Nucleate pool boiling heat transfer coefficient have been experimentally measured on a horizontal rod heater for various liquid binary mixtures. Measurements are based on more than three hundred data points on a wide range of concentrations and heat fluxes. In this investigation, it has been confirmed that the heat transfer coefficient in boiling solutions are regularly less than those in pure component liquids with same physical properties. Several reasons should be responsible for this phenomenon, but mainly it could be related to preferential evaporation of the more volatile component(s) during bubble formation. In this article, the performances of major existing correlations to the present experimental data including pure and binary mixture liquids are discussed. It is shown that it is impossible to predict the accurate value of boiling heat transfer for liquid mixtures and even pure liquids by any existing correlations over all ranges of concentrations or heat fluxes. In this investigation, the Schlunder correlation - as a model with excellent theoretical basis - has been modified; however some models provide superior performance in our experimental range. Originally, it is stated by different authors that B0 - the ratio of the interfacial area of heat transfer to those of mass transfer as a tuning parameters in Schlunder model - is too complicated to predict and should be fitted empirically as a function of heat flux, density and pressure for any given binary system. In this investigation, B0, the mentioned tuning parameter has been basically derived based on the analogy of the mass, heat and momentum transfer. As the results, the average error of Schlunder model in a wide range of boiling parameters has been significantly reduced.

The main purpose of this article is to provide a critical analysis of published research on these heat transfer surfaces. Important experimental methods and numerical procedures are explained, and many types of vortex generators are described. The phenomenon of flow attributed to vortex generators mounted, connected, pierced, or placed inside surfaces that transmit heat was also examined. In addition, recommendations for applying vortex generator (VGs) technology to improve air-side heat transfer are provided, as well as information on the thermal performance of newly proposed VG heat transfer surfaces. The performance of air-side heating surfaces can often be significantly improved through the use of vortex generators. However, their effectiveness can be greatly affected by many factors, including fluid flow rate, pipe geometry (diameter, shape, pitch, in-line or staggered configuration), fin type, and geometry of the vortex generator (height, length, shape, angle of attack, etc.). Circular fin-tube heat exchangers generally perform worse in terms of thermal-hydraulic efficiency than flat-tube-fin and oval-tube-fin heat-exchanging devices, and more recently, suggested vortex generators. Most current heat exchanger optimization methods focus only on thermal-hydraulic performance.

Heat transfer by electromagnetic radiation is one of the common methods of energy transfer between objects. Using the fluctuation-dissipation theorem, we have studied the effect of particle arrangement in the transmission of radiative heat in many-body systems. In order to show the effect of the structure morphology on the collective properties, the radiative heat transfer is studied and the results are compared for fractal and periodic structures. The calculations for fractals are restricted to the fractal structures based on vicsek model. It is shown that the thermal conductance can be large even for far apart particles in periodic structures. In contrast, it is shown that fractal arranged nanoparticles display complex radiative behavior related to their scaling properties, and heat flux is not of large-range character in such structures.

In this paper numerical simulations were performed utilizing Computational fluid dynamics code Fluent to investigate the thermo-fluid performance of a wavy rectangular winglet supported fin-and-tube heat exchanger with five inline rows of circular tubes. The influence of wave height, number of waves, wavy winglet length and winglet attack angle on the thermo-fluid performance of the fin-and-tube heat transfer surface has been examined under laminar flow conditions. Further the Plain and wavy rectangular winglets are placed together over different tube locations and their effect on heat transfer and flow resistance is also examined. An enhancement factor has also been discussed to summarize the overall thermo-fluid performance. The results show that increase in the wave height increase both heat transfer and pressure drop, and an optimum wave height could be decided based on the enhancement factor. It is also found that the increase in wavy winglet length guides the flow more effectively towards the tubes wake region. It is also observed that with increase in number of waves the heat transfer performance initially increases and then decreases as the wave pitch becomes very small. For wavy winglet supported heat exchanger the optimum attack angle is found out for maximum enhancement factor.

The problem of steady, laminar and incompressible natural convection flow in an octagonalenclosure was studied. In this investigation, two horizontal walls were maintained at a constant hightemperature, two vertical walls were kept at a constant low temperature and all inclined walls wereconsidered adiabatic. The enclosure was assumed to be filled with a Bousinessq fluid. The studyincludes computations for different Prandtl numbers Pr such as 0.71, 7, 20 and 50 whereas the Rayleighnumber Ra was varied from 103 to 106. The pressure-velocity form of Navier-Stokes equations andenergy equation was used to represent the mass, momentum and energy conservations of the fluidmedium in the enclosure. The governing equations and boundary conditions were converted todimentionless form and solved numerically by penalty finite element method with discretization bytriangular mesh elements. Flow and heat transfer characteristics were presented in terms of streamlines, isotherms and average Nusselt number Nu. Results showed that the effect of Ra on the convection heattransfer phenomenon inside the enclosure was significant for all values of Pr studied (0.71-50). It wasalso found that, Pr influence natural convection inside the enclosure at high Ra (Ra > 104).

Radiative heat transfer must be considered in retail refrigerators with glass doors. Some methods have been proposed for reducing radiative losses, like usage of double glased windows filled with argon or other types of transparent material with low emissivity in infrared band. For evaluation of thermal radiation in commercial refrigerator compared to infiltration loss, thermal conduction and facilities loss, a three dimensional model has been developed. In this model all wall surfaces are isothermal and evaporator with specific temperature located in roof. The radiative properties of glass are considered as actual.The results show that decreasing internal temperature of cabinet incentive radiation losses. These losses are almost independent of window surface temperature. Increasing of emissivity factor of evaporator, causes increasing of thermal radiation flux of evaporator which can be used in design improvement. Radiation flux of each surface have been compared with convection flux. This comparison show the importance of covering windows in unutilized times.

The paper deals with the application of the infrared thermography to the determination of the convective heat transfer coefficient in complex flow configurations. The fundamental principles upon which the IRTh relies are reviewed. The different methods developed to evaluate the heat exchange are described and illustrated through applications to the aerospace and aeronautical field as well as to the industrial processes.