Bachelor's thesis Laura Maria Maier


Overall Energetic Examination and Economic Analysis of Air Handling Units

An established program which allows the calculation of the useful energy demand per hour of a HVACsystem is expanded by the systemīs supply chain, its distribution and generation components. The existing program enables the calculation of the useful energy demand of an exemplary HVAC system which is based on weather data of German TRY for different locations and usage profiles. As the supply chainīs influence on the total energy demand of the HVAC system is significant, the respective calculationmethods are added to the program. Thus, the HVAC-system is evaluated on a global level.
This thesis focusses on the interaction of the heat and cold generation systems and their hydraulic connection to the HVAC system. The existing program is written in the programming language VBA ("Visual Basis for Applications") and integrated inMicrosoft Excel 2010.
The refrigeration capacity is generated by an idealized compression refrigeration machine. Heat is supplied by different types of boilers and an idealized heat pump. In addition, the dependance of the generating componentsī performance on the supply and return temperatures of the distribution network is integrated in the calculation procedures of the program. Therefore, the program allows to estimate the final energy demand of the components of the generation system as well as the pumps in the distribution network and the air handling unit.
Based on these calculation procedures, an overall energetic and economic analysis of the HVAC system is performed, focusing on the final energy demand of the respective components. The economic analysis is realised by evaluating the life-cycle costs of the HVAC system based on the annuity method. Apart from that, the influence of a varying water supply temperature and temperature difference between supply and return temperature is evaluated. It appears that an increasing supply temperature has a positive influence on the cooling machineīs efficiency while the heat pumpīs drive power increases. An increase in the temperature difference between supply and return temperature leads to an increase in both the heat pumpīs and the cooling machineīs efficiency.
Finally, the use of an air washer is compared to the use of a finned heat exchanger taking into account their different pressure drops in the water and air distribution network and their influence on the performance of the total system is evaluated. This comparison reveals that the use of an air washer can lead to possible savings in the final energy demand of the system if certain boundary conditions are met.