scholarly journals Influence of bismuth additives on the thermophysical and thermodynamic properties of aluminum conductive alloy E-AlMgSi (Aldrey)

2020 ◽  
Vol 23 (1) ◽  
pp. 86-93
Author(s):  
I. N. Ganiev ◽  
A. P. Abdulakov ◽  
J. H. Jayloev ◽  
U. Sh. Yakubov ◽  
A. G. Safarov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Aluminum Alloys ◽  
Gibbs Energy ◽  
Transfer Coefficient ◽  
Thermodynamic Functions ◽  
Economic Feasibility ◽  
Conductive Material ◽  
The Cost

The economic feasibility of using aluminum as a conductive material is explained by the favorable ratio of its cost to the cost of copper. It is also important that the cost of aluminum for many years remains virtually unchanged.When using conductive aluminum alloys for the manufacture of thin wire, winding wire, etc. Certain difficulties may arise in connection with their insufficient strength and a small number of kinks before fracture. In recent years, aluminum alloys have been developed, which even in a soft state have strength characteristics that allow them to be used as a conductive material.One of the promising areas for the use of aluminum is the electrical industry. Conducting aluminum alloys of the E-AlMgSi type (Aldrey) are representatives of this group of alloys. The paper presents the results of a study of the temperature dependence of heat capacity, heat transfer coefficient, and thermodynamic functions of an aluminum alloy E-AlMgSi (Aldrey) with bismuth. Research conducted in the "cooling" mode.It was shown that the temperature capacity and the thermodynamic functions of the alloy E-AlMgSi (Aldrey) with bismuth increase with temperature, and the Gibbs energy decreases. Additives of bismuth up to 1 wt.% Reduce heat capacity, heat transfer coefficient, enthalpy and entropy of the initial alloy and increase the value of Gibbs energy.

scholarly journals Effect of bismuth additions on the thermophysical and thermodynamical properties of E-AlMgSi (Aldrey) aluminum semiconductor alloy

2020 ◽  
Vol 6 (3) ◽  
pp. 107-112
Author(s):  
Izatullo N. Ganiev ◽  
Aslam P. Abulakov ◽  
Jamshed H. Jayloev ◽  
Umarali Sh. Yakubov ◽  
Amirsho G. Safarov ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Gibbs Energy ◽  
Thermodynamic Functions ◽  
Heat Conductivity ◽  
Economic Feasibility ◽  
Cooling Mode ◽  
Conductive Material ◽  
The Cost

The economic feasibility of using aluminum as a conductive material is explained by the favorable ratio of its cost to the cost of copper. In addition, one should take into account that the cost of aluminum has remained virtually unchanged for many years. When using conductive aluminum alloys for the manufacture of thin wire, winding wire, etc., certain difficulties may arise in connection with their insufficient strength and a small number of kinks before fracture. Aluminum alloys have been developed in recent years which even in a soft state have strength characteristics that allow them to be used as a conductive material. The electrochemical industry is one of the promising application fields of aluminum. E-AlMgSi (Aldrey) conductor aluminum alloys represent this group of alloys. This work presents data on the temperature dependence of heat capacity, heat conductivity and thermodynamic functions of the E-AlMgSi (Aldrey) aluminum alloy doped with bismuth. The studies have been carried out in "cooling" mode. It has been shown that the heat capacity and thermodynamic functions of the E-AlMgSi (Aldrey) aluminum alloy doped with bismuth increase with temperature and the Gibbs energy decreases. Bismuth additions of up to 1 wt.% reduce the heat capacity, heat conductivity, enthalpy and entropy of the initial alloy and increase the Gibbs energy.

Efficiency Centered Maintenance of Preheat Train of a Crude Oil Distillation Unit

2020 ◽  
Author(s):  
J. Fajardo ◽  
D. Yabrudy ◽  
D. Barreto ◽  
C. Negrete ◽  
B. Sarria ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Operational Reliability ◽  
Distillation Unit ◽  
Maintenance Costs ◽  
Oil Refineries ◽  
The Cost

