Case Study of Optimized Cascaded Phase Change Thermal Energy Storage Unit

Phase change materials are paid increasing attention by the scholars in the past decades. For maintaining a relatively constant renewable energy output as a competent alternative for fossil fuel replacement, phase change storage unit are widely studied. However, for better pursuit of thermal energy performance and energy efficiency, only single staged phase change storage unit is not enough for increasing thermal requirements. Therefore, a triple staged phase change thermal energy storage unit have been proposed in this study. Meanwhile, correspondent comparison with single staged counterpart have been conducted along with related optimization. It has been concluded that the proposed thermal storage unit achieved 334.95 J/s & 41.54% / 186.37 J/s & 53.22 % in thermal energy exchange rate & exergy efficiency during endothermic/exothermic respectively. 3/21.4 L/min are the optimal circulating heat transfer fluid flowrates for endothermic/exothermic (better discharging rate)/ exothermic (better energy efficiency). Moreover, 100/9/15 are the best temperatures of circulating water for endothermic/ exothermic (better discharging rate)/ exothermic (better energy efficiency)

Stochastic Downsampling for Cost-Adjustable Inference and Improved Regularization in Convolutional Networks

It is desirable to train convolutional networks (CNNs) to run more efficiently during inference. In many cases however, the computational budget that the system has for inference cannot be known beforehand during training, or the inference budget is dependent on the changing real-time resource availability. Thus, it is inadequate to train just inference-efficient CNNs, whose inference costs are not adjustable and cannot adapt to varied inference budgets. We propose a novel approach for cost-adjustable inference in CNNs - Stochastic Downsampling Point (SDPoint). During training, SDPoint applies feature map downsampling to a random point in the layer hierarchy, with a random downsampling ratio. The different stochastic downsampling configurations known as SDPoint instances (of the same model) have computational costs different from each other, while being trained to minimize the same prediction loss. Sharing network parameters across different instances provides significant regularization boost. During inference, one may handpick a SDPoint instance that best fits the inference budget. The effectiveness of SDPoint, as both a cost-adjustable inference approach and a regularizer, is validated through extensive experiments on image classification

Paradoxical phenomenon in urban renewal practices: promotion of sustainable construction versus buildings’ short lifespan

The current urban renewal programs in some developing countries, such as China, are at the expense of demolishing a huge number of existing buildings without distinction. As a consequence, the buildings’ short lifespan due to premature demolition and resultant adverse impacts on environment and society have been criticized for not being in line with sustainable development principles. This study therefore examines impacts of urban renewal practices on buildings’ lifespan by referring to a typical urban renewal region in western China – the Gailanxi region of Chongqing city which is considered representative. Findings show in current practices, little consideration is given to the implications of building demolitions across economic, social and environmental horizons collectively. As a result, premature demolition due to requirements of urban renewal has been a major factor leading to the significantly short lifespan of buildings. This is against the core intention of implementing urban renewal, which is promoting sustainability of the cities. Particularly, buildings’ short lifespan results in consequences against sustainable construction principles, such as energy and resources waste, construction waste generation, environmental pollution, and higher lifecycle costs of buildings. Furthermore, building demolitions without distinction lead to losses of valuable historic buildings. Therefore, the urban renewal process presents a paradoxical phenomenon: the promotion of sustainable construction versus buildings’ short lifespan. The dominance of economic consideration in the decision-making on buildings is considered as the underlying reason to the paradox. The learned experience presented in this study should be built into the decision-making process for carrying out future urban renewal programs

Heat Transfer Correlations for Supercritical Water in Vertically Upward Tubes

Supercritical pressure water (SCW) has been widely used in many engineering fields and industries, such as fossil fuel-fired power plants, newly developed Gen-IV nuclear power plants and so forth. Heat transfer characteristics of SCW are of great importance for both design and safe operation of the related systems. Many heat transfer correlations have been developed in the history for predicting the heat transfer characteristics of SCW. However, the prediction accuracy of the existing correlations is less than satisfactory, especially in the cases with deteriorated heat transfer (DHT) because of the severe and quick variation in thermal physical properties of SCW in the vicinity of the fluids’ pseudo critical point. It is very necessary to develop new correlations for the heat transfer of SCW to meet the engineering requirements for satisfactory prediction of the heat transfer behavior of SCW. In this chapter, experimental data on heat transfer of SCW are extensively collected from published literatures, and the performance of the existing heat transfer correlations for SCW are reviewed and quantitatively evaluated against the collected experimental data, and then a new heat transfer correlation for SCW with high prediction accuracy is proposed

Nutritional Interventions Improved Rumen Functions and Promoted Compensatory Growth of Growth-Retarded Yaks as Revealed by Integrated Transcripts and Microbiome Analyses

