Improvement In Heat Transfer Rate Research Articles

Design and development of single screw conveying machine for pyrolysis of waste plastics using nano zeolite particles in fixed bed reactor

In the present economic growth, the energy produced from sustainable resources plays a vital role rather than from non-renewable energy resources. There are many alternative sustainable energy resources available for energy development, such as biomass, hydropower, and wind energy. Another interest in current research is the conversion of waste plastic material into liquefied fuel. The use of plastic materials implies high demand and causes depletion of natural resources. Moreover, tons of used plastic materials are ending up in the oceans, landfill or open burning causes pollution. So, a suitable waste management strategy implies controlling or reduce the pollution causing the environment. In this present work, a new method has been addressed to extract liquefied fuels from waste LDPE plastics. A single screw conveying machine setup is fabricated to mix the shredded waste plastics with Nano zeolite catalyst. The various weight percentage of plastic material and zeolite catalyst is mixed and subject to pyrolysis process. The distribution of nano zeolite catalyst with the plastic wastes was found to be even, which leads to improved heat transfer rate, pyrolysis temperature, and reduced reaction time also produces a higher pyrolytic oil yield of 7%. The FT-IR results of extracted pyrolytic oil outcomes showed clear peaks of carbon and oxidizing agent chemical bonds in all liquid oil samples also alkanes present in the oil are confirmed with the GC–MS results. The liquid oil has a higher heating value range of 9820–9860 Kcal/kg, which is close to the standard diesel fuel heating value.

Numerical investigation of a nanofluidic heat exchanger by employing computational fluid dynamic

Shell-and-tube heat exchanger is widely applied in different industrial processes and energy systems. Utilized fluid in the heat exchanger and its thermophysical properties are among the key factors that influence the thermal performance and fluid flow in heat exchangers. Employing nanofluids, with enhanced thermal properties, can improve heat transfer rate of heat exchanger. In this regard, the current article concentrates on the numerical simulation of a shell-and-tube heat exchanger with baffle, utilizing multi-walled carbon nanotube/water nanofluid. In this regard, computational fluid dynamic is used for modeling. The applied turbulence model in this study is k- $$\varepsilon$$ which is selected based on the literature review. Heat transfer rate comparison in cases of utilizing the nanofluid in shell side of heat exchanger revealed high potential of the nanofluid in thermal performance improvement. Moreover, it was noticed that by using higher concentration of the nanofluid, more enhancement would be obtained which is owing to higher increment in the nanofluid effective thermal conductivity. Average increment in the heat transfer rate of the HE in case of using multi-walled carbon nanotube/water with 4% concentration is around 29.5% in comparison with the condition water is used as the operating fluid.

Fans arrangement analysis in oil forced air natural cooling method of power transformer radiator

The cooling of radiators in power transformers employing natural oil-air forced method is the purpose of this study. Two modes used for cooling fans, namely vertical and horizontal placement, will be compared as well. Four sets of radiators have been studied in this research, and in each set, 14 fins and three fans with a diameter of half a meter have been used. The fans will be arranged such that three of them will be placed under the radiator (in vertical position) in the first case, while in the second case, they will be located in one side of the radiator (in horizontal position). The results derived from the comparisons indicate the superiority of the horizontal mode in heat transfer against the vertical mode. Furthermore, it is notable that if the internal fan is disconnected, the cooling can be enhanced with the help of some existing points in the vertical mode. The improvement in heat transfer rate can be observed through locating the vertical fans optimally, once compared to the horizontal placement. The lower reliability of the vertical mode can be detected once the side fans are disconnected, while in any cases, the heat transfer superiority is achievable for horizontal mode. That is because, the disconnection of one of the fans, leads to the negligence of the radiators major parts in the vertical mode.

NUMERICAL AND EXPERIMENTAL INVESTIGATIONS ON PERFORMANCE EVALUATION OF A CONICAL OFFSET VORTEX GENERATOR INSERTS TO IMPROVE CONVECTIVE HEAT TRANSFER COEFFICIENT

