This study concerns measurement and prediction of single-phase and flow boiling heat transfer coefficients and pressure drops in mini multi-channel geometries with and without interconnecting passages, including plate channel; parallel channel; in-line pin-fin and in-line off-set pin-fin surfaces. Experiments were performed with refrigerant R113 and deionised water at atmospheric pressure. Single-phase and flow boiling heat transfer coefficients and pressure drops were obtained over a range of effective heat fluxes and mass fluxes. For the plate and parallel channel surfaces, the results obtained have been compared with several published macro- and micro-channels correlations. For the in-line and in-line off-set pin fin surfaces, as the geometries have some similarities with tube bundles, the results obtained have been predicted using the standard correlations for tube bundles. The results also have been compared with several existing correlations developed based on macro-scale tube bundles and micro-pin-fin surfaces data. The saturated flow boiling heat transfer coefficients for the parallel channel and pin-fin surfaces were similar to within the experimental uncertainty, and considerably higher than the plate channel values, all dependent on heat flux and reasonably independent of mass flux and vapour mass fraction. This indicated that the dominant heat-transfer mechanism in the saturated boiling flow regime was nucleate boiling for all surfaces. The parallel channel, in-line and off-set pin-fin surfaces improved heat transfer by increasing the surface area and the heat transfer coefficient in comparison with the plate channel surface. The two-phase pressure drops in the parallel channel and pin-fin surfaces were considerably larger than that for the plate channel surface. Thus, the reduction in wall temperature is achieved by a significant pressure drop penalty. For the pin-fin surfaces, at low vapour qualities the heat transfer coefficients were in reasonable agreement with the conventional scale tube bundles correlations however as the vapour quality increases, the correlations were not able to predict the heat transfer coefficient as unlike the conventionally-sized tube bundles, the convective enhancement does not happen in the mini-pin-fin surfaces tested. The nucleate pool boiling correlation of Cooper (1984) provided a good agreement with the data for all surfaces tests with R113 and deionised water. The measured two-phase pressure drops for both pin-fin surfaces tests with R113 and deionised water were in a good agreement with the predicted values obtained from standard correlations for tube bundles, indicating pressure drop methods maybe transferable.

This thesis describes three connected stages of development and analysis of residential heat pump energy use: firstly, the analysis of heat pump performance data from a monitoring study of ground source heat pumps; secondly, the definition and development of a generalised residential heat pump energy model embedded within an enhanced dwelling energy model; finally, the analysis of the effects of possible residential heat pump installation scenarios on the UK energy supply and carbon emissions. The monitoring study involved three ground source heat pump installations. The data collected consisted of heat output, electric power input, system temperatures and system status indicators. Analysis indicated that these systems showed reductions in carbon emissions from homes ranging from 18% to 37% compared with their counterfactual fuel-burning systems. The monitoring study provided empirical values to parameterise the heat pump model which was built around a linear regression relationship of heat pump COP to source / sink temperature differential based on heat pump performance data from standard laboratory test results. This model was added in a new module to enhance the BRE domestic energy model, BREDEM-8, which provides monthly estimates. Estimating rules were included for energy use from bivalent alternate, bivalent parallel operation and space cooling. The enhanced BREDEM-8 model was used to analyse the effects of possible residential heat pump installations within a housing stock energy model developed using the English Housing Survey datasets as a data source. Baseline estimates for the current stock were created using data reduction techniques to provide parameters (u-values, glazing details) for the enhanced BREDEM-8 model. Scenarios for heat pump deployments were created for the periods up to 2020 and 2050, selecting dwellings for heat pump application according to scenarios reflecting the perceived needs of the period, ie. the likely reduction in UK generating capacity up to 2020 and CO2 emissions reduction targets to 2050. Results showed that up to 2020, a policy of targeting dwellings with the highest overall emissions for replacement would reduce carbon emissions by 7.6%, at the expense of a 12% increase in electricity consumption. Targeting dwellings with the highest emitting existing systems caused a smaller increase in electricity consumption of about 6.5% with carbon emissions reduced by about 6.8%. The scenarios for the period to 2050, including 80% replacement of gas systems with heat pumps, gave an estimated 80% reduction in carbon emissions, when accompanied by an similar reduction in the carbon intensity of electricity generation and bringing about an increase in electricity consumption of somewhat over 40%. The effect of the more extreme scenario is to replace all but a small proportion of the energy used for heating and hot water with standard rate electricity, in 84.6% of the dwellings, and retaining gas in the remainder, 15.2%, bringing about a radical shift to electric heating throughout the housing stock.

