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The purpose of this study is to investigate the effect of panel connections on the hygrothermal performance of facade panels using a coupled, transient heat and moisture transfer analysis.

A coupled, transient heat and moisture transfer analysis has been conducted to investigate the effect of panel connections in the hygrothermal behavior of facade panels. Governing partial differential equations for the coupled heat and moisture transfer were formulated. Four panel connections proposed by pre-cast/pre-stressed concrete institute were modeled for the ultra-high performance fiber-reinforced concrete facade panel as illustrations and a finite element method was used to solve the numerical models.

The results of heat transfer analysis showed that steel connections could significantly reduce the thermal resistivity of facade panels by converging heat fluxes and acting as thermal bridges within facade panels. The results also showed that the maximum heat flux in the steel connector of the panel to foundation connection was 10 times higher compared to the other connections. Also, the results of moisture transfer showed that air gaps between the panels had higher moisture flux compared to the other layers in the models. The results show the significant importance of panel connections in the energy performance analysis of facade systems. They also highlight the importance of devising novel connection designs and materials that consider the transient, coupled heat and moisture transfer in the connections to effectively exploit the potential opportunities provided by innovative facade systems to improve building energy efficiency.

This paper, for the first time, investigates the effect of panel connections in the hygrothermal performance of building facade systems using a coupled, transient heat and moisture transfer analysis.

This study aims to perform a comprehensive investigation to model the thermal characteristics of a coupled conduction-radiation heat transfer in a two-dimensional irregular enclosure including a triangular-shaped heat source.

For this purpose, a promising hybrid technique based on the concepts of blocked-off method, FVM and DOM is developed. The enclosure consists of several horizontal, vertical and oblique walls, and thermal conductivity within the enclosure varies directly with temperature and indirectly with position. To simplify the complex geometry, a promising mathematical model is introduced using blocked-off method. Emitting, absorbing and non-isotropic scattering gray are assumed as the main radiative characteristics of the steady medium.

DOM and FVM are, respectively, applied for solving radiative transfer equation (RTE) and the energy equation, which includes conduction, radiation and heat source terms. The temperature and heat flux distributions are calculated inside the enclosure. For validation, results are compared with previous data reported in the literature under the same conditions. Results and comparisons show that this approach is highly efficient and reliable for complex geometries with coupled conduction-radiation heat transfer. Finally, the effects of thermo-radiative parameters including surface emissivity, extinction coefficient, scattering albedo, asymmetry factor and conduction-radiation parameter on temperature and heat flux distributions are studied.

In this paper, a hybrid numerical method is used to analyze coupled conduction-radiation heat transfer in an irregular geometry. Varying thermal conductivity is included in this analysis. By applying the method, results obtained for temperature and heat flux distributions are presented and also validated by the data provided by several previous papers.

Combined free and forced laminar air convective heat transfer from a vertical composite plate with isolated discontinuous surface heating elements has been studied numerically and experimentally. The problem has been simplified by neglecting heat conduction in unheated elements of the plate to accomplish a better understanding of the complicated combined/complicated convection problem. In this study, it is most important in explaining the heat transfer behaviour to clarify the interactions between buoyancy and inertia forces in the convective field and also the coupling effects of unheated elements upon the combined flow fields. Therefore, the temperature distributions of the wall surface and local Nusselt number, obtained by numerical calculations and experiments, have been discussed based on the various parameters associated with the present convection problem, i.e., Grashof number Gr_L, Reynolds number Re_L, geometry factor D/L and stage number N. Heat transfer characteristics Nu_t/Re^1/2_L of this combined and coupled convection of air are presented as a function of a generalized coupling dimensionless number Gr_L/Re²_L, and stage number N for certain values of the geometry factor of D/L.

The time of tightly coupled transient calculation and the accuracy of conventional loosely coupled algorithm make it difficult to meet the engineering design requirements for long-term conjugate heat transfer (CHT) problems. The purpose of this paper is to propose a new loosely coupled algorithm with sufficient accuracy and less calculation time on the basis of the quasi-steady flow field. Through this algorithm, it will be possible to reduce the update frequency of the flow field and devise a strategy by which to reasonably determine the update steps.

