Gas exchange devices

Extracorporeal blood gas exchange devices have been used on infants with the respiratory distress syndrome (RDS) (4, 5). Twenty-five thousand newborns are estimated to die from this disease every year in this country (6). Though the causes of this disease are not clearly understood, it is hoped that supporting the infant with the aid of an extracorporeal-gas exchanger will give his own lungs time in which to heal. 

Blood gas exchange devices have either a gas-blood interface, as found in the disk and bubble oxygenators, or a membrane interposed be-... 

Galletti, P. M. and C. K. Colton, 1995, Artificial lungs and blood-gas exchange devices, in The Biomedical Engineering Handbook, J. Bronzino, ed., CRC Press, Boca Raton, FL, pp. 1879-1897. 

Oxygen concentration Usually low enough because of continuous spontaneous outgassing Build-up in closed system requires gas exchange devices (O2 must be removed to prevent inhibition of photosynthesis and photo oxidative damage)... 

Snyder, T.A. et al. 2006. Blood biocompatibility assessment of an intravenous gas exchange device. Artif Organs 30 657-64. 

Typical heat-recuperation devices are finned gas exchangers, ceramic heat wheels, and Ljungstrom air preheaters. 

There are many other types of heat exchanger devices that can be used to heat the gas above the hydrate temperature. These could include shell and tube heat exchangers, electrical immersion heaters, furnaces, etc. However, the most common equipment type used to heat a well stream is the indirect fired water bath heater. 

The selectivity of ISEs used in flow systems can be boosted by incorporating an on-line separation unit (e.g. an ion-exchange colunm, a dialysis module or a gas-diffusion device) into the hydrodynamic system. Occasionally —particularly when an ion-exchange column is used—, the ancillary... 

For reactors of a larger diameter (e.g. more than 600 mm) it is more advisable to use a bundle of small tubes as heat exchangers. Such a distribution of heat exchange surfaces virtually does not inhibit fluidising and ensures that the heat is efficiently withdrawn from the whole surface of the apparatus. It should be also kept in mind that tube bundles allow one to select the reaction space and place rotating gas distribution devices between sections this considerably increases the coefficient of heat transfer and ensures a more uniform gas distribution in the reaction zone. 

Figure 1 indicates the schematic flow of two-bed pyrolysis plant. This plant consists of the pyrolysis reactor and the regenerator through which fluidized medium circulates, the precombustion burner, the raw material feeder, the cyclones, the heat exchangers, the vapor-liquid separator, the gas recycle blower, the air feeder, the gas cleaner and the produced-gas combustion device. The plant also includes various auxiliary equipment, the devices for measuring and recording flow rate, pressure and temperature, as well as the automatic analysis for gas. 

In conjunction with membrane-based blood oxygenators for example, microchannels offer improved gas exchange efficiency and reduce the volume of blood required for initial priming. A device developed by Himg et al. [281] involves a stack of 16 plate units incorporating 110 pm deep by 230 pm wide microchannels sandwiched with oxygen permeable membranes (Fig. 7.22). Experimental results not only show improved gas exchange efficiency over both macrochannels and theoretical predictions, but also a reduction in apparent blood viscosity. 

Parallel plate mass exchange devices with semi-permeable membranes have been studied in a number of separation techniques including hemodialysis, artificial oxygenation, gas separation, and heavy-metal ion separation C10-18% The accurate prediction of solute separation in these mass exchangers is desirable. For parallel-plate geometry, Grimsrud and Babb C5) and Colton et al. C ) developed series solutions to describe the mass transfer process. Kooljman CB) reviewed the analytical and numerical solutions available in the early 1970 s. Since that time, other... 

Traditional heat recovery included the recovery of heat fron a dryer outlet, the hot dried product, and/or the outlet gas. Typical devices for heat recovery are presented in Figure 54.5. Conventional heat exchangers have the following efficiency indices thermal wheel, 75%-90% plate exchanger, =70% heat pipe, =60% scrubber, =60% and two-section exchanger, =50%. 

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