Prediction of the theoretical and semi-empirical model of ambient temperature

It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is often, but not always, based upon experience or knowledge. Although guaranteed accurate information about the future is in many cases impossible, prediction can be useful to assist in making plans about possible developments. As a result, temperature profiles can be developed which accurately represent the expected ambient temperature exposure that this environment experiences during measurement. The ambient temperature over time is modeled based on the previous T _min and T _max data and using a Lagrange interpolation. To observe the comprehensive variation of ambient temperature the profile must be determined numerically. The model proposed in this paper can provide an acceptable way to measure the change in ambient temperature.     

Estimation of hourly temperature data from their monthly average values:: case study of Greece

An algorithm for the extraction of hourly temperature distributions from their monthly average values is presented. The algorithm is applicable to broad regions (country level) and is especially useful for the approximate estimation of heating degree-days. This last quantity, which is indispensable for the evaluation of space heating projects, can be calculated for various base temperatures and for cases where heating is either perpetually applied or during selected hours of a day only. The algorithm is analysed and compared with previously suggested ones, while a case study is additionally included to demonstrate its applicability. As an immediate consequence of comprehensive tables with temperature data and a map which are also embodied in the paper, approximate hourly temperature data are extractable for all over Greece, the country which is referred to in the case study.     

Estimation of ambient temperature bin data from monthly average temperatures and solar clearness index. Validation of the methodology in two Greek cities

Ambient temperature bin data are used for estimating the energy consumption in HVAC systems with air-source heat pumps and cooling equipment. In this paper a methodology for estimating the ambient temperature bin data, based on monthly average outdoor temperatures and solar clearness index, is presented. For the two most populated cities of Greece, namely Athens and Thessaloniki, the estimated data are compared to the bin data produced by statistical analysis of 10 years hourly dry-bulb temperature measurements. Both data sets were also used for estimating the heating and cooling energy requirements of a case study building. The results obtained are similar, with very small differences, suggesting that the proposed methodology can be used for estimating bin data for other cities.     

Off-design performance of a chemical looping combustion （CLC） combined cycle： effects of ambient temperature

The present work investigates the influence of ambient temperature on the steady-state off-design thermodynamic performance of a chemical looping combustion （CLC） combined cycle. A sensitivity analysis of the CLC reactor system was conducted, which shows that the parameters that influence the temperatures of the CLC reactors most are the flow rate and temperature of air entering the air reactor. For the ambient temperature variation, three off-design control strategies have been assumed and compared： 1） without any Inlet Guide Vane （IGV） control, 2） IGV control to maintain air reactor temperature and 3） IGV control to maintain constant fuel reactor temperature, aside from fuel flow rate adjusting. Results indicate that, compared with the conventional combined cycle, due to the requirement of pressure balance at outlet of the two CLC reactors, CLC combined cycle shows completely different off-design thermodynamic characteristics regardless of the control strategy adopted. For the first control strategy, temperatures of the two CLC reactors both rise obviously as ambient temperature increases. IGV control adopted by the second and the third strategy has the effect to maintain one of the two reactors＇ temperatures at de- sign condition when ambient temperature is above design point. Compare with the second strategy, the third would induce more severe decrease of efficiency and output power of the CLC combined cycle.     

Simulation and experiment of a PV-MCHP-TE system and ambient parameters impacts

Combining the photovoltaic (PV) with the thermoelectric (TE) can obtain higher electrical outputs, because the thermal energy produced by the PV cells can be used to produce more electricity by the TE device. This paper built the mathematical model on the energy flow of the PV–microchannel heat pipe (MCHP)–TE system then verified the correctness of the model via the experiment. In addition, the impacts of the different wind speed, different solar radiation, and different ambient temperature on the PV-MCHP-TE system have been analysed. The result shows that the maximum difference value of the power output between the simulation and experiment is 0.16 W, so the simulated values and experimental values are in good agreement. At the same time, within the scope of the ambient parameters set in the simulation, when the solar radiation raises, the electrical efficiency of the PV-MCHP-TE system decreases, but when the wind speed raises, the electrical efficiency of this system will decrease more and more slowly. This work will lay the foundation for the performance forecasting of the system throughout the year.     

