The Experts below are selected from a list of 93831 Experts worldwide ranked by ideXlab platform
M Bohnet - One of the best experts on this subject based on the ideXlab platform.
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influence of the transport properties of the crystal Heat Transfer Surface interfacial on fouling behavior
Chemical Engineering & Technology, 2003Co-Authors: M BohnetAbstract:One method to reduce fouling is to extend the induction time by a defined modification of the interfacial interactions between the Heat Transfer Surface and the crystalline deposit. Since these interactions are a result of both molecular and mechanical forces, two approaches for fouling mitigation have been developed: (a) Modification of the energy related properties of the Heat Transfer Surface and (b) Modification of the geometry related properties of the Heat Transfer Surface.
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modification of molecular interactions at the interface crystal Heat Transfer Surface to minimize Heat exchanger fouling
International Journal of Thermal Sciences, 2000Co-Authors: Markus Forster, M BohnetAbstract:Abstract Recent studies with respect to mitigate Heat exchanger fouling spend only minor attention to the possibility of modifying molecular interactions at the interface between Heat Transfer Surface (substrate) and adjacent crystalline deposit (adhesive). New anti-fouling strategies deal with a defined modification of these interactions to reduce the corresponding adhesive strength favouring the removal process due to the wall shear stress. By means of drop shape analysis the interfacial free energy adhesive/substrate has been determined. On the basis of numerous fouling experiments the interfacial defect model has been identified to serve as a tool to estimate the optimal choice of Surface material. For the description of the influence of interfacial energies between two materials on adhesion both van der Waals and hydrophobic interactions making allowance for the presence of polar media have been analyzed. The geometric and harmonic mean approach (van der Waals forces only) is chosen for the description of metallic Surfaces. For polymeric materials where repulsive interactions have to be taken into account, the Lewis acid–base approach (also considering hydrophobic interactions) is favoured.
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influence of the interfacial free energy crystal Heat Transfer Surface on the induction period during fouling
International Journal of Thermal Sciences, 1999Co-Authors: Markus Forster, M BohnetAbstract:Abstract The accumulation of unwanted crystalline deposits (fouling) reduces the efficiency of Heat exchangers. In order to adjust the operating conditions with respect to fouling mitigation a model for the description of the entire fouling process has to be established. The main disadvantage of known models is the lack of a description of the induction period which is influenced by the nucleation rate and the adhesive strength between crystals and Heat Transfer Surfaces. The deposition and removal process depends on the interfacial free energy crystal/Heat Transfer Surface. For many industrial applications the only possibility to influence the interfacial free energy is to modify the Surface energy characteristics of the Heat Transfer Surface, i.e. its Surface free energy. Based on the experimental investigation of the Surface energy of several metallic and low energy materials their fouling performance when exposed to a liquid flow of a calcium sulphate solution was evaluated. The deployment of new Surface materials such as DLC (diamond like carbon) coatings proved to be a strategy to increase the induction period.
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influence of the adhesion force crystal Heat exchanger Surface on fouling mitigation
Chemical Engineering and Processing, 1999Co-Authors: Markus Forster, W Augustin, M BohnetAbstract:The accumulation of unwanted crystalline deposits (fouling) reduces the efficiency of Heat exchangers considerably. In order to decrease the cost of fouling two strategies have been developed. The first fouling mitigation strategy is based on the modification of energy and geometry related characteristics of the Heat Transfer Surface to realize an increased duration of the induction period. By means of a DSA (drop shape analysis) measurement device the interaction at the interface crystal/Heat Transfer Surface is determined. The deployment of the fracture energy model and the interfacial defect model relates wetting characteristics to the adhesion phenomenon. Hence, a first estimation of the optimal choice of Surface material is realized. Furthermore, the influence of Surface topography on interfacial interactions has been analyzed. The second fouling mitigation strategy is based on the adjustment of the hydrodynamic flow conditions using a pulsation technique. Here, single strokes of higher velocity are superimposed on the stationary flow. These strokes shift the equilibrium of forces to an improved removal process. Fouling experiments have proved that pulsation is a powerful tool to mitigate the built-up of fouling layers on Heat Transfer Surfaces.
Mohamed El Habib Amagour - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation and comparative performance analysis of a compact finned tube Heat exchanger uniformly filled with a phase change material for thermal energy storage
Energy Conversion and Management, 2018Co-Authors: Mohamed El Habib Amagour, Adil Rachek, Mounir Bennajah, Mohamed Ebn TouhamiAbstract:Abstract In the present paper, a latent Heat storage system using a Heat-Transfer enhancement technique has been built and tested. The potential of using a natural phase change material of Moroccan provenance for energy storage was studied by experimental analysis. The enhanced Heat Transfer Surface of the compact finned-tube Heat exchanger presents geometric complications. Therefore, a new method based on equivalent circular fin efficiency for the calculation of the effective Heat Transfer Surface area was developed and applied to the system under study. In order to carry out the performance analysis for this innovative system, charging and discharging experiments were conducted for different Heat Transfer fluid flow rates. It was found that increasing the flow rate from 0.2 to 1 l/min divides melting time by 2.5 and solidification time by four. The average effectiveness was calculated for each flow rate and was proven to decrease during charging from 0.95 for a flow rate of 0.2 l/min to 0.63 for 1 l/min. Likewise, increasing flow rate from 0.2 to 1 l/min for discharging process decreases Heat exchanger effectiveness from 0.99 to 0.7. The combination of the effectiveness-number of Transfer units method with the procedure that was developed to compute the effective Heat Transfer area lead to derive an empirical correlation. This equation was used to compare the finned-tube compact storage system with other Heat and cold storage units. The comparison showed that the present system displayed satisfactory results. The second use of the correlation was to design, through a case study, a Heat storage system suitable for solar domestic hot water production in a residential building.
