Fluid Film Characteristics over Horizontal Multi-Faceted Tube and the Augmentation of Thermal Performance

This work is concerned with the effect on the film pressure distribution caused on a hydrodynamic tilting pad bearing, by the change in surface properties of the journal. Here two identical journals, both manufactured with AISI 9840, were employed. One of them was coated with DLC by the triboadhesion process, and the second, was used as a reference without applying any coating. During tests, the tilting pad experienced a lower film pressure distribution when the journal coated with DLC was employed. This phenomena could readily be attributed to the different surface energies of the coated and uncoated journals, which in time causes that the fluid film characteristics to be modified by the reduction of the shear stresses at the wall, thus reducing the maximum film pressure measured and shifting the maximum pressure to the line of symmetry, drawn from the center of the journal to the pin of rotation of the tilting pad.

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Squeeze Film Characteristics Between Parallel Circular Plates Containing a Single Central Air Bubble in the Inertial Flow Regime

Journal of Tribology ◽

10.1115/1.2831283 ◽

1995 ◽

Vol 117 (3) ◽

pp. 513-518 ◽

Cited By ~ 9

Author(s):

H. Hashimoto

Keyword(s):

Differential Equation ◽

Nonlinear Differential Equation ◽

Bubble Radius ◽

Isothermal Condition ◽

Fluid Film ◽

Squeeze Film ◽

Cylindrical Shape ◽

Parallel Plates ◽

Air Bubble ◽

Film Characteristics

In this paper, the effects of an air bubble on the Newtonian squeeze film characteristics between two circular parallel plates with sinusoidal relative motion are theoretically investigated by considering the fluid film inertia effects. In the derivation of the lubrication equation, a single central air bubble of a cylindrical shape is considered. Approximating the momentum equation governing the squeeze film flow by the mean value averaged across the film thickness and assuming an ideal gas under isothermal condition for an air bubble, a nonlinear differential equation for the bubble radius is obtained. The nonlinear differential equation is solved by the Runge-Kutta-Gill method, and then the squeeze film force is determined. Moreover, the analytical solutions for the air bubble radius and pressure distribution are derived based on the perturbation method for a small amplitude of sinusoidal motion, and the analytical results are compared with the numerical results. From the calculated results, the combined effects of air bubble and fluid film inertia on the squeeze film force are clarified.

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Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020200192 ◽

2020 ◽

Vol 92 (3) ◽

pp. 30901

Author(s):

Suvanjan Bhattacharyya ◽

Debraj Sarkar ◽

Ulavathi Shettar Mahabaleshwar ◽

Manoj K. Soni ◽

M. Mohanraj

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Thermal Performance ◽

Working Fluid ◽

The Novel ◽

Heat Exchanger Tube ◽

Heat Transfer Augmentation ◽

Corrugated Tube ◽

The Impact ◽

Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

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