Construction and realization of the knowledge base and inference engine of an IDSS model for air-conditioning cooling/heating sources selection

The knowledge representation mode and inference control strategy were analyzed according to the specialties of air-conditioning cooling/heating sources selection. The constructing idea and working procedure for knowledge base and inference engine were proposed while the realization technique of the C language was discussed. An intelligent decision support system (IDSS) model based on such knowledge representation and inference mechanism was developed by domain engineers. The model was verified to have a small kernel and powerful capability in list processing and data driving, which was successfully used in the design of a cooling/heating sources system for a large-sized office building.

Effect of thermal storage performance of concrete radiant cooling room on indoor temperature

A building model with radiant cooling system was established and the cooling load, indoor temperature, surface temperature of the wails and other parameters in non-cooling and radiant cooling room were calculated by TRNSYS. The comparative analysis of the characteristics of attenuation and delay proves that the operation of radiant cooling system increases the degree of temperature attenuation of the room and reduces the inner surface temperature of the wall significantly, but has little effect on the attenuation coefficient and delay time of wall heat transfer. The simulation results also show that the inner surface temperature of the walls in the radiant cooling room is much lower than that in non-cooling room in the day with the maximum cooling load, which reduces the indoor operation temperature largely, and improves the thermal comfort. Finally, according to the analysis of indoor temperature of the rooms with different operation schedules of cooling system, it can be derived that the indoor mean temperature changes with the working time of radiant cooling system, and the operation schedule can be adjusted in practice according to the actual indoor temperature to achieve the integration of energy efficiency and thermal comfort.

Analysis of Solar Direct-Driven Organic Rankine Cycle Powered Vapor Compression Cooling System Combined with Electric Motor for Office Building Air-Conditioning

Solar energy powered organic Rankine cycle vapor compression cycle(ORC-VCC)is a good alternative to convert solar heat into a cooling effect.In this study,an ORC-VCC system driven by solar energy combined with electric motor is proposed to ensure smooth operation under the conditions that solar radiation is unstable and discontinuous,and an office building located in Guangzhou,China is selected as a case study.The results show that beam solar radiation and generation temperature have considerable effects on the system performance.There is an optimal generation temperature at which the system achieves optimum performance.Also,as a key indicator,the cooling power per square meter collector should be considered in the hybrid solar cooling system in design process.Compared to the vapor compression cooling system,the hybrid cooling system can save almost 68.23%of electricity consumption.

Performance analysis of thermal storage unit with possible nano enhanced phase change material in building cooling applications

The heat transfer performance of the phase change materials used in free cooling and air conditioning applications is low,due to the poor thermal conductivity of the materials.The recent phenomenal advancement in nano technology provides an opportunity for an appreciable enhancement in the thermal conductivity of the phase change materials.In order to explore the possibilities of using nano technology for various applications,a detailed parametric study is carried out,to analyse the heat transfer enhancement potential with the thermal conductivity of the conventional phase change materials and nano enhanced phase change materials under various flow conditions of the heat transfer fluid.Initially,the theoretical equation,used to determine the time for outward cylindrical solidification of the phase change material,is validated with the experimental results.It is inferred from the parametric studies,that for paraffinic phase change materials with air as the heat transfer fluid,the first step should be to increase the heat transfer coefficient to the maximum extent,before making any attempt to increase the thermal conductivity of the phase change materials,with the addition of nano particles.When water is used as the phase change material,the addition of nano particles is recommended to achieve better heat transfer,when a liquid is used as the heat transfer fluid.

Energy Storage System for Solar Thermal Air Conditioning Combined with Ejector Cooling System

A system of energy storage for solar thermal air conditioning combined with ejector cooling system for residential is determined in this paper. The purpose of this study is to design the energy storage system for heating the water in a storage tank to reach the required temperature for exchanging heat with the refrigerant of cooling system. The design from calculation of thermal energy storage system that proper with the solar flat plate collector area results are 70 m2, and the hot water temperature is over than 80 ℃. A cooling system is selected for refrigerant of R141b from the solar air conditioning system of 10.5 kW, and the energy source is solar thermal energy from the collector that there is an efficiency of 0.46 approximately. This storage system for the electric solar cooling system can be reduced the problem of the intermittent of energy source with the constant generating temperature to run the cooling system continuously.

Heat transfer and parametric studies of an encapsulated phase change material based cool thermal energy storage system

This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES) system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.

