Circumferential Fins Research Articles

Application of performance dynamic equationin numerical simulation and optimization of waste heat utilization and storage system

In order to improve the current situation of double energy loss in waste heat recovery and utilization, according to the factors such as phase change temperature, thermal conductivity, phase change latent heat, economy, and safety of thermal storage materials, 70# phase change thermal storage balls produced by XX company were selected as phase change thermal storage materials, and differential scanning calorimetry was used to test and analyze them, and the melting point, freezing point and phase change latent heat value of PCM were obtained, provide data reference for simulation in the following text. The shell and tube heat exchanger is selected as the core component of the mobile heat storage system, and its heat storage and release processes are simulated using FLUENT software. The results show that when the heat transfer equipment is charged for 7 hours, almost all of the inner-heat exchangers have completed the heat supply, and only the phase change products at both sides and bottom of the heat supply have ?dead zone?, which is the major effect of heat storage. In order to improve the heat storage and release rate and break the ?bottleneck? of heat storage, the heat transfer was strengthened by changing the diameter size, arrangement, and adding fins of the heat exchange tube. The effects of straight fins, T-shaped fins, as well as the number, height, thickness, and width of fins on the heat storage performance were explored. The results indicate that, adding fins cannot only improve heat transfer efficiency, but also inhibit natural-convection. The heat storage and release time decreases to varying degrees with the increase of fin width, thickness, height, and the number of circumferential fins in a single heat exchange tube.

Effects of circumferential fin on cooling performance improvement of forced air-cooled battery pack

In demand for clean energy sources, batteries have a vital role to play. Batteries are the heart of many electrical energy storage systems, as in electric vehicles (EVs). The high internal heat generation from a battery is the main hindrance to battery performance and safety. The high-temperature environment impacts performance; therefore, maintaining the battery temperature within desired limits is essential. In this work, we focus on the increasing effectivity of forced air cooling for high-capacity batteries at high discharge rates, decreasing auxiliary power consumption without compromising the compactness of the battery pack. The novelty of this work is that we have developed a hybrid BTMS consisting of circumferential fins and forced air cooling. Using a circumferential fin clad to the cell body has the advantage of increasing the surface area of the battery pack so that the ability of air to extract heat from the battery pack is improved and the auxiliary power consumption is reduced. The experiments use thin circumferential fins of 0.5 mm thickness mounted on cell bodies and discharged at various rates. The numerical model has been developed and tested using ANSYS FLUENT software. Using a single circumferential fin (Model 1) improves cooling performance by 3.14 %, and using three circumferential fins (Model 2) improves cooling performance by 7.32 % in the natural convection mode compared to the uncooled model. The improvement achieved in forced air cooling with a velocity of 2 m/s and three circumferential fins cooling performance is improved by 18.71 %. It is observed that using fins, the overall increase in weight of the system is by 3.58 %.

Enhancement of the cooling by mixed convection of a CPU using a rotating heat sink: Numerical study

The technological progress made in recent years has driven electronic apparatus to become not only more efficient and work faster but also considerably smaller in weight and size. Furthermore, the power densities of these devices have known an impressive increase. However, the challenge for the electronic industry is the lifetime device improvement by controlling the adequate removal of their excess heat. The use of more efficient cooling systems is, therefore, crucial in order to ensure durable device functionality. In this work, computational simulation was carried out to study the enhancement cooling process mixed convection of an electronic component (CPU mounted in a motherboard) using a new design of a heat exchanger by combining the heat sink (the finned surface) and the fan in a single component, this allows more heat to be moved faster and with less energy than a conventional cooler. Three radial heat sinks (HS18, HS24 and HS36) are considered depending on circumferential fin numbers ( n = 18, 24 and 36). The effect of Reynolds number, heat flux and rotational velocity is investigated, and the optimum comprehensive performance was determined. The results reveal the cooling performance turns out to be better for heat sink with n = 36. The rotational velocity operates a significant effect on the temperature field only for values below than 900 rpm. We also found that the improvement in the Nusselt number and its percentage enhancement is intensified with increased rotational velocity and decreased with heat flux. A bigger Ω and ReΩ meant a more obvious heat transfer enhancement (NuΩ/Nu0) in the case of smaller Q, but (NuΩ/Nu0) decreased with increasing Q.

