A new tvpe ot macnetic retricerator usine a rotatine belt eeometrv has been desiened and developed. The retricerator u.e. the maenetocaloric ettect. that is. the heat inc or cooline ot a maenetic material on application or removal ot a maen.tic tield. to execute a Carnot cvcle. An antiterromaanetic material. Gadolinium Gallium Garnet, Gd3Gas012 (GGG) , i. used ae the retricerant. This is in the torm ot a belt which run. throuch the bore ot a .uperconduct1na solenoid macnet to execute the cyole. The retricerator has been developed in three staces, Fir.tlv the belt ceometry was de.icned. oonstructed and te.ted. This lead to the development ot the model one retricerator. and ba.ed on the.e results the model two retriaerator was con.tructed. Re.ult •• trom the model two retricerator. show an anomalous temperature increa.e in the .ource recion resul tine trom a re - lIlaenetieation ot the belt. Purthermore. entrained tluid ettects limit the operatinc temperature span. However. the belt concept has been .ucce.etullv realised with it beina operated at trequencie. ot up to 30 rpm in macnetic tields not exceedine "T.

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Pig production in Malawi and in most of the developing countries is shifting increasingly from pasture or dirt lot to total confinement with improved housing facilities. Keeping pig level temperatures within the comfort zone in hot weather is a common problem in naturally ventilated intensive pig buildings. Automatically controlled natural ventilation (ACNV) has proved to be effective in reducing the problem of heat build up in pig houses and is becoming very popular. However, a method for reducing summer temperatures at animal level in non-automated naturally ventilated intensive pig buildings has not been developed. An attempt was made to develop a natural ventilation system which would maximise the cooling effect of wind at animal level by manual control in buildings suitable for the Tropics. The research project was conducted in three stages: (1) air flow pattern studies, using 1:20 scale two-dimensional models, (2) wind tunnel testing, using three-dimensional, 1:20 scale models with simulated pigs, and (3) validation of results from the wind tunnel studies made with a 1:4 scale model, put out in the field. Air deflectors were used as a means of increasing the effect of wind on the ventilation pattern in the models. Monopitch, duopitch and offest gable models were tested in the water table, and monopitch models were tested in the wind tunnel. The use of air deflectors in monopitch and offset gable models showed a marked increase in airflow towards the animal zone area and a reduction in the difference between the surface temperature of the model pigs and the outside air temperatures. The deflectors improved the performance of the models by about 10% with the front orientation and about 20% with the rear orientation. In the duopitch model an increase in the roof overhang improved flow circulation on the leeward side. The use of air deflectors also improved flow circulation on the leeward side. The wind speed and air temperature at the experimental site for the 1:4 scale model were used to validate the results from the wind tunnel tests. The measured temperature values showed similar response curves to the predicted values. Temperature differentials increased with an increase in the angle of the deflector.

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This thesis describes a theoretical and experimental investigation of the ejector re-compression lithium bromide absorption refrigeration cycle. In this novel cycle, a steam ejector is used to enhance the concentration process by compressing the vapour to a state that it can be used to re-heat the solution from where it was evolved. Since this cycle recovers the heat otherwise wasted in a conventional absorption cycle, the energy performance of the cycle is improved. The theoretical study shows that the improvement of the efficiency is proportional to the performance of the steam ejector. A COP of 1.013 was achieved from the experiment in this investigation. The novel cycle does not only improve the energy efficiency but also avoids the corrosion that will happen when high temperature heat sources are used to drive a lithium bromide absorption refrigerator. The steam ejector in the novel cycle acts as an efficient temperature converter in acceptance of different temperature heat sources, which reduces the energy loss when the temperature difference between the solution and the heat source is big. Therefore, the solution temperature can be set to a low level while the heat source temperature is high. This is significant to avoid the corrosion of lithium bromide solution at high temperature. Furthermore, the construction of the machine based on the novel cycle is simpler than that based on the conventional double-effect cycle. This refrigerator will be more reliable and have a lower initial capital cost. The cycle was investigated comprehensively in this thesis. In the theoretical study, a mathematical model for this novel cycle was established. The theoretical study reveals the operation characteristics and the factors that affect the energy efficiency of the cycle as well as how to design a refrigerator based on the novel cycle. In the experimental study, a concept-approved refrigerator was manufactured and tested. The part-load performance of the novel cycle was investigated from the experiment. The theoretical results had a good agreement with the experimental ones. NB. This ethesis has been created by scanning the typescript original and contains some inaccuracies. In case of difficulty, please refer to the original text.

