Variable pressure micro-channel condensation dehumidification device and regulation method thereof

Abstract

The application provides a variable-pressure micro-channel condensation dehumidification device and a regulation method thereof. The variable-pressure micro-channel condensation dehumidification device comprises a compressor, a micro-channel dehumidifier, a first gas-liquid separator and an expander. An air inlet pipe is connected with an air inlet of the compressor. An air outlet of the compressor is connected with an air inlet of the micro-channel dehumidifier. An air outlet of the micro-channel dehumidifier is connected with an inlet of the first gas-liquid separator. An air outlet of the first gas-liquid separator is connected with an air inlet of the expander. An air outlet of the expander is connected with an air outlet pipe. The variable-pressure micro-channel condensation dehumidification device and the regulation method thereof do not need additional refrigeration equipment, and energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of air dehumidification, in particular to a variable pressure micro-channel condensation dehumidification device and a control method thereof. BACKGROUND

[0002] The control of air humidity plays an important role in civil buildings and industrial processes, and is one of the important factors to achieve indoor comfortable conditions. Traditional dehumidification systems, such as air conditioners, dehumidifiers, etc., usually use compressors and evaporators to condense and dehumidify air during the dehumidification process. However, these traditional devices have problems such as inaccurate temperature and humidity regulation, low energy efficiency, etc. Especially in high humidity and large flow environments, the dehumidification effect and system energy efficiency will be significantly reduced.

[0003] Therefore, it is urgent to improve the energy efficiency of the dehumidification system and make the dehumidification system have more flexible regulation. Condensation dehumidification is one of the traditional dehumidification methods, but currently it mainly uses normal pressure condensation dehumidification, which needs to obtain a low-temperature cooling source from a water chiller, and also needs to be reheated to make the air reach the comfortable temperature required by the human body. Therefore, the condensation dehumidification process of wet air at normal pressure will cause energy waste, leading to an increase in the energy consumption of the dehumidification system. When the environment needs deep dehumidification, the dew point temperature is extremely low, even below 0℃, which may cause the equipment to frost and have low energy efficiency. SUMMARY

[0004] The present application provides a variable pressure micro-channel condensation dehumidification device and a control method thereof, which does not need additional refrigeration equipment and reduces energy consumption.

[0005] To solve the above technical problems, the embodiments of the present application adopt the following technical solutions:

[0006] In a first aspect, the embodiments of the present application provide a variable pressure micro-channel condensation dehumidification device, which comprises a compressor, a micro-channel dehumidifier, a first gas-liquid separator and an expander. The gas inlet pipe is connected to the gas inlet of the compressor, the gas outlet of the compressor is connected to the gas inlet of the micro-channel dehumidifier, the gas outlet of the micro-channel dehumidifier is connected to the inlet of the first gas-liquid separator, the gas outlet of the first gas-liquid separator is connected to the gas inlet of the expander, and the gas outlet of the expander is connected to the gas outlet pipe.

[0007] As a further improvement of the embodiment of the present application, the air-air heat exchanger and the second gas-liquid separator are further included, the gas outlet of the first gas-liquid separator is connected with the gas inlet of the expander, specifically, the gas outlet of the first gas-liquid separator is connected with the first gas inlet of the air-air heat exchanger, the first gas outlet of the air-air heat exchanger is connected with the gas inlet of the second gas-liquid separator, and the gas outlet of the second gas-liquid separator is connected with the gas inlet of the expander; the gas outlet of the expander is connected with the gas outlet pipe, specifically, the gas outlet of the expander is connected with the second gas inlet of the air-air heat exchanger, and the second gas outlet of the air-air heat exchanger is connected with the gas outlet pipe.

[0008] As a further improvement of the embodiment of the present application, the micro-channel dehumidifier includes a first channel layer and a second channel layer which are stacked, and the first channel layer and the second channel layer are each provided with a plurality of micro-channels; the inlet of the first channel layer is connected with the gas outlet of the compressor as the gas inlet of the micro-channel dehumidifier, and the outlet of the first channel layer is connected with the gas inlet of the first gas-liquid separator as the gas outlet of the micro-channel dehumidifier; the diameter of the micro-channels of the first channel layer gradually increases along the air flow direction.

[0009] As a further improvement of the embodiment of the present application, the cooling working medium of the micro-channel dehumidifier is a natural cooling source or provided by an evaporative cooling tower.

[0010] As a further improvement of the embodiment of the present application, the motor is further included, the input end of the motor is connected with the expander, and the output end of the motor is connected with the compressor.

[0011] In the second aspect, the embodiment of the present application further provides a control method of the variable-pressure micro-channel condensation dehumidification device provided in the first aspect, including the following steps:

[0012] Step 10, establishing a wet air positive pressure condensation dehumidification heat and mass transfer model;

[0013] Step 20, according to the structure parameters of the micro-channel dehumidifier and the wet air property parameters including the wet air pressure entering the micro-channel dehumidifier, the wet air positive pressure condensation dehumidification heat and mass transfer model is used to calculate the air humidity output by the micro-channel dehumidifier under different wet air pressures, so as to obtain the corresponding relationship between the wet air pressure entering the micro-channel dehumidifier and the air humidity output by the micro-channel dehumidifier;

[0014] Step 30, according to the corresponding relationship between the wet air pressure entering the micro-channel dehumidifier and the air humidity output by the micro-channel dehumidifier, the preset wet air pressure range corresponding to the target air humidity is obtained, and the compressor is controlled so that the wet air pressure entering the micro-channel dehumidifier is within the preset wet air pressure range.

