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Power-Based Two-Ports with Application to HVAC Systems

Time: Thu 2022-06-09 10.00

Location: Munin, Teknikringen 8, Stockholm

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Language: English

Subject area: Vehicle and Maritime Engineering

Doctoral student: Mina Wagih Nashed , Farkostteknik och Solidmekanik

Opponent: Professor Antonio Torregrosa, Universitat Politècnica de València, Spanien

Supervisor: Hans Bodén, Linné Flow Center, FLOW, Competence Center for Gas Exchange (CCGEx), Farkostteknik och Solidmekanik

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QC 220519


The understanding of acoustic wave propagation in ducts or pipes is essential for all applications involving fluid machines, e.g., fans, pumps, and compressors. Over the years different methods have been developed to simulate wave propagation in duct networks. The existence of accurate simulation methods saves effort and time in the design phase and can prevent noise problems after implementation. One common type of duct network used in buildings and vehicles is Heating-Ventilation and Air-Conditioning or HVAC systems. Traditionally the so-called “Source-Path-Receiver” method is used in such systems. This method is based on analyzing the flow of acoustic power from the source through a system. This approach is valid when a large number of waves are propagating in a duct or for sufficiently high frequencies. The method neglects reflections, starts from the source sound power, subtracts the attenuation of each element and adds its flow generated noise. In an attempt to further developing and improving the “Source-Path-Receiver” method; a power-based two-port method is proposed in this thesis. The proposed method is developed first to comply with the standard “Source-Path-Receiver” methods as described in ASHRAE and VDI standards. The newly proposed method can include the effect of both reflection and transmission for all elements via a scattering matrix. In order to demonstrate when and to what extent this can be important, a study using power-based two-ports is conducted on purely reflective networks and with mixed reflective and dissipative networks.