Experimental study of moist air condensation outside three-dimensional finned tubes with different fin parameters

The condensation of moist air is a common phenomenon in daily life and industry, and increasing its heat transfer coefficient has always been a hot spot in research. Three-dimensional (3-D) finned tube is an effective heat transfer enhancement element and its fin parameters have an important influence on the enhancement result. This study carried out experiments using orthogonal design and Taguchi method to determine the influence of 3-D fin parameters on moist air condensation. The contribution ratios of axial fin spacing, fin height, fin width, and circumferential fin spacing on the heat transfer coefficient were obtained and analyzed in detail. Meanwhile, the photos of condensation processes were obtained. Experimental results show that all the heat transfer coefficient increased with the increase of relative humidity (RH) or the decrease of cooling water inlet temperature. Besides, all the 3-D finned tubes had higher heat transfer coefficient compared with smooth tube. The contribution ratio of fin height on the heat transfer coefficient was the highest, which can be 75.7% at most. Besides, the contribution ratio of axial fin spacing increased from 10.1% to 24.0% with the increase of RH. The optimal parameters combination of 3-D fins within the range of this experiment was also recommended. The results obtained in this study can provide guidance for the design and optimization of 3-D finned tubes used in moist air condensation.

Modelling of Automobile Radiator by Varying Structure and Materials

Radiators used in the automotive application are a class of heat exchangers whose main purpose is to cool the coolant coming from the internal combustion engines. These coolants flow through tubes covered with fins that facilitate a faster way of heat transfer to the surrounding more efficiently. With the increase in efficiency of the engine cooling system it directly helps in the longevity of the engine in other words, the life of the internal combustion engine increases multifold times. Upon investigating we found different shapes that can be used to optimize the radiators efficiency. There are several other ways to improve the efficiency of a radiator. And these can be achieved by improving the surface area of the radiator, improving airflow through it, improving coolant property which flows through these tubes covered with fin all around and at last using alternate materials that prove to be more efficient than the present ones that are being used. The demand of the current times of climate change and energy crisis have paved way for improved heat transfer rates and designing radiators in smaller dimensions and sizes at the same time being more efficient than the previous generation of radiators. With the above conditions in mind, it has been found out that with a simple modification of changing the existing rectangular-shaped radiators into spiral-shaped ones thereby improving efficiency to improved levels, which finds its use in the current generation of vehicles which are benefitting from the improved rate of heat transfer taking place. The spiral radiator of copper tube used here is wound in two coils connected centrally. Spiral tubes of the radiator have circumferential fins. In this type of configuration, heat transfer rate will increase because of having a circumferential fin across the length of the spiral tube through which water flows. These design considerations have been done keeping in mind the major aims to achieve for this type of design and they are improving heat transfer rate and achieving compactness of shape of radiator. We also did Computational Fluid Dynamics or CFD Analysis to test the material properties for the application of heat transfer and how it fares against old materials.

Melting and solidification of PCMs inside a spherical capsule: A critical review

Abstract To date, numerous phase change materials (PCM) have been developed for application in latent heat storage systems. There are many issues in the process from the development of PCM to using them in storage systems, which should be resolved. The problem of heat transfer in PCMs during the phase change process is the most important one. Latent heat storage containers usually have simple geometrical forms such as a sphere, cylinder, cylindrical annulus, rectangular enclosure, etc. A large number of papers were published on melting and solidification processes in PCMs. Therefore, there is a pressing necessity for generalizing the art of the state in this field and establish how accumulated knowledge meets practical requirements. The present review considers the current state in investigations of heat transfer in a spherical shell. Heat transfer in PCMs during constrained melting (solid PCM fixed inside the vessel), unconstrained (unfixed) melting and solidification, and phase change in finned shells are analyzed. It is shown that currently, there is no satisfactory description of the constrained melting process. For unconstrained melting and solidification, some correlations are suggested, describing these processes. The applicability range of the proposed correlations, as well as their accuracy were investigated and established. To intensify the process of phase change inside the spherical container, the use of orthogonal fins is appropriate option compared to the employ of circumferential fins.