[0015] As a further improvement of the embodiment of the present application, the wet air positive pressure condensation dehumidification heat and mass transfer model includes a single droplet model, a droplet growth model and a channel condensation model.

[0016] The expression of the single droplet model is Formula (1) to Formula (4):

[0017]

[0018]

[0019] Q ds = 4πr d λ w (t ds -t z ) Formula (3)

[0020]

[0021] In the formula, M i represents the mass flux through the Knudsen layer, r i represents the Knudsen layer radius, ρ i represents the Knudsen layer vapor density, R represents the gas constant, t i represents the Knudsen layer surface temperature, ρ d represents the droplet density, r d represents the droplet radius, t ds represents the droplet surface temperature; M c represents the mass flux from the continuous region to the Knudsen layer, D v represents the water vapor diffusion coefficient, ρ m represents the moist air density, ρ v represents the moist air vapor partial density; Q ds represents the heat flux of a single droplet growing to r d , λ w represents the thermal conductivity of water, t z represents the cold wall temperature; M ds represents the mass flux of a single droplet growing to r d , and L represents the latent heat of condensation per unit time;

[0022] The expression of the droplet growth model is Formula (5) to Formula (12):

[0023]

[0024] S β = S” β +S”' β Formula (6)

[0025]

[0026]

[0027]

[0028] Y β =Y" β +Y"' β Equation (10)

[0029]

[0030]

[0031] where q β represents the total heat transfer rate during droplet growth, A represents the sum of the cylindrical surface areas of all microchannels in the first channel layer of the microchannel dehumidifier, q ds represents the heat transfer rate at the droplet radius corresponding to a certain time, τ" β represents the time of droplet coalescence, τ"' β represents the time of droplet sliding, and m represents the total number of droplets; m β represents the total mass transfer rate during droplet growth, m ds represents the mass transfer rate at the droplet radius corresponding to a certain time;

[0032] The expressions of the channel condensation model are Equations (13) to (17):

[0033]

[0034]

[0035]

[0036] q x = K (t m -t w ) Equation (16)

[0037] q i = q x,i + q β,i , i = 1, 2, …, n Equation (17)

[0038] m i = m β,i Equation (18)

[0039] dQ i = q i dA i Equation (19)

[0040] dM i = m i dA i Equation (20)

[0041]

[0042] t m,i = f(p, h m,i ) Equation (23)

[0043] where k w represents the second passage layer convective heat transfer coefficient, Nu w represents the Nusselt number of the cooling water, r a represents the diameter of the microchannel of the second passage layer; k m represents the first passage layer convective heat transfer coefficient, Nu m represents the Nusselt number of the air, λ m represents the thermal conductivity of the air, r c represents the average diameter of the microchannel of the first passage layer, r c = (r a + r b ) / 2, r b represents the inlet diameter of the microchannel of the first passage layer; K represents the convective heat transfer coefficient of the wet air and the baffle, r g represents the baffle thickness, λ cu represents the thermal conductivity of copper; q x represents the convective heat transfer rate between the wet air and the baffle, t m represents the temperature of the wet air, t w represents the temperature of the cooling water; q i represents the heat transfer rate of the i-th microchannel segment, q x,i represents the convective heat transfer rate between the wet air and the baffle in the i-th microchannel segment, q β,i represents the total heat transfer rate of the droplet growth process in the i-th microchannel segment, m i represents the mass transfer rate of the i-th microchannel segment, m β,i represents the total mass transfer rate of the droplet growth process in the i-th microchannel segment; dQ i represents the heat transfer flux of the i-th microchannel segment, dA i represents the cylindrical surface area of the i-th microchannel segment of the first passage layer of the microchannel dehumidifier, dM i represents the mass flux of the i-th microchannel segment; h m,i represents the enthalpy of the wet air at the outlet of the i-th microchannel segment, h m,i-1 represents the enthalpy of the wet air at the outlet of the i-1-th microchannel segment, q m represents the mass flow rate of the wet air, q a represents the mass flow rate of the dry air, d m,i represents the moisture content of the wet air at the outlet of the i-th microchannel segment, d m,i-1 represents the moisture content of the wet air at the outlet of the i-1-th microchannel segment, t m,i represents the temperature of the wet air at the outlet of the i-th microchannel segment.

[0044] As a further improvement of the embodiment of the application, the step 20 specifically comprises:

[0045] Step 201, initialize the droplet state parameters;

[0046] Step 202, using an iterative method, the target is the same calculation results of formula (1), formula (2) and formula (4), the droplet state parameters are calculated; the droplet state parameters are compared with the initialized droplet state parameters, if the error condition is not met, the droplet state parameters are reinitialized by using the dichotomy method, and step 202 is executed; if the error condition is met, step 203 is executed;

[0047] Step 203, the heat flux and mass flux generated by a single droplet are calculated by using formula (3) and formula (4); according to the heat flux and mass flux generated by a single droplet, the total heat flux and mass flux of the droplet growth process are calculated by using the droplet growth model;

[0048] Step 204, according to the total heat flux and mass flux of the droplet growth process, and the wet air property parameters, the air humidity at the outlet of the micro-channel dehumidifier under different wet air pressures is calculated by using the micro-element method; the wet air property parameters include the wet air pressure, the wet air temperature and the wet air humidity entering the micro-channel dehumidifier;

[0049] Step 205, the corresponding relationship between the wet air pressure and the air humidity is obtained.

