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Natural ventilation is a passive cooling method that has significant potential to reduce building energy consumption and to positively contribute to indoor environmental conditions. Because the window is an important element in naturally ventilated buildings, it can be used to adjust indoor air flow. However, lack of knowledge about occupants‘ window control behaviour and how this relates to different window typology would result in discrepancy between actual and proposed building performance. And also, limit the potential of natural ventilation in the building. This thesis explores the relationship between indoor air velocity, occupants‘ window control behaviour and window design. This study is based on field measurement and occupant comfort survey in four office buildings in a hot and humid climate in South-east China. The field study was carried in September and October of 2012. The indoor and outdoor thermal conditions, indoor air flow speed, window state and effective opening area were monitored. Occupant thermal comfort questionnaires were given to participants four times a day to record their comfort perceptions in the office. The field study gives new insights into the correlation between indoor air speed, occupants‘ window control behaviour and window design. For the research 14400 set of indoor and outdoor temperature and relative humidity data, 174560 indoor air velocity records and 1344 copies of questionnaires were collected. The results of this study defined comfort zone for this climate which is consistent with Givoni‘s comfort zone for a hot and humid climate. The indoor air flow path is identified by measuring the indoor air velocity across different parts of the office and related window opening combinations. Besides, the effective opening area is reduced with decreased indoor air temperature when the indoor air temperature is lower than 25°c. None of the windows is closed when the indoor air temperature is higher than 28°c. During the working hours, the changing of effective opening is related to the air velocity across the desk surface. And measured maximum indoor air velocity measured around the occupant is 1.8m/s which did not result in occupants‘ window changing behaviour to adjust for comfort. In conclusion, this study proved that occupants who live in hot and humid climate can accept higher humidity level. If the air velocity can be avoided across the occupant‘s working surface, then a higher indoor air velocity is still accepted by occupant as within their comfort threshold. So, there are great potentials for occupant to extend their comfort threshold and adapt to the local climate. Besides, window opening type and position has a significant impact on indoor air velocity and pattern. It would also influence convective cooling affect and occupant thermal comfort. This is evident from the indoor air velocity measurement results and the occupant comfort survey results. In addition, accessibility is important to window design. In the naturally ventilated office building, if occupants find it difficult to operate the window, this will have an influence on the natural ventilation potential in the building and cause the occupant discomfort. Thus, the findings of this study will help architects and engineers to design naturally ventilated office buildings in South-east China.

Energy consumption by human enhanced activities has led to distinctive environmental problems; in particular, climate change and global warming. In hot regions, the main reason for energy consumption comes from the cooling of many buildings. The intensity and duration of the sunshine in hot regions have a direct relation with the usage of cooling systems. The energy used for cooling purpose is continuously increasing and expected to increase in the following years. Evaporative cooling is one of the passive cooling method which has been used throughout history. As it is cheaper, environmentally-friendly and simpler compared to vapour compression systems, it is more widely used in residential, commercial and industrial buildings in hot and dry regions. Since this method is less efficient and limited under hot and humid climate, the desiccant based evaporative cooling system is preferred in such areas in order to dehumidify the air. The pad material used for evaporative cooling system is important as it helps to evaporate the water. Therefore, the material should be porous enough to absorb water which enhances the rate of evaporation. Moreover, the material should be available and cheap. This study shows the potential of using different materials for evaporative cooling systems. The aim of this study is to investigate the feasibility, suitability and potential of using local materials such as eucalyptus fibres, as cooling pads for evaporative cooling system in hot and dry regions. In addition to this, the liquid desiccant evaporative cooling systems by using potassium formate is also studied for hot and humid areas in Cyprus. Since Cyprus has multi-climate regions due to the topography and different weather condition, different cooling systems can be used for each region. The results are reported in terms of temperature difference, cooling output, COP, etc. The wind tunnel is used to test the eucalyptus fibres with an inlet air temperature of 35 °C to simulate the climate in Cyprus. It was found that the maximum reduction of air temperature was between 11.3 °C and 6.6 °C, while the maximum cooling efficiency was in the range of 71% and 49% at 0.1 and 0.6 m/s air velocity respectively. Corresponding cooling capacities were also calculated as 108 and 409 W indicating a directly proportional relation between air velocities and cooling performance. Following this, the