Two phase flow and phase change heat transfer in small structures

New production techniques, which became available since the 1980’s, allowed the mass production of small sized fluidic systems. Reducing the size of a technical system alters the performance due to scaling effects. Physical phenomena which operate on volumes, such as gravity and inertia, become less important with respect to physical phenomena...

Long-term unsteadiness and large-scale structures in Rayleigh-Bénard convection with and without electromagnetic forcing

This dissertation focuses on turbulent thermal convection, which occurs in a wide range of (geo)physical situations, like in the atmosphere, the oceans, the interior of stars or planets, and engineering applications, like metal casting or crystal growth processes. In this work, a special type of thermal convection, Rayleigh-Bénard convection, is...

Multiple impinging jet arrays. An experimental study on flow and heat transfer

Because of their high efficiency and their ability to provide high heat transfer rates, impinging jets are applied for rapid cooling and heating in a wide variety of industrial processes. However, the physical phenomena controlling the heat transfer from impinging jets are to a large degree unknown. The goal of the present project was to gain a...

Fluidized bed ice slurry generator for enhanced secondary cooling systems

Ice slurries are liquid solutions of a freezing point depressant in water, in which small ice crystals are present. Ice slurries are efficient secondary cooling fluids because they utilize the latent heat effect involved with the ice/water phase change. A high heat capacity is available at relatively constant temperatures, while ice slurries are...

Enhanced modelling of LAGEOS non-gravitational perturbations

Mean particle diameters: From statistical definition to physical understanding

Mean particle diameters are important for the science of particulate systems. This thesis deals with a definition system for these mean diameters, called Moment-Ratio (M-R) definition system, and provides a general statistical and physical basis. Also, the current DIN/ISO definition system is discussed. Many types of mean diameters defined...

Multi-sensor remote sensing parameterization of heat fluxes over heterogeneous land surfaces

The parameterization of heat transfer by remote sensing, and based on SEBS scheme for turbulent heat fluxes retrieval, already proved to be very convenient for estimating evapotranspiration (ET) over homogeneous land surfaces. However, the use of such a method over heterogeneous landscapes (e.g. semi-arid regions or agricultural land) becomes...

Heat Transfer in the Thick Thermoset Composites

Nowadays more and more large composites are used to replace the traditional metallic structural materials in the industries. However, for manufacturing the thick thermoset composites, the size not only influences the mechanical properties in the completed products, but also the core temperature overshoot generated during the curing reaction....

Towards a composite exhaust system: Investigation of the flow, thermal and wear resistance of an insulating, ceramic fibrous liner of combustion engine exhaust ducts and their influence on the design space

The current concerns regarding global warming and climate change in Europe and other parts of the world also influence developments in the automotive sector. Not only are alternative energy and power sources making their advent, but greenhouse gas emission reduction has also become a major factor in the development of vehicles with combustion...

Rotating heat pipe assisted annealing

Steel is an indispensable material for the sustainable maintenance and progress of modern civilization. Its versatility in terms of mechanical and thermal characteristics, corrosion resistance, raw material availability, energy consumption and recyclability provides a clear advantage in a fast-changing technological landscape. In order to adapt...

Towards a heat transfer based distance sensor for measuring sub-micrometer separations

In this thesis a proof-of-principle demonstration is developed that uses the heat flux between a probe and a sample as a proxy for their separation. The proposed architecture uses a probe that consists of a bilayer cantilever with an attached sphere at its free end. The deflection of the cantilever that is caused by the heat input is measured...

Rayleigh-Bénard convection of a supercritical fluid: PIV and heat transfer study

Fluids above the critical point are widely used in industry. Chemical, pharmaceutical, food industry and energy production are some examples. In the energy production sector they are mainly used as cooling fluids, because they allow to increase the thermal efficiency of the power plants. However, the fundamentals of their heat transfer behavior...

Natural and Mixed Convection in Coarse-grained Porous Media

In the chain of steel production, the blast furnace converts iron ore into liquid iron. The hearth of the blast furnace, where the liquid metal is collected and tapped off, is filled with relatively large coke particles (D ~ 20 – 100 mm). The meandering flow of hot liquid metal in the coarse-grained porous medium in the hearth causes erosion of...