Effects Of Fin Height Research Articles

Effects of Fin Height, Fin Thickness and Reynolds Number on Heat Transfer Enhancement of Flat-Plate Thermal Collector: A Numerical Analysis

A flat-plate thermal collector combined with a PV panel also called a PV/T collector is a device that converts solar irradiation into thermal energy and electrical energy simultaneously. The unused thermal energy of the PV/T collector is absorbed by the flat-plate thermal collector. This may then contribute directly to an enhancement of the electrical efficiency of the PV/T collector. In the present study, the effect of geometry and Reynolds Number on the thermal performance of flat-plate thermal collectors is numerically investigated. Thereafter, CFD simulation is then implemented to characterize the thermal performance in terms of absorber temperature and convection heat transfer coefficient. To disturb the fluid flow pattern in this work the 45o inclined fins are attached underneath the surface of the collector model and they act as an absorber. Monthly average weather data of inlet fluid temperature and ambient temperature as well as solar irradiation level implemented in this study were obtained from the Meteorological, Climatological and Geophysical Agency of Bandarlampung regency. Several different cases have been considered by varying the fin height from 20 to 80 mm, fin thickness from 1 to 4 mm, and Reynolds number from 1500 to 6000. The results show that increasing the fin geometry (the fin thickness and fin height) and Reynolds Number reduce the flat-plate surface temperature due to the more conductive and convective heat transfer process. However, in terms of the convective heat transfer coefficient parameter, the Reynolds Number implemented has a dominant effect compared to the fin geometry. Moreover, by increasing Reynolds Number by four times, there is a decrease in the mean surface temperature by 26% and an increase in the mean convective heat transfer coefficient of 146% compared to the initial conditions

Effect of fin density and fin height on flow-induced vibration behavior of finned tube arrays subjected to water cross flow

PurposeThe prediction of critical velocity at instability threshold for shell and tube heat exchangers is important to avoid failure of tubes as a result of flow-induced vibrations due to water cross flow. The flow-induced vibration in finned tube heat exchangers is affected by various parameters such as fin height, fin pitch, fin material, tube array, pitch ratio, fin type, fluid velocity etc. In this paper, an experimental investigation of fluid elastic instability in shell and tube heat exchangers is carried out by subjecting normal square finned tube arrays of pitch ratio 1.79 to water cross flow.Design/methodology/approachThe five tube arrays, namely plain array, two finned tube arrays with 3 fpi and 9 fpi fin density, and two finned tube arrays with 3 mm and 6 mm fin height are tested in the experimental test setup with water flow loop and vibration measurement system. The research objective is to evaluate the effect of fin density and fin height on the instability threshold. The critical velocity at instability threshold is determined to characterize the fluid elastic instability behavior of different tube arrays. The vortex shedding behavior of the tube arrays is also studied by determining Strouhal number corresponding to the small peaks before fluid elastic instability.FindingsThe fluid elastic instability behavior of the tube arrays was found to be the function of fin tube parameters. The experimental results indicate that an increase in fin density and fin height results in delaying the instability threshold for finned tube arrays. It is also observed that critical velocity at instability is increased for finned tube arrays compared to plain tube arrays of the same pitch ratio. The design modifications in the outer box have resulted in further reduction in the natural frequency. This enabled to reach clear instability for all the five-tube arrays.Originality/valueThe research data add the value to the present body of knowledge by knowing the effect of fin height and fin density on the fluid elastic instability threshold of normal square finned tube arrays subjected to water cross flow.

The effect of fin height on forced convection heat transfer from rectangular fin array

In this research, experimental investigation of the coefficient of the heat transfer has been conducted for a set of rectangular fins with different fin height, 0.27, 0.47 and 0.67 m at air velocity test points of 1.1, 1.3, 1.5, 1.7 and 2 m/s, to meet the Reynolds number (Re). Thirty samples from the two cases with changing fin positions were studied to verify the thermal performance of the system. The study was conducted based on the cross-sectional diameter of 21167, 25016, 28864, 32713, and 38486. Total heat flux in all tubes has been settled as 26.3, 58, and 88.7 W/m 2 . The experimental results showed that the temperature difference between the surface of the block and flowing air increases with increasing Reynolds number for all heat flow states.

