Transfer piston

After the mould has closed, but before final clamping, a measured quantity of rubber is injected into the transfer port. The rubber forces the transfer port open until it contains the required volume. With a top injection system the mould is forced downwards and the transfer piston remains stationary. With a bottom injection unit the mould is stationary and the transfer piston is raised. In both cases the effective volume of the port is increased by the filling action of the rubber. 

In view of the difficulties in determining gas transfer coefficients accurately, direct methods for CO2 flux measurements aboard the ship are desirable. Sea-air CO2 flux was measured directly by means of the shipboard eddy-covariance method over the North Atlantic Ocean by Wanninkhof and McGillis in 1999. The net flux of CO2 across the sea surface was determined by a covariance analysis of the tri-axial motion of air with CO2 concentrations in the moving air measured in short time intervals ( ms) as a ship moved over the ocean. The results obtained over awind speed range of 2-13.5 m s are consistent with eqn [3] within about +20%. If the data obtainedin wind speeds up to 15 m s are taken into consideration, they indicate that the gas transfer piston velocity tends to increase as a cubeof wind speed. However, because of a large scatter ( + 35%) ofthe flux values at high wind speeds, further work is needed to confirm the cubic dependence. 

In order to study asphaltene precipitation from live oil systems at reservoir conditions and to study effect of pressure on amount of asphaltene precipitation, experimental set up was assembled. Figure 11 is a schematic diagram of the setup used. The major components of the set up include 1) JEFRI positive displacement pump, 2) recombination cell, 3) solvent transfer (pistoned) cell, 4) stainless steel (60 micron) In-line filter, 5) air bath equipped with temperature controller and rocking mechanism. Positive displacement pump was used either to inject gas during recombination of oil or to inject CO2 at constant pressure into recombination cell to prepare desired CO - recombined oil mixture. 

Unlike the compression mold, there is no loading chamber in the transfer mold. Instead, it has a centrally arranged heating cylinder with transfer piston. This distinction in the arrangement of the transfer piston is shown below ... 

Figure 1.79 (b) shows the mold for the transfer molding process from the bottom. A press with a separate injection unit is required for molds of this design. Most commonly, these are presses with a hydraulic cylinder that is centrally attached to the mold table. This actuates the transfer piston which is linked to the machine control (transfer press). 

Transfer piston (2) transfer cyiinder (3) fiash opening (4) external clamping (5) upper mold half (6) lower mold half... 

Test mold for transfer molding process (1) Upper clamping plate (2) transfer piston (3) external clamping (4) mold core (5) transfer cylinder (6) bypass channel (7) mold leader pin (8) upper mold half (9) hand grip (10) lower mold half (11) lower clamping plate... 

Fig. 17. Effect of axial dispersion in both phases on solute distribution through countercurrent mass transfer equipment. A, piston or plug flow B, axial...

Hydraulic piston-type compactors for collection vehicles, on-site compactors, and transfer-station compactors roll crushers used to fracture brittle materials and to crush tin and aluminum cans and other ductile materials... 

The temperature is approximately 20°F below the 265°F temperature limit. The sections differ by less than 1 F. This is probably just luck because that good a balance is not really necessary. Also, it should be noted that to maintain simplicity the additional factors were ignored, such as the 10°F temperature pickup in the return stream due to internal wall heat transfer. Also, nozzle pressure drops for the exit and return were not used. Balance piston leakage was not used as it was in Example 5-3. When all the factors are used, the pressures for each section would undoubtedly need additional adjustment as would the efficiency. However, for the actual compression process, the values are quite realistic, and for doing an estimate, this simpler approach may be quite adequate,... 

Steam turbines, which generate more than 80 percent of the world s electric power, differ from steam engines m that steam drives blades and not pistons. Steam turbines expand pressurized steam through nozzles that accelerate the steam at the expense of heat energy and pressure. Work is created by transferring a portion of steam velocity to blades, buckets, or nozzles affixed to a rotor to move at high speeds. Steam turbines are relatively compact in relation to steam... 

One pound-mole of an ideal gas is compressed at a constant pressure of 1 atm in a piston-like device from an initial volume of 1.5 ft to a final volume of 0.5 ft. The internal energy is known to decrease by 20 Btu. How much heat was transferred to or from the gas ... 

The use of hydraulic systems for the setting, operation and control of machine tools has increased significantly. Hydraulic mechanisms being inter-linked with electronic controls and/or feedback control systems. In machine tools, hydraulic systems have the advantage of providing stepless and vibration-less transfer of power. They are particularly suitable for the linear movement of tables and slideways, to which a hydraulic piston may be directly coupled. 

Self-Test 6.6B Suppose that 1.00 kj of energy is transferred as heat to oxygen in a cylinder fitted with a piston the external pressure is 2.00 atm. The oxygen expands from 1.00 L to 3.00 L against this constant pressure. Calculate w and AU for the entire process by treating the 02 as an ideal gas. 

It is seen in figure (4) that the total air pressure on the piston, diameter (y), is transferred to a piston controlling the liquid pressure of diameter (x). Because the radii of the pistons differ, there will be a... 

Here Ac = Ca - XhCw with Cg and Cw representing the concentrations in the air and water respectively and Kh the Henry s law constant. The parameter K, linking the flux and the concentration difference, has the dimension of a velocity. It is often referred to as the transfer (or piston) velocity. The reciprocal of the transfer velocity corresponds to a resistance to transfer across the surface. The total resistance R — K ) can be viewed as the sum of an air resistance (i a) and a water resistance (Rw). ... 

The piston velocity, or gas transfer velocity, is a function of wind speed. There are large differences in the relationships between piston velocity and wind speed, especially at liigher wind speeds (e.g., Liss and Merlivat, 1986 Wannin-khof, 1992). This is the limiting factor for these calculations. 

The units on A are mol/(m s). This is the convective flux. The student of mass transfer will recognize that a diffusion term like —3>Adaldz is usually included in the flux. This term is the diffusive flux and is zero for piston flow. The design equation for the variable-density, variable-cross-section PFR can be written as... 

These simple situations can be embellished. For example, the axial dispersion model can be applied to the piston flow elements. However, uncertainties in reaction rates and mass transfer coefficients are likely to mask secondary effects such as axial dispersion. 

Values for the various parameters in these equations can be estimated from published correlations. See Suggestions for Further Reading. It turns out, however, that bubbling fluidized beds do not perform particularly well as chemical reactors. At or near incipient fluidization, the reactor approximates piston flow. The small catalyst particles give effectiveness factors near 1, and the pressure drop—equal to the weight of the catalyst—is moderate. However, the catalyst particles are essentially quiescent so that heat transfer to the vessel walls is poor. At higher flow rates, the bubbles promote mixing in the emulsion phase and enhance heat transfer, but at the cost of increased axial dispersion. 

---