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.

This thesis is a study of an indirect heat pump assisted solar domestic hot water (I-HPASDHW) system, where the investigated configuration is called the Dual Side I-HPASDHW system. The study outlines the development of an Experimental Test Unit (ETU), and focuses on the experimental validation of TRNSYS models. Shortcomings of the system design realized throughout the validation process, as well as weaknesses in the control schemes used to operate the system are also provided. A description of the Dual Side I-HPASDHW system is provided along with the design intent of the system. The corresponding ETU is presented in detail to provide a comprehensive understanding of the ETU’s simulation capabilities. Components of the ETU, such as the heat pump, heat exchanger, and domestic hot water (DHW) tank are characterized in order to provide input data for built-in TRNSYS models, and to develop custom TRNSYS models for the heat pump and heat exchanger. Heat exchanger performance is modelled with a linear correlation, while the heat pump performance is mapped by applying experimental data to three-dimensional surface fitting software. For the purpose of validation, the ETU is used to simulate the performance of the Dual Side I-HPASDHW system under a realistic control scheme. Four full day tests are conducted using data from a fall, winter, and summer day. The full day summer test is repeated with and without electrical backup heating. The TRNSYS model of the Dual Side system is tuned in order to provide the closest match possible between the computer simulation and the measured performance of the ETU. Experimental tests were compared with TRNSYS simulations to reveal some disparity in the results. The majority of simulation error was attributed to inaccuracy in modeling DHW tank temperatures and water circulation patterns. The disparity created by the DHW tank model only resulted in substantial performance deviation when inaccurate DHW temperatures were used directly for vital control decisions. Conclusions were drawn suggesting that the TRNSYS model of the ETU was valid for a majority of operating conditions, often matching experimental tests well within experimental uncertainty. Caution was recommended towards the use of the developed TRNSYS model, where techniques were recommended for tracking and minimizing substantial simulation errors. Several key performance issues affecting the Dual Side I-HPASDHW system were targeted with recommendations for design and control alterations, along with future improvement and optimization studies.

A volumetric contact dynamics model has been proposed by Gonthier et al. [1, 2, 3] for the purpose of rapidly generating reliable simulations of space-based manipulator contact dynamics. By assuming materials behave as a Winkler elastic foundation model, forces and moments between two bodies in contact can be expressed in terms of the volume of interference between the undeformed geometries of the bodies. Friction between bodies is modelled by a dwell-time dependent bristle model for both tangential friction, and spinning friction torque. This volumetric model has a number of advantages. Unlike point-contact models, it allows for the modelling of contact between complex geometries and scenarios where the contact surface is relatively large, while being less computationally expensive than finite element methods. Rolling resistance is included in the model through damping effects across the volume of interference. The friction model accounts for dwell-time dependent slip-stick effects, spinning friction torque, and the Contensou effect. In this thesis, an experimental validation of the volumetric contact model is presented for the first time. Models for simple geometries in contact (e.g. cylinder-on-plane, sphere-on-plane) have been developed for stationary contact and for contact with motion normal and tangential to the contact surface. Tangential motion is modelled with pure translation, pure rotation about the normal axis, and combined motion, in order to separately consider friction forces, spinning friction torque, and the Contensou effect, respectively. An apparatus has been developed to experimentally validate these models for metal-on-metal contact. The apparatus has two configurations, one for validating the normal contact models and the other for the friction models. Experimental measurements of forces and displacements are used to identify model parameters (e.g. volumetric stiffness, friction coefficients, etc.). For normal force experiments, modelling the contact forces as proportional to volume of interference was found to be a reasonable approximation. A Hertzian model was compared with the volumetric model for spherical payloads loaded quasi-statically. Using stiffnesses estimated from spherical experiments, small misalignments of the cylindrical payloads were estimated that corresponded well with measured results. Dynamic experiments suggest an inverse relationship between impact velocity and the hysteretic damping coefficient. The high normal forces applied in the friction experiments were found to create significant wear on the contact surfaces. Coefficients of friction between titanium and aluminum were found to be consistent translationally and rotationally. Friction forces from combined translation and rotation demonstrate that the Contensou effect is accurately described by the volumetric contact model.

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.

Keywords: EAC, full-scale experimental Validation, ABRI Lab, VRV The VRV air-conditioning system has been gaining overwhelming popularity in recent years due to its superb merits such as high energy efficiency, lower power consumption, low noise and increasing thermal comfort. During last phase of study, computer simulation using the DOE 2.1 as a tool has been performed systematically to establish a calculation equation for the EAC for Green Building Evaluation Indexes, in replacing the currently adapted fixed constant of 0.8. It is the goal of this year¡¦s project to further validate this equation by conducting a series of full-scale experiments at the ABRI Tainan Laboratory. The experimental result will be organized as a model to revise the equations established during last phase of study with good accuracy. Various different VRV systems which were commercially available on the local air-conditioning market will be adapted so that comparative study can be performed among them. The IPLV curves, which are the essential performance curve of each specific VRV system will then be obtained under local weather conditions. It is expected that through the execution of this project, the calculation equation of the VRV system to be adapted in the Green Building EAC evaluation index will be finalized and validated by the full-scale experiments. The test facilities established during this phase of study will then become the most suitable location of similar tests when building energy conservation is concerned.