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No description available.

This project sought to study the heat transfer and Kapitza resistance of fluids across interfaces, nanopores and nanochannels with varying sti.ness constants, mass and energy intermolecular in- teraction strength of wall and fluid particles. An Einstein-Maxwell molecular dynamics thermal wall model is developed. The developed modeling approach is shown to provide dual energy and momentum transport exchange across solid-liquid interfaces and nanofluidic channels. Cont/d.

According to the second law of thermodynamics, no process can be 100% efficient and all processes must increase the total entropy of the system they occupy. Therefore, living systems require a constant influx of low-entropy energy to survive, giving an evolutionary advantage to those that produce less waste. Odum suggested that ecosystems would therefore develop mechanisms for reducing entropy production per unit biomass, as they matured. Isothermal calorimetry allows the direct measurement of waste heat emitted from any system, including soils and the life within them. However, upon review it became apparent that current methods employed in the analysis of soil microbial communities via isothermal calorimetry are outdated and in need of review. An experiment was conducted to troubleshoot the method and appropriate modifications were made. A second experiment was conducted to test the microbial community response to pre-incubation prior to calorimetric analysis at 20°C, concluding that samples should be pre-incubated for ten to sixteen days prior to analysis at 20°C. Subsequently, experiments were carried out to establish how much waste heat was produced by soil microbial communities in the context of various ecological gradients, following glucose amendment. Results for enthalpy efficiency (ηeff) proved inconclusive, whereas results for substrate induced heat production (SIHP), where heat output is expressed per unit biomass, indicated that soil microbial communities produced significantly more waste heat when subjected to long-term metals induced stress and short-term copper-induced stress. In addition, a reduction in the production of waste heat generated by soil microbial communities associated with primary succession along a glacier foreland was observed. This provides evidence that living systems do indeed evolve towards greater thermodynamic efficiency, manifest via the reduction of energetic waste.

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This thesis presents an in-depth investigation into the performance of a novel integrated back pass solar collector (BPSC) system, including the monitoring of a full scale BPSC over two years. BPSC are special type of heat exchangers that absorb incident solar radiation, and convert it to useful thermal energy via a photothermal process. In a BPSC, the absorber transfers the energy from the solar irradiance to the air flowing through the collector by forced convection. This heated air inside the collector is then transported as circulating air directly into the building space.

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The gas turbine fuel injector hs been the focus of considerable on-going research and development for over fifty years in order to satisfy the continuously evolving requirements with regard to combustion performance, fuel consumption and pollutant emissions. This exposition attempts to summarise the principal findings from the authors own research during the past two decades, and to identify their significance within the global framework of related studies in the area of gas turbine fuel injection. His recent studies on the structure of sprays in the near-nozzle region, encompassing simplex, pressure-swirl and engine-standard, pre-filming airblast atomizers, are characterised by an unparalleled combination of near-full power air density and liquid throughput, thereby extending significantly the knowledge database on the performance of these nozzles. They also served to reconcile the long-standing apparent contradictions in the open literature concerning the effect of ambient air pressure variation upon spray SMD for the simplex swirl injector. Moreover, they showed for the first time that the near-nozzle spray trajectory and overall mean drop size characteristics of the types of airblast nozzles used on engines are significantly different from those of the laboratory-scale atomizers featured in earlier research efforts. This is a reflection principally of the distinctive nature and scale of the fuel-air interactions involved in the two different environments. The new knowledge and understanding generated by the author's work on the plain-jet airblast concept has found practical application in large-scale industrial gas turbine engines. It is also contributing to the design of certain hybrid fuel injector configurations, which are now being offered either as an altemative to or in combination with the more established pre-filming concept. The limit of capability of both the laser sheet imaging technique developed by the author and the commercially available phase Doppler instrument have, for the first time, been successfully explored at the extreme conditions of high air density and high fuel throughputs encountered in modern gas turbines - yielding generally plausible isothermal spray property data.