Step Fin Research Articles

Natural convective solar dryer powered by stepped fin plate integrated trough array solar air heater for agricultural produce preservations

In this work, heat energy analysis and economic feasibility of natural convection mixed mode solar dryer under three different methods viz., normal flat plate collector solar dryer (NFPSD), step fin plate integrated trough array collector solar dryer (SFPTSD) and SFPTSD with latent heat storage (LHS) are experimentally investigated. The drying time in SFPTSD – LHS (setup 3) to reach its safe moisture content for paddy, wheat, green chilli are 5.5 h, 6 h and 7 h respectively and it is significantly lowered to a maximum of 47 % as compared with NFPSD (setup 1). Also, the average maximum heat efficiency of 62.19 % for collector and 38.32 % for drying cabinet is obtained in setup 3. The specific heat energy consumption is lowered by 20.65 % and specific moisture extraction rate increases to 21.73 % for this proposed setup in comparison with setup 1. The improvement potential is reduced to a substantial margin of 136.5 W and yields an exergetic efficiency increase of 12.38 % than setup 1. An average annual saving increase of 193.08$ with its present value 94.33$ is achieved for setup 3 as compared with setup 1. We recommend this setup can dry edible produce at low cost and affordable to economically weak farming communities.

Investigation of Step Fin (SF), Step Drain (SD) and Step Source (SS) FinFETs with Trap Effect

In this paper, the RF and analog performances of the triple material gate (TMG) step Fin (SF) FinFET, step drain (SD) FinFET, and step source (SS) FinFET have been explored by 3D TCAD simulation. We have simulated the performance in the presence of uniform trap (UT) and Gaussian trap (GT) distribution with a fixed value of trap concentration (1012 eV−2cm−2). The various DC parameters, such as threshold voltage (Vth), sub-threshold swing (SS), and switching ratio, are observed in trap distribution. The outcome of this simulation study is that the SF FinFET structure has shown 25.1% and 33.95% enhancement of drive current compared to SD FinFET and SS FinFET, respectively. On the other hand, SS FinFET has shown an enhancement of 1.2x(9.8x) on gain transconductance frequency product (GTFP), 1.21x(1.01x) of transconductance frequency product (TFP), 4.19x(23.28x) of intrinsic gain (Av), 1.88x(21.21x) of gain frequency product (GFP), and 4.18x(9.69x) of the gain-bandwidth product (GBP) compared to SD FinFET (SF FinFET).

Effect of various fin geometries on heat dissipation of traction motors used in Electric vehicles

The traction motor is one of the major component in an electric vehicle subjected to high temperature variations and thermal stresses. In order to cool the motor, fins are proposed on the housing. Present study investigates effect of various fin geometries such as rectangular fin, rectangular fin with a rectangular protrusion, tapered pin fin integrated with rectangular fin, step fin and wavy fin on heat dissipation of an electric motor by developing numerical model and the comparative study is presented. 3D geometrical model of the motor housing is developed using CATIA V5 and analyzed using ANSYS Workbench 2019 R3. Steady-state temperature distribution in the housing cross section is obtained. The obtained results were found in satisfactory quantitative agreement with the published literature results and deviated not more than 7 percent. Research confirmed that rectangular fin with rectangular protrusions gives the greatest heat transfer comparatively and it is concluded that the life of an electric motor increases as there is decrease in temperature of the motor.

Geometric Size Optimization of Annular Step Fin Using Multi-Objective Genetic Algorithm

Although an annular stepped fin can produce better cooling effect in comparison to an annular disk fin, it is yet to be studied in detail. In the present work, one-dimensional heat transfer in a two-stepped rectangular cross-sectional annular fin with constant base temperature and variable thermal conductivity is modeled as a multi-objective optimization problem. Taking cross-sectional half-thicknesses and outer radii of the two fin steps as design variables, an attempt is made to obtain the efficient fin geometry primarily by simultaneously maximizing the heat transfer rate and minimizing the fin volume. For further assessment of the fin performance, three more objective functions are studied, which are minimization of the fin surface area and maximization of the fin efficiency and effectiveness. Evaluating the heat transfer rate through the hybrid spline difference method, the well-known multi-objective genetic algorithm, namely, nondominated sorting genetic algorithm II (NSGA-II), is employed for approximating the Pareto-optimal front containing a set of tradeoff solutions in terms of different combinations of the considered five objective functions. The Pareto-optimal sensitivity is also analyzed for studying the influences of the design variables on the objective functions. As an outcome, it can be concluded that the proposed procedure would give an open choice to designers to lead to a practical stepped fin configuration.

