A Convenient Method for the Accurate Calculation of Fin Efficiency of H-Type Fins Based on Linear Nomograms and Fitting Formulae

Fin efficiency, as a measure of the effectiveness of the heat transfer enhancement, is of great importance in studying the heat transfer performance of H-type finned tube banks. The fin efficiency of square fins is adopted by most researchers as an alternative to that of H-type fins, which can create certain errors in the fin efficiency of H-type fins. For this paper, the linear nomograms and fitting formulae of fin efficiency of H-type fins are obtained by the definition method of fin efficiency based on numerous numerical simulations, and the results calculated by this method are verified by experimental data. On this basis, the effects of three geometric parameters (slit width, fin height, and fin thickness) and two thermal parameters (surface heat transfer coefficient and fin thermal conductivity) on the fin efficiency of H-type fins are also investigated and compared to those of square fins. The results indicate that the fin efficiency of H-type fins increases with the increment of fin thickness and thermal conductivity, and decreases with the increase of slit width, fin height, and surface heat transfer coefficient. Accordingly, the linear nomograms and fitting formulae for the fin efficiency of H-type fins, which are well compatible with experimental data, can help to facilitate further theoretical research and engineering application.

Thermal performance of optimum exponential fin profiles subjected to a temperature jump

Purpose This paper aims to seek purely analytical results relying on the physical parameters including the temperature jump parameter. Design/methodology/approach The exponential fin profiles and heat transfer enhancement influenced by a temperature jump at the base are the main targets of this paper. Findings The introduced temperature slip at the base penetrates through the surface of the fin and reorganizes the distribution of temperature all over the surface. The overall impact of the temperature jump on the fin efficiency is such that it acts to lower the fin efficiency. However, the efficiency of the exponential fin is increasing for growing shape exponential fins as compared to the rectangular and decaying ones. Hence, exponential fins amenable to certain temperature jump has significance in technological cooling processes. Finally, the optimum dimensions regarding the base fin thickness and the fin length of the exponential profiles are assessed by means of optimizing the base heat transfer rate given a cross-sectional area. Originality/value Exact solutions are provided for optimum exponential type fins subjected to a temperature jump. The optimum dimensions regarding the base fin thickness and the fin length of the exponential profiles are assessed.

Heat Transfer Correlations for Star-Shaped Fins

Star-shaped fins are a newer type of fin for which correlations for heat transfer and pressure drop do not yet exist in the literature. Therefore, correlation equations for air-side heat transfer and pressure drop in a finned heat exchanger with star-shaped stainless-steel fins in staggered arrangement were developed in this work. To obtain these correlations, a numerical analysis of the basic heat exchanger geometry and another 21 variants of heat exchanger geometry was performed using computational fluid dynamics, and then the results of laboratory tests of a model of heat exchangers with star-shaped fins were used. In the numerical analysis, the fin pitch, the fin thickness, and the air velocity at the inlet to the heat exchanger were varied. The Nusselt (Nu) and Euler (Eu) numbers were determined for each variation analyzed. Initial correlations for Nu and Eu were derived using the least-squares deviation method. The correlation coefficients thus obtained were adjusted to agree with the results of the laboratory tests. The deviation of the final obtained correlation for Nu from the experimental test results was up to 10% in the range of Re < 3500, whereas for higher values of Re, the deviation was less than 2%. The Eu correlation deviated from experimental results up to 19% in the range of Re < 4000, whereas in the range of Re > 5600, the deviation was less than 1%. The correlations were valid in the range 2000 < Re < 16,000.

Multi-criteria optimization of a PCM based heat sink - Effect of geometric parameters on operational time and melt fraction

Computational fluid dynamic analysis of a PCM (Phase Change Material) based heat sink has been carried out in the present study. The PCM used is RT44HC. Longitudinal fins made of aluminum have been considered. The influence of pertinent parameters viz. fin number, fin thickness, orientation and base thickness on melt fraction and operational time have been analyzed. The critical temperature considered for the study is 54.8°C. The melting behavior of the PCM is simulated by employing the Volume of Fluid (VOF) method. The design of the experiment has been performed using the Taguchi method. By employing grey relational multi-criteria optimization technique and Multi-Objective Optimization on the basis of Ratio Analysis (MOORA) method the best thermally performing configuration has been attained through the optimum values of operational time and melt fraction. In addition to the above ANOVA (Analysis of Variance) is performed to find the most significant parameter. Based on the investigation fin thickness and number of fins are observed to significantly influence the thermal transport.

