Patrice Blondeau

Night ventilation for building cooling in summer

Abstract This paper presents a two-step analysis of night ventilation as a way of cooling office buildings and providing comfort in summer. Experimental data first allows us to discuss some factors which affect the performance of the technique, to show that significant comfort improvement may be obtained in “well-designed” rooms, and to investigate the energy removal from the building by defining a potential energy efficiency index. Through the use of numerical simulations, we then deal with the useful cooling energy which is offered by night ventilation in the experimental configuration and show that much care has to be taken when the technique is intended to be used in the frame of a mixed-mode cooling system.

Multicriteria analysis of ventilation in summer period

This paper presents a multicriteria analysis of ventilation during summertime in Europe. Multicriteria analysis theories are used to determine the most suitable ventilation strategy on a university building, that is to say to ensure the best possible indoor air quality, thermal comfort of the occupants and the lower energy consumption in case of accelerated diurnal or nocturnal ventilation and/or air conditioning. After defining the possible actions, the criteria of quality regarding thermal comfort, indoor air quality and energy consumption are defined. The possible actions are then assessed relative to each of these three criteria and ranked from the best to the worst ones using two different multicriteria analysis methods.

Measurement of Thermal Comfort and Indoor Air Quality Aboard 43 Flights on Commercial Airlines

This paper reports the results of thermal comfort and indoor air quality measurements aboard aircraft from 43 flights on commercial airlines with a duration of more than 1 h. The measurements were performed continuously during the whole flight (from the departure gate to the arrival gate), and the parameters monitored were temperature, relative humidity and carbon dioxide concentration. The results were then compared with the ASHRAE Standards for the thermal comfort (ASHRAE Standard 55-92) and indoor air quality (ASHRAE Standard 62-89). The evaluation of the indoor air quality was based mainly upon comparison of the carbon dioxide concentrations measured with standards and recommendations for the indoor environment. Overall, the levels of relative humidity were far lower than the limit set by the ASHRAE Standard 55-92. The levels of carbon dioxide on most flights were higher than that recommended by the ASHRAE Standard 62-89. The results of this study, mainly the low level of humidity and high concentrations of carbon dioxide, led us to expect that the crew and the passengers would have been dissatisfied with their degree of thermal comfort and the quality of the air in the cabin. This conclusion is based simply on a comparison of our measurements with the values stated in the ASHRAE Standards. However, we must bear in mind that these were developed for an indoor environment at atmospheric pressure. More research is needed to study the validity of these standards for sub-atmospheric conditions.

Sorption Isotherms of Acetone on Various Building Materials

The physical modelling of Indoor Air Quality (IAQ) suffers a lack of sorption data for the most common Volatile Organic Compounds (VOC) on building materials. This paper deals with an experimental facility that aimed to provide the sorption isotherms of gaseous contaminants on various materials. It was used to determine the sorption isotherms of acetone on chipboard, acrylic paint, and the gypsum core of commercially available gypsum board. After a brief introduction to fundamental principles of sorption, the experimental device is presented in detail. The results are reported and discussed, emphasising the description of the isotherm shapes and the possible partial reversibility of the sorption phenomenon for porous materials. The resulting curves are clearly non linear when dealing with gypsum and chipboard. Moreover, the sorption isotherms of acetone on gypsum were found to be different whether they were determined in the directions of increasing or decreasing concentrations. Many questions remain unresolved about the physico-chemical processes involved, the sorption data to be considered for the purposes of IAQ modelling, and the way to account for the observed phenomenon when modelling the sorption/diffusion contaminant transport in building materials.

Short-term storage systems of thermal energy for buildings: a review

Thermal energy storage in buildings is essential to reduce energy consumption, to switch electrical consumption from on-peak period to off-peak period and to develop the use of intermittent renewable energy sources. Several systems designed to store thermal energy on a short-term scale (maximum a few days of storage) are presented in previous publications. However, there are no available comparisons of these systems and their conditions of use. This paper details these different designs for short-term scale thermal energy storage, regarding (i) their passive or active nature, (ii) their usage conditions and (iii) their performances. In the first section, the thermal properties of materials are listed. In particular, advantages and problems associated with phase change materials are presented. Subsequently, thermal storage systems are presented in two parts, on the one hand, passive systems and on the other hand active systems, according to the fluid used. For each system, the advantages of substituting sensible storage with latent storage are highlighted. Furthermore, an original and comparative analysis of published studies attempts to define some criteria and requirements for efficient use of latent storage. This review demonstrates that an exhaustive comparison of the systems encounters difficulties, due to the differences between the studies with respect to experimental measurements and weather data and the lack of similar comparison criteria, such as decrement factor, efficiency and cost.

