Thesis (Ph.D.)--Hong Kong Polytechnic University, 2008. / Adviser: Jian Lei Niu. Includes bibliographical references.

Thesis (M.Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 81-92) Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2004. / Also available in print.

Thesis (M.S.E.)--University of Wisconsin -- La Crosse, 2005. / Includes bibliographical references (leaf 56)

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed June 11, 2007). PDF text: x, 153 p. : ill. UMI publication number: AAT 3243742. Includes bibliographical references. Also available in microfilm and microfiche formats.

The initial stage of the work was a study of an 80 tonne industrial furnace, taking observations, panel water temperature data and samples of slag layers from the sidewalls. This resulted in a simple model of layer formation which explained the observed structures, and also the effect of slag layer thickness on heat losses was examined. However, the complexity and variety of structures found were such that a full series of direct thermal conductivity measurements was deemed impractical, and so a theoretical model to calculate the thermal conductivity of complex structures from the thermal conductivities of it s components was developed. Other aspects of heat transfer both within the furnace and from the furnace interior to the water cooling were also explored. In order to obtain a reliable value of thermal conductivity for the slag component of layer structures, a technique was developed to measure the thermal conductivity of the slag. This consisted of firstly determining a viable route for the production of homogenous samples, followed by the design, construction and refinement of an experimental measuring rig. After a large number of preliminary measurements, a series of thermal conductivity values at temperatures between 300 and 800 °C were measured using operating conditions calibrated against a heat storage brick sample of known thermal conductivity. These results were used to provide the data for the theoretical thermal conductivity model, which was then applied to real structures for which thermal data was available. Comparison of the results showed good correlation. Finally, in the appended case study, the heat loss calculation was applied for various furnace situations to identify the potential heat loss savings that could be achieved by controlling the slag layer thickness and structure, and the financial implications.

No description available.

This project looks at the production of electricity by the CEGB's power stations noting the vast quantities of water required for cooling purposes. The main types of cooling system and the problem of condenser scaling often associated with the use of cooling towers and the evaporative cooling process are described, together with the usual methods of scale prevention/ treatment. The Croydon B power station is entirely dependant on treated sewage effluent for cooling water. A combination of the high total dissolved solids content of sewage effluent and their concentration by evaporative cooling made condenser scaling a particular problem. A novel method was developed, whereby nitrification of ammonia in the cooling water was used to control pH and prevent scaling. The system has been in operation for some twenty years, and this project investigates the effect of the major physical and chemical factors in cooling towers on the nitrification process. Work was carried out on a laboratory scale in a 15 litre culture vessel, a 27000 litre pilot scale cooling tower rig system and in the power station itself. The site of nitrification and the effect of pH, temperature, substrate concentration, flow rates, retention time, packing area and organic loading were investigated Differences in the reactions to these factors in the different scales of experiment were found and explanations attempted. In a power station cooling system the most important factors governing nitrification were felt to be pH, flow rate and area of packing. The results of the tests were used to develop a simple model of the system which could be used as a rapid guide to the degree of nitrification posible in any cooling tower. Finally the feasibility of the use of different sources of ammonia was investigated.

The zone method for analysing radiative heat transfer has been widely applied for furnace modelling, and is extensively reported in the open literature. The main reason for the application of this method lies in the accuracy with which it solves the radiant transfer in hot enclosures. Thus, it is generally the preferred method when it is essential to predict accurately the temperature distribution in the furnace. Its application, however, has been limited in most cases by the need to over-simplify the furnace conditions. These simplifications include the need to modify the furnace shape and zoning arrangement, the load representation, and the simulation of convection. Another significant feature of most applications of the zone method is the restriction of the simulation to steady-state conditions. This Ph.D. project aims to eliminate some of these constraints and, therefore, improve application of the zone method to furnaces. Hence, full transient conditions were simulated for different zone models, which varied in complexity from a single gas zone model to a full 3D multi-zone version. The exchange factors required in the zone method were calculated by a Monte-Carlo method using RADEX, a suitable computer code which enabled the furnace geometry to be accurately represented as well as the load, which could be simulated by a series of individual components instead of a single big slab covering the entire hearth surface area. Two different furnaces were modelled, namely a steel reheating furnace and a heat treatment furnace. Experimental data from production were used to validate the heat treatment system mathematical model. Parametric studies were then performed for both furnaces. The predictions clearly demonstrate the need for multi-zone transient models since the load temperature-history was significantly different from that predicted by a simpler long-furnace model. Another aim of the project was to produce reliable data concerning the convective heat transfer in furnaces. This parameter is often ignored in furnace modelling, or if included has been restricted to a crude single empirical value (usually 5 - 10 W/m2K). This can produce erroneous results in applications where the flame and combustion products temperatures are low, as in heat treatment furnaces. In these cases convection may play a more important role than is currently assumed. A mass transfer technique was employed in order to determine heat transfer coefficients for the heat treatment furnace for a variety of load arrangements and firing conditions. These coefficients which were significantly higher (25 - 45 W/m2K) than the usually assumed crude values were subsequently used in the mathematical models of the furnace performance.

This thesis is concerned with an experimental and theoretical investigation of domestic heat pumps. The development of heat pumps in the 1970's did not meet the original expectations and this thesis examines the reasons why. The items considered included cycling and unsteady conditions created whilst matching the heat pump's output to meet a space heating load. A detailed study was made of the hermetically sealed refrigerant compressor, the heat exchangers, and the refrigerant pressure and temperature control systems. In addition to the conventional heat pump a study was made of the advantages gained from modular designed heat pumps. The application of heat pumps to U.K. dwellings and climatic conditions was studied together with the suitability of thermostatic control. Initial studies were made of the operation of a demonstration unit. This showed how intermittent operation would reduce a heat pump performance and was followed by the development of a computer model which simulated the complete refrigerant circulation system. This allowed a study to be made of a heat pump performance at part load conditions. A computer model of the complete refrigerant cycle was developed which aided in the design and construction of a heat pump which used refrigerant R12. This was followed by the construction of a second test rig using R 134(a). The completed R 134(a) test rig was installed in an environmental chamber which could simulate outdoor weather conditions. Results from the test rigs indicated that the performance was greatly affected by on/off cycling an item that was further investigated.