The passive augmentation technique is widely used by researchers from thermal engineering field and it has shown excellent results for convective heat transfer rate. This paper shows the numerical and experimental findings for convective heat transfer characteristics and friction coefficient. Tests were conducted for turbulent flow, using air as medium through a uniformly heated steel pipe containing a novel kind of insert named as Conical offset Vortex Generator (COVG). The simulation tests were performed for turbulent flow with varying Reynolds number in the range 4000 to 50000. The parameters were analyzed during tests are pitch to smooth tube diameter ratio (p/d) and angle of attack (α). Various simulation tests were carried out with the help of ANSYS Fluent software to optimize the geometry. The simulation tests were carried out for different angle of attack (α = 15°, 30°, 60°). COVG with angle of attack (α = 60°) shows more enhancement in heat transfer rate, hence it was used for the experimentation purpose. The experimentation is conducted for various pitch to diameter (p/d = 1.18, 1.97, 3.94). The numerical and experimental results show improvement in heat transfer rate as there is decrease in pitch to smooth tube diameter ratio (p/d) and it also increases the value of friction factor. The reason behind the improvement in heat transfer rate is that, the braking of thermal boundary layer near the wall surface. Experimental results show the enhancement of Nusselt number from 3.46 – 6.7.

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.

Experimental investigation of enhanced cooling performance with the use of hybrid nanofluid for automotive application

The hybrid nanofluids exhibit remarkable thermal performance as coolant in automobile radiators. Hybrid nanofluid predominantly improves the heat transfer performance as compared to conventional coolants. Therefore, the present research work is focused on the hybrid nanofluids as coolant for automobile radiator. Due to improved heat transfer rate of hybrid nanofluid, the overall size of automobile radiator can be reduced. The heat transfer characteristics of Multi Walled Carbon Nanotubes (MWCNT)-Copper Oxide (CuO)/deionized water and Graphene/deionized water nanofluids were analyzed experimentally compared with deionized water. The experimental work aimed to find thermo physical properties such as thermal conductivity, specific heat capacity, and density of hybrid nanofluids. The concentrations of MWCNT-CuO and Graphene nanofluid were varied from 0.05 to 0.15wt%. Significant improvement in the stability was observed by magnetic stirring and ultra-sonication process with the Sodium dodecyl sulphate (SDS) surfactant. The effect of SDS surfactant on stability of MWCNT/CuO and Graphene nanofluid experimentally investigated. Effect of coolant flow rate on heat transfer rate is studied experimentally by varying coolant flow rate (3-7 lit/min) for different temperature (50°C to 80°C) conditions.Based on the experimental observations it was noticed that the Nusselt number of the hybrid nanofluid is linear relationship with the nanocoolant flow rate and a highest Nusselt number of 37.7 was observed at 0.1 %wt and 7 lit/min nanocoolant flow rate at 80°C inlet temperature. It was observed that aqueous based MWCNT-CuO hybrid nanofluid enhanced the convective heat transfer coefficient by 295% as compared to conventional base fluid at 80°C and 7 lit/min nanocoolant flow rate. It was also observed that the convective heat transfer coefficient for MWCNT-CuO/Deionized water hybrid nanofluid is 30% more than graphene based nanofluid at higher operating temperature (80°C) and higher coolant flow rate (7 lit/min). Further experiments were conducted at higher mass flow rates and temperature to investigate the maximum heat transfer ability of Graphene-CuO and MWCNT-CuO hybrid nanofluids as a feasible nanocoolant for automotive application.

Study and Analysis for the improvement of Heat Transfer Rate of AC Evaporator by Optimizing Materials

Study and Analysis for the improvement of Heat Transfer Rate of AC Evaporator by Optimizing Materials

Experimental and numerical investigation of microencapsulated phase change material slurry heat transfer inside a tube with butterfly tube inserts

In this research, the effect of microencapsulated phase change material (MEPCM) addition to water and producing MEPCM slurry (MPCS) for heat transfer augmentation was investigated, experimentally and numerically. Copper tube with and without butterfly tube inserts (BTI) was used as a test section in a laboratory apparatus and was heated at a constant heat flux. Experiments were performed to determine heat transfer coefficient of MPCS at the Reynolds number of 1500 and 2600 and containing up to 15 wt% MEPCM. The effect of tube inserts type was also investigated numerically. The results showed that for the plain tube, the addition of MEPCM to the base fluid improves heat transfer rate by up to 40.3% and 38.9% for non-laminar and laminar flow regimes, respectively. Moreover, when the BTI was used, it was observed that the heat transfer rate increased by up to 234% for pure water and by up to 180% for the 10 wt% MEPCM slurry under laminar flow regime. This is due to the turbulence induced in the flow and the disturbance to the thermal boundary layer. Moreover, tube inserts cannot have a significant effect on the heat transfer under non-laminar flow regimes. The inserts only increase the pressure drop in these conditions. However, performance evaluation criteria (PEC) analysis indicated that 5% MEPCM slurry provides the highest ratio of heat transfer enhancement to pressure drop increment. Furthermore, in the simulation section, the results clearly indicated that the inserts shape have no significant effect on the heat transfer coefficient.