Zahid H Ayub - One of the best experts on this subject based on the ideXlab platform.
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geometric optimization for thermal hydraulic performance of dimpled enhanced tubes for single phase flow
Applied Thermal Engineering, 2016Co-Authors: Tariq S Khan, Ebrahim Al Hajri, Zahid H AyubAbstract:Abstract Enhanced Surfaces have larger Heat Transfer Surface area and offer increased turbulence level hence allowing higher Heat exchange performance. In this study, numerical simulations are conducted to simulate geometric design optimization of enhanced tubes for optimal thermal–hydraulic performance. The simulations are validated with experimental data. Two and three dimensional steady incompressible turbulent flow in dimpled enhanced tube is numerically studied using realizable k – e method. The pressure–velocity coupling is solved by Semi-Implicit Method for Pressure Linked Equations Consistent (SIMPLEC) algorithm. Results show that dimples on tube Surface present high Heat Transfer performance. Compared to staggered configuration, the in-line dimples arrangement provided better overall Heat exchange characteristics. The geometric parameters like dimple shape, depth, pitch and starts are found to have significant effects on overall Heat exchange performance while the dimple diameter has insignificant effect on thermal performance.
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experimental investigation of single phase convective Heat Transfer coefficient in a corrugated plate Heat exchanger for multiple plate configurations
Applied Thermal Engineering, 2010Co-Authors: Tariq S Khan, Mohammad S Khan, Mingc Chyu, Zahid H AyubAbstract:Corrugated plate Heat exchangers have larger Heat Transfer Surface area and increased turbulence level due to the corrugations. In this study, experimental Heat Transfer data are obtained for single phase flow (water-to-water) configurations in a commercial plate Heat exchanger for symmetric 30°/30°, 60°/60°, and mixed 30°/60° chevron angle plates. Experiments were carried out for Reynolds number ranging from 500 to 2500 and Prandtl number from 3.5 to 6.5. Experimental results show significant effect of chevron angle and Reynolds number on the Heat Transfer coefficient. Based on the experimental data, a correlation to estimate Nusselt number as a function of Reynolds number, Prandtl number and chevron angle has been proposed.
Markus Forster - One of the best experts on this subject based on the ideXlab platform.
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modification of molecular interactions at the interface crystal Heat Transfer Surface to minimize Heat exchanger fouling
International Journal of Thermal Sciences, 2000Co-Authors: Markus Forster, M BohnetAbstract:Abstract Recent studies with respect to mitigate Heat exchanger fouling spend only minor attention to the possibility of modifying molecular interactions at the interface between Heat Transfer Surface (substrate) and adjacent crystalline deposit (adhesive). New anti-fouling strategies deal with a defined modification of these interactions to reduce the corresponding adhesive strength favouring the removal process due to the wall shear stress. By means of drop shape analysis the interfacial free energy adhesive/substrate has been determined. On the basis of numerous fouling experiments the interfacial defect model has been identified to serve as a tool to estimate the optimal choice of Surface material. For the description of the influence of interfacial energies between two materials on adhesion both van der Waals and hydrophobic interactions making allowance for the presence of polar media have been analyzed. The geometric and harmonic mean approach (van der Waals forces only) is chosen for the description of metallic Surfaces. For polymeric materials where repulsive interactions have to be taken into account, the Lewis acid–base approach (also considering hydrophobic interactions) is favoured.
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influence of the interfacial free energy crystal Heat Transfer Surface on the induction period during fouling
International Journal of Thermal Sciences, 1999Co-Authors: Markus Forster, M BohnetAbstract:Abstract The accumulation of unwanted crystalline deposits (fouling) reduces the efficiency of Heat exchangers. In order to adjust the operating conditions with respect to fouling mitigation a model for the description of the entire fouling process has to be established. The main disadvantage of known models is the lack of a description of the induction period which is influenced by the nucleation rate and the adhesive strength between crystals and Heat Transfer Surfaces. The deposition and removal process depends on the interfacial free energy crystal/Heat Transfer Surface. For many industrial applications the only possibility to influence the interfacial free energy is to modify the Surface energy characteristics of the Heat Transfer Surface, i.e. its Surface free energy. Based on the experimental investigation of the Surface energy of several metallic and low energy materials their fouling performance when exposed to a liquid flow of a calcium sulphate solution was evaluated. The deployment of new Surface materials such as DLC (diamond like carbon) coatings proved to be a strategy to increase the induction period.
