scholarly journals Investigation of heat transfer enhancement in an annular conduit with angled fins using functionalized GNP colloidal suspension

2021 ◽  
Vol 945 (1) ◽  
pp. 012058
Author(s):  
Sayshar Ram Nair ◽  
Cheen Sean Oon ◽  
Ming Kwang Tan ◽  
S.N. Kazi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Colloidal Suspension ◽  
Industrial Applications ◽  
Point Of View ◽  
Solid Particles ◽  
Working Fluid

Abstract Heat exchangers are important equipment with various industrial applications such as power plants, HVAC industry and chemical industries. Various fluids that are used as working fluid in the heat exchangers such as water, oil, and ethylene glycol. Researchers have conducted various studies and investigations to improve the heat exchanger be it from material or heat transfer point of view. There have been attempts to create mixtures with solid particles suspended. This invention had some drawbacks since the pressure drop was compromised, on top of the occurrence of sedimentation or even erosion, which incurs higher maintenance costs. A new class of colloidal suspension fluid that met the demands and characteristics of a heat exchanger was then created. This novel colloidal suspension mixture was then and now addressed as “nanofluid”. In this study, the usage of functionalized graphene nanoplatelet (GNP) nanofluids will be studied for its thermal conductivity within an annular conduit with angled fins, which encourage swirling flows. The simulation results for the chosen GNP nanofluid concentrations have shown an enhancement in thermal conductivity and heat transfer coefficient compared to the corresponding base fluid thermal properties. The data from this research is useful in industrial applications which involve heat exchangers with finned tubes.

scholarly journals Modelling of Polymeric Shell and Tube Heat Exchangers for Low-Medium Temperature Geothermal Applications

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2737
Author(s):  
Francesca Ceglia ◽  
Adriano Macaluso ◽  
Elisa Marrasso ◽  
Maurizio Sasso ◽  
Laura Vanoli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Heat Transfer Area ◽  
Geothermal Fluid ◽  
Shell And Tube

Improvements in using geothermal sources can be attained through the installation of power plants taking advantage of low and medium enthalpy available in poorly exploited geothermal sites. Geothermal fluids at medium and low temperature could be considered to feed binary cycle power plants using organic fluids for electricity “production” or in cogeneration configuration. The improvement in the use of geothermal aquifers at low-medium enthalpy in small deep sites favours the reduction of drilling well costs, and in addition, it allows the exploitation of local resources in the energy districts. The heat exchanger evaporator enables the thermal heat exchange between the working fluid (which is commonly an organic fluid for an Organic Rankine Cycle) and the geothermal fluid (supplied by the aquifer). Thus, it has to be realised taking into account the thermodynamic proprieties and chemical composition of the geothermal field. The geothermal fluid is typically very aggressive, and it leads to the corrosion of steel traditionally used in the heat exchangers. This paper analyses the possibility of using plastic material in the constructions of the evaporator installed in an Organic Rankine Cycle plant in order to overcome the problems of corrosion and the increase of heat exchanger thermal resistance due to the fouling effect. A comparison among heat exchangers made of commonly used materials, such as carbon, steel, and titanium, with alternative polymeric materials has been carried out. This analysis has been built in a mathematical approach using the correlation referred to in the literature about heat transfer in single-phase and two-phase fluids in a tube and/or in the shell side. The outcomes provide the heat transfer area for the shell and tube heat exchanger with a fixed thermal power size. The results have demonstrated that the plastic evaporator shows an increase of 47.0% of the heat transfer area but an economic installation cost saving of 48.0% over the titanium evaporator.

scholarly journals Execution of a Smart Prediction Tool to Evaluate Thermal Performance in a heat exchanger by using Single Elliptical Leaf Strips with altered Angle

2019 ◽  
Vol 8 (11) ◽  
pp. 123-131
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Industrial Applications ◽  
Generalized Regression Neural Network ◽  
Prediction Tool ◽  
Pressure Drops ◽  
Transfer Rates ◽  
Mass Flow Rates

