Pressure backing

The methane warms to 10°C. It then passes through the booster compressors on the expansion turbine shaft, increasing in pressure from 325 psi to 375 psi before being introduced into other gas compressors tliat boost the pressure back up to 600 psi. This is the pressure needed for reintroduction of the natural gas back into the TransCanada pipeline. This 50 psi boost, which makes use of available energy from the expansion turbines, provides a significant savings in electrical power. 

The inerts will blanket a portion of the tubes. The blanketed portion has very poor heat transfer. The column pressure is controlled by varying the percentage of the tube surface blanketed. When the desired pressure is exceeded, the vacuum system will suck out more inerts, and lower the percentage of surface blanketed. This will increase cooling and bring the pressure back down to the desired level. The reverse happens if the pressure falls below that desired. This is simply a matter of adjusting the heat transfer coefficient to heat balance the system. 

The Seal Drum - A typical flare seal drum for an elevated flare stack is illustrated in Figure 7. A baffle maintains the normal water level, and the vapor inlet is submerged 75 mm to 100 mm. Drum dimensions are designed such that a 3 m slug of water is pressured back into the vertical inlet piping in the event of... 

An important design detail is that the inlet line should be sloped at least 30" from the horizontal and the diameters of the vertical and sloped legs of the Y-seal are sized such that a 3 m slug of water is pressured back up the sloping inlet line, without spilling over into the header, in the event of flashback. Note that this requires an enlarged diameter section in the vertical leg of the Y-seal. The seal is maintained by a continuous flow of water at 1.26 dm /s and the water makeup is provided with steam injection, if required for winterizing or cold releases. 

Back-pressure can affect either the set pressure or the capacity of a relief valve. The set pressure is the pressure at which the relief valve begins to open. Capacity is the maximum flow rate that the relief valve will relieve. The set pressure for a conventional relief valve increases directly with back-pressure. Conventional valves can be compensated for constant back-pressure by lowering the set pressure. For self-imposed back-pressure—back-pressure due to the valve itself relieving—-there is no way to compensate. In production facility design, the back-pressure is usually not constant. It is due to the relief valve or other relief valves relieving into the header. Conventional relief valves should be limited to 10% back-pressure due to the effect of back-pressure on the set point. 

The hydrogen pressure-drop corresponds to 0.325-0.335 mole (99-102%). When the hydrogen pressure drops below about 15 p.s.i., the hydrogen should be replenished in the reservoir tank to bring the pressure back up to about 30 p.s.i. The checkers found a reduction period of 4-6 hours sufficient the submitters routinely used a 24-hour reduction period. 

For any load of a given steam turbine with fixed inlet pressure, back-pressure and inlet temperature, the isentropic... 

A decrease in blood volume or blood pressure may result in a decrease in the blood flow to the kidney. The kidney monitors renal blood flow by way of stretch receptors in the vessel walls. A decrease in renal blood flow stimulates the release of renin. The subsequent secretion of aldosterone causes retention of sodium and water and, therefore, an increase in blood volume and blood pressure back to normal. An increase in renal blood flow tends to cause the opposite effect. 

Hypertension (blood pressure >140/90 mmHg) may be caused by an elevation in cardiac output or excessive vasoconstriction. Diuretics are used in these patients to reduce cardiac output. Assume that the hearts of these individuals are operating on the ascending portion of the cardiac function curve. As the plasma volume is reduced in response to treatment with diuretic drugs, venous return and preload are reduced, as are ventricular filling and stroke volume, and cardiac output, thus bringing blood pressure back within the normal range. 

A 12 in. ID gas pipeline carries methane (MW = 16) at a rate of 20,000 scfm. The gas enters the line at a pressure of 500psia, and a compressor station is located every 100 mi to boost the pressure back up to 500psia. The pipeline is isothermal at 70°F, and the compressors are adiabatic with an efficiency of 65%. What is the required horsepower for each compressor Assume ideal gas. 

Enantiomeric discrimination and its relation to film component reorganization upon compression can also be observed in dynamic surface tension hysteresis loops. Figure 26 shows the WjA isotherms generated upon five successive compression/expansion cycles (from II = 0 to lOdyncm-1) of racemic and enantiomeric films containing 17 mole percent palmitic acid. The hysteresis loops, obtained on the apparatus described in Section 2 (p. 63), show that the first compression/expansion cycle of the racemic system is repeated in each successive cycle. Upon expansion of the film from the maximum surface pressure back to Odyncm-1, the racemic film returns to its original state without detectable reorganization of the components. However, the... 

