M.Tech. (Architectural Technology) / It is estimated that commercial buildings are responsible for 5.4% of worldwide Green House Gas (GHG) emissions through their construction and on-going operation. In developed countries this figure can go up to 30%. The environmental control industry is one of the large consumers of this energy. Heating, ventilation and air conditioning (HVAC) contribute approximately 15% of South Africa's current peak electrical demand consumption according to Eskom (the South African electricity utility). The purpose of this dissertation is to analyse and evaluate methods to reduce the energy consumption of the HVAC system in a commercial office building. This encompasses careful building design to reduce heat loads and promote the circulation of fresh air; the use of energy-efficient air-conditioning systems and the incorporation of materials and technology to reduce energy consumption. This will be based upon a case study of the new SANRAL (South African National Roads Agency Limited) head office building in Val-DeGrace, Pretoria. A deductive research approach will be followed. The as-designed Actual Building is modelled with the appropriate energy modelling software and its annual energy usage is obtained. A benchmark based Notional Building complying with SANS 204:2008 criteria of the same size, shape, location and operational schedules as the Actual Building is also modelled and its energy usage results compared to that of the Actual Building. This comparison will determine how energy efficient the Actual Building's HVAC system is compared to a conventional Notional Building. Quantitative data collection is performed by empirical measurement of the energy usage of the as-built Actual Building. The raw data (power usageofthe HVAC system) is measured by Schneider Electric PM9c™ power meters located in the HVAC distribution boards of the building. This raw data are collected by Schneider Electric's ION Enterprise' power management software which has a user friendly interface from where the data can be downloaded. The power management software is connected to an ANDOVEWM Building Management System (BMS). Due to commissioning procedures and the timeframe at hand for the completion of this dissertation measurements could only be taken over a 7 month period. Operational data were measured from July 2011 to March 2012 thus accounting for summer, winter and a seasonal changeover period. The modelled energy usage results of the as-designed Actual Building are compared to the measured energy usage data obtained from the as-built Actual Building. This comparison serves to evaluate the accuracy of the software model...

This thesis details a study of strategies used to limit the flow generated noise encountered in the outlet diffusers of high velocity heating, ventilation and air conditioning (HVAC) duct systems. The underlying noise rating criterion is drawn from the specifications covering ocean going aluminium fast ferries. Although directed primarily towards the fast ferry industry the results presented herein are applicable to other niche high velocity HVAC applications. Experimental tests have been conducted to prove the viability of a high velocity HVAC duct system in meeting airflow requirements whilst maintaining acceptable passenger cabin noise levels. A 50 mm diameter circular jet of air was expanded using a primary conical diffuser with a variety of secondary outlet configurations. Noise measurements were taken across a velocity range of 15 to 60 m/s. An optimum outlet design has been experimentally identified by varying the diffuser angle, outlet duct length and the termination grill. A 4 to 5 fold reduction in required duct area was achieved with the use of a distribution velocity of 20 to 30 ms-1, without exceeding the prescribed passenger cabin noise criteria. The geometric configuration of the diffuser outlet assembly was found to have a pronounced effect on the noise spectrum radiating from the duct outlet. The development of a numerical model capable of predicting the flow induced noise generated by airflow exiting a ventilation duct is also documented. The model employs a Large Eddy Simulation (LES) CFD model to calculate the turbulent flow field through the duct diffuser section and outlet. The flow-generated noise is then calculated using a far field acoustic postprocessor based on the Ffowcs-Williams and Hawkings integral based formulation of Lighthill???s acoustic analogy. Time varying flow field variables are used to calculate the fluctuating noise sources located at the duct outlet and the resulting far field sound pressure levels. This result is then used to calculate the corresponding far field sound intensity and sound power levels. The numerical acoustic model has been verified and validated against the measured experimental results for multiple outlet diffuser configurations.

This thesis details a study of strategies used to limit the flow generated noise encountered in the outlet diffusers of high velocity heating, ventilation and air conditioning (HVAC) duct systems. The underlying noise rating criterion is drawn from the specifications covering ocean going aluminium fast ferries. Although directed primarily towards the fast ferry industry the results presented herein are applicable to other niche high velocity HVAC applications. Experimental tests have been conducted to prove the viability of a high velocity HVAC duct system in meeting airflow requirements whilst maintaining acceptable passenger cabin noise levels. A 50 mm diameter circular jet of air was expanded using a primary conical diffuser with a variety of secondary outlet configurations. Noise measurements were taken across a velocity range of 15 to 60 m/s. An optimum outlet design has been experimentally identified by varying the diffuser angle, outlet duct length and the termination grill. A 4 to 5 fold reduction in required duct area was achieved with the use of a distribution velocity of 20 to 30 ms-1, without exceeding the prescribed passenger cabin noise criteria. The geometric configuration of the diffuser outlet assembly was found to have a pronounced effect on the noise spectrum radiating from the duct outlet. The development of a numerical model capable of predicting the flow induced noise generated by airflow exiting a ventilation duct is also documented. The model employs a Large Eddy Simulation (LES) CFD model to calculate the turbulent flow field through the duct diffuser section and outlet. The flow-generated noise is then calculated using a far field acoustic postprocessor based on the Ffowcs-Williams and Hawkings integral based formulation of Lighthill???s acoustic analogy. Time varying flow field variables are used to calculate the fluctuating noise sources located at the duct outlet and the resulting far field sound pressure levels. This result is then used to calculate the corresponding far field sound intensity and sound power levels. The numerical acoustic model has been verified and validated against the measured experimental results for multiple outlet diffuser configurations.

Past research has shown that natural ventilation can be used to satisfy upwards of 98% of the yearly cooling demand when utilized in the appropriate climate zone. Yet widespread implementation of natural ventilation has been limited in practice. This delay in market adoption is mainly due to lack of effective and reliable control. Historically, control of natural ventilation was left to the occupant (i.e. they are responsible for opening and closing their windows) because occupants are more readily satisfied when given control of the indoor environment. This strategy has been shown to be effective during summer months, but can lead to both over and under ventilation, as well as the associated unnecessary energy waste during the winter months. This research presents the development and evaluation of a model-based control algorithm for natural ventilation. The proposed controller is designed to modulate the operable windows based on ambient temperature, wind speed, wind direction, solar radiation, indoor temperature and other building characteristics to ensure adequate ventilation and thermal comfort throughout the year without the use of mechanical ventilation and cooling systems. A midrise student dormitory building, located in Portland OR, has been used to demonstrate the performance of the proposed controller. Simulation results show that the model-based controller is able to reduce under-ventilated hours to 6.2% of the summer season (June - September) and 2.5% of the winter (October - May) while preventing over-heating during 99% of the year. In addition, the model-based-controller reduces the yearly energy cost by 33% when compared to a conventional heat pump system. As a proactive control, model-based control has been used in a wide range of building control applications. This research serves as proof-of-concept that it can be used to control operable windows to provide adequate ventilation year-round without significantly affecting thermal comfort. The resulting control algorithm significantly improves the reliability of natural ventilation design and could lead to a wider adoption of natural ventilation in appropriate climate zones.