The purpose of this article is to present and validate a computationally efficient numerical approach for the calculation of the ground-coupled heat transfer in buildings with periodic boundary ...conditions. When the boundary conditions of the heat transfer problem are described by periodic functions, it is possible to consider the transient state problem as a quasi-stationary problem with considerable savings in terms of computational time. The method is presented in detail from a mathematical point of view, together with a validation for two simple cases of slab-on-grade thermal losses, four comparisons with the ISO 13370:2007 procedure, a case with a complex shape and an evaluation of the computational efficiency.
•A numerical design model of a Concrete Solar Collector (CSC) has been developed.•Transient simulations for three European climates have been carried out.•For Stuttgart climate, the CSC reached a ...winter energy yield of 460.77kWh/m2/y.•CSCs can be alternatives to air-source compression heat pumps.•Morris method has been applied for ranking the most influent design parameters.
The aim of this work is to investigate the energy potential of using exposed concrete structures as solar energy absorbers (here denoted with the general term of Massive Solar-Thermal Collectors, MSTCs) during the heating period and in particular the design of a Concrete Solar Collector (CSC) is then presented. The CSC is a particular kind of MSTC, conceived as an exposed free standing structure that embeds a coiled pipe heat exchanger in a massive-concrete matrix. A numerical design model has been developed and parametric simulations have been conducted in order to get a figure of the energy potential of the CSC under different European climate conditions. The CSC has reached an energy yield of 460.77kWh/m2/y and an average heat flux of 93.07W/m2 for the reference climate of Stuttgart (Germany) during the winter season (inlet fluid temperature of −5°C and mass-flow rate of 45kg/h/m2). The Elementary Effect Method has been adopted as Sensitivity Analysis procedure with the aim of understanding the dependency of design parameters on the energy output. Finally, an economic analysis has been carried out by comparing investment costs and energy outputs.
The objective of this work is to quantify the effects of the short-term climate change with a multiyear (MY) approach on the results of the heat and moisture transfer simulations of an historic ...building located in Udine (Italy) and to evaluate if a single year simulation could be representative of the results obtained with the MY. The hygrothermal performance and the moisture related risk are evaluated for a brick wall with and without insulation, with a MY of 25 years and with three single years selected form the MY. The software DELPHIN is used for the simulations and the damage indicators are calculated using simplified methods (number of days with unfavourable conditions). Depending on the damage considered, the years have different effects on the studied wall. The simulations that use the MY weather file allow to obtain more accurate results than using one-year simulations, but the effort and time required for the interpretation of the simulation results could be not acceptable. It is then shown that the choice of a representative weather file is crucial to the results of the risk analysis and that considering more than one weather file is necessary to obtain representative results for different damages mechanisms.
The present paper deepens the analysis on the dynamics and thermal-fluid-dynamics of a sprinkler nozzle-emitted water droplet traveling in air before reaching the ground. The following analysis ...variables were considered, as main causes of the phenomenon assessed: initial droplet diameter, initial droplet velocity, initial droplet temperature, variable droplet temperature, air temperature, diffusion coefficient of water in air, air relative humidity, inlet droplet throw inclination, thermal radiation, and wind velocity. These variables proved their effect on the droplet travel distance, the droplet time of flight, and the final droplet temperature. The study was carried out thanks to an analytical-numerical model, recently proposed by the same authors of this paper, equipped with a few assumptions that did not alter the realistic description provided. The results proved the effect of each analysis variable and clarify the picture of a complicate yet extremely important phenomenon.
Treatment for childhood cancer with chemotherapy, radiation and/or hematopoietic cell transplant can result in adverse sequelae that may not become evident for many years. A clear understanding of ...the association between therapeutic exposures and specific long-term complications, and an understanding of the magnitude of the burden of morbidity borne by childhood cancer survivors, has led to the development of guidelines to support lifelong risk-based follow up for this population. It is important to develop interventions to reduce the impact of treatment-related late effects on morbidity and mortality and to continue research regarding the etiopathogenesis of therapy-related cancers and other late effects.
The present paper is aimed at analyzing the behavior of water droplets traveling in air from the nozzle to the ground according to a traditional numerical and a quantum point of views. Considering a ...single-droplet system, an analytical model based on the Newtonian kinematics is here described, considering the most relevant parameters involved: droplet initial diameter, droplet initial velocity, water and air temperatures, diffusion coefficient of water in air, air relative humidity, environmental radiation, and presence of wind. The effect of those parameters on water evaporation is, hence, discussed. Differently, when a multi-droplet system in considered, the problem becomes even more complicated due to the difficulty of assessment of interdroplet reciprocal affections and both a Newtonian description and a numeric implementation are definitely hard to obtain. An alternative to traditional approaches to treat the water droplet dynamics is the quantum approach, which is here introduced and pointed out in order to give an as full as possible description of the whole phenomenon. Such an approach offers a more tight description of the microscopic phenomena that influence the evolution of the whole multi-droplet system.
As an alternative to the continuous analysis of coupled velocity and temperature fields, the average fluid velocities and the convective heat transfer coefficients are estimated first by standard ...engineering procedures. Afterwards, these values are specified as part of the input data in a finite element code that calculates the detailed temperature distributions in the solid and the bulk temperature variations in the fluid. In the examples, the finite element formulation is validated by comparison with a typical benchmark solution, and the capabilities of the finite element method are demonstrated by the analysis of coupled conduction and convection problems in refrigerated transport.
Pour remplacer l'analyse continue de la vitesse et des champs de température, les vitesses mo'rennes du fluide et les coefficients de transfert de chaleur par convection sont d'abord estimés par des procédures classiques. Ensuite, cas valeurs sont spécifieés de façon à être entrèes dans un code aux eléménts finis qui calcule les distributions de température détaillées dans le solide et les variations de température dans le fluide. Dans les exemples, la formulation des éléments finis est validée par comparaison avec une solution type de référence, et on montre les possibilités de la méthode des éléments finis pour l'analyse des problémes couplés de conduction et de convection dans le transport frigorifique.
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