[0050] As a further improvement of the embodiment of the application, the step 203 specifically comprises:

[0051] The micro-channel of the micro-channel dehumidifier is differentiated, the total heat flux and mass flux of the droplet growth process obtained in step 203 are taken as the heat flux and mass flux of the initial state air passing through the first micro-channel segment, the wet air pressure, the wet air temperature and the wet air humidity entering the micro-channel dehumidifier are given, the enthalpy, the moisture content and the temperature of the air at the outlet of the first micro-channel segment are calculated by using formula (21) to formula (23); the heat flux and mass flux of the second micro-channel segment are calculated by using formula (13) to formula (20), the enthalpy, the moisture content and the temperature of the air at the outlet of the second micro-channel segment are calculated by using formula (21) to formula (23), the heat flux and mass flux of each micro-channel segment and the enthalpy, the moisture content and the temperature of the outlet air are sequentially calculated; the wet air humidity and the wet air temperature are unchanged, the wet air pressure entering the micro-channel dehumidifier is re-given, the heat flux and mass flux of each micro-channel segment and the enthalpy, the moisture content and the temperature of the outlet air are sequentially calculated; thereby the air humidity at the outlet of the micro-channel dehumidifier under different wet air pressures is obtained.

[0052] As a further improvement of the embodiment of the present application, the corresponding relationship between the wet air pressure and the air humidity at the outlet of the micro-channel dehumidifier is that when the wet air pressure is 160-300 kPa, the air humidity at the outlet of the micro-channel dehumidifier is 15.6-10.9 g / kg.

[0053] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0054] The variable-pressure micro-channel condensation dehumidification device and the regulation and control method thereof provided by the present application can improve the dew point temperature by pressurizing the air, so that the water vapor in the air is more easily condensed into water and separated; the air humidity is reduced by physical means, without the need for additional refrigeration equipment, thereby reducing energy consumption; the micro-channel dehumidifier is used to dehumidify the air under positive pressure, which can effectively overcome the resistance generated by the flow of wet air, reduce the pressure loss, and improve the air condensation dehumidification performance; a wet air positive pressure condensation dehumidification heat and mass transfer model is established to monitor the state parameters of the inlet and outlet of the micro-channel dehumidifier in the condensation dehumidification process, and the corresponding relationship between the wet air pressure entering the micro-channel dehumidifier and the air humidity output by the micro-channel dehumidifier is obtained; the pressure is adjusted according to the humidity requirement, the condensation dehumidification performance is regulated and controlled by adjusting the pressure, the heat and mass transfer process is optimized, and the air dehumidification energy efficiency is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0055] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0056] Figure 1 is a structural schematic diagram of the variable-pressure micro-channel condensation dehumidification device of the embodiment of the present application;

[0057] Figure 2 is Figure 1 the structure of the micro-channel dehumidifier in the embodiment of the present application;

[0058] Figure 3 is Figure 2 a sectional view of the first channel layer in the embodiment of the present application.

[0059] In the drawings, there are: a compressor 1, a micro-channel dehumidifier 2, a first channel layer 21, a second channel layer 22, a first gas-liquid separator 3, an air-air heat exchanger 4, a second gas-liquid separator 5, an expander 6, an electric motor 7, an air inlet pipe 8, and an air outlet pipe 9. DETAILED DESCRIPTION

[0060] The technical scheme of the present application will be described in detail below with reference to the drawings.

[0061] This invention provides a variable pressure microchannel condensation dehumidification device, such as... Figure 1 As shown, it includes a compressor 1, a microchannel dehumidifier 2, a first gas-liquid separator 3, and an expander 6. The inlet pipe 8 is connected to the inlet of the compressor 1, the outlet of the compressor 1 is connected to the inlet of the microchannel dehumidifier 2, the outlet of the microchannel dehumidifier 2 is connected to the inlet of the first gas-liquid separator 3, the outlet of the first gas-liquid separator 3 is connected to the inlet of the expander 6, and the outlet of the expander 6 is connected to the outlet pipe 9.

[0062] When the above-mentioned variable pressure microchannel condensation dehumidification device is working, the humid air in the environment enters the compressor 1 through the air inlet pipe 8 for compression and pressure increase. The pressurized humid air enters the microchannel dehumidifier 2 for condensation and heat exchange to reduce the air temperature. When the air temperature drops below the dew point temperature, the water vapor in the air condenses into water and then enters the first gas-liquid separator 3 for gas-liquid separation to achieve condensation dehumidification. The dehumidified air enters the expander 6 for pressure reduction and then is output to the environment through the air outlet pipe 9.

[0063] The variable pressure microchannel condensation dehumidification device of this embodiment increases the dew point temperature by pressurizing the air, making it easier for water vapor in the air to be condensed into water and separated. It reduces air humidity through physical means, eliminating the need for additional refrigeration equipment and reducing energy consumption. By using a microchannel dehumidifier to dehumidify air under positive pressure conditions, it can effectively overcome the resistance generated by the flow of humid air, reduce pressure loss, and improve the air condensation dehumidification performance.

