing industrial grade heat exchanger design criteria (e.g., TEMA standard, GB/T151) are mostly based on steady state operating condition assumptions, and conventional structures expose serious endogenous defects in mechanical adaptability and hydrodynamic stability in the face of such low cycle fatigue operating conditions. 1. Mechanical failure mechanism analysis of rigid constraint structure: (1) Engineering traps of multiple hyperstatic structures in the prior art generally adopt fixed tube-plate type, rigid support spiral tube type or multi-flow plate-fin structures in order to pursue compactness of the structure and convenience in manufacturing. For example, chinese patent application CN117847407a (publication 2024, 04, 09) discloses a methane subcooling and filling system, in which a core subcooler adopts a structure in which a first heat exchanger (for passing liquid methane) and a second heat exchanger (for passing heated gas) are nested in the same housing. This design attempts to reduce volume by integration, but looks at solid mechanics, which builds a typical "multiple hyperstatic system". In mechanical topology, the shell, the first tube bundle, the second tube bundle and the tube sheet together form a rigid frame. When the system is in a working state, the shell is contacted with liquid nitrogen (about 77K) to shrink, the first tube bundle is filled with liquid methane (about 100K) to shrink, but the amplitude is smaller than that of the shell, and the second tube bundle is filled with normal temperature or heated nitrogen (about 300K), so that thermal expansion is even possible. (2) Failure deduction based on thermoelastic mechanics, since the above components are rigidly connected by welding or expansion, their free deformation is forcibly constrained by geometric boun