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influence of the adhesion force crystal Heat exchanger Surface on fouling mitigation
Chemical Engineering and Processing, 1999Co-Authors: Markus Forster, W Augustin, M BohnetAbstract:The accumulation of unwanted crystalline deposits (fouling) reduces the efficiency of Heat exchangers considerably. In order to decrease the cost of fouling two strategies have been developed. The first fouling mitigation strategy is based on the modification of energy and geometry related characteristics of the Heat Transfer Surface to realize an increased duration of the induction period. By means of a DSA (drop shape analysis) measurement device the interaction at the interface crystal/Heat Transfer Surface is determined. The deployment of the fracture energy model and the interfacial defect model relates wetting characteristics to the adhesion phenomenon. Hence, a first estimation of the optimal choice of Surface material is realized. Furthermore, the influence of Surface topography on interfacial interactions has been analyzed. The second fouling mitigation strategy is based on the adjustment of the hydrodynamic flow conditions using a pulsation technique. Here, single strokes of higher velocity are superimposed on the stationary flow. These strokes shift the equilibrium of forces to an improved removal process. Fouling experiments have proved that pulsation is a powerful tool to mitigate the built-up of fouling layers on Heat Transfer Surfaces.
Fengrui Sun - One of the best experts on this subject based on the ideXlab platform.
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Heat Transfer Surface area optimization for a thermoelectric generator
International Journal of Ambient Energy, 2007Co-Authors: Lingen Chen, Fengrui SunAbstract:SYNOPSIS The combination of finite time thermodynamics and non-equilibrium thermodynamics is applied to analyse and optimise the performance of a thermoelectric generator, which is composed of multi-elements. For the fixed total Heat Transfer Surface area of two Heat exchangers, the ratio of Heat Transfer Surface area of the high temperature side Heat exchanger to the total Heat Transfer Surface area of the Heat exchangers is optimised for maximising the power output and the thermal efficiency of the thermoelectric generator. The effects of various parameters on the optimum performance are analysed. The results may provide guidelines for the analysis and optimisation of practical thermoelectric generators.
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performance optimization of a two stage semiconductor thermoelectric generator
Applied Energy, 2005Co-Authors: Lingen Chen, Fengrui SunAbstract:A model of a two-stage semiconductor thermoelectric-generator with external Heat-Transfer is built. Performance of the generator, assuming Newton's Heat-Transfer law applies, is analyzed using a combination of finite-time thermodynamics and non-equilibrium thermodynamics. The analytical equations about the power output versus the working electrical current, and the thermal efficiency versus working electrical-current are derived. For a fixed total Heat-Transfer Surface-area for two Heat-exchangers, the ratio of Heat-Transfer Surface-area of the high-temperature side Heat-exchanger to the total Heat-Transfer Surface-area of the Heat-exchangers is optimized for maximizing the power output and the thermal efficiency of the thermoelectric-generator. For a fixed total number of thermoelectric elements, the ratio of number of thermoelectric elements of the top stage to the total number of thermoelectric elements is also optimized for maximizing both the power output and the thermal efficiency of the thermoelectric-generator. The effects of design factors on the performance are analyzed.
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optimum allocation of Heat Transfer Surface area for cooling load and cop optimization of a thermoelectric refrigerator
Energy Conversion and Management, 2003Co-Authors: Jun Luo, Lingen Chen, Fengrui SunAbstract:The theory of finite time thermodynamics is applied to analyze and optimize the performance of a thermoelectric refrigerator, which is composed of multi-elements. For the fixed total Heat Transfer Surface area of two Heat exchangers, the ratio of the Heat Transfer Surface area of the high temperature side Heat exchanger to the total Heat Transfer Surface area of the Heat exchangers is optimized for maximizing the cooling load and the coefficient of performance of the thermoelectric refrigerator. The effects of various parameters on the optimum performance are analyzed. The results may provide guides for the analysis and optimization of practical thermoelectric refrigerators.
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performance analysis for a real closed regenerated brayton cycle via methods of finite time thermodynamics
International journal of ambient energy, 1999Co-Authors: Lingen Chen, Gang Cheng, Fengrui SunAbstract:SYNOPSIS Performance analysis of a real power cycle has been performed using finite-time thermodynamics. The analytical formulae about the relations between power output and pressure ratio, and between efficiency and pressure ratio of a real closed regenerated Brayton cycle coupled to variable-temperature Heat reservoirs are derived. In the analysis, the irreversibilities involve the Heat resistance losses in the hot- and cold-side Heat exchangers and the regenerator, the irreversible (non-isentropic) expansion and compression losses in the turbine and compressor, and the pressure drop loss in the pipe and system. The optimal performance characteristics of the cycle may be obtained by optimising the distribution of Heat conductance or Heat-Transfer Surface areas among two Heat exchangers and regenerator, and the matching between working fluid and Heat reservoirs. For the specified Heat reservoir conditions, the power output is dependent on the effectiveness of the regenerator, and there exists an optimal ...