Design, development and performance monitoring of a photovoltaic-thermal (PVT) air collector

The photovoltaic-thermal (PVT) systems allow the enhancement of the energy performance of photovoltaics, by removing thermal energy and subsequently decreasing the operating temperature of the cells. The possibility of the utilization of heat for climatization makes them attractive for the building integration. In order to diffuse this kind of solar systems it is necessary to translate the basic concepts into efficient and functional technological components and associated performance should be evaluated in a reliable manner. This paper presents the experimental and theoretical results of a research and development program carried out at the Politecnico di Milano on the design, development and performance monitoring of a hybrid PVT air collector. One of the main products of the research consists of a simulation model for performance prediction of the system. This R&D program led to the development of the TIS (tetto integrale solarizzato, i.e. integrated solar roof), an innovative technological system for building integration of hybrid PVT air collectors. The successful commercial application of the TIS in a research center building is also shown as a case study.     

旋流燃烧器螺旋伸展长度对高温空气燃烧特性的影响

以工业炉的高温空气燃烧技术应用为背景,对一个同心式轴向旋流高温空气燃烧器单烧嘴燃烧室内的高温空气燃烧特性进行了数值研究.燃烧室尺寸为600 mm×600 mm×1000 mm,燃烧器烧嘴由位于中心的圆形直射流燃气喷口和其外围的同心轴向旋流高温预热空气射流喷口构成.湍流输运方程采用RSM模型,气相燃烧模型采用β函数的PD...     

The effect of ambient pressure on the evaporation of a single droplet and a spray

The effect of ambient pressure on the evaporation of a droplet and a spray of n-heptane was investigated using a model for evaporation at high pressure. This model considered phase equilibrium using the fugacities of the liquid and gas phases for the behavior of a gas being real, and its importance in the calculation of the evaporation of a droplet or spray at high pressures was demonstrated. For the evaporation of a single droplet, the fact that the droplet's lifetime increased with pressure at a low ambient temperature, but decreased at high temperatures, was explained with pressure and the droplet's temperature determining phase equilibrium. In this study, it was also found that the evaporation of a spray can be explained in terms of multiplex dependencies of the atomization and evaporation of a single droplet. The evaporation of a spray was enhanced by increasing the ambient pressure and this effect was more dominant at higher ambient temperatures.     

Optimization of properties and operating parameters of a passive DMFC mini-stack at ambient temperature

An investigation of properties and operating parameters of a passive DMFC monopolar mini-stack, such as catalyst loading and methanol concentration, was carried out. From this analysis, it was derived that a proper Pt loading is necessary to achieve the best compromise between electrode thickness and number of catalytic sites for the anode and cathode reactions to occur at suitable rates. Methanol concentrations ranging from 1 M up to 10 M and an air-breathing operation mode were investigated. A maximum power of 225 mW was obtained at ambient conditions for a three-cell stack, with an active single cell area of 4 cm², corresponding to a power density of about 20 mW cm⁻².     

Development and optimization of artificial neural network algorithms for the prediction of building specific local temperature for HVAC control

This research accounts for the outcome of a major cloud-based smart dual fuel switching system (SDFSS) project, which is a dual-fuel integrated hybrid heating, ventilation, and air conditioning (HVAC) system in residential homes. The SDFSS was developed to enable optimized, flexible, and cost-effective switching between the natural gas furnace and electric air source heat pump (ASHP). In order to meet the optimal energy consumption requirements in the house and provide thermal comfort for the residents, various high-quality sensors and meters were installed to record multiple data points inside and outside the house. The performance of the system was monitored in the long term, which is a common practice in energy monitoring projects. Outdoor temperature data plays the most crucial role in operating HVAC systems and also is a key variable in the decision-making algorithm of the SDFSS controller. Therefore, this study introduces an innovative and unique approach to obtain the outdoor temperature that could potentially replace high precision sensors with a data-driven model utilizing weather station data at a time resolution of 2 minutes and 1 hour. In this work, a series of artificial neural network algorithms were developed, optimized, and implemented to predict the outdoor temperature with an average of 0.99 coefficient of correlation (R), 1.011 mean absolute error (MAE), and 1.315 root mean square error (RMSE). It has been demonstrated that the developed ANN is a reliable and powerful tool in predicting outdoor temperature. Thus, the proposed model is strongly suggested to be implemented as an alternative to temperature sensors in hybrid energy systems or similar systems requiring accurate ambient temperature measurements.     