Forced convection condensation of R134a in three-dimensional conical pin fin tubes

This paper investigates the forced convection condensation heat transfer performance of R134a in circular tubes with three-dimensional conical pin fin structures. Five conical pin fin tubes of different circumferential fin pitch (pc) and longitudinal fin pitch (pl) were fabricated by Selective Laser Melting (SLM) with the aim of enhancing the internal forced convection condensation of R134a. Experiments were performed to characterize the condensation heat transfer coefficients (href) and pressure drops (ΔP) across these enhanced tubes. These experiments were conducted at the refrigerant mass fluxes (mref) of 50 kg/m2·s to 200 kg/m2·s, average vapor qualities (xave) from 0.2 to 0.8 and saturation pressure (Psat) of 13.4 bar. The effects of xave, mref, pc and pl on href and ΔP were determined and the results were compared against a commercial Al tube, a plain tube fabricated by SLM and two SLM fabricated enhanced tubes with dome-shaped fins. It was found that href of the conical pin fin tubes increases with increasing xave and mref and these values are also significantly higher than those of the plain tubes. Both pl and pc were found to significantly affect the href values of the conical pin fin tubes whereas the ΔP values were affected only by the change in pc. An efficiency index (η1) is defined to evaluate the thermal-hydraulic performances of the enhanced tubes. The experimental results show that all the conical pin fin tubes demonstrated higher η1 than the dome-shaped fin tubes. Based on the boundary layer approach, a semi-empirical model is developed to predict the Nusselt numbers of the conical pin fin tubes. Reasonably accurate predictions were achieved with an overall mean absolute error (MAE) of 10.5%.

CFD and Experimental Analysis of Phase Change Material Behaviour Encapsulated in Internally Finned Spherical Capsule

Phase change material (PCM) based Thermal Energy Storage (TES) system is a proven technology to store/release a large amount of energy as latent heat during the phase transition process. In spite of the advantages, a major weakness with PCMs is their low thermal conductivity in both solid and liquid phases which seriously affects the heat transfer rate. Over the past two decades various efforts have taken place to enhance the heat transfer rate during the melting/solidification process of phase change material (PCM) encapsulated in various shape of containers. However, very few attempts have been made on accounting the heat transfer augmentation in internally finned spherical capsule. In the present study, CFD analysis is carried out to explore and report the effect of fin orientation on heat transfer enhancement of a paraffin PCM filled in an internally finned spherical capsule. Keeping the same surface area of fin but oriented differently (orthogonal and circumferential) in spherical capsule is undertaken for the computational analysis. In addition, spherical capsule with no fin configuration is alsoconsidered in the present analysis to compare with finned configuration results. The CFD results showed that the orthogonally finned spherical capsule resulted in appreciable reduction in total time takenfor complete melting/solidification process than the circumferential fin and no fin configuration. Thesame computational study is performed experimentally in order to validate the CFD results.

HEAT TRANSFER ENHANCEMENT USING CIRCUMFERENTIAL FINNED TWISTED TAPE HEAT EXCHANGER

The most desirable feature in any thermal equipment is the enhancement of heat transfer. Heat transfer is basically a slow process and is enhanced by adopting passive or active methods of enhancement. In passive enhancement methods, heat transfer is increased without demanding any external power source; while in active method, enhancement in heat transfer demand external power. In this work, a passive enhancement method is proposed and tested to check the extent of heat transfer enhancement noticed. A tube in shell heat exchanger is designed with circumferential fins attached along the length of tube and a spiral insert running inside the tube. One fluid is made to flow inside the tube under the influence of twisted tape and the shell side fluid is running around the tube continuously provoked by fins. Therefore, the hot and cold fluids were estimated to exchange more heat because of thorough mixing initiated in their flow paths. In this work, analysis was made in CFD package by creating a model that simulates experimentations observed in the literature. The results of experiments and results of CFD analysis were compared. Noticing the agreement between the results, the CFD model is given enhancements like circumferential fins and twisted tape to check the enhancement in heat transfer. The velocity and temperature contours were observed at various flow conditions (Reynolds numbers). Based on results of analysis, thermal performance factor is also estimated to check the increment in heat transfer with reference to hydraulic (or flow) parameters.

Three finned press-fit cup: Does its initial fixation strength provide an adequate stability? Clinical midterm results of 685 implants

