| Dehumidification technology is one of the key technologies in temperature and humidity independent control air-conditioning systems.The traditional temperature and humidity independent control air-conditioning systems use solid or liquid desiccant to achieve dehumidification and use a low-grade heat source to achieve desiccant regeneration at the same time,so it has a remarkable energy-saving effect.However,the solid and liquid desiccant dehumidification systems are generally large and have high requirements for the low-grade heat source,which limits the further application of temperature and humidity independent control technology.Therefore,it is necessary to develop a dehumidification air-conditioning technology with compact structure,energy-saving,and a wide range of adaptation.Vacuum membrane-based dehumidification air-conditioning technology is an emerging air-conditioning technology,which uses vacuum membrane-based dehumidification devices and airconditioning refrigeration devices to achieve independent control of indoor temperature and humidity.It is suitable for environments where the control accuracy of temperature and humidity is high,and for environments with insufficient low-grade heat sources.Vacuum membrane-based dehumidification technology uses a water vapor selective permeation membrane to absorb water vapor from the air and simultaneously uses a vacuum pump to achieve regeneration.To demonstrate the thermodynamic feasibility of vacuum membrane dehumidification air-conditioning system,this paper constructs two different types of novel temperature and humidity independent control air-conditioning systems based on vacuum membrane-based dehumidification.Besides,this work explores the thermodynamic characteristics of the two novel vacuum membrane-based dehumidification air-conditioning systems from the system scale.Moreover,to further clarify the theoretical direction for improving the dehumidification performance of vacuum membrane-based dehumidification air-conditioning systems,the microscopic flow and mass transfer mechanism of the dehumidification process of the curved vacuum membrane-based dehumidification module is revealed.Finally,to further enhance the applicability of vacuum membrane-based dehumidification air-conditioning systems in the HVAC field,the dehumidification performance of a novel low-selective vacuum dehumidification membrane is investigated from the perspective of the preparation and regulation.The main work of this paper includes as follows.(1)To analyze the thermodynamic feasibility of the vacuum membrane-based dehumidification air-conditioning system,a novel vacuum membrane-based dehumidification air-conditioning system(VMD-ACER)is proposed,which integrates vacuum membrane-based dehumidification and air carrying energy radiant air-conditioning system.The VMD-ACER system ensures indoor comfort while achieving the energy-saving target,and it can be utilized for winter heating and summer cooling,so the VMD-ACER system is expected to extend the application scope of temperature and humidity independent control air-conditioning system.A thermodynamic model of the VMD-ACER system is developed and validated.The degree of influence of operating parameters on the performance of the conventional fan coil airconditioning system and the VMD-ACER system was evaluated.The energy-saving of the conventional fan coil air-conditioning system and the VMD-ACER system were compared.It is found that the COP of the VMD-ACER system is higher than that of the fan coil air conditioning system when the permeate side pressure is greater than 8 k Pa,which proves the energy-saving potential of the VMD-ACER system.(2)To reduce the dependence of the vacuum membrane-based dehumidification air conditioning system on conventional organic refrigerants,a novel vacuum membrane-based dehumidification air conditioning system(DAV)is proposed,which integrates dew point evaporative cooling,air carrying energy radiant-conditioning,and vacuum membrane-based dehumidification.The DAV system does not use any organic refrigerant and couples the cooling process with the fresh air supply process,so it can effectively prevent the operation manager from reducing the fresh air ratio at will.In addition,the DAV system is flexible in regulation and can meet the cooling requirements of different environments.The thermodynamic model of the DAV system is established and validated.The parameters of the DAV system were systematically analyzed to reveal the basic laws of DAV system operation and regulation.When the permeate side pressure is 20 k Pa,the COP of the DAV system in Singapore and Changsha area are 5～7 and 4.5～9,respectively,and the energy-saving potential of the DAV system is demonstrated.The engineering design method of the DAV system is discussed,and a design scheme for independent control of temperature and humidity of the DAV system is proposed.(3)To investigate the flow and mass transfer mechanism of curved vacuum membranebased dehumidification modules,a numerical calculation method applicable to the vacuum membrane-based dehumidification process is proposed based on gas dynamic theory.The importance of the phase equilibrium effect in the dehumidification process of vacuum membrane-based dehumidification is analyzed,and an inversion method is proposed for predicting the apparent water vapor permeance under the phase equilibrium effect.The results show that the phase equilibrium effect has a positive impact on the dehumidification process of vacuum membrane-based dehumidification,and it can improve the dehumidification efficiency by 4.65%～8.22%,and the apparent water vapor permeability calculated by the inverse method is 61% higher than that measured by the conventional cup method.Based on the proposed numerical calculation method,the dehumidification performance and flow mass transfer mechanism of vacuum membrane-based dehumidification modules with different curved structures such as convexly curved membrane,concavely curved membrane,spiral fin curved membrane,straight fin curved membrane,and wavy membrane are studied,which provide theoretical references for structural optimization of vacuum membrane-based dehumidification modules and further improvement of dehumidification performance of vacuum membranebased dehumidification air conditioning systems.(4)To further enhance the adaptability of vacuum membrane-based dehumidification air conditioning systems in the HVAC field,a novel preparation method of low-selective vacuum dehumidification membrane is proposed.An experimental test method for the low-selective vacuum membrane-based dehumidification system is established and an experimental platform is built.A test software of vacuum membrane-based dehumidification system is developed.The influence of some key parameters such as vacuum degree on the permeation side,wet air flow rate,and Li Cl content in the casting film solution on the dehumidification process is studied,and the feasibility of the proposed novel low-selective vacuum dehumidification membrane is demonstrated.The dynamic response law of the vacuum membrane-based dehumidification process is investigated through experimental tests,and the flow mass transfer mechanism of the low-selective vacuum membrane-based dehumidification module is further studied based on the CFD method to provide theoretical reference for the application of vacuum membranebased dehumidification air conditioning system.This paper demonstrates the thermodynamic feasibility of vacuum membrane-based dehumidification air conditioning system,systematically investigates the flow and mass transfer law of curved vacuum membrane-based dehumidification modules,develops a vacuum dehumidification membrane especially suitable for HVAC environment and establishes the corresponding experimental test and numerical calculation methods,which are of great theoretical significance to realize the green and low-carbon development in HVAC field. |
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