Abstract Nowadays, maintenance is based on the synergistic integration of operational reliability and timely maintenance, which guarantees the required availability and optimal cost. Operational reliability implies producing more, better performance, longer life, and availability. Timely maintenance involves the least time out of service, fewer maintenance costs, fewer operating costs, and less money. In this work, we study the preheating train of a crude distillation unit of a refinery, which processes 994 m3/h, which presents a formation of a fouling layer inside it. Among the impacts of fouling is the reduction in the effectiveness of heat transfer, the increase in fuel consumption, the increase in CO2 emissions, the increase in maintenance costs, and the decrease in the profit margin of process. An appropriate cleaning program of the surface of the heat exchanger network is necessary to preserve its key performance parameters, preferably close to design values. This paper presents the maintenance method centered on energy efficiency, to plan the intervention of the preheating train equipment maintenance, which considers the economic energy improvement and the cost of the type of maintenance. The method requires the calculation of the fouling evolution from which the global heat transfer coefficient is obtained, and the heat flux is determined as a function of time. It was observed that, as time passes, the resistance provided by fouling increases and that the overall heat transfer coefficient decreases. The energy efficiency centered maintenance has an indicator of economic justification (factor J) that relates the economic-energy improvement achieved when performing maintenance, taking into account the economic effort invested. Depending on the cost of the type of maintenance to be performed, a threshold should be chosen, from which the maintenance activity is justified. The effectiveness values of the heat exchanger (ε) and the J indicator are used to form a criticality matrix, which allows prioritizing maintenance activities in each equipment. The planning of the implementation dates of the maintenance of each heat exchanger, from the maintenance method centered on energy efficiency applied to the crude distillation unit’s, preheat train, constitutes a contribution in this specific field. The conceptual design of the maintenance method centered on energy efficiency presented in this work is feasible for other heat transfer equipment used in oil refineries and industry in general. The procedure developed uses real operation values, and with its implementation, a saving of 150000 US dollars was achieved.

scholarly journals Economic justification of the choice of the thermal protection of buildings

2018 ◽  
Vol 196 ◽  
pp. 04078
Author(s):  
Elena Malyavina ◽  
Anastasya Frolova
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Thermal Protection ◽  
Transfer Resistance ◽  
Cooling Systems ◽  
Heating And Cooling ◽  
Heat Protection ◽  
The Cost

A large number of factors influence the economically feasible heat transfer resistance of the building enclosing structures. First of all, it is the cost of insulation and heat for the building heating in the cold season. As shown by studies, it is not enough for air-conditioned buildings. The result depends on the mode of the building operation in time and the heat load on the heating and cooling systems. Therefore, in addition to these significant factors of economic feasibility of the thermal protection level, there are the cost of electricity for the production of cold for cooling the building, the cost of the building heating and cooling systems and the cost of connection to power supply networks. The got result is important to convey to the professional community in a clear and compact form. In the present work the buildings of administrative and office purpose are considered, the working day of which lasts from 9-00 to 18-00 hours with different specific heat supply from 0 to 80 W/m2 on the estimated area during working hours. Generalization of the research results is made on the basis of specific heat protection characteristics of the building, which is a product of the overall heat transfer coefficient of the building and the compactness coefficient. The total heat transfer coefficient of the building characterizes the heat losses and the heat inflows to the building through the enclosing structures, and the compactness coefficient can serve as an indicator of the surface area of the building, which is covered with insulation. For these buildings provision has been made for identification of the areas of the total discounted cost combination for all of the above components and the specific heat protection characteristics of the building relating to the feasibility of the specified level of the thermal protection.

Forced Convection Heat Transfer of Nanofluids: A Review

2017 ◽  
Author(s):  
Aditya Kuchibhotla ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Specific Heat ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Convection Heat

Stable homogeneous colloidal suspensions of nanoparticles in a liquid solvents are termed as nanofluids. In this review the results for the forced convection heat transfer of nanofluids are gleaned from the literature reports. This study attempts to evaluate the experimental data in the literature for the efficacy of employing nanofluids as heat transfer fluids (HTF) and for Thermal Energy Storage (TES). The efficacy of nanofluids for improving the performance of compact heat exchangers were also explored. In addition to thermal conductivity and specific heat capacity the rheological behavior of nanofluids also play a significant role for various applications. The material properties of nanofluids are highly sensitive to small variations in synthesis protocols. Hence the scope of this review encompassed various sub-topics including: synthesis protocols for nanofluids, materials characterization, thermo-physical properties (thermal conductivity, viscosity, specific heat capacity), pressure drop and heat transfer coefficients under forced convection conditions. The measured values of heat transfer coefficient of the nanofluids varies with testing configuration i.e. flow regime, boundary condition and geometry. Furthermore, a review of the reported results on the effects of particle concentration, size, temperature is presented in this study. A brief discussion on the pros and cons of various models in the literature is also performed — especially pertaining to the reports on the anomalous enhancement in heat transfer coefficient of nanofluids. Furthermore, the experimental data in the literature indicate that the enhancement observed in heat transfer coefficient is incongruous compared to the level of thermal conductivity enhancement obtained in these studies. Plausible explanations for this incongruous behavior is explored in this review. A brief discussion on the applicability of conventional single phase convection correlations based on Newtonian rheological models for predicting the heat transfer characteristics of the nanofluids is also explored in this review (especially considering that nanofluids often display non-Newtonian rheology). Validity of various correlations reported in the literature that were developed from experiments, is also explored in this review. These comparisons were performed as a function of various parameters, such as, for the same mass flow rate, Reynolds number, mass averaged velocity and pumping power.

