Double-pipe countercurrent

The time required to heat the agitated batch using the double pipe countercurrent flow exchanger. 

In a typical heat exchanger a hot fluid inside a pipe is cooled from T toTj by a cold fluid which is flowing on the outside in a double pipe countercurrently (in the reverse direction) and is heated from Tj to Z tts shown in Fig. 4.5-3a. The AT shown is varying with distance. Hence, AT in Eq. (4.5-17) varies as the area A goes from 0 at the inlet to A at the outlet of the exchanger. 

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

A. Zavala-Rio, R. Femat, and G. Solis-Perales. Countercurrent double-pipe heat exchangers are a special type of positive systems. In First Multidisciplinary International Symposium on Positive Systems Theory and Applications (POSTA 2003), volume IEEE LNCIS 294, pages 385-392, Roma, Italy, August 2003. 

Temperature crosses that require multishell shell-and-tube units can be avoided by the inherent true countercurrent flow in double pipes. 

Fig. 1.19 Fluid temperatures t) ] and do in a double-pipe heat exchanger, a countercurrent flow, b cocurrent flow...

A heavy hydrocarbon oil with heat capacity, Cp = 0.55 Btu/(lb °F), is being cooled in a countercurrent double-pipe heat exchanger from Tj = 210°F to T2 = 170°F. The oil flows inside a tube at the rate of 8000 Ib/h and the inside tube surface temperature is maintained at 60°F. The overall heat-transfer coefficient,... 

The cooling section, Fig. 6, is of double pipe construction. Cooling water and sterile media pass countercurrently. The back pressure control valve (for sterilization) is located at the low point of the piping. A Masoneilon Camflex valve is a suitable design for this service. A steam bleed should be located on each side of this valve in order to sterilize the sterilizer forward from the steam injector and backward from the fermenter. 

FIGURE 6.24 Basic double-pipe heat exchanger, with arrows showing countercurrent flow. 

In many systems, energy is exchanged between recycle streams such as the streams and B2 shown in Fig. 7-3. Consider the case where energy is transferred from stream B2 to Bx in a double-pipe heat exchanger with countercurrent flow. 

Aniline is to be cooled from 200 to 150°F in a double-pipe heat exchanger having a total outside area of 70 ft. For cooling, a stream of toluene amounting to 8600 Ib/h at a temperature of 100 F is available. The exchanger consists of l in. Schedule 40 pipe in 2-in. Schedule 40 pipe. The aniline flow rate is 10,000 Ib/h. (a) If flow is countercurrent, what are the toluene outlet temperature, the LMTD, and the overall heat-transfer coefficient (A) What arc they if flow is parallel ... 

A flow of 1 kg/s of an organic liquid of heat capacity 2.0 kJ/kgK is cooled from 350 to 330 K by a stream of water flowing countercurrently through a double-pipe heat exchanger. Estimate the effectiveness of the unit if the water enters the exchanger at 290 K and leaves at 320 K. 

Cocurrent or countercurrent cooling fluids in the annular region of a concentric double-pipe configuration... 

Reactant A is converted irreversibly and exothermically to products in a 2-in.-inner-diameter tubular reactor via first-order chemical kinetics. The reactive mixture in the inner pipe is cooled using a concentric double-pipe heat exchanger. The nonreactive cooling fluid in the annular region flows countercurrently with respect to the reactive fluid. The radius ratio of the double-pipe configuration is If = Rinside/ outside = 0.5, the inlet temperature of the reactive fluid is 340 K,... 

TABLE 4-7 System of Equations That Must Be Analyzed to Prevent Thermal Runaway in a Plug-Flow Tiibular Reactor with Countercurrent Cooling in a Concentric Double-Pipe Configuration That Is Not Insulated from the Surroundings"... 

Figure 4-12 Correlation between the inlet and outlet temperatures of a countercurrent cooling fluid and the maximum conversion for an exothermic reactive fluid in a concentric double-pipe configuration with radius ratio k = 0.5 that is not insulated from the surroundings. The exothermic reactive fluid enters at 340 K. Two different steady-state solutions exist when the inlet temperature of the cooling fluid is between 308 K and 324 K.

Figure 4-14 Examples of two different steady-state solutions for the reactive and cooling fluid temperature profiles in a countercurrent concentric double-pipe configuration with exothermic chemical reaction in the inner tube. In both cases, the inlet temperatures of the reactive and cooling fluids are 340 K and 322 K, respectively, (a) Thamally well-behaved reactor with 18% outlet conversion of reactants to products, (b) Thamally well-behaved reactor with 49% outlet conversion of reactants to products.

Figure 4.5-3. Temperature profiles for one-pass double-pipe heat exchangers (a) countercurrent flow (b) cocurrent or parallel flow.

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