Countercurrent exchange

About: Countercurrent exchange is a research topic. Over the lifetime, 2255 publications have been published within this topic receiving 28687 citations. The topic is also known as: Countercurrent exchange.

Countercurrent Concentration of Gases and Development of Dynamic Surface Remodeling

Abstract: Author(s): Brubaker, Kyle | Advisor(s): Esser-Kahn, Aaron P | Abstract: Nature, while slow to change, has had the benefit of billions of years competitive pressure to hone approaches to interesting problems. In this work, we take advantage of this preexisting work, and make progress towards replicating the benefits found in nature in artificial systems. Taking inspiration from dynamic, living structures such as bone, and muscle, we demonstrate partial synthetic recreations of the conceptual pieces required to mimic such materials. Diffusion controlled etching is used to demonstrate functional optimization of preexisting structures. Incorporating growth into the system allows dynamic, reversible changes in structure to take place. We show the migration of a channel through a solid matrix. We also took inspiration from deep sea fish to develop a device that concentrates gas more efficiently than a simple countercurrent flow separator. Existing methods including hollow fiber membrane contactors, vacuum swing adsorption, and cryogenic distillation represent a significant portion of the worlds energy needs. Countercurrent amplifiers found in the swimbladders of teleost fish, can efficiently concentrate gases at least 15,000 times above the ambient concentrations. Incorporating the architecture found in the swim bladders of deep sea fish with modern CO2 and O2 capture fluids enables a feedback loop of concentration within our artificial device to drive an increase in the release rates of both gases.

A high performance cocurrent-flow heat pipe for heat recovery applications

Abstract: By the introduction of a plate-and-tube separator assembly into a heat pipe vapor core, it has been demonstrated that axial transport capacity in reflux mode can be improved by up to a factor of 10. This improvement is largely the result of eliminating the countercurrent shear that commonly limits reflux heat pipe axial capacity. With benzene, axial heat fluxes up to 1800 W/sq cm were obtained in the temperature range 40 to 80 C, while heat flux densities up to 3000 W/sq cm were obtained with R-11 over the temperature range 40 to 80 C. These very high axial capacities compare favorably with liquid metal limits; the sonic limit for liquid sodium, for example, is 3000 W/sq cm at 657 C. Computational models developed for these cocurrent flow heat pipes agreed with experimental data within + or - 25%.

Continuous cocurrent processes in the nonsteady state

Abstract: Although continuous heat- and mass-transfer processes are usually conducted in countercurrent flow, there are certain cases in which the cocurrent flow can be used to some advantages from an operation point of view. For example, in the packed adsorption column, flooding due to high vapor or gas flow rate can be eliminated if cocurrent flow is employed. Use of cocurrent flow can also reduce the pressure drop requirement in the packed column. Reiss (1967) discussed several instances in which cocurrent mode operation may be favored over countercurrent flow. In the case of heat transfer, cocurrent flow is also suitable for some special situations. For instance, if it is necessary to limit the maximum temperature of cooler fluid or if it is important to change the temperature of at least one fluid rapidly (McCabe et al., 1985). The transient behaviors of both cocurrent and countercurrent processes are important in the startup and control of mass- and heat-transfer operations. Previously, numerical solutions based on a method of characteristics was used to study the transients of countercurrent processes (Tan and Spinner, 1984). Owing to the split boundary conditions, analytic solutions are difficult to obtain even for the linear system. For cocurrent flow, compact analytic solutions in terms of well-known tabulated function can be derived. The purpose of this note is to present the nonsteadystate behavior of continuous cocurrent flow of two contacting phases. The transient responses to the inlet disturbances are derived based on a simple mathematical model. This simplified model is equally applicable to either mass- or heat-transfer processes. Laplace transformation method is used to obtain compact analytic solutions. These solutions can be easily evaluated with the aid of the known tabulated mathematical functions or charts. Both the derivation and the final form of solutions are easier to apply in comparison to the work of Li (1986).

Quickly-heating type instant-boiling air heat energy heat pump water boiler

Abstract: The utility model discloses a quickly-heating type instant-boiling air heat energy heat pump water boiler which comprises an air heat energy heat pump system and a boiling water control processing system. The air heat energy heat pump system and the boiling water control processing system are connected by a condenser assembly, wherein the condenser assembly is internally provided with a refrigerant heat carrying pipe and a water system pipe which are both of an independent loop countercurrent structure. The multilevel temperature difference heat release and ascending heat extraction technical principle is creatively adopted in the utility model, the outlet water temperature of a monopolar heat pump is improved to 100 DEG C above by using the condenser assembly, boiling water is produced; in addition, after flowing over a undercooling device, refrigerant keeps good low temperature state at a throttle valve so as to ensure that the refrigerant entering an evaporator can evaporate and absorb heat from environmental air efficiently and further better reduce environmental temperature to achieve refrigerating effect; therefore, the quickly-heating type instant-boiling air heat energy heat pump water boiler can be used for improving and adjusting the refrigerating effect of air indoors.