Heat transfer characteristics of water flowing through micro-tube heat exchanger with variable fluid properties

Journal of Thermal Analysis and Calorimetry - The heat transfer characteristics of laminar single-phase forced convective water flow through a micro-tube heat exchanger are numerically investigated...     

Numerical modelling of the spiral plate heat exchanger

The spiral plate heat exchanger (SHE) is widely used in plenty of industrial services in full counter current flow liquid-liquid heat exchange. We have produced a thermal modelling of the heat exchanges in both steady-state and time dependent cases with 2D spiral geometry, allowing computation with different materials, forced convective heat transfer models in turbulent flow and geometrical parameters options. We will display here some results in steady-state conditions in order to improve the exchanger performances.     

Exergy analysis of a plate heat exchanger with a new geometric design

Journal of Thermal Analysis and Calorimetry - In the current study, a plate heat exchanger with a novel geometry is investigated in which the cross section is not uniform as in conventional ones....     

Computational simulation of variable magnetic force on heat characteristics of backward-facing step flow

Journal of Thermal Analysis and Calorimetry - The application of the nanofluid is highly increased due to its high heat rate in the attendance of the magnetic field. In current investigation, CFD...     

Two-phase simulation of nanofluid flow in a heat exchanger with grooved wall

Journal of Thermal Analysis and Calorimetry - The aim of this paper is to achieve a smaller and cheaper heat exchanger with similar performance. To fulfill this demand, ANSYS-Fluent software and...     

Aspects of thermal conductivity relative to heat flow

Summary The various techniques and methodologies of thermal conductivity measurement have been conventionally based on the determination of the rate of directional heat flow through a material having a unit temperature differential between its opposing faces. The constancy of this rate depends on the material density, its thermal resistance and the heat flow path itself. The last of these variables contributes most significantly to the true value of steady-state axial and radial heat dissipation depending on the magnitude of transient thermal diffusivity along these directions. The purpose of this paper is to exemplify the above features by defined parameters of heat flow measurement by existing methodologies. No new method is proposed here. Importantly, the relationship between the rate of heat transfer, total heat transferred and thermal conductivity at a given temperature under steady-state conditions for a fixed heat flow path will be illustrated.     

Distribution characteristics of liquid in spiral-wound heat exchanger under sloshing conditions

Journal of Thermal Analysis and Calorimetry - The maldistribution of working medium restricts the heat transfer performance of the spiral-wound heat exchangers (SWHEs), especially when the heat...     

Numerical simulation of nanofluid turbulent flow in a double-pipe heat exchanger equipped with circular fins

Journal of Thermal Analysis and Calorimetry - In this study, the thermal and flow characteristics of a nanofluid were evaluated numerically in a circular finned double-pipe heat exchanger. A 3D CFD...     

Optimization of the finned double-pipe heat exchanger using nanofluids as working fluids

Journal of Thermal Analysis and Calorimetry - The heat exchanger pipe diameter has a significant effect on the flow characteristics as well as on the initial investment, operation and overall cost....     

Differential thermal analysis and heat flow calorimetry of coffee and chicory products

The techniques of differential thermal analysis (DTA) and heat flow calorimetry were used to study the thermal behaviour of coffee and chicory products above 20°C. Intensive exothermic reactions were particularly evident when measurements were made under pressure, which prevents vaporization of the water contained in the products, in the temperature domain of interest.     

Heat transfer coefficient and pressure drop during refrigerant R-134a condensation in a plate heat exchanger

The condensation heat transfer coefficient and the two-phase pressure drop of refrigerant R-134a in a vertical plate heat exchanger were investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, local values of the heat transfer coefficient and frictional pressure drop were calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution and vapor quality profile inside the plate. The influences of the mass flux and the heat flux on the heat transfer coefficient and the pressure drop were also taken into account and a comparison with previously published experimental data and literature correlations was carried out. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Laminar heat transfer and fluid flow of two various hybrid nanofluids in a helical double-pipe heat exchanger equipped with an innovative curved conical turbulator

Journal of Thermal Analysis and Calorimetry - In the present study, the effect of inserting an innovative curved turbulator and utilizing two types of hybrid nanofluids on thermal performance in a...     

