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AbstractUsing a low supply water temperature in heating conditions and a high water temperature during cooling can increase energy efficiency, use renewable energy sources, and provide a comfortable and healthy indoor climate. High temperature cooling and low temperature heating is achieved by reducing temperature difference in heat trans er and energy transportation process. The losses in temperature difference can be classified into three types: by heat/moisture exchange; by energy transportation through air/water circulation; by indoor terminal that releases heat/cooling to indoor condit oned space. The air handling process of HVAC system and indoor terminals are the key factor of reducing temperature differen e.Aiming at the losses in HVAC system, Annex 59, titled High Temperature Cooling & Low Temperature Heating in Buildings, is a new international cooperative work under the framework of International Energy Agency (IEA) Energy in Buildings and Communities (EBC). This paper introduc s the background, scope, objective, structure and deliverables of Annex 59. Annex 59 will try to present a new perspective and a new concept to analyze HVAC system in buildings. The goal of the Annex is to build up new concept of analyzing HVAC system from the perspective of reducing mixture loss and transfer loss and th n apply it in high temperature cooling and low temperature heating system.

Abstract A refrigeration system was developed which combines a basic vapor compression refrigeration cycle with an ejector cooling cycle. The ejector cooling cycle is driven by the waste heat from the condenser in the vapor compression refrigeration cycle. The additional cooling capacity from the ejector cycle is directly input into the evaporator of the vapor compression refrigeration cycle. The governing equations are derived based on energy and mass conservation in each component including the compressor, ejector, generator, booster and heat exchangers. The system performance is first analyzed for the on-design conditions. The results show that the COP is improved by 9.1% for R22 system. The system is then compared with a basic refrigeration system for variations of five important variables. The system analysis shows that this refrigeration system can effectively improve the COP by the ejector cycle with the refrigerant which has high compressor discharge temperature.

In order to complete the broadband simulation model of power transformer, and establish a systematic and complete model for studying fast transient interaction between transformer and power system, the frequency dependent characteristics of dielectric losses in power transformer were investigated. Several typical insulation structures in power transformers were considered and measuring techniques determined to study the dielectric losses. Frequency dependent dielectric losses in the range of 10-107 Hz were measured by a dielectric spectroscopy analyzer produced by Novocontrol. The characteristics of insulating papers and pressboard measured in the air and after immersing in the mineral oil were compared. Based on the dielectric relaxation theory, the number of dielectric relaxation was determined according to the measured data, and four typical model functions were adopted to fit the data and the consistency of fitting by these functions were compared and physical explanations of fitting parameters were described. Finally, a quantitative description of frequency dependent characteristics of insulation losses was proposed for improving the transformer simulation model.

Abstract Air change rate is a very important parameter for indoor air quality estimation as it influences the exchange of air pollutants between indoor and outdoor environments. Consequently, determining air change rate distribution is indispensable for assessment of a population's exposure to air pollutants. In this study, the annual and seasonal average infiltration rates (air change rate for window close conditions) of 180 representative residences were simulated using the multi-zone network airflow model (CONTAM) to understand the residential infiltration rate distributions in Beijing. The representative residences were selected by probability sampling based on building characteristics, including building type, floor area, number of rooms, construction year, number of floors, and building orientation. The results show that the annual average infiltration rates in Beijing range from 0.02 to 0.82 h−1 with a median value of 0.16 h−1. The empirical distributions of the annual and seasonal average residential infiltration rates in Beijing were provided. The annual average infiltration rates were also found to well fit a two-parameter lognormal distribution, the median and standard deviation of which is −1.79 and 0.62. Infiltration rates of 34 residences in Beijing were measured via the CO2 decay method, and the measured infiltration rates of residences matched the simulated distribution well. The differences between the simulated and measured infiltration rates are discussed.

Carbon metabolism of a chemical industrial park remains scarce in literature, due to overwhelming data collection workload and intricate interfirm flow examination. Based on five-year intensive data collection and verification, this research presents the findings of one-year static carbon metabolism in a typical Chinese fine chemical industrial park. As to the total direct carbon input (0.38 million tons), 32% concern chemicals production, while the remaining 68% are related to energy conversion. Three common metrics, carbon efficiency, C factor, and E factor are applied to assess the performance of carbon flows. Based on an analysis of 380 raw chemicals and 130 chemical products, performance of the three kinds of chemicals, pharmaceuticals, dyes, and other fine chemicals, and the chemical industrial park as a whole are considered and compared with similar industrial area, respectively. The carbon efficiency of chemicals production is 69%, while the other 31% ends up in waste. The interfirm carbon flow accounts for 3.4% of the carbon inputs in raw chemicals. Pursuing local environmental goals (i.e., abatement of odor, chemical oxygen demand, and solid waste) results in greater CO(2) emissions, which runs against protection of the global environment. Options to improve carbon efficiency were also discussed from three aspects. This study lays groundwork for quantifying greenhouse gas emissions, benchmarking carbon efficiency, and conducting life cycle assessment on the park level.

