heat transfer

Even though numerous PRAs have shown that fire can be a major contributor to nuclear power plant risk, there are some specific areas of knowledge related to this issue, such as the prediction of fire-induced damage to electrical cables and circuits, and their potential effects in the safety of the nuclear power plant, that still constitute a practical enigma, particularly for the lack of approaches/models to perform consistent and objective assessments. This report contains a discussion of three different models ...

Thermo fluid energy system simulation has shown to be a useful tool for engineers; encompassing component design, system design and with increasing interest, system optimization. Thermo fluid energy systems, be they for comfort cooling, comfort heating, power generation, or any other purpose typically possess a unique composition and function. This has resulted in simulations for individual rather narrowly defined energy systems, each customized for the particular system of interest. However, it is impossible to ignore that the majority of thermo ...

Pool boiling heat transfer measurements from different heater sizes and shapes were obtained in low-g (0.01 g) and high-g (1.7 g) aboard the NASA operated KC-135 aircraft. Boiling on 4 square heater arrays of different size (0.65 mm2, 2.62 mm2, 7.29 mm2, 49 mm2) was investigated. The heater arrays consist of 96 independent square heaters that were maintained at an isothermal boundary condition using control circuitry. A fractional factorial experimental method was designed to investigate the effects of bulk liquid ...

Phase change technology is a science that is continually finding new applications, from passive refrigeration cycles to semiconductor cooling. The primary heat transfer techniques associated with phase change heat transfer are pool boiling, flow boiling, and spray cooling. Of these techniques, spray cooling is the least studied and the most recent to receive attention in the scientific community. Spray cooling is capable of removing large amounts of heat between the cooled surface and the liquid, with reported heat flux capabilities ...

An extensive review of the literature indicates a lack of systematic study of supercritical CO2 gas cooling and no prior work on CO2/oil mixture in supercritical region, suggesting a lack of fundamental understanding of supercritical gas cooling process and a lack of comprehensive data that would help quantify the performance potential of CO2 microchannel heat exchangers for engineering applications. This dissertation presents a systematic and comprehensive study on gas cooling heat transfer characteristics of supercritical CO2 in microchannels. Semi-empirical correlation ...

Spray cooling is a powerful heat transfer technique in which an atomizing nozzle provides a flow of liquid droplets directed towards a hot surface. This dissertation explores two potentially powerful techniques capable of improving traditional spray cooling: nanofluids and extended surfaces. Nanofluids were experimentally studied in a pool boiling system to elucidate the underlying mechanisms of critical heat flux (CHF) enhancement. Dilute suspensions of nanoparticles were found to have a degrading or no effect on boiling performance. Greater concentrations (≥ ...

This thesis is carried out at Volvo Aero in Trollhättan at the Department of combustion chambers and nozzles. The aim is to compare two methods for coupled analysis between structural and fluid calculations and assess if the methods can be applied on a whole nozzle. The softwares used are ANSYS CFX and ANSYS mechanical. The two methods evaluated are unidirectional and bidirectional Fluid Structure Interaction (FSI). The calculations are made on a section of half a coolant channel and the ...

In the harsh environment inside a jet engine, the turbine exhaust is one of the most critical areas in terms of high temperatures. The structure material must be able to handle the exposure of very high static temperatures as well as fast heating and cooling, creating temperature gradients. The scope of this work is to further investigate the crucial so called pocket area and the influence of leakage flows on the heat transfer on the turbine structure. The tool for ...