QC 20110811

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In this thesis, heat and moisture transfer between supply and exhaust air streams are investigated for a run-around system in which the coupling material is a desiccant coated solid that is transported between two exchangers. The finite difference method is used to solve the governing partial differential equations of the cross-flow heat exchangers in the supply and exhaust ducts. The outlet air properties are calculated for several inlet air operating conditions and desiccant properties. The accuracy of the heat transfer model is verified by comparing the simulations with well-known theoretical solutions for a single cross flow heat exchanger and a liquid coupled run-around system. The difference between the analytical predictions and the numerical model for sensible effectiveness for each exchanger and the run-around system were found to be less than 1% over a range of operating conditions. The model is also verified by modifying the boundary conditions to represent a counter flow energy wheel and comparing the calculated sensible, latent, and total effectiveness values with correlations in the literature. <p>Using the verified model for energy exchangers and the run-around energy recovery system, the sensible, latent and overall effectiveness are investigated in each exchanger and the run-around system during simultaneous heat and moisture transfer. The overall effectiveness of the run-around energy recovery system is dependent on the air flow rate, the solid desiccant flow rate, the desiccant properties, specific surface area, the size of each exchanger, and the inlet air operating conditions. The run-around system can achieve a high overall effectiveness when the flow rates and exchangers properties are properly chosen. Comparisons between the solid desiccant and salt solution run-around system effectiveness (Fan, 2005 and Fan et al, 2006) shows they are in good agreement. In a sensitivity study, the thickness of desiccant on the fibre is investigated in the solid run-around system. It was found that good performance is obtained with very thin desiccant coatings (1 or 2 micron). During the practical use of this system, a desiccant coated fibre could be inserted into very porous balls or cages that protect the desiccant coated fiber from mechanical wear. The performance sensitivity for this kind of run-around system is demonstrated.

Several recent projects in building science have examined the hygric performance of building materials. Most building materials adsorb from and desorb water vapour to their environments. This phenomenon could be used to help control relative humidity fluctuations in buildings, experienced during periods of moisture production such as cooking, washing or bathing. They could also be used to reduce the need for mechanical ventilation and air conditioning to remove excess moisture. To understand how a building material responds to transient changes in relative humidity, testing is required.<p> This thesis outlines the testing performed on gypsum board, a common wall and ceiling finishing material used inside buildings. The effect of paint coatings on the gypsum boards and heat and mass transfer coefficients of the air passing over the gypsum bed was tested. The data produced from these experiments was used to validate several numerical models through an International Energy Agency/Energy Conservation in Buildings and Community Systems (IEA/ECBCS), Annex 41: Whole Building Heat, Air and Moisture Response. The validated models are important for simulating the process of adsorption and desorption in building materials to predict failure in the building envelope and expected indoor air conditions.<p> A sensitivity analysis is also presented which examines the effects of the sorption isotherm and vapour permeability of the gypsum and paints as well as the heat and mass transfer coefficients the boards are exposed to. The sensitivity range used was determined from the tests performed on the gypsum boards and paints which were also performed during the work of Annex 41.<p> The results of this thesis produced a high quality data which can also be used to validate future numerical models. All information required for validation of future models is available such as dimensions of test section, test conditions, material properties and the experimental data.<p> The results show that when designing for passive humidity control in buildings using gypsum boards, the most influential factor is the type of coating or paint applied to the surface. The sensitivity analysis showed that material properties such as vapour permeability and the sorption isotherms, for the expected temperature range, should be well known for increased accuracy of the simulation. The material properties were determined from inter-laboratory testing at 14 different institutions to achieve confident values.<p> The effect of increasing the heat and mass transfer coefficients, over the range of coefficients studied in this thesis, showed negligible differences in the results. The simulated results had very good agreement between the models and were mostly within experimental uncertainty of the measurements.

