冷热组合型超市系统的设计与经济性分析

设计了冷热组合型超市系统,利用CO2跨临界循环对空间夏季供冷和冬季供热,采用R290/CO2复叠式制冷循环对食品冷冻冷藏,同时回收CO2跨临界循环高温气体散发的热量和R290/CO2复叠式制冷循环R290高温循环气体的冷凝热,实现夏季空间供冷、食品制冷的同时供应生活热水,冬季空间供暖、食品制冷的同时供应生活热水,及春秋季节食品制冷同时供应生活热水。并与供冷、供暖、食品制冷和供应生活热水分别进行的常规R404A超市系统的能效相比较,得出冷热组合型超市系统的能耗大大降低,能效明显增加,不仅节约能源,而且保护环境,是很有发展前景的绿色环保系统。     

基于CO2热泵的产消型数据中心能效联动优化

  目的  随着数字经济的发展,数据中心的“规模”将不断扩大,“算力”不断提高,随之带来的“能耗”及“运行成本”也将不断攀升。为实现数据中心余热的有效利用,并实现能效的联动优化,构建了一种基于CO₂热泵的产消型数据中心能源系统。  方法  将数据中心视为产消者,耗电的同时将制冷系统的余热回收,用于住宅供暖。产消型数据中心能源系统采用空气直接冷却、直膨式地埋管冷却和建筑供暖末端冷却三种方式实现数据中心全年的冷却,最大程度利用自然冷却,降低系统电耗。CO₂作为余热回收用热泵的工作介质,能够提高系统紧凑性与环境友好性。  结果  本系统可有效削减冷负荷,进而在平均占用率较低时,实现制冷电耗的降低。当平均占用率为0.6时,与常规房间级风冷空调机组相比,本系统可降低全年冷负荷108 MWh,节约电耗制冷电耗167 MWh,为建筑供热290 MWh,获得年收益4.23万元。  结论  本系统可实现数据中心余热回收用于建筑供暖,实现了数据中心非供暖期余热的有效利用。并通过地源热泵系统实现了数据中心余热与建筑热负荷的协调,为产消型数据中心的能效联动优化提供了借鉴。     

固体吸附式冷管循环工作过程的动态模拟与分析

针对余热驱动吸附式冷管单元(直径16mm,总长1020mm)制冷循环过程的变压吸/脱附特性,采用线性驱动力(LDF)模型,建立了动态的传热传质数学模型。对吸附式冷管的主要部件——吸附器和冷凝/蒸发器在加热解吸和冷却吸附不同阶段的工作过程,分别建立了耦合的动态方程。对所提出的模型进行分析和合理简化后,利用数值方法对模型进行了求解,获得了冷管单元吸附器、冷凝/蒸发器的循环工作参数的动态变化规律,计算结果与实验结果较好地吻合。为吸附式冷管单元及其组合式制冷系统进一步的优化设计和实用化的改进研究提供了重要参考。     

Exergy optimization of a novel hydrogen production plant with fuel cell,heat recovery,and MED using NSGAII genetic algorithm

In the current research, 4E analysis and multi-criteria optimization are applied to the poly generation unit for power, heating, refrigeration, and freshwater generation. This system consists of a solid oxide fuel cell (SOFC), multi-effect thermal vapor desalination (MED-TVC), an organic system with ejector refrigeration (OSER), a heat recovery steam generator (HRSG) and a domestic hot water generator. The mathematical simulation is applied to assess the performance of the plant at design conditions and the genetic algorithm finds the optimum operating point with two different scenarios. Parametric analysis and multi-objective optimization are carried out. Findings represent that the developed plant can provide 257.65 kW power, 12.13 kW, 7.44 kW cooling and heating load, and 0.04 kg/s freshwater with a total cost rate of 10.62 $/h. In this case, the plant energy and exergy efficiency is 73.9% and 71.35% respectively. The results of multi-objective optimization show that these values can be improved to 79% and 73.9% respectively. In addition, the plant cost can be reached to 10.07 $/h in this condition.     

The Performance of the First Pilot Thermoacoustic Refrigerator

The simple goal of this work is constructing a cheap, demonstrative model of a thermoacoustic refrigerator. To this end, the author succeeded in designing, building and testing the first pilot thermoacoustic refrigeration in Jordan basing on the theory of using sound waves as a coolant. The pilot thermoacoustic refrigerator was built from inexpensive and readily available parts in Mutah University, Jordan. The thermoacoustic refrigerator was operated for several hours. Consequentially, this experiment proved that thermoacoustic refrigerators were technically possible. Additionally, this experiment did yield some findings regarding the efficiency of thermoacoustic refrigeration. On other hand, solid flow CFD software was used to simulate the performance of thermoacoustic refrigerator especially the temperature and velocity inside the refrigerator. In general, very good agreement was deduced.     

