Deposition of fine aerosols in laminar tube flow at high temperature with large gas-to-wall temperature gradients

Fluid flow and heat transfer in the entrance region of rectangular microchannels of various aspect ratios are numerically investigated in the slip-flow regime with particular attention to thermal creep effects. Uniform inlet velocity and temperature profiles are prescribed in microchannels with constant wall temperature. An adiabatic section is also employed at the inlet of the channel in order to prevent unrealistically large axial temperature gradients due to the prescribed uniform inlet temperature as well as upstream diffusion associated with low Reynolds number flows. A control-volume technique is used to solve the Navier–Stokes and energy equations which are accompanied with appropriate velocity slip and temperature jump boundary conditions at the walls. Despite the constant wall temperature, axial and peripheral temperature gradients form in the gas layer adjacent to the wall due to temperature jump. The simultaneous effects of velocity slip, temperature jump and thermal creep on the flow and thermal patterns along with the key flow parameters are examined in detail for a wide range of cross-sectional aspect ratios, and Knudsen and Reynolds numbers. Present results indicate that thermal creep effects influence the flow field and the temperature distribution significantly in the early section of the channel.

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Material Deterioration in High Temperature Gradients and Transients

Modeling and Simulation Based Life-Cycle Engineering ◽

10.1201/9781482264715-24 ◽

2004 ◽

pp. 225-239

Keyword(s):

High Temperature ◽

Temperature Gradients

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An experimental investigation of pressure drop of aqueous foam in laminar tube flow

10.2172/6534897 ◽

1987 ◽

Cited By ~ 1

Author(s):

B.F. Blackwell ◽

K.B. Sobolik

Keyword(s):

Experimental Investigation ◽

Pressure Drop ◽

Tube Flow ◽

Aqueous Foam ◽

Laminar Tube Flow

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LC/8YSZ TBCs Thermal Cycling Life and Failure Mechanism under Extreme Temperature Gradients

Coatings ◽

10.3390/coatings11091051 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1051

Author(s):

Kun Liu ◽

Xi Chen ◽

Kangping Du ◽

Yu Wang ◽

Jinguang Du ◽

...

Keyword(s):

High Temperature ◽

Surface Temperature ◽

Thermal Cycling ◽

Thermal Shock ◽

Failure Mechanism ◽

Extreme Temperature ◽

Temperature Gradients ◽

Accelerated Life Test ◽

Ceramic Layer ◽

Cycling Life

The purpose of this paper is to study the thermal shock resistance and failure mechanism of La2Ce2O7/8YSZ double-ceramic-layer thermal barrier coatings (LC/8YSZ DCL TBCs) under extreme temperature gradients. At high surface temperatures, thermal shock and infrared temperature measuring modules were used to determine the thermal cycling life and insulation temperature of LC/8YSZ DCL TBCs under extreme temperature gradients by an oxygen–acetylene gas flame testing machine. A viscoelastic model was used to obtain the stress and strain law of solid phase sintering of a coating system using the finite element method. Results and Conclusion: (1) Thermal cycling life was affected by the surface temperature of LC/8YSZ DCL TBCs and decreased sharply with the increase of surface temperature. (2) The LC ceramic surface of the failure coating was sintered, and the higher the temperature, the faster the sintering process. (3) Accelerated life test results showed that high temperature thermal cycling life is not only related to thermal fatigue of ceramic layer, but is also related to the sintering degree of the coating. (4) Although the high temperature thermal stress had great influence on the coating, great sintering stress was produced with sintering of the LC ceramic layer, which is the main cause of LC/8YSZ DCL TBC failure. The above results indicate that for new TBC ceramic materials, especially those for engines above class F, their sinterability should be fully considered. Sintering affects the thermal shock properties at high temperature. Our research results can provide reference for material selection and high temperature performance research.

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