Modelling and simulation of an absorption solar cooling system for Cyprus

In this paper a modelling and simulation of an absorption solar cooling system is presented. The system is modelled with the TRNSYS simulation program and the typical meteorological year file containing the weather parameters of Nicosia, Cyprus. Initially a system optimisation is carried out in order to select the appropriate type of collector, the optimum size of storage tank, the optimum collector slope and area, and the optimum thermostat setting of the auxiliary boiler. The final optimised system consists of a 15-m² compound parabolic collector tilted 30° from the horizontal and a 600-l hot water storage tank. The collector area is determined by performing the life cycle analysis of the system. The optimum solar system selected gives life cycle savings of C£1376 when a nonsubsidized fuel cost is considered. The system operates with maximum performance when the auxiliary boiler thermostat is set at 87°C. The system long-term integrated performance shows that 84,240 MJ required for cooling and 41,263 MJ for hot water production are supplied with solar energy.     

太阳能地面采暖系统蓄热水箱容积分析

通过分析太阳能采暖系统所需蓄热鼍与建筑热负荷、太阳能集热量日变化规律之间的关系,得出太阳能采暖系统所需蓄热水箱容积的理论算式.根据拉萨、银川、西宁、西安等地的太阳辐射强度及建筑热负荷的日变化规律,模拟得出系统所需蓄热量变化规律;并对各种蓄热温差下对应的蓄热水箱容积进行了模拟分析,结果表明:太阳能采暖系统所需蓄热量随太阳集热器的集热量与建筑热负荷之间的差值增大而增加;蓄热水箱容积随蓄热温差增大而减小,当蓄热水温达到80℃时,在各种地面采暖系统取水温度下,单位集热器面积所需蓄热水箱容积趋于相等.     

带饮水机的多功能电冰箱设计

在传统电冰箱的基础上,另独立设置2个保温箱贮存冷热饮用水。冷水制取是在冷水箱中设置蒸发器,将冷水箱中的水制冷。热水制取是在热水箱中设置逆流套管式冷凝器,利用制冷系统的排热量将饮水机中的水加热到一定温度,如温度不够则再通过电加热器,可将饮用水加热至沸腾,冷凝管通热水箱后可采用风冷式和水冷却两种方式相结合。根据设计和理论计算,多功能电冰箱的冷凝器可将饮用水加热到65℃左右,再用电加热器,可将饮用水加热至沸腾,比市场上纯粹用电加热的饮水机可节电22.31W;利用制冷系统将冷水箱中的水制冷,每产生4℃冷饮用水2L比市场上一般的压缩式制冷饮水机可节约大约2.3×105J的能量。     

Analysis of the impact of heat-to-power ratio for a SOFC-based mCHP system for residential application under different climate regions in Europe

In this paper, the ability of a micro combined heat and power (mCHP) system to cover the heat and electricity demand of a single-family residence is investigated. A solid oxide fuel cell based mCHP system coupled with a hot water storage tank is analyzed. The energy profiles of single-family households in different European countries are evaluated. The range of Heat-to-Power Ratio for the SOFC-based mCHP System of 0.5–1.5 shows good agreement with the hot water, space heating and electricity demand during the warm seasons across Europe. This suggests that the fuel cell system should be sized according to the summer energy demand. The winter energy demand shows a Heat-to-Power Ratio which cannot be covered by the mCHP unit alone. To ensure that the mCHP system meets both the thermal and electrical energy demand over the entire year, an auxiliary boiler and a hot water storage tank need to be coupled with the mCHP unit. It is further noted that the size of the auxiliary boiler should match the larger winter space heating demand. In contrast, the hot water tank volume should be sized according to the warm season space heating requirement, when space heating is not required but electricity and hot water are still in demand. This maximizes the running time of the fuel cell, and thus the economic and environmental benefit of the system, without wasting produced heat.     