Impact of air contamination by NOx on the performance of high temperature PEM fuel cells

High temperature PEM fuel cells show enhanced tolerances regarding fuel impurities like CO for use in various applications. However, the impact of air impurities like NO_x on the cell behavior is not completely understood yet. This study provides systematic investigation during 500 h of operation in presence of cathode air containing 10 ppm NO or NO₂. Nitrogen oxides provoke a strongly and linearly decreasing voltage of 245.3 ± 18.5 μV h⁻¹ and highly comparable damage that verifies similar HT-PEMFC degradation via both oxides. Cyclic voltammetry and electron microscopy reveal the loss of electrochemical catalyst surface by selectively poisoned surface and enforced catalyst particle growth. Impedance spectroscopy reveals besides increased electrode charge transfer resistances an affected proton conductivity. In contrast, SO₂/NO₂ impurity mixture in real occurring ratio causes less voltage decay due to a positive SO₂ impact through H₂SO₄ formation causing further shown and discussed effects like nitrate formation and discharge.     

气化参数对高温空气气化的影响

介绍了生物质高温空气气化思想和系统的工作原理及其过程，并就气化参数对生物质高温空气气化的影响进行了深入的分析，结畏发现：随蒸汽消耗率的增加气化温度降低，而气化所得的煤气热值增大；气化温度随氮碳比的增大而升高，而气化所得的煤气热值却随氮碳比的增加而降低；煤气热值随气化温度的增加而增大，但是增加量不大。     

Improvement of part-load performance of gas turbine by adjusting compressor inlet air temperature and IGV opening

A novel adjusting method for improving gas turbine (GT) efficiency and surge margin (SM) under part-load conditions is proposed. This method adopts the inlet air heating technology, which uses the waste heat of low-grade heat source and the inlet guide vane (IGV) opening adjustment. Moreover, the regulation rules of the compressor inlet air temperature and the IGV opening are studied comprehensively to optimize GT performance. A model and calculation method for an equilibrium running line is adopted based on the characteristic curves of the compressor and turbine. The equilibrium running lines calculated through the calculation method involve three part-load conditions and three IGV openings with different inlet air temperatures. The results show that there is an optimal matching relationship between IGV opening and inlet air temperature. For the best GT performance of a given load, the IGV could be adjusted according to inlet air temperature. In addition, inlet air heating has a considerable potential for the improvement of part-load performance of GT due to the increase in compressor efficiency, combustion efficiency, and turbine efficiency as well as turbine inlet temperature, when inlet air temperature is lower than the optimal value with different IGV openings. Further, when the IGV is in a full opening state and an optimal inlet air temperature is achieved by using the inlet air heating technology, GT efficiency and SM can be obviously higher than other IGV openings. The IGV can be left unadjusted, even when the load is as low as 50%. These findings indicate that inlet air heating has a great potential to replace the IGV to regulate load because GT efficiency and SM can be remarkably improved, which is different from the traditional viewpoints.     

City-block-scale sensitivity of electricity consumption to air temperature and air humidity in business districts of Tokyo,Japan

The sensitivity of electricity consumption to air temperature and air humidity are effective indicators in evaluating the impacts of countermeasures against urban heat islands. The impacts of these countermeasures vary in time and space and so sensitivities based on finer resolution data are needed. Using actual hourly electric power consumption data from the business districts of Tokyo, we calculated the sensitivity of electric power consumption using multiple regression analysis. The sensitivities appear from 07:00 to 23:00 local standard time (LST) during weekdays during both winter and summer, mainly from 09:00 to 17:00 LST. The sensitivities to air temperature during winter are approximately 0.7–1.1 (W/floor-m²)/°C on an average and those during summer are approximately 1.1–1.4 on an average; the sensitivities to air humidity are approximately 0.6–0.9 on an average. It was found that the sensitivities to air temperature are caused due to heating during winter and cooling during summer; further, the sensitivities to air humidity were caused by dehumidification not for conditioning the air humidity of the room but for the condensation around the air-conditioner's coils with cooling during summer.     