Cool storage time of phase change wallboard room in summer

More and more attention was paid to phase change energy storage in air conditioning domain and construction energy conservation,and became the focus of the international research. Through the test and analysis of the parameters of the indoor thermal property in phase change wallboard room and ordinary room,the effects of using phase change wallboards on indoor temperature in summer and air conditioning are obtained. The combination of construct enclosure and phase change materials can stabilize indoor temperature,improve indoor thermal comfort,reduce the frequency of the operation of air conditioning facility,cut the initial investment and operation expense,and meanwhile play an practical role in "the power balancing between the peak period and the valley period" policy. Through the experiment and the test of the effects exerted by phase change wallboard room and ordinary room on the indoor thermal environment,it is obtained that the phase change wallboard can reduce the fluctuation range of indoor temperature and the heat flow from the outside into indoor environment in summer. According to the study,it is found that the effect of cool-storing for 5 h is obvious. Through the analysis of the phase change wallboard without air conditioning in daytime,it is obtained that the frequency of the operation of air conditioning in phase change wallboard room is smaller than that in the ordinary room,which can prolong the lifetime of the facility and reduce operation expense.

Absolute dielectronic recombination rate coefficients of highly charged ions at the storage ring CSRm and CSRe

Dielectronic recombination(DR)is one of the dominant electron-ion recombination mechanisms for most highly charged ions(HCIs)in cosmic plasmas,and thus,it determines the charge state distribution and ionization balance therein.To reliably interpret spectra from cosmic sources and model the astrophysical plasmas,precise DR rate coefficients are required to build up an accurate understanding of the ionization balance of the sources.The main cooler storage ring(CSRm)and the experimental cooler storage ring(CSRe)at the Heavy-Ion Research Facility in Lanzhou(HIRFL)are both equipped with electron cooling devices,which provide an excellent experimental platform for electron-ion collision studies for HCIs.Here,the status of the DR experiments at the HIRFL-CSR is outlined,and the DR measurements with Na-like Kr25^(+)ions at the CSRm and CSRe are taken as examples.In addition,the plasma recombination rate coefficients for Ar12^(+),14^(+),Ca14^(+),16^(+),17^(+),Ni19^(+),and Kr25^(+)ions obtained at the HIRFL-CSR are provided.All the data presented in this paper are openly available at https://doi.org/10.57760/sciencedb.j00113.00092.

Seasonal coolth storage system for residential buildings in Australia

Night sky cooling is explored as an alternative to the conventional cooling technologies using fossil fuels. The night sky cooling method is based on the long wave radiation of unglazed collectors to the sky at night. An evaluation of the night sky cooling system is present for a residential building in three cities of Australia, namely Alice Springs, Darwin and Melbourne. The system comprises an unglazed flat plate solar collector integrated with borehole storage. It uses night sky radiation to reduce the temperature of the ground near to the boreholes. The system was simulated with TRNSYS, a transient simulation program. The simulation results for adequately sized systems show that night sky radiation is able to reduce the coolth storage borehole temperature and the proposed system is able to meet the cooling load of the residential building simulated in three locations. Borchole lengths of 270, 318 and 106 m are required for coolth storage with 90, 260 and 14 m2 collector area for heat rejection in Alice Springs, Darwin and Melbourne, respectively. At the 20th simulation year, the proposed system is able to achieve a system cooling coefficient of performance of 2.2 in Alice Springs, and 2.8 in Darwin and Melbourne.

Experimental Study of Air Conditioning Unit of Evaporative Cooling Assisted Mechanical Refrigeration

The evaporative cooling,which assists the refrigeration machinery air-conditioning systems test-rig,has been designed.Its structure and working principle were described,and the performance test was conducted and analyzed.The test shows that making full use of the evaporative cooling "free cooling" in Spring and Autumn seasons can fully meet the requirements of air-conditioned comfort through the switch of the function in different seasons.Taking into account the evaporative cooling fan and pump energy consumption,compared with the traditional mechanical refrigeration system,more than 80 percent of energy can be saved,and the energy efficiency ratio of the Unit(EER)is as high as 7.63.Using the two stages of indirect evaporative cooling to pre-cool the new wind in summer,under the conditions of the same air supply temperature requirements,0.83 kg/s chilled water saved can be equivalent to the traditional mechanical refrigeration system,and when the new wind ratio up to 50 percent,more than 10 percent load was reduced in mechanical refrigeration system.The overall EER increased about 35 percent.

Experimental investigation of evaporative cooling systems for agricultural storage and livestock air-conditioning in Pakistan

Evaporative cooling(EC)is an ancient technique that is usually suitable for hot and dry climatic conditions due to the potential of water vapor evaporation.In this study,three kinds of evaporative cooling systems such as direct EC(DEC),indirect EC(IEC),and Maisotsenko cycle EC(MEC)were locally developed at lab-scale.The performance of the systems was evaluated and compared for agricultural storage and livestock air-conditioning application in Pakistan.The experiments were performed for climatic conditions of Multan city(Pakistan)and the data were collected for hourly and daily basis.According to the results,it was observed that the DEC system has the ability to reduce the temperature of ambient air to an average of 8.5℃.Whilst IEC and MEC systems were able to drop the temperature of ambient air to an average of 6.8℃and 8.9℃,respectively.As per the results,the DEC system remained behind to provide desired conditions for livestock and agricultural product storage applications due to excessive humidity.On the other hand,the IEC and MEC systems can achieve the desired conditions for livestock application,but could not provide feasible conditions for various fruits and vegetable storage.The study concludes that hybrid EC systems can be developed to provide desired conditions for a wide range of applications under varying climatic conditions.