In this thesis, heat and moisture transfer between supply and exhaust air streams are investigated for a run-around system in which the coupling material is a desiccant coated solid that is transported between two exchangers. The finite difference method is used to solve the governing partial differential equations of the cross-flow heat exchangers in the supply and exhaust ducts. The outlet air properties are calculated for several inlet air operating conditions and desiccant properties. The accuracy of the heat transfer model is verified by comparing the simulations with well-known theoretical solutions for a single cross flow heat exchanger and a liquid coupled run-around system. The difference between the analytical predictions and the numerical model for sensible effectiveness for each exchanger and the run-around system were found to be less than 1% over a range of operating conditions. The model is also verified by modifying the boundary conditions to represent a counter flow energy wheel and comparing the calculated sensible, latent, and total effectiveness values with correlations in the literature. <p>Using the verified model for energy exchangers and the run-around energy recovery system, the sensible, latent and overall effectiveness are investigated in each exchanger and the run-around system during simultaneous heat and moisture transfer. The overall effectiveness of the run-around energy recovery system is dependent on the air flow rate, the solid desiccant flow rate, the desiccant properties, specific surface area, the size of each exchanger, and the inlet air operating conditions. The run-around system can achieve a high overall effectiveness when the flow rates and exchangers properties are properly chosen. Comparisons between the solid desiccant and salt solution run-around system effectiveness (Fan, 2005 and Fan et al, 2006) shows they are in good agreement. In a sensitivity study, the thickness of desiccant on the fibre is investigated in the solid run-around system. It was found that good performance is obtained with very thin desiccant coatings (1 or 2 micron). During the practical use of this system, a desiccant coated fibre could be inserted into very porous balls or cages that protect the desiccant coated fiber from mechanical wear. The performance sensitivity for this kind of run-around system is demonstrated.

Several recent projects in building science have examined the hygric performance of building materials. Most building materials adsorb from and desorb water vapour to their environments. This phenomenon could be used to help control relative humidity fluctuations in buildings, experienced during periods of moisture production such as cooking, washing or bathing. They could also be used to reduce the need for mechanical ventilation and air conditioning to remove excess moisture. To understand how a building material responds to transient changes in relative humidity, testing is required.<p> This thesis outlines the testing performed on gypsum board, a common wall and ceiling finishing material used inside buildings. The effect of paint coatings on the gypsum boards and heat and mass transfer coefficients of the air passing over the gypsum bed was tested. The data produced from these experiments was used to validate several numerical models through an International Energy Agency/Energy Conservation in Buildings and Community Systems (IEA/ECBCS), Annex 41: Whole Building Heat, Air and Moisture Response. The validated models are important for simulating the process of adsorption and desorption in building materials to predict failure in the building envelope and expected indoor air conditions.<p> A sensitivity analysis is also presented which examines the effects of the sorption isotherm and vapour permeability of the gypsum and paints as well as the heat and mass transfer coefficients the boards are exposed to. The sensitivity range used was determined from the tests performed on the gypsum boards and paints which were also performed during the work of Annex 41.<p> The results of this thesis produced a high quality data which can also be used to validate future numerical models. All information required for validation of future models is available such as dimensions of test section, test conditions, material properties and the experimental data.<p> The results show that when designing for passive humidity control in buildings using gypsum boards, the most influential factor is the type of coating or paint applied to the surface. The sensitivity analysis showed that material properties such as vapour permeability and the sorption isotherms, for the expected temperature range, should be well known for increased accuracy of the simulation. The material properties were determined from inter-laboratory testing at 14 different institutions to achieve confident values.<p> The effect of increasing the heat and mass transfer coefficients, over the range of coefficients studied in this thesis, showed negligible differences in the results. The simulated results had very good agreement between the models and were mostly within experimental uncertainty of the measurements.

The main objective of this thesis research is to test the applicability of a novel heat and moisture transfer panel (HAMP) in an office building to control the space humidity. A HAMP is a panel that uses a liquid desiccant to add or remove heat and moisture to or from a space. This thesis research uses the TRNSYS computer package to model an office building in four different cities representing four climatic conditions. The cities are Saskatoon, Saskatchewan; Chicago, Illinois; Phoenix, Arizona; and Miami, Florida; representing cold-dry, cool-humid, hot-dry, and hot-humid climates, respectively. The HAMP is employed in the office building with a radiant ceiling panel (RCP) system. Three other HVAC systems are examined and compared to the system employing the HAMP. The systems are: a conventional all-air system, a RCP system with 100% outdoor air, a RCP system with a parallel dedicated outdoor air system (DOAS), and the RCP system with the HAMP and 100% outdoor air. In the latter, the HAMP covers 10% of the ceiling area and uses lithium chloride solution as the liquid desiccant at different temperatures and concentrations. The results show that the HAMP is able to control the space humidity within the control limits in all climates. The HAMP also shows the ability to provide better humidity control than the other systems as it directly responds to the space latent loads. The HAMP is able to control the relative humidity between 26% RH and 62%, 24% RH and 57% RH, 27% RH and 60%, and 40% RH and 62% RH in Chicago, Saskatoon, Phoenix, and Miami, respectively. The HAMP is able to achieve a relative humidity of 35% in Chicago, Saskatoon, and Phoenix for 14%, 13%, and 20% of the working hours of the year, respectively. It is also able to achieve a relative humidity of 60% in Chicago, and Miami 10% and 55% of the working hours of the year, respectively. The results also show the potential of the RCP system with the HAMP to reduce the total energy consumed by a conventional all-air system in the hot climates by 40%, and 54% in Miami and Phoenix respectively, and in the cold climates by 14% and 23% in Saskatoon and Chicago, respectively.

