[en] The contribution under consideration reports on a gamma denitometric measurement of gas concentrations in a vertical heated tube bundle which is flowed around by a fluid. Two measurement positions, two flow rates of the circulating fluid, two subcooling values and eleven heat fluxes were selected for the measurement. The authors of this contribution describe the test facility, measurement methodology, results and their interpretation. The measurement uncertainty is described in detail.

[en] This textbook contains the following main topics: Heat conductivity, convection, condensation and evaporation, radiation heat transfer and heat exchangers. It includes the physical foundations for all these aspects and many examples. (WL)

[en] The objective of this research is to estimate ablating and charring of heat shield materials in severe aero thermal / erosive environments. This requires an accurate and rapid technique for its serious heat transfer with moving boundary. Aerodynamic heating is obtained by an explicit relation. Fully implicit method is used for heat transfer calculation. Moving boundary is captured by VOF method. Thickness of heat shield, temperature of moving surface and radiation heat is presented. The results are in good agreement with other calculations. (author)

[en] A mathematical model of radiative heat exchange in the throats of wide-necked helium cryostats is analyzed. A comparison of the numerical results with known calculated and experimental data shows their good agreement

[en] The advanced thermal characteristics of nanomaterials allow better heat transfer efficiency in engineering, industrial and technological processes. In this report, the outcome of a comparative analysis between the dynamics of blood carrying Cu nanoparticles and blood carrying single-walled carbon nanotubes (SWCNTs) due to the stretching and rotation of two disks at various levels of rotation, stretching, power-law index and heat source/sink is presented. By using appropriate similarity variables, the leading partial differential equations (PDEs) are altered into one-dimensional equations (ODEs). The resulting ODEs are handled using the shooting method. The impact of governing parameters on the boundary layer profiles is analysed graphically. Fluid velocity gets enhanced in three dimensions during the rotation of the disk, but they predict different behaviours for the stretching parameters of the upper and lower disks. The temperature decays for power-law index, rotation and stretching parameters. Also, the rates of heat transfer are more extensive for shear-thinning. Finally, the effects of the Cu–blood(blood) nanofluid are dominant over the base fluid (blood) and SWCNTs–blood nanofluid. (author)

[en] Compared to the pure refrigerants, the zeotropic refrigerant mixtures have the obvious temperature glide during phase change. Therefore, the Lorenz cycle can be approached with this special attribute. By analysing the heat transfer in the counter flow heat exchanger, a new evaluation method for zeotropic refrigerant mixtures based on the variance of the temperature difference between the refrigerant and heat transfer fluid (HTF) is proposed in this paper. For approaching to the Lorenz cycle and perfect glide matching, the zeotropic mixture which has smaller variance in the heat exchanger should be chosen in the refrigeration cycle. The variance of temperature difference is affected by two factors which are the temperature difference between the inlet and outlet of HTF and the linear relationship between the refrigerant temperature and enthalpy, respectively. The smallest variance of the zeotropic refrigerant can be obtained by setting the temperature difference of HTF to be the optimal temperature difference.

[en] Short communication

[en] The use of additives in the base fluid is one of the techniques to strengthen the heat transfer with the amelioration in the field of nanotechnology. A new class of heat transfer fluids has been engineered, a base fluid (host) in which nano particles (guests) are dispersed and suspended stably. Researches have showed that these fluids exhibit higher thermal conductivity than the base fluid. As a result, the study of nanofluids has materialized as a new field of scientific interest and innovative application. The present work mainly focus es on the study of heat transfer characteristics and to analyze the thermal stability & other properties of nanofluid prepared by dispersing nanoparticles that are synthesized using green method. This work not only focuses on the heat transfer enhancement but also on the phenomena that are possible for this enhancement. (paper)

[en] The heat transfer augmentation in parabolic trough concentrator is gaining importance now a days as it makes the system compact and efficient. Out of various techniques, use of twisted tape inserts is popular due to easy implementation as well as substantial enhancement in system performance. Most of the studies in this field pertaining to experimental/computational analysis with respect to both outdoor and indoor set ups. The rise in convective coefficient of heat transfer fluid due to insert has been studied by many researchers. But such studies are based on uniform heat flux or out-field non-uniform based which is under uncontrollable environment. Hence in the present study, Nusselt number correlations for plain absorber and absorber with twisted tape (y=3.48, 5.42 and 7.36) are developed under the realistic condition of solar concentration with controlled environment. The parity plot shows the maximum deviation of 20% which in turn indicates better quality of fit. (paper)

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