Performance Comparison of Mini-Rectangular Fin Heat Sinks Using Different Coolants: Supercritical CO2, Water and Al2O3/H2O Nanofluid

Mini-channel heatsinks have proven useful in removing high heat fluxes from microelectronic devices. However, further miniaturization of electronic devices requires significant enhancement in the mini-channel heatsinks’ thermohydraulic characteristics, which depend greatly on the coolant and geometrical configuration of the channel. Therefore, the current study explores the potential of mini-channel heatsinks’ using different coolants (water, nanofluid and supercritical carbon dioxide) and various channel configurations. The effect of various channel configurations on the thermohydraulic characteristics of the mini-channel heat sinks is evaluated numerically for different coolants employing three flow rates (17 g/s, 34 g/s and 50 g/s). Hence, the effects of fin height, spacing and thickness, and mass flow rate on the overall heat transfer coefficient (CHT) and pressure drop (ΔP) are reported for the abovementioned coolants. It is found that increasing the mass flow rate increases both the CHT and ΔP. It is also noted that increasing the fin height and spacing decreases both the CHT and ΔP, as opposed to increasing the thickness, which causes both the CHT and ΔP to increase. Among the three coolants used, the sCO2 shows superior performance compared to the water and nanofluid and this based on higher CHT and lower ΔP. Moreover, the performance evaluation criterion (PEC) for the sCO2 is higher than that for the water and nanofluid by 53% at 17 g/s flow rate and 243% at 50 g/s flow rate.

Optimum design for wavy fin tube in an air cooler with genetic algorithm

A strategy by multi-objective genetic algorithm (MOGA) combined with Kriging response surface is proposed for optimum design of wavy fin tube in an air cooler, while minimum pressure loss factor, maximum heat transfer factor and overall performance factor as three objective functions. The results show that the effects of fin height and fin density on the overall performance are positive and the wave number and wave angle are negative; The overall performance of parallel fin is higher than staggered fin; The overall performance of small pipe diameter of wave fin is higher than big pipe diameter; The overall performance reaches the optimum as fin height is 20.7 mm, fin density is 9.9, wave number is 11, wave angle is 4°; The multi-objective genetic algorithm combined with Kriging response surface eliminates the dependence on empirical relation. The results can be used to guide the optimum design of wavy fin tube.

Investigation on vibration parameters in aluminum finned tube arrays subjected to water cross flow

PurposePredicting the critical velocity is crucial at the instability threshold for shell and tube heat exchangers in order to prevent tube failure due to vibrations. In this study, the vibration response of an aluminum tube bundle subjected to water cross flow was analyzed experimentally. Aluminum tubes are preferred over steel tubes because of aluminum tubes' excellent corrosion resistance, ease of manufacture, and high thermal efficiency.Design/methodology/approachThe fluid elastic instability and vortex shedding mechanisms in a finned tube array of aluminum tubes with a base tube diameter of 19.05 mm and pitch of 34 mm were investigated. The current study considers parallel triangular finned tube arrays with fin heights of 3 mm and 6 mm with a uniform fin thickness and fin pitch. The plain tube array was tested to compare the finned tube array results. The tube vibration response was measured using an accelerometer mounted on the middle tube of the third row. In order to define the fluid elastic instability behavior of various tube arrays, the critical velocity at the instability threshold is measured. By finding the Strouhal number at the small peaks before instability, the vortex shedding behavior of the tube arrays is examined.FindingsThe results reveal that the critical velocity at instability for coarse finned tube arrays increases as the fin height increases. The effect of the tube material is evaluated by comparing the results with those previously reported for parallel triangular tube arrays made of steel. Finally, the occurrence of vortex shedding in a tube array is confirmed based on the Reynolds number and Strouhal number relationship. The instability constant K for the plain tube array of steel and aluminum material are 4.97 and 4.87, respectively.Originality/valueThis paper provides the research findings on the effect of fin height on coarse density finned tube array. This will add substantial knowledge to the literature in the field of fluid elastic instability and vortex shedding, which is needed for the safe functioning of shell and tube heat exchangers.