Thermal Performance of Double-Sided, Partial Height Strip Fin Arrays in a High Aspect Ratio, Rectangular Channel

Friction loss and heat transfer enhancement measurements were obtained for double-sided, partial height, strip fin arrays within a high aspect ratio (AR = 8), rectangular channel. Fins were arranged in a staggered array configuration with channel height to fin thickness ratio H/W = 9.6, spanwise spacing distance to fin thickness ratio S/W = 8.0, and streamwise spacing distance to fin length ratio X/L = 1.0. Shortened strip fins of equal length are positioned directly opposite of each other on the upper and lower channel surfaces with three gap size to channel height ratios considered G/H = 0.2, 0.3, and 0.4. The thermal performance of each fin configuration is determined from the measured pressure drop across the array and regionally averaged heat transfer coefficients at flow Reynolds numbers ranging from Re = 20,000–80,000. The partial height strip fin results are compared to baseline cases of strip fins spanning the full height of the channel and the smooth channel without roughness elements. Linear correlations of friction loss and power correlations of the heat transfer enhancement and thermal performance are provided as functions of flow Reynolds numbers for all cases. Strip fins spanning the full height of the channel provide the greatest heat transfer enhancement of all cases but introducing a gap size can significantly reduce friction losses. Full height strip fins provide the greatest thermal performance for Reynolds numbers ranging from Re = 20,000–30,000, and partial height strip fins with the gap size of G/H = 0.3 provide the greatest thermal performance for flow Reynolds numbers ranging from Re = 40,000–80,000.

Flight Stability Analysis of a Flexible Rocket Using Finite Elements and Reduced-Order Modeling

The coupling of advanced structural and aerodynamic methods is a complex and computationally demanding task. In many cases, simplifications must be made. For the flight simulation of flexible aerospace vehicles, it is common to reduce the overall structure down to a series of linked degenerate structures such as Euler-Bernoulli beams in order to expedite the structural portion of the solution process. The current study employs the sophistication and generality of finite-element based modeling with the concepts of reduced-order modeling to create a general flexible-body flight simulation program. The program was created for use with the MATLAB-Simulink programming package. A parametric analysis on the stability of flexible rockets is performed and results are presented for a variety of rocket configurations based on the SPHADS-1 vehicle under development at Ryerson University. The primary instability mode under study is that associated with the flapping and twisting motions of the tailfins under aerodynamic loading. By varying the average fin thickness, both stable and unstable behaviour is recorded for a variety of flight conditions.

Flight Stability Analysis of a Flexible Rocket Using Finite Elements and Reduced-Order Modeling

The coupling of advanced structural and aerodynamic methods is a complex and computationally demanding task. In many cases, simplifications must be made. For the flight simulation of flexible aerospace vehicles, it is common to reduce the overall structure down to a series of linked degenerate structures such as Euler-Bernoulli beams in order to expedite the structural portion of the solution process. The current study employs the sophistication and generality of finite-element based modeling with the concepts of reduced-order modeling to create a general flexible-body flight simulation program. The program was created for use with the MATLAB-Simulink programming package. A parametric analysis on the stability of flexible rockets is performed and results are presented for a variety of rocket configurations based on the SPHADS-1 vehicle under development at Ryerson University. The primary instability mode under study is that associated with the flapping and twisting motions of the tailfins under aerodynamic loading. By varying the average fin thickness, both stable and unstable behaviour is recorded for a variety of flight conditions.

Performance Investigation of The Bed Adsorption of An Adsorption Desalination Using CFD Simulation

One of the critical elements of an adsorption desalination system is the adsorption bed. System dynamics of a 2-bed single-stage silica gel plus water-based AD system was analyzed. A great pattern is expanded using energy conservation and mass connected with the kinetics of the ad- sorption/desorption process. Computational fluid dynamics (CFD) modeling was handled for simulation of the adsorption process for a rectangular finned tube-based adsorption bed featured with silica gel adsorbent substance. For the simulation, the adsorbents were considered as a solid volume with defined porosity based on Darcy equation. The adsorption and desorption mode of the adsorption bed was simulated. The CFD techniques were then applied to study fin thickness and fin height. The results showed that decreasing the fin thickness increased the water uptake by up to 8% and decreased the fin height from 30mm to 20mm, which resulted in an increase of the water uptake up to 17%. The CFD technique was also used to investigate the effect of plate type on the adsorption bed performance. The results showed that the copper plate improved the water uptake up to 9%. The copper plate decreased the temperature of the adsorption bed up to 11% more than the aluminum plate.

Flow-Induced Acoustic Resonance of Finned Cylinders With Varying Fin Heights

The flow-excited acoustic resonance phenomenon, which is instigated by periodic flow perturbation, leads to the generation of acute sound pressure. In this work, we investigated the characteristics of the flow-excited acoustic resonance for circular finned cylinders with different fin heights. The fin height is expressed as a normalized form considering the ratio of the fin diameter to the root cylinder diameter. The experiments are performed with finned cylinders having a range of diameter ratios between 1.5&lt;Df/Dr&lt;2.5. The diameter ratios are varied by changing the root diameter and fin diameter separately as well as simultaneously while keeping the fin pitch and the fin thickness constant. The results show that the excitation of acoustic resonance has profound dependence on the diameter ratio. Increasing the diameter ratios of the finned cylinder results in strong acoustic resonance excitation. The lock-in width and the onset of the acoustic resonance excitation also depend on the diameter ratio of the cylinders. Moreover, the results show that using an effective diameter based on the geometrical flow blockage does not take into account the changes occurring in the source of resonance excitation due to the addition of fins.