Cooling Device Using the Natural Convection, Phase Change of Substance and Capillary Effect

Paper deals about testing of device with gravity assisted heat pipes and about researching of wick heat pipes used to effective heat transfers from power switches of energy converter. At first, to simulate ambient condition was designed thermostatic chamber where was monitoring temperature course on main parts of cooling device （energy converter, air cooler and heat pipes） at various position of cooling device. It was found, if the cooling device is in tilt position the cooling performance is better. But if the tilt angel of gravity assisted heat pipe is higher the heat transfer is lower. From reason improve heat transfer cooling device at tilt angle are manufactured heat pipes with the sintered, mesh screen and grooved capillary structures and tested their thermal performance at vertical and tilt angel 45~ position by calorimetric method. Article describes manufacturing process and thermal performance measuring method of wick heat pipes. This experiment testify that the wick heat pipe is able operate at tilt angle position than gravity assisted heat pipe and application of wick heat pipes into cooling device will improve his cooling performance.     

Gasification of Bio-waste and Biomass Products through Exposure to HD and LD Supercritical Water

Biomass as a sustainable and renewable energy source is starting to gain momentum, especially as more economical energy extraction methods prevail. SCWBG （supercritical water biomass gasification） is one of the more promising methods to extract energy from biomass in a gaseous form due to its lower temperature and simpler setup. In this work, two biomass and two bio-waste samples are gasified in SCW （supercritical water） under two temperatures （hence water densities）. As temperature increases and water density decreases, combustible gas yields tend to increase due to changes in reaction pathways and reaction rates. An analytical comparison is also made between the four different types of biomass in terms of the combustible gases produced and hence the energy value. As a result of this analysis beet skin produces the most methane and corn silage yields the most hydrogen. The two bio-waste samples （straw and beet skin） are found to have the highest HHV （higher heating values）.     

Effects of unequal finite piston speeds on the optimal performances of endoreversible Carnot refrigeration and heat pump cycles

The performances of endoreversible Carnot refrigeration and heat pump cycles with loss of heat resistance and finite piston speeds are analysed and optimized by using the combination of finite time thermodynamics, finite speed thermodynamics and direct method. The unequal finite piston speed model on four branches is adopted. Expressions of cooling load of endoreversible Carnot refrigeration cycle and of heating load of endoreversible Carnot heat pump cycle are derived with a fixed cycle period and unequal finite piston speeds on the four branches. Numerical examples show that there exist optimal expansion ratios, which lead to maximum cooling load and maximum heating load for the fixed coefficient of performance (COP), respectively. The maximum cooling load, maximum heating load, optimal ratios of finite piston speeds and optimal hot- and cold-side working fluid temperatures versus COP characteristics for the endoreversible Carnot refrigeration and heat pump cycles are obtained. Moreover, the effects of design parameters on the performances of the two cycles are discussed.     

Direction Dependence of Savings on Cooling and Heating Loads by Energy Efficient Windows

The energy saving performance of energy efficient windows has strong dependence on window direction. Transmitted insolation level definitely affected the cooling and heating load. Simple simulation on the decrement of cooling load and the increment of heating load of a shading window compared with those of a transparent window show the prospect of energy saving effect clearly.From southeastward to southwestward, shading window even enlarges total heating and cooling loads when the thermal transmission is the same. However, if the shading coefficient of window is switched between summer and winter, total cooling and heating load can be reduced. This result clarifies the importance of ＂smart window＂.     

Modelling of Transduction Heaters Using Transformer Equivalent Circuit and Finite Element Analysis

This paper presents the modelling of transduction heaters using the TEC （transformer equivalent circuit） model and FEA （finite element analysis）. Each model was used to simulate a set oftransduction heating experiments and the results compared. Analysis of the TEC calculated results suggested modification of three parameters： the secondary resistance, the core tube eddy current resistance and the core tube magnetizing reactance. The improved TEC model was then used to design, build and test a 6 kW transduction heater. The measured results are compared with calculated results from the TEC and FEA models. The TEC model accurately predicts the performance of the heater.     

