Document Details

Document Type : Thesis 
Document Title :
MODELING OF FLUID FLOW AND HEAT TRANSFER IN DIRECT CONTACT MEMBRANE DISTILLATION
نمذجة تدفق المائع وانتقال الحرارة في عملية تقطير غشائي ذو اتصال مباشر
 
Subject : Faculty of Engineering 
Document Language : Arabic 
Abstract : Direct contact membrane distillation (DCMD) is a comparatively modern method, which is being adopted and explored internationally since it is inexpensive and energy efficient compared to existing desalination techniques. This technique of (DCMD) in both sides of membrane in direct connection with hot feed water side and cold permeate side. Vapour passes through the hydrophobic porous membrane due to the variation in temperature, which leads to a difference in vapour pressure (the driving force). In this study, we consider single spacer geometry and adopt a numerical approach using computational fluid dynamics (CFD) in OpenFOAM software to focus on a feed channel filled with spacers of the same diameter. The distances between the spacers are fixed in two dimensions under different conditions. These are characterized by heat transfer coefficient (HTC) and pressure gradient (∆P/∆x) and mathematical modeling is used to solve the governing equations (Navier¬–Stokes and heat transport) subject to appropriate boundary conditions to obtain velocity and temperature fields, before a post-process is undertaken to achieve the desired quantities (HTC and ∆P/∆x). The purpose of using spacers to enhance convective heat transfer is that they increase velocity and decrease temperature polarization, maintaining the value of the driving force and enhancing the vapour flux process of the DCMD modules. This can, furthermore, result in raising the efficiency of energy utilization for the separation process. DCMD modules use different boundary conditions of constant heat flux with a uniform inlet temperature profile and other boundary conditions (such as constant heat flux - variable heat flux with conduction only - variable heat flux with latent heat) with a fully developed inlet temperature profile. The objective of this study is to verify the impacts of the spacers’ geometrical characteristics and boundary conditions on HTC and pressure gradient. The HTC is significantly higher in the developing boundary layer region than it is in the fully developed region. In an analysis of a fully developed temperature profile as the inlet boundary conditions, much more reasonable values for the HTC were obtained, which is consistent with fully developed laminar convection in a plain channel between two infinite parallel plates with uniform heat flux boundary conditions. The slightly higher value obtained can be attributed to the presence of the spacers. Cases simulating both vaporization and heat conduction through the walls showed much more variation in the temperature field than in all the other cases. The heat flux associated with water vaporization is much higher than in previous cases, and increases further with the Reynolds number are compared of the cases of conduction only. This means that a higher heat flux is generated as the Reynolds number increases. The pressure drop data for the three temperatures considered collapse into one curve, confirming that the power number depends only on the Reynolds number. The results show that flow hydrodynamics are not temperature dependent. 
Supervisor : Prof. Mohammed AL-Beiruti 
Thesis Type : Master Thesis 
Publishing Year : 1438 AH
2016 AD 
Added Date : Wednesday, January 11, 2017 

Researchers

Researcher Name (Arabic)Researcher Name (English)Researcher TypeDr GradeEmail
بندر عبدالوهاب مجيدMajeed, Bandar AbdulwahabResearcherMaster 

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