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Numerical investigation of local heat transfer distribution on surfaces with a non-uniform temperature under an array of impinging jets with various nozzle shapes

Marzec K., Kucaba-Piętal A.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 4

1313--1324

EN

Numerical calculations of heat transfer characteristics of an impingement cooling system with a non-uniform temperature on a cooled surface using ANSYS CFX have been performed. The influence of a surface heat flux qw(x) and a nozzle shape on the Nusselt number distribution on the cooled surface has been studied. The setup consisted of a cylindrical plenum with an inline array of ten impingement jets. Cylindrical, convergent divergent shapes of nozzles and linear temperature distribution on the cooled surface have been considered for various heat fluxes qw (x). Results indicate that geometry of the cylindrical nozzles resulted in the highest Nusselt numbers along the cooled surface. The line of the averaged Nusselt number has a trend to increase in the direction of the flow for the cooling system with increasing values of the surface heat flux q(x). This tendency can be observed for all presented shapes of jets. On the other hand, for decreasing functions of the heat flux qw (x), the Nusselt number distribution is more uniform. It can be observed for all types of nozzles. Very similar values of the Nusselt number occur especially for the non-uniform heat flux 5000-2500W/m². For constant values of the heat flux q(x) = 5000W/m², the line of the average Nusselt number has a trend to increase slightly in the direction of the flow. Numerical analysis of different mesh density results in good convergence of the GCI index, what excludes mesh size dependency. The presented study is an extension of the paper (Marzec and Kucaba-Piętal, 2016) and aims at answering the question how the Nusselt number distribution on the cooled surface is affected by various geometries of nozzles for a non-uniform surface heat flux qw (x).

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Ocena wpływu kształtu dyszy ssącej na wydajność i opory przepływu w podciśnieniowym transporcie pneumatycznym

Jóśko E., Skotnicki P.

Prace Instytutu Ceramiki i Materiałów Budowlanych

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2011

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R. 4, nr 7

108-117

PL

W pracy przedstawiono wyniki badań nad określeniem wpływu kształtu dyszy ssącej na wydajność i opory przepływu dwufazowego gazu i ciała stałego w typowej instalacji podciśnieniowego transportu pneumatycznego. Do analiz wykorzystano płaskie dysze ssące o kącie rozwarcia Alfa = 40o i 60o. W przypadku płaskich dysz stożkowych, dzięki rozwinięciu powierzchni kontaktu dyszy z lustrem materiału, więcej powietrza jest pobierane przez dyszę, przez co maleje ryzyko blokady rurociągu. Takie rozwiązanie pozwala na zastosowanie tego typu dysz do transportu materiałów drobnoziarnistych, które ze względu na ograniczone możliwości dysz rurowych nie mogły być transportowane podciśnieniowo.

EN

The aim of the research was to determine influence of the suction nozzle shape at nature of two phase gas-solid flow and pressure drop in typical vacuum pneumatic conveying systems. In the research there were used flat suction nozzles with flare angle Alfa = 40o, 60o. Flat conical nozzles, due to expanded contact surface with material level, suck more air what decreases risk of pipeline clogging. This solution enables use of the above nozzles for transport of fine-grained materials, which because of limited possibilities of pipe nozzles could not be vacuum transported.

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Sweep, lean, taper and twist of nozzle blading in 2D model. Inverse problem.

Puzyrewski R., Tesch K.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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1999

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nr 115

327--336

EN

The paper objectives is to show how different factors named here as sweep, lean, taper and twist appears in the solution of the inverse problem within the frame of 2D model. The skeletons of the channels or profiles are the results of the solution of the in verse problem. They can be converted into the shapes of blading.