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1

On numerical modelling of heat transfer and fluid flow in a scraped surface heat exchanger

Błasiak P., Gnutek Z.

Archives of Thermodynamics

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2014

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Vol. 35, no. 3

251--264

EN

Steady state two-dimensional numerical simulation of laminar heat transfer and fluid flow in a scraped surface heat exchanger (SSHE) is presented. Typical SSHE consists of a stator, rotating shaft and scraping blades. Due to symmetry only a quarter of the heat exchanger is modelled. Governing equations for transport of mass, momentum and energy are discretised and solved with the use of commercial CFD code. The results are presented in a nondimensional form for velocity, pressure and temperature distributions. Local and averaged Nusselt number along the stator wall are calculated and depicted in graphs. It was found that the thirty fold increase of the cReynolds number, leads to heat transfer enhancement rate by three times.

2

The analysis of flow around a cylinder under free convection conditions

Błaszczuk A., Nowak W.

Turbulence : international journal

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2007

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Vol. 12

31-41

EN

The article describes the application of the optical gradient technique to the analysis of development of the thermal boundary layer. This analysis was carried out using a modified schlieren system. The modifications made to the optical measuring system made it possible to extend the measuring range of the testing beam with a simultaneous reduction of the measuring system's susceptibility to misalignment. The coherent light source was an He-Ne laser of a power of 25 mW. Recording of the distribution of the information carrier's optical density around the experimental model was conducted using a CCD matrix coupled with an image acquisition card. The experimental model was a horizontal copper cylinder. The measurements of convective heat transfer were carried out for different thermal conditions (470, 410 and 350 K) of the cylinder surface. The obtained results of experimental analysis have been approximated with the exponential relationship NUD = C(Ra).

3

Experimental investigation of the convective heat transfer around a perpendicular plate by means of flow visualization techniques

Błaszczuk A., Mirek P.

Archives of Thermodynamics

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2004

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Vol. 25, no. 3

73-86

EN

The subject of the study is presentation of optical techniques for the measurement of local values of overall heat transfer coefficient. Measuring systems based on Schlieren and interference systems, built either in classical versions or modified by the authors of the present study, were used in the research. The recording of the distribution of optical density of the information carrier around the object under analysis was carried out using a CCD matrix with the image acquisition card. The role of the information carrier in the experimental research was performed, alternatively, by the collimated beam of a 25 mW-power He-Ne laser or a slotted white light source in the form of a halogen lamp, type H3. The modifications introduced to the optical measuring range along with a reduction in the susceptibility of the systems to misalignment.

4

Transient laminar-turbulent transition of thermal boundary layer after the change of incidence angle

Wierciński Z., Kaiser M.

Transactions of the Institute of Fluid-Flow Machinery

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2003

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nr 114

237-252

EN

Convective heat transfer problems occur in many technical application. Unsteady transition in the heated boundary layer is one of them. Heat transfer investigation of a flat plate in a low subsonic wind tunnel for flow velocity Uo=15 and 20 m/s was performed. The changes in time of the Stanton number distribution along the plate were observed after the incidence angle had been changed from - 0.8 to 0°. While for the incidence angle i= -0.8° the flow in boundary layer was laminar, for angle -0.67#176 the transition was observed, and for the angle -0.23° the flow was turbulent. After the sudden change of angle the transient bahaviour of the heat transfer between these three states were observed, e.g. for the change from -0.8 to -0.6° from laminar to transitional, so after the time of about 30 min the transition was perfect. This time is needed to achieve a new internal thermal balance of the plate and transition in thermal boundary is established.