Experimental study on convective heat transfer and entropy generation of carbon black nanofluid turbulent flow in a helical coiled heat exchanger

Journal of Thermal Analysis and Calorimetry - The convective heat transfer coefficient (CHTC) of a fluid is one of the most effective factors on the performance of a fluid in heat transfer...     

Three-dimensional numerical simulation of external fluid flow and heat transfer of a heat exchanger in a wind tunnel using porous media model

Journal of Thermal Analysis and Calorimetry - Notwithstanding the widespread use of wind tunnel to investigate the performance of radiators and heat exchangers, has never been considered a...     

Experimental investigation of heat transfer and exergy loss in heat exchanger with air bubble injection technique

Journal of Thermal Analysis and Calorimetry - The main aim of this study is to evaluate thermal performance and exergy analysis of a shell-and-tube heat exchanger with a new technique called air...     

Modeling and control-oriented thermal characteristics under variable load of the solid oxide fuel cell

Journal of Solid State Electrochemistry - The performance of the solid oxide fuel cell (SOFC) is greatly influenced by its operating temperature. Therefore, making a profound study of the thermal...     

Optimization of glycerol fed-batch fermentation in different reactor states: a variable kinetic parameter approach

To optimize the fed-batch processes of glycerol fermentation in different reactor states, typical bioreactors including 500-mL shaking flask, 600-mL and 15-L airlift loop reactor, and 5-L stirred vessel were investigated. It was found that by reestimating the values of only two variable kinetic parameters associated with physical transport phenomena in a reactor, the macrokinetic model of glycerol fermentation proposed in previous work could describe well the batch processes in different reactor states. This variable kinetic parameter (VKP) approach was further applied to model-based optimization of discrete-pulse feed (DPF) strategies of both glucose and corn steep slurry for glycerol fed-batch fermentation. The experimental results showed that, compared with the feed strategies determined just by limited experimental optimization in previous work, the DPF strategies with VKPs adjusted could improve glycerol productivity at least by 27% in the scale-down and scale-up reactor states. The approach proposed appeared promising for further modeling and optimization of glycerol fermentation or the similar bioprocesses in larger scales.     

First and second laws of thermodynamics analysis of nanofluid flow inside a heat exchanger duct with wavy walls and a porous insert

This paper investigates the combined effects of using nanofluid, a porous insert and corrugated walls on heat transfer, pressure drop and entropy generation inside a heat exchanger duct. A series of numerical simulations are conducted for a number of pertinent parameters. It is shown that the waviness of the wall destructively affects the heat transfer process at low wave amplitudes and that it can improve heat convection only after exceeding a certain amplitude. Further, the pressure drop in the duct is found to be strongly influenced by the wave amplitude in a highly non-uniform way. The results, also, show that the second law and heat transfer performances of the system improve considerably by thickening the porous insert and decreasing its permeability. Yet, this is associated with higher pressure drops. It is argued that the hydraulic, thermal and entropic behaviours of the system are closely related to the interactions between a vortex formation near the wavy walls and nanofluid flow through the porous insert. Viscous irreversibilities are shown to be dominant in the core region of duct where the porous insert is placed. However, in the regions closer to the wavy walls, thermal entropy generation is the main source of irreversibility. A number of design recommendations are made on the basis of the findings of this study.

     

Numerical simulation of a three-layer porous heat exchanger considering lattice Boltzmann method simulation of fluid flow

Journal of Thermal Analysis and Calorimetry - The present study investigates the thermal characteristics of a proposed porous heat exchanger (PHE). This heat exchanger consists of three sections,...     

Building materials thermal conductivity measurement and correlation with heat flow meter, laser flash analysis and TCi

The most important factor in the worldwide problem of global warming is the emission of carbon dioxide. The 23% of carbon dioxide emissions generated by building construction must be reduced. Reduction in thermal conductivity, especially via improved insulation, is the most basic factor for decreasing energy consumption. Therefore, accurate and continuous thermal conductivity measurements are important in saving energy. This study presents methods for investigating thermal conductivity measurement and compares three methods: the heat flow meter, laser flash analysis, and thermal conductivity analyzer.