Thermal analysis of near-isothermal compressed gas energy storage system

Experimental and analytical evaluation of a hydro-pneumatic compressed-air Ground-Level Integrated Diverse Energy Storage (GLIDES) system

\n In this work, the unsteady Reynolds-averaged Navier–Stokes (URANS) and three hybrid Reynolds-averaged Navier–Stokes-large eddy simulation (RANS-LES) models are employed to resolve the vortical flows in a typical single-stage side channel pump, to evaluate the suitability of these advanced turbulence models in predicting the pump hydraulic performance and unstable swirling flows. By the comparison of the overall performance, it can be observed that the results obtained by scale-adapted simulation (SAS) are closer to test data than shear stress transport (SST), detached eddy simulation (DES) and filter-based model (FBM). Simultaneously, the distribution of axial velocity on the plane near the interface is used to describe the position and intensity of internal fluid exchange between impeller and side channel. It is obvious that the intensity of mass flow exchange is strong near the inner and outer edges. Then, the vortex core region illustrates that the vortex is easily produced near the interface due to internal fluid exchange. Finally, the evolutions of circumferential in-plane vortical structures are presented to further account for the process of fluid exchange and the main vortex flows. It reveals that the recirculation flow presents a strong instability during 6–7 blade pitches as the fluid enters into the impeller and the flow is stable in downstream 7–8 blade pitches. Besides, the flow turns to be unsteady near outlet affected by the sudden change of fluid direction. This work could provide some suggestions for the choice of appropriate turbulence model in simulating strong swirling flows.

Effect of URANS and Hybrid RANS-Large Eddy Simulation Turbulence Models on Unsteady Turbulent Flows Inside a Side Channel Pump

In this paper, the effectiveness of storing energy by compressing and expanding a condensable gas is evaluated A high efficiency energy storage system, which stores energy by compressing/expanding gas (air) using a liquid (water) piston has been recently introduced and extensively studied With the use of the liquid piston, the inefficient gas turbomachines used in conventional gas compression/expansion systems are replaced with high efficiency hydraulic machines Utilizing heat transfer techniques and replacing the non-condensable air with a condensable gas (ie CO2, synthetic refrigerants, hydrocarbon refrigerants, etc) have been proposed as methods to improve energy density and roundtrip efficiency of such systems, leading to near isothermal and near isobaric charge/discharge processes In order to investigate the effectiveness of the proposed concept, a miniature lab-scale experimental setup was designed and built to investigate the compression/expansion characteristics and energy storage efficiency of a system utilizing R134a as the energy storage (primary) working fluid, and mineral refrigerant oil as the liquid piston (secondary) working fluid Several tests are carried out to quantify energy storage efficiency and energy density It is found that improving heat transfer rates from/into the storage fluid results in increased efficiency and energy density A heat-transfer enhancement strategy to achieve near isothermal, isobaric expansion and compression is proposed and investigated experimentally Some results are generalized and presented in non-dimensional form which can be applied to describe and/or design scaled-up systems Lastly, a potential working fluid for a scaled-up system is discussed

Near-isothermal-isobaric compressed gas energy storage

To fill the lack of literature in the numerical study of Positive Displacement (PD) pumps in cavitating condition, a comprehensive and transient Computational Fluid Dynamics (CFD) model of a PD pump, simulating the cavitation arising during the suction stroke, was created. The “full” cavitation model was utilised to study its capability on PD pumps cavitation. A set of three plunger speeds were simulated. Using the highest plunger speed an assessment was made of the effect of 1.5, 3, 4.5 and 15 ppm of air mass fraction on pump performance and cavitation. An experimental test rig, replicating the CFD model, was designed and built in order to validate the numerical model and find its weaknesses. CFD modelled, in a consistent way, the fluid dynamics phenomena related to cavitation (chamber pressure approaching the vapour pressure, the vaporization/condensation and the pressure spike occurrence at the end of the suction stroke marking the end of cavitation). On the other hand the CFD pressure trends calculated appeared stretched along the time axis with respect to the experimental data and this highlighted issues in the multiphase and cavitation models: the vaporization/condensation rate calculated by CFD did not follow the real dynamics correctly because the non-condensable gas expansion was overestimated. This was seen when comparing the CFD/experiments where the simulated pressure drop gradient, at the beginning of the suction stroke and the pressure peaks as the valve closed, exhibited a delay in their occurrence. The simulation results were sensitive to the dissolved air mass fraction as the delay depended on the amount of air dissolved in the water. Although the influence of the air mass fraction was considered consistent, the 3 ppm CFD case was the closest to the experiment results whereas the analyst expected the 15 ppm case to be more accurate.

https://www.tandfonline.com/doi/pdf/10.1080/19942060.2015.1110535

A CFD and experimental study on cavitation in positive displacement pump : benefits and drawbacks of the "full" cavitation model

Product Manager for Union Pump Company, in Battle Creek, Michigan. He has 39 years of experience in the design, application, and maintenance of reciprocating power and direct acting pumps. Prior to Mr. Tackett’s current position in Aftermarket Product Development, he served as R&D Engineer, Field Service Engineer, and new equipment order Engineer, in addition to several positions in Reciprocating Pump Sales and Marketing. He has been a member of ASME since 1991.

Positive Displacement Reciprocating Pump Fundamentals - Power And Direct Acting Types

A sealing system for a pump having a plunger includes a housing having an internal chamber adapted to receive a portion of the plunger. Primary and secondary seals are located within the internal chamber and adapted to sealingly engage the plunger. The primary seal communicates with the fluid being pumped. A barrier fluid chamber contains a barrier fluid in contact with the primary seal and the secondary seal. A pressure referencing device has an inlet port in communication with the pumped fluid and an outlet port providing fluid at a pressure magnitude equal to a peak pressure of the pumped fluid. A pressurizing device is in communication with the fluid at the peak pressure and the barrier fluid to maintain the barrier fluid pressure at a magnitude greater than the peak pressure of the pumped fluid such that the pumped fluid is restricted from leaking past the primary seal.

Herbert H. Tackett

Papers

Positive Displacement Reciprocating Pump Fundamentals - Power And Direct Acting Types

Zero emissions reciprocating pump