84MW大型层燃水火管热水锅炉的开发

通过对84MW大型层燃水火管热水锅炉的开发,不仅成功地解决了水火管热水锅炉进一步大型化的各项难题,而且也为当前市场上29～70MW水火管锅炉产品结构和性能的进一步完善与提高提供了有益的参考。     

太阳能空调综合系统在住宅小区应用的可行性探讨

经济性是制约太阳能空调普及推广应用的难题。文中介绍了一种太阳能空调和热水站综合系统方案,即在居民住宅楼的屋顶布置太阳能集热器阵,结合地源水低温热源系统,建设全年供应全体住户生活热水的太阳能热水站,以及夏季和冬季供应顶一、二层住户空调冷、热水的综合系统．提出了一种双效与单效耦合的板壳式溴化锂吸收式制冷机循环方案,白天日照时段采用双效循环运行并进行蓄热,而在其余时段切换为单效循环利用蓄热运行。该方案不仅效率高、而且其单位体积蓄能罐的蓄能密度极大,可实现无需用辅助能源而完全靠太阳能进行昼夜空调。由于综合利用系统中集热器的投资费用被所有热水用户分摊,空调用户的投资可很快从节省的电费中得到回收。     

Design and transient-based analysis of a power to hydrogen (P2H2) system for an off-grid zero energy building with hydrogen energy storage

In this study, zero energy building (ZEB) with four occupants in the capital and most populated city of Iran as one of the biggest greenhouse gas producers is simulated and designed to reduce Iran's greenhouse emissions. Due to the benefits of hydrogen energy and its usages, it is used as the primary energy storage of this building. Also, the thermal comfort of occupants is evaluated using the Fanger model, and domestic hot water consumption is supplied. Using hydrogen energy as energy storage of an off-grid zero energy building in Iran by considering occupant thermal comfort using the fanger model has been presented for the first time in this study. The contribution of electrolyzer and fuel cell in supplying domestic hot water is shown. For this simulation, Trnsys software is used. Using Trnsys software, the transient performance of mentioned ZEB is evaluated in a year. PV panels are used for supplying electricity consumption of the building. Excess produced electricity is converted to hydrogen and stored in the hydrogen tank when a lack of sunrays exists and electricity is required. An evacuated tube solar collector is used to produce hot water. The produced hot water will be stored in the hot water tank. For supplying the cooling load, hot water fired water-cooled absorption chiller is used. Also, a fan coil with hot water circulation and humidifier are used for heating and humidifying the building. Domestic hot water consumption of the occupants is supplied using stored hot water and rejected heat of fuel cell and the electrolyzer. The thermal comfort of occupants is evaluated using the Fanger model with MATLAB software. Results show that using 64 m² PV panel power consumption of the building is supplied without a power outage, and final hydrogen pressure tank will be higher than its initial and building will be zero energy. Required hot water of the building is provided with 75 m² evacuated tube solar collector. The HVAC system of the building provided thermal comfort during a year. The monthly average of occupant predicted mean vote (PMV) is between ?0.4 and 0.4. Their predicted percentage of dissatisfaction (PPD) is lower than 13%. Also, supplied domestic hot water (DHW) always has a temperature of 50 °C, which is a setpoint temperature of DHW. Finally, it can be concluded that using the building's rooftop area can be transformed to ZEB and reduce a significant amount of greenhouse emissions of Iran. Also, it can be concluded that fuel cell rejected heat, unlike electrolyzer, can significantly contribute to supplying domestic hot water requirements. Rejected heat of electrolyzer for heating domestic water can be ignored.     

Yearly simulation of a solar-aided R22-DEGDME absorption heat pump system

The performance of a solar-aided R22-DEGDME absorption heat pump system designed for 100 kW cooling capacity is investigated by a computer simulation using hourly data for Ankara. In summer the generator, and in winter the evaporator, receives solar energy while the remaining demands are met by auxiliary heaters. When needed, these boost the temperature of the water from the storage tank to the minimum allowable levels which are determined as 20°C in winter and over 80°C in summer. The system performance, judged by the fraction of the load supplied from solar energy, is affected mostly from the climate, source temperature limit, collector type and area but little from storage tank size, for the sizes and configuration under investigation. With 400 m² of high efficiency collectors, the solar energy supplied 38% of the demand in winter and 91% of the demand in summer.     

