Loop-type system

The Turbocraft water tunnel is a closed loop type system. Suction and discharge pressure taps are located the prescribed distances from the pump in accordance with the Hydraulic Institute code. The flow is measured using a sharp-edged orifice. The calibration of the orifice plate is based on NACA data. For cavitation testing a vacuum pump is used to obtain the desired tank pressurization value below atmospheric pressure,... 

In a sample loop type system, a probe is located in the main pipeline and directs a portion of the fluid flow into the sample loop. This probe may be a 90 elbow or a 45 level facing upstream (see 10.2). The average flow velocity through the sample loop shall be near the maximum average velocity expected in the main pipeline, but not less than 2.5 m/s (8 ft/s). 

In this section, the systematic search for conical intersections based on the Longuet-Higgins phase-change rule is described. For conciseness sake, we limit the present discussion to Hiickel-type systems only, unless specifically noted otherwise. The first step in the antilysis is the determination of the LH loops containing a conical intersection for the reaction of interest. 

In order to achieve the widest application range, partially concurrent solvent evaporation (PCSE) with an on-column interface is normally used during the transfer of analytes from the LC-type precolumn to the GC system. Eully concurrent solvent evaporation (ESCE), with a loop-type interface, is used in some cases, although the... 

A more sophisticated method, giving a much more detailed characterization, involves the on-line coupling of EC and GC (LC-GC). Analysis schemes for middle distillates (kerosine, diesel and jet fuels) combining EC and GC have been reported by various authors (25-31). However, only Davies et al. (25) andMunari et al. (27) have reported on the required automatic transfer of all of the individual separated fractions from the EC unit the GC system. Davies used the loop-type interface and Munari the on-column interface. Only Beens and Tijssen report a full quantitative characterzation by means of LC-GC (31). 

Recycling of partially reacted feed streams is usually carried out after the product is separated and recovered. Unreacted feedstock can be separated and recycled to (ultimate) extinction. Figure 4.2 shows a different situation. It is a loop reactor where some of the reaction mass is returned to the inlet without separation. Internal recycle exists in every stirred tank reactor. An external recycle loop as shown in Figure 4.2 is less common, but is used, particularly in large plants where a conventional stirred tank would have heat transfer limitations. The net throughput for the system is Q = but an amount q is recycled back to the reactor inlet so that the flow through the reactor is Qin + q- Performance of this loop reactor system depends on the recycle ratio qlQin and on the type of reactor that is in the loop. Fast external recycle has... 

This brief overview of separate treatment techniques is not complete, however it can be used for a first inventory and identification of treatment steps which may be considered as part of a complete closed loop water system. It has to be taken in mind that the above-mentioned overview of separate treatment techniques is primarily based on one type of pollutant and one physical state of that pollutant. It will be clear that very often the same treatment step can be applied to remove different types of pollutants. It is also evident that a large percentage of the separate treatment steps mentioned will result in a concentrate containing the pollutants. This concentrate has to be treated subsequently. 

As a first approach it is assumed that an industrial closed water loop focuses on the production of one type of process water of a constant water quality and temperature. After this process water has been polluted and has become a wastewater, it will be treated to the required quality and will be used again as process water. In fact this is the simplest form of a closed loop water system. We will discuss this situation first. The first step in the design of such a simple closed loop water system is to consider the type of separate treatment steps and the sequence of these treatment steps which have to be applied on a wastewater stream that contains large amounts of easily biodegradable soluble pollutants in addition to non-biodegradable soluble organic and inorganic pollutants and suspended and colloidal particulate... 

In the aforementioned closed loop water system the polluted process water is purified completely in one wastewater treatment scenario. Only one type of process water is produced for reuse. In practise several types of process water are needed, and also several types of polluted wastewater streams are produced. This is schematically shown in Figure 2. In that case it can be advantageous in technical, economic and environmental respects to include several closed loop water systems within one production line. 

In general, it can be expected that several types of closed loop water systems will be technically feasible for any particular industrial facility. 

The injector system is often of the loop type. Here the main solvent delivery tube to the column top is by-passed in a loop, which may be isolated and depressurised, and injected with sample via a septum. After injection the liquid in the loop is released into the main solvent flow. The loop volume is of comparable capacity to the injection volume. Most instruments are designed for autosampling in the case of multiple analyses, the operation being controlled by the instrument software. 

The closed-loop type artificial pancreas (specifically 8-cell), which consists of an automatic continuous monitor of blood glucose level (BGL) and an automatic injector of insulin which are coupled with feed-back system, has great potential for prevention of diabetic complication such as micro-angiopathies(l). A large-scale closed-loop type artificial pancreas for bedside use has already been developed and is clinically used at some laboratories and hospitals (2-4). However, this device is limited to only bedside use. On the other hand, the open-loop type artificial pancreas which consists of only a insulin injecting pump without an automatic continuous monitor of BGL, has been developed and is going to be clinically used(5-7). This system, however, can not completely control BGL as well as the bare pancreas in a normal body and often causes lower BGL(8-9). 

In order to provide for the complete therapy of diabetic patients, an implantable or portable closed-loop type artificial pancreas must be developed. The key factor in the development of such system is development of a small-size glucose sensor which is able to measure directly up to 500-700 mg/dl of BGL in a blood stream or in a body fluid. 

On-Line Systems Flowing MMLLE systems have been established in different layouts with automation and on-line hyphenation to GC and HPLC analysis. An automated on-line FS-MMLLE-GC system with a loop-type interface compatible with LVI was used for the extraction of pesticides and PAHs in surface waters.86 In another study, pressurized hot water extraction (PH WE) was coupled on-line to a FS-MMLLE-GC-FID system and applied to the analysis of PAHs in soil, where MMLLE was used as a cleanup and concentration step of the PH WE extract prior to final GC analysis.87 In addition, an HF-MMLLE setup was incorporated in PHWE and GC, resulting in an online PHWE-HF-MMLLE-GC system, where the HF membrane module contained 10-100 HFs. The system served for the extraction and analysis of PAHs in soil and sediments ... 

Computer-controlled automatic profile dies with electrical controlled sensors in closed-loop control systems have developed greater efficiency and accuracy to extrusion coating, cast film, and sheet lines. A scanner measures the web thickness and signals the computer, which then converts the readings to act on thermally actuated die bolts. The individual adjusting bolts expand or contract as ordered by the computer to control the profile. The more sophisticated systems measure adjusting bolt temperature and provide faster response time with less scrap and quicker startups. The scanner is typically an infrared, nuclear, or caliper-type gauge. 

In the process, homopolymer and random copolymer polymerization occurs in the loop-type reactor (or vessel-type reactor) (1). For impact copolymer production, copolymerization is performed in a gas-phase reactor (2) after homopolymerization. The polymer is discharged from a gas-phase reactor and transferred to the separator (3). Unreacted gas accompanying the polymer is removed by the separator and recycled to the reactor system. The polymer powder is then transferred to the dryer system (4) where remaining propylene is removed and recovered. The dry powder is pelletized by the pelletizing system (5) along with required stabilizers. 

Liquid chromatograph. The instrument should be one that is designed for use with stainless steel columns and is equipped with a pumping system able to maintain a pressure of 15 MPa a UV spectrophotometer detector able to measure UV absorbance at 254nm and a loop-type injector. 

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