Abstract A two-dimensional (2D) model is developed to analyze the performance and efficiency of H 2 O/CO 2 co-electrolysis in tubular SOEC (solid oxide electrolysis cell). The model fully considers the fluid flow, heat/mass transfer and electrochemical/chemical reactions in the SOEC. The results show that RWGSR (reversed water-gas shift reaction) significantly promotes CO 2 conversion ratio. The effect of important operating parameters was comprehensively studied and optimal operating condition was determined. When the inlet gas flows in parallel flow mode with the velocity of 1 m s −1 , TSOEC with the H 2 O/CO 2 molar ratio of 1 at 700 °C at 1.4 V achieves the highest efficiency of 59.4% and the syngas conversion ratio of 43.8%. Lowering gas flow velocity decreases the syngas yield but promotes H 2 O/CO 2 convert ratio and efficiency. Finally, calculation found that counter flow is superior to parallel flow.

Abstract With the mushrooming deployment of volatile renewable energy sources as well as the intrinsic uncertainty from the demand side, secure and economic energy dispatch has become increasingly challenging for energy systems, especially for the emerging and promising integrated electric-gas system. Aside from the aforementioned uncertainties, the dispatch of the integrated electric-gas system suffers from two inherent obstacles, which are model nonconvexities, originating from the Weymouth equations in the gas network, and the demand-side differentiated gas delivery priorities according to current industrial practice, respectively. To deal with the conundrum, an adjustable robust dispatch method is proposed for operating the integrated electric-gas system, where uncertain wind generation outputs and gas loads are described by intervals. In contrast to existing work employing pre-determined intervals, the admissible wind output intervals in this paper are optimized, reflecting the interdependencies between the regulation capabilities of gas-fired generation and the gas delivery adequacy. By this means, gas delivery priority is considered in comply with gas industrial practice, and it also provides a more flexible mechanism to maintain robustness of the dispatch strategy. Through analyzing the feasibility impact of uncertain variables, a deterministic robust counterpart is derived, in which uncertainties are eliminated based on affine generator dispatch and estimation of total line pack. Furthermore, nonconvex quadratic terms in the Weymouth equations are expressed as difference-of-convex functions. A sequential convex optimization procedure is developed, and a heuristic method is suggested to initiate the sequential algorithm. The proposed models and methods are tested on three test systems. Key impact factors on the dispatch strategy, such as gas prices, wind generation forecast accuracy and gas network initial operation conditions, are analyzed, and the computational benefits brought by convex programming are validated by scalability tests.

The present paper proposes an Eulerian-Eulerian two-phase model for non-equilibrium condensing flow in steam turbines. This model is especially suitable for upwind finite volume scheme. An approximate Roe type flux using real water/vapor property is constructed to calculate the upwind wet-steam flux. This flux fully couples the wetness fraction with other conservative variables in the Jacobian Matrix whose eigen-vector and eigen-value are analitically derived. A novel treatment of real wet-steam property is developed by constructing a 3-DOFs TTSE table according to IAPWS97 formulas. The table is actually a cubic and uses the mixture’s density, the mixture’s internal energy and wetness as independent variables. Besides homogeneous condensation, heterogeneous condensing is also integrated into the model, which facilitates simulating the effect of salt impurities. The above methods are validated through two nozzle and one turbine cascade calculations and finally applied to a model LP steam turbine stage. Results show that the current model is very robust and is able to correctly capture the non-equilibrium condensation phenomena.

Abstract The civil nuclear energy deployment in China is important for future “Nuclear Renaissance” of China and worldwide. Compared to the other nations that developed their nuclear power energy system in last century, China can take advantage of the research and mistakes made by those states with regards to the back-end of the nuclear fuel cycle (NFC). The spent fuel accumulated by decades of operations of civil nuclear power is today a big burden for the nuclear industry. China must carefully plan the NFC for a sustainable development of the nuclear energy with special consideration to closing the fuel cycle. The present paper addresses the NFC option and implication of a LWR reactors scenario development and of a fast reactor park developed after 2035 and 2050, and covers the historical development of nuclear energy in China (i.e. from the first criticality of the first reactor) to the year 2100. The paper studies the partition and transmutation strategy with the use of accelerator driven system (ADS) to burn the MA to understand the ADS impact on the NFC and to estimate the number and the necessary deploying schedule of the ADS reactors to limit the minor actinides stock build up. The code INFCIS developed by the International Atomic Energy Agency (IAEA) is used in the present study.