Study on heat storage performance of a novel vertical shell and multi-finned tube tank

High-efficient latent heat storage technology plays a crucial role in solar energy utilization. In this study, a shell-and-tube heat storage tank employing a novel fin structure has been proposed. A three-dimensional unsteady heat transfer model of the tank has been established. The effects of fin height, fin angle and fin number on liquid fraction, average temperature and heat storage rate have been investigated. The results show that the complete melting time of the phase change material in the novel finned tube is shortened by 66.4% compared with the finless structure. The melting time of the fins with heights of 34.20 mm, 42.75 mm, and 51.30 mm are shortened by 56.9%, 60.1% and 66.4%, respectively. When the fin height exceeds 51.30 mm, the melting rate remains almost unchanged. The fin angle is not the larger the better. Compared with the bending angles of 10°, 20° and 40°, the complete melting time of 30° is reduced by 14.0%, 11.6% and 6.4%, respectively. As the number of fins increases, the total heat storage time is shorter, but the total heat storage has also been reduced. The results can provide a good reference for design, operating, and energy-saving of latent heat storage systems.

Fluid elastic instability and vortex induced vibration parameters in finned tube arrays with P/D ratio 1.79

PurposeThis paper aims to analyze the effect of fin geometry on mechanisms of flow induced vibration. Finned tube arrays are used in a heat exchanger to increase its efficiency. Therefore, it is necessary to investigate the effect of geometric parameters of the fin fluid elastic instability and vortex shedding. In this paper, the effect of fin height, fin density and tube pitch ratio for parallel triangular tube array on fluid elastic instability and vortex shedding is analyzed.Design/methodology/approachExperimental analysis was carried out on a parallel triangular finned tube array with a pitch ratio of 1.79 subjected to water crossflow. The experimentation aims to study fluid elastic instability and vortex-induced vibration mechanism responsible for flow induced vibration for finned tube array. A fully flexible finned tube array of the copper tube was used with its base diameter of 19.05 mm and thickness of 2 mm. Over the tube surface, crimped fins of height 6 mm and the same material are welded spirally with fin density 8.47 mm and 2.82 mm. Experimental analysis was carried out on a test setup developed for the same. The results obtained for the finned tube array were compared with those for the plain tube array with the same base tube diameter.FindingsFor parallel triangular tube array of copper material, test results show that critical velocity increases with an increase in fin pitch density for low pitch tube array. Before the occurrence of instability, the rate of growth in tube vibrations is high for plain tubes compared to that with fin tubes. The results based on Owen’s hypothesis show vortex shedding before the occurrence of fluid elastic instability. The effect of fin geometry on vortex-induced forces is analyzed. For the tube array pattern understudy, the values of Conner’s constant K for coarse fin-tube and fine fin tube array are obtained, respectively, 6.14 and 7.25.Originality/valueThis paper fulfills the need for research on the effect of fin geometry on fluid elastic instability and Vortex shedding on a tube array subjected to water cross flow when the pitch ratio is less than two, i.e. with a low pitch ratio.

Numerical investigation on the influence of installation angle of inclined interrupted fins heat sink on heat dissipation performance

Numerical simulations of a symmetric array of inclined fins heat sink under natural convection had been carried out using the ANSYS icepak to solve the complete Navier-Stokes equation and the energy equation in the current study. The effects of fin height (20 mm ≤ H ≤ 40 mm) and heat sink installation angle (–45° ≤ φ ≤ 30°) were analyzed. The work fluid was the air. The results showed that when the input power was constant, as the fin height increased, the heat transfer performance improved. There was no better heat transfer performance than the case of fin height was 40 mm, of which the corresponding heat transfer resistance was also almost the lowest. Compared with H = 20 mm and H = 30 mm, the case of H = 40 mm can reduce the average substrate temperature by 5%−10%. The installation angle greatly affected the heat transfer performance of the heat sink. Compared with the negative installation angle, the positive installation angle showed stronger inhibition on the heat dissipation. The installation angle of −15° showed the highest heat transfer coefficient, which could improve the heat transfer coefficient by about 7%. The Nusselt number (Nu) was found to increase approximately linearly with the Rayleigh number (Ra) in the range of 8.5 × 106 ∼ 1.64 × 107. A correlation between Nu and Ra, the geometric parameters of fin arrangement and the dimensionless correlations related to the heat sink installation angle were obtained. Highlights A new type of fin heat sink was proposed to improve heat sink performance. The heat sink installation angles was studied with the best angle found. The correlation formula related to the installation angle was obtained.

