Dynamic response of viscous compressible fluids in rigid tubes

Data on experimental verification of Iberall's analysis applies to such problems as pressure sensing, pneumatic control circuits with bellows, measuring irregular shaped volumes, and transmitting fluid power by pulsating flow

Effect of Pulsation Width Modulation (PWM) on the Performance of an Evaporator

Pulsating flow can increase the heat transfer coefficient when a two-phase flow passes through a single horizontal tube through the following mechanisms: 1) When liquid-vapor two-phase flow and heat transfer occurs inside a tube, flow pulsations can change the flow pattern and increase liquid-wall contact area at a fixed void fraction, thus increasing the heat transfer coefficient; 2) Local pressure at some locations in the tube will drop more with pulsating flow, and the attendant reduction saturation temperature can increase local evaporation and heat transfer. However, the effects of pulsation are more complex for pulsations within a practical evaporator for which the use of a multi-tube construction and the presence of tube bends at the end of each tube certainly affect the resulting flow. In this case, it is anticipated that pulsation width modulation is very important for evaporator performance enhancement. Moreover, local pressure drop in the evaporator increases due to the pulsating flow, and this needs to be taken into account for practical evaporators when considering pulsation as a method of heat transfer performance enhancement. In this work, the effects of pulsation width on heat transfer coefficient and pressure drop in an air-to-refrigerant evaporator have been studied experimentally. An experimental system has been developed with two separate but identical evaporators located in separate but identical wind tunnels. The pulsation width can be controlled with a minimum period of 1s. Average heat transfer coefficient, local heat transfer coefficient and pressure drop have been measured and compared with and without pulsating flow. Two-phase flow regimes at different locations in the evaporator are also observed with pulsating flow, and a new flow regime characterization is provided. These observations are used to help explain the heat transfer enhancement in pulsating flow

Discrete-vortex simulation of pulsating flow on a turbulent leading-edge separation bubble

Studies are made of the turbulent separation bubble in a two-dimensional semi-infinite blunt plate aligned to a uniform free stream with a pulsating component. The discrete-vortex method is applied to simulate this flow situation because this approach is effective for representing the unsteady motions of the turbulent shear layer and the effect of viscosity near the solid surface. The numerical simulation provides reasonable predictions when compared with the experimental results. A particular frequency with a minimum reattachment is related to the drag reduction. The most effective frequency is dependent on the amplified shedding frequency. The turbulent flow structure is scrutinized. This includes the time-mean and fluctuations of the velocity and the surface pressure, together with correlations between the fluctuating components. A comparison between the pulsating flow and the non-pulsating flow at the particular frequency of the minimum reattachment length of the separation bubble suggests that the large-scale vortical structure is associated with the shedding frequency and the flow instabilities

Дослідження тепловіддачі пульсуючого газового потоку

Проведено дослідження процесу теплообміну пульсуючого потоку вихлопних газів дизельного двигуна на різних режимах роботи. В результаті обробки експериментальних даних отримані залежності коефіцієнта тепловіддачі від характеристик пульсуючого потоку, які можуть бути використані при розрахунку теплообмінників для утилізації теплоти вихлопних газів.Research has been done into the heat exchange process of exhaust gas pulsating flow of diesel engine at various operation regimes. The resulting experimental date showed the dependence of heat exchange coefficients on pulsating flow characteristics, which can be used when projecting heat exchangers for utilizing heat of exhaust gases

Heat transfer in pulsating flow

M.S.Charles W. Gorto

Importance of Mechanical Losses Modeling in the Performance Prediction of Radial Turbochargers under Pulsating Flow Conditions

This work presents a study to characterize and quantify the mechanical losses in small automotive turbocharging systems. An experimental methodology to obtain the losses in the power transmission between the turbine and the compressor is presented. The experimental methodology is used during a measurement campaign of three different automotive turbochargers for petrol and diesel engines with displacements ranging from 1.2 l to 2.0 l and the results are presented. With this experimental data, a fast computational model is fitted and used to predict the behaviour of mechanical losses during stationary and pulsating flow conditions, showing good agreement with the experimental results. During pulsating flow conditions, the delay between compressor and turbine makes the mechanical efficiency to fluctuate. These fluctuations are shown to be critical in order to predict the turbocharger behaviour.Serrano Cruz, JR.; Olmeda González, PC.; Tiseira Izaguirre, AO.; García-Cuevas González, LM.; Lefebvre, A. (2013). Importance of Mechanical Losses Modeling in the Performance Prediction of Radial Turbochargers under Pulsating Flow Conditions. SAE International Journal of Engines. 6(2):1-10. doi:10.4271/2013-01-0577S1106

Vibration of a flexible pipe conveying viscous pulsating fluid flow

The non-linear equations of motion of a flexible pipe conveying unsteadily flowing fluid are derived from the continuity and momentum equations of unsteady flow. These partial di!erential equations are fully coupled through equilibrium of contact forces, the normal compatibility of velocity at the fluid} pipe interfaces, and the conservation of mass and momentum of the transient fluid. Poisson coupling between the pipe wall and fluid is also incorporated in the model. A combination of the finite difference method and the method of characteristics is employed to extract displacements, hydrodynamic pressure and flow velocities from the equations. A numerical example of a pipeline conveying fluid with a pulsating flow is given and discussed

Design and performance analysis of concentrated photovoltaic cooling.

Kahagala Gamage, Upul - Associate SupervisorThe use of solar energy as a global energy source has increased over the past two decades. Photovoltaic cells, which utilise the sun to generate electricity, are a promising alternative to fossil fuels that contribute to climate change. However, the high intensity of concentrated solar radiation can cause overheating in photovoltaic cells, reducing their efficiency and power output. Researchers worldwide are improving cooling in concentrated photovoltaic cells (CPV) to enhance temperature uniformity and improve power output. Previous studies have demonstrated that pulsating flow can effectively enhance heat transfer in various fields, including electronics, mechanical engineering, and medicine. In this research, three flow patterns (continuous flow, uniform pulsating flow, and bio-inspired pulsating flow) were studied in both simulation and experimental designs. Two cooling designs were considered: the conventional design (C- Design) and the parallel design with baffles (W-B) and without baffles (Wout-B). With the implementation of 30 pulses per minute bio-inspired pulsating flow a reduction of 1.96% in solar cell temperature was observed when compared to continuous flow. This reduction in temperature was consistently observed across a range of flow rates from 0.5 to 2.5 L/m, employing the parallel Wout-B design. Notably, the bio-inspired pulsating flow shows better performance in comparison to uniform pulsating flow, as well as the conventional designs with continuous flow and uniform pulsating flow, resulting in notable improvements in cooling efficiency of 1.22%, 2.14%, and 4.00%, respectively. In terms of a direct comparison, the implementation of uniform pulsating flow in the parallel Wout-B design exhibited a maximum cooling improvement of 0.74% when contrasted with continuous flow. Furthermore, when assessing uniform pulsating flow against the C-design with uniform pulsating flow in the parallel Wout-B design, a noteworthy enhancement of 0.93% was observed. Remarkably, the C-design with uniform pulsating flow demonstrated a superior effectiveness of 1.90% when compared to the C-design with continuous flow.MSc by Research in Energy and Powe