Pumping Concept

Two terms related to the pumping need to be distinguished, the conductance (C) and the pumping speed (S). They are typically expressed in the identical units of volumetric flow per second (I s ). The conductance applies to passive parts of a vacuum system (tubes, elbows, valves, etc.), while the pumping speed intrinsically refers to some active devices that actually remove gas molecules from the system. 

The vacuum chamber characterized by the base pressure Phase P l 

In the case in which molecular flow conditions are satisfied, one can easily calculate the conductance. For example, for a straight cylindrical tube of length L and diameter D 

In analogy to electrical circuits, for combining conductances, one can apply Kirchhoff s laws to calculate the total conductance, Cj, of an assembly of elements. If two parts are connected in parallel, the total conductance wiU be Cp = Q -F Cz, and if they are connected in series, it will be -F Thus, the simple consequence for the serial connection is that the smallest conductance wiU determine the conductance of the assembly. 

Considering now the active pumping elements, that is, the pumps, it is obvious that the effective pumping speed will be reduced by the total conductance of the connection between the vacuum chamber and the pump opening. The nominal pumping speed of the isolated pump, Snom. usually declared by the pump producers, will therefore never be achieved in practice. The true (effective) pumping speed, S, is rather given by  

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As a byproduct of work on cough CPR (Section 18.3.1.3 and Section 18.3.1.10), Rosborough found that using ventilation to increase intrathoracic pressure with simultaneous compression of the abdominal compartment maintained carotid artery flows similar to flows from standard CPR in dog experiments [36]. This model, based on a pure thoracic pump concept, has not been demonstrated to improve outcome in humans, and has been associated with pulmonary complications attributed to high airway pressures. 

C E Brennen, Hydrodynamics of Pumps, Concepts ETI, Norwich VT, 1994. Also Oxford University Press, Oxford, 1994. 

The computational results demonstrated that the liquid-liquid electroosmotic pumping concept is feasible for relatively low interface zeta potentials and viscosity ratios. The time evolution of the velocity profile provides a detail insight of the flow characteristic. It is recommended that detailed experiment be carried to validate the model. 

Thermocapillary pumping (TCP) is a pumping concept based on thermocapillary forces, where a liquid droplet moves through a microchannel or on a planar surface. A temperature gradient leads to a difference of the surface stresses across a liquid droplet and propels it into a cooler region. 

Glockner and Naterer reported a new method of cyclic flow control with an external heat source is developed for thermocapillary pumping of a microdroplet in a closed microcharmel [12]. The pumping concept involves a stationary cyclic heat source embedded within an adjoining... 

Another popular heat pump concept, if not widely adopted, is the direct use of the overhead vapor as the heat pump working fluid, an open cycle heat pump termed mechanical vapor recompression (MVR). In MVR the compressor raises the pressure of the overhead vapor to the point where it will condense at a temperature sufficient to drive the reboiler. This has the advantage that the reboiler heat exchanger serves as both the reboiler and the condenser. One disadvantage is the process vapor may not be the most efficient working fluid for the temperatures involved. Nevertheless, primary energy savings over 50% are anticipated [21]. 

A second interesting result is that wearable infusion pumps for insulin delivery have been marketed for nearly a decade, and less than 1% of insulin- dependent diabetics now use the pump. Those that do, however, are able to demonstrate superior control of blood glucose. This fact is reflected in the relatively high score that the infusion pump concept received. However, the 99% who do not use pumps have determined that the improved glycemic control is just not worth the hassle of wearing the pump 24 hours a day, changing tube sets, and having a needle in their skin all the time. 

With a strong emphasis on the development of electrochemical membrane processes, e.g., water electrolysis and fuel cells, electrode performance must be well characterized electrochemically. Use of a hydrogen pump concept can provide insight into anode and/or cathode electrode electrochemical characteristics. Furthermore, the method can also be utilized to determine the back diffusion of hydrogen through the membrane [5, 25]. 

Huth A, Schaar B, Oekermann T (2009) A proton pump concept for the investigation of proton transport and anode kinetics in proton exchange membrane fuel cells. Electrochim Acta 54 2774-2780... 

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