This paper presents new results for the dynamic behaviour of fluid around a rotating turbulator in a channel. The turbulator has a propeller form which is placed inside a flat channel. The research was carried out using 3D numerical simulation. The rationale of the experiment was as follows: we put a propeller-turbulator inside a flat channel, and then we insert a water flow inside the channel. The turbulator rotates at a constant and uniform speed. The main points studied here are the effect of the presence of turbulator and its rotational direction on the flow behaviour behind the turbulator. The results showed that the behaviour of flow behind the turbulator is mainly related to the direction of turbulator rotating. Also, the studied parameters affect coefficients of drag force and power number. For example, when the turbulator rotates in the positive direction, the drag coefficient decreases in terms of rotational speed of the turbulator, while the drag coefficient increases in terms of rotational speed when the turbulator rotates in the negative direction.

This paper presents a comparative study on the effects of the in-situ surface modifications performed on “H” type microfluidic systems obtained via additive manufacturing. The microsystem was printed using a polylactic acid filament on an Ender-5 Pro printer. The surface modification of the main channel was done using chloroform by two different methods: vapor smoothing and flushing. The obtained surface roughness was studied using an optical microscope and the ImageJ software, as well as scanning electron microscopy. The effect of the channel surface treatment upon the characteristics of the fluid flow was assessed. The microfluidic systems were used for the dynamic study of biofilm growth of Candida albicans (ATCC 10231). The influence of the surface roughness of the main channel on the formation and growth of the biofilm was studied using quantitative methods, scanning electron microscopy imaging as well as optical coherence tomography.

The paper presents two analytical solutions namely for Fanning friction factor and for Nusselt number of fully developed laminar fluid flow in straight mini channels with rectangular cross-section. This type of channels is common in mini- and microchannel heat exchangers. Analytical formulae, both for velocity and temperature profiles, were obtained in the explicit form of two terms. The first term is an asymptotic solution of laminar flow between parallel plates. The second one is a rapidly convergent series. This series becomes zero as the cross-section aspect ratio goes to infinity. This clear mathematical form is also inherited by the formulae for friction factor and Nusselt number. As the boundary conditions for velocity and temperature profiles no-slip and peripherally constant temperature with axially constant heat flux were assumed (H1 type). The velocity profile is assumed to be independent of the temperature profile. The assumption of constant temperature at the channel’s perimeter is related to the asymptotic case of channel’s wall thermal resistance: infinite in the axial direction and zero in the peripheral one. It represents typical conditions in a minichannel heat exchanger made of metal.

A passive autocatalytic hydrogen recombiner (PAR) is a self-starting device, without operator action or external power input, installed in nuclear power plants to remove hydrogen from the containment building of a nuclear reactor. A new mechanistic model of PAR has been presented and validated by experimental data and results of Computational Fluid Dynamics (CFD) simulations. The model allows to quickly and accurately predict gas temperature and composition, catalyst temperature and hydrogen recombination rate. It is assumed in the model that an exothermic recombination reaction of hydrogen and oxygen proceeds at the catalyst surface only, while processes of heat and mass transport occur by assisted natural and forced convection in non-isothermal and laminar gas flow conditions in vertical channels between catalyst plates. The model accounts for heat radiation from a hot catalyst surface and has no adjustable parameters. It can be combined with an equation of chimney draft and become a useful engineering tool for selection and optimisation of catalytic recombiner geometry.

This study presents the behavior of a single wall carbon nanotube (SWCNT)/water nanofluid for convective laminar flow inside a straight circular pipe heated by a constant heat flux. Five volume fractions of SWCNT were used to investigate their effect on the heat transfer coefficient, Nusselt number, temperature distribution and velocity field in comparison with pure water flow. One model for each property was tested to calculate the effective thermal conductivity, effective dynamic viscosity, and effective specific heat of the SWCNT/water mixture. The models were extracted from experimental data of a previous work. The outcomes indicate that the rheological behavior of SWCNT introduces a special effect on the SWCNT/water properties, which vary with SWCNT volume fraction. The results show an improvement in the heat transfer coefficient with increasing volume fraction of nanoparticles. The velocity of SWCNT/water nanofluid increased by adding SWCNT nanoparticles, and the maximum increase was registered at 0.05% SWCNT volume fraction. The mixture temperature is increased with the axial distance of the pipe but a reduction in temperature distribution is observed with the increasing SWCNT volume fraction, which reflects the effect of thermophysical properties of the mixture.

The paper is a thermodynamics analysis of the removal of any inert gas from the tank using the vapors of any liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose, a thermodynamic model was created which considers two boundary cases of this process. The first is a ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. Calculations make it possible to determine the amount of a gas used to complete the operation and its loss incurred as a result of total mixing of both gases.

The energetic efficiency of mixing is studied numerically in a continuous flow mixer constructed from a sequence of alternately twisted pipe bends. Counter-rotating vortices present in the curved channels and known as Dean vortices narrow the distribution of the residence time of fluid elements and accelerate the generation of a new material surface without obstructing the main flow and increasing the risk of fouling or flow stoppage. Cyclic twisting of the pipe curvature allows for quick reorientation of Dean vortices. The reorientation induces chaotic advection in a stable three-dimensional flow and speeds up mixing. The effect of computational domain discretisation for the low and medium Reynolds numbers (20 < Re < 2000º on the head loss, primary and secondary flow, residence time distribution, and the energetic efficiency of generation of the inter material surface is determined. The energetic efficiency is calculated in the time space, a standard approach in modelling reactive micromixing, and at the reactor exit. The maximum energetic efficiency is determined for Re ≈ 600 ÷ 700. It is also found that the initial orientation of the material surface to the pipe curvature has a significant impact on the energetic efficiency of mixing.

Helical coil heat exchangers are widely used in a variety of industry applications such as refrigeration systems, process plants and heat recovery. In this study, the effect of Reynolds number and the operating temperature on heat transfer coefficients and pressure drop for laminar flow conditions was investigated. Experiments were carried out in a shell and tube heat exchanger with a copper coiled pipe (4 mm ID, length of 1.7 m and coil pitch of 7.5 mm) in the temperature range from 243 to 273 K. Air – propan-2-ol vapor mixture and coolant (methylsilicone oil) flowed inside and around the coil, respectively. The fluid flow in the shell-side was kept constant, while in the coil it was varied from 6.6 to 26.6 m/s (the Reynolds number below the critical value of 7600). Results showed that the helical pipe provided higher heat transfer performance than a straight pipe with the same dimensions. The convective coefficients were determined using theWilson method. The values for the coiled pipe were in the range of 3–40 W/m2 ·K. They increased with increasing the gas flow rate and decreasing the coolant temperature.