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Numerical analysis of a desiccant-based dehumidification system employing membrane contactors


   School of Computing and Engineering

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  Dr Faisal Asfand, Prof Rakesh Mishra  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

Huddersfield United Kingdom Biomedical Engineering Chemical Engineering Electrical Engineering Energy Technologies Mechanical Engineering Architecture, Building & Planning Computer Science

About the Project

The liquid desiccant dehumidification systems have been widely adopted both in the industrial and residential sector to absorb the moisture content using an absorbent solution and to control the indoor air humidity, respectively. The dehumidifier is one of the essential parts of these systems, which severely affects the whole system performance and size. In addition to higher consumption of energy, the size of the dehumidifier is usually bigger in order to provide higher surface area for contact between the liquid desiccant and the process air. Moreover, in the conventional desiccant-based dehumidification systems, the liquid desiccant is in direct contact with the process air. This can lead to the contamination of the process air by the liquid desiccant droplets crossover and therefore small liquid desiccant droplets may be carried over by the process air to indoor environment, which could be rather harmful to occupants. Recent studies have shown that the use of membrane contactors can allow the development of innovative dehumidifier for non-contacting air dehumidification. In addition, the larger surface area provided by the membrane contactors can allow the development of compact dehumidifier with enhanced performance. This study aims to perform modelling and simulation of a membrane based liquid desiccant dehumidification system in order to analyse the absorption performance of the membrane-based dehumidifier.

This work aims to analyse in detail the absorption process of a membrane based liquid desiccant dehumidification system by developing a CFD model and a numerical model based on global mass and energy equations for global analysis. The following objectives will be targeted in this work.

·    Developing a steady-state 1-D global model in MATLAB to acquire the basic understanding of the absorption process in a membrane based liquid desiccant dehumidification system and to investigate the effect of different operating and design parameters on the absorption performance.

·    Implementation of the global model based on mass and energy balance equations in the thermodynamic simulation of a membrane based liquid desiccant dehumidification system to evaluate the performance of the complete system and compare the performance with that of the commercial unit operating with conventional dehumidifier.

·    Developing a numerical model of the membrane-based dehumidifier using CFD approach for detail heat and mass transfer analysis. The optimized design parameters and operating conditions obtained from the global model and system simulation will be used as input conditions in the detailed modelling.

·    Performing numerical simulations to investigate the absorption performance of a membrane based liquid desiccant dehumidification system using potential novel working fluid mixtures.

The first objective of this research proposal is to acquire the basic understanding of the membrane based liquid desiccant dehumidification system and to obtain optimized input condition for the detail modelling. To achieve this, a steady-state 1-D global model will be used to investigate the effect of different operating and design parameters on the absorption performance. Further, ASPEN Plus process simulation tool will be used to perform steady-state thermodynamic analysis of a liquid desiccant dehumidification system employing membrane-based dehumidifier. The input variables for the thermodynamic simulation will be adopted similar to that of a commercial liquid desiccant dehumidification system. The effect of process air quality (humidity level) on the dehumidifier size will be studied and the design parameters will be optimized to achieve a compact dehumidifier.

Moreover, a CFD based solver will be used to carry out detailed heat and mass transfer analyses. The optimized design parameters and operating conditions obtained from the global model and system simulation will be used as input conditions in CFD simulations. CFD analysis can provide a sound foundation to investigate in detail the fluid dynamics behaviour and the heat and mass transfer processes at local levels to better understand the phenomenon and the effect of flow parameters. Potential working fluid mixtures will be investigated, and numerical analysis will be carried out to compare and evaluate the performance of the system with these working fluid mixtures.

The simulation results will be validated with the experimental data. For this purpose, a lab-scale setup will be built. In case of exceptional circumstances, validation of the numerical model can be performed using the available literature data.

This work will provide a sound foundation to investigate in detail the performance of a membrane based liquid desiccant dehumidification system. Furthermore, this study will recommend optimum operating and design parameters for new working fluids. Expected results of this study can help in designing a compact and an efficient membrane based liquid desiccant dehumidifier for dehumidification systems that can maintain the air quality in commercial buildings, hospitals, and commercial aeroplanes etc.

The Huddersfield Smart House Research Facility is being developed as a collaborative hub for industry, academia and government organisations. It is being developed to accelerate research and development for smart products and services to be used in the building environment with an aim to bring transformational improvements in key performance indicators corresponding to 21st century houses and living conditions. For this purpose, a well instrumented two storey dwelling is being constructed that will provide facilities for a range of novel and innovative investigations to be carried out.

Smart technologies can help us in reducing carbon footprints as well as having positive energy balance through improved energy performance of homes and buildings. We can achieve greater energy efficiency, cut carbon emissions and support more intelligent and flexible management of energy supply and demand. By incorporating use of smart technologies, the health and wellbeing can be significantly improved through better management of internal environments, safety and security. Smart technologies have potential to offer significant improvements in wellbeing of the occupants by allowing control through voice and mobile apps as well as using automation and artificial intelligence to support and predict our changing needs.

HSHRF aims to bring researchers, practitioners, industries and government organisations together to design, develop and implement holistic solutions to current and future societal challenges associated with building environment and its use.

Applications

Applications must be made through the University of Huddersfield Online Application portal:

 

https://uoh-onlineapps.hud.ac.uk/


Funding Notes

The Huddersfield Smart House Research Facility is looking to award four Smart House Scholarships to exceptional applicants. Each Smart House Scholarship will provide a full fee waiver to the successful candidate. The Scholarships do not include a bursary or stipend. The Interviews will take place on Thursday 1st and Friday 2nd July 2021.