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Publisher Summary This chapter discusses the analytical characteristics of packed capillary columns. The geometrical characteristics of a chromatographic column primarily determine its performance. While an increased inlet pressure is the "technological price" that is paid for an increase in the number of theoretical plates obtained in LC, chromatographic columns having a variety of characteristics can meet the analytical task of component resolution with a variable degree of difficulty. The development of miniaturized LC systems has generated a great deal of interest during recent years. Some micro-column types having decreased column inner diameters and increased column lengths, were shown to exhibit considerably higher chromatographic efficiency than their conventional counterparts. The flow-rates typical of such columns are quite low, which results in significantly reduced consumption of both sample and mobile phase.

The aim of this paper is the study of the influence of the inlet pressure on the behaviour of the structure of the flowfield in a DF chemical laser. The unsteady complete Navier-Stokes equations have been solved numerically in the nozzles and in the laser cavity. The results show the different structures of the flow, the effect on the shape of the diffusion zone in the laser cavity and the distribution of the small-signal gain coefficients for a rotational-vibrational transition.

The pneumatically actuated total artificial heart (TAH) can maintain normal physiology in man and in experimental animals for several months with extracorporeal pneumatic actuation through the skin. The ultimate goal is the development of a totally implantable cardiac prosthesis that functions for a minimum of two years. The Cleveland Clinic Foundation’s cardiac prosthesis is a pusher-plate type of blood pump that uses protein-coated blood contact surfaces and trileaflet dura mater valves. The pusher-plate design for mechanical actuation provides a net stroke volume of 80 ml. It can pump as much as 9.6 L/min at 120 beats/min with 15 mm Hg inlet pressure. Total artificial hearts and the left ventricular assist devices (LVAD) were implanted in calves without anticoagulation for as long as seven months. Our group is developing a mechanically actuated universal blood pump for use as a TAH and LVAD, compatible with either thermal or electrical actuation systems. We have also developed a parathoracic version of the LVAD. The application of newly developed implantable actuation systems to cardiac prostheses offers many alternatives to the traditional pneumatic method. These methods should allow the patient to live a nearly normal life. We summarize the recent work in this area and identify the relevant design features and mechanical actuation systems for cardiac prostheses.

A number of entirely oil‐free, four‐stage reciprocating‐piston vacuum pumps which produce an ultimate pressure of approximately 15 mTorr have been in operation for periods approaching two years. These pumps have been used for pre‐evacuation of high and ultra‐high vacuum chambers and devices, backing of turbomolecular pumps, molecular drag pumps and Roots‐type blowers, regeneration of cryo‐pumps, pumping of vacuum furnances and process chambers for degassing solids and liquids. Basic performance characteristics are generally similar to conventional mechanical vacuum pumps with a comparable ultimate pressure but with the advantage of being free of hydrocarbons in the residual gas content. Practical operational experience regarding longevity, maintenance requirements, inlet pressure, and power relationships are presented.

Because of increased activities in cryogenic engineering, liquefaction cycles, in particular hydrogen cycles, are undergoing a more thorough thermodynamic analysis than had been justified previously.

Because of wide variations in the venturi throat pressure, well beyond the panellit gage trip range, that occur during the sequence of operational charge-discharge, the panellit gage cannot be included in the scram safety circuit during the period of time that charge- discharge operations are being performed. In its stead, the function of the panellit gage is replaced in an overlapping manner by a tube inlet pressure monitor that is equipped with high and low pressure trip mechanisms that may be included in the scram safety circuit during the time that the panellit gage must be by-passed. The tube inlet pressure monitor is then used to provide the protection from unstable flow that is normally obtained with the panellit gage. This memorandum describes the manner in which the tube inlet pressure monitor trip points are to be determined and used.

The response of a lift engine model compressor to inlet pressure distortion is studied in detail to determine the nature and extent of the critical area of spoiling. This is found to be a sector of width between 60 and 90 deg. On this basis a simple distortion index is proposed which implies that only the circumferential pressure gradients of a complex distortion pattern are significant. The “Parallel Compressor” model satisfactorily explains surge and this experience is related to different types of compressors and to complex spoiling patterns. Comments are made on the differences in behavior between compressors operating on rig test and in engines.Copyright © 1969 by ASME

F-111A airplane in-flight inlet pressure fluctuations for engine compressor surge, discussing average turbulence factor

Lift engine V/STOL configurations low speed characteristics, measuring exhaust reingestion, inlet pressure, engine and airframe effects in wind tunnels

This paper presents numerical investigations of a twin-screw expander for low grade (≤100 °C) heat to power conversion applications based on the bottoming Trilateral Flash Cycle. After a thorough description of the modeling procedure, a first set of simulations shows the effect of different inlet qualities of the R245fa working fluid and of the revolution speed on the expander performance. In particular, at 3750 RPM and an inlet absolute pressure of 5 bar, the volumetric and adiabatic efficiencies would increase from 24.8% and 37.6% to 61.2% and 83.1% if the inlet quality in the intake duct of the expander increased from 0 to 0.1. To further assess the effects of inlet quality, inlet pressure and revolution speed on the expander performance, parametric analyses are carried out in the ranges 0–1 inlet quality, 5–10 bar pressure and 1500–6000 RPM speed respectively.

Some anaesthetic gas machines have pipeline inlet pressure gauges which indicate the higher of either pipeline pressure, or machine circuit pressure (the pressure distal to the pressure reducing valve, and proximal to the flowmeter control valve). Failure by the operator to appreciate this feature may in specific circumstances lead to a delayed appreciation of pipeline malfunction or disconnection. The Canadian Standards Association Z168.3-M1980 Anaesthetic Gas Machine Standard requires pipeline inlet gauges which measure only pipeline (hose) pressure. Existing machines should be modified to accommodate this requirement.

UNTIL now pressure variation has been treated with great care in gas chromatography. Most experiments are carried out in equilibrium conditions, with more or less carefully controlled inlet pressure, and recently interest has been focused on the use of pressure programming1,2. In spite of the development of an exponential pressure programmer3 only slow rates of pressure programming have been used. For theoretical as well as practical reasons, we suggest the use of extremely high programme rates, so that when the injection is made, the inlet pressure is increased almost instantaneously from a value near that of the outlet pressure up to the final value. Clearly, the duration of the programme will be much less than that of the analysis itself. This method has, however, distinct advantages over the more conventional ones.

ALTHOUGH a great deal of attention1–5 has been focused on obtaining separations in the least possible time, the theory of minimum-time operation has not been developed for inlet/outlet pressure ratios greatly exceeding unity. Such a theory does not immediately seem widely applicable since most rapid separations made with an outlet pressure of one atmosphere do not require an inlet pressure greatly exceeding one atmosphere. This conclusion is incorrect, however, since a search for the optimum values of all parameters reveals that the optimum outlet pressure is very close to zero in all circumstances. Furthermore, the difference in minimum retention times found with an outlet pressure of one atmosphere and zero is large enough in many cases to be significant in obtaining more rapid analyses.

The relation between noise level, force (thrust), and inlet pressure has been investigated for 20 different blow‐gun nozzles or ejectors. This variety of design was a result of an Occupational Safety and Health Administration ruling that all hand‐held blow guns must be provided with pressure regulation and relief such that the maximum blocked static pressure could not exceed 30 psig. At a supply pressure of 100 psig a noise level variation of 63 dBA was found between the quietest and noisiest guns. Nearly the same degree of variation was demonstrated when the supply pressure was adjusted for each gun to yield equal force downstream. Guide lines will be given for the selection of nozzle design to yield minimum noise exposure consistent with downstream force requirements.