Heat Exchanger Optimization

Design specifications for one case of heat exchanger optimization... 

Jenssen, S.K. "Heat Exchanger Optimization." Chemical Engr. Progress, v.65, no.7, pp.59-66 July 1969. 

Adsorption systems are used to remove water and carbon dioxide from feed air. Two or more adsorption beds are used in a swing arrangement to accomplish the required purification. An energy requirement of 5-7% of the air compressor power is expended in the operation of an adsorptive purification system. But heat exchanger optimization and cold box simplification can be achieved with this type of system and regeneration heat can be recovered and air losses completely eliminated. The energy penalty is overcome by the advantages of an adsorption system and, as a result, most modern air separation plants use adsorptive purification for the feed air. 

Use pre-flash, feed conditioning, feed-product heat exchange, heat pumps, dividing-wall columns (Premkumar and Rangaiah, 2009), intermediate heat exchangers, optimize pump around flows. Organic Rankine Cycle (ORC) and Kalina Cycle (KC) to recover power (Chew et al., 2014)... 

The design of the heat exchanger network is greatly simplified if the design is initialized with an optimized value for... 

Increasing the chosen value of process energy consumption also increases all temperature differences available for heat recovery and hence decreases the necessary heat exchanger surface area (see Fig. 6.6). The network area can be distributed over the targeted number of units or shells to obtain a capital cost using Eq. (7.21). This capital cost can be annualized as detailed in App. A. The annualized capital cost can be traded off against the annual utility cost as shown in Fig. 6.6. The total cost shows a minimum at the optimal energy consumption. 

The overall inventory. In the preceding chapter, the optimization of reactor conversion was considered. As the conversion increased, the size (and cost) of the reactor increased, but that of separation, recycle, and heat exchanger network systems decreased. The same also tends to occur with the inventory of material in these systems. The inventory in the reactor increases with increasing conversion, but the inventory in the other systems decreases. Thus, in some processes, it is possible to optimize for minimum overall inventory. In the same way as reactor conversion can be varied to minimize the overall inventory, the recycle inert concentration also can be varied. 

Heat Exchanger Network Design Based on the Optimization of a Reducible Structure... 

The approach to heat exchanger network design discussed so far is based on the creation of an irreducible structure. No redundant features were included. Of course, when the network is optimized, some of the features might be removed by the optimization. The scope for the optimization to remove features results from the assumptions made during the creation of the initial structure. However, no attempt was made to deliberately include redundant features. 

Yee, T. F., and Grossmann, I. E., A Simultaneous Optimization Approach for the Synthesis of Heat Exchanger Networks, Paper 81d, Annual AIChE Meeting, Washington, 1988. 

Eurther research on convective transport under low Reynolds number, quasicontinuum conditions is needed before the optimal design of such a micro heat exchanger is possible. The cooling heat exchanger is usually thermally linked to a relatively massive substrate. The effects of this linkage need to be explored and accurate methods of predicting the heat-transfer and pressure-drop performance need to be developed. 

Combinatorial. Combinatorial methods express the synthesis problem as a traditional optimization problem which can only be solved using powerful techniques that have been known for some time. These may use total network cost direcdy as an objective function but do not exploit the special characteristics of heat-exchange networks in obtaining a solution. Much of the early work in heat-exchange network synthesis was based on exhaustive search or combinatorial development of networks. This work has not proven useful because for only a typical ten-process-stream example problem the alternative sets of feasible matches are cal.55 x 10 without stream spHtting. 

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