[0064] As a preferred example, such as Figure 1 As shown, the variable pressure microchannel condensation dehumidification device in this embodiment further includes an air-to-air heat exchanger 4 and a second gas-liquid separator 5. Specifically, the connection between the outlet of the first gas-liquid separator 3 and the inlet of the expander 6 is as follows: the outlet of the first gas-liquid separator 3 is connected to the first inlet of the air-to-air heat exchanger 4; the first outlet of the air-to-air heat exchanger 4 is connected to the inlet of the second gas-liquid separator 5; and the outlet of the second gas-liquid separator 5 is connected to the inlet of the expander 6. The connection between the outlet of the expander 6 and the outlet pipe is as follows: the outlet of the expander 6 is connected to the second inlet of the air-to-air heat exchanger 4; and the second outlet of the air-to-air heat exchanger 4 is connected to the outlet pipe.

[0065] In operation, the humid air in the environment enters the compressor 1 through the inlet pipe 8 to be compressed and pressurized, and then enters the micro-channel dehumidifier 2 to be condensed and heat-exchanged, so as to reduce the temperature of the air. When the temperature of the air is reduced to below the dew point, the water vapor in the air is condensed into water, and then enters the first gas-liquid separator 3 to be separated into gas and liquid. The air after the removal of part of the water vapor enters the air-air heat exchanger 4 to be condensed and heat-exchanged, so as to further reduce the temperature of the air. The water vapor in the air is condensed into water, and then enters the second gas-liquid separator 5 to be separated into gas and liquid, so as to realize condensation and dehumidification. The dehumidified air enters the expander 6 to be depressurized, and then enters the air-air heat exchanger 4 as a cold source. Finally, the air is output to the environment through the outlet pipe 9.

[0066] The air-air heat exchanger can be used to further condense and dehumidify the air, so as to further improve the dehumidification effect and meet the requirement of the moisture content.

[0067] As shown in Figure 2 , the micro-channel dehumidifier 2 includes a first channel layer 21 and a second channel layer 22 which are stacked. The first channel layer 21 and the second channel layer 22 are both provided with a plurality of micro-channels. The inlet of the first channel layer 21 is connected with the outlet of the compressor 1 as the air inlet of the micro-channel dehumidifier 2, and the outlet of the first channel layer 21 is connected with the inlet of the first gas-liquid separator 3 as the air outlet of the micro-channel dehumidifier 2. The first channel layer is used to pass the pressurized humid air, and the second channel layer is used to pass the cooling medium. The humid air and the cooling medium are countercurrently heat-exchanged through the partition plate between the first channel layer and the second channel layer. Preferably, the cross section of all the micro-channels is circular. The circular micro-channels can make the air flow more uniformly and stably in the micro-channels, so as to reduce the energy loss. The wall of the circular micro-channels is arc-shaped, so that the contact area of the convection heat exchange is relatively uniform, which can effectively promote the heat exchange, and further improve the overall condensation and dehumidification efficiency. As shown in Figure 3 , the diameter of the micro-channels of the first channel layer 21 gradually increases along the air flow direction, and the diameter of the micro-channels of the second channel layer 22 remains unchanged along the cooling medium flow direction. Preferably, the outlet diameter of the micro-channels of the first channel layer 21 is equal to the outlet diameter of the micro-channels of the second channel layer 22. That is, the inlet diameter of the micro-channels of the first channel layer 21 is r b , the outlet diameter of the micro-channels of the first channel layer 21 is r a , and the diameter of the micro-channels of the second channel layer 22 is r a . The diameter of the micro-channels of the second channel layer is the same as the maximum diameter of the micro-channels of the first channel layer, so that the heat exchange area of the cooling medium entering the micro-channels is increased, the flow of the cooling medium is increased, and the condensation and dehumidification effect is enhanced. Preferably, the micro-channel dehumidifier is made of copper.

[0068] In the above embodiment, the diameter of the microchannels of the first channel layer 21 gradually increases along the air flow direction, that is, a gradually expanding channel is adopted, so that the sharp change of the air flow rate is slowed down, the air flow is more uniform and stable, the flow resistance is reduced, and the pressure loss is reduced. At the same time, the contact time of the air and the partition plate is increased, and the condensation dehumidification performance of the microchannel dehumidifier is improved.

[0069] Preferably, the cooling working medium of the microchannel dehumidifier 2 adopts a natural cold source or is provided by an evaporative cooling tower. Without the need for a traditional mechanical refrigeration system, energy consumption is reduced while ensuring high cooling efficiency. The cooling working medium is preferably cooling water.

[0070] As a preferred example, the variable-pressure microchannel condensation dehumidification device of the embodiment further comprises a motor 7, the input end of the motor 7 is connected with the expander 6, and the output end of the motor 7 is connected with the compressor 1. In the embodiment, the expander performs pressure reduction on the dehumidified air, and at the same time, provides part of the energy for the operation of the compressor through the motor.

[0071] The embodiment of the present application also provides a control method of the variable-pressure microchannel condensation dehumidification device, comprising the following steps:

[0072] Step 10, establishing a wet air positive pressure condensation dehumidification heat and mass transfer model.

