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.

Thermo-mechanical energy converter

Abstract: The invention presents a continuous thermodynamic process which occurs between two different temperature levels and in which the heat power fed at the higher temperature to the working medium which is in the form of gas or vapour is converted into an equivalent amount of pressure energy minus the cooling power. This object is achieved with the aid of two identical working cylinders each with a displacement piston, which pistons can be moved backwards and forwards in a sinusoidal shape phase-shifted through 180 DEG . The heating energy of a fluid or gaseous fuel is fed at a high temperature to the cylinder heads via heat exchangers of the same kind in a common combustion chamber; the processing heat at ambient temperature is conducted away via identical heat exchangers which are connected to the colder working volumes of the cylinders. The heat exchangers for the higher and lower temperature level are connected to one another separately for each cylinder by means of pipelets which are connected in parallel by means of one train and are in good thermal contact and form a common countercurrent heat exchanger. Each of the colder working spaces of the cylinder is connected to two pressurized gas buffers via two non-return valves with opposing transmitting direction, in which buffers the working medium is stored at different pressures. If the two pressure accumulators are connected via a rotating or oscillating expansion motor, mechanical work is produced. A particularly compact...

Experimental Investigation of a Friction Ventilator

Abstract: Standard decentralized ventilation systems typically consist of two ventilators for inlet and exhaust air and a heat exchanger for the heat recovery. A recently developed device, a so called friction ventilator, combines these three elements into a single functional element. The ventilator consists of circular plates which are rotating centrally in between the inlet and the outlet duct of a ventilation system and generate a countercurrent flow in the two ducts. Furthermore, the discs act as a rotating heat exchanger between the two air flows. To increase understanding of the energy transfer from the rotating discs to the flow an experimental investigation on the effect of different rotor geometries was conducted. The study showed an interesting influence of the hub diameter on the characteristic curves with a higher pressure difference for an increase in diameter. The results of the heat recovery measurement however were only mildly affected by the hub geometry. Here the distance between the discs, the rotational speed of the discs and the volumetric flow seemed to have the greatest effect on heat recovery.

Production of prussic acid based on andrussow process

Abstract: PROBLEM TO BE SOLVED: To preferably control the exothermic reaction and to easily assemble into a large-size device by using the reaction heat generated in the reaction to heat the starting gas to the required reaction temp by indirect heat exchange based on the countercurrent principle SOLUTION: As for the reactor, a reversal countercurrent reactor consisting of two concentric tubes comprising a tightly sintered aluminum oxide ceramic material is used The inner tube 1 is equipped with a catalyst bed 3 at the upper end part, while the outer tube 2 is closed at the top end, namely, the top of the reactor When the starting gas mixture is introduced from the lower side to the inner tube 1, the mixture passes through the catalyst bed 3 and turns downward in the ringlike space between the inner tube 1 and the outer tube 2 At the initiation of the reaction, it is necessary to heat the starting gas mixture and the catalyst to >=800 degC This heating process is carried out by direct heating of the catalyst by a heater jacket or a current surrounding the outer tube 2 After the reaction is initiated, it is enough to use the generated reaction heat to heat the starting gas mixture to the reaction temp

Combination direct and indirect closed circuit evaporative heat exchanger

Abstract: A heat exchange apparatus (10) which can be used as an evaporative condenser, fluid cooler or wet-air cooler, is provided with a direct evaporative heat exchange section (90) overlying an indirect evaporative heat exchange section (50). An air entry zone (120) common to both heat exchange sections (50;90) receives an air stream blown into this zone by at least one fan (24), thereby pressurizing the plenum such that the air stream is forced to split and enter each section (50;90) while inside the apparatus. This eliminates the need for separate air entries, thus condensing the size and cost of the apparatus, while increasing heat exchange capacity. A countercurrent air flow pattern through the direct section (90) provides a uniformly cooled evaporative liquid for use in the indirect section (50). The evaporative liquid flow is parallel to the air stream provided in the indirect section. A process fluid inside the circuits of the indirect section (50) can accept or reject heat from the evaporative liquid received from the direct section (90), with a part of the heat being transferred into the indirect section air stream in sensible and latent form, thus increasing or decreasing the enthalpy of the air stream. The remaining heat can be either stored or released from the evaporative liquid to increase or decrease its temperature. The evaporative liquid is collected in a sump (30) and then pumped upwardly for re-distribution across the direct evaporative heat exchange section (90).

Mathematical Model of Maximum Commutation Half Cycle for Thermal Countercurrent Oxidation of Low-Concentration Gas in Coal Mine Ventilation

Abstract: The Fluent computational fluid dynamics software was used to study the relevant factors affecting the maximum commutation half cycle for thermal countercurrent oxidation of low-concentration gas in coal mine ventilation. Based on orthogonal experiments, the maximum commutation half cycle for thermal countercurrent oxidation of the exhaust gas in the coal mine ventilation under 25 working conditions with the combination of different methane concentrations, inlet speeds, porosities, and oxidation bed filling lengths is investigated. SPSS data processing software was used to perform regression analysis on the numerical simulation data, and a mathematical model for predicting the maximum commutation half cycle under the influence of four factors was obtained. Through experiments, the mathematical model of the maximum commutation half cycle by the numerical simulation was verified. After introducing the wall heat loss correction coefficient, the complete prediction model of the maximum commutation half cycle was obtained. Comparing the experimental test value with the calculated value using the corrected model, the relative error was not more than 3%. The complete mathematical model corrected can be applied to the design calculation of the maximum commutation half cycle for thermal countercurrent oxidation of low-concentration gas in actual coal mine ventilation.