conceptual design ideas of integrated eucalyptus fibres based evaporative cooling panel (EFECP) into building elements are considered to meet the demand for cooling and the architectural requirements of the building. These design ideas were developed for shutter, fenestration, toplighting elements, wind catcher-solar chimney and wall design of the building. The cooling performances of the hollow fibre integrated by using potassium formate desiccant based evaporative cooling system were experimentally investigated under the incoming air temperature in the range of 35 ˚C to 40 ˚C. The cooling capacity is increased as the air velocity is increased. At 3.5m/s, the cooling capacity is 1340 W, 1530 W and 1920 W respectively for incoming air relative humidity of 60%, 65% and 70%. Both evaporative cooling systems performances are discussed and clearly presented in this study. From the experimental testing in this thesis, it is concluded that local eucalyptus fibres can be used for hot-dry areas and liquid desiccant evaporative cooling systems can be used for hot-humid areas of Cyprus. Since using of eucalyptus fibres for evaporative cooling system is locally available, simple construction and easy to apply, the design ideas for integrating eucalyptus fibres with evaporative cooling system are developed within the scope of the thesis. The usage of local eucalyptus fibres and Polyvinylidene fluoride (PVDF) hollow fibres as evaporative cooling pad, the evaporative cooling process designed by using fibres and the conceptual building design ideas integrated local eucalyptus fibres combined with evaporative cooling system are all the novel ideas of this thesis.

In this thesis, heat powered ejector cooling systems was investigated in two ways: to store the cold energy with energy storage system and to utilize low grade energy to provide both electricity and cooling effect. A basic ejector prototype was constructed and tested in the laboratory. Water was selected as the working fluid due to its suitable physical properties, environmental friendly and economically available features. The computer simulations based on a 1-0 ejector model was carried out to investigate the effects of various working conditions on the ejector performance. The coefficients of performance from experimental results were above 0.25 for generator temperature of lI5°C-130 °C, showing good agreements with theoretical analysis. Experimental investigations on the operating characteristics of PCM cold storage system integrated with ejector cooling system were conducted. The experimental results demonstrated that the PCM cold storage combined with ejector cooling system was practically applicable. The effectiveness-NTU method was applied for characterizing the tube-in-container PCM storage system. The correlation of effectiveness as the function of mass flow rate was derived from experimental data, and was used as a design parameter for the PCM cold storage system. In order to explore the possibility of providing cooling effect and electricity simultaneously, various configurations of combined power and ejector cooling system were studied experimentally and theoretically. The thermal performance of the combined system in the range of 0.15-0.25 and the turbine output between 1200W -1400W were obtained under various heat source temperatures, turbine expansion ratios and condenser temperatures. Such combined system was further simulated with solar energy as driving force under Shanghai climates, achieving a predicted maximum thermal efficiency of 0.2. By using the methods of Life Saving Analysis, the optimized solar collector area was 30m2 and 90m2 respectively for the system without and with power generation. The environmental impacts and the carbon reductions of these two systems were discussed.

The trend towards improving building airtightness to save energy has increased the incidence of poor indoor air quality and associated problems, such as condensation on windows, mould, rot and fungus on window frames. Mechanical ventilation/heat recovery systems, combined with heat pumps, offer a means of significantly improving indoor air quality, as well as providing energy efficient heating and cooling required in buildings. This thesis is concerned with the development of a novel mechanical ventilation heat recovery/heat pump system for the domestic market. Several prototypes have been developed to provide mechanical ventilation with heat recovery. These systems utilise an annular array of revolving heat pipes which simultaneously transfer heat and impel air. The devices, therefore, act as fans as well as heat exchangers. The heat pipes have wire finned extended surfaces to enhance the heat transfer and fan effect. The systems use environmentally friendly refrigerants with no ozone depletion potential and very low global warming potential. A hybrid system was developed which incorporated a heat pump to provide winter heating and summer cooling. Tests were carried out on different prototype designs. The type of tinning, the working fluid charge and the number and geometry of heat pipes was varied. The prototypes provide up to 1000m3/hr airflow, have a maximum static pressure of 220Pa and have heat exchanger efficiencies of up to 65%. At an operating supply rate of 200m3/hr and static pressure 100Pa, the best performing prototype has a heat exchanger efficiency of 53%. The heat pump system used the hydrocarbon isobutane as the refrigerant. Heating COPs of up to 5 were measured. Typically the system can heat air from 0°C to 26°C at 200m3/hr with a whole system COP of 2. The contribution to knowledge from this research work is the development of a novel MVHR system and a novel MVHR heat pump system and the establishment of the performances of these systems.