Simulation of District Cooling Plant and Efficient Energy Air Cooled Condensers (Part I)

In hot arid countries with severe weather, the summer air conditioning systems consume much electrical power at peak period. Shifting the loads peak to off-peak period with thermal storage is recommended. Model A of residential buildings and Model B of schools and hospitals were used to estimate the daily cooling load profile in Makkah, Saudi Arabia at latitude of 21.42°N and longitude of 39.83°E. Model A was constructed from common materials, but Model B as Model A with 5 - 8 cm thermal insulation and double layers glass windows. The average data of Makkah weather through 2010, 2011 and 2012 were used to calculate the cooling load profile and performance of air conditioning systems. The maximum cooling load was calculated at 15:00 o’clock for a main floor building to a 40-floor of residential building and to 5 floors of schools. A district cooling plant of 180,000 Refrigeration Ton was suggested to serve the Gabal Al Sharashf area in the central zone of Makkah. A thermal storage system to store the excess cooling capacity was used. Air cooled condensers were used in the analysis of chiller refrigeration cycle. The operating cost was mainly a function of electrical energy consumption. Fixed electricity tariff was 0.04 $/kWh for electromechanical counter, and 0.027, 0.04, 0.069 $/kWh for shifting loads peak for the smart digital counter. The results showed that the daily savings in consumed power are 8.27% in spring, 6.86% in summer, 8.81% in autumn, and 14.55% in winter. Also, the daily savings in electricity bills are 12.26% in spring, 16.66% in summer, 12.84% in autumn, and 14.55% in winter. The obtained maximum saving in consumed power is 14.5% and the daily saving in electricity bills is 43% in summer when the loads peak is completely shifted to off-peak period.

Thermal properties in phase change wallboard room based on air conditioning cold storage

By comparing the thermal performance parameters of an ordinary wall room with a phase change wall (PCW) room,the effect of phase change wallboard on the fluctuation of temperature in air-conditioning room in summer was studied. And PCW room and an ordinary wall room,which are cooled by air-conditioner,were built up. Differential scanning calorimetry (DSC) was used to test the temperature field and heat flow fluctuation in these rooms. Through analyzing the data tested,it is found that the mean temperature of PCW is lower than that of ordinary wall room by 1-2 ℃,and PCW can lower the heat flow by 4.6 W/m2. Combining phase change material to building envelope can lower the indoor temperature,make the room thermal comfortable,and cut down the turn-on-and-off frequency of air-conditioner,the primary investment and operating costs. It alleviates urgent need of the electric power. Building envelope which contains phase change wallboard can improve the indoor thermal environment,and decrease energy consumption in buildings. Phase change wallboard can make impressive effect on energy efficiency of buildings.

Intelligent Scheduling for High Bulilding Multi-type Cooling System

In modern giant buildings,in order to improve energy utilization efficiency, cooling systems have developed from conventional chillers alone to smart energy net which includes chillers,ice storage,ground-source heat pump,combined cooling heating and power( CCHP) and so on. The reasonable distribution of load is the key to guarantee such system in economical operation.Based on typical multi-type cooling system,economic models of different devices are presented and real-time intelligent economic scheduling with the approach of mixed integer programming is carried out. This algorithm has been applied in a certain building of Shanghai and results of simulation show that it is able to provide guidance on intelligent economic scheduling for multi-type cooling system.

Design of Heat Storage for a Solar Concentrator Driving an Absorption Chiller

The feasibility of employing stand-alone solar energy systems to meet demand-side loads depends strongly on providing appropriate solar energy storage. The present paper presents an efficient and economical, underground, thermal storage design to store hot water at a temperature of around 180?C required for running a double effect absorption chiller to cool a zero-energy-house in a desert environment. The performance of the design is evaluated employing a specially developed efficient mathematical model, for simulating the steady state radiation, convection and conduction processes occurring within the storage unit. The model is presented and analyzed, and employed to investigate the effects of various design parameters on storage efficiency. It is demonstrated that high storage efficiency may be reached, providing that appropriate insulation materials are used. It is also revealed that the soil conductivity has little effect on storage efficiency.