Buildings expend vast quantities of energy, which has a detrimental impact on the environment. Buildings systems are often oversized to cope with possible extreme environmental conditions. Building simulation provides an opportunity to improve building thermal design, but the available tools are typically used in combination in order to overcome their individual deficiencies. Two such tools, often used in tandem are computational fluid dynamics (CFD) and dynamic thermal modelling (DTM). DTM provides a coarse analysis, by considering external and internal thermal conditions over a building (including its fabric) over time. CFD is usually used to provide steady state analysis. Boundary conditions typically in the form of surface temperatures are manually input from DTM into CFD. CFD can model buildings dynamically, but is not commonly used, since solving for hugely different time constants of solid and air pose significant limitations, due to data generated and time consumed. A technique is developed in this study to tackle these limitations. There are two main strands to the research. DTM techniques had to be incorporated into CFD, starting from first principles of modelling heat transfer through solid materials. These were developed into employing the use of functions such as the 'freeze flow' function (FEF) and the 'boundary freeze' function (BFF) in combination with a time-varying grid schedule to model solids and air simultaneously. The FFF pauses the solution of all governing equations of fluid flow, except temperature. The BFF can be applied to solid boundaries to lock their temperatures whilst all other equations are solved. After extensive research the established DTM-CFD Procedure eventually used the FEF and BFF with transient periods and steady state updates, respectively. The second strand of research involved the application of the DTM-CFD Procedure to a typical office space over a period of 24-hours. Through inter-model comparisons with a fully transient simulation, the DTM-CFD Procedure proved to be capable of providing dynamic thermal simulations 16.4% more efficiently than a typical CFD code and more accurately than a typical DTM code. Additional research is recommended for the further improvement of the DTM-CFD Procedure.

The study presented here is focused on the use of aqua-ammonia solution in a novel solar-powered refrigeration cycle intended to be suitable for use in the rural areas of developing countries. The cycle is referred to as a `intermittent regenerative' (IR) cycle, the term regenerative meaning in this context the use of heat recovery or recuperation. The first chapter describes the three better known cycles which may be considered for this application. The IR cycle is introduced as a hybrid development of these which offers the significant advantages of high efficiency while minimising complexity. Chapter 1 provides a methodology by which the novel aqua-ammonia system can be evaluated in comparison with existing systems. The second chapter surveys previous experimental work on solar driven aqua-ammonia cycles. Chapter 3 consists of a detailed design study of the new IR cycle based on computer modelling techniques. The study serves as an analysis of the cycle and allows the performance of the cycle, together with design features and component sizes, to be simulated in a variety of meteorological conditions. A number of original design proposals are evaluated through the modelling exercise. Chapter 4 summarises the results of a second separate modelling exercise which investigates the absorption phase of the cycle. Chapters 5 and 6 describe experimental work. The results of laboratory tests are compared with the predictions of the computer model and in the event serve to validate the theoretical characterisation made in chapter 3 of the performance of key components of the system. The energy efficiency of the system as measured by experiment is proved to correspond to theoretical prediction, so representing a significant advance on the performance of alternative systems. Chapter 7 addresses itself to the wider question of the social and economic validity of a device with the performance and cost of the IR device. A case study is undertaken which explores the potential role of the device in the fish trading economy of Zambia. The study provides data valuable in assessing the usefulness of the technology in helping to stimulate the under-capitalised rural economy of a developing country and in improving local food resource utilisation. Chapter 8 draws together the conclusions of the various chapters and provides an overall conclusion and comment on the value of the IR system. It is proved to have a high efficiency but not to have the robustness nor portability demanded for widespread application in remote locations. Nevertheless the likely life-time cost-effectiveness of the system is judged to be an improvement on existing alternatives and suggestions are made for further improvement.

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