A volumetric contact dynamics model has been proposed by Gonthier et al. [1, 2, 3] for the purpose of rapidly generating reliable simulations of space-based manipulator contact dynamics. By assuming materials behave as a Winkler elastic foundation model, forces and moments between two bodies in contact can be expressed in terms of the volume of interference between the undeformed geometries of the bodies. Friction between bodies is modelled by a dwell-time dependent bristle model for both tangential friction, and spinning friction torque. This volumetric model has a number of advantages. Unlike point-contact models, it allows for the modelling of contact between complex geometries and scenarios where the contact surface is relatively large, while being less computationally expensive than finite element methods. Rolling resistance is included in the model through damping effects across the volume of interference. The friction model accounts for dwell-time dependent slip-stick effects, spinning friction torque, and the Contensou effect. In this thesis, an experimental validation of the volumetric contact model is presented for the first time. Models for simple geometries in contact (e.g. cylinder-on-plane, sphere-on-plane) have been developed for stationary contact and for contact with motion normal and tangential to the contact surface. Tangential motion is modelled with pure translation, pure rotation about the normal axis, and combined motion, in order to separately consider friction forces, spinning friction torque, and the Contensou effect, respectively. An apparatus has been developed to experimentally validate these models for metal-on-metal contact. The apparatus has two configurations, one for validating the normal contact models and the other for the friction models. Experimental measurements of forces and displacements are used to identify model parameters (e.g. volumetric stiffness, friction coefficients, etc.). For normal force experiments, modelling the contact forces as proportional to volume of interference was found to be a reasonable approximation. A Hertzian model was compared with the volumetric model for spherical payloads loaded quasi-statically. Using stiffnesses estimated from spherical experiments, small misalignments of the cylindrical payloads were estimated that corresponded well with measured results. Dynamic experiments suggest an inverse relationship between impact velocity and the hysteretic damping coefficient. The high normal forces applied in the friction experiments were found to create significant wear on the contact surfaces. Coefficients of friction between titanium and aluminum were found to be consistent translationally and rotationally. Friction forces from combined translation and rotation demonstrate that the Contensou effect is accurately described by the volumetric contact model.

This thesis is a study of an indirect heat pump assisted solar domestic hot water (I-HPASDHW) system, where the investigated configuration is called the Dual Side I-HPASDHW system. The study outlines the development of an Experimental Test Unit (ETU), and focuses on the experimental validation of TRNSYS models. Shortcomings of the system design realized throughout the validation process, as well as weaknesses in the control schemes used to operate the system are also provided. A description of the Dual Side I-HPASDHW system is provided along with the design intent of the system. The corresponding ETU is presented in detail to provide a comprehensive understanding of the ETU’s simulation capabilities. Components of the ETU, such as the heat pump, heat exchanger, and domestic hot water (DHW) tank are characterized in order to provide input data for built-in TRNSYS models, and to develop custom TRNSYS models for the heat pump and heat exchanger. Heat exchanger performance is modelled with a linear correlation, while the heat pump performance is mapped by applying experimental data to three-dimensional surface fitting software. For the purpose of validation, the ETU is used to simulate the performance of the Dual Side I-HPASDHW system under a realistic control scheme. Four full day tests are conducted using data from a fall, winter, and summer day. The full day summer test is repeated with and without electrical backup heating. The TRNSYS model of the Dual Side system is tuned in order to provide the closest match possible between the computer simulation and the measured performance of the ETU. Experimental tests were compared with TRNSYS simulations to reveal some disparity in the results. The majority of simulation error was attributed to inaccuracy in modeling DHW tank temperatures and water circulation patterns. The disparity created by the DHW tank model only resulted in substantial performance deviation when inaccurate DHW temperatures were used directly for vital control decisions. Conclusions were drawn suggesting that the TRNSYS model of the ETU was valid for a majority of operating conditions, often matching experimental tests well within experimental uncertainty. Caution was recommended towards the use of the developed TRNSYS model, where techniques were recommended for tracking and minimizing substantial simulation errors. Several key performance issues affecting the Dual Side I-HPASDHW system were targeted with recommendations for design and control alterations, along with future improvement and optimization studies.

