Evaluation of empirical heat transfer models using TFG heat flux sensors

The development and validation of mechanistic boiling heat transfer models has been a focal point in the efforts to improve the efficiency and profitability of power generation systems, e.g. nuclear reactors. The primary goal of these models is improving the accuracy of boiling heat transfer simulations and reducing the uncertainty margins that affect both the design and the safety of a system. However, the emergence of these models has also stimulated the need for high-fidelity experiments and experimental data for validation and verification. In this work we present first-of-a-kind data of heat flux partitioning in boiling heat transfer, obtained using cutting-edge diagnostics and post-processing techniques. A HSV camera was used to visualize the boiling surface at 10,000 frames per second with simultaneous front and side views of the two-phase flow. A high-speed IR camera was used to capture the 2-D radiative signal from the boiling surface to visualize bubble nucleation, growth and detachment at a 115 μm/pixel resolution at 2,500 frames per second. A coupled radiation-conduction calibration model was used to calibrate the IR data and extract the full local temperature and heat flux distributions on the boiling surface, which enable a direct measurement of the partitioned heat fluxes. Here we report the results of investigations performed in flow boiling conditions with a mass flux of 500 kg/m2/s, at atmospheric pressure and 10 K of subcooling. These data will be leveraged to inform the development and validation of the next generation of mechanistic boiling heat transfer models, to be used in Computational Fluid Dynamics (CFD) codes for the design and the safety analysis of nuclear reactors.

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Exploration of Hands-On Discovery Pedagogy in Heat Transfer

Volume 4: Heat and Mass Transfer Under Extreme Conditions; Environmental Heat Transfer; Computational Heat Transfer; Visualization of Heat Transfer; Heat Transfer Education and Future Directions in Heat Transfer; Nuclear Energy ◽

10.1115/ht2013-17597 ◽

2013 ◽

Author(s):

Thomas E. Diller ◽

Chris Williams

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Problem Solving ◽

Conceptual Understanding ◽

Heat Energy ◽

Concept Inventory ◽

Heat Flux Sensors ◽

Hands On ◽

Authentic Problems ◽

Transfer Principles

Recent research in the development of the “Thermal and Transport Concept Inventory” test (TTCI) has shown that, despite completing several related courses, students have significant misconceptions of heat transfer principles such as the differences between heat, energy and temperature. This lack of conceptual understanding limits students’ problem-solving abilities (and thus their transition to expertise) and their ability to transfer knowledge to other courses and contexts. This research demonstrates how this problem can be addressed by integrating hands-on workshops into a traditional heat transfer lecture course. The workshops are designed to actively engage students in exploration and discovery using authentic problems. Using heat flux sensors allows students to physically observe abstract phenomena that cannot be easily observed.

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Evaluation of Heat Transfer Models With Measurements in a Hydrogen-Fuelled Spark Ignition Engine

2010 14th International Heat Transfer Conference, Volume 3 ◽

10.1115/ihtc14-22438 ◽

2010 ◽

Cited By ~ 1

Author(s):

Joachim Demuynck ◽

Sebastian Verhelst ◽

Michel De Paepe ◽

Henk Huisseune ◽

Roger Sierens

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Thermodynamic Model ◽

Internal Combustion Engines ◽

Internal Combustion ◽

Hydrogen Combustion ◽

Spark Ignition Engine ◽

Combustion Engines ◽

Combustion Properties ◽

Transfer Models

Hydrogen-fuelled internal combustion engines are still investigated as an alternative for current drive trains because they have a high efficiency, near-zero noxious and zero tailpipe greenhouse gas emissions. A thermodynamic model of the engine cycle enables a cheap and fast optimization of engine settings for operation on hydrogen. The accuracy of the heat transfer sub model within the thermodynamic model is important to simulate accurately the emissions of oxides of nitrogen which are influenced by the maximum gas temperature. These emissions can occur in hydrogen internal combustion engines at high loads and they are an important constraint for power and efficiency optimization. The most common models in engine research are those from Annand and Woschni, but they are developed for fossil fuels and the heat transfer of hydrogen differs a lot from the classic fuels. We have measured the heat flux and the wall temperature in an engine that can run on hydrogen and methane and we have investigated the accuracy of simulations of the heat transfer models. This paper describes an evaluation of the models of Annand and Woschni with our heat flux measurements. Both models can be calibrated to account for the influence of the specific engine geometry on the heat transfer. But if they are calibrated for methane, they fail to calculate the heat transfer for hydrogen combustion. This demonstrates the models lack some gas or combustion properties which influence the heat transfer process in the case of hydrogen combustion.

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