[0073] Step 20, according to the structure parameters of the microchannel dehumidifier and the wet air property parameters including the wet air pressure entering the microchannel dehumidifier, using the wet air positive pressure condensation dehumidification heat and mass transfer model, the air humidity output by the microchannel dehumidifier under different wet air pressures is calculated, and the corresponding relationship between the wet air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier is obtained.

[0074] Step 30, according to the corresponding relationship between the wet air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier, obtaining a preset wet air pressure range corresponding to the target air humidity, and controlling the compressor so that the wet air pressure entering the microchannel dehumidifier is within the preset wet air pressure range.

[0075] The control method of the variable-pressure microchannel condensation dehumidification device of the embodiment establishes a wet air positive pressure condensation dehumidification heat and mass transfer model, calculates the air humidity output by the microchannel dehumidifier in the condensation dehumidification process according to the structure parameters of the microchannel dehumidifier and the wet air property parameters entering the microchannel dehumidifier, obtains the corresponding relationship between the wet air pressure entering the microchannel dehumidifier and the air humidity output by the microchannel dehumidifier, adjusts the pressure according to the humidity demand, realizes the control of the condensation dehumidification performance through the adjustment of the pressure, optimizes the heat and mass transfer process, and further improves the air dehumidification energy efficiency.

[0076] As a preferred example, the wet air positive pressure condensation dehumidification heat and mass transfer model includes a single droplet model, a droplet growth model and a channel condensation model.

[0077] In the single droplet model, there are three regions, which are the inside of the droplet and the Knudsen layer and the continuous region of the vapor space around the outside of the droplet.

[0078] For the Knudsen layer, the free molecule dynamics theory is applied to calculate the mass flux through the Knudsen layer, i.e. equation (1):

[0079]

[0080] In the equation, M i represents the mass flux through the Knudsen layer, r i represents the Knudsen layer radius, p i represents the Knudsen layer vapor density, R represents the gas constant, t i represents the Knudsen layer surface temperature, p d represents the droplet density, r d represents the droplet radius, t ds represents the droplet surface temperature.

[0081] For the continuous region, the continuous medium fluid mechanics is applied to calculate the mass flux from the continuous region to the Knudsen layer, i.e. equation (2):

[0082]

[0083] In the equation, M c represents the mass flux from the continuous region to the Knudsen layer, D v represents the water vapor gas diffusion coefficient, p m represents the wet air density, p v represents the wet air vapor partial density.

[0084] For the inside of the droplet, the heat conduction law is applied to calculate the heat transfer flux of the wet air dropwise condensation when the droplet grows to a certain transient radius, i.e. equation (3):

[0085] Q ds = 4πr d λ w (t ds -t z ) equation (3)

[0086] In the equation, Q ds represents the heat transfer flux of the single droplet growing to r d , λ w represents the heat conduction coefficient of water, t z represents the cold wall surface temperature.

[0087] The mass flux of a droplet growing to a certain transient radius is calculated by using equation (4) when the dropwise condensation of wet air occurs:

[0088]

[0089] In the equation, M ds represents the mass flux of a single droplet growing to r d , L represents the latent heat of condensation per unit time.

[0090] According to the law of conservation of mass, the mass fluxes of the three regions are equal.

[0091] In the droplet growth model, the growth process of a droplet includes the process before the droplet nucleates to coalesces, the process of droplet coalescence, and the process of droplet sliding. Since the condensation of wet air has not reached a dynamic stable state before the droplet nucleates to coalesces, the heat transfer flux of this process is not included in the total heat transfer flux, and the mass flux is not included in the total mass flux.

[0092] Therefore, the total heat transfer rate of the droplet growth process is calculated by using equation (5):

[0093]

[0094] S β = S” β + S''' β Equation (6)

[0095]

[0096]

[0097] In the equation, q β represents the total heat transfer rate of the droplet growth process, A represents the sum of the cylindrical surface areas of all microchannels in the first channel layer of the microchannel dehumidifier; q ds represents the heat transfer rate at a certain time corresponding to the droplet radius, which is calculated by using equation (3) to calculate the heat transfer at a certain time corresponding to the droplet radius r d , and then dividing the droplet condensation area 4πr d 2 to obtain the heat transfer rate at a certain time corresponding to the droplet radius; τ” β represents the time of the droplet coalescence process, τ''' β represents the time of the droplet sliding process, and m represents the total number of droplets.

[0098] The total mass transfer rate of the droplet growth process is calculated by using equation (8):

[0099]

[0100] Y β = Y” β+ Y" β Equation (10)

[0101]

[0102] In the formula, m β represents the total mass transfer rate in the droplet growth process; m ds represents the mass transfer rate at the droplet radius corresponding to a certain time, which is calculated by dividing the mass flux at the droplet radius corresponding to a certain time by the droplet condensation area 4πr d 2 to obtain the mass transfer rate at the droplet radius corresponding to a certain time.

[0103] A channel condensation model is established for the micro-channel dehumidifier as shown in Figure 2 The micro-element method is adopted to divide each micro-channel into n micro-channel segments, and the heat flux and mass flux of each micro-channel segment are calculated. Preferably, the value of n ranges from 100 to 20000. Further preferably, n is 1000.

[0104] The convective sensible heat, i.e. the convective heat exchange between the humid air and the partition plate, needs to be considered.

[0105] Specifically, the cooling water side convective heat exchange coefficient is calculated by using Equation (13):

[0106]

[0107] In the formula, k w represents the second channel layer convective heat exchange coefficient, Nu w represents the Nusselt number of the cooling water, λ w represents the thermal conductivity of water, r a represents the diameter of the micro-channel of the second channel layer.

