Guohua Shi

Evaluation of a Double-Stage Coupled Heat Pump for Heating: Performance Optimization and Case Study

AbstractA thermoeconomic model for a double-stage coupled heat pump (DSCHP) with finite-rate heat transfer, heat leakage, and internal irreversibility has been developed. The heating load per unit total cost has been taken as the objective function. The optimal performance characteristics of the DSCHP have been discussed in detail and the optimum design parameters have been deduced analytically. The theoretical model has been exemplified in a particular case study. The investigation results demonstrate that the model is accurate to within 15% of the experimental data. The DCSHP design, with thermoeconomic optimization, leads to a significant increase of the specific heating load and a clear improvement of the economic performance with a small decrease of the coefficient of performance. When the values of ambient temperature, irreversibility of cycle I, irreversibility of cycle II, and investment cost per unit power have the same variation (5%), the objective function changes about 5, 5, 4.4, and 4.5%, res...

Prospects of natural gas storage and transportation using hydrate technology in China

Natural gas is becoming a main source of town gas in China. It is difficult to supply natural gas by pipelines from gas fields to every city in China. To solve the problem, natural gas hydrate (NGH) technology is introduced in this paper. At the same time, NGH technology is compared with liquefied natural gas (LNG) technology and compressed natural gas (CNG) technology. We conclude that NGH technology has many particular advantages, such as moderate conditions of production and storage, simple technology and high security. A domestic NGH gas supply chain is proposed including the production of NGH, the road transportation of NGH, the regasification of NGH and the gas distribution. In addition, a cost analysis of NGH gas supply chain is made compared with LNG gas supply chain. The result shows that the gas supply technology via NGH is more cost effective and has powerful competitive in China. Considering the technical advantages and the economic efficiency of NGH technology, we conclude that it has a bright application prospect in China and put forwards some suggestions on realizing the commercial application of NGH technology.

An illustration of the optimization of combined cooling heating and power systems using genetic algorithm

The performances of combined cooling, heating and power (CCHP) system are greatly dependent on its design, operation strategy and thermal and electric demands. This paper illustrates how the use of a genetic algorithm can provide speedy optimization, by applying it to two styles of buildings operated in different operation strategies. The primary energy consumptions of CCHP system following electric demand management (EDM) and thermal demand management (TDM) are firstly analyzed respectively. Then, sixteen hypothetical buildings are constructed to represent various energy demands. Primary energy saving (PES), annual total cost saving (ATCS), and CO2 emission reduction (CO2ER), are weighted to evaluate the integrated performances of CCHP system in comparison to separation production system. Finally, the optimized CCHP system for sixteen scenarios using GA are compared. Practical application: This paper provides an optimization design method for CCHP system. The performance analysis of CCHP systems running different operation modes for different buildings is believed by the authors to contribute to a significant guide for the fundamental design of CCHP systems. Although sensitivity to a number of other important design considerations such equipment performance, possible future changes in operating conditions, changes to the price or carbon intensity of grid-supplied energy etc are not addressed, the conclusions present a simple and effective direction and the proposed optimization algorithm and the evaluation method for CCHP system can be extended to other buildings.

Experiment on Hg 0 removal from flue gas by sodium chlorite solution

The important to enhancing gaseous elemental mercury (Hg0) removal in wet scrubber systems is altering the chemical form of the Hg0 to a water-soluble oxidized species. Experiments on the removal elemental mercury from simulated flue gas by aqueous sodium chlorite in a bubble reactor were carried out in this work. The effect of initial oxidizing solution concentration, reaction temperature, pH and SO2 concentration on mercury oxidative absorption in sodium chlorite were investigated. The results indicate that the higher concentration of sodium chlorite favors Hg0 removal, whose efficiency is greater in acidic than alkaline solution. High temperature inhibits Hg0 absorption in aqueous sorbent when reaction temperature is lower than about 40□, and the removal efficiency increases whereas temperature is higher than about 40□. The SO2 concentration did not significantly affect the efficiency of Hg0 removal.

Application of Entropy Method in Fuzzy Synthetic Evaluation for Micro-Turbine Performance

Distributed generation (DG) is becoming the indispensable supplement to the centralized generation. Micro-turbine is paid more and more attention in scientific research and commercial application due to its unique advantages and gradually becomes the core of distributed generation. It is essential to make a synthetic and scientific evaluation on the performance of micro-turbine in order to promote the progress of the distributed generation technology using micro-turbine. This article gives the synthetic performance evaluation of micro-turbine. Some performance characters (rated capacity, generating efficiency, rotation speed, pressure ratio, fuel consumption, multi-fuel, intake temperature, exhaust temperature, NOx emission level, noises and life time) were chosen as evaluating indicators and some common micro-turbines were taken as evaluating objects in this paper. Considering the difficulty of fuzzy synthetic evaluation method in calculation of the multiple factors and the ignorance of the relationship among evaluating objects, a new weight evaluation process using entropy method was introduced. The entropy method is an objective way for weight determination. The improved method for weight determination of the evaluating indicators was applied in performance assessment of the micro-turbines. The evaluation result of the example showed that this method was favorable for fuzzy synthetic evaluation when there was more than one evaluating objects and the entropy method for determination of weight was a very effective method for evaluating indicators. The method predigested the fuzzy synthetic evaluation process greatly and the evaluation results are more reasonable.Copyright

