Natural Convection Effect on Solidification Enhancement in a Multi-Tube Latent Heat Storage System: Effect of Tubes’ Arrangement

The solidification process in a multi-tube latent heat energy system is affected by the natural convection and the arrangement of heat exchanger tubes, which changes the buoyancy effect as well. In the current work, the effect of the arrangement of the tubes in a multi-tube heat exchanger was examined during the solidification process with the focus on the natural convection effects inside the phase change material (PCM). The behavior of the system was numerically analyzed using liquid fraction and energy released, as well as temperature, velocity and streamline profiles for different studied cases. The arrangement of the tubes, considering seven pipes in the symmetrical condition, are assumed at different positions in the system, including uniform distribution of the tubes as well as non-uniform distribution, i.e., tubes concentrated at the bottom, middle and the top of the PCM shell. The model was first validated compared with previous experimental work from the literature. The results show that the heat rate removal from the PCM after 16 h was 52.89 W (max) and 14.85 W (min) for the cases of uniform tube distribution and tubes concentrated at the bottom, respectively, for the proposed dimensions of the heat exchanger. The heat rate removal of the system with uniform tube distribution increases when the distance between the tubes and top of the shell reduces, and increased equal to 68.75 W due to natural convection effect. The heat release rate also reduces by increasing the temperature the tubes. The heat removal rate increases by 7.5%, and 23.7% when the temperature increases from 10 °C to 15 °C and 20 °C, respectively. This paper reveals that specific consideration to the arrangement of the tubes should be made to enhance the heat recovery process attending natural convection effects in phase change heat storage systems.

Blood Flow with Multiple Stenoses in a Force Field

In the present manuscript, a mathematical model of steady and incompressible Casson fluid in a non-uniform tube having many stenoses in the presence of a force field is analyzed. Using mild stenosis approximation and appropriate boundary conditions, analytical expressions for velocity, pressure drop, impedance, and wall share stress have been computed due to their importance in the rheology of blood. The Casson fluid is used to depict the behavior of blood flow. The effects of different physical constraints on resistance to the flow and wall shear stress of the fluid are examined. The study ascertains that resistance to the flow and wall shear stress is maximum at duck of stenosis. It is also explored that an increase in the size of the stenosis in the artery affects the normal flow of the blood through vessels in the heart, body, and brain and this may lead to major cardiac disease problems like stroke, heart attack, etc.

Heat and mass transfer effects of peristaltic motion of a Jeffery fluid in a tube

The impact of heat and mass transfer were analyzed in the present investigation by considering the peristaltic transport of a Jeffery fluid with nanoparticles in a uniform tube. Lubrication theory hypotheses have been considered and expressions have been defined for axial velocity, pressure drop, frictional force, heat and mass transfer effects. The patterns of the stream line and trapped bolus were graphically depicted at the end. It is found that with regard to the modification of various parameters, pressure drop and frictional force exhibit identical behavior. By increasing/decreasing the local temperature Grashof number, Brownian motion parameter and local nanoparticle Grashof number, pressure drop and axial velocity can be regulated.

Pinguicula rosmarieae Casper, Bussmann & T.Henning (Lentibulariaceae), a new butterwort from the Amotape-Huancabamba Zone (northern Peru)

The insectivorous genus Pinguicula occurs along the whole Andean mountain chain from Colombia-Venezuela in the north to Tierra del Fuego in the south with a short interruption in the Peruvian-Chilean desert range. This paper describes a new and striking species of Pinguicula that occurs in the south-eastern part of the Amotape-Huancabamba Zone in north Peru. It grows either as a lithophyte on moist rocks or as an epiphyte on Polylepis multijuga Pilg. in the wet highlands of the Cordillera Central. Pinguicula rosmarieae Casper, Bussmann & T.Henning, sp. nov. is clearly distinguished by a basal rosette of ovate-obovate leaves spread out flat on the ground and especially by a two-partite corolla with a straight uniform tube-spur complex, two features unknown from other Andean Pinguicula species. The morphological similarity to P. calyptrata Kunth is discussed and the habitat and distribution of P. rosmarieae are characterised.

Study of Al2O3/copper–water nanoparticle shape, slip effects, and heat transfer on steady physiological delivery of MHD hybrid nanofluid

This paper contains the analytical investigation of magnetohydrodynamic (MHD) flow of copper/Al2O3–water hybrid nanofluid with unstable peristaltic motion. Three different geometries (bricks, cylinder, and platelets) along with velocity and thermal slip conditions are studied in detail to reach the precise solution. Flow geometry of a non-uniform tube of finite length, experimental values of base fluid, and considered nanoparticles are taken into account to examine the theoretical investigation of formulated equations. Dimensionless control equations, which are subject to physically realistic boundary conditions, are closely studied to obtain precise results. The shape effects of nanoparticles on velocity, temperature distribution, and heat transfer on the length of the non-uniform tube with variation of the various flow parameters are discussed in a graphical description to understand the theoretical aspects to validate the medical analysis. The observations from the analysis state that copper/Al2O3–water carry maximum velocity for smaller values of slip parameter. Temperature distributions for heat absorption parameter are more significant as fluid flow accelerates when large values are chosen. Large values of thermal slip parameter yield enhancement in pressure gradient and Cu–water nanofluid has higher impact than hybrid nanofluid. Platelet-shaped nanoparticles of hybrid nanofluid have more significant effect on pressure gradient than cylinder- and brick-shaped nanoparticles of Cu–water nanofluid. An intrinsic property of peristaltic transport (i.e., trapping) is also discussed. The trapped bolus decreases for platelets and cylinder-shaped nanoparticles, whereas, the size of the trapped bolus increases for brick-shaped nanoparticles. This model is applicable to a drug delivery system and to design the micro-peristaltic pump for transporting nanofluids.

CONVECTION HEAT TRANSFER PERFORMANCE OF THE FRACTAL TUBE BANK UNDER CROSS FLOW

Convective heat transfer process between fractal tube bank and coolant water was simulated by using the finite element method. Both rectangular and circular tube banks were investigated in detail. For the relationship between Nusselt number and Reynolds number, the fractal circular tube bank shows the same trend as the rectangular tube one. Based on simulation results, the empirical heat transfer correlations for different stage fractals were regressed. The exponents of correlations increase with the fractal stage. Almost linear correlations between Nu and Re for fourth stage fractal were obtained, indicating a good heat transfer enhancement with the increase in fractal stages. Compared to the uniform tube bank, the fractal tube banks show better overall performance in enhanced heat transfer effect. This research would be helpful to understand the heat exchange mechanism of the multi-scale structure.