Chiruvella, R. V., Jaluria, Y., Sernas, V., and Esseghir, M., Extrusion of Non-Newtonian Fluids in a Single-Screw Extruder with Pressure Back Flow, Polym. Eng. Set, 36, 358 (1996)... 

The ASE system is fully automated. An autoseal actuator moves the cell from the carousel into the heating oven. The solvent is delivered from one or more solvent bottles into the extraction cell by a pump. The oven is heated, and the temperature and pressure in the cell rise. When the pressure reaches 200 psi above the preset value, the static valve opens to release the excessive pressure and then closes again. Then the pump delivers fresh solvent to the cell to bring the pressure back to the preset value. The addition of fresh solvent increases the concentration gradient and enhances both mass transfer and extraction efficiency. The extracts are collected in 40 or... 

Place the system under a static pressure (back pressure) of nitrogen or argon and immerse it in a dry ice-bath. 

Return to homeostasis when increased cardiac output and increased vascular resistance bring blood pressure back to normal... 

The bypassed vapor heats up the liquid there, thereby causing the pressure to rise. WTien the bypass is closed, the pressure falls. Sufficient heat transfer surface is provided to subcool the condensate, (f) Vapor bypass between the condenser and the accumulator, with the condenser near ground level for the ease of maintenance When the pressure in the tower falls, the bypass valve opens, and the subcooled liquid in the drum heats up and is forced by its vapor pressure back into the condenser. Because of the smaller surface now exposed to the vapor, the rate of condensation is decreased and consequently the tower pressure increases to the preset value. With normal subcooling, obtained with some excess surface, a difference of 10-15 ft in levels of drum and condenser is sufficient for good control, (g) Cascade control The same system as case (a), but with addition of a TC (or composition controller) that resets the reflux flow rate, (h) Reflux rate on a differential temperature controller. Ensures constant internal reflux rate even when the performance of the condenser fluctuates, (i) Reflux is provided by a separate partial condenser on TC. It may be mounted on top of the column as shown or inside the column or installed with its own accumulator and reflux pump in the usual way. The overhead product is handled by an alter condenser which can be operated with refrigerant if required to handle low boiling components. 

If the tension, P2, is not sufficient to spall the material, a tension wave travels both to left and right. If the tension is sufficient to spall the material, then the material parts, dropping the pressure back to P = 0, and forms two free surfaces that fly away in each direction at the particle velocity magnitude u. ... 

The pressure and liquid level in the chlorine vaporizer are controlled automatically. As vapor flows out the top. the pressure in the tank begins to decrease. A pressure sensor detects the drop and sends a signal to the steam flow control valve. The valve opens and feeds more steam to the coil, causing more liquid chlorine to evaporate and raising the pressure back to the desired value. As the liquid evaporates, the liquid level in the tank begins to drop. A liquid level sensor detects the drop and sends a signal to the liquid chlorine flow control valve. The valve opens, and more liquid enters the tank to replace the liquid that evaporated, raising the liquid level back to the set-point (desired) value. 

The feed rate of chlorine to the absorber is automatically controlled to maintain the absorber pressure at a specified value. If the pressure begins to fall, a pressure sensor detects the drop and sends a signal to the expansion valve described in Step 3. The valve opens, causing the flow rate of chlorine to increase and raising the absorber pressure back to the set-point value. It the pressure rises above the set point, the pressure sensor sends a signal that adjusts the control valve to decrease the flow rate of chlorine and the pressure comes back down to the set-point value. 

It is a good idea to check such results by inserting the calculated equilibrium partial pressures back into the equilibrium expression to make sure that the known value of K comes out. 

One kilogram of steam goes through the following reversible process. In its initial state (state 1) it is at 2700 kPa and 540 C. It is then expanded isothermally to state 2, which is at 700 kPa. Then it is cooled at constant volume to 400 kPa (state 3). Next it is cooled at constant pressure to a volume of 0.4625 mVkg (state 4), Then it, is compressed adiabatically to 2700 kPa, and 425 C (state 5), and finally it is heated at constant pressure back to the original state. 

The significance of the reversibility of the above processes is that at the end of the cycle the system is brought back to its starting point with no losses incurred due to friction or other causes. Thus, as the system temperature is restored to its starting point Tp its pressure is also restored to its starting level of Pp If the processes are not reversible, additional work would have to be done on the system to bring the pressure back to Pp The net work would be less than g, - 2i and the efficiency would be lower than the Carnot efficiency. 

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