This thesis aims to predict wind induced ventilation of a structure through the application of current analytical techniques, computational fluid dynamics simulations and novel techniques for ventilation flows induced by turbulent mechanisms. Validation of the predictions was carried out through full-scale measurements undertaken on a purpose built test structure. The structure was of cubic design with an external dimension of 6m. The construction of this full-scale research structure at Silsoe Research Institute, Bedfordshire, England, provided a unique opportunity for undertaking full-scale experimentation on a fundamental wind engineering test case which, prior to this thesis, had only been investigated using scale models in wind tunnels and computational simulations.

Natural ventilation has the potential to provide good indoor air quality, thermal comfort for occupants, and can also save energy and reduce CO2 emissions. Computational fluid dynamics (CFD) offers detailed information about indoor flow patterns, air movement, temperature and local draught distribution in buildings, so it has unique advantages as an efficient and cost-effective tool for optimum design in a complex built environment. This thesis shows the use of CFD to simulate the coupled external and internal flow field around a 6m cubic building with two small openings. To study both wind driven and combined wind and buoyancy driven cross ventilation through a full-scale cubic structure, un-structured grid CFD and a steady envelope flow model were applied to calculate mean ventilation rates. To validate the CFD results, full-scale experiments were undertaken under various weather conditions in England. For wind driven ventilation RANS model predictions were proved reliable when wind directions were near normal to the ventilation openings, i.e. 0o~30o. However, when the fluctuating ventilation played a more dominant role than the mean flow (90o) RANS models were incapable of predicting the total ventilation rate. Improved results may be expected by applying more sophisticated turbulence models, such as LES, weighted quasi-steady approximations, or unsteady envelope flow models. In the thesis experience on the modelling of combined wind and thermal effects is outlined and feedback is provided to CFD code developers to enable further improvements for building ventilation studies. The full-scale field testing data from this study is valuable for comparison with wind tunnel results and validation of CFD applications.

The European Union has an ongoing commitment to reducing CO2 emission as highlighted by its agreement at the Kyoto Summit. One approach to achieving these reductions would be to develop alternative energy sources for major energy demanding sectors. In the EU, about 40% of all energy consumed is associated with buildings and of this, about 60% is utilised in the housing sector. A major part of the energy demand of buildings could be met by utilising renewable energy sources, e.g. solar energy. Existing large-scale plants for power generation prevent efficient utilisation of the waste hot water produced. This means that to meet electricity demand, vast quantities of fossil fuels are burnt releasing unwanted pollutants (e.g., CO2 and NOx) into the atmosphere. Over the last decade, small-scale CHP plants have been introduced for many applications with proven environmental and economic benefits. In addition, solar energy has been used to generate electricity and provide hot water in conjunction with the CHP plants. Investigation of a hybrid heat pipe solar collector/CHP system was carried out in this research. The system is powered by solar and gas energy as well as the boiler waste heat to provide electricity and heating for residential buildings. Compared to the relevant system configurations, this system has the following innovative features: The solar collector was integrated with exhaust flue gas channels that allowed both solar energy and waste heat from exhaust gas to be utilised. Heat pipes as high efficiency heat transfer devices were incorporated in the collector panel. Both miniature and normal heat pipes were investigated, and this resulted in two types of collectors, e.g., thin membrane heat pipe solar collector, and hybrid heat pipe solar collector, to be produced for this application. A compact, lightweight turbine was applied in this system. Novel refrigerants, including n-pentane and hydrofluoroethers (HFEs), were employed as the working fluids for the CHP system. Use of the system would save primary energy of approximately 3,150kWh per year compared to the conventional electricity and heating supply systems, and this would result in reduction of CO2 emission of up to 1.5 tonnes. The running cost of the proposed system would also be lower. The research initially investigated the thermal performance of several heat pipes, including micro/miniature heat pipes, normal circular and rectangular heat pipes, with/without wicks. An analytical model was developed to evaluate the heat transport capacity for these heat pipes. A miniature heat pipe with parallel piped channel geometry was proposed. The variation of heat transport capacity for either micro/miniature or normal heat pipes with operation temperature, liquid fill level, inclination and channel geometry were investigated. Investigation of the operating characteristics of the selected heat pipes, e.g., two miniature and one mini heat pipes, and