Thermoeconomic assessment of a multi-engine,multi-heat-pump CCHP (combined cooling,heating and power generation) system – A case study

Design and operation of complex systems for combined cooling, heating and power generation (CCHP) are always a matter of matching performance and demand characteristics of a thermal system set to supply electrical, cooling and heating loads, according to specific usage demands. Equipment selection and operation require the characterization of power, heating and cooling load demands, and their time variation during years, seasons, months and even hours or minutes. The paper aims at utilizing a general model for complex CCHP systems. The proposed model is based on the general theory of exergy cost and structural coefficients of internal links. A general model is presented, and a simple hypothetical cogeneration case is studied. The system operates with two heat engines, with waste heat recovery driving a chiller, in order to meet electrical power and refrigeration loads.     

Eco Insulation Materials： Reduction of Cooling Loads of a House Made of Breeze Block or Laterite in a Dry Tropical Climate

In this paper, we study the influence ofeco materials for roof insulation and fiber-reinforced mortar coatings on cooling loads of a home in dry tropical climate. The walls of the house are made of cinderblock or laterite and the insulating material of a roof panel is made with lime （24%）, cement （6%）, water （50%） of vegetable fibers hibiscus sabdariffa （16%）, tree widespread in Burkina Faso and sugar cane bagasse （4%）. This panel roof insulation and the fiber-reinforced mortar were characterized at the Laboratory of Physics and Chemistry of the environment by the hot plate method. The building is modeled in TRNSYS using climate data from the city of Ouagadougou. The results obtained show that in the warmer months of the year, that is to say in March and April, the relative differences between heat gains the configurations ＂breeze block-coating mortar and roof not insulated＂ and ＂laterite- fiber-reinforced mortar coating and insulated roof＇ vary between 15.6% and 16.8%. The configuration ＂laterite-fiber-reinforced mortar coating and insulated roof allows a reduction of annual heat gains of 15.5% compared to the configuration ＂breeze block-coating mortar and roof not insulated＂.     

Fundamental Study of a Loop-Tube-Type Thermoacoustic Heating System

This paper proposes a loop-tube type thermoacoustic heating system without any moving parts based on the thermoacoustic effect. In a thermoacoustic heating system, the supplied sound is converted to heat and the heating point is heated. A thermoacoustic heating system differs from a thermoacoustic cooling system： The location of the reference temperature section at the heat pump is upside down. The authors construct a prototype ofthermoacoustic heating system. The experimental results show that the heating point reaches 100 ~C. It must be emphasized that, using this simple and inexpensive thermoacoustic heating system, noise, waste heat and unused heat are useful as a renewable energy source.     

Experimental Verification of Model for Liquid-Cooled Staggered Pin Fin Heat Sinks with Top Bypass Flow

Pressure drops and heat transfer over staggered pin fin heat sinks with top bypass flow were experimentally evaluated. The authors considered liquid-cooling applications because there were few data available comparing to air-cooling applications. Empirical equations to predict heat transfer on the endwall were developed by obtaining experimental data on the copper base plate with acrylic pins. A new model for predicting pressure drops and heat transfer over staggered pin fin heat sinks with top bypass flow based on mass, momentum, and energy conservation within the two control volumes is proposed. The first control volume in the model is located within the finned area, and the second is located in the gap between the tip of the pins and the flow channel. This model combines two conditions according to the boundary-layer thickness. A comparison between experimental and calculated results revealed that dimensionless pressure drops and the Nusselt number could be predicted within 30% error for the former and 50% error for the latter.     

Optimizing GSHP Performance with ICT and RETScreen Plus

Under the RHO （renewable heat obligation）, public buildings in the Republic of Korea must achieve an 11% overall reduction to thermal energy consumption in buildings more than 10,0O0 m^2. RETScreen Plus is a freely available software tool developed by the Canadian Government which can be used to develop energy baselines of clean energy technologies. Using curve-fitting and statistical methods like CUSUM, the software can combine actual energy performance with near real time weather information from NASA. We developed a method to simulate the performance of a GSHP （ground source heat pump）. The three distinct energy zones involve heating, no-energy, and cooling. RETScreen Plus methodology is used to develop curve fits for each distinct zone as it builds a correlation with NASA satellite data. The model then factors the impact of ICT （information and control technologies） as a means to improve and lower the building＇s energy consumption. Two values of COP （coefficient of performance） are used--the first is a standard ICT COP, while the second is an improved ICT COP with a smart controller. This methodology can then be expanded to incorporate current and future smart meter technologies, time of use rates, energy price signals, demand response and electricity storage options. In summary, this methodology enables a building owner or energy conservation official to quickly and accurately determine the baseline energy for a building and the potential impacts of smart ICT technologies, especially for buildings equipped with GSHP technologies.     