Relation Between the Thermal Effectiveness of Overall Parallel and Counterflow Heat Exchanger Geometries

1989 ◽  
Vol 111 (2) ◽  
pp. 294-299 ◽  
Author(s):  
A. Pignotti
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Rate Ratio ◽  
Simple Relation ◽  
Two Fluids ◽  
The Heat Transfer Coefficient

A simple relation is established between the thermal effectiveness of two heat exchanger configurations that differ from each other in the inversion of either one of the two fluids. Using this relation, if the expression for the effectiveness of a configuration, as a function of the heat capacity rate ratio, and the number of heat transfer units, is known, the corresponding expression for the “inverse” configuration is immediately obtained. The relation is valid under the assumptions of temperature independence of the heat transfer coefficient and heat capacity rates, when one of the fluids proceeds through the exchanger in a single, mixed stream. The property is illustrated with several examples from the available literature.

Heat Transfer to Water-Oxygen Mixtures at High Pressure

2002 ◽  
Author(s):  
S. N. Rogak ◽  
S. Boskovic ◽  
D. Faraji
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Water Oxidation ◽  
Pure Water ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Water Oxygen ◽  
Maximum Heat Transfer

The constant pressure heat capacity and forced convection heat transfer coefficient was measured in a horizontal, smooth, electrically-heated tube. For the supercritical pressures considered, flow rates and temperatures (330–430 °C), the flow in the 6.2 mm ID tube was fully turbulent. The fluid was distilled water and up to 9 wt% oxygen. This mixture and the experimental conditions are found in supercritical water oxidation systems. At subcritical temperatures, the oxygen and water are almost immiscible, but just below the critical temperature, the fluid becomes single-phase. By measuring bulk and surface temperatures, knowing the mass and heat flux, both the heat capacity and heat transfer coefficient could be measured. The water-oxygen system is a highly non-ideal mixture, and small amounts of oxygen significantly reduce the temperature at which maximum heat transfer occurs. The changes in heat capacity appear to dominate the effect of oxygen on heat transfer, however, the mixtures do exhibit heat transfer deterioration at slightly subcritical temperatures, at flows and heat fluxes for which pure water shows nothing similar.

Heat capacity and heat transfer coefficient estimation for a dynamic thermal model of rail vehicles

2016 ◽  
Vol 23 (5) ◽  
pp. 439-452 ◽  
Author(s):  
Raphael N. Hofstädter ◽  
Thomas Zero ◽  
Christian Dullinger ◽  
Gregor Richter ◽  
Martin Kozek
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Model ◽  
Rail Vehicles ◽  
Coefficient Estimation

Analysis and Improvement of a Loosely Coupled Fluid-Solid Heat Transfer Method

2013 ◽  
Author(s):  
Zhi Wang ◽  
Roque Corral ◽  
Jose M. Chaquet ◽  
Guillermo Pastor
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cfd Simulation ◽  
Computational Time ◽  
New Approach ◽  
One Dimensional ◽  
Loosely Coupled ◽  
Transfer Method ◽  
The Cost

A new, fast and reliable loosely coupled fluid-solid heat transfer method is described. The approach is based on an improvement of heat transfer coefficient Forward Temperature Backward method. The numerical analysis of the coupling process of an one-dimensional model, shows that the convergence behaviour is influenced by the physical Biot number and a virtual heat transfer coefficient. The effect of using partially converged CFD solutions has also been studied. The novelty of the method is based on the use of dynamic evaluation of the numerical parameters of the coupling, namely the virtual heat transfer coefficient. Two representative models in turbomachinery applications are applied to test the proposed method. It is shown that the computational time can be reduced by a factor of three to five relative to previous existing methods. The new approach only spends around two times the cost of stand-alone CFD simulation of the problem to obtained a coupled fluid/solid thermal analysis.

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