Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains viii, 67 p. : ill. Includes abstract. Includes bibliographical references (p. 53).

Thesis--M. Phil., University of Hong Kong, 1976.

The results of an insitu investigation into the thermal performance of a range of wall constructions are presented. The investigations were mainly undertaken to establish the uncertainty introduced by the measurement, the variability in the performance of the wall due to factors such as workmanship and the relevance of design values in practice. This study provides a useful addition to the otherwise sparse literature of actual measured heat flow and temperature data available from large scale field surveys in UK. A review of methods and equipment used to recover the thermal transmittance value of wall constructions is presented. The Heat Flow Sensor measurement method was found to be most suitable for the needs of the study and was evaluated both theoretically and experimentally. An experimental design approach was devised which enabled the separation of the variability involved in the measurement process and the variability involved in the performance of the wall to be obtained. The four generic wall types sampled included a representative range of existing and new build constructions. The indications are that the wall constructions investigated broadly perform as expected. However, for certain wall types there were significant differences between measured and standard design calculation values. This was because the appropriate theoretical model was not applied in order to establish the transmittance of the wall construction at the design stage. It would appear that the overall error in the measurement process, which is a combination of both the systematic and the random error, was typically of the order of +/-11%, whereas the variability in the wall performance was seen to vary as a function of the wall type with the resulting values ranging between 4% and 39.5%. The differences in the observed performance of the wall may be potentially attributed to 4 major causes, namely: (a) dimensional tolerances and material properties, (b) changes in material properties, (c) the wall as part of the construction and (d) workmanship. The average wall performance in some circumstances can be estimated satisfactorily by using a one dimensional model where a relatively homogeneous wall construction is assumed. While the area weighted one dimensional model gives a reasonable estimate of the average wall performance by taking into account the cold bridging of the mortar joints, a more complete understanding of the wall performance can only be achieved by the use of a three dimensional model.

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Design for process flexibility is an industrially important topic so it is not surprising that it is attracting much research work. Given the size of the problem it is also not surprising that workers have concentrated on heat exchanger networks, which can be considered to be a self-contained sub-problem. Unfortunately, recent research has suffered from a number of major drawbacks. Problem formulation has often been unrealistic. Proposed procedures tend to be 'clinical' rather than practical. Academic research has often been conducted without proper consideration of the industrial environment. Very few research results have been tested on full scale industrial problems. In this thesis a new problem formulation and new solution techniques are presented. They have been designed to fulfil the needs of industry. In problem formulation it is recognised that the specification of flexibility is primarily an economic problem. The amount of flexibility industry will demand is a function of how much it costs. The methodology developed here allows both, the flexibility cost and the existing trade-off between flexibility needs, capital costs and energy costs to be fully evaluated. Flexibility problem formulation is mainly based on Multiple Base Cases. Different plant operating scenarios are set and a design found that is able to satisfy each case. This is a formulation that has found a wide acceptance in industry. To be industrially practical, process design techniques must be intelligible to the non-specialist. The techniques developed here are simple and straightforward and give insight. Two new design techniques have been developed. The first of these is 'Downstream Paths'. These are used to identify and evolve the network structures that permit cost effective flexibility. The second technique is 'Sensitivity Tables'. These can be used to analyse the performance of a given structure. In addition they determine the cost effective modification to elements of the structure which provide the specified flexibility needs. The technique is rapid, simple to apply and easy to repeat. Consequently, many scenarios can be screened without much effort and a cost profile developed in order to evaluate the cost trade-off described above. The approach proposed in this thesis, involving the new problem formulation and solution techniques, has been applied to a number of case studies of industrial scale. These case studies have covered problems as diverse as catalyst deactivation, fouling, and plant debottlenecking. One major spin-off from the work is a new approach to the design of heat exchanger networks subjected to fouling. Large potential savings have been identified.

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