two normal heat pipes, was then carried out using both the numerical technique and experimental testing. It was found that the results from tests were in good agreement with the numerical predictions when the test conditions were close to the simulation assumptions. The research work further involved the design, modelling, construction and tests of two innovative heat pipe solar collectors, namely, the thin membrane heat pipe solar collector and the hybrid heat pipe solar collector. A computer model was developed to analyse the heat transfer in the collectors. Two collector efficiencies, η and η1, were defined to evaluate their thermal performance, which were all indicated as the function of a general parameter (tmean-ta)/In. Effects of the top cover, manifold as well as flue gas temperature and flow rate (for hybrid collector only) on collector efficiencies were investigated using the computer model developed. Laboratory tests were carried out to validate the modelling predictions and experimentally examine the thermal performance of the collectors. Comparison was made between the modelling and testing results, and the reasons for error formation were analysed. The research then considered the issues of the micro impulse-reaction turbine, which was another part of the integrated system. The structure configuration, coupling pattern with the generator as well as internal geometry contour of the turbine were described. The velocity, pressure and turbulent kinetic energy of the flow in the turbine were determined using numerical CFD prediction. In addition, experimental tests were carried out using a prototype system. The results of CFD simulation and testing show good agreement. This indicates that CFD can be used as a tool of optimizing turbine geometry and determining operating conditions. The research finally focused on the integrated system which brought the heat pipe solar collector, boiler and micro turbine together. The individual components, configurations and layout of the system were illustrated. Theoretical analysis was carried out to investigate thermodynamic cycle and heat transfer contained in the combined system, which is based on the assumption that the system operated on a typical Rankine cycle powered by both solar and gas energy. Tests for the prototype system was carried out to realistically evaluate its performance. Two types of turbine units were examined; one is an impulse-reaction turbine, and the other is a turbo-alternator. The turbo-alternator was found to be too small in capacity for this system thereby affecting its output significantly. The micro impulse reaction turbine was considered a better option. A typical testing showed that the majority of heat required for the turbine operation came from the boiler (7.65kW), and very little (0.23kW) from the solar collector. The gas consumption was 8.5kW. This operation resulted in an electricity output and domestic hot water generation, which were 1.34kW and 3.66kW respectively. The electrical efficiency was 16% and the thermal efficiency was 43%, resulting in an overall efficiency of 59%. Increasing the number of the collectors used would result in reduced heat output from the boiler. This would help in improving system performance and increasing efficiencies. In this application, number of collectors used would be 4 as the flue gas flow rate would only be sufficient to provide 4 to 5 such collectors for heat recovery. The research resulted in the proposal of another system configuration. The innovative concept is illustrated in Chapter 8, and its key technical issues are discussed.

This thesis investigates a novel combination of a jet-pump refrigeration cycle and a thermal (ice) storage (TIS) system that could substantially reduce the electrical energy requirements attributable to comfort cooling.Two methods of TIS were identified; spray ice TIS would use evaporative freezing to store ice on a vertical surface,and encapsulated ice TIS would freeze a bed of encapsulated elements by sublimation freezing.Thestudy also investigates jet-pump refrigeration at partload and a convergent-divergent design manufactured from a thermoset plastic to make recommendations for performance enhancement for a system that has a low COP. An experimental rig was built to investigate the novel concepts in the laboratory. Encapsulated ice TIS was superior to spray ice TIS because, for the same nominal secondary flow, sublimation freezing causes an increase in coolth storage rate of about 10 % compared to evaporative freezing. Encapsulated ice stores experience difficulties in fully discharging their coolth (approximately 6% in this case), but spray ice TIS can be used to produce an ice/brine slurry enabling all of the ice to be used, and so may be more suitable if the unmelted ice represents a large proportion of the cooling capacity. Approximately 85 % to 90 % of the ice formed on the vertical surface during spray ice TIS testing was formed by evaporative freezing from a falling film. At high saturation conditions, heat is transferred mainly by conduction across the falling film. Both the growth of an ice layer on a vertical surface and freezing of encapsulated elements were found to be successful, but a large data spread was observed during spray ice TIS testing. It was thought that a variation in the steady-state saturation conditions in the evaporator/ice store was caused by variability of droplet size distribution from