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Water hammer analysis

This case study demonstrates the capability of Flownex to simulate the water hammer effect by simulating the sudden closure of a valve at the outlet of a long pipe in which water is flowing. In practice, this closure could be facilitated by a fast acting valve or similar device. The model takes the fluid and pipe wall elasticity into account.

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Turbine protection - Two phase flow regimes

The main challenge explored in this case study is the root cause analysis of dynamically hazardous movements in the distillate lines to a plant deaerator. Flownex's simulation optimization tool was used to determine the preferred two phase flow regime. By using Flownex to identify the cause, it was possible to mitigate a commercial impact on the project, maintain the planned commissioning schedule and improve the existing plant design thereby also removing the safety risk of unwanted dynamic line movements.

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Transient Simulation of a Two-Stage Air Cycle Chiller

This case study demonstrates the transient operation of a two-stage Air Cycle Chiller. The chiller consists of a closed cycle in which dry air is circulated via a set of centrifugal compressors and expanded through a turbine to provide cooling at very low temperatures. A typical application is in crust freezing of pre-baked foods.

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Boiler Header Cracking Investigation

This Case Study describes how Steinmüller used Flownex to dynamically simulate the flow and heat transfer over the platen evaporator and determine the possible reasons for header cracking.
As part of the repowering of a power station Steinmüller is tasked with the optimization of the boiler sub-system. This included a study to determine the reasons for regular Platen Evaporator header cracking. Platen Evaporator Header cracking in the boiler can cause unnecessary and costly down time due to maintenance of the power plant. Steinmüller used Flownex to dynamically simulate the flow and heat transfer over the platen evaporator and determine the possible reasons for header cracking.
 
Flownex proved that with its two-phase capabilities, momentum conservation, and ability to simulate dynamically the seemingly complex model of the platen evaporator was handled quickly and efficiently providing engineers with dynamic graphs of the flow within the evaporator tubes and the effects brought on by phase change.
 
From this study the source of oscillations were isolated along with other factors that could have caused the headers to crack i.e. mal temperature distribution that will lead to buckling of the platen evaporator.
 
This allowed the company to make decisions on how optimize this sub-system and reduce header cracking. 

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Regulator temperature analysis

Pressure regulators are to be employed at a gas-fired power station to reduce upstream gas pressures from a maximum of 15 MPa to approximately 3.5 MPa. Due to the Joule-Thompson effect, the resulting gas temperature drops could be in the region of 55 °C. The dew-point temperature of the hydrocarbons (gas) flowing through is -15 °C, and the minimum ambient temperature of the area is -6 °C. Thus, the regulators could potentially be subjected to gas at -61 °C at start-up. According to the valve manufacturer, temperatures as low as -20 °C can be tolerated for some time, provided that condensation does not occur. 

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