Countercurrent heat exchangers

For a simple J-T liquefier, the liquefied portion is continuously withdrawn from the resei voir and only the unliquefied portion of the fluid is warmed in the countercurrent heat exchanger and returned to the compressor. The fraction y that is hquefied is obtained by applying the first law to the heat exchanger, J-T valve, and hquid resei voir. This results in... 

In a counterflow or countercurrent heat exchanger, hot and cold fluids enter the exchanger from opposite sides. The counterflow heat exchanger in Fig. 9.5 serves as a reference for all other heat exchanger configurations. A detailed analysis of this type of heat exchanger is therefore necessary. 

For a countercurrent heat exchanger, the logarithmic temperature difference is then... 

The batch system of heating is to be replaced by a continuous countercurrent heat exchanger in which the heating medium is a liquid entering at 388 K and leaving at 333 K. If the heat transfer coefficient is 250 W/m2 K, what heat exchange area is required Neglect heat losses. 

Techniques for approaching optimum temperature profiles for exothermic reaction, (a) Adiabatic operation of reactors with interstage cooling, (b) Countercurrent heat exchange. (Adapted from Chemical Reaction Engineering, Second Edition, by O. Levenspiel. Copyright 1972. Reprinted by permission of John Wiley and Sons, Inc.)... 

Emmitle 4.2. A countercurrent heat exchanger is an important example of a system described by equations that are usually solved iteratively. Figure 4.4 shows the system. The problem is to And the steadystate outlet temperatures of the oil, T , and cooling water,, and the heat transfer rate Q, given the inlet temperatures, flow rates, and heat transfer coefficient and area. The steadystate equations for heat transfer are... 

As crystals of ice are formed, they are perfectly separated from the residual brine and passed to a melting tank, being raised to the melting temperature, Toi en route by the previously mentioned countercurrent heat exchange with the incoming saline water. 

When a patient coming out of anesthesia gets the chills, what do you do Put a warm blanket on them, of course. The energy in the warm blanket transfers energy to the patient, at least partially through conduction. Countercurrent heat exchange between veins and arteries is an important temperature regulation mechanism in the human body, which also relies on conduction. 

A value of lossnorm = 1 indicates that the total heat loss via the exit streams of the exothermic and the endothermic stage is equal to the amount of heat required to heat up the feed of the endothermic stage about AT = Tequ-To. lossmrm can be expressed explicitly as a function of h and NTUenio taking into account the theory of ideal countercurrent heat exchangers [7]. 

Under autothermal operation the hot effluent of a fixed-bed reactor is used to heat up the cold feed to the ignition temperature of the catalytic reaction. Since no other addition or removal of heat takes place, autothermal operation is restricted to reaction systems which all together are exothermic. The conventional reactor design consists of an adiabatic packed-bed reactor coupled with a countercurrent heat exchanger (Fig. 23A). 

Figure 25. Equivalence of operation with periodical flow re versa and countercurrent heat exchange A) Fixed-bed reactor with periodic flow reversal, B) Temperature profiles with rapid flow reversal, C) Countercurrent reactor with catalyst at the wall D) Schematic concentration and temperature profiles m both reactors [141...

Reaction products leave the reactor and are cooled in two countercurrent heat exchangers with water. Effluent is then depressurized to atmospheric pressure. Samples are collected for the analysis. 

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