Second Law and Energy Loss Analysis in a Turbulent Flow Through a Nozzle Type Duct

2005 ◽  
Author(s):  
S. R. Javadinejhad
Keyword(s):  
Heat Transfer ◽  
Energy Loss ◽  
Exchange Process ◽  
Dimensionless Number ◽  
Inlet Temperature ◽  
Primary Concern ◽  
Loss Analysis ◽  
Heat Exchanger Design ◽  
Heat Exchange Process ◽  
Pattern Forming

Amount of heat transfer is the primary concern in a heat exchanger design. The amount of energy that has been destroyed during the heat exchange process has been investigated by introducing a new dimensionless number. Analyises of simpler systems are often useful to understand more important features of complex pattern forming processes in various field of science and technology. The entropy generation have been studied by use of new dimensionless number . This number defined as the ratio of total energy loss to total heat transfer across the duct length. The temperature dependence on the viscosity is taken into consideration and results have been derived for various L/D ratio, nozzle angles and inlet temperature.

Energy Loss and Pumping Power Analysis of Fully Developed Laminar Convection in a Helical Coil

2007 ◽  
Author(s):  
Seeaidreza Javadinezhad ◽  
Zahra Asadikapourchali
Keyword(s):  
Heat Transfer ◽  
Energy Loss ◽  
Exchange Process ◽  
Design Parameters ◽  
Dimensionless Number ◽  
Helical Coil ◽  
Primary Concern ◽  
Pumping Power ◽  
Heat Exchanger Design ◽  
Laminar Convection

Energy loss characteristics of heat transfer and fluid flow due to forced convection of steady laminar flow of incompressible fluid in a helical coil is analysed. This paper analyses energy loss and pumping power in the fully developed laminar convection in a helical coil with constant wall heat flux. The important design parameters, including Reynolds number (Re), coil to tube radius (δ) and dimensional coil pitch (λ) are varied to investigate their influences on the energy loss and pumping power values. Amount of heat transfer is the primary concern in a heat exchanger design. The amount of energy loss during the heat exchange process has been investigated by introducing a new dimensionless number This dimensionless number has been defined as the energy loss to total heat transfer rate ratio. The energy loss dimensionless number behavior have been compared with entropy generation dimensionless number behavior for this problem.

scholarly journals Numerical analysis of heat exchange process in the biomass carbonisation reactor

2019 ◽  
Vol 252 ◽  
pp. 05019 ◽  
Author(s):  
Robert Zarzycki ◽  
Justyna Jędras
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Numerical Analysis ◽  
Exchange Process ◽  
Geometrical Model ◽  
Heating Time ◽  
Heating Process ◽  
Hot Air ◽  
Cyclic Operation ◽  
Heat Exchange Process

The study presents the problem of heat exchange in the biomass carbonisation reactor with cyclic operation. Based on the actual parameter of the biomass carbonisation reactor, a geometrical model was developed, and the computation of the heating process was conducted for two cases: an empty reactor and a filled reactor. Its result demonstrated that for the analysed configuration of the reactor, the process of heating biomass in the containers is limited by the capability of heat transfer to the biomass in the container. The results suggest opportunities for the improved heat exchange in the reactor and, accordingly, shortening heating time through installation of the system that forces circulation of hot air inside the reactor.

scholarly journals ANALYSIS OF EVAPORATOR EFFECTIVENESS ON 1/2 CYCLE REFRIGERATION SYSTEMS: A CASE STUDY ON LPG FUELED VEHICLES

2020 ◽  
Vol 82 (3) ◽  
Author(s):  
Muji Setiyo ◽  
Budi Waluyo ◽  
Nurkholis Hamidi
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Exchange Process ◽  
Cooling Curve ◽  
Heat Exchange Process ◽  
Heat Transfer Capacity ◽  
The Ideal

The ½ cycle refrigeration system on LPG fueled vehicles has a significant cooling effect. However, the cooling is very dependent on the heat exchange process in the evaporator. Therefore, this paper analyses the deviation of the actual cooling curve from the ideal scenario carried out on a laboratory scale. The analytical method used is the calculation of the effectiveness of the evaporator, which compares the actual to the potential heat transfer capacity. The LPG flow rate was varied from 1-6 g/s, while the evaporation pressure ranged between 0.05, 0.10, and 0.15 MPa, which applied to compact type evaporators with dimensions of 262 ´ 200 mm, with a thickness of 65 mm. The research results confirm that the higher the LPG mass flow rate, the lower the heat transfer effectiveness. At the higher LPG mass flow rate, heat transfer occurs less optimally,  due to incomplete evaporation of LPG in the evaporator.

scholarly journals NOVEL TRENDS OF DEVELOPMENT AND PERFECTION THE MODERN HEAT EXCHANGERS

2019 ◽  
pp. 54-65
Author(s):  
B.S. Soroka
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Exchange Process ◽  
Combustion Products ◽  
Reynolds Analogy ◽  
Heat Exchange Equipment ◽  
Heat Exchange Process ◽  
Heat Transfer Phenomenon ◽  
Relative Change

Some actual aspects of advancement the problem of improvement the heat exchange equipment are considered in the paper. First of all the actual items related to middle and high temperature recuperators are discussed with proper up-to — date approaches. The classification of flue gases heat recovery appliances has been proposed along with the statement and analysis of the main characteristics of the recovery plants and option the ways of optimization the mentioned characteristics. The problem of Reynolds analogy (similarity of relative change the heat transfer phenomenon and variation the hydraulic resistance) within the channels of different purpose and of various cross-section supplied with and without the obstacles has been analyzed in application to separate cases of flow along the surfaces equipped with the cavities (dimples) or the convex elements. Thermal Performance Factor (TPF) of the heat exchange process is qualitatively like to Reynolds analogy factor and is highly depended upon rate of heat transfer and of friction factor in conditions of the scheme under consideration for flow over the surface or flow within the channel. The various media has been compared used as a working body in the heat exchanger’s channels: gaseous, liquid and the nanofluids, the last appeared in practice since 2000. Analysis has been carried out on effect of using the secondary energy emitters (SEE) arranged inside the tube channels, on resulting heat flux by heat exchange between outward flow of combustion products and the inner air flow. Bibl. 23, Fig. 6.