[0108] The air side convective heat exchange coefficient is calculated by using Equation (14):

[0109]

[0110] In the formula, k m represents the first channel layer convective heat exchange coefficient, Nu m represents the Nusselt number of the air, λ m represents the thermal conductivity of air, r c represents the average diameter of the micro-channel of the first channel layer, r c = (r a + r b ) / 2, r b represents the inlet diameter of the micro-channel of the first channel layer.

[0111] The convective coefficient between the humid air and the partition plate is calculated by using Equation (15):

[0112]

[0113] where K represents the convective heat transfer coefficient between the humid air and the baffle, r g represents the thickness of the baffle, λ cu represents the thermal conductivity of copper.

[0114] The convective heat transfer rate between the humid air and the baffle is calculated using Equation (16):

[0115] q x = K (t m - t w ) Equation (16)

[0116] where q x represents the convective heat transfer rate between the humid air and the baffle, t m represents the temperature of the humid air, and t w represents the temperature of the cooling water.

[0117] The heat transfer rate of the i-th microchannel segment is calculated using Equation (17):

[0118] q i = q x,i + q β,i , i = 1, 2,..., n Equation (17)

[0119] where q i represents the heat transfer rate of the i-th microchannel segment, q x,i represents the convective heat transfer rate between the humid air and the baffle in the i-th microchannel segment, and q β,i represents the total heat transfer rate during the droplet growth process in the i-th microchannel segment.

[0120] The mass transfer rate of the i-th microchannel segment is calculated using Equation (18):

[0121] m i = m β,i Equation (18)

[0122] where m i represents the mass transfer rate of the i-th microchannel segment, and m β,i represents the total mass transfer rate during the droplet growth process in the i-th microchannel segment.

[0123] The heat flux of the i-th microchannel segment is calculated using Equation (19):

[0124] dQ i = q i dA i Equation (19)

[0125] where dQ idA i dA

[0126] dM

[0127] dM i dM i dA i dA

[0128] dM i dM

[0129]

[0130]

[0131]

[0132] t m,i t m,i

[0133] h m,i h m,i-1 q m q a d m,i d m,i-1 d m,i t

[0134] As a preferred example, step 20 specifically comprises:

[0135] Step 201, initializing droplet state parameters.

[0136] Step 202, using an iterative method, the target is that the mass fluxes of the three regions in the single droplet model are equal, i.e. the calculation results of formula (1), formula (2) and formula (4) are the same, and the droplet state parameters are calculated. The droplet state parameters include the droplet surface temperature t ds , the Knudsen layer surface temperature t i and the Knudsen layer surface pressure P i .

[0137] ​​The droplet state parameters are compared with the initialized droplet state parameters, and if the error condition is not satisfied, the droplet state parameters are reinitialized by using the dichotomy, and step 202 is executed until the error condition is satisfied. If the error condition is satisfied, step 203 is executed.

[0138] In step 203, the heat flux and mass flux generated by a single droplet are calculated by using formula (3) and formula (4). According to the heat flux and mass flux generated by a single droplet, the total heat flux and mass flux in the droplet growth process are calculated by using the droplet growth model, i.e. formula (5) to formula (12).

[0139] In step 204, the air humidity at the outlet of the microchannel dehumidifier under different air pressures is calculated by using the micro-element method according to the total heat flux and mass flux in the droplet growth process and the wet air property parameters by using the channel condensation model. The wet air property parameters include the air pressure, air humidity and air temperature of the wet air entering the microchannel dehumidifier.

[0140] In step 205, the corresponding relationship between the air pressure and the air humidity is obtained.

[0141] In step 204, the following steps are included.

[0142] The microchannel of the microchannel dehumidifier is differentiated, the total heat flux and mass flux in the droplet growth process obtained in step 203 are taken as the heat flux and mass flux of the air in the initial state passing through the first microchannel segment, the air pressure, air humidity and air temperature of the wet air entering the microchannel dehumidifier are given, and the enthalpy, humidity and temperature of the air at the outlet of the first microchannel segment are calculated by using formula (21) to formula (23). The heat flux and mass flux of the second microchannel segment are calculated by using formula (13) to formula (20), and the enthalpy, humidity and temperature of the air at the outlet of the second microchannel segment are calculated by using formula (21) to formula (23). The heat flux and mass flux of each microchannel segment and the enthalpy, humidity and temperature of the air at the outlet are calculated in sequence. The air humidity and air temperature are unchanged, the air pressure of the wet air entering the microchannel dehumidifier is given again, and the heat flux and mass flux of each microchannel segment and the enthalpy, humidity and temperature of the air at the outlet are calculated in sequence. Thus, the air humidity at the outlet of the microchannel dehumidifier under different air pressures is obtained.