STATIC THERMAL ANALYSIS OF FINS MODELS USING ANSYS

The Engine chamber is one of the essential engine components, that is subjected to over the top temperature differences and thermal stresses. Fins are set on the surface of the cylinder to improve the quantity of heat exchange by convection. When fuel is burned in an engine, heat is produced. Additional heat is also generated by friction between the moving parts. In air-cooled I.C engine, extended surfaces called fins are provided at the periphery of engine cylinder to increase heat transfer rate. That is why the analysis of fin is important to increase the heat transfer rate. The main of aim of this work is to study various researches done in past to improve heat transfer rate of cooling fins by changing cylinder fin geometry and material. In the present work, Experiments have been performed to discover the temperature variations inside the fins made in four kind geometries (plate Fins, Circular Pin fins, plate fins with holes, and draft Pin fins) and consistent state heat exchange examination has been studied utilizing a finite element software ANSYS to test and approve results. The temperature variations at various areas of fins models are evaluated by FEM and compared models of fins performance by heat flux and temperature variations obtained by experimentally in Analysis. The principle implemented in this project is to expand the heat dissipation rate by utilizing the wind flow. The main aim of the study is to enhance the thermal properties by shifting geometry, material, and design of fins.

Towards the development of a high power density, high efficiency, micro power generator

An innovative method to use combustion-based source for portable power generation for Microelectromechanical systems with significant improvement in power density and conversion efficiency has been reported in this study. A triple microcombustor configuration with backward facing steps and associated provision for efficient heat recirculation is proposed for flame stabilization. The presence of three parallel combustion zones increases the combustion intensity compared to a single combustor configuration and enhances the overall thermal performance. A novel technique to extract maximum heat from the hot combustion products for thermoelectric power generation is implemented. The thermoelectric modules are mounted to facilitate direct contact of the module surface with the hot combustion products. A significant improvement in heat transfer rate from the hot combustion gases to the thermoelectric modules (~16 times) is achieved. An electric power output of 4.9 W with overall conversion efficieny of 5.09% at a mixture velocity of 10 m/s and a mixture equivalence ratio of 0.9 is achieved. This signifies an improvement of ~10–20% in overall conversion efficiency as compared to previously reported systems.

Effect of a zinc oxide nanoparticle fuel additive on the performance and emission characteristics of a CI engine fuelled with cotton seed biodiesel blends

With advancement in technology and production of nano-sized particles, access and more importantly cost of nanoparticles have come down. This gives an exciting opportunity to tackle the strict regulations for emissions being in place which poses an urgent need to reduce emissions of not only new vehicles but of existing vehicles with as little modification as required. Not a lot of extensive work has been conducted in terms of emissions, combustion and performance characteristics of fuel mixed with metallic Nano sized powders. Zinc oxide is one such exciting nanoparticle because of its properties such as improvement of heat transfer rate, flash point, fire point, ability to store energy in it crevices and mass diffusivity, when dispersed in any fluid medium. And also it increases catalytic properties and provided higher surface to volume ratio. In the present work the Biodiesel derived from cotton seed oil has been employed as fuel along with 80 ppm ZnO and is considered for investigation. A Kirloskar diesel engine has been employed to conduct the experiment at varied load. In this experiment Diesel has been considered as baseline reading and four other fuels. The engine has been run from 0% to 100% load using the 5 fuels and the results have been evaluated, tabulated and plotted on graphs for discussion. Thus by employing this additive, the emissons are decreased without penalizing the performance and combustion characteristics.

Comparative study of heat transfer characteristics of a tube equipped with X-shaped and twisted tape insert

In order to investigate the effect of insert tape geometry on the heat exchanger tubes, present study compares thermal characteristic of water flowing in a tube equipped with X-tape and twisted tape. Material of the insert tapes used in the investigation is stainless steel. Thermal performance of heat exchanger tube has been analysed in terms of heat transfer rate (Q), Nusselt Number (Nu), friction factor (f). Significant enhancement in thermal performance was observed for X tape compared to twisted tape insert. Forced turbulence created due to modified geometry of tape played vital role in improvement of heat transfer rate in the tube. The X-shaped tape showed an enhancement of 1.27 times in heat transfer rate with respect to twisted tape. Computational fluid dynamics (CFD) analysis of the proposed tapes was performed to validate the obtained results.

