Flow and heat transfer near a cylinders row

The paper aims to investigate the dependence of heat transfer classification on the Reynolds number (Re) during flow around circular heated cylinders row. The investigated range of Re number varies from 4.5×103 up to 42×103. The distance between cylinders S was changed from 0.5d to 4d (where d is the cylinders dia). Cylinders surface temperature was kept constant. For each Re number, the case when the cylinders were mounted one after the other was investigated. To measure heat transfer and flow parameters (velocity, heat flux and heat transfer coefficient) near and at the cylinders surface, two experimental methods were used: gradient heatmetry and PIV. Heat flux and velocity fields were obtained from gradient heatmetry and PIV results, based on which the flow mode could be determined and compared with heat transfer mode. As a result, it was found that heat transfer is influenced by both the Reynolds number and the distance between the cylinders. The observed features are associated with influence on characteristics such as separation point location, boundary layer thickness, change in flow between the cylinders and vortices formation.

Numerical Simulation of Paraffin Melting Process in an Inclined Channel

Numerical simulation of the melting of paraffin in the inclined straight channel shows that the melting speed of paraffin is faster in the early stage and gradually slows down in the later stage. It is found that heat conduction is the main heat transfer mode in the early stage of paraffin melting. With the increasing number of liquid paraffin, natural convection occurs in the liquid paraffin. The liquid paraffin with higher temperature flows upward due to the effect of buoyance and lift, and convection heat transfer gradually increases and takes the dominant position in the melting process.

Numerical Study Using Microstructure Based Finite Element Modeling of the Onset of Convective Heat Transfer in Closed-Cell Polymeric Foam

The thermal performance of closed-cell foams as an insulation device depends on the thermal conductivity. In these systems, the heat transfer mode associated with the convective contribution is generally ignored, and studies are based on the thermo-physical properties that emerge from the conductive contribution, while others include a term for radiative transport. The criterion found in the literature for disregarding convective heat flux is the cell diameter; however, the cell size for which convection is effectively suppressed has not been clearly disclosed, and it is variously quoted in the range 3–10 mm. In practice, changes in thermal conductivity are also attributed to the convection heat transfer mode; hence, natural convection in porous materials is worthy of research. This work extends the field of study of conjugate heat transfer (convection and conduction) in cellular materials using microstructure-based finite element analysis. For air-based insulating materials, the criteria to consider natural convection (Ra=103) is met by cavities with sizes of 9.06 mm; however, convection is developed into several cavities despite their sizes being lower than 9.06 mm, hence, the average pore size that can effectively suppress the convective heat transfer is 6.0 mm. The amount of heat transported by convection is about 20% of the heat transported by conduction within the foam in a Ra=103, which, in turn, produces an increasing average of the conductivity of about 4.5%, with respect to a constant value.

Thermophysical Characterization and Numerical Investigation of Three Paraffin Waxes as Latent Heat Storage Materials

Thermophysical characterization of three paraffin waxes (RT27, RT21 and RT35HC) is carried out in this study using DSC, TGA and transient plane source technics. Then, a numerical study of their melting in a rectangular enclosure is examined. The enthalpy-porosity approach is used to formulate this problem in order to understand the heat transfer mechanism during the melting process. The analysis of the solid-liquid interface shape, the temperature field shows that the conduction is the dominant heat transfer mode in the beginning of the melting process. It is followed by a transition regime and the natural convection becomes the dominant heat transfer mode. The effects of the Rayleigh number and the aspect ratio of the enclosure on the melting phenomenon are studied and it is found that the intensity of the natural convection increases as the Rayleigh number is higher and the aspect ratio is smaller. In the second part of the numerical study, a comparison of the performance of paraffins waxes during the melting process is conducted. Results reveals that from a kinetically RT21 is the most performant but in term of heat storage capacity, it was inferred that RT35HC is the most efficient PCM.

High Performance of Solar Cooker by Heat Transfer Mode Condition System Using Fuzzy Logic Controller Applications

In this work has been made to predict the effect of several parameters on the productivity to a system by expending fuzzy set technique. A solar cooker has been developed low cost and critically high efficiency produce in Vel Tech Multitech Engineering College at Chennai, Tamilnadu, India. Dissects in thermal performance of cooking system have been produced heat transfer follow in fuzzy logic techniques (Low, Medium, and High). The thermal effect of factor should be developed in fuzzy logic for the system. They should have groups of heat transfer produced in fuzzy logic controller for solar cooker system which had been implemented of system performance discussed. It is to study have induced to give the shortly time for the enhancement of the box solar cooker production.

Modelling of Operating Conditions of Conduction Heat Transfer Mode Using Energy 2D Simulation

<p>An energy transfer across a system boundary due to a temperature difference by the mechanism of inter-molecular interactions called conduction heat transfer. In the present work, a mathematical model and a simulation based on Energy 2D V 3.0.1 simulator are presented to study the effect of the conduction parameters: thermal conductivity, surface contact area, temperature difference and conduction distance on the heat transferred by the conduction mode. </p>

Drying of algae by various drying methods

Algae drying was carried out using Vacuum Tray Dryer and an Innovative Solar Conduction Dryer. Algae was dried in a Vacuum Tray Dryer at 60°C under varied pressure conditions and makes use of specially designed double condenser system. The open sun drying and solar conduction dryer (SCD) was also used for algae drying. Comparison between open sun drying and solar conduction dryer were done and it was found that the solar conduction dryer gives high performance than the open sun drying. It was also found that, the conductive heat transfer mode plays a crucial role in the solar conduction dryer. Keywords: Vaccum Dryer; Solar Conduction Dryer; Algal Drying