[0143] Preferably, the humidity of the wet air is set to 100%, the temperature of the wet air is set to 27℃, the temperature of the cooling water is set to 26℃, and the pressure of the wet air is set to vary in the range of 160-300kPa, so as to obtain a corresponding relationship between the pressure of the wet air and the humidity of the air at the outlet of the micro-channel dehumidifier, i.e., when the pressure of the wet air is 160-300kPa, the humidity of the air at the outlet of the micro-channel dehumidifier is 15.6-10.9g / kg. The above-mentioned corresponding relationship is obtained in this embodiment, and under the condition of positive pressure, when the pressure of the air increases, the humidity of the outlet air decreases, and the dehumidification efficiency is improved. In step 30, for example, if the target humidity of the air is 11g / kg, the compressor is adjusted so that the pressure of the wet air output by the compressor is 160-300kPa, and after passing through the micro-channel dehumidifier, the humidity of the air approaches the target humidity of the air.

[0144] The wet air positive pressure condensation dehumidification heat and mass transfer model established in the embodiment of the present application includes a single droplet model, a droplet growth model and a channel condensation model. The model is established from the perspective of the beaded condensation of the wet air, and the influence of the non-condensable gas in the air on the droplet condensation is considered. The model is established according to the structure of the micro-channel dehumidifier, and the corresponding relationship between the pressure of the wet air entering the micro-channel dehumidifier and the humidity of the air output by the micro-channel dehumidifier can be calculated according to different air conditions (the temperature and humidity of the wet air) and the structure size of the micro-channel dehumidifier, so that the pressure can be adjusted according to the target humidity of the air, and the dehumidification process is more accurate and flexible.

[0145] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above-mentioned specific embodiments, and the above-mentioned specific embodiments and the description in the specification are only for further illustration of the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application.

Claims

1. A method of regulating a variable pressure microchannel condensing dehumidification apparatus, comprising: The variable-pressure micro-channel condensation dehumidification device comprises a compressor (1), a micro-channel dehumidifier (2), a first gas-liquid separator (3) and an expander (6), an air inlet pipe is connected with an air inlet of the compressor (1), an air outlet of the compressor (1) is connected with an air inlet of the micro-channel dehumidifier (2), an air outlet of the micro-channel dehumidifier (2) is connected with an inlet of the first gas-liquid separator (3), an air outlet of the first gas-liquid separator (3) is connected with an air inlet of the expander (6), and an air outlet of the expander (6) is connected with an air outlet pipe; The micro-channel dehumidifier (2) comprises a first channel layer (21) and a second channel layer (22) arranged in layers, and the first channel layer (21) and the second channel layer (22) are each provided with a plurality of micro-channels; the inlet of the first channel layer (21) is connected with the air outlet of the compressor (1) as the air inlet of the micro-channel dehumidifier (2), and the outlet of the first channel layer (21) is connected with the inlet of the first gas-liquid separator (3) as the air outlet of the micro-channel dehumidifier (2); the diameters of the micro-channels of the first channel layer (21) gradually increase along the air flow direction; The control method comprises the following steps: Step 10, establishing a wet air positive pressure condensation dehumidification heat and mass transfer model; Step 20, according to the structural parameters of the micro-channel dehumidifier (2) and the wet air property parameters including the wet air pressure entering the micro-channel dehumidifier (2), the wet air positive pressure condensation dehumidification heat and mass transfer model is used to calculate the air humidity output by the micro-channel dehumidifier (2) under different wet air pressures, and the corresponding relationship between the wet air pressure entering the micro-channel dehumidifier (2) and the air humidity output by the micro-channel dehumidifier (2) is obtained; Step 30, according to the corresponding relationship between the wet air pressure entering the micro-channel dehumidifier (2) and the air humidity output by the micro-channel dehumidifier (2), a preset wet air pressure range corresponding to the target air humidity is obtained, and the compressor is controlled so that the wet air pressure entering the micro-channel dehumidifier (2) is within the preset wet air pressure range; The wet air positive pressure condensation dehumidification heat and mass transfer model comprises a single droplet model, a droplet growth model and a channel condensation model; The expression of the single droplet model is formula (1) to formula (4): Formula (1) Equation (2) Equation (3) Equation (4) wherein represents the mass flux through the Knudsen layer, represents the Knudsen layer radius, represents the Knudsen layer vapor density, represents the gas constant, represents the Knudsen layer surface temperature, represents the droplet density, represents the droplet radius, represents the droplet surface temperature; represents the mass flux from the continuous region to the Knudsen layer, represents the water vapor diffusion coefficient, represents the moist air density, represents the moist air vapor partial density; represents the heat flux to a single droplet growing to represents the heat flux to a single droplet growing to represents the thermal conductivity of water, represents the cold wall surface temperature; represents the mass flux to a single droplet growing to represents the mass flux to a single droplet growing to represents the latent heat of condensation per unit time; The expression of the droplet growth model is formula (5) to formula (12): Equation (5) Equation (6) Equation (7) Equation (8) Equation (9) Equation (10) Equation (11) Equation (12) wherein represents the total heat transfer rate for the droplet growth process, A represents the sum of the cylindrical surface areas of all the microchannels of the first channel layer of the microchannel dehumidifier, represents the heat transfer rate at the droplet radius corresponding to a certain time, represents the time for the droplet coalescence process, represents the time for the droplet slide-off process, m represents the total number of droplets; represents the total mass transfer rate for the droplet growth process, represents the mass transfer rate at the droplet radius corresponding to a certain time; The expression of the channel condensation model is formula (13) to formula (17): Equation (13) Equation (14) Equation (15) Equation (16) Equation (17) Equation (18) Equation (19) Equation (20) Equation (21) Equation (22) Equation (23) wherein represents the second channel layer convective heat transfer coefficient, represents the Nusselt number of the cooling water, represents the diameter of the microchannel of the second channel layer; represents the first channel layer convective heat transfer coefficient, represents the Nusselt number of the air, represents the thermal conductivity of the air, represents the average diameter of the microchannel of the first channel layer, , represents the inlet diameter of the microchannel of the first channel layer; represents the convective heat transfer coefficient of the wet air and the baffle, represents the baffle thickness, represents the thermal conductivity of the copper; represents the convective heat transfer rate between the wet air and the baffle, represents the temperature of the wet air, represents the temperature of the cooling water; represents the heat transfer rate of the i-th microchannel segment, represents the convective heat transfer rate between the wet air and the baffle in the i-th microchannel segment, represents the total heat transfer rate of the droplet growth process in the i-th microchannel segment, represents the mass transfer rate of the i-th microchannel segment, represents the total mass transfer rate of the droplet growth process in the i-th microchannel segment; represents the heat transfer flux of the i-th microchannel segment, represents the cylindrical surface area of the i-th microchannel segment of the first channel layer of the microchannel dehumidifier, represents the mass flux of the i-th microchannel segment; represents the enthalpy of the i-th microchannel segment outlet wet air, represents the enthalpy of the i-1-th microchannel segment outlet wet air, represents the wet air mass flow rate, represents the dry air mass flow rate, represents the i-th microchannel segment outlet wet air moisture content, represents the i-1-th microchannel segment outlet wet air moisture content, represents the i-th microchannel segment outlet wet air temperature; The step 20 specifically comprises: Step 201, initializing droplet state parameters; Step 202, using an iterative method, aiming to make the calculation results of formula (1), formula (2) and formula (4) the same, the droplet state parameters are calculated; the droplet state parameters are compared with the initialized droplet state parameters, if the error condition is not met, the droplet state parameters are reinitialized by using a dichotomy method, and step 202 is executed; if the error condition is met, step 203 is executed; Step 203, the heat flux and the mass flux generated by a single droplet are calculated by using formula (3) and formula (4); according to the heat flux and the mass flux generated by a single droplet, the total heat flux and the total mass flux in the droplet growth process are calculated by using the droplet growth model; In step 204, the air humidity at the outlet of the micro-channel dehumidifier under different wet air pressures is calculated by using the micro-element method and the channel condensation model according to the total heat flux and mass flux of the droplet growth process and the wet air property parameters, wherein the wet air property parameters include the wet air pressure, the wet air temperature and the wet air humidity entering the micro-channel dehumidifier (2). In step 205, the corresponding relationship between the wet air pressure and the air humidity is obtained. The step 204 specifically comprises: The micro-channel of the micro-channel dehumidifier is differentiated, the total heat flux and mass flux of the droplet growth process obtained in step 203 are taken as the heat flux and mass flux of the air passing through the first micro-channel section under the initial state, the wet air pressure, the wet air temperature and the wet air humidity entering the micro-channel dehumidifier (2) are given, the enthalpy, the moisture content and the temperature of the air at the outlet of the first micro-channel section are calculated by using formulas (21)-(23), the heat flux and mass flux of the second micro-channel section are calculated by using formulas (13)-(20), the enthalpy, the moisture content and the temperature of the air at the outlet of the second micro-channel section are calculated by using formulas (21)-(23), and the heat flux and mass flux of each micro-channel section and the enthalpy, the moisture content and the temperature of the air at the outlet are calculated in sequence; the wet air humidity and the wet air temperature remain unchanged, the wet air pressure entering the micro-channel dehumidifier (2) is given again, and the heat flux and mass flux of each micro-channel section and the enthalpy, the moisture content and the temperature of the air at the outlet are calculated in sequence; and thus the air humidity at the outlet of the micro-channel dehumidifier under different wet air pressures is obtained.