Semiempirical Method of Boiling Expectation Time Calculation in Falling Wavy Liquid Film

2012 ◽  
Vol 7 (3) ◽  
pp. 78-83
Author(s):  
Andrey Chernyavskiy ◽  
Aleksandr Pavlenko
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Thermal Conductivity Coefficient ◽  
Exchange Process ◽  
Semiempirical Method ◽  
Liquid Films ◽  
Wave Characteristics ◽  
Time Calculation ◽  
Heat Exchange Process ◽  
The Mathematical Model

The Mathematical model which allows to calculate boiling expectation times in falling wavy liquid films on nonsteady heat release has been represented. It has been shown that it is necessary to take a convective constituent of a heat transfer into account in heat exchange modeling in falling films. The effective thermal conductivity coefficient which invlolves a convective constituent of a heat transfer calculated from average wave characteristics using Vorontsov method has been used. The method of accounting of the wave moving influence on a heat exchange process has been presented. The comparison of results of a numerical simulation and experimental data has been done

scholarly journals Experimental Determination of the Influence of Shape on the Heat Transfer Process in a Crushed Granite Storage Bed

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6725
Author(s):  
Magdalena Nemś
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Flow Rate ◽  
Exchange Process ◽  
Heat Transfer Analysis ◽  
Crushed Rock ◽  
Storage Material ◽  
Flow Rates ◽  
Actual Surface ◽  
Heat Exchange Process

The article presents the problem of modelling the charging of a constant-phase bed storage in the first hours of the process. The places of errors in the heat transfer calculations for the packed beds were indicated. Granite in the shape of spheres and crushed rocks, with a characteristic dimension of 50 mm, was used for the experimental tests. The material was subjected to tomographic examination and then used as a storage material. The charging process was carried out for three flow rates: 0.006, 0.008 and 0.010 m3/s. After three hours of testing, the temperature of the outlet air for the granite sphere as the storage material was the same as for the granite crushed rock. However, the biggest differences occurred after 1 h of charging. They were equal to: 40.4% for the flow rate of 0.006 m3/s, 22.0% for the flow rate of 0.008 m3/s, and 18.5% for the flow rate of 0.010 m3/s. The differences were greater than the uncertainty of the measurements. As a result, different temperatures of the storage material were obtained. After three hours, they were equal to: 25.2%, 12.3% and 8.6% for the lowest, medium, and highest airflow, respectively. The conducted heat transfer analysis and the relationship Nu = f(Re) was determined. The influence of the calculated and actual surface of the crushed rock on the heat exchange process was explained. For all the tested air flow rates through the bed, higher thermal parameters were obtained for the crushed rock than for the sphere. The maximum differences in the Nu number were: 222.6%, 151.4% and 161.3% for the flow of 0.006, 0.008 and 0.010 m3/s, respectively. This means that the description of the heat exchange process in the piled beds would require a parameter that takes into account the geometry of the storage material.

Heat Exchanger Design Methodology for Electronic Heat Sinks

2006 ◽  
Vol 129 (7) ◽  
pp. 899-901 ◽  
Author(s):  
Ralph L. Webb
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Transfer Rate ◽  
Design Methodology ◽  
Design Method ◽  
Heat Sinks ◽  
Inlet Temperature ◽  
Heat Exchanger Design ◽  
Electronic Heat

This paper discusses the “inlet temperature difference” (ITD) based heat-exchanger (and its variants) design methodology frequently used by designers of electronic heat sinks. This is at variance with the accepted methodology recommended in standard heat-exchanger textbooks—the “log-mean temperature difference,” or the equivalent ε-NTU design method. The purpose of this paper is to evaluate and discuss the ITD based design methodology. The paper shows that the ITD based method is an approximation at best. Variants of the method can lead to either under- or overprediction of the heat transfer rate. Its shortcomings are evaluated and designers are directed to the well established and accepted design methodology.

scholarly journals Enhancement in Heat Exchange Process in a Shell and Tube Heat Exchanger using Nano-Particles

2020 ◽  
Vol 9 (3) ◽  
pp. 1791-1795
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Exchange Process ◽  
Flow Characteristics ◽  
Nano Particles ◽  
Tube Heat Exchanger ◽  
Nano Fluid ◽  
Heat Exchange Process ◽  
Shell And Tube ◽  
Improved Performance

Nanoparticles and nano-fluids are having its significant role in transforming and improvising the existing tools and techniques of science and other research. This experimental study deals with the parametric analysis of Al2O3 of size 20-30 nm and CuO of size 30-50 nm nanoparticles to improve the effectiveness of a shell and tube heat exchanger. Nanoparticles used in heat exchangers improved performance through better heat transfer characteristics. An experimental investigation was done on the forced convective heat transfer and flow characteristics of the nano-fluid flowing in a horizontal shell and tube heat exchanger under turbulent flow conditions. The heat transfer of nano-fluid is found higher than that of the base liquid at same mass flow rate and temperature difference. The heat transfer thus heat transfer parameters increases with an increase in volume concentration up to 1.6 % after which heat transfer decreases due to viscosity effects.

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