the spray nozzle flow, which may make a full-scale system unreliable. The COP of the spray ice TIS system was approximately 0.15 compared to a COP of approximately 0.25 found during encapsulated ice TIS testing. The difference was because of the use of an over-expanded primary nozzle, which restricted secondary flow and increased momentum losses. A primary nozzle that expands close to the design evaporator saturation conditions should be used to maximise entrainment ratio. The COP of a jet-pump TIS is low, but a system designed to operate at off-peak periods could increase the COP to about 0.8 by taking advantage of the lower ambient conditions. The measurement of entrainment ratio was used successfully to determine ice storage rate and COP. This was valid because of the assumption that the saturation conditions in the evaporator/ice store approached steady-state. However, over longer periods that would be found in large-scale systems, the ice storage rate and entrainment ratio may fall substantially. The steady-state assumption could still be used to observe the change in evaporator conditions by sampling over short time intervals (30 minutes). At part-load, increases in evaporator saturation temperature could increase entrainment ratio substantially (50 % increase) for only a small reduction in critical pressure lift ratio Ns *(15 % reduction). A variation in chilled water temperature could be used to boost entrainment ratio at the peak demand. The variation in Ns* is too small to use this strategy to control the jet-pump with respect to condenser operating conditions. The entrainment ratio is approximately proportional to the diff-user to primary nozzle area ratio. A doubling of entrainment ratio was attained for only a 15% reduction in Ns*. The change in geometry from a constant area throat to a convergent-divergent design caused the flow through the jet-pump to vary with outlet conditions indicating that secondary flow was not choked. Higher entrainment ratios and pressure lift ratios were observed, but the entrainment ratio varied with outlet conditions in the form of peaks and troughs, making its operation unpredictable. This was thought to be caused by the restriction in secondary flow area due to the interaction of the primary jet and the curved wall. The convergent-divergent design manufactured from a thermoset plastic was successfully tested, showing that a plastic material can be used as a material of construction. In principle, a large number of jet-pump units could be manufactured from a single mould, reducing the first cost. The investigation proved the concept of jet-pump TIS. Waste-heat could be utilised over 24 hours and year round, increasing the efficiency of the process. The use of a convergent-divergent throat design, multiple geometry jet-pumps and operation at off-peak periods can maximise the performance over a cooling season, and be competitive with other TIS and chiller systems. The mass production of jet-pumps using injection moulding techniques could reduce substantially the capital cost of a system. All of these factors should encourage the development of such systems, so that the harmful emissions caused by the use of air conditioning systems can be minimised.

This thesis describes a theoretical and experimental investigation of the jet-pump refrigerator, and the application of Computational Fluid Dynamics (CFD) to improve the performance of the jet-pump, which lies at its heart. Within this thesis a number of new studies aimed at improving the COP of jet-pump refrigerators are carried out. These include an investigation of a novel jet-pump design methodology, (the Constant Rate of Momentum Change method), the application of CFD in the design of jet-pumps, the experimental testing of two new refrigerant fluids and finally, a comparative experimental investigation of performance benefits resulting from two cycle improvements that had not been tested before - these are the introduction of (i) a pre-heater (or recuperator) between the jet-pump and condenser, to preheat the liquid flow to the vapour generator, and (ii) a pre-cooler (or economiser) in the suction line between the evaporator and jet-pump, in order to sub-cool the liquid refrigerant in the line between the condenser and evaporator. Literature studies of jet-pump refrigerator technology and jet-pump design methodology are reviewed and discussed. A CFD model has been developed, assessed and validated against given experimental data. Simulations of a jet-pump that is part of a jet-pump refrigerator cycle was carried out to investigate the refrigerant flow structure and to assess the dominant influence of operating conditions and geometry. The validated CFD code was then used to optimize the design of the jet-pump for two new refrigerants (R236fa and R245fa). The resulting optimized jet-pumps were manufactured and tested experimentally over a wide range of operating conditions, using an adaptable test rig that was purpose-developed as part of this research work. Detailed experimental studies were carried out. All the experimentally determined results were compared to the CFD predicted values, and these showed good agreement for all the jet-pumps tested. These results showed that CFD has the potential to be an effective and powerful tool for simulating and optimising jet-pumps. The results also show that the jet-pump refrigerator should be considered if sources of low-grade heat are available.