Experimental and Numerical Investigation of an In-line TubeBank’s Cooling Potential

Abstract: Within this thesis, an experimental and numerical study was performed on cooling of a 5x5 in-line tube bank placed within a duct using impinging jets. The Reynolds numbers investigated using the main inlet as reference were Re~2300 and Re~4500. The Reynolds number corresponding to the impinging jets was Re~147000. The aim of the study was to replicate the thermal conditions in an industrial tunnel kiln used for production of cylindrical objects. As the current cooling was fairly unknown due to difficulties in conducting proper measurements a miniature tunnel oven model had been built. The experimental part of the thesis was done on said miniature tunnel oven model which was at the time located at Gävle University (HiG).Prior to collecting the cooling data, an extensive groundwork was performed e.g. leakage test, jet and inlet velocity studies. The velocity measurements were conducted using a hot-wire anemometer. The simulation part was conducted using computational fluid dynamics simulations (CFD). A pre-study was performed in order to study the effect of using different settings in the CFD-setup. The study resulted in the use of steady RANS together with k – ω SST as turbulence model. First order schemes were used except for the energy equation which used second order. A mesh independence study was performed and showed a better agreement to experiments with the increase in mesh density. The experimental and numerical results showed good resemblance to each other for both the temperature and the heat transfer coefficient of the cylinders. The average deviation of the simulations to the experiments were 8.3% and 11.0% for the cylinder temperature and heat transfer coefficient respectively. By studying the obtained temperature and heat transfer coefficient contours obtained through ANSYS a more evenly distributed cooling was obtained by placing the impinging jets between cylinders compared to directly facing cylinders in a cylinder package. This was also apparent by observing the obtained results from the experimental study.