Combined heat and moisture transfer in buildings systems

Temperature and humidity are the two main parameters indicating the comfort level of the building occupants. Although the effect of temperature is taken into account in thermal simulation of buildings, the moisture transfer through the rooms and porous building walls is sometimes neglected. The level of humidity can give different sensations of thermal comfort. It is necessary to take into account both heat and moisture transport in and around buildings to predict the hygrothermal behavior of rooms and building walls so as to calculate the energy demands correctly. In this work some benchmark exercises are worked out to see the performance of the heat and moisture transfer model implemented for rooms and porous walls. Finally, numerical results are compared with the measured data for a room exposed to varying outdoor conditions

Full Numerical Simulation of an Object Oriented Program for Hermetic Reciprocating Compressors: Numerical Verification and Experimental Validation.

An object oriented approach of the numerical simulation model for the thermal and fluid dynamic behavior of hermetic reciprocating compressors was previously presented (Damle, et al., 2008), describing the fluid flow resolution and its numerical verification, based on an updated version of the conservation equations resolution (continuity, momentum and energy) along the whole compressor domain in a sequential way (Pérez-Segarra, et al. 2003). In the present paper, not only a numerical verification is shown, but also an experimental validation is detailed, including to the object oriented code the heat transfer resolution between solid parts and its coupling with the fluid flow through compressor elements, in addition to kinematic and dynamic analysis of crankshaft vs. connecting rod mechanism. The present full object oriented numerical simulation program, together with a brief numerical verification is here presented, while a detailed experimental validation for different compressor capacities, fluid refrigerants and working fluids is also shown in order to assure the numerical results obtained and the possibilities offered by the new program.Peer ReviewedPostprint (published version

Parallelization of the coupling between CFD models for airflow and building energy simulation with an object-oriented infrastructure

Integrating CFD & HT models with the general building program raises the computational time of building simulations as these simulations are usually performed over a period of one year. Within this context, our aim is to couple a object-oriented modular building program with CFD & HT for airflow and parallelize the simulation with numerous processors for reducing computational time. Also the modular nature of the code will allow to resolve selective critical zones with CFD & HT models while employing simple models for airflow in less critical zones. Thus, there are different levels of modelling different rooms/elements of the building system depending on the requirements of a specific case

Energy simulation of buildings with a modular object-oriented tool

The aim of this work is to develop a modular object-oriented tool “NEST” (Numerical Edifice Simulation Tool) for the energy simulation of buildings, which can be coupled with a parallel CFD software. For this purpose, a building is modelled as a collection of basic elements (walls, rooms, outdoor, openings, etc.). Different models (1D, 2D, simplified energy balances, CFD & HT, etc) are implemented for different elements which are capable of solving themselves for given boundary conditions. The elements can be linked to each other to form a specific building configuration. Thus new configurations can be quickly formed by adding or removing the required elements. Such an approach gives flexibility of choosing a model for each element and to have different levels of modelling for different elements in the system. Moreover, elements developed can be used for applications not restricted to buildings only. The object-oriented methodology, element descriptions, BESTEST cases for code validation, and transient thermal simulations of two different cases are presented in this paper.Peer ReviewedPostprint (author’s final draft

Numerical simulation of combined heat transfer phenomena (conduction, convection, and radiation). Application to he optimisation of thermal systems

Thermal systems interchanging heat and mass by conduction, convection, radiation (solar and thermal ) occur in many engineering applications like energy storage by solar collectors, window glazing in buildings, refrigeration of plastic moulds, air handling units etc. Often these thermal systems are composed of various elements for example a building with wall, windows, rooms, etc. It would be of particular interest to have a modular thermal system which is formed by connecting different modules for the elements, flexibility to use and change models for individual elements, add or remove elements without changing the entire code. A numerical approach to handle the heat transfer and fluid flow in such systems helps in saving the full scale experiment time, cost and also aids optimisation of parameters of the system. In subsequent sections are presented a short summary of the work done until now on the orientation of the thesis in the field of numerical methods for heat transfer and fluid flow applications, the work in process and the future work

Large Eddy Simulation of Airflow in a Single Family House

This work is addressed to contribute to the progress in the determination of indoor air flow in buildings. The air flow in such environments is caused by natural convection, stack and wind effects, infiltration of ambient air and mechanical ventilation. It is important to be able to predict the pressure, temperature and velocity distributions in order to maintain an adequate indoor environment and to minimize the energy demand at the same time. The problem is difficult due to the large and complex geometry involved, the changing boundary conditions, the mixture of free and forced convection and especially, because the flows are turbulent. The purpose of this work is to explore the feasibility of the use of Large Eddy Simulation (LES) models to carry out full scale simulations of airflow in buildings. A review of the previous works shows that the use of LES for this kind of problems has been restricted to idealized geometries and relatively low Re numbers. In this work, for code validation, a 3D cavity with mixed convection is simulated and the numerical results are compared with the experimental data of Blay, et al. (1992). Then, a single family house with a realistic geometry, Re number of 11834 and Rayleigh number of 2.4 x 1010 is solved using a Yoshizawa Smagorinsky LES model. The code TermoFluids has been used for the simulation and post-processing of the results.Peer ReviewedPostprint (published version

Modular simulation of buildings with an object-oriented tool

The objective of this work is to develop a modular object-oriented building simulation tool “NEST” (Numerical Edifice Simulation Tool) which can be coupled with a parallel CFD software. To do so, a building is modelled as a collection of basic elements (walls, rooms, outdoor, openings, etc.). These elements are capable of solving themselves for given boundary conditions and can be linked to each other to form a specific building configuration. A modular approach gives flexibility of choosing a model for each element and to have different levels of modelling for different elements in the system. Also, new configurations can be made by adding or removing the required elements. Moreover, elements developed can be used for applications not restricted to buildings only. The object-oriented methodology, element descriptions, code validation with BESTEST cases, and transient thermal simulations of two different cases are presented in this paper.Peer ReviewedPostprint (published version

Mixed convection in a ventilated 3D cavity : comparison of different LES models with experimental data

The aim of this work is to contribute to the progress in the determination of indoor airflow in buildings and to explore the possibility of coarse grid CFDsimulations for room airflow in building energy programs. To do so, a three dimensional ventilated cavity with mixed convection is simulated with different LES models and different meshes to see their influence on the numerical results. The Rayleigh number for this case is 2.23 x 109 and the Archimedes number is 0.036. This case is, to a certain extent, a representative of the flow that exists in real building rooms and is sufficiently complex for modelling. Also, the numerical results are compared with experimental data.Peer Reviewe

Modular simulation of buildings with an object-oriented tool

The objective of this work is to develop a modular object-oriented building simulation tool “NEST” (Numerical Edifice Simulation Tool) which can be coupled with a parallel CFD software. To do so, a building is modelled as a collection of basic elements (walls, rooms, outdoor, openings, etc.). These elements are capable of solving themselves for given boundary conditions and can be linked to each other to form a specific building configuration. A modular approach gives flexibility of choosing a model for each element and to have different levels of modelling for different elements in the system. Also, new configurations can be made by adding or removing the required elements. Moreover, elements developed can be used for applications not restricted to buildings only. The object-oriented methodology, element descriptions, code validation with BESTEST cases, and transient thermal simulations of two different cases are presented in this paper.Peer Reviewe