Low-pressure side

The transition from k to on the low-pressure side ean be eonstnieted using iiiidtidimensional unimoleeular rate theory [1, 44], if one knows the barrier height for the reaetion and the vibrational frequeneies of the reaetant and transition state. The transition from to k y ean be deseribed in temis of Kramers theory [45]... 

AH these devices are fiUed with sHicone oil and have low gradient, corrosion-resistant barrier diaphragms on both the high and low pressure sides of the sensor. 

The pressure difference between the high and low pressure sides of the membrane is denoted as AP the osmotic pressure difference across the membrane is defined as Att the net driving force for water transport across the membrane is AP — (tAtt, where O is the Staverman reflection coefficient and a = 1 means 100% solute rejection. The standardized terminology recommended for use to describe pressure-driven membrane processes, including that for reverse osmosis, has been reviewed (24). 

If the power requirement of the gaseous diffusion process were no greater than the power required to recompress the stage upflow from the pressure on the low-pressure side of the barrier to that on the high-pressure side, then the power requirement of the stage would be Z RTLq (1 /r) for the case where the compression is performed isotherm ally. The power requirement per unit of separative capacity would then be given simply by the ratio... 

Bearing lubrication oil from the outboard or low-pressure side of the seal. 

If a tube breaks, pressure on the exehanger low-pressure side can spike to a level that exceeds the pressure predicted by a steady-state analysis. This spike is due to pressure buildup before the fluid accelerates out of the shell and/or before the relief device fully opens. 

Stage 1 may last less than one second to several seconds. It is characterized by a very fast transient and a pressure spike immediately after the tube rupture. After the low-pressure side fills with high-pressure fluid, the transition to stage 2... 

A vapor poeket on the exchanger s low-pressure side can create a cushion that may greatly diminish the pressure transient s intensity. A transient analysis may not be required if sufficient low-pressure side vapor exists (although tube rupture should still be considered as a viable relief scenario). However, if the low-pressure fluid is liquid from a separator that has a small amount of vapor from flashing across a level control valve, the vapor pocket may collapse after the pressure has exceeded the fluid s bubble point. The bubble point will be at the separator pressure. Transient analysis will prediet a gradually inereasing pressure until the pressure reaches the bubble point. Then, the pressure will increase rapidly. For this ease, a transient analysis should be considered. 

Transient Analysis (dynamic simulation) is recommended where there is a wide difference in design pressure between the two exchanger sides, especially where the low-pressure side is liquid-filled (section 3.18.3). 

The first guideline is often referred to as the "two-thirds rule." The basis of this rule is that if the low pressure side is designed for two-thirds of the high pressure side design pressure, the exchanger hydrotest pressure will not be exceeded due to a tube rupture. 

API RP-521 reeommends transient analysis for exchangers with wide difference in design pressure (such as cases where the two-thirds rule was not applied) because the pressure in the low pressure side of the exehanger ean spike to a level that exceeds the pressure predicted by a steady state analysis when it is liquid-filled. This pressure spike is due to pressure buildup before the liquid is accelerated out of the low pressure side and/or before the relief device opens fully. API RP-521 recommends that the basis for the tube rupture be a sharp... 

The most common membrane systems are driven by pressure. The essence of a pressure-driven membrane process is to selectively permeate one or more species through the membrane. The stream retained at the high pressure side is called the retentate while that transported to the low pressure side is denoted by the permeate (Fig. 11.1). Pressure-driven membrane systems include microfiltration, ultrafiltration, reverse osmosis, pervaporation and gas/vapor permeation. Table ll.l summarizes the main features and applications of these systems. 

The driving force for the separation is differential pressure. CO2 tends to diffuse quickly through membranes and thus can be removed from the bulk gas stream. The low pressure side of the membrane that is rich in CO2 is normally operated at 10 to 20% of the feed pressure. 

Step 6a. First calculate the mol of propane and hutane vapor in the low pressure side ... 

At the low-pressure side of the reducing valve it is usually essential to fit a relief or safety valve. If any of the steam-using equipment connected to the low-pressure range is designed to withstand a pressure below that of the upstream steam supply, then a safety valve is mandatory. Further, it may be called for when it is sought to protect material in process from over-high temperatures (Figure 22.9). 

Figures 8.5 and 8.6. The liquid is carried round in the spaces between consecutive gear teeth and the outer casing of the pump, and the seal between the high and low pressure sides of the pump is formed as the gears come into mesh and the elements of fluid are squeezed out. Gear pumps are extensively used for both high-viscosity Newtonian liquids and non-Newtonian fluids. The lobe-pump (Figures 8.7 and 8.8) is similar, but the gear...

Vapour-pressure-dependent up to svp, supplying the same data as in (1) per test tests likely to be medium-term to give sufficient permeant for reliable measurement. Can reduce vapor pressure (e.g., by using a carrier gas) on low-pressure side to maximize permeation by keeping P2 near-zero. 

Essentially pressure-independent only permeation rate and D readily obtainable medium-long tests (again can be shortened by reducing vapor pressure on low pressure side). 

In the other three membrane processes, for example, in RO, a membrane is mounted in an apparatus so that a two-section compartment is formed. Contaminated water is pressurized and circulated through the high-pressure-solution compartment. Water permeates to the low-pressure side and is removed. The concentrated brine is removed separately. 

---