No description available.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The water utilized by passive air-conditioning systems in buildings is typically required at higher elevations. The thermally driven natural circulation water pump (TDNCWP) is a passively driven pumping system for delivering water from ground level against gravity to a higher elevation. It consists of a humid air closed duct loop to which a temperature difference is applied, resulting in a density gradient driven flow. A hot water evaporation tray inside the loop at ground level introduces water vapour to the loop air flow, and a cold condensation plate inside the loop at the elevated level removes this water vapour for passive airconditioning usage. In this thesis, a one-dimensional theoretical and numerical simulation model is developed. Experiments were conducted on two experimental TDNCWP set-ups of different cross sectional areas to evaluate the pump design and the theoretical model. It is shown in this thesis that the TDNCWP can provide water at varied elevations using non-mechanical, passive means. A temperature difference of 9 to 12.5 °C induced an average velocity of 0.4 to 0.6 m/s for a duct cross section of 100 mm2. For a larger cross section of 400 mm2, a temperature difference of 2 to 5 °C induced an average velocity of 0.25 to 0.3 m/s. An asymmetrical velocity profile was observed which varied at different points in the loop. A water delivery rate of 1.2 to 7.5 L/day was experimentally determined which compares well to the passive air-conditioning water requirements of a small building. The theoretical model over-predicted the delivery rate at increased duct cross sectional areas but fared well when compared to the smaller experimental model results. Further refinement of the numerical model and the TDNCWP design is required, and recommendations were made regarding this. It is clear however that the TDNCWP provides an alternative to a conventional water pump for low-volume water pumping requirements. / AFRIKAANSE OPSOMMING: Die water wat gebruik word deur passiewe lugversorgingstelsels in geboue word tipies benodig op hoër vlakte. Die termies gedrewe natuurlike sirkulasie waterpomp (TDNCWP) is ʼn passiewe gedrewe pomp stelsel vir die lewering van water vanaf die grondvlak teen swaartekrag na ʼn hoër vlak. Dit bestaan uit 'n vogtige geslote lug geut siklus waarop ʼn temperatuur verskil toegepas word, dit lei tot vloei gedrewe deur ʼn digtheids gradiënt. ʼn Warm water verdampings-pan binne die geut op grondvlak stel waterdamp aan die geut lugvloei toe, en ʼn koue kondensasie plaat binne die geut op die verhoogde vlak verwyder hierdie waterdamp vir passiewe lugversorgings gebruik. In hierdie tesis word ʼn eendimensionele teoretiese en numeriese simulasie model ontwikkel. Eksperimente is uitgevoer op twee eksperimentele TDNCWP stelsels van verskillende deursnee grootes om die pomp ontwerp en die teoretiese model te evalueer. Die tesis dui aan dat die TDNCWP water kan voorsien teen verskillende hoogtes op ʼn nie-meganiese, passiewe wyse. ʼn Temperatuur verskil van 9 tot 12.5 °C veroorsaak ʼn gemiddelde snelheid van 0.4 tot 0.6 m/s vir ʼn geut deursnit van 100 mm2.Vir ʼn groter deursnit van 400 mm2, het ʼn temperatuur verskil van 2 tot 5 °C ʼn gemiddelde snelheid van 0.25 tot 0.3 m/s veroorsaak. ʼn Asimmetriese snelheidsprofiel was waargeneem wat gewissel het op verskillende punte in die siklus. ʼn Water voorsienings tempo van 1.2 tot 7.5 L / dag was eksperimenteel waargeneem wat goed vergelyk met die passiewe water lugversorging vereistes van 'n klein gebou. Die teoretiese model het ʼn groter voorsienings tempo voorspel vir die groot deursneë, maar het goed gevaar in vergelyking met die kleiner eksperimentele model. Verdere verfyning van die numeriese model en die TDNCWP ontwerp word vereis, en aanbevelings is gemaak ten opsigte van hiervan. Dit is egter duidelik dat die TDNCWP ʼn alternatief is vir konvensionele lae-volume water pomp applikasies. / National Research Foundation (NRF)

Automotive structures contain hundreds of welds. Most of the time, failure occurs at the weld ends (weld toe or weld root). Thus, welds affect the structural integrity of an entire structure. Thus, the modeling of welded joints is very important from a design point of view. In this research, the primary aim is to develop a weld model to assess the structural integrity of welded joints based on stress analysis by using a finite element method (FEM) and through experimental validation. The stress distribution in welded joints mainly depends on the geometry, loading type and material properties. Therefore, it is greatly challenging to develop a weld model that can predict the behavior of stress distribution and weld stiffness in joints. There are several approaches for modeling welded structures by using FEM. However, the effective notch stress approach has been used for weld joint modeling in this research which is gaining in popularity in the automotive industry. The effective notch stress approach calculates the local stress at a notch (weld toe or root) assuming that there is linear-elastic material behavior. Parameter tuning of the weld model has been done to obtain the lowest validation error with the experimental results. The effective notch radius is chosen as the only tuning parameter in this weld model. Through this investigation, the weld model based on the effective notch stress has been experimentally validated for the first time through parameter tuning. Two different types of welded joints are investigated. Both types of joints are analyzed with a fine meshed 3D finite element model by using the effective notch stress approach. The FEM model of these two joints is validated with the experimental results. The calculated FEM results show a good agreement with the experimental results (obtained by using strain gages) for the ASTM model. This modeling technique is also validated with real world data of a bus window pillar. The model of the bus window pillar shows a close approximation with the experimental results. / October 2016