Introduction: One of the major causes of loosening of cementless acetabular cup implants is insufficient initial stability. A technical proposal to decrease the risk of suboptimal first stability is a circumferential finned design of the cup. This design aims to improve periacetabular bone contact and prevent rotational micromotion of the cup when optimal press-fit cannot be obtained. Materials and Methods: We retrospectively reviewed a group of 712 consecutive patients who underwent total hip arthroplasty from June 2006 to June 2014. In all patients, a titanium cup, characterized by three anti-rotational circumferential fins at the superior pole, was implanted. Results: Five hundred and ninety-two patients, for a total of 685 hips, were evaluated at a mean follow-up of 58 months (range 12-96 months). At 1-year follow-up, the average score increased to 82.90 (range 100-70) and at the final follow-up (58 months, range 12-96 months), it was 80.12 (range 100-66). In 22 cases (3%), screws to obtain a secure primary stability of the cup were used. Nineteen complications (2.6%) needing revision surgery were observed. Survivorship at 10 years was 98.7% (95% confidence interval [CI], 98.7-99.7%) with revision for aseptic cup loosening as an endpoint and 96.7% (95% CI, 98.3-95.1%) with revision for all causes of revision as the second endpoint. Discussion: In our group of patients, we did not observe the cases of very early cup loosening. The only two-cup revision, do to loosening of osteolysis, was observed 26 and 32 months before surgery. Conclusion: Our very low rate of additional screws represents an indirect sign of finned cup first stability. Three-finned cup design clinically confirmed to improve initial cup stability.

AN EXPERIMENTAL INVESTIGATION OF ANNULAR FINS UNDER FORCED CONVECTION

Heat transfer characteristics under forced convection are investigated experimentally by varying parameters like surface area, base-to-ambient temperature difference and Reynolds number. To investigate the performance of fins experimentally, fins made of aluminium (high thermal conductivity) are taken. For varying the surface area fin with 11 mm diameter without circumferential fins, fin with 31 mm diameter and annular fins of 31 mm diameter are taken as specimens. Base to ambient temperature difference is varied with the aid of dimmerstat ranging from 25W to 45W. Reynolds number is also varied by varying the velocities of air. Velocities are varied by the aid of fan. Then these fins are tested under different load conditions, different Reynolds number by varying the surface area of fins increase the rate of heat transfer. With the variation of relevant parameters under forced convection heat transfer rates are analyzed experimentally. Experiments are conducted by using the annular fins, fin with diameter 11mm without circumferential fins and fin with diameter 31mm at different Reynolds number and loads under forced convection and comparison is made between fins. Experimental results shows that forced convection heat transfer rate from fins depend on surface areas, base ambient temperature difference and Reynolds number. The base temperature for annular fins is reduced by 30% when compared to fin with diameter 11mm due to increase in surface area about 40%. The base temperature for annular fins is reduced by 10% when compared to fin with diameter of 31mm due to decrease in surface area about 41%. It is also observed that at higher heat load i.e., 45W, the overall fin efficiency of annular fins is increased by 44% and 8% compared to fin with diameter of 11mm and 31mm respectively. At higher Reynolds number range 800-2000, heat transfer rate increases in annular fins due to more number of air molecules get in contact with the heated surface. ---------------------------------------------------------------------***--------------------------------------------------------------------INTRODUCTION Heat generation is the result of many engineering system. But due to unwanted heat overheating and failure of the system occure so the heat generated with in the system should be dissipated to surrounding in order to maintain the system working effectively and reliably. To overcome from this problem, thermal systems with effective emitters as fins is considerable, to achive the desired rate of heat dissipation. The heat dissipation from system to atmosphere can be obtain by using of convection and radiation heat transfer. As we know that the heat transfer rate can be increased by increasing the surface area or heat transfer coefficient.

相变材料在含翅片球形容器内的约束熔化传热过程

Spherical capsules are widely used as housing for phase change materials (PCMs) in heat exchangers for thermal energy storage applications. In view of the low thermal conductivity of common PCM candidates, extended surfaces, such as fins, are routinely added to PCM capsules to improve the thermal performance. In this paper, to quantitatively evaluate the influence of fins on the thermal performance of PCM-filled spherical capsules, constrained melting heat transfer of a PCM in a circumferentially finned spherical capsule with various fin heights was investigated both numerically and experimentally under constant-temperature boundary conditions. The enthalpy-based model was used in the numerical simulations to deal with phase change, while the control volume method was used to solve the governing equations for the melting problem with natural convection in the liquid phase. A spherical melting facility that allows for direct observation of the solid-liquid phase interface during melting was designed and constructed. The spherical capsule and fins were made of glass and aluminum, respectively. Octadecane with a nominal melting point at 28.2°C was used as the PCM. Qualitative agreement was obtained between the experimentally observed and numerically predicted results of solid-liquid interface evolution. The sources of the differences were identified to be the departure of the physical model from the real system, as well as simplifications of the numerical model. The evolution of the natural convective flow and temperature fields during melting are presented in the form of a series of snapshots of streamline and isotherm contours. The heat transfer mechanisms during melting were interpreted by these contour snapshots. The presence of circumferential fins not only enhances heat conduction, but also augments natural convection heat transfer in localized areas in the vicinity of the fins. The localized interactions between these two effects are significantly affected by the fin height. Under the specific conditions considered, fins with height-to-radius ratios of 0.25, 0.50, and 0.75 decrease the total melting time by 10.6%, 20.2%, and 28.7%, respectively, leading to a significant increase of the thermal energy storage rates in the spherical capsule. Although the presence of fins benefits heat transfer enhancement, a more comprehensive understanding of the effects of other important factors, such as the inclination angle of the spherical capsule, is required.

