This paper presents the effect of number of tubes, unequal baffle spacing and tube diameter on heat transfer and pressure drop characteristics of a typical shell and tube type heat exchanger. Upon geometrical optimization, the second phase of this research work aims at studying the influence of Al2O3 nanofluid of 0.5%, 0.75%, 1%, 1.25% and 1.5% concentrations by admitting water along the tubes and Al2O3 nanofluid along the shell side. The shell and tube heat exchangers of various geometrical configurations are modeled using SOLIDWORKS 2015. The heat transfer and fluid flow characteristics through the heat exchanger are obtained by solving the governing equations namely continuity, momentum and energy equations using ANSYS CFX 15 CFD code. Temperature, pressure contours and velocity streamlines along the mid-plane of the shell and tube heat exchanger are obtained for various geometrical configurations and for different volume concentration of nanofluid. The heat transfer coefficient and the pressure drop for various volume fraction concentrations of the nanofluid are plotted. The use of nanofluid resulted in increase of both the pressure drop and heat transfer coefficient. The heat transfer coefficient at 1.25% volume concentration of nanofluid is found to be the optimum value.

A one-dimensional mathematical model is developed to analyze the unsteady characteristics of arbitrary damped free motion, denoted as Z(τ), in a rigid, constant-diameter vertical column of a U-tube filled with an incompressible Newtonian liquid, where τ represents time. This model utilizes a simplified unsteady momentum equation derived from the Navier–Stokes equations in a circular coordinate system. Moreover, it incorporates assumptions about the periodicity of arbitrary damped free oscillations and employs the Fourier series representation to characterize the damped free motion. The combination of assumptions made for periodicity, the simplified momentum equation, and the Fourier series representation makes the current mathematical model unique and novel compared to prevailing models in the literature. In this model, the governing partial differential equation contains two dependent variables: Z(τ) is the known variable, as one can measure from experiments, and the instantaneous velocity uz is the unknown variable. Fitting the experimental data into the Fourier series provides the Fourier coefficients associated with the specific experiment. The Laplace transform method is used to determine the analytical solution for uz corresponding to the known Z(τ). The analytical expressions for instantaneous flow characteristics of practical importance, including area-averaged velocity, wall shear stress, and acceleration/deceleration, are deduced from uz. The analytical solutions presented are valid for generalized unsteady motions, including underdamped oscillations with varying amplitudes and periods, underdamped oscillations with varying amplitudes and constant period, and overdamped motion that does not exhibit a single oscillation. The findings from the present model offer insights for formulating a new friction model.

The effect of outlet thickness and outlet angle of the bladeless fan have been an alysed numerically on the aerodynamic performance of the bladeless fan. Five different aerofoil profiles have been considered for the present work is Eppler 479, Eppler169, Eppler 473, S1046 and S1048. The bladeless fan arrangement has been achieved by converting the aerodynamic models listed above. The ANSYS ICEM CFD 16.0 have been used to discretize the enclosure and bladeless fan through finite volume approach. The mesh model is then imported into ANSYS CFX 16.0 pre-processor for applying the required boundary conditions. The governing equations namely continuity and momentum are used to solve the flow physics through and across the bladeless fan and SST k-? turbulence model has been used to predict the turbulence in the bladeless fan. The effect of outlet thicknesses and outlet angles have been varied for all the five aerofoil configurations mentioned and the volumetric flow at inlet have been adjusted from 5 LPS to 80 LPS. Outlet thickness is varied from 0.8, 1.0, 1.3, 1.5 and 2 mm and the slit angle is varied from 20 degrees to 80 degrees in step of 10 degrees. The results predicted that Eppler 473 aerofoil profile showed better performance when the thickness of slit and outlet angle has been fixed constant as 1 mm and 70 degree respectively. Also, the maximum discharge flow ratio is recorded for an inlet volumetric flow rate of 80 LPS and it is found to be 34.37. The present numerical study substantiated that outlet thickness plays a dominant role on the bladeless fan’s aerodynamic performance compared to outlet angle and aerodynamic shape considered in this numerical analysis. The contours of velocity, streamline and pressure of the bladeless fan have been discussed.