Heat exchanger counter-current

Figure 2.52 2-D model of a counter-current heat-exchanger reactor with a nanoporous catalyst layer deposited on the channel wall.

TeGrotenhuis et al. studied a counter-current heat-exchanger reactor for the WGS reaction with integrated cooling gas channels for removal of the reaction heat. The computational domain of their 2-D model on the basis of the finite-element method... 

Fig. 5.11. A schematic counter-current heat exchanger. Tl is the temperature of the input stream, T2 of the output stream. Superscripts H and C signify hot end and cold end respectively.

The secondary circuit uses water from any water distribution network or, when possible, from a centralized cooled-water system. The heat dissipated from the magnet and from the power supply into the primary cooling circuit is transferred to the secondary circuit by means of a high-performance counter-current heat exchanger. 

In this idealization the formation and removal of ice are assumed to be simultaneous, so that the mass flow rate decreases throughout the transition from the initial freezing temperature, Ti to the final temperature, Tf. The above computation of theoretical energy is not dependent upon removal of the ice in this manner, however. Ice formed at temperatures above Tf could, for example, remain in contact with the brine and be cooled to Tf before separation, the cooling being accomplished by perfect counter-current heat exchange with previously formed ice. 

Show that the steady- state and dynamic models for a double-pipe, counter-current heat exchanger can have the same form as the model of a packed bed absorber. Discuss the assumptions inherent in both the heat exchanger and the absorber models which might lead to significant differences in the kinds of model equations used to describe each system. 

Stevens, E.D., Lam, H.M. and Kendall, J. (1974). Vascular anatomy of the counter-current heat exchanger of skipjack tuna. Journal of Experimental Biology 61,145-153. 

Figure 4.112 Monolithic counter-current heat exchanger manufactured from a stack of micro structured plates and sealed by laser welding (source IMM).

The system equations for the counter-current heat exchanger are derived from the enthalpy balance and the heat transfer rate. 

Carbonate Process. In this process the ores are leached with hot sodium carbonate for 24 hours, with sparging with air to provide oxidation. The leachate is cooled in counter-current heat exchangers, heating the carbonate solution for the next batch. The carbonate leachate is filtered on rotary drums, and the uranium is precipitated with sodium hydroxide and filtered. The filtrate is converted back to carbonate by sparging with carbon dioxide, usually from a boiler flue gas, and... 

Agostini shows that for Bi > 3 the convective effects are prominent and for Bii < 0.3 the longitudinal heat flux produces an effect on the temperature profiles. The definition given by Commenge was calculated for counter-current heat exchangers and leads to different valnes. Evalnating these nnmbers would be useful in ensuring the heat flux is purely transversal. 

Fig. 11.14. Process flow sheet of cyclohexane/benzene heat pump using hydrogen permeable membranes Rdit and R/rdehydrogenation and hydrogenation reactors C, compressors T, turbine HE, heat exchangers CHE, counter-current heat exchangers P, liquid pump M, hydrogen membranes. Reproduced from Cacciola et al. [133] with permission.

E. A, Grens, II and R, A. McKean, Temperature Maxima in Counter-current Heat Exchangers with Internal Heat Generation/ Chem. Eng. Sci., 18, 291 (1963). 

HeatX - co- and counter-current heat exchangers Hetran - shell and tube heat exchangers Aerotran - air-cooled heat exchangers... 

Modify the process in Problem 7.5 to use a counter-current heat exchanger (and trim heater) to heat the reactor feed and cool the reactor product. 

Counter Current Heat Exchangers in Plug Flow Reactors... 

Consider a counter-current heat exchanger, such as is used on many industrial plants. In essence this is a pair of pipes in close thermal contact (Fig. 5.1). If it were to be operated reversibly, the water and initially hot liquid would be in continuous equilibrium, with at each point only an infinitesimal thermal gradient between the liquids. In such a case, the liquids... 

Figure 20.2 is a schematic of a counter-current heat exchanger showing the heat flows. Neglecting heat conduction in a longitudinal direction, an energy balance on the tube wall element gives ... 

First, the TID is a temperature plot, not to scale, of all hot and cold streams to be analyzed. Two temperature scales are shown on the TID, the hot temperature scale and the cold temperature scale. A minimum temperature driving force, pre-selected by the designer, separates the hot and cold temperature scales numerically and this minimum temperature driving force is the minimum temperature difference between a hot and cold stream to be allowed on either end of a counter-current heat exchanger. Each hot and cold steam is represented on the TID as an individual arrow whose tail is the supply temperature and whose head is the target temperature. Figure 6.2 shows an example temperature-interval diagram with two hot streams and two cold streams plotted. 

Figure 10.11 Schematic of a counter-current heat exchanger.

Apart from the benefits of the high pressure mixing of SO3 with water to produce sulfuric acid, the proposed cold process for the manufacture of sulfuric acid has also been conceived to avoid the complexity of requiring a sulfur furnace and the related heat recovery system, the multipass static converter, counter current heat exchangers, the interpass absorption tower (IPAT), drying tower (DT), final absorption tower (FAT), mist eliminators, acid coolers, and alkali scrubber. The resulting plant is, as a result, of much lower cost in equipment and land use. 

Claude process A process for Uquelying air on a commercial basis. Air under pressure is used as the working substance in a piston engine, where it does external work and cools adlabatically. This cool air Is fed to a counter-current heat exchanger, where it reduces the temperature of the next intake of high-pressure air. The same air is recom-press and used again, and after several cycles eventually liquefies. The process was perfected in 1902 by the French scientist Georges Claude (1870-1960). 

The most realistic option for partial condenser modeling is the LMTD option. The cooling medium is a liquid that enters a counter-current heat exchanger at a specified inlet temperature. The minimum approach differential temperature is specified. The process inlet and outlet temperatures are known, so the log-mean temperature differential driving force is known. With the known condenser duty, the required product of the overall heat-transfer coefficient and the condenser heat-transfer area (UA) is calculated. The required flow rate of the cooling medium can also be calculated. 

Figure 3.20. Quantification of heat exchange characteristics. The set-up of measurements contains a counter-current heat exchanger with indicated values of temperatures (T at warm sides, at cool sides). The temperature profile shown (a) serves to calculate the logarithmic mean according to Equ. 3.67 in such real cases of greater linear extension. From the plot of reactor temperature versus time t (b), in analogy to Fig. 3.15b, heat evolution rate and heat transfer coefficient can be calculated as shown in the text. At time tg, the heat exchanger is stopped and at it is reactivated.

Consider a counter-current heat exchanger. The stream on the tube side has a specific heat capacity of 2.0 kJ kg K and has an inlet temperature of 100°C. The other stream enters at 35°C and has a specific heat capacity of 2.5 kJ kg K". The respective flowrates are 1.5 kg s and 0.9 kgs . Given an overall heat transfer coefficient of 800 W m K calculate the exit temperatures, and heat exchange area required, if 50 per cent, 75 per cent and 95 per cent of the maximum possible amount of heat is recovered. 

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