Slag Monitoring System for Combustion Chambers of Steam Boilers

The computer-based boiler performance system presented in this article has been developed to provide a direct and quantitative assessment of furnace and convective surface cleanliness. Temperature, pressure, and flow measurements and gas analysis data are used to perform heat transfer analysis in the boiler furnace and evaporator. Power boiler efficiency is calculated using an indirect method. The on-line calculation of the exit flue gas temperature in a combustion chamber allows for an on-line heat flow rate determination, which is transferred to the boiler evaporator. Based on the energy balance for the boiler evaporator, the superheated steam mass flow rate is calculated taking into the account water flow rate in attemperators. Comparing the calculated and the measured superheated steam mass flow rate, the effectiveness of the combustion chamber water walls is determined in an on-line mode. Soot-blower sequencing can be optimized based on actual cleaning requirements rather than on fixed time cycles contributing to lowering of the medium usage in soot blowers and increasing of the water-wall lifetime.     

太阳能吸收式空调及供热系统的设计和性能

一套太阳能吸收式空调及供热综合系统已在山东省乳山市建成。该系统由热管式真空管集热器、溴化锂吸收式制冷机、储水箱、循环、冷却塔、空调箱、辅助燃油锅炉和自动控制系统等内部分组成,具有夏季制冷、冬季供热和全年提供生活用热水等功能。太阳能集热器总采光面积540m∧2,制冷、供热功率100kW,空调、采暖建筑面积1000m∧2供生活用热水量32m∧3／d。文中着重介绍了系统的设计特点和测试性能。     

几种大容量燃天然气热水锅炉方案的分析比较

文章分别介绍了大容量燃天然气热水锅炉的三种型式,即自然循环热水锅炉、带有自然循环特性的强制循环热水锅炉和强制循环热水锅炉,并针对三种型式各自的设计特点予以比较,最终给出结论.     

Study on a compact silica gel–water adsorption chiller without vacuum valves: Design and experimental study

A compact silica gel–water adsorption chiller without vacuum valves was manufactured and experimentally studied. This chiller contains two adsorption/desorption chambers and one chilled water tank. Each adsorption/desorption chamber consists of one adsorber, one condenser and one evaporator. The chilled water tank is adopted to mitigate the variation of the chilled water outlet temperature. A mass recovery-like process, which is a heat recovery process between the two evaporators, was carried out in this chiller. A novel heat recovery process was also fulfilled after the mass recovery-like process to improve the coefficient of performance (COP). The cooling power and COP were 9.60 kW and 0.49 respectively when the average hot water inlet temperature, cooling water inlet temperature, and chilled water outlet temperature were 82.0, 31.6 and 12.3 °C, respectively.     

Analysis of natural circulation solar water heating systems

This paper presents an analysis of the performance of a solar water heating system with natural thermosyphon circulation between the collector and the storage tank. The analysis is based on the formulation by Ong except that provision for withdrawal of hot water from the tank (for domestic/ industrial use) has been made in the energy balance equation; further in contrast to the use of the finite difference method by Ong, explicit expressions have been obtained. The results of the present analysis (in the absence of withdrawal of hot water from the tank) are seen to be in better agreement with experiments than the corresponding results of Ong, obtained by use of the finite difference method.

Numerical results, corresponding to hot water retrieved from the storage tank, have been presented for two modes of hot water withdrawal viz. the constant flow rate and constant mean storage tank water temperature.     

Parametric Analysis of Solar Heating and Cooling Systems for Residential Applications

Abstract

In this paper, a parametric analysis of two solar heating and cooling systems, one using an absorption heat pump and the other one using an adsorption heat pump, was performed. The systems under investigation were designed to satisfy the energy requirements of a residential building for space heating/cooling purposes and domestic hot water production. The system with the absorption heat pump was analyzed upon varying (i) the solar collectors’ area, (ii) the volume of the hot water storage, (iii) the volume of the cold water tank, and (iv) the climatic conditions. The system with the adsorption heat pump was evaluated upon varying (i) the inlet temperature of hot water supplied to the adsorption heat pump, (ii) the volume of the hot water storage, (iii) the volume of the cold water tank, and (iv) the climatic conditions. The analyses were performed using the dynamic simulation software TRNSYS in terms of primary energy consumption, global carbon dioxide equivalent emissions, and operating costs. The performance of the solar heating and cooling systems was compared with those associated with a conventional system from energy, environmental and economic points of views in order to evaluate the potential benefits.     