Heat exchangers are prominent industrial applications where engineering science of heat transfer and Mass transfer occurs. It is a contrivance where transfer of energy occurs to get output in the form of energy transfer. This paper aims at finding a solution to improve the thermal performance in a heat exchanger by using passive method techniques. This experimental and numerical analysis deals with finding the temperature outlets of cold and hot fluid for different mass flow rates and also pressure drop in the tube and the annular side by adding an elliptical leaf strip in the pipe at various angles. The single elliptical leaf used in experiment has major to minor axes ratios as 2:1 and distance of 50 mm between two leaves are arranged at different angular orientations from 0 0 to 1800 with 100 intervals. Since it’s not possible to find the heat transfer rates and pressure drops at every orientation of elliptical leaf so a generalized regression neural network (GRNN) prediction tool is used to get outputs with given inputs to avoid experimentation. GRNN is a statistical method of determining the relationship between dependent and independent variables. The values obtained from experimentation and GRNN nearly had precise values to each other. This analysis is a small step in regard with encomiastic approach for enhancement in performance of heat exchangers

scholarly journals Implicit Finite Difference Simulation of Prandtl-Eyring Nanofluid over a Flat Plate with Variable Thermal Conductivity: A Tiwari and Das Model

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3153
Author(s):  
Nidal H. Abu-Hamdeh ◽  
Abdulmalik A. Aljinaidi ◽  
Mohamed A. Eltaher ◽  
Khalid H. Almitani ◽  
Khaled A. Alnefaie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Finite Difference ◽  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Variable Thermal Conductivity ◽  
Solid Particles ◽  
Engine Oil ◽  
Working Fluid ◽  
Implicit Finite Difference

The current article presents the entropy formation and heat transfer of the steady Prandtl-Eyring nanofluids (P-ENF). Heat transfer and flow of P-ENF are analyzed when nanofluid is passed to the hot and slippery surface. The study also investigates the effects of radiative heat flux, variable thermal conductivity, the material’s porosity, and the morphologies of nano-solid particles. Flow equations are defined utilizing partial differential equations (PDEs). Necessary transformations are employed to convert the formulae into ordinary differential equations. The implicit finite difference method (I-FDM) is used to find approximate solutions to ordinary differential equations. Two types of nano-solid particles, aluminium oxide (Al2O3) and copper (Cu), are examined using engine oil (EO) as working fluid. Graphical plots are used to depict the crucial outcomes regarding drag force, entropy measurement, temperature, Nusselt number, and flow. According to the study, there is a solid and aggressive increase in the heat transfer rate of P-ENF Cu-EO than Al2O3-EO. An increment in the size of nanoparticles resulted in enhancing the entropy of the model. The Prandtl-Eyring parameter and modified radiative flow show the same impact on the radiative field.

Binary Particle Mixtures as a Heat Transfer Media in Shell-and-Plate Moving Packed Bed Heat Exchangers

2021 ◽  
Author(s):  
Chase Ellsworth Christen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Packed Bed ◽  
Particle Sizes ◽  
Overall Heat Transfer Coefficient ◽  
Solid Media

Solid particles are being considered in several high temperature thermal energy storage systems and as heat transfer media in concentrated solar power (CSP) plants. The downside of such an approach is the low overall heat transfer coefficients in shell-and-plate moving packed bed heat exchangers caused by the inherently low packed bed thermal conductivity values of the low-cost solid media. Choosing the right particle size distribution of currently available solid media can make a substantial difference in packed bed thermal conductivity, and thus, a substantial difference in the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers. Current research exclusively focuses on continuous unimodal distributions of alumina particles. The drawback of this approach is that larger particle sizes require wider particle channels to meet flowability requirements. As a result, only small particle sizes with low packed bed thermal conductivities have been considered for the use in the falling-particle Gen3 CSP concepts. Here, binary particle mixtures, which are defined in this thesis as a mixture of two continuous unimodal particle distributions leading to a continuous bimodal particle distribution, are considered to increase packed bed thermal conductivity, decrease packed bed porosity, and improve moving packed bed heat exchanger performance. This is the first study related to CSP solid particle heat transfer that has considered the packed bed thermal conductivity and moving packed bed heat exchanger performance of bimodal particle size distributions at room and elevated temperatures. Considering binary particle mixtures that meet particle sifting segregation criteria, the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers can be increased by 23% when compared to a monodisperse particle system. This work demonstrates that binary particle mixtures should be seriously considered to improve shell-and-plate moving packed bed heat exchangers.

scholarly journals OTEC Maximum Net Power Output Using Carnot Cycle and Application to Simplify Heat Exchanger Selection