Hybrid microchannel/multi-jet two-phase heat sink: A benchmark and geometry optimization study of commercial product

In this paper, an experimental study of two-phase cooling heat sink using the dielectric working fluid Novec/HFE-7000 is performed. The liquid flow is directed into microchannel fins through multiple impinging jets. A copper microchannel heat sink with a fin height of 3mm, fin thickness of 0.1 mm and channel width of 0.1 mm was used for removing heat flux from the heated surface. A copper block was used to mimic computer chip with a surface area of 1” x 1” (6.45 cm2). The experiment was performed at heat flux from 5 W/cm2 to 80 W/cm2, subcooling of 5 °C, 15 °C, 25 °C, and flow rates 1, 1.25 and 1.75 lpm. The results in the two-phase regime for high heat fluxes are compared with analytical correlations. Reduced subcooling can results in enhancement of heat transfer coefficient by 25 % but will increase the pressure drop through the heat sink. Heat transfer coefficient increases with flow rate in the single-phase region and in the convective boiling region. In nucleate boiling region, heat transfer coefficient increases with heat flux rather than flow rate. Geometry optimization of heat sink was carried out considering effects of fin height on thermal and hydraulic performance. It is found that thermal resistance variation with fin height shows a parabolic trend and an improvement of 46 % in thermal performance can be obtained. A new correlation was also developed to predict results of experimental data with mean absolute error of 7 %. The inclusion of Reynolds number and hydraulic diameter was found to considerably reduce error when compared to values obtained with the previously available correlation, in which only the subcooling and heat flux were the parameters for modelling the heat transfer.

Cooling Performance Analysis of Outside Fins of the Closed Circuit Axial Piston Transmission

Realizing conversion between fluid power and mechanical energy, the closed circuit axial piston transmission (CCAPT) plays a vital and indispensable role in miscellaneous industries. The frictional loss and leakage loss inside the system give rise to the inevitable temperature rise. In order to prolong the life of the device, a cooling structure on the outside of the CCAPT is designed for promoting heat dissipation. Based on the relevant heat transfer law and the temperature distribution of internal machinery elements, a spiral fin structure is designed at the shell side. With the help of numerical simulation, the effects of fin height, fin pitch, and fin thickness on the thermal performance are studied. The flow field and temperature field on the outside of the fin structure are obtained as a guidance for enhancing heat dissipation effect. Results indicate that the area of rotating elements tend to accumulate heat, where more attention should be paid for a better cooling effect. In addition to this, a moderate increase of fin height, fin pitch and fin thickness has a positive effect on heat transfer enhancement. The peak value of Nusselt number is obtained with a fin height of 7.5 mm, which is about 2.09 times that of the condition without the fin structure. An increase in fin pitch improves both heat transfer performance and comprehensive performance at the same. When fin pitch is 30 mm, Nusselt numberincreases 104% over the original condition.

NUMERICAL ANALYSIS OF EFFECT OF IMPINGING JET ON COOLING OF SOLAR AIR HEATER WITH LONGITUDINAL FINS

In this study, the effect of impinging jet cooling on solar air heater with and without longitudinal fins has been numerically investigated. The absorber plate surface of the solar air heater is modeled as a constant heat flux condition. Numerical analyses have been conducted on turbulent flow conditions (10,000 ≤ Re ≤ 50,000). The jet flow velocity has been taken constant. The effect of fin height and mass flow rate of working fluid on the thermal efficiency of the solar air heater has been analyzed in detail. Variation of the convection heat transfer coefficient as a function of Reynolds number has also been determined for finned and unfinned conditions. Temperature and local Nusselt number distributions on the absorber plate have been defined as contour graphs. It is found that the Nusselt number and thermal efficiency enhance by adding impingement jets and increasing the Reynolds number. Also, it is obtained from numerical analyses that the convection heat transfer coefficient increases with increasing the fins height. Finally, it is revealed that using impinging jets and fins enhances the efficiency and convection heat transfer up to 23.35% and 15%, respectively.

