Advanced Materials Research Vols. 960-961

Abstract: In the paper, by studying the underground heat exchanger heat transfer mode, the computing platform for ground source heat pump system was established. Through a engineering case, the influence character of the fluid temperature at the outlet of ground heat exchange on the length of system, the fluid temperature in ground heat exchange, and the heat pump power consumption were analyzed, which provide an approach for engineering design and operation prediction, and for the thermodynamic analysis of performance of system year by year and prospective study to guide the engineering practice.

Abstract: This paper deals with the study of transmission and distribution energy consumption (TDEC) optimization design about surface-water source heat pump system. Three mathematical model have been established. The fitted polynomials of COP, N_e, N_c were obtained by the MATLAB curve fitting toolbox according to datum from product samples. The differences between two operating states which are constant flow and variable flow were analyzed and compared. Under variable flow operating state it was found that there exists an maximum energy conversation rate12.68% of TDEC; the heat pump unit will consume more than average 8.41% energy, while COP will decline average 7.61%, the mean energy conversation rate of N_e and N_c are 49.38% and 38.86%, the average declination rate of t_ein and t_cout are 17.09% and 5.73% compared with constant flow operating state.

Abstract: In order to reduce pressure drop of filtration process and increase filtration area, filtration media would usually made into pleated shape. The designs of pleats numbers and pleats height in the unit length have greatly impacted on pressure drop of the filtration process. In this paper, filter pressure drop of pleated air filters were examined by theoretical, experimental and simulation studies. By solving pressure drop from the Navier-Stokes equation on basis of velocity function assumption, by using the concept of average pressure drop in wind gap width, pressure drop in pleated filters was calculated. The numerical simulation of pleated filtration media was developed via using FLUENT software package and flow field variation in gap of pleated media was simulated. The results of theoretical calculations were in agreement with experimental results. It was confirmed that reducing pleat spacing or increasing pleats height could increased the area of filtration media and reduce the overall pressure drop of filters, although structure pressure drop increased. There were best value between pressure drop of pleated air filters and pleat numbers in the unite length. Key words: filtration medium; pressure drop; numerical simulation; air filter; pleated structure

Abstract: Based on the theoretical derivation of hydraulic coupling relationship between the hydropower units sharing long common tunnel,the non-linear hydro turbine model with sharing long diversion tunnel system is established and order-reduced in accordance with the demand of power system simulation. And according to the complex structure characteristics of surge tank,a method of correcting surge tank storage constant with surge tank structure coefficient is proposed. This hydro turbine model can reflect the influence of surge tank and sharing common tunnel in the power system long term process,the accuracy of model is proved by comparison of simulation results and actual recording data in power system.

Abstract: Doubly-fed induction generator (DFIG) wind turbine has become a mainstream machine of wind generators in China. As the different operational characteristics between the DFIG and synchronous generator (SG), the large amount of DFIG-based wind generators installed in the grid may bring a series of impacts on the dynamic behaviors of power system. In order to study the DFIG transient characteristics on the condition of the voltage dips happening in the power system, a definition of the DFIG power angle is given and the effects of the converters on the DFIG power angle are discussed. On this basis, the transient angle characteristic of the DFIG is derived. The DFIG transient characteristics are performed by Matlab/Simulink software, the simulation results demonstrate that the DFIG has the resemble power angle characteristic of SG and prove the effectiveness of the derivation process, which lay a foundation for the study on the interactions between the DFIG and power system.

Abstract: The rough model method (RMM) is explained through its application to the design of a pressurized circular shaped conduit with benches, widely used in practice. The three basic equations of turbulent flow are firstly applied to define explicitly the geometric elements of a referential rough model characterized by an arbitrary assigned relative roughness value. The required linear dimensions of the studied conduit are then easily deduced by multiplying the homologues linear dimensions of the rough model by a non-dimensional correction factor. Friction factor is not indispensable when applying the RMM, unlike current design methods. Resulting RMM equations are not only explicit but are also valid in the entire domain of turbulent flow.

Abstract: Volatile organic compounds (VOCs) are emitted from the refueling of gasoline vehicles and trucks. Controlling these emissions has been an important issue since the late 2000s in China. We have recently developed a condensation refueling gas recovery system to recover the VOCs from gaseous wastes at a bulk gasoline terminal. In this system VOC vapor is condensed by a reversed turbo-Brayton cycle refrigerator. The recovery system has a capacity of 100 Nm³/hr at the lowest condensation temperature of 190K. It has been put into use since 2008. The achieved recovery efficiency is 96% and the emission of VOCs is less than 8 g/m³ at the exit of the recovery system.

Abstract: This paper introduces the advantages of capillary roof radiant heating system, by using finite element numerical method, the indoor temperature distribution of capillary radiant roof and underfloor supply air composite system is simulated, using the theory of exergy to analysis the energy saving of the system, the result proves that the system can well satisfy indoor comfort requirements, and compared with the floor radiation heating system can saving energy 65.8%, has great research value.

Abstract: Taken as the carrier of heat extraction between rock-soil body and ground source heat pump systems, U-tubed pipe heat transfer efficiency was the key for ensuring the long-term and high-performance operation of ground source heat pump systems by means of improving the heat transfer effect. The efficiency coefficient, E, is defined as the ratio of the actual heat transfer capacity to the theoretically maximal heat transfer capacity from the U-tube into rock-soil body, which illustrated the effect of heat transfer ability and the variable heating or cooling loads. Aim at Variation characteristics of heat transfer coefficient of energy efficiency under the variable temperature inflow condition, decomposed into the product of the ratio of biggest buried tube heat transfer temperature difference φ and heat pump outlet water temperature difference σ. Use of u-shaped buried pipe three-dimensional heat transfer model which based on the multipole theory, the influence law of its change which caused by the construction load, buried pipe flow and the unit performance were analyzed, it can provide technical support to optimize the design of ground source heat pump system.

Abstract: This paper introduces a virtual experiment bench for automotive air conditioning. In the experiment bench based on the experiment bench for Corolla 1.6AT automatic air conditioning, the refrigeration, heating, gas distribution and other mechanical systems are removed and the electrical control system is reserved using the virtual and simulation theory. The experiment bench has the features, such as simple structure, low production and operation cost, safety and environmental protection; its main sensor signals are simulated through a variable resistance, the working processes of some actuators are shown by light bulbs, so that it is easy to operate the experiment bench, and the working process is visual and direct. The experiment bench can be self-developed, designed and produced by students under the guidance of teachers, thus to promote the comprehensive ability of students to use knowledge and innovate.