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[en] Highlights: • A rare field experiment analysing community action on household energy saving. • Insulation interventions led to energy saving, but with 40% direct rebound. • Volunteer-led community activity following insulation upgrades had no measurable effect. • Comparative analysis suggests time and framing constraints limit effectiveness of community action. -- Abstract: A three-year field experiment was conducted with 185 prosperous households to assess whether behavioural interventions by a community environmental group during and after thermal upgrades (cavity wall and/or loft insulation) can achieve reductions in households’ energy use, including reductions in direct and indirect rebound. The engineering interventions on the thermal efficiency of dwellings appear effective in reducing energy use in both treatment and control groups: a direct rebound effect is estimated to be at most 40 per cent from the engineering interventions. However, across a range of measures of energy use, we observe no significant effect of the community behavioural intervention across the total lifetime of the project. Qualitative data collected on similar community groups suggests substantial constraints on their capacity to realise reductions in energy use amongst households.

[en] Efficiency of a finned single-pass solar air collector was studied. This paper presents the experimental study to investigate the effect of solar radiation and mass flow rate on efficiency. The fins attached at the back of absorbing plate to improve the thermal efficiency of the system. The results show that the efficiency is increased proportional to solar radiation and mass flow rate. Efficiency of the collector archived steady state when reach to certain value or can be said the maximum performance

[en] The Carnot, Diesel, Otto, and Brayton power cycles are reconsidered endoreversibly in finite time thermodynamics (FTT). In particular, the thermal efficiency of these standard power cycles is compared to the well-known results in classical thermodynamics. The present analysis based on FTT modelling shows that a reduction in both the maximum and minimum temperatures of the cycle causes the thermal efficiency to increase. This is antithetical to the existing trend in the classical references. Under the assumption of endoreversibility, the relation between the efficiencies is also changed to ${\mathrm{\eta <!--\; ??\; -->}}_{\mathrm{C}\mathrm{a}\mathrm{r}\mathrm{n}\mathrm{o}\mathrm{t}}><!--\; >\; -->{\mathrm{\eta <!--\; ??\; -->}}_{\mathrm{B}\mathrm{r}\mathrm{a}\mathrm{y}\mathrm{t}\mathrm{o}\mathrm{n}}><!--\; >\; -->{\mathrm{\eta <!--\; ??\; -->}}_{\mathrm{D}\mathrm{i}\mathrm{e}\mathrm{s}\mathrm{e}\mathrm{l}}><!--\; >\; -->{\mathrm{\eta <!--\; ??\; -->}}_{\mathrm{O}\mathrm{t}\mathrm{t}\mathrm{o}}$, which is again very different from the corresponding classical results. The present results benefit a better understanding of the important role of irreversibility on heat engines in classical thermodynamics. (paper)

[en] Presented here is a review of two methods by which the thermal contact resistance occurring at the metal-to-metal interfaces that exist in heat exchanges can be reduced. The two methods discussed, inserting a thin metal foil into the interface or coating one of the surfaces with a thin metallic coating, have the potential to significantly reduce the thermal contact resistance and thereby improve the overall system thermal efficiency and performance

[en] In the presented work, the specific features of the crystal lattice of the TISe type and the principle of producing semiconducting thallium chalcoindianates and alloys based on them with rareearth elements are described in detail. Correlations between the physical properties and the content of rare-earth elements in the compositions of the studied materials are given. The results of experimental studies on the radiation effects arising under the influence of gamma radiation are presented.

[en] This research examines some of the multiple benefits of a home energy efficiency upgrade programme for social housing tenants. Employing a quasi-experimental approach, we examine a range of objectively measured and self-reported outcomes, including metered gas consumption, for a control and upgrade group, before and after the upgrade. We drew our sample from a large home energy efficiency programme in Ireland, The SEAI Better Energy Communities Scheme, which provides funding for whole communities to upgrade the efficiency of their dwellings. Dwellings were selected for upgrade based on need, allowing us to control for observable dwelling characteristics correlated with selection into the trial. The upgrades undertaken were extensive relative to the average home energy improvement, with many dwellings receiving a number of measures. Households reported improvements across a range of outcomes associated with heating-related deprivation and comfort in the home. We use panel regression models to estimate the elasticity of gas demand with respect to the thermal efficiency of the dwellings. Overall, we find that use of natural gas fell much less than 1:1 for each increment to thermal efficiency of the home. For the average household in this study, about one third of the marginal increase in thermal efficiency was reflected in reduced gas demand. This result highlights issues with standard engineering models which are commonly used to assess the energy efficiency of dwellings and points to a behavioural response from households, potentially taking back some of the savings as increased internal temperatures.