Effect of Fin Height and Rayleigh Number with Small Increments on Convective Heat Transfer in a Horizontal Annulus

Effect of Fin Height and Rayleigh Number with Small Increments on Convective Heat Transfer in a Horizontal Annulus

Augmentation of natural convection heat sink via using displacement design

Miniaturization of electronic devices demands an effective thermal management system for efficient cooling. Still, many electronic industries use natural convection cooling techniques like plate-fin heat sinks as far as no moving part (noise) and reliability is concerned. In this study, the widely-used plate fin heat sink is augmented by a novel fin displacement amid fin array. Yet the effect of fin displacement between alternate fins is experimentally and numerically investigated under natural convection condition. In the meantime, the effects of fin spacing, length, height, and heat flux on the heat sink performance subject to fin displacement is also studied. For the smaller fin pacing, introducing the fin displacement will delay the merging of boundary layers, and reduce the length of fully developed region accordingly. Smaller fin spacing can also entrain the outside air into the fin array at the upper portion of heat sink for offering additional enhancement. The fin displacement is especially effective for a smaller fin spacing. This is because fully developed flow prevails at a smaller fin spacing. On the other hand, the fin displacement may impair the performance when a very wide fin spacing is used. Similarly, the increase in the fin length also enhances the heat transfer performance under the fin displacement conditions. It is also found that the effect of fin height on the thermal performance is small and the effect of heat flux is negligible. The maximum reduction in the thermal resistance is 56% by adopting the displacement design. A drop in fin temperature at the upper portion with the displacement design may lead to a reduction in heat transfer coefficient. For the comparison containing the fixed volume, the heat sink with fin displacement offers a 30% heat transfer enhancement ratio, 28.7% reduction in total mass, and 27.4 % reduction in surface area when compared to the conventional heat sinks.

Effect of Fin Height on Performance of Passive Solar Still in Indian Coastal Conditions

Effect of Fin Height on Performance of Passive Solar Still in Indian Coastal Conditions

Thermal performance optimization and evaluation of a radial finned shell-and-tube latent heat thermal energy storage unit

Add of fin is a simple and effective way to enhance the thermal behavior of latent heat thermal energy storage (LHTES). The target of this research is finding the most appropriate radial fins arrangement to accelerate phase change material (PCM) melting process in vertical LHTES unit. The effect of adding aluminum fins which possess the much higher thermal conductivity compared to PCM on melting process was investigated by numerical simulation firstly. The full melting time of radial finned LHTES unit decreases 44.0% compared with LHTES unit without fin. Then, the effects of fin height and pitch on thermal performance are simultaneously considered. The dimensionless fin height of 0.642 is recommended in this study. The thermal performances of vertical finned LHTES with four different fin arrangements (lower fins, upper fins, middle fins and arithmetic fins) were explored. Numerical results show that the complete melting time could be reduced 49.9% by arithmetic fins. The root mean square (RMS) of liquid fraction is proposed to describe the uniformity of the melting process of PCM. In this study, the root mean square of the LHTES unit using arithmetic fins is the lowest in the four fins arrangements, following by lower fins, middle fins and upper fins. For maximizing thermal performance, adding arithmetic fins to LHTES is recommended.

Numerical investigation of the thermal performance enhancement of latent heat thermal energy storage using longitudinal rectangular fins and flat micro-heat pipe arrays