Simulating the Performance of Solar Water Heating Systems

This paper presents a software for simulating the thermal performance of solar water heating systems. The implemented model computes the energy balance in the hot water storage tank in each time step along a simulation interval. Its input data are values from a typical meteorological year of a chosen location and the hot water load. The system components are the hot water storage tank and the solar collector. Firstly, the validation of the model is presented and then four solar water heating systems are simulated in four different cities along one year. The storage tank water hourly temperatures were obtained for a typical meteorological year and those values were compared with the values obtained by the widespread TRNSYS simulation software. The results obtained from this comparison were satisfactory.     

Testing Thermal Properties of Cooling Device with Heat Pipes to Improve His Heat Transfer Ability

This paper deals about testing thermal properties of the cooling device with heat pipes at inclination position, in consequence of using the natural convection to improve heat transfer properties. Head point testing of cooling device is monitoring temperature on the aluminium block of energy converter, heat pipes and ribs under temperature condition 30 ℃ in thermostatic chamber. Testing of the device was performed at tilt angles positions 0, 10 and 20° from the vertical level. The heat flux loaded to energy converter was 450 W. The next goal of the paper is to research on influence working position of the wick heat pipe on their thermal performance. In this research heat pipes were made with capillary structure sintered from copper powder granularity 100, 63 and 50 μm filled with water and ethanol. Next heat pipe thermal performance was performed by measuring heat source and working positions. Knowledge of these two research goals can bring potential improvements in purpose of cooling device for effective heat sink from high power electronic components.     

Effects of Latitude and Design Variables on Performance and Cost of a Solar Heating System with Seasonal Storage

A thermo-economic model for the simulation and optimization of a CSHPSS （central solar heating plant with seasonal storage） is presented. The model, written in Matlab, allows to analyze the effects of different design and operating variables on plant performance and cost. Daily and seasonal variations of solar irradiation at different latitudes are considered, and an original approximate model for thermal stratification is included. Since a limited computational time is required, the simulation model can be effectively integrated with a non-linear constrained optimization procedure so as to determine the optimal choice of design variables for different locations and operating conditions. The comparison between a two-variable and four-variable optimization for five different locations at various latitudes has been presented, showing a significant decrease in pay-back time with latitude. Finally a sensitivity analysis on the most important design and operating variables has been performed and presented. It emerges that the optimal insulator thickness always decreases with latitude. The optimal tilt angle is slightly lower than latitude only when the plant is designed to cover the whole thermal load, while higher tilt values are selected in case of partial load covering.     

Network Reconfiguration for Load Balancing in Distribution System with Distributed Generation and Capacitor Placement

This paper presents an efficient algorithm for optimization of radial distribution systems by a network reconfiguration to balance feeder loads and eliminate overload conditions. The system load-balancing index is used to determine the loading conditions of the system and maximum system loading capacity. The index value has to be minimum in the optimal network reconfiguration of load balancing. The tabu search algorithm is employed to search for the optimal network reconfiguration. The basic idea behind the search is a move from a current solution to its neighborhood by effectively utilizing a memory to provide an efficient search for optimality. It presents low computational effort and is able to find good quality configurations. Simulation results for a radial 69-bus system. The study results show that the optimal on/off patterns of the switches can be identified to give the best network reconfiguration involving balancing of feeder loads while respecting all the constraints.     

Thermal modelling and parametric study of two stage absorption refrigeration and air-conditioning systems

This paper presents a thoermodynamic assessment of two stage absorption refrigeration and air-conditioning systems. Two working fluids, namely water-LiBr and NH₃-H₂O as refrigerant-absorbent combinations have been considered for the production of different cooling temperatures. Both the systems are assumed to be operated with hot water available from solar collectors. Thermal modelling and a parametric study of a two stage absorption system, based on thermodynamic analysis aided by computer, have been carried out in detail. It is found that the cascading of two stage absorption systems (in which the first stage evaporator produces cooling water to be circulated in the absorber of the second stage) can be easily operated to produce much lower temperatures suitable for refrigeration and air-conditioning applications. The COP of a two stage absorption system is lower than that of a single stage; however, the second stage can be operated with lower generator temperatures than the first stage. However, there is an advantage for a two stage system because of the slow fall-off in COP at higher generator temperatures.