This study focuses on the hygrothermal performance of Moso bamboo. The knowledge in this aspect is remarkable important for the research of building energy saving and the low carbon building design. However, the detailed hygrothermal properties of Moso bamboo are fairly rare. To obtain these data, a series of experimental works have been done for measurement of density, porosity, thermal conductivity, specific heat capacity, water vapour permeability, hygrothermal expansion and sorption isotherm of Moso bamboo. To obtain further understanding on the hygrothermal performance of Moso bamboo, a number of dynamic heat and moisture transfer experiments were conducted. These experiments simulated two extreme outdoor environments and one indoor environment. The temperature and RH responses of Moso bamboo panels were monitored. Then a coupled transient heat and moisture transfer numerical simulation at the material level was conducted to predict and validate the hygrothermal performance of Moso bamboo. A sensitivity study of the hygrothermal properties of bamboo was also presented to indentify the influence of each hygrothermal property of Moso bamboo. Major findings include the following aspects. Both experiment and simulation results appear to be consistent with the results of measurements of the basic hygrothermal parameters. The parametric study found that density can be regarded as the most sensible parameter to influence the temperature simulation results at the transient state, while the thermal conductivity dominated the temperature variation at the steady state. The water vapour diffusion resistance factor can be regarded as the most critical parameter to influence the RH simulation results. The influence of liquid water diffusivity is negligible in this study. The parametric study results indicated that the simulation with moisture is more accurate than the simulation without moisture in both equilibrium and transient state. The results also imply that the existence of moisture could increase the heat capacity and reduce the thermal conductivity. The results of this study recommend that the external part of the bamboo culm wall can be utilised to minimise the RH variation of the panel while the internal part of the bamboo culm wall is suitable to increase the thermal insulation performance of the panel. To avoid hygroexpansion, the implementation of external part of bamboo culm wall needs to be minimised.

