Development of a desiccant system for space air conditioning using metal-organic framework materials

Makar, Andrew Nabil Aziz ORCID: 0000-0003-4184-3322 (2024). Development of a desiccant system for space air conditioning using metal-organic framework materials. University of Birmingham. Ph.D.

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Abstract

Metal-Organic Frameworks (MOFs) are very promising materials for improving the effectiveness of desiccant air conditioning systems due to their outstanding ability to adsorb moisture, adjustable features, and potential for sustainable heating and cooling applications. This study examines the incorporation of Metal-Organic Frameworks (MOFs) into desiccant systems to achieve energy-efficient control of indoor humidity and temperature, thus positively impacting occupants' health and comfort. Through a comprehensive literature review, several MOFs were identified and numerically and experimentally investigated in terms of moisture removal rate from air. MOF-303/G was identified as the best candidate adsorbent for this application. Various heat exchangers were considered, and the wire-finned heat exchanger was identified as the most efficient for coating with the identified MOF- 303/G. An advanced computational fluid dynamics model of MOF-303/G coated wire-finned tube was created using COMSOL Multiphysics software. This model accurately simulates the heat and mass transfer process between the MOF material and the air and the heat transfer between the MOF material and the metal heat exchanger under different operating scenarios. In addition, a novel heating process for the MOF-coated heat exchanger was developed utilising electrical DC to optimise the heat transfer and energy consumption. The developed DCHE's experimental testing confirmed the dynamic of the adsorption- desorption processes and validated the CFD model. The model-predicted water uptake during the adsorption process with the experimental measurements with time, showing good agreement with a maximum deviation of ±6% Use the developed MOF-303/G DCHE to construct the desiccant air conditioning system consisting of an array of DCHEs, a direct evaporative cooler, an air-to-water heat exchanger, ducting and an automatic control system. The system was tested to achieve the comfort conditions for a 2m3 room. Results showed that the developed system effectively attained the ASHRAE comfort standards by consistently maintaining a steady indoor environment with a temperature of 25-28°C and a relative humidity of 50-60% at air ambient conditions ranging from 10-35°C and 50-80% with system COP ranging 0.7-1.54. This performance illustrates the system's capability to achieve the target indoor comfort conditions with lower energy consumption. The desiccant air conditioning system significantly reduced power consumption for heating, with a decrease of 74%, and for cooling, with a decrease of 66%, compared to a 2 kW vapour compression air conditioner (split type). Such results highlight the potential of the developed system in terms of energy savings and independent control of indoor temperature and humidity for climate control in residential, commercial, and agricultural environments.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):