In this paper, the new algorithm updates the flow field by solving the steady governing equations in the fluid region and by calculating the transient temperature distribution until the next update of the fluid flow, by means of solving the transient energy equations in the entire computational domain. The authors propose a strategy by which to determine the update step, by using the engineering empirical formula of the Nusselt number, on the basis of the changes of the inlet and outlet boundary conditions.

Taking a duct heated by an inner forced air flow heating process as an example, the comparison results for the tightly coupled transient calculation by Fluent software shows that the new algorithm is able to significantly reduce the calculation time of the transient temperature distribution with reasonable accuracy. For example, the respective computing times are reduced to 22.8 and 40 per cent, while the duct wall temperature deviations are 7 and 5 per cent, using the two flow update time steps of 100 and 50 s on the variable inlet-flow rate conditions.

The new algorithm outlined in this paper further improves the calculated performance and meets the engineering design requirements for long-term CHT problems.

This paper aims to develop a numerical model to investigate coupled conduction radiation heat transfer in a multilayer semi-transparent polymeric foam.

The model uses a multi-phase approach in which the radiative transfer is determined by solving the radiative transfer equation explicitly in the whole medium incorporating an interface condition valid in the geometric optics rgime. This is executed by using a combination of ray splitting and a discrete curved ray tracing technique. Both partial photon reflection and total internal reflection at the interface are considered in the present investigation.

The directional distribution of intensity within the whole medium can be determined, which is used to obtain the detailed temperature profile inside the domain. The performance of the proposed methodology has been tested by simulating the modelled foam at ambient conditions. The results obtained from the simulations are in good agreement with the published results and shows that there is a global non-linearity in the temperature profile in problems where conduction to radiation parameter is small.

Specular nature of radiative transfer at the interface is accounted for in the present analysis. Instead of working with direction integrated quantities (as in the case of P1 approximation), each bundle of rays is treated separately within the whole medium. This model serves as a starting point for a detailed spatially three dimensional study of heat transfer in foams and the mathematical nature of the formulation is such that it may result in an implementation to three-dimensions.

We report on the progress in the development and application of a coupled boundary element/finite volume method temperature‐forward/flux‐back algorithm developed to solve conjugate heat transfer arising in 3D film‐cooled turbine blades. We adopt a loosely coupled strategy where each set of field equations is solved to provide boundary conditions for the other. Iteration is carried out until interfacial continuity of temperature and heat flux is enforced. The NASA‐Glenn explicit finite volume Navier‐Stokes code Glenn‐HT is coupled to a 3D BEM steady‐state heat conduction solver. Results from a CHT simulation of a 3D film‐cooled blade section are compared with those obtained from the standard two temperature model, revealing that a significant difference in the level and distribution of metal temperatures is found between the two. Finally, current developments of an iterative strategy accommodating large numbers of unknowns by a domain decomposition approach is presented. An iterative scheme is developed along with a physically‐based initial guess and a coarse grid solution to provide a good starting point for the iteration. Results from a 3D simulation show the process that converges efficiently and offers substantial computational and storage savings.

The problem of coupled heat and mass transfer by natural convection from a vertical, semi‐infinite flat plate embedded in a porous medium in the presence of an external magnetic field and internal heat generation or absorption effects is formulated. The plate surface is maintained at either constant temperature or constant heat flux and is permeable to allow for possible fluid wall suction or blowing. The resulting governing equations are non‐dimensionalized and transformed using a non‐similarity transformation and then solved numerically by an implicit, iterative, finite‐difference scheme. Comparisons with previously published work are performed and excellent agreement is obtained. Useful correlations containing the various physical parameters for both isothermal and isoflux wall conditions are reported. A parametric study of all involved parameters is conducted and a representative set of numerical results for the velocity, temperature and concentration profiles as well as the skin‐friction parameter, Nusselt number, and the Sherwood number is illustrated graphically to show typical trends of the solutions.

