Steady and unsteady flow analysis in microdiffusers and micropumps: a critical review

Abstract

In recent research, there has been a growing interest in the analysis of flow through microdiffusers and micropumps in order to characterize and optimize the performance of these devices. In this review, the recent advances in the numerical and experimental analysis of the steady and pulsating flows through microdiffusers and valveless micropumps are surveyed. The differences between the performance of microdiffusers and micropumps in steady and unsteady flow regimes are described. Qualitative and quantitative discussions of the effects of different design parameters on the performance of microdiffusers and valveless micropumps in both steady and unsteady flow regimes along with the contradictory results reported in the literature in this regard are provided. In addition, a summary of the latest micropump technologies along with the advantages and disadvantages of each mechanism with the emphasis on the innovative and lessreviewed micropumps are presented. Two important types of fixed microvalves, as part of valveless micropumps are described in details. Experimental flow visualization of steady and pulsating flows through microdiffusers and micropumps as a useful tool for better understanding the underlying micro-fluid dynamics is discussed. The present review reveals that there are many possible areas of research in the field of steady and unsteady flows through microdiffusers and micropumps in order to understand the effects of all important design parameters on the performance of these devices. List of symbols uVelocity in x direction (m/s) v Velocity in y direction (m/s) u max Maximum velocity in x direction (m/s) Q Volumetric flow rate (m 3 /s) Q net Net flow rate (m 3 /s) q Density (kg/m 3 ) p Pressure (Pa) p 0 Static pressure (Pa) t Time (s) x Axial position (m) y Transverse position (m) T Excitation period (s) l Shear viscosity (kg/m s) m Kinematic viscosity (m 2 /s) Re = u max D h /m Reynolds number St = x D h /u max Strouhal number Ro = x D h 2 /m = Re.St Roshko number Wo = D h /d Womersley number V Volume-average velocity (m/s) P Maximum pressure (Pa) Dp Frictional pressure drop (Pa) g Diffuser efficiency g max Maximum diffuser efficiency n d Total pressure loss coefficient in the diffuser direction n n Total pressure loss coefficient in the nozzle direction

Understanding frequency response of thermal micropumps using electrical network analogy

“…4, is consistent with qualitative trends reported in the literature [6,9,26,[34][35][36][37][38][39][40]. In addition, Nabavi [9], Hwang [39], and Sheen [40] suggested an increase in the net flow rate of the micropump as the operating frequency increased, until a cut-off frequency is reached, L . A second cut-off frequency is observed with further increase in operating frequencies, H .…”

“…Special interest has been devoted to developing micropumps technologies for applications in drug delivery, thermal management, fuel injection, and chemical analysis [1,[3][4][5][6]. In developing micropumps several types have been introduced including piezoelectric, electrostatic, thermopneumatic, phasechange, shape memory alloy, electromagnetic, electrowetting, electro-osmotic, and evaporative types [2,[5][6][7][8][9]. Previously, fabrication, and characterization and performance of different types of micropumps were investigated [6].…”

Rapid real-time recirculating PCR using localized surface plasmon resonance (LSPR) and piezo-electric pumping

“…An unidirectional flow was achieved using in-channel piezoelectric pumping 31 that was implemented by, first, milling a 10mm diameter indentation to 200μm depth in the polycarbonate chip to serve as the pumping chamber. Then, the chamber was connected to the channel structures via Diffusion no-moving parts valves (NMPs) 31, 32 , which were also milled to 200 μm depth and utilized for flow rectification (Fig.…”

“…Then, the chamber was connected to the channel structures via Diffusion no-moving parts valves (NMPs) 31, 32 , which were also milled to 200 μm depth and utilized for flow rectification (Fig. S3).…”

Experimental Investigation of Pulsating Turbulent Flow Through Diffusers

“…There is a rapidly growing interest for the analysis of the flow in microdiffusers to optimize the performance of devices, and recent advances in the analysis of flow were surveyed by Nabavi [11]. Most of the studies on unsteady flows through microdiffusers have been carried out for planar microdiffusers [12,13].…”