Technological improvement on energy-efficient methods applied to a solar cavity collector

An advanced and improvised version of a flat plate collector is the solar cavity collector (SCC). The experimental analysis of an SCC with various working parameters is presented in this research paper. Overall dimensions of the SCC are 1.25 × 0.85 × 0.05 m. Initially, SCC has been tested with aluminium and copper as receiver materials. Various length to diameter ratios [L/D ratio] have been experimented viz., 40, 50, and 78.74. Comparisons have been made for its optimal performance with circular and rectangular type cavity and also with cavity cover materials. Pebbles are used in SCC for the improvement in heat exchange as a sensible heat storage material. Further to achieve improved heat transfer rates between the cavity and the transport fluid (water), heat transfer fluid [HTF] has been incorporated in SCC. It has been tested with different mass flow rates of water such as 0.002, 0.0025, 0.003, 0.0035, 0.004, and 0.0067 kg/sec to investigate and find its optimal performance parameter. Copper used as a receiver material gives better performance than other materials. HTF is considerable for larger mass flow rates of water.

A Numerical Research of Heat Transfer in Rectangular Fins with Different Perforations

Heat Transfer enhancement needs buoyancy force. This is to be achieved by making perforations on fin surfaces. The present paper is a study on the enhancement of heat transfer in terms of density, velocity and temperature with three different perforation geometry (parallel square, inclined square and circular). CFD was used to carry out the study of density variation, velocity and temperature drop among different perforated fins. This type of perforated fin has an improvement in heat transfer rate over its dimensionally equivalent solid fin.

Enhancement of Heat Transfer Characteristics of Plain Fin Coated with Brass and Aluminium

Rate of heat transfer plays a very important role in the performance of thermal systems like heat engines, steam power plants, refrigerators, air conditioners etc. Continuous efforts are being made to improve the effectiveness of the mentioned systems. Thermal conductivity of material effects the heat transfer characteristics the most and can be enhanced by surface coating of various materials. Materials with high thermal conductivity are preferable for providing coating on substrate to improve heat transfer rate. In present work, fins made of Stainless Steel 304 coated with Brass and Aluminum (250 micrometers thickness) by Twin wire arc coating process, is investigated. Experiments were conducted with and without coating at different heat input using Pin Fin Apparatus and calculated Nusselt number, Reynolds number, thermal conductivity, heat transfer coefficient, fin efficiency. From the results obtained, it is concluded that Nusselt number in case of S.S coated with Aluminium is increased by 1.36% compared with coated with brass and 2.1% compared without coating and there is an increase in efficiency of fin coated brass and Aluminium materials by 14-73% compared to without coating.

Thermal and Flow Analysis of Split Drop-Shaped Pin Fins for Improved Heat Transfer Rate

Proper dissipation of thermal energy has always been a requirement for better efficiency of a system. Fins provide additional surfaces to reject heat to the surrounding from the working faces. The current work considers the thermal analysis of pin fins of circular and drop-shaped cross section. Fins of uniform cross section are placed over a base plate arranged in a staggered manner. With an analysis of various thermal and flow parameters, the drop-shaped pin fin is found to yield a better thermal enhancement over cylindrical pin fins. Further, the drop-shaped fins are modified to make a split to enhance the interaction between the fluid and the fin surface. The modification shows slightly better result compared to existing drop-shaped fin. The modelling has been done using ANSYS FLUENT 17.1.

Analysis on thermal and flow behavior of triple concentric tube heat exchanger handling MWCNT-water nanofluids