A proper analytical analysis of annular step porous fins for determining maximum heat transfer

The annular stepped fin is a common choice for enhancing heat transfer from a cylindrical primary surface. This typical fin shape is easy in manufacturing compared to the taper shape. There is still effort required to increase the heat transfer rate per unit mass of a step fin. With this design point of view, the present study has been carried out. There may be two design aspects to be adopted to satisfy the above design requirement. With consideration of the porous material and moving condition of fins, heat transfer can be increased for a constraint mass of a fin. In the present study, an appropriate analytical method has been developed for an annular step fin of porous material under a moving condition. The effect of internal heat generation in the fin and the radiation mode of heat transfer on the fin performance have been studied elaborately. Unlike previous literature for moving fins, the performance design parameter is dependent on the modified Peclet number instead of the conventional Peclet number. The double differential transform method has been used for the analytical analysis. The optimization analysis has been demonstrated for the maximization of heat transfer through an annular step porous fin (ASPF) under a design constraint of mass of a fin. A comparative study has also been made between the porous and solid fins for an equal mass of fins. It was highlighted that the porous fin transfer always more heat at an optimum condition compared to the solid fin which is a profitable design aspect for selecting the porous condition. The moving condition is also a better approach to increase heat transfer rate and it is clearly demonstrated in the present study. The formulation of the present work is suitable for stationary and annular disk porous fins also by considering an appropriate design variable.

A novel trapezoid fin pattern applicable for air-cooled heat sink

The present study proposed a novel step or trapezoid surface design applicable to air-cooled heat sink under cross flow condition. A total of five heat sinks were made and tested, and the corresponding fin patterns are (a) plate fin; (b) step fin (step 1/3, 3 steps); (c) 2-step fin (step 1/2, 2 steps); (d) trapezoid fin (trap 1/3, cutting 1/3 length from the rear end) and (e) trapezoid fin (trap 1/2, cutting 1/2 length from the rear end). The design is based on the heat transfer augmentation via (1) longer perimeter of entrance region and (2) larger effective temperature difference at the rear part of the heat sink. From the test results, it is found that either step or trapezoid design can provide a higher heat transfer conductance and a lower pressure drop at a specified frontal velocity. The effective conductance of trap 1/3 design exceeds that of plate surface by approximately 38 % at a frontal velocity of 5 m s−1 while retains a lower pressure drop of 20 % with its surface area being reduced by 20.6 %. For comparisons exploiting the overall thermal resistance versus pumping power, the resultant thermal resistance of the proposed trapezoid design 1/3, still reveals a 10 % lower thermal resistance than the plate fin surface at a specified pumping power.

An ease of analysis for optimum design of an annular step fin

In the present study, exact and approximate analytical techniques are developed to determine the optimum design of a rectangular stepped annular fin with constant base temperature. An algebraic expression based on the mean value theorem is used as the vehicle for an approximation tool. The corresponding temperature distribution and heat transfer characteristics in the fin are determined using exponential functions. The standard modified Bessel function formulation is employed for the exact analysis. Error analysis has been carried out to compare between the exact and approximate results. It is found that the integral approach of calculating the rate of heat transfer is more accurate than the differential approach while applying the approximate analytic technique. The errors associated with the approximate analytic methods falls well within acceptable accuracy levels for engineering analysis and design.

Some modifications on the text of our paper: Two dominant analytical methods for thermal analysis of convective step fin with variable thermal conductivity, Thermal science, vol. 18, 2014, no. 2, pp. 431-442

As the original manuscript had some similar sentences with some of our previous publications, we have decided to modify the main text of the manuscript in the PDF version. The modifications have been applied within the PDF online version. This printed version is provided for ones who have access to the printable version of the journal and to avoid any confusion. It should be noted that the results and mathematical procedure of the original version are completely correct and this note has nothing to do with the formulations of the main paper.

Optimization of space radiators with step fins

The optimal design of the fin geometry of a heat pipe/fin radiator having fins with a step change in thickness, namely step fin (SF), has been performed in the present article. The optimization algorithm determines the thickness parameter describing the variation of fin thickness, intermediate fin length where the step change in thickness occurs, and the root thickness of the fins in order to provide the maximum heat radiated per element mass given the linear density of the heat pipe, the thermal conductivity and density of the fin material, the emissivity of the surface, and the operating temperature. The objective function is evaluated as the solution to a radiation thermal analysis problem performed using the Adomian decomposition method, which provides an analytical solution in the form of an infinite power series. The results of the new optimal design have been compared to heat pipe/fin radiators with flat fins (FFs). The results demonstrated that the maximum heat transfer rate per unit mass for a radiator with SF is always higher than that of a radiator with FF for the identical design condition.