某下送风多功能厅气流组织及节能性的实测与分析

实测了采用下送风空调方式的某多功能厅的温度场和速度场。获得了夏季三种工况下的温度、速度分布及其随时间的变化。评价了该空调房间的节能性以及舒适状况。结果表明,在一定送风量和送风参数下能够满足舒适性要求,且具有较明显的节能效果,通风效率为1.7~3.2。     

蜂窝蓄热体温度特性数学解析

基于蜂窝蓄热体气固传热精确解，研究蓄热体温度变化和切换周期设计方法，忽略沿气流流动方向的固体导热影响，建立了周期传热数学模型，并求出了气固温度分布精确解。和数值计算相比，半解析解可信，按炉内低氧稳定燃烧和蓄热体低温端不结业的要求，可进行切换周期优化设计，从而为低氧弥散燃烧设计和操控优化提供一种高效、经济、准确的解析研究方法。     

江水源热泵工程设计中江水水温与气温的关系研究

在长江上游地区的江水源热泵工程设计中,江水温度的全年变化情况是确定系统方案的重要依据之一。对长江上游水温的特点及影响因素进行了分析。以重庆世纪会江水源热泵工程、长江上游水文水资源勘测局和重庆气象站的监测数据为依据,对江水水温和气温之间的关联关系进行了多项式和非线性拟合,结果表明Boltzmann拟合模型的计算值与实测值的吻合度较好;采用长江寸滩站的实测水温对Boltzmann拟合模型进行了校验,结果表明该模型可以较好地预测不同气温情况下的江水水温,可以在重庆主城区长江河段的水源热泵工程设计中应用。     

Methodology to estimate the threshold in-cylinder temperature for self-ignition of fuel during cold start of Diesel engines

Cold startability of automotive direct injection (DI) Diesel engines is frequently one of the negative features when these are compared to their closest competitor, the gasoline engine. This situation worsens with the current design trends (engine downsizing) and the emerging new Diesel combustion concepts, such as HCCI, PCCI, etc., which require low compression ratio engines. To mitigate this difficulty, pre-heating systems (glow plugs, air heating, etc.) are frequently used and their technologies have been continuously developed. For the optimum design of these systems, the determination of the threshold temperature that the gas should have in the cylinder in order to provoke the self-ignition of the fuel injected during cold starting is crucial. In this paper, a novel methodology for estimating the threshold temperature is presented. In this methodology, experimental and computational procedures are adequately combined to get a good compromise between accuracy and effort. The measurements have been used as input data and boundary conditions in 3D and 0D calculations in order to obtain the thermodynamic conditions of the gas in the cylinder during cold starting. The results obtained from the study of two engine configurations -low and high compression ratio- indicate that the threshold in-cylinder temperature is a single temperature of about 415 °C.     

Recombination of hydrogen-air catalyzed by Pt/C catalyst in a confined vessel at ambient temperature

Most of the previous studies have investigated the detonation and combustion characteristics of hydrogen and air mixtures, but the change process of hydrogen-air recombination reaction at ambient temperature is unclear. In this study, the variation of temperature and hydrogen conversion during the H₂-air mixture reaction catalyzed by Pt/C catalyst was examined. Experiments were carried out in a small-scale cylindrical vessel to investigate the effects of hydrogen volume fraction, catalyst mass, and inlet gas flow rate on the reaction process. The results revealed that the reaction temperature climbed as the hydrogen volume fraction increased, with a peak value achieved when the hydrogen volume fraction reached 35 vol%, and subsequently reduced as the hydrogen volume fraction increased further. The increase of the inlet gas flow rate also promoted the growth of reaction temperature. However, there was no significant linear relationship between the rise of catalyst mass and the change of reaction temperature.