粮仓能源桩系统绿色储粮技术应用研究

简化粮食入库后全周期控温供冷储粮流程,提出满仓主动降温与夏季粮仓热平衡2种供冷方案。通过理论公式计算2种方案下的供冷量需求,并利用有限元模拟软件计算得出能源桩换热量,由此设计可满足上部粮仓供冷需求的能源桩运行方案。结果表明:在1万t储粮规模下,粮仓能源桩储粮技术可满足2种供冷方案下的能源需求,对比谷物冷却机与地源热泵储粮,其初期投入成本更低;对比空调储粮,其初期投入成本增加,但能源桩储粮技术可利用绿色清洁能源,储粮能耗最低。

新型迷你通道-相变热沉实验研究

电子元件的集成化、微型化等特点加剧了芯片的热问题,基于相变材料的被动式冷却技术已无法满足功率波动的高功率电子设备的需求。本文将相变技术与主动冷却技术相结合,提出了一种用于风冷散热的新型迷你通道-相变热沉结构。该结构改善了相变材料导热性能差的问题,也解决了相变材料熔化后泄漏的问题。通过实验测试了不同热流密度、不同风速对其热控性能的影响,总结了热沉的蓄放热特性,并与未填充相变材料热沉的热控性能进行了对比。实验中热流密度变化范围为1.81~3.47 W/cm^(2),风速变化范围为0~4 m/s。研究表明:热流密度的增大和风速的降低均会导致热沉温控时间的缩短。2 m/s风速足以满足热流密度小于2.91 W/cm^(2)的芯片散热需求,4 m/s风速可以在热流密度为3.47 W/cm^(2)的情况下将热沉底面温度维持在70℃。与未填充相变材料热沉相比,本研究提出的热沉可以起到延长温控时长,降低稳态温度的作用。此外,风扇的开启可以有效缩短热沉的冷却时间,对于间歇性工作的电子设备具有重要的应用意义。研究结果可为迷你通道-相变热沉在实践中的应用提供参考依据。

基于TRNSYS的主动式建筑相变蓄冷空调系统模拟

以夏热冬冷地区的办公建筑为例,利用瞬态系统仿真程序(transient system simulation program, TRNSYS)构建主动式相变蓄能地板模块,建立了主动式相变蓄能地板空调系统和常规风机盘管加新风空调系统的仿真模型,对其节能性和经济性进行模拟计算.以典型日和供冷季晚间蓄冷运行工况为条件,研究冷冻水温对主动式相变蓄能地板的蓄释能特性、室温波动与热泵制冷系数的影响.结果表明:夜间相变蓄冷工况下,在满足每平方米冷负荷为74.78 W情况下,9℃为最佳供水水温;采取晚间低电价时段间歇运行蓄冷热泵的方案,能够有效提高热泵运行时的制冷系数,并降低运行费用;主动式相变蓄能地板空调系统供冷季的能耗相比于常规风机盘管加新风空调系统减少30.5%,运行费用减少44.24%,夏季制冷综合能效比达到了2.38.

基于太阳能吸附制冷的载/蓄冷充填降温系统性能分析

含冰粒的载/蓄冷充填降温是解决深井热害问题的有效方式,但其制冰能耗大、系统运行费用较高。为此,研发了基于太阳能吸附制冷的矿井载/蓄冷充填降温系统(Mine Cold Load/Storage Backfill Cooling System Based on Solar Adsorption Refrigeration),该系统由地面太阳能集热子系统、吸附制冷子系统和地下输冰子系统组成。通过建立子系统的数学模型和地面系统的TRNSYS模型,分别分析甲醇解吸量、吸附制冷量和吸附制冰量在不同太阳能辐射强度、不同季节和不同地区影响下的变化规律,进而得出太阳辐射强度和太阳辐射连续性是造成制冰量差异的主要原因。选取太阳辐射强度和太阳连续性较优的淮南、南宁两区域进行系统制冰能效分析,与传统蒸汽压缩式制冷系统相比,该系统的吸附制冷子系统平均节能效率达到64.71%。研究结果反映出,太阳能吸附制冷与载/蓄冷充填降温相结合的新型矿井降温系统的研发,对于高效解决矿井热害问题有所裨益。

食用油罐内冷媒管降温模拟试验与优化

为缓解食用油在储藏过程中出现的热分层现象,设计内置冷媒管的食用油储罐,并通过调整冷媒流动方式、冷媒流量和冷媒温度等对储油进行降温对比试验。结果表明:采用上供式和下供式降温均可在储油温度整体下降的同时有效缩小上下层温差(1.93、3.67℃),且与自然降温(6.79℃)相比,热分层现象得到明显改善。采用下供式降温的效率最高,较上供式提高了约20%,且下层油温较上供式低约1.9℃。基于Ansys(Fluent)商用计算流体动力学软件平台,通过数值模拟进一步研究了采用下供式的冷媒流量对下层油温的影响。结果显示下供式降温可有效阻隔外部传热,而下层温度变化集中在低温区域,对远离入口侧区域的影响并不明显。