La zone d'enrobage des aciers des structures en béton armé est soumise au cours de la vie de l'ouvrage à l'action de divers agents agressifs (ions chlorure, dioxyde de carbone, etc.) qui sont susceptibles d'entraîner la corrosion des armatures. Dans le cadre de la maintenance de l'ouvrage, une réparation du béton dégradé est généralement imposée afin d'assurer l'intégrité et la sécurité de la structure, et d'en allonger la pérennité. Cette étude s'attache à explorer les transferts hydriques qui limitent l'efficacité de la réparation au cours de l'hydratation du mortier de réparation. L'évolution microstructural et les profils hydriques sont obtenus par des techniques non-destructives comme l'imagerie résonance magnétique (IRM) et la gamma-densimétrie (GD) depuis très jeune âge à 28 jours. La durabilité du béton réparé est concernée. L'effet du séchage est évité dans cette étude. Le mortier isolé d'une même formulation est préparé pour la comparaison du comportement d'hydratation avec le mortier de réparation. Des diverses techniques classiques aident de compléter les résultats obtenus par IRM et GD. Donc le système de réparation est désigné. Les transferts hydriques à l'interface sont visualisés pendant la réparation (0 - 28 jours), afin de permettre une exploration en profondeur sur les mécanismes des couplages physico-chimiques. La réparation plus efficace donc est déterminée par cette méthodologie, en étudiant divers matériaux de réparation, divers états de support (saturé ou séché) et divers conditions environnementaux, etc. De plus, après la réparation (1 - 2 mois), la porosité totale est mesurée par GD ou la porosimétrie par l'intrusion de mercure (PIM). La distribution poreuse est aussi examinée par PIM selon la hauteur du système de réparation. Les indicateurs de durabilité (Cl- et CO2) après la réparation (> 2 mois) présentent l'empêchement de pénétration des ions chlorures et un effet non-évident pour la pénétration du dioxyde de carbone. L'évolution est suivie au fur et à mesure pendant la pénétration, afin d'explorer l'efficacité de la réparation qui s'adresse à une vie de service prolongée. Cette méthodologie pourra être appliquée aussi sur des autres systèmes, où il existe des transferts hydriques. Par exemple, une couche de protection en Béton Fibré à Ultra-haute Performance (BFUHP) sur le béton ordinaire. En conclusion, cette méthodologie en combinant des techniques non-destructifs et destructifs, est un outil d'étudier le système de réparation par un moyen systématique et quantitatif. C'est intéressant de comparer des divers cas. L'efficacité de réparation est étudiée afin d'assurer une durabilité à long terme / The coating area of steel reinforced concrete structures is subjected during service life time to various aggressive agents (carbon dioxide, chloride ions, etc.), which causes corrosion of steel rebars. Concerning the maintenance, repair works of degraded concrete cover are generally imposed to ensure its integrity and structural safety, and to extend long-term durability. This research aims in exploring moisture transfers which limit the efficiency of repair work during mortar hydration. Microstructure evolution and water profiles are obtained by non-destructive techniques such as Magnetic Resonance Imaging (MRI) and Gamma-Ray Attenuation (GRA) since casting until 28 days. The durability of repaired concrete is involved after the repair procedure. The effect of drying is avoided in this research. Sealed mortar of the same formula is prepared to compare its hydration performance with the repair mortar. Various conventional techniques help to supplement the results obtained by MRI and GRA. The configuration of designed repair systems is shown. Moisture transfers at the interface between the repair mortar and the old concrete are investigated during the repair procedure (0 - 28 days), which allows exploring the mechanisms of physico-chemical couplings. Efficient repair work can be determined for various repair materials, various substrates (initially-saturated or initially-dried), various environmental conditions, etc. Furthermore, total porosity is measured by GRA or by Mercury Intrusion Porosimetry (MIP) after the repair procedure (1 - 2 months). Pore size distribution (PSD) is also investigated by MIP at different positions within the repair systems. Durability indicators (Cl- and CO2) after the repair procedure (> 2 months) present a prevention of chloride penetration and a non-evident influence on carbonation. Evolution is followed during penetration, in order to explore repair efficiency during prolonged service life time. This methodology could also be applied on various systems where exist moisture transfers. For example, a protective layer of Ultra High Performance Fiber-Reinforced Concrete (UHPFRC) on conventional concrete. In conclusion, this methodology is a tool to investigate the repair systems in a systematic and quantitative way, by combining non-destructive and destructive techniques. It is interesting to compare aforementioned systems. Repair efficiency is investigated in order to ensure a long-term durability

Energy price are on the way up to a high level that will not diminish in the future make us to focus more on the sustainable development for a better solution of residential houses. Passive house or low energy housing are one of the solution to make residential more environment friendly, in same time it´s a financial security using less energy, and saving money. The last 10 years in Germany and all around Europe the concept of passive house been developed, and people aim to know more about these concept that leading the market more attractive for passive houses. A passive house is a well designed building highly insulated and air tight with mechanical ventilated system for the whole building envelope that minimizes the use of energy for heating [1]. The housing company Mimer has chosen to invest in low energy consumption in every new housing project.  These future plan projects are decided to use less than 75 kwh per square meter annually in purchased energy [2]. This thesis is about new constructed passive houses, and focuses on the evaluations of the temperature, and moisture condition for attic, external walls and joist. Reason for doing this investigation is to see if passive houses fulfill the building codes regarding moisture, and temperature changes, and to find in early stage suspicious changes that could affect badly on the building envelop. The aim of this study is -         Moisture risk analyses of the attic, external walls and joist -         Studying temperature analysis   With highly insulated walls the risk for moistures extra sensitive than normal building construction.  Also during summer time the comfort inside may be surprised by high indoor temperature and one solution for that could be using sun shading.