Reduction of pressure losses in air handling units

  • Druckverlust Reduzierung in raumlufttechnischen Anlagen

Azem, Abdul; Müller, Dirk (Thesis advisor); Kriegel, Martin (Thesis advisor)

Aachen (2018, 2019)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2018


This work focuses on airside pressure losses in air handling units (AHUs). For this reason, the effect of air velocity on pressure losses and component energy efficiency in order to reduce operating costs were investigated. First, key figures, relevant to the evaluation of AHUs were introduced. Then, the most common components used in modern AHUs were presented, along with their special properties. Subsequently, the current norm guidelines and legal regulations for AHUs and their implications were explained. Next, a literature and patent search that included an analysis of component sales figures between 2014 and 2017 was carried out. This analysis made it possible to identify AHU assemblies that show potential for optimisation and identified those components where optimisation would only have a minor effect on AHU efficiency. Following this analysis, a method for determining the economically most advantageous air velocity in AHUs was developed, based on dynamic simulations. This revealed that the optimum air velocity in AHUs is a function of air volume flow, daily operating time, expected lifetime and energy price, while the location only plays a subordinate role. Thereafter, investigations were carried out to optimise AHU components. During the investigation, two very promising optimisation measures were developed. First, a heat exchanger with an optimal bypass that is dimensioned as a function of the expected annual operating hours; and second, a cubic silencer that functions as a pressure regain unit (PRU) and is placed directly downstream of the fan. Finally, a real test AHU was designed specifically for the investigations of the airside pressure losses. The designed test AHU had several modules, each of which contained only one component. This modular design allowed quick switching between the different setups that were being examined. In these investigations regular modules, as well as modules with optimised components (cooler with bypass and PRU) were analysed. The main finding of the tests was that the theoretically calculated advantages of the optimised components could also be proven under realistic test conditions.


  • E.ON Energy Research Center [080052]
  • Chair of Energy Efficient Buildings and Indoor Climate [419510]