Design of heat exchangers and heat transfer enhancement methods are struggling to meet out the cooling demand of present scenario. Many researchers suggested that the addition of nanosized solids particles into traditional base fluids resulting the higher heat transfer rate than the existing coolants and named the new fluids as nanofluids. In this investigation, the effect of microwave carbon nanotube (MWCNT)-water nanofluids on heat transfer rate, pressure drop and pumping power of a triple concentric tube heat exchanger are experimentally investigated and compared the results of MWCNT-water nanofluids with water. The MWCNT-water nanofluids were prepared by two step method at the volume concentrations of 0.2%, 0.4%, and 0.6%. The range of target fluid mass-flow rate is in the range of 0.026 to 0.039 kg per second and the constant heat flux condition is considered. On experimentation, it is noted that the effectiveness and presure drop of 0.6% MWCNT-water based nanofluids are 27% and 21% greater than water at the maximum mass-flow rate. The reason for improved heat transfer rate of nanofluids is because of higher thermal conductivity, Brownian motion, lower boundary-layer thickness, and lower specific heat capacity of nanofluids. Also found that the pumping power increases with increasing volume concentration and pumping power is 25% higher than water at the 0.6% nanofluids. Therefore, the MWCNT-water nanofluids are good choice for replacing water as coolant in triple concentric tube heat exchanger.

Enhancement of thermal conductivity and thermal stability of capric-lauric acid eutectic phase change material using carbonaceous materials

This paper investigates the effect of adding carbon based nano additives viz., graphene oxide (GO), multi-walled carbon nanotubes (MWCNT) and activated carbon (AC) to capric-lauric acid (CA-LA) eutectic phase change material (PCM) in order to prepare nanoenhanced PCMs (NEPCMs). Field emission scanning electron microscopy images showed that GO has a sheet, MWCNT has a tube, and AC has a sheet with porous like structures, which influence the shape stability of eutectic PCM. The CA-LA has melting and solidification temperature at 18.92 °C and 18.30 °C, corresponding latent heat values were 107.9 J g−1 and 106.8 J g−1 analyzed by differential scanning calorimetry. The addition of carbonaceous materials shows a slight decrease in the latent heat values for NEPCMs which is quashed by its improved heat transfer rate. Thermal stability of NEPCMs were studied by thermogravimetric analysis. As-prepared carbonaceous materials had excellent thermo-physical properties in that MWCNT has higher thermal conductivity compared to GO and AC due to it light weight. Therefore, NEPCMs has acceptable thermal properties which are suitable for cold thermal energy storage.

Optimal Start-up Policies for a Nanofluid-Based Solar Thermal Power Plant

Parabolic trough solar thermal power plants use a fluid to transfer thermal energy from captured solar radiation to a Rankine cycle to drive a turbine that, coupled to an electrical generator, produces electricity. Continuous improvement on their performance will lead these technologies to truly compete with either conventional or other forms of renewable energy systems. Nanofluids have been proposed as a way to improve heat transfer rates in thermal solar plants. Hence, nanofluid thermal solar plants coupled to dynamic optimal operating policies should render improved heat transfer characteristics as well as power production. The main objective of this work is to obtain optimal start-up policies of such plants using diverse nanofluids (Al2O3-water and TiO2-water) compared against pure water as base fluid, focused on power delivery and the time required for the system to reach target conditions. For the analysis, the deterministic dynamic mathematical model of a previously proposed solar thermal power fac...

Laminar flow heat transfer enhancement in square and rectangular channels having: (1) A wire-coil, axial and spiral corrugation combined with helical screw-tape with and without oblique teeth and a (2) spiral corrugation combined with twisted tapes with oblique teeth

Heat transfer enhancement is a vital area of research as it helps to design heat exchangers of reduced sizes and improved heat transfer rates. Thus, there is a pressing need for techniques which result in significantly increased heat transfer over and above increased pressure drop. In this paper, the benefits of different compound techniques using (1) wire-coil inserts and helical screw-tape inserts with oblique teeth, (2) wire-coil inserts and helical screw-tape inserts without oblique teeth, (3) spiral corrugation and helical screw-tape inserts without oblique teeth, (4) axial corrugation and helical screw-tape inserts without oblique teeth, and (5) spiral corrugation and twisted-tape inserts with oblique teeth were studied experimentally for laminar flow in a non-circular duct (aspect ratio = 1, 0.5 and 0.33). Servotherm medium oil with Prandtl number ranging from 430 to 530 was used as working fluid. The experiment was conducted for a uniform heat flux boundary condition. The effect of geometric parameters of the inserts such as wire-coil diameter, wire-coil helix angle, tooth angle and tooth horizontal length of the screw tape and the twisted tape, corrugation height and corrugation pitch, etc. on heat transfer and pressure drop characteristics was presented. The influence of duct geometry (aspect ratio) on Nusselt number and friction factor was also studied. Correlations for Nusselt number and friction factor were developed and a performance evaluation was done.