Wang, Yuhao
(2023)
A heat pipe internally-cooled membrane-based liquid desiccant dehumidification system.
PhD thesis, University of Nottingham.
Abstract
In recent years, membrane-based liquid desiccant dehumidification has emerged as an efficient approach for air humidity control in building air conditioning process, in which the internally-cooled liquid desiccant dehumidifier is regarded as an energy-efficient device with high dehumidification effectiveness and cooling performance.
This research project aims at investigating the dehumidification and cooling performance of a heat pipe internally-cooled liquid membrane-based desiccant dehumidification (HP-ICMLDD) system and its application in multi-family terraced houses under subtropical and humid Mediterranean climate conditions. The project also develops an integrated liquid desiccant air-conditioning (ILDAC) system by combining the HP-ICMLDD system with an air-water heat pump (AWHP), photovoltaics-thermal (PVT), and hot water storage.
An innovative HP-ICMLDD system is established by integrating the heat pipe internal cooling method with the dehumidification system, where experimental investigation is conducted. Moreover, the energy simulation of the building with the ILDAC system has been conducted via the IES VE and EnergyPro software using the reference buildings (RBs) in Spain, Italy and Greece.
The research output indicates that the dehumidification performance is influenced by the heat pipe's internal cooling effect, which is significantly improved by reducing the cold water temperature and increasing the cold water flow rate. The optimal operating conditions for the complete LDD system have been determined. For the dehumidifier in the HP-ICMLDD system, the optimal inlet cold water temperature, mass flow rate, solution temperature and solution concentration are 18 ℃, 0.017 kg/s, 18℃, 32%, respectively; For the regenerator in the system, the optimal solution temperature is 55 ℃. The correlations of thermal, electrical, total COP, air temperature and relative humidity at the dehumidifier outlet with the inlet air conditions have been generated using the linear regression method. It is found that the ILDAC system COP rises with the increasing inlet air temperature and relative humidity.
By comparing the energy consumption of the residential building without and with the ILDAC system in three different locations, the building energy consumption is reduced by 77.6%, 74.8% and 78.8% in Barcelona, Rome and Methoni, and the corresponding carbon reduction rate is 88.8%, 84.3% and 76.9%. The ILDAC system could achieve higher COP of 6.41, 8.14 and 7.52 in Barcelona, Rome and Methoni, which are significantly higher than those of the complete LDD and AWHP systems. The discounted payback period varies between 7 and 9 years, with the annual return on investment ranging from 8.40% to 11.90%. Moreover, it is appropriate to invest in the ILDAC system in Spain, Italy and Greece when the inflation rates fall between -6.80% and 12.20%, -6.90% and 12.20%, and -5.40% and 8.70%, respectively.
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