Physically Based Modelling of the Material and Gaseous Contaminant Interactions in Buildings: Models, Experimental Data and Future Developments

Abstract Although potentially having a significant influence on indoor air quality (IAQ), interactions between building materials and gaseous contaminants have often been neglected or crudely modelled in IAQ simulation tools. During the past 20 years, empirical source and sink models have progressively given way to physically based models; but confusion still remains on their applicability, as well as on the adequate experimental data to input for the model parameters. Thus, demonstration is first made that models relating macroscopically the room air phase and material concentrations through adsorption and desorption constants are not scientifically sound. Instead, elemental models combining diffusion equations and local sorption equilibria should be used. The compilation of sorption and diffusion data presented in the second part of this chapter underlines the fact that such data cannot be considered independently from the mass transport equations used to fit the measurements. As a result, a thorough analysis of diffusion processes in polymers and porous media is presented in order to define and relate the diffusion coefficients. Finally, the last part of the chapter discusses the way in which existing models could be extended to account for the contributions of temperature, multi-component mixtures, humidity and chemical transformations within materials. Still based on fundamental considerations, the proposed methodology consists of implementing new functionalities to describe the temperature dependence of the model parameters, elemental models representing the interactions between gaseous contaminants and water, as well as kinetic models coming from the fields of atmospheric and surface sciences.

Assessment of indoor HONO formation mechanisms based on in situ measurements and modeling

The photolysis of HONO has been found to be the oxidation driver through OH formation in the indoor air measurement campaign SURFin, an extensive campaign carried out in July 2012 in a classroom in Marseille. In this study, the INCA-Indoor model is used to evaluate different HONO formation mechanisms that have been used previously in indoor air quality models. In order to avoid biases in the results due to the uncertainty in rate constants, those parameters were adjusted to fit one representative day of the SURFin campaign. Then, the mechanisms have been tested with the optimized parameters against other experiments carried out during the SURFin campaign. Based on the observations and these findings, we propose a new mechanism incorporating sorption of NO2 onto surfaces with possible saturation of these surfaces. This mechanism is able to better reproduce the experimental profiles over a large range of conditions.

A systematic approach for evaluation of gas-phase filter model

This article reports the development of a systematic methodology for the evaluation of gas-phase filtration models. In this approach, two sets of experiments are performed. For the first, all of the required model input parameters are quantified either experimentally or empirically. The second set of experiments is needed for the overall model validation process. The proposed methodology was applied to an existing gas-phase filter model that was developed for application to a single or a mixture of contaminants. The model was evaluated for two gases, namely n-hexane and methyl ethyl ketone, and four scenarios: (1) single methyl ethyl ketone at a dry air condition, (2) single n-hexane at a dry air condition, (3) a mixture of methyl ethyl ketone and n-hexane at a dry air condition, and (4) a mixture of methyl ethyl ketone and n-hexane at a humid air condition. The model was able to predict the lifetime of the filter for a single contaminant with less than 10% relative error. For the binary mixture, the model could not predict the lifetime of the heavier compound; however, it was able to predict the lifetime of the filter for the lighter compound with about 25% relative error. For the case of a mixture, the model underestimates the displacement phenomenon of a lighter compound. It was also noted that in the case of a heavier compound, there is good agreement between the models prediction, when it was applied to a single gas, and the experimental data for the single and mixture gas. It was also concluded that humidity has little effect on the breakthrough profile.

Data on comparison between FLEC and CLIMPAQ methods used for fast sorption measurements of VOCs on building materials

A test emission chamber called CLIMPAQ has been coupled to a chromatography analyzer GC to measure volatile organic compounds (VOC) concentration during a sorption experiments (Fast sorption measurements of VOCs on building materials: Part 2 – Comparison between FLEC and CLIMPAQ methods, (Rizk et al., In press) [1]). The equations used to calculate the mass transfer coefficient and the thickness of the boundary layer developed on the surface of a material are presented. In addition, the experimental profiles obtained using the CLIMPAQ chamber is also presented in the presence and the absence of a building material. Finally, the impact of chamber size on the obtained concentration profile using different chambers is shown using 3 types of chambers having different volumes, 1 m3, 30 m3 and a micro chamber of 40 mL.

PANDORA database: A compilation of indoor air pollutant emissions

Modeling indoor air quality (IAQ) in real buildings still remains difficult because of the limited data regarding the pollutant outdoor concentrations and indoor sources. The characterization of indoor sources is currently problematic, as most of studies have focused solely on measuring indoor concentration levels instead of determining the source emission rates that are required to model the indoor concentration changes with time. The present work aims at compiling the available data regarding the emission rates of both gaseous and particulate pollutants in a systematic way into a unique database called PANDORA (a comPilAtioN of inDOor aiR pollutAnt emissions) to provide useful information for IAQ modelers. In addition to the presentation of PANDORA, the elaboration of a target volatile organic compounds (VOC) list based on the emission rates implemented in the database is also described. Results show that the obtained target VOC list is similar to those based on actual indoor VOC concentration measurements, demonstrating that PANDORA alone can be used to produce such a list and that, considering the data integrated in the database, formaldehyde, acetaldehyde, and benzene are the three VOC that should be carefully accounted for in IAQ analysis.