The performance of a new type of latent heat thermal energy storage (LHTS) device based on flat micro-heat pipe arrays (FMHPAs) with longitudinal rectangular fins is numerically studied by enthalpy–porosity technique based on finite volume method (FVM) in this research. The numerical model is verified correct. The temperature distribution and phase transition process in different directions of the interior of a thermal storage tank and the effects of fin height, spacing, and thickness on charging power and thermal storage capacity are also analyzed numerically. Results show that phase interface is presented in U type in the horizontal direction. In the vertical direction, the phase change material (PCM) among fins melts from up to down when the fin spacing is larger than 6 mm, and the opposite occurs when the fin spacing is less than 6 mm. The thermal storage capacity of the LHTS device is reduced drastically when the fin spacing is less than 4.14 mm. For fin height, the structure of multiple rows of FMHPAs with dwarf fins is recommended because it exhibits large power and exerts a small negative effect on thermal storage capacity. Fin thickness has a minimal effect on charging power and thermal storage capacity. The study results provide optimization design guidance for LHTS devices based on FMHPAs under various application backgrounds, such as solving the contradiction between energy supply and demand in solar thermal systems and the peak load shifting of electricity in heat pump systems.

Examination of effects of operating and geometric parameters on the performance of a two-bed adsorption chiller

A detailed numerical model of a two-bed adsorption chiller has been developed to examine the effects of operating and geometrical parameters on its overall performance. The condenser and evaporator are considered non-ideal in the present model. Therefore, their energy balances and heat transfer equations are integrated with the distributed-parameter fully coupled model for the two packed-bed adsorbers. Initially, the effects of fixed values of evaporating and condensing temperatures were evaluated for different three cases and two cycle times, the percentage change in the cooling capacity (CC) and COP were varied between +12.3% to −18.5% and +4.7% to −5.6% for the given cases, respectively, compared to the basic model developed in this study. At a certain cycle time of 840 s, the specific cooling capacity (SCC) and (COP) were increased significantly by about 42% and 68%, respectively, when the heat-transfer-fluid (HTF) flow changed from the case of laminar to the case of turbulent flow regimes. The parameters effects on theoretical chiller performance were in different manners. For examples; when the ratio of desorption/adsorption durations (TR) was adjusted to 0.782, both of the SCC and COP were maximized and enhanced by about 2.4% and 4%, respectively, compared to the basic model case. Regarding the impact of the fins’ number (Nfin), the SCC was doubled, reaching 305 W/kgads, when the tubes of 50 fins each were replaced by those of 200 fins per tube, while the COP attained the maximum of 0.59 at Nfin of 130 fins compared to the COP of 0.555 at Nfin of 50 fins for each tube. Furthermore, the effects of fin height and tube length have been investigated.

Optimum fin spacing of finned tube adsorber bed heat exchangers in an exhaust gas-driven adsorption cooling system

Adsorption cooling systems (ACS) are considered as potential alternatives to traditional vapor compression air conditioning systems in heavy-duty vehicles. In ACS, adsorber bed heat exchangers (ABHEx) replace compressors and their appropriate design directly impacts the ACS performance. During operation, ABHEx undergo a large temperature swing to derive a refrigerant in ACS and their response time affects the dynamic behavior of ACS. In this study, a detailed three dimensional non-equilibrium model is developed to study the effects of heat and mass transfer in annular and longitudinal finned tube adsorber beds filled with zeolite-13x particles. The effects of fin height and spacing are studied on the system operating parameters to identify an optimum fin geometry. The simulation results show that a decrease in fin spacing leads to a decrease in the coefficient of performance (COP) and an increase in the specific cooling power (SCP), and no optimum value is observed for them in a specific fin spacing. However, variations of the total cooling power (TCP) maximize at a certain fin spacing. For longitudinal finned tube ABHEx, the optimum averaged fin spacing shifts from 5.4 to 6.8 mm for the adsorber beds with 10, 15, and 20 mm fin heights, while the optimum fin spacing of annular finned tube ABHEx changes from 5.0 to 6.4 mm. Furthermore, the results show that under similar dimensions and operating conditions, an ACS with annular finned tube ABHEx provides a 10% higher total cooling power than that with a longitudinal finned tube ABHEx at the optimum fin spacing. Using the ACS with optimized ABHEx in a truck would annually save about 370 L of fuel consumption and decreases greenhouse emissions by up to 738 kg CO2e.

The effects of fin height, fin-tube contact thickness and louver length on the performance of a compact fin-and-tube heat exchanger

The effects of fin height, fin-tube contact thickness and louver length on the performance of a compact fin-and-tube heat exchanger