A numerical investigation of the heat transfer characteristics of water-based mango bark nanofluid flowing in a double-pipe heat exchanger

Investigation on reconstruction of internal heat source in biological tissue based on multi-island genetic algorithm

With the rapid development of engineering thermophysics, researches on human biological heat transfer phenomena has gradually shifted from qualitative to quantitative. It is a typical inverse problem of heat conduction that deriving the distribution of internal heat sources from the temperature distribution on the body surface. Differing from traditional numerical methods for solving heat conduction, this paper transforms such an inverse problem of bio-heat transfer into a direct one, thereby avoiding complex boundary conditions and regularization processes. To noninvasively reconstruct the internal heat source and its corresponding 3D temperature field in biological tissue, the multi-island genetic algorithm (MIGA) is used in the simulation module, where the position P(x, y, z) of point heat source in biological tissue and its corresponding temperature T are set as the optimization variables. Under a certain optimized sample, one can obtain the simulated temperature distributing on the surface of the module, then subtract the simulated temperature from the measured temperature of the same surface which was measured using a thermal infrared imager. If the absolute value of the difference is smaller, it indicates that the current sample is closer to the true location and temperature of the heat source. When the values of optimization variables are determined, the corresponding 3D temperature field is also confirmed. The simulation results show the experimental and simulation temperature values of 15.5Ω resistor are 60.75°C and 62.15 °C respectively, with the error of 2.31 %, and those of 30.5Ω resistor are 84.40 °C and 86.33°C respectively, with the error of 2.29 %. The simulated positions are very approximate with those of the real experimental module. The method presented in this paper has enormous potential and promising prospects in clinical research and application, such as tumor hyperthermia, disease thermal diagnosis technology, etc.

Numerical study of heat transfer, pressure drop and entropy production characteristics in inclined heat exchangers with uniform heat flux using mango bark/CO2 nanofluid

For sustainable low-carbon cities, using sustainable urban energy system solutions is imperative. CO2-based bionanofluid is one proposed energy system solution that is sustainable and environmentally friendly. This paper examines the thermal-hydraulic and entropy production properties of mango bark/CO2 nanofluid for industrial-inclined gas cooling applications. The influence of gravitational force (in terms of tube inclination angle), volume fraction, and Reynolds number on the heat transfer, pressure drop, and entropy production of CO2-based mango bark nanofluids in laminar flow through a circular aluminum tube are numerically studied. The bionanofluid flows through a tube with an inner radius of 2.25 mm, a length of 970.0 mm, and an initial temperature of 320.0 K. A constant heat flux of -10.0 W/m2 is applied to the flow at its walls. The laminar flow regime with Reynolds numbers of 100, 400, 700, and 1000 are subjected to flow inclinations of ±90°, ±60°, ±45°, ±30°, and 0° and bionanofluid volume fractions of 0.5%, 1.0%, and 2.0%. Results show that ±45° tube inclination angle offers the optimal heat transfer coefficient, maximum pressure drop, and minimum total entropy production rates for Re > 100; however, for Re = 100, these occur at the inclination angle of -30° and +60°. The pressure drop shows less sensitivity to the inclination angle; however, it offers peak values at the same inclination angles as the heat transfer coefficient for the respective Reynolds number values. The maximum thermal enhancements due to gravitational effect are 42%, 93.98%, 121.28%, and 150% for Reynolds numbers of 100, 400, 700, and 1000, respectively, while that due to nanofluid volume fraction are less than 16%.

Enhancing Heat Transfer Inside a Double Pipe Heat Exchanger Using Al2O3 Nanofluid, Experimental Investigation Under Turbulent Flow Conditions

The aim of the present research is to enhance the convective heat transfer coefficient inside the tube of the double pipe under turbulent flow conditions, this is carried out by mixing the water with aluminium oxide (Al2O3) nanoparticles. In this study, the effects of Al2O3 nanofluid with different volume concentrations of 0.05% to 0.4%, mass flow rates of nanofluid inside the tube, mass flow rates of the water flow through the annulus, and inlet temperature inside the tube on the Nusselt number were investigated. The analysis of experiential results revealed that use Al2O3 nanofluids leads to a significant enhancement of the convective heat transfer coefficient. The convective heat transfer coefficients reached maximum values at 0.1% of the volume concentrations of Al2O3 nanoparticles and then decreased as the increase of the volume concentrations from 0.1 to 0.4%. The Nusselt number increases as the Reynolds numbers of both the flows inside the tube and through the annulus increase. The fiction factor increases as the volume concentrations of nanoparticles increases. Empirical correlations are presented describing the Nusslet number and friction factor of the Al2O3 nanofluid flow through the tube of the double pipe heat exchangers, and concealing the affecting parameters in such process.

Numerical study of the effects of geometric parameters and nanofluid properties on heat transfer and pressure drop in helical tubes

In this research the geometric parameters and nanofluid properties effects on heat transfer and pressure drop in helical tube, by using alumina-water nanofluid as cooling fluid, are numerically investigated. Friction factor and heat transfer coefficient are calculated by considering the effects of nanofluid properties, including nanoparticle diameter, nanofluid temperature, Reynolds number, and volume fraction, on the one hand, and the impact of geometric parameters, including tube diameter, coils diameter and coils pitch, on the other hand. Numerical analysis is performed in the Ansys Fluent 19.2 software using the SST k-ω turbulence model. By increasing the nanofluid volume fraction the heat transfer coefficient and pressure drop in helical coils increase, the same as the nanoparticle diameter reduction. The reduction of nanoparticle diameter causes an enhancement of heat transfer and friction factor, the best results happen in dp = 5 nm and φ = 4%, where the it was ~ 40.64% more efficient than base fluid. This amounts for φ = 3%, φ = 2% and φ = 1% are 31.80%, 18.02% and 8.83%, respectively. Finally, the performance evaluation criteria (PEC) is compared for different cases, the maximum value was happen on φ = 4% and dp = 5 nm, which it is 1.86 times higher than the base fluid. The results indicate that the thermal efficiency of the heat exchanger improve largely by using helical coils and nanofluids, rather than the base fluid, and direct tubes. In addition, increasing coil pitch and curvature ratio enhance heat transfer and reduce friction factor.