Heat Transfer Studies on Air Cooled Spiral Radiator with Circumferential Fins

Heat exchangers find use in several applications such as in automobiles, refrigeration, air conditioning, and water treatment plants. Radiators are a class of heat exchangers in which heat transfer occurs by means of air flowing across a series of finned tubes, eventually decreasing the temperature of the fluid to be cooled. The energy crises of recent times have necessitated improved heat transfer rates and at the same time the need for making heat exchangers smaller and more energy efficient. A simple modification has been carried out in the existing configuration of radiators, with a view to improve its efficiency and has resulted in the development of a compact spiral radiator against a standard air cooled fin and tube radiators used commonly especially in automobiles. In this configuration, water flows through spiral tubes, which are fitted with circumferential fins and air flows across the tubes for bringing about heat transfer.A numerical investigation has been carried out on the spiral radiator to study flow characteristics and thermal performance by means of local element by element analysis utilizing ɛ-NTU method. Experiments were performed and the results after comparison with the theoretical values were found to be promising. From the experimental data, a correlation among the important dimensionless numbers has been obtained using GARCH tool.

Effect of design on the initial stability of press-fit cups in the presence of acetabular rim defects: experimental evaluation of the effect of adding circumferential fins

This experimental study was undertaken to examine the fixation characteristics of a six-finned acetabular cup in both primary and revision arthroplasty in comparison with two other commonly used cup designs without fins. All three cup designs (Ananova® [Intraplant], Plasmacup® NSC [Aesculap]; Exceed ABT™ [Biomet]) were implanted into validated models of normal and revision acetabula. The defect models were designed to simulate a dorso-cranial rim defect of 90° width and 10 mm in depth (moderate rim defect) and a dorso-cranial rim defect of 130° width and 15 mm in depth (severe rim defect). The fixation strength of the three cup designs was tested by cyclically edge-loading the implanted cups using a mechanical testing machine. The six-finned Ananova implant exhibited greater resistance to foam-cup interface motion than both the Plasmacup and Exceed ABT implants. The largest average differences were observed in the resistance to ultimate spin-out, with Ananova outperforming Exceed ABT and Plasmacup by 26% and 17% in the moderate and by 36% and 38% in the severe defect models, respectively. The six-finned Ananova cup was significantly more resistant to edge loading both in the normal acetabulum and in acetabula with moderate to severe dorso-cranial rim defects than cup designs without fins, indicating that it may cover a wider range of clinical indications than conventional press-fit cups and provide clinicians with the confidence that, in primary and simple revision arthroplasty, adequate fixation strength can be obtained.

Conduction Characteristics of Frosting Circumferential Fin of Rectangular Profile

Through the appropriate assumptions, a mathematical model was derived on circumferential fin of rectangular profile coated with frost layer, and a new analytical solution is presented and compared to alternative approaches for calculating the fin temperature and efficiency. The analytical solution enhances the accuracy ,and have a simpler form of expression. It can be easily used in engineering practice. The solution is useful for other cases of a low-thermal-conductivity coating on a high-thermal-conductivity substrate .

Condensation of Steam on Pin-Fin Tubes: Effect of Circumferential Pin Thickness and Spacing

Experimental data are reported for condensation of steam at atmospheric pressure and low velocity on five three-dimensional pin-fin tubes. The main geometric parameters varied were the circumferential pin spacing and thickness, since these have been shown to have a strong effect on condensate retention, and the present study shows some evidence for an optimum circumferential fin spacing. Enhancements of the vapor-side heat-transfer coefficient of up to 4 were found, compared to a plain tube at the same vapor-side temperature difference. The measured enhancements are equal to, but do not exceed, those obtained from “optimized” two-dimensional integral-fin tubes reported in the literature—an observation that is also generally true for condensation of refrigerants. The evidence suggests, however, that three-dimensional fin profiles can produce worthwhile enhancement over those obtained from simple, two-dimensional, integral-fin tubes, but that more work is needed to understand the phenomena involved so that more efficient geometries can be developed.