The purpose of this study is a numerical analysis of steady-state heat transfer behavior of couple-stress nanofluid sandwiched between viscous fluids. It should be noted that this research deals with the development of a cooling system for the electronic devices.

Stokes model is used to define the couple-stress fluid and the single-phase nanofluid model is used to define the nanofluid transport processes. The fluids in all regions are assumed to be incompressible, immiscible and the transport properties in all the three layers are assumed to be constant. The governing coupled linear ordinary differential equations are made dimensionless by using appropriate fundamental quantities. The exact solutions obtained for the velocity and temperature fields are evaluated numerically for various model parameters.

The results are demonstrated using different types of nanoparticles such as copper, silver, silicon oxide (SiO₂), titanium oxide (TiO₂) and diamond. The investigations are carried out using copper–water nanofluid for different values of couple-stress parameter a with a range of 0 = a = 12, solid volume fraction ϕ with a range of 0.0 ≤ ϕ ≤ 0.05, Eckert number Ec with a range of 0.001 ≤ Ec ≤ 6 and Prandtl number Pr with a range of 0.001 ≤ Pr ≤ 6. It was found that the Nusselt number increases by increasing the couple stress parameter, Eckert number and Prandtl number and it decreases with a growth of the solid volume fraction parameter. It was also observed that using SiO₂–water nanofluid, the optimal Nusselt number is obtained. Further, using copper, silver, diamond and TiO₂, nanoparticles and water as a base fluid does not show any significant changes in the rate of heat transfer. The couple-stress parameter enhances the velocity and temperature fields whereas the solid volume fraction suppresses the flow field for both Newtonian and couple-stress fluid.

The originality of this work is to analyze the heat transfer behavior of couple-stress nanofluid sandwiched between viscous fluids. The results would benefit scientists and engineers to become familiar with the analysis of convective heat transfer and flow structures in nanofluids and the way to predict the heat transfer rate in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

The general aim of this work is to calculate the extent of the equiaxed zone in continuously cast steel products. Free equiaxed grains can grow only in undercooled liquid regions. Undercooling of the bulk liquid occurs because the columnar dendrite tips growing from the mould reject solutes in the liquid. The specific aim of this contribution is to calculate the thermal and physical state of continuously cast steel long products assuming a columnar solidification mode, taking into account the tip undercooling at the solidification front. A 2‐D heat transfer model has been developed where the columnar solidification mode is assumed. The calculation of the undercooling at the advancing solidification front is coupled with the heat transfer equation. The comparison between the results of the present model and the classical heat transfer model indicates the importance of modelling the undercooling phenomenon. The influence of the secondary cooling has also been studied.

Carbonate-based heterogeneous reacting systems are investigated for the applications of thermochemical carbon dioxide capture and energy storage. This paper aims to review recent progress in numerical modeling of thermal transport phenomena in such systems.

Calcium oxide looping is selected as the model carbonate-based reacting system. Numerical models coupling heat and mass transfer to chemical kinetics are reviewed for solar-driven calcium oxide looping on the sorbent particle, particle bed, and reactor levels.

At the sorbent particle level, a transient numerical model of heat and mass transfer coupled to chemical kinetics has been developed for a single particle undergoing cyclic calcination and carbonation driven by time-periodic boundary conditions. Modeling results show cycle times impact the maximum sorbent utilization and solar-to-chemical energy efficiency. At the reactor level, a model of heat and mass transfer coupled to chemical kinetics of calcination of a packed-bed reactor concept has been developed to estimate the reactor’s performance. The model was used to finalize reactor geometry by evaluating pressure drops, temperature distributions, and heat transfer in the reactor.

Successful solar thermochemical reactor designs maximize solar-to-chemical energy conversion by matching chemical kinetics to reactor heat and mass transfer processes. Modeling furthers the understanding of thermal transport phenomena and chemical kinetics interactions and guides the design of solar chemical reactors.