Session Q06: Industrial Applications: General

Numerical investigation of high capacity ground-coupled heat exchanger performance for water cooled chillers services

Ground coupled heat exchanger (GCHE) has received considerable attention with the increased demand on energy efficiency to combat global warming. Among other applications, GCHE has a promising potential as a heat rejection method for chillers especially in hot and humid climates where cooling towers are not very effective such as the case of the Gulf countries. In this work, a transient axisymmetric numerical model to simulate the heat transfer and turbulent flow through coaxial borehole ground heat exchanger is developed. The present study is aimed at improving our understanding of the parameters controlling the heat transfer from the GCHE to serve large capacity chillers under hot and wet climate condition. Parameters such as borehole size, exchanger depth and inner‒outer pipe diameter ratio are optimized to maximize the heat transfer. For validation, the present results of a deep small diameter heat exchanger are compared with experimental and numerical data reported in the literature.  For further enhancement of the performance, a novel idea, helical digging threading fins configuration (HDTFC), is employed with GCHE to enhance the heat rejection into the ground using the extended surfaces (fins) and to facilitate the ground digging process for the heat exchanger installment.   

Direct numerical simulations of heat and mass transport in membrane distillation systems

Membrane distillation (MD) is an emerging process for desalinating hypersaline brines. The process flows warm brine and cool distillate water on opposite sides of a hydrophobic membrane. The temperature difference causes water to evaporate from the brine, travel as vapor through the membrane, and condense in the distillate. Two major challenges for MD are temperature and concentration polarization. Temperature polarization represents a reduction in the transmembrane temperature difference due to heat transfer through the membrane. Concentration polarization describes the accumulation of solutes near the membrane, which leads to undesirable salt precipitation. We develop an in-house CFD method to simulate 2-D and 3- D unsteady heat and mass transport within plate-and-frame MD systems. The coupled momentum, energy, and mass transport equations are solved with an efficient projection method. For the 2-D simulations, we perform a parametric study of temperature and concentration polarization under a variety of operating conditions. We show that the temperature and concentration boundary layers show self-similar behavior that satisfies power laws for the downstream growth. We also present 3-D results demonstrating polarization occurring both in the downstream and lateral directions.   

A simplified route to manufacturing microstructured optical fibres

Microstructured optical fibres (MOFs) are used widely in the communications industry for the transmission of data signals. They are typically constructed from glass via a drawing process and their resulting cross-sections comprising a complex array of holes and interconnecting glass 'struts'. But how do we make a MOF with a desired final cross-sectional configuration?  We present a model for the surface-tension-driven evolution of the viscous struts, or viscidas, and the connecting junctions, which bears similarities to  network models used for foam dynamics. A degeneracy in the model highlights the need for care when constructing the model. Crucially, the theory provides a simplified framework for predicting the evolution of a complex MOF cross-section during the drawing process. Moreover, the model is well-posed for inverse time, allowing us to predict the start configuration required to generate a desired final cross-sectional profile.    

The Use of 3D Printed Impellers in Small Industrial Pump Testing

H20 for Humanity is a non-profit organization that provides small scale water treatment facilities to rural villages in India. These facilities currently use a 120 psi pump operating at 25% efficiency to provide water to a reverse osmosis filter. To improve the system performance, the pump impellers were redesigned to utilize an increased pump speed. The newly designed impellers were manufactured with a 3D printer to reduce manufacturing cost and enable rapid prototyping. One of the purposes of the experiment was to determine whether 3D printed impellers were an effective method of testing pump performance. It was concluded that 3D printed impellers appropriately represent the injection molded impellers. The 3D printed impellers matched the performance of the injection molded impellers with a difference of  1.8% when compared to the experimental data collected by the injection molded impellers. 3D printing is not without challenges. There are a myriad of print settings that required customization in order to achieve a quality printed impeller. Additionally, the inlet cavitation limit for the 3D printed impellers closely matched the performance of the injection molded impellers.    

Design and Modeling and a Passive Carbon Capture Device

The atmospheric level of CO2 has increased at an alarming rate in the past 100 years, so much that its impact can be seen in melting ice caps, changing weather patterns, and enormous loss of marine life. Almost all nations are concerned with curbing the CO2 emissions and efforts are made to bring them to sustainable levels. However, emerging economies, such as China and India, that use fossil fuels as their primary energy source, have difficult time to balance the energy needs of large populations and reducing fossil fuel impact on environment. Fortunately, there has been considerable interest in recent years to reduce the current CO2 levels through active extraction from atmospheric air. However, one of the major drawbacks with these efforts is energy consumption for active extraction. In our research, an effort has been made to design, model and test a small-scale passive CO2 extraction devise. It consumes significantly less amount of energy compared to an active extraction device working within similar constraints. After successful testing, the design will be modified for industrial scale and mass production.