Abstract
Turbine generators operate with complex cooling systems due to the challenge in controlling the peak temperature of the stator bar caused by Ohm loss, which is unavoidable. Therefore, it is important to characterize and quantify the thermal performance of the cooling system. The focus of the present research is to investigate the heat transfer and pressure loss characteristics of a typical cooling system, the so-called stator ventilation duct. A real scale model was built at its operating conditions for the present study. The direction of cooling air was varied to consider its operation condition, so that there are: (1) outward flow; and (2) inward flow cases. In addition, the effect of (3) cross flow (inward with cross flow case) was also studied. The transient heat transfer method using thermochromic liquid crystals is implemented to measure full surface heat transfer distribution. A series of computational fluid dynamics (CFD) analyses were also conducted to support the observation from the experiment. For the outward flow case, the results suggest that the average Nusselt numbers of the 2nd and 3rd ducts are at maximum 100% and 30% higher, respectively, than the inward flow case. The trend was similar with the effect of cross flow. The CFD results were in good agreement with the experimental data.
Highlights
The increasing demand for electric energy drives the need for bigger power generation systems, in general
The present study focuses on evaluating the full surface heat transfer and pressure loss of stator ventilation ducts of air-cooled turbine generators using experimental and computational fluid dynamics (CFD) approaches
This paper presents experiments and CFD analysis to investigate the full surface heat transfer coefficient and pressure loss characteristics of the stator ventilation duct of a turbine generator
Summary
The increasing demand for electric energy drives the need for bigger power generation systems, in general. It continuously requires larger capacity turbine generators with higher efficiency. One of the key challenges is to control the peak temperature of the generator caused by Ohmic loss, which is unavoidable. The peak temperature of a generator should typically be maintained below 130 °C. Depending on overall heat removal and installation requirement, air or hydrogen is used for the cooling medium. Air is preferred for its availability and safety to handle compared to hydrogen. Hydrogen offers much higher heat capacity, so it is the choice for the requirements of the highest heat removal
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