Heat exchanger designs for

A numerical study of the effect of area ratio on the flow distribution in parallel flow manifolds used in a Hquid cooling module for electronic packaging demonstrate the useflilness of such a computational fluid dynamic code. The manifolds have rectangular headers and channels divided with thin baffles, as shown in Figure 12. Because the flow is laminar in small heat exchangers designed for electronic packaging or biochemical process, the inlet Reynolds numbers of 5, 50, and 250 were used for three different area ratio cases, ie, AR = 4, 8, and 16. 

There are two basic approaches to heat-exchanger design for low temperatures (1) the effec tiveness-NTU approach and (2) the log-mean-temperature-difference (LMTD) approach. The LMTD approach is used most frequently when all the required mass flows are known and the area of the exchanger is to be determined. The effec-... 

For reformate flow rates up to 400 Ndm3 min-1, the CO output was determined as < 12 ppm for simulated methanol. The reactors were operated at full load (20 kW equivalent power output) for -100 h without deactivation. In connection with the 20 kW methanol reformer, the CO output of the two final reactors was < 10 ppm for more than 2 h at a feed concentration of 1.6% carbon monoxide. Because the reformer was realized as a combination of steam reformer and catalytic burner in the plate and fin design as well, this may be regarded as an impressive demonstration of the capabilities of the integrated heat exchanger design for fuel processors in the kilowatt range. 

TUBE-SIDE POWER COST IMMATERIAL. Optimization of the heat-exchanger design for this situation is based on the assumption that C, is zero and ht is constant. The procedure is similar to that for the case of shell-side power immaterial as described in the preceding paragraph. The optimum value of h0 can be determined from the following equation, which is obtained by setting the partial derivatives of Eq. (44) with respect to hQ and with respect to A, equal to zero ... 

The inside diameter of the shell is used as the reference dimension for heat exchanger design. For example, the unit shown in Figure 2-4 has a shell with an outside diameter of 20 inches and an inside iameter of 19-1/4 inches. These are the dimen-sons of 20-inch, Schedule 20 pipe, which is .eaper and easier to use than flat steel plate which wDuld have to be rolled into a cylinder and welded together to form the shell. 

Figure 14.19 (a) Integrated water-gas shift reactor/heat exchanger designed for 5kW fuel cell system, (b) internal temperature profiles determined during operation of this reactor the different profiles correspond to different load (100% load is the 5 kW equivalent). The values shown for 100% load were determined at the fresh reactor (0 h) after 24 h under operation (24 h) and after an accidental exposure to reformate of too low temperature for the... 

Because the reformer was a combination of steam reformer and catalytic burner in plate and fin design, this was regarded as an early and impressive demonstration of the capabilities of the integrated heat exchanger design for fuel processors in the kilowatt range. 

Figure 7.31 Integrated water-gas shift reactor/heat-exchanger designed for a 2-kW fuel cell system [312],...

For traditional cascaded plants, consisting mainly of process units connected in series, the controllability properties can easily be deduced from consideration of the individual units. The disturbance sensitivity is simply a product of the disturbance sensitivities of the units cormecting the disturbance and output under consideration, and any fundamental control limitation can be attributed to some individual unit. Since there exist a wealth of knowledge on how to improve the disturbance sensitivity, and avoid control limitations, through design of common units like reactors, distillation columns and heat-exchangers, design for controllability is fully feasible for cascaded plants. 

Determine the bare module cost of a 1-shell pass, 2-tube pass (1-2) heat exchanger designed for the following operating conditions ... 

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