Browsing by Subject "Heat exchangers"
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Item Analysis and optimization of heat integrated distillation sequences(Texas Tech University, 1985-05) Shankar, HariharanThis work proposes a heuristic-evolutionary method to optimize heat-integrated distillation sequences. The key to this method is the use of a quantitative measure which evaluates the Overall Difficulty of Separation for a separation problem (ODOS). ODOS is defined as ODOS=(Q/dt)/F where Q is the condenser duty in the column, dt is the temperature difference between the condenser and reboiler and F is a factor, proposed by Nadgir and Liu (1983), which reflects the balance between the top and bottom products. F is defined as F = Min (V/L, L/V) where V and L are respectively the amounts of the top and bottom products. The ODOS, developed in this work, not only enabled selection of a good upper bound for the cost of the 'optimal' sequence, but allowed prediction of a band of 'good' sequences for the problems considered in this work. This quantitative measure was also successful in eliminating the non-competitive sequences from further consideration. The selection of a band of sequences enables the designer to choose the sequence for actual implementation from objectives other than economics, like ease of control, plant layout, etc. The method involves no intermediate evaluation of the candidate sequences, unlike traditional evolutionary methods. This work has also confirmed the decomposition principle of Sophos et al (1981, 1982), which stated that the separation sequencing problem should be tackled first and then heat integration should be attempted for the 'good' sequences identified. This method was tested by calculating the costs for each sequence with and without integration for seven of the nine examples considered in this work. For the other two examples, as well as for the first seven examples, values reported in the literature were used to assess this method. This method has also been compared with the standard heuristic methods in the literature. This method compares very favorably with the literature methods in terms of locating a good initial sequence, identifying competitive sequences, eliminating non-competitive sequences and providing a quantitative measure for the competitiveness of a sequence.Item Design and control of a heat-integrated distillation train(Texas Tech University, 1985-08) Bryan, Kent ENot availableItem Experimental comparison of advanced control strategies(Texas Tech University, 1995-08) Joshi, Ninad V.The objective of this research endeavor is to compare experimentally several advanced control strategies on a heat exchanger and fluid flow system. The experimental set-up was established a few years back and consists of a shell-and-tube heat exchanger with several control valves. This heat exchanger uses steam or hot water on its shell side to heat either cold or hot or a mixture of hot and cold water passing through its tube side to a desired temperature. The apparatus also contains many pneumatic control valves for controlling the flow rates of hot or cold water or steam. An experimental comparison of three control strategies (classical PID, internal model control [IMC], and process modelbased control [PMBC]) was done a couple of years earlier. The objective of this study, along with the previous one, was to implement some advanced control strategies, and present a broad-based overall perspective on the advantages and disadvantages of different control strategies. This study picks up where the last study left off, and implemented some more control strategies under similar experimental conditions. The different advanced control strategies ultimately to be implemented were neural network-based control (both inverse and normal model), model predictive control, a combination of model predictive control and neural network-based control, and heuristic-based fuzzy logic control. Thus, as a part of this study, eight different strategies were implemented. Studies on the fuzzy logic strategy were carried out separately by another graduate student.