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1143 ◽  
Author(s):  
Kevin Fontaine ◽  
Takeshi Yasunaga ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Power Output ◽  
Heat Exchangers ◽  
Power Plants ◽  
Seawater Temperature ◽  
Carnot Cycle ◽  
Ocean Thermal Energy ◽  
Net Power Output

Ocean thermal energy conversion (OTEC) uses the natural thermal gradient in the sea. It has been investigated to make it competitive with conventional power plants, as it has huge potential and can produce energy steadily throughout the year. This has been done mostly by focusing on improving cycle performances or central elements of OTEC, such as heat exchangers. It is difficult to choose a suitable heat exchanger for OTEC with the separate evaluations of the heat transfer coefficient and pressure drop that are usually found in the literature. Accordingly, this paper presents a method to evaluate heat exchangers for OTEC. On the basis of finite-time thermodynamics, the maximum net power output for different heat exchangers using both heat transfer performance and pressure drop was assessed and compared. This method was successfully applied to three heat exchangers. The most suitable heat exchanger was found to lead to a maximum net power output 158% higher than the output of the least suitable heat exchanger. For a difference of 3.7% in the net power output, a difference of 22% in the Reynolds numbers was found. Therefore, those numbers also play a significant role in the choice of heat exchangers as they affect the pumping power required for seawater flowing. A sensitivity analysis showed that seawater temperature does not affect the choice of heat exchangers, even though the net power output was found to decrease by up to 10% with every temperature difference drop of 1 °C.

Numerical Investigation of Heat Transfer and Condensation Rate in Two-Stage Transport Membrane Condenser Heat Exchanger Units

2016 ◽  
Author(s):  
Soheil Soleimanikutanaei ◽  
Cheng-Xian Lin ◽  
Dexin Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Work Performance ◽  
Transport Model ◽  
Flow Direction ◽  
Industrial Applications ◽  
Water Recovery ◽  
Condensation Rate ◽  
Two Stage

Heat and water recovery using Transport Membrane Condenser (TMC) based heat exchangers is a promising technology in power generation industry. In this type of innovative heat exchangers the tube walls are made of a nano-porous material and have a high membrane selectivity which is able to extract condensate water from the flue gas in the presence of the other non-condensable gases such as CO2, O2 and N2. Considering the fact that for industrial applications, a matrix of TMC heat exchangers with several TMC modulus in the cross section or along the flow direction is necessary. Numerical simulation of multi-stage TMC heat exchanger units is of a great importance in terms of design, performance evaluation and optimization. In this work, performance of a two-stage TMC heat exchanger unit has been studied numerically using a multi-species transport model. In order to investigate the performance of the two-stage TMC heat exchanger unit, parametric study on the effect of transversal and longitudinal pitches in terms of heat transfer, pressure drop and condensation rate inside the heat exchangers have been carried out. The results indicate that the heat transfer and condensation rates both increase by reducing TMC tube pitches in the second stage and increasing the number of TMC tube pitches in the first stage of the units.

Novel Evaporator Geometries Based on Entrance-Length Flow-Paths for Geothermal Binary Power Plants

2016 ◽  
Author(s):  
Adrian S. Sabau ◽  
Ali H. Nejad ◽  
James W. Klett ◽  
Adrian Bejan ◽  
Kivanc Ekici
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Cost Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Length Scale ◽  
Entrance Length ◽  
Scale Levels

In this paper, a novel geometry is proposed for evaporators that are used in Organic Rankine Cycles. The proposed geometry consists of employing successive plenums at several length-scale levels, creating a multi-scale heat exchanger. The channels at the lowest length-scale levels were considered to have their length given by the thermal entrance-length. Numerical simulations based on turbulent flow correlations for supercritical R134a and water were used to obtain performance indicators for new heat exchangers and baseline heat exchangers. The relationship between the size of the channels at one level, k, with respect to the size of the channels at the next level, k + 1, is based on generalization of the “Murray’s law.” In order to account for the variation of the temperature and heat transfer coefficient in the entrance region, a heat transfer model was developed. The variation of the brine and refrigerant temperatures along each pipe was considered. Using the data on pumping power and weight of metal structures, including that of all the plenums and piping, the total present cost was evaluated using a cost model for shell-and-tube heat exchangers. In addition to the total present cost, the data on overall thermal resistance is also used in identifying optimal heat exchanger configurations. The main design variables include: tube arrangement, number of channels fed from plenum, and number of rows in the tube bank seen by the outside fluid. In order to assess the potential improvement of the new evaporator designs, baseline evaporators were designed. The baseline evaporator designs include long tubes of the same diameter as those of the lowest length-scale levels, placed between one inlet and one outlet. The baseline evaporator designs were created from the new evaporator designs by simply removing most of the internal plenums employing tubes much longer than their entrance length, as they would currently be used. Consistent with geothermal applications, the performance of new heat exchanger designs was compared to that of baseline heat exchanger designs at the same flow rates. For some operating conditions it was found that the new heat exchangers outperform their corresponding baseline heat exchangers.