Growth retardation reduces the incomes of livestock farming. However, effective nutritional interventions to promote compensatory growth and the mechanisms involving digestive tract microbiomes and transcripts have yet to be elucidated. In this study, Qinghai plateau yaks, which frequently suffer from growth retardation due to malnutrition, were used as an experimental model. Young growth-retarded yaks were pastured (GRP), fed basal ration (GRB), fed basal ration addition cysteamine hydrochloride (CSH; GRBC) or active dry yeast (ADY; GRBY). Another group of growth normal yak was pastured as a positive control (GNP). After 60-day nutritional interventions, the results showed that the average daily gain (ADG) of GRB was similar to the level of GNP, and the growth rates of GRBC and GRBY were significantly higher than the level of GNP (P < 0.05). Basal rations addition of CSH or ADY either improved the serum biochemical indexes, decreased serum LPS concentration, facilitated ruminal epithelium development and volatile fatty acids (VFA) fermentation of growth-retarded yaks. Comparative transcriptome in rumen epithelium between growth-retarded and normal yaks identified the differentially expressed genes mainly enriched in immune system, digestive system, extracellular matrix and cell adhesion pathways. CSH addition and ADY addition in basal rations upregulated ruminal VFA absorption (SLC26A3, PAT1, MCT1) and cell junction (CLDN1, CDH1, OCLN) gene expression, and downregulated complement system (C2, C7) gene expression in the growth-retarded yaks. 16S rDNA results showed that CSH addition and ADY addition in basal rations increased the rumen beneficial bacterial populations (Prevotella_1, Butyrivibrio_2, Fibrobacter) of growth-retarded yaks. The correlation analysis identified that ruminal VFAs and beneficial bacteria abundance were significantly positively correlated with cell junction and VFA absorption gene expressions and negatively correlated with complement system gene expressions on the ruminal epithelium. Therefore, CSH addition and ADY addition in basal rations promoted rumen health and body growth of growth-retarded yaks, of which basal ration addition of ADY had the optimal growth-promoting effects. These results suggested that improving nutrition and probiotics addition is a more effective method to improve growth retardation caused by gastrointestinal function deficiencies

Building Energy Storage Panel Based on Paraffin/Expanded Perlite: Preparation and Thermal Performance Study

This study is focused on the preparation and performance of a building energy storage panel (BESP). The BESP was fabricated through a mold pressing method based on phase change material particle (PCMP), which was prepared in two steps: vacuum absorption and surface film coating. Firstly, phase change material (PCM) was incorporated into expanded perlite (EP) through a vacuum absorption method to obtain composite PCM; secondly, the composite PCM was immersed into the mixture of colloidal silica and organic acrylate, and then it was taken out and dried naturally. A series of experiments, including differential scanning calorimeter (DSC), scanning electron microscope (SEM), best matching test, and durability test, have been conducted to characterize and analyze the thermophysical property and reliability of PCMP. Additionally, the thermal performance of BESP was studied through a dynamic thermal property test. The results have showed that: (1) the surface film coating procedure can effectively solve the leakage problem of composite phase change material prepared by vacuum impregnation; (2) the optimum adsorption ratio for paraffin and EP was 52.5:47.5 in mass fraction, and the PCMP has good thermal properties, stability, and durability; and (3) in the process of dynamic thermal performance test, BESP have low temperature variation, significant temperature lagging, and large heat storage ability, which indicated the potential of BESP in the application of building energy efficiency

Exploring the optimal return air height of different air supply modes based on energy consumption analysis and TOPSIS evaluation method

The side return air is considered to be a ventilation form that can effectively remove indoor particulate matter, and relevant scholars have little research on the height of air return outlet for different air supply methods. In this paper, a single-person ward experimental cabin is established, and the focus is to study the effect of different side return air outlet heights on the particle removal effect under three air supply forms. And use CFD simulation to increase the type of return air outlet height, finally use the technique for order of preference by similarity to ideal solution (TOPSIS) method to comprehensively evaluate the pros and cons of 60 working conditions. The results show that the optimal return air height of top air supply and underfloor air supply is 1.2m, and the best working condition of side air supply is 1.6m air supply-0.7m air return of 12ACH. Most of the working conditions of side air supply are better, followed by top air supply, and finally underfloor air supply

Experimental study on the robustness of ventilation systems in the control of walking-induced disturbances under different walking modes and temperatures

Ventilation system’s effectiveness can be affected by walking-induced disturbances. A series of experiments were performed in a chamber in this study (6.0 m × 5.9 m × 2.5 m) to measure the walking-induced temperature/flow/pollution field fluctuation characteristics. A method for quantifying the robustness of a ventilation system in the control of walking-induced fluctuations was used in this study. The experimental results showed that the cumulative particle exposure levels under walking modes W1, W2 and W3 were 2.04 ± 0.27, 1.72 ± 0.26 and 0.87 ± 0.12 times the exposure levels without human walking. The four ventilation systems all performed well in indoor temperature disturbance control; however, different walking modes and ventilation systems would result in different walking-induced disturbances of the flow and pollutant fields. For the flow field, the highest range scale robustness value was achieved by the side supply and side return (SS) system. For the pollutant field, the range scale robustness value of the SS system was still the highest, 18.7% larger than the lowest value. With the increase in temperature from 18 °C to 28 °C , the range and time scale robustness of the different ventilation systems decreased by 7.7–18.4% and 1.3–15.7%, respectively