2. The method of claim 1, wherein, The corresponding relationship between the wet air pressure and the air humidity at the outlet of the micro-channel dehumidifier is that when the wet air pressure is 160-300 kPa, the air humidity at the outlet of the micro-channel dehumidifier is 15.6-10.9 g / kg.

3. The method of claim 1, wherein the step of modulating comprises: The variable-pressure micro-channel condensation dehumidification device further comprises an air-air heat exchanger (4) and a second gas-liquid separator (5), and the outlet of the first gas-liquid separator (3) is connected with the inlet of the expander (6), specifically, the outlet of the first gas-liquid separator (3) is connected with the first inlet of the air-air heat exchanger (4), the first outlet of the air-air heat exchanger (4) is connected with the inlet of the second gas-liquid separator (5), and the outlet of the second gas-liquid separator (5) is connected with the inlet of the expander (6); and the outlet of the expander (6) is connected with the outlet pipe, specifically, the outlet of the expander (6) is connected with the second inlet of the air-air heat exchanger (4), and the second outlet of the air-air heat exchanger (4) is connected with the outlet pipe.

4. The method of claim 1, wherein the step of modulating comprises: The cooling working medium of the micro-channel dehumidifier (2) uses a natural cold source or is provided by an evaporative cooling tower.

5. The method of claim 1, wherein the step of modulating comprises: The variable-pressure micro-channel condensation dehumidification device further comprises an electric motor (7), the input end of the electric motor (7) is connected with the expander (6), and the output end of the electric motor (7) is connected with the compressor (1).

Images