Study on zero discharge technology of wastewater from power plant

This electronic document is a “live” template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document. About 60 percent or 70 percent of the cities in China are short of water in different degree, thus the water resource is very shortage in China. The problem of water shortage has restricted the industrial development. The matter is especially severe in North China and the area with water shortage areas. It is critical to increase the concentrated ratio of the circulating cooling water and decrease the wastewater discharge for the power plant, where the circulating cooling water system is used. According to the characteristic of the wastewater in the power plant at present, the problems of the optimization of the wastewater treatment are put forward in this paper. Whats more, the technology of staged concentration of circulating water used for supplying water is designed, viz. the circulating cooling water is concentrated in stages and operation in series with the supplying water. The practical engineering experience in a certain power plant, indicates that it is profitable for the technology of the supplying water being series-wound concentrated stepwise. With the use of this technology, the number of the discharge of wastewater is reduced, all of which reveals the social, economical and environmental benefits.

Study on treated wastewater from power plant as circulating supplementary water

The water consumed by power plants is about half of the total annual industrial water consumption in China. Considering some characteristics of wastewater in power plants, the paper presented a new process to treat the wastewater. In the process, wastewater was made centralized treatment utilizing activated sludge firstly, then water purifying agent was put into the wastewater and they were coagulation sedimentation. The wastewater was treated by aeration and disinfection at last. In order to increase the efficiency, the ash conveying water was used as the cogulating aid in the process. The experimental results showed that the presented process was effective. The quality of the wastewater after treated was stabile and the ash conveying water was beneficial to the flocculation promotion. The effluent was well used for the circulating cooling water system. It can be concluded that the wastewater of power plants can be the supplementary water of the circulating cooling water system after appropriate treatment. The engineering practice indicated that the process can reveal the social, economical and environmental benefits and be helpful to the realization of the zero discharge of the power plants.

Analytical design of decoupling control for variable flow hydronic heating system

Hydronic heating systems are used in homes and apartments worldwide. The variable flow system is advantaged to the energy saving while the control in variable flow system is difficult. This paper describes the typical variable flow hydronic heating system and presents the coupling mathematical model of heat exchanger. Based on the mathematical model, a new analytical design method of decoupling controller matrix is proposed in terms of the standard internal model control structure for variable flow hydronic heating system. Its advantage is that absolute decoupling for the nominal responses of system outputs can be implemented, and moreover, the controller parameters can be tuned on-line in a monotonous manner to cope with the perturbed plant dynamics, so that significant decoupling regulation can be achieved. The detailed simulation shows that the decoupling control system is effective and feasible.

Evaluation Indexes and Methods of Energy-Efficient Buildings

The energy consumption in the world and the environment protection impel more attention to the energy-efficient building. This paper briefly introduced the energy consumption of buildings and the endeavor to improve energy efficiency in buildings in China. The evaluation indexes for energy-efficient buildings are reviewed and they would be obtained in different ways in the lifecycle of buildings. Then the evaluation methods or systems for energy-efficient buildings are presented. It can be found that the evaluation systems are prosperously developed and the evaluations in all lifecycle of the buildings is helpful to establish the policy, encourage governments, producers and users active actions and decrease the energy consumption in buildings in the future.Copyright

Performance Evaluation for Micro-Turbine Using Modified TOPSIS With Objective Weights

Micro-turbine is paid more and more attention in scientific research and commercial application with the development of distribution generation (DG) in the global range. It is essential to make a synthetic and scientific evaluation on the performance of micro-turbine in order to promote the progress of the distributed generation technology using micro-turbine. This study presents the synthetic performance evaluation of micro-turbine. Some performance characters (rated capacity, generating efficiency, overall system efficiency, unit cost, fuel consumption, multi-fuel, NOx emission level, noises and life time) are chosen as evaluating criterions and some common micro-turbines are taken as evaluating objects in this paper. Considering the difficulty of fuzzy synthetic evaluation method in calculation of the multiple factors and the ignorance of the relationship among evaluating objects, a modified TOPSIS with objective weights is introduced and applied in performance assessment of the micro-turbines. Each criterion weight is calculated based on Shannon’s entropy concept. The evaluation result of the example shows that this approach is favorable for fuzzy synthetic evaluation of micro-turbine performance, particularly applicable for situations where reliable subjective weights from experts cannot be obtained. The evaluation results can also be as references for manufactures how to improve design of micro-turbines and for users how to make proper selection of micro-turbines.© 2009 ASME