scholarly journals Performance Analysis of Shell and Tube Type Heat Exchanger Using Aluminium Oxide (Al2O3) Nano-Particle

2021 ◽  
Vol 9 (9) ◽  
pp. 157-164
Author(s):  
Paritosh Singh
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Solid Particles ◽  
Tube Heat Exchanger ◽  
Overall Heat Transfer Coefficient ◽  
Shell And Tube ◽  
Evacuated Tube

Abstract: Research in convective heat transfer using suspensions of nanometer sized solid particles in a base fluid started only over the past decade. Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension. The very first part of the research work summarizes about the various thermo physical properties of Al2O3 Nanofluid. In evacuated tube solar water heating system nanofluids are used as primary fluid and DM water as secondary fluid in Shell and Tube Heat Exchanger. The experimental analysis of Shell and Tube heat exchanger integrated with Evacuated tube solar collector have been carried out with two types of primary fluids. Research study of shell and tube heat exchanger is focused on heat transfer enhancement by usage of nano fluids. Conventional heat transfer fluids have inherently low thermal conductivity that greatly limits the heat exchange efficiency. The result of analysis shows that average relative variation in LMTD and overall heat transfer coefficient is 24.56% and 52.0% respectively. The payback period of system is reduced by 0.4 years due to saving is in replacement cost of Evacuated Tube Collector. Keywords: ETC; Nanofluid; LMTD; Thermal Conductivity; Overall heat transfer coefficient

Development and Application of a Plugging Margin Evaluation Method Taking Into Account the Fouling of Shell-and-Tube Heat Exchangers

2005 ◽  
Author(s):  
Kyeong Mo Hwang ◽  
Tae Eun Jin
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Nuclear Power ◽  
Power Plants ◽  
Evaluation Method ◽  
Operating Time ◽  
Flow Characteristics ◽  
Shell And Tube

As the operating time of heat exchangers progresses, fouling caused by water-borne deposits and the number of plugged tubes increase and thermal performance decreases. Both fouling and tube plugging are known to interfere with normal flow characteristics and to reduce thermal efficiencies of heat exchangers. The heat exchangers of Korean nuclear power plants have been analyzed in terms of heat transfer rate and overall heat transfer coefficient as a means of heat exchanger management. Except for fouling resulting from the operation of heat exchangers, all the tubes of heat exchangers have been replaced when the number of plugged tubes exceeded the plugging criteria based on design performance sheet. This paper describes a plugging margin evaluation method taking into account the fouling of shell-and-tube heat exchangers. The method can evaluate thermal performance, estimate future fouling variation, and consider current fouling level in the calculation of plugging margin. To identify the effectiveness of the developed method, fouling and plugging margin evaluations were performed at a component cooling heat exchanger in a Korean nuclear power plant.

A Review on Nanofluid Heat Pipe

2014 ◽  
Author(s):  
Maryam Shafahi ◽  
Kevin Anderson ◽  
Ali Borna ◽  
Michael Lee ◽  
Alex Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Working Fluid ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Medical Instruments ◽  
Thermo Physical Properties

This paper reviews the improvement in the heat pipe’s performance using nanofluid as the working fluid. The use of nanofluid enhances heat transfer in the heat pipe due to its improved thermo-physical properties, such as a higher thermal conductivity. Nanofluids proved to be the innovative approach to a variety of applications, such as electronics, medical instruments, and heat exchangers. The influence of different nanoparticles on heat pipe’s performance has been studied. Utilizing nanofluid as the working fluid leads to a significant reduction in heat pipe thermal resistance, an increase in maximum heat transfer, and an improvement of heat pipe thermal performance.

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