Countercurrent exchange

D. Winne, The influence of villous countercurrent exchange on intestinal absorption, J. Theor. Biol, 53, 145-176 (1976). 

These traits have received most study in tunas, a group of fishes noted for continuous swimming and for major anatomical differences from other fishes. Of particular importance in the anatomical organization of tunas is the internalization of red muscle, an anatomical feature that appears critical for allowing endothermy to develop. In most fishes, the red muscle is located superficially, where it would be difficult, if not impossible, to prevent loss of metabolically generated heat to the environment. The internalization of the red muscle mass in tunas isolates this tissue from close contact with seawater. There is also an effective isolation from the medium of the circulatory system within red muscle countercurrent exchangers interspersed between red muscle and the arterial circulation supplying the tissue allow much of the heat produced in red muscle to be retained, rather than lost to the environment. 

A vapor-compression refrigeration system is conventional except that a countercurrent exchanger is installed to subcool the liquid from the condenser by heat exchange with the v stream from the evaporator. The minimum temperature difference for heat transfer is 10(°F). Amm is the refrigerant, evaporating at 22(°F) and condensing at 80(°F). The heat load on the evapo is 2,000(Btu)(s) . If the compressor efficiency is 75 percent, what is the power requirement ... 

The ethylbenzene feed needs to be heated and the reactor effluent cooled. Heat exchange between them is feasible and desirable. Setting an approach temperature for a countercurrent exchanger (temperature difference between... 

This is carried out by selective adsorption of olefins in the liquid phase on a solid. The distribution of the circuits is designed to simulate a countercurrent exchange between the liquid and solid phases, wthout any effective movement of the adsorbenn... 

Sometimes sizable attrition of ion exchanger has been considered a disadvantage of countercurrent exchange (see, for example. Ref. 79). In arriving at such a conclusion, however, account has not been taken of the... 

The ethylbenzene feed needs to be heated and the reactor effluent cooled. Heat exchange between them is feasible and desirable. Setting an approach temperature for a countercurrent exchanger (temperature drlference between heated feed and reactor effluent) at 10°C, fixes the heated feed temperature at 590°C (1094°F). An energy balance for the heated feed and steam mixture estabhshes the required steam temperature ... 

If Q < 1, then takes on the character of an efficiency. The normalised temperature change of the fluid with the smaller heat capacity flow is known as the efficiency or effectiveness of the heat exchanger. With an enlargement of the heat transfer area A the temperature difference between the two fluids can be made as small as desired, but only at one end of the countercurrent exchanger. Only for... 

The time required to heat the agitated batch using the double pipe countercurrent exchanger can be determined from Equation 8-170. 

Many methods have been used to achieve partial separation of lithium isotopes on a small scale. Examples of processes and reported separations are listed in Table 12.4. A process somewhat similar to the last one listed in this table, involving countercurrent exchange of lithium isotopes between aqueous lithium hydroxide and lithium amalgam, is to be used in a plant being built... 

To recover and recycle potassium amide, the partially enriched ammonia containing dissolved partially enriched potassium amide leaving the exchange column at (11) is depressured to 55 atm, heated to 125 C, and separated at E into ammonia vapor and a concentrated liquid solution of potassium amide (16). Because this solution contains 1.32 percent deuterium, its deuterium content must be reduced before it is recycled to the top of the stripping exchange column. In Fig. 13.23 this is done by countercurrent exchange with stripped ammonia vapor (9) in the catalyst deuterium stripper F. This is a conventional sieve-plate column in wWch deuterium is transferred from dissolved potassium amide to ammonia vapor in the overall reaction... 

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