燃煤热水锅炉运行安全性探讨

采用大容量燃煤热水锅炉是符合我国国情、改善环境质量的重要举措,势在必行.但是大容量燃煤热水锅炉安全运行是需要十分关注的问题.分析了热水锅炉出现故障的原因和解决办法,并以实例分析说明角管式燃煤热水锅炉不仅很好地解决了热水锅炉运行的安全性问题,而且有利于节约能源和改善燃煤热水锅炉使用地的周边环境.     

A new heat-pipe type solar domestic hot water system

The performance of a new solar hot water system with an integrated heat-pipe is investigated theoretically and experimentally. The new system uses a wickless gravity assisted loop heat-pipe for the heat transfer from the collector–evaporator to the tank through a heat exchanger–condenser. A detailed heat transfer experimental study is performed, focused on the thermal behaviour of the different parts of the system. The results show that the system can reach satisfactory efficiencies which, in combination with manufacturing simplicity, absence of moving parts and good behaviour under freeze conditions, make it an interesting technological solution. Furthermore, a theoretical model for the collector is proposed and comparison with experimental results is performed. This model can be used for the optimisation of the system design.     

关于常压热水锅炉的系统设置和节能

常压热水锅炉在国内已有广泛的应用,但常压热水锅炉房目前尚无权威的设计布置方法,而导致安全事故常有发生。在这种锅炉的布置中必须有通大气管和锅炉热水箱。循环热水泵应设于锅炉的出口。在循环热水泵选型时,其压头应为热用户与锅炉房的高程差及管网阻力之和,回水管路上必须设启闭网和阻力调节阀。常压锅炉的节能特性应视热水管网的构成情况具体分析。这种锅炉大体上用在低层、低参数、小容量的场合较为合适。     

116MW水冷方形分离循环流化床热水锅炉的运行经验

城市燃煤集中供暖对洁净燃烧技术的需求是循环流化床热水锅炉发展的动力。介绍了首台运行的最大容量的116MW循环流化床热水锅炉的运行情况。实践表明：采用水冷方形分离器的116MW循环流化床热水锅炉运行稳定,可用率高,燃烧效率高,满足严格的大气排放标准,密封性好,占地面积小,可以很好地适应城市集中供暖频繁启动和压火的需要。图6表5参6     

燃用玉米芯的循环流化床锅炉热风系统研究与设计

介绍了一种循环流化床锅炉热风系统的设计,该系统的热源为一燃用玉米芯的循环流化床热水锅炉,燃料燃烧产生的热首先产生热水,热水在换热器内与空气换热,然后产生43℃热风.这套系统设计关键为锅炉的燃烧温度选择、灰渣质量平衡以及如何保证热风风温稳定等.为进行这套系统的设计,通过试验研究了玉米芯在流化床内的燃烧特性、灰渣结焦特性以及循环床回料器的回料特性.在试验基础上,设计了这套热风系统,这套热风系统由锅炉、换热器、调节系统、除尘器等组成.首台采用该技术的热风系统已在山东登海先锋种业公司投产.这套系统可作为设计燃用稻壳、秸秆等其他生物质燃料锅炉的参考.     

Simulation of a solar domestic water heating system using a time marching model

This paper presents the modelling and simulation of a solar water heating system using a time marching model. The results of simulations performed on an annual basis for a solar system, constructed and operated in Yugoslavia, which provides domestic hot water for a four-person family are presented. The solar water heater consists of a flat-plate solar collector, a water-storage tank, an electric heater, and a water-mixing device. The mathematical model is used to evaluate the annual variation of the solar fraction with respect to the volume of the storage tank, demand hot water temperature required, difference of this temperature and preset storage tank water temperature, and consumption profile of the domestic hot water demand. The results of this investigation may be used to design a solar collector system, and to operate already designed systems, effectively. The results for a number of designs with different storage tank volumes indicate that the systems with greater volume yield higher solar fraction values. The results additionally indicate that the solar fraction of the system increases with lower hot water demand temperature and higher differences between the mean storage water and the demand temperatures. However, when a larger storage tank volume is used, the solar fraction is less sensitive to a variation of these operation parameters.