A numerical study on heat transfer enhancement and design of a heat exchanger with porous media in continuous hydrothermal flow synthesis system

The aim of this study is to use a new configuration of porous media in a heat exchanger in continuous hydrothermal flow synthesis(CHFS)system to enhance the heat transfer and minimize the required length of the heat exchanger.For this purpose,numerous numerical simulations are performed to investigate performance of the system with porous media.First,the numerical simulation for the heat exchanger in CHFS system is validated by experimental data.Then,porous media is added to the system and six different thicknesses for the porous media are examined to obtain the optimum thickness,based on the minimum required length of the heat exchanger.Finally,by changing the flow rate and inlet temperature of the product as well as the cooling water flow rate,the minimum required length of the heat exchanger with porous media for various inlet conditions is assessed.The investigations indicate that using porous media with the proper thickness in the heat exchanger increases the cooling rate of the product by almost 40% and reduces the required length of the heat exchanger by approximately 35%.The results also illustrate that the most proper thickness of the porous media is approximately equal to 90% of the product tube's thickness.Results of this study lead to design a porous heat exchanger in CHFS system for various inlet conditions.

Combinatorial Performance Mapping of Near-NMC111 Li-ion Cathodes

A combinatorial library of twenty-three,phase pure,near-NMC111(LiNi_(0.33) Mn_(0.33)Co_(0,33)O_(2))composi-tions were synthesised and their electrochemical performance,was mapped(in lithium ion half-cells).Each of the 23 compositions was made in series,using a two-step process of 1)a rapid initial contin-uous hydrothermal precipitation,followed by 2)solid state lithiation.The 23 lithiated NMC samples were then subjected to analytical methods including electron microscopy(selected samples),Powder X-ray Diffraction and electrochemical tests in half cell Li-ion configurations versus Li metal.A sample with a Ni:Mn:Co(NMC)ratio of 39:28:33,revealed a specific capacity of 150 mA h g^(-1) at a C/20 rate,which was 63 and 43% greater capacity than NMC111 and NMC433 samples produced in this work,respectively.The sample with NMC ratio 47:25:28,showed the best capacity retention characteristics,retaining 70%of its C/20 capacity at 1C,after 40 cycles.Further analysis of all the samples by cyclic voltammetry and elec-trochemical impedance spectroscopy,allowed compositional mapping of diffusion coefficients.Overall,the mapping data revealed a gradual change of properties across compositional space,which has vali-dated our combinatorial approach and allowed identification of the optimum performing near-NMC111 cathode materials.