Performance of a Convectively Heated Rectangular Fin With a Step Change in Cross-Sectional Area and Losing Heat by Simultaneous Convection and Radiation (Step Fins Under Radiation Environment)

A numerical procedure has been used to study the thermal performance of a step convective-radiative fin with temperature dependent thermal conductivity and convective base heating. An analytical solution has been developed for a pure convective fin with constant thermal conductivity, with its base exposed to a hot fluid. The effects of geometrical and thermophysical parameters on the temperature profiles in the fin, the fin efficiency, and the fin effectiveness are illustrated. The step fin is found to deliver a superior thermal performance compared with the uniformly thick fin.

Analysis of thermal performance and optimization of concentric circular fins under dehumidifying conditions

The analysis of wet fins was carried out by many investigators with the variation of a linear relationship between specific humidity and the corresponding saturation temperature of air adjacent to the fin surface. For determination of the fin surface temperature under this scheme, fin-tip temperature is essentially known a priori which can be employed to calculate the psychrometric parameters associated with the dehumidification process. On the other hand, the tip temperature is only known after the salving the governing equation and it is also a function of the psychrometric properties of air. Thus for the simplicity, dew point temperature is considered as the tip temperature for calculating only the psychrometric parameters of fully wet fins in a recent publication. Nevertheless, in the actual situation this dew point temperature never satisfies at the tip and therefore psychrometric parameters calculated with the assumption of the dew point temperature at the tip may be incorrect. In the present work, an iterative scheme is demonstrated for determination of the actual tip temperature and local fin surface temperature. With considering this aspect, thermal analysis of a new geometric fin, namely, annular step fin (ASF) is proposed for the more effective utilization of fin material in comparison with the annular disc fin. An optimization study has also been made by using the modified thermal analysis of fully wet fins and the analysis of partially wet fins, separately. A remarkable change in results has been noticed when they are compared with that of the published result. Finally, it is worthy to mention that the maximum heat transfer rate per unit volume for an ASF is always higher than that of the annular disc fin for the identical design condition.

Mode theory of multilayer waveguide structure with discontinuities

TEn mode (whose electric field is zero in the normal direction of the boundaries between layers) and TMn mode (whose magnetic field is zero in the normal direction of the boundaries between layers) are defined. Then conditions under which pure TEn (TMn) modes may exist in multilayer waveguide structure with discontinuities are presented. E (H) step wavguides, ridged wavguides, microstrip lines and fin lines all satisfy the conditions, and hold for TEn (TMn) mode. The conventional conclusion that ridged waveguides with inhomogeneous dielectric-slab loading, microstrip lines and fin lines only hold for hybrid modes is revised. Compared with hybrid modes, the number of unknown variations and matching equations is reduced by half for pure TEn (TMn) modes, and the computation cost is decreased dramatically.

COMMAND GUIDANCE SYSTEMS SIMULATION : AIRFRAME ANALYSIS

A complete six-degrees of freedom flight simulation model for anti-aircraft command guided missile system is developed. A computer code that solves the model is constructed with BORLANDC. Modular concept is considered in the code development. The non-linear differential equations that describe the model are solved by Runge-kutta 4 method. The integration step is chosen small enough that the numerical errors are negligible. The aerodynamic non-linear coefficients that describe the missile airframe are calculated by the aid of standard NASA curves. The missile is roll angle stabilized throughout the flight. It is controlled in the lateral planes via two pairs of rear control fins. The pitch and yaw control channels are identical except for constant gravity bias added to the pitch channel. The missile airframe is deeply investigated. The step response of the airframe to unit step fin deflection is obtained. The results indicate that the airframe can be accurately represented by a second order lag system. The weathercock natural frequency and the damping coefficient are obtained by transforming the time-domain data to the frequency domain by the Fast Fourier Transform. The obtained results show that the missile airframe is heavily underdamped. As well, the airframe bandwidth increases by increasing the missile speed. Doubling the missile speed fairly doubles the weathercock frequency at the expense of aerodynamic damping coefficient reduction.