A State Space Model for Real-Time Control of the Temperature in Indoor Space - Principle, Calibration and Results

Real-time control of comfort in indoor spaces needs models of temperature distribution and the air velocity field. Complete models, based on CFD, give this information but, because of processing time limitations, cannot be applied to real-time calculations. Therefore, a reduced model is needed. This study proposes to reduce the complexity of a CFD model by first considering a fixed velocity field and solving only the energy balance equation, then putting this equation in the form of state-space and finally by reducing its order by Proper Orthogonal Decomposition (POD).

Air Distribution Effectiveness for Different Mechanical Ventilation Systems

The purpose of ventilation is to dilute indoor contaminants that an occupant is exposed to. In a multi-zone environment such as a house, there will be different dilution rates and different source strengths in every zone. Most US homes have central HVAC systems, which tend to mix conditions between zones. Different types of ventilation systems will provide different amounts of dilution depending on the effectiveness of their air distribution systems and the location of sources and occupants.

An Investigation into Parameters Affecting an Optimum Ventilation Design of High Density Cities

This paper addresses the process of optimising the benefits of the natural (air) environment in the case of a high density city in which the amount of building volume is ultimately constrained. It is hypothesised that, in densely built cities, the amount of vertically placed gaps, permeability and porosity of the cityscape will affect the ventilation and wind environment. Wind tunnel experiments are described in which different amounts and positions of gaps were applied to a simplified city layout.

Application of the PHACES Tool in the Design of Natural Ventilation for Passive Cooling

Natural ventilation associated with shading techniques is an alternative way to reduce the use of expensive and environmentally harmful active systems, while providing summer thermal comfort and good indoor air quality. However, there is still a lack of knowledge concerning the design of such systems. The tool presented in this paper provides guidelines on natural ventilation and shading control strategies. This tool (called PHACES) has been developed under the MATLAB/SIMULINK environment by modelling an experimental device (HYBCELL) designed at the LASH/ENTPE laboratory.

Aspects of CFD Modelling of a Fan and Pad Evaporative Cooling System in Greenhouses

A methodology approach to simulate, by means of computational fluid dynamics (CFD) tools, a greenhouse equipped with a fan and pad evaporative cooling system is presented. Using the main aspects of evaporative cooling systems, in terms of heat and mass transfer, the flow and boundary conditions of the simulation model are identified taking into account both the external and internal climatic conditions. The crop (tomato) was simulated using the equivalent porous medium approach by the addition of a momentum source term.

Assessment of Uncertainty in Measurements with Low Velocity Thermal Anemometers

The important error sources associated with measurements using low velocity thermal anemometersincorporating an omnidirectional velocity sensor (LVTA) are identified and quantified. The impact of natural convection, directional sensitivity and dynamic response of the anemometer are modelled. The developed models, together with a database of instantaneous velocity records obtained by means of a Laser Doppler Anemometer are used to estimate the uncertainty of mean velocity and standard deviation of velocity measurements by LVTA.

Building Load and Energy Simulation Programs and the Design Process

Several building simulation programs have been developed for design, analysis and prediction of thedistribution of temperature, airflow and heat transfer between the inside and outside of a building, and/or between different zones of the building. These programs are categorized as mono-zone models (e.g. AIDA and Type 19 of TRNSYS), multi-room models (e.g. HOT2000, DOE, Type 56 of TRNSYS, EnergyPlus, COMIS and CONTAMW), zonal models (e.g. POMA and CWSZ), Computational Fluid Dynamics (CFD) models (e.g. EXACT3, FLUENT, FLOVENT, PHOENICS, and STAR-CD), and multi-zone models (e.g. ESP-r).

Carbon Dioxide Concentration and its Application in Estimating the Air Change Rate in Typical Irish Houses

In this study, the function of carbon dioxide as an index of indoor air quality and as a tracer gas to estimate the air exchange rate in naturally ventilated single family houses was investigated. Carbon dioxide concentrations were measured continuously in the occupied room of six selected Irish houses for periods of 2 to 7 days. The air change rates were then calculated according to the mass balance equation and the time variation of carbon dioxide levels.

Combining Junction Losses on Channel Sections in Ventilation Duct System Flow Analyses

When the airflow pressure losses at the junctions of ducts in ventilation systems are taken into account, the analysis becomes more complicated since no unique value for the static pressure is associated with a junction. Additional system equations expressing the pressure jumps over the junctions must be written down. A method to replace the junction losses approximately as equivalent channel section losses is presented. The method is based on dissipation considerations. Simpler system equations with fewer unknowns are obtained.

Control of Outdoor Ventilation Airflow Rate - Evaluation of Setting Methods

Ventilation is essential for the health and comfort of building occupants. It is particularly required to dilute and/or remove pollutants emitted by occupants' metabolism and activities. The concentration of metabolic CO2 is well correlated to metabolic odour intensity. Therefore CO2 concentration can be efficiently chosen as an indoor air quality index when occupants are the main source of pollution inside the buildings.

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