SENSITIVITY ANALYSIS IN THE HEAT TRANSFER IN A FINNED NUCLEAR FUEL ELEMENT

To carry out sensitivity analysis on a finned surface, the differential perturbative method
is applied in a heat conduction problem within a thermal system, made up of a onedimensional
circumferential fin on a nuclear fuel element. The model is described by the
temperature distribution equation and the further specific boundary conditions. The adjoint
system is used to determine the sensitivity coefficients for the case of interest. Both, the
direct model and the resultant equations of the perturbative formalism are solved. The
convective heat flow rate of the fin and the average excess temperature were the response
functionals studied. The half thickness, the thermal conductivity and heat transfer
coefficients, and the excess temperature at the base of the fin were the parameters of
interest for the sensitivity analysis. The results obtained through the perturbative method
and the direct variation had, in a general form and within acceptable physical limits, good
concordance and excellent representativeness for the analyzed cases. It evidences that the
differential formalism is an important tool for the sensitivity analysis and also it validates
the application of the methodology in heat transmission problems on extended surfaces.
The method proves to be necessary and efficient while elaborating thermal engineering
projects.

SENSITIVITY ANALYSIS IN THE HEAT TRANSFER IN A FINNED NUCLEAR FUEL ELEMENT

To carry out sensitivity analysis on a finned surface, the differential perturbative method is applied in a heat conduction problem within a thermal system, made up of a onedimensional circumferential fin on a nuclear fuel element. The model is described by the temperature distribution equation and the further specific boundary conditions. The adjoint system is used to determine the sensitivity coefficients for the case of interest. Both, the direct model and the resultant equations of the perturbative formalism are solved. The convective heat flow rate of the fin and the average excess temperature were the response functionals studied. The half thickness, the thermal conductivity and heat transfer coefficients, and the excess temperature at the base of the fin were the parameters of interest for the sensitivity analysis. The results obtained through the perturbative method and the direct variation had, in a general form and within acceptable physical limits, good concordance and excellent representativeness for the analyzed cases. It evidences that the differential formalism is an important tool for the sensitivity analysis and also it validates the application of the methodology in heat transmission problems on extended surfaces. The method proves to be necessary and efficient while elaborating thermal engineering projects.

An oblique rotating barrel electrochemical reactor for removal of copper ions from wastewater

An experimental study was performed using an oblique rotating barrel cathode to recover copper from a simulated wastewater, which initially contained 100 parts per million (ppm) of cupric ions. The barrel was a perforated cylindrical polypropylene basket having several axial and circumferential fins on its exterior surface. It was partially filled with copper Raschig rings and was partially submerged in the wastewater at a tilted angle from the horizontal position. During the operation, the barrel was slowly rotating about its axis and the copper rings were made as the cathode by connecting them to a d.c. power supply through a dangler contact. The movement of exterior fins and tumbling motion of copper rings provided a high mass transfer rate and a large cathode area for copper electrodeposition reaction. The cupric ion concentration in the wastewater was reduced to less than 1.0 ppm, permitting discharge of the treated wastewater to the drain system. With an operating cell voltage of 2.5–5.0 V, the overall cathode current efficiency was 53–20%, and the electric energy requirement was 4 to 21 kWh per kilogram of copper recovered from the wastewater. An apparent first order reaction rate constant for copper electrodeposition reaction on the Raschig rings was measured as a function of process variables including cell voltage, barrel rotational speed, percentage barrel loading, barrel tilt angle and percent barrel immersion.

Combined convection and radiation in a tube with circumferential fins and circular disks

Combined convection and radiation heat transfer in a circular tube with circumferential fins and circular disks is investigated for various operating conditions. Using a finite volume technique for steady laminar flow, the governing equations are solved in order to study the flow and temperature fields. TheP- 1 approximation and the weighted sum of gray gases model (WSGGM) are used for solving the radiation transport equation. The results show that the total Nusselt number of combined convection and radiation is higher than that of pure convection. If the temperatures of the combustion gas and the wall in a tube are high, radiation becomes dominant. Therefore, it is necessary to evaluate the effect of radiation on the total heat transfer. Key Words: Convection, Radiation, Nongray Radiation,P- 1 Approximation, Weighted Sum of Gray Gases Model