[en] Highlights: • The work and efficiency of advanced gas turbine cycles are analytically optimized. • Polytropic efficiencies are used for the compression and expansion processes. • The overall and intermediate pressure ratios which maximise the net-work are given. • The ranges of the pressure ratios yielding a benefit in the efficiency are found. • The maximum-efficiency point is analytically given for the intercooled & reheat cycle. -- Abstract: The paper presents a theoretical analysis of advanced gas-turbine cycles. Specifically, three cycles are investigated, that is the intercooled, the reheat, and the intercooled and reheat cycles. The internal irreversibilities, which characterise the compression and expansion processes, are taken into account through the polytropic efficiencies of the compressors and turbines. New analytical formulations for the overall and intermediate pressure-ratios which maximise the net work of the three aforementioned cycles are proposed along with an order relation between these optimum pressure-ratios. Moreover, the thermal efficiency of these cycles is also analysed providing, among other findings, the ranges of the intermediate pressure-ratios returning a benefit in the thermal efficiency in comparison with the simple cycle. Finally, for the sole intercooled and reheat cycle, a novel analytical expression for the maximum point of the thermal efficiency is given. It is also shown that, for the intercooled and reheat cycle, there is a unique value of the overall pressure-ratio which simultaneously maximises the net work and the thermal efficiency. To give some quantitative information, consider a maximum to minimum cycle-temperature ratio equal to 1573/300 and a compressor (resp. turbine) polytropic-efficiency equal to 0.8 (resp. 0.88). The net work and the thermal efficiency are maximised by a set of overall pressure-ratios obeying an order relation. The simple, the reheat, the intercooled, and the intercooled and reheat cycles reach the maximum net-work (resp. thermal efficiency) for increasing values of the overall pressure-ratio, that is 8.550 (resp. 18.260), 14.950 (resp. 25.039), 20.846 (resp. 39.984), and 73.109 (resp. 73.109). The reheat cycle achieves a 34.899% (resp. 6.077%) gain in the net work (resp. thermal efficiency), while the intercooled cycle returns a 31.477% (resp. 15.970%) increment. The maximum net-work of the intercooled and reheat cycle exactly doubles that of the simple cycle. Finally, the maximum thermal efficiency of the intercooled and reheat cycle yields a 24.966% improvement in comparison with the simple one.

[en] Development and selection of membranes for membrane distillation (MD) could be accelerated if all performance-determining characteristics of the membrane could be obtained during MD operation without the need to recur to specialized or cumbersome porosity or thermal conductivity measurement techniques. By redefining the thermal efficiency, the Schofield method could be adapted to describe the flux without prior knowledge of membrane porosity, thickness, or thermal conductivity. A total of 17 commercially available membranes were analyzed in terms of flux and thermal efficiency to assess their suitability for application in MD. The thermal-efficiency based model described the flux with an average %RMSE of 4.5%, which was in the same range as the standard deviation on the measured flux. The redefinition of the thermal efficiency also enabled MD to be used as a novel thermal conductivity measurement device for thin porous hydrophobic films that cannot be measured with the conventional laser flash diffusivity technique.

[en] Here, we report on the experimental and theoretical understanding of seamless junction Au mesh network flexible transparent heaters. Three Au mesh transparent conductors (TCs) are fabricated using the photolithography-etching process to compare the influence of metal surface coverage on their electrical and thermal performance. The fabricated mesh networks are quite transparent (T ∼ 80%) in the 400–900 nm spectral region and exhibit small variation in sheet resistance (ΔR _max ∼ 0.12, 0.05, and 0.22 Ω □⁻¹) under different bending radii (minimum radii of ∼7.5 mm). The Au mesh with large surface coverage (i.e. ∼4.8%) exhibited the highest figure of merit (1035), and the Au mesh with small surface coverage (i.e. ∼2.5%), which eventually tested as a heater, exhibited the highest thermal efficiency (i.e. 249 °C/(W/cm²)) and temperature of 150 °C at the lowest input power (0.5 W cm⁻²). A 1D analytical heat transfer model is developed for quick estimation of temperature of heater samples. The thermal simulation of heaters is carried out using an ANSYS tool. The experimental, simulation and 1D analytical results are compared and validated, revealing that the simulation results are more aligned with experimental results. The flexible TCs with short response time and high thermal resistance are very useful in various flexible heating applications. (paper)