Advanced Materials Research Vols. 446-449

Abstract: This paper proposes the method of the fresh air heat transfer enhancement through insert Spiral in the tube of TIEC, and researches the heat transfer enhancement and Flow resistance characteristics through experiment when the Re is 6270 - 11016 range. Through regression analysis of the experimental data, obtained the experimental correlation of the heat transfer and drag coefficient of the strengthen tube, at the same time, evaluate the performance of heat transfer enhancement using appropriate method, and give some exploratory analysis.

Abstract: Many studies have found that the photovoltaic (PV) cell temperature plays an important impact on the solar-to-electricity conversion efficiency. Different cooling liquids like air and water have been introduced to pass across the PVs to reduce the cell temperature, and thus increase the electrical efficiency. In this paper, the refrigerant R134a is used as the cooling liquid and the PV/thermal (PV/T) panel is coupled with a heat pump system acting as the evaporator, which is expected to achieve a better cooling effect and energy performance due to its low boiling temperature. Two different kinds of PV/T panels, glass vacuum tube (GVT) type and flat plate (FP) type, are proposed for the study on the energy performance comparison. The results show that the GVT PV/T panel has an average thermal efficiency of 0.775 and an average electrical efficiency of 0.089 (based on the reference efficiency of 0.12), which is 73.4% and 1.1% higher than that of the FP PV/T panel respectively, with the solar radiation varying from 200 W/m² to 1000 W/m². The GVT PV/T heat pump system has an average COP of 5.6, 9.8% higher the FP PV/T heat pump system. The GVT PV/T heat pump system has a better energy performance than the FP PV/T heat pump system.

Abstract: A cascade ethylene-propane Rankine power cycle that can recover LNG’s cold energy is represented. It is rather appreciated for a CCHP system which uses LNG as the primary energy due to the relatively low operating pressure of the cascade system. The parameter analysis is done for the key process parameters which mainly affect the performance of the system. The results show that the performance can be improved by decreasing the low pressure of the ethylene cycle and increasing the high pressure of the propane cycle. The optimized parameters can obtain 7.43% more electric power and 2.4% more cooling energy.

Abstract: The paper research the loading methods of medium-speed coal mill and the variable loading system of LM18.20 coal mill. The experiment result has shown that using variable hydraulic loading system can make the coal mill running steadily with stable output under varies output conditions; and the mill's loading range is extended; the mill power consumption and wear rate of grinding parts are reduced.

Abstract: The authors numerically simulated the natural ventilation in an industrial workshop with heat sources by computational fluid dynamics (CFD) method and the effect of skylight size on the indoor temperature, ventilation rate and air flow patterns inside the workshop was discussed in detail. Realizable k- turbulent model was used to calculate the flow. Results show that a larger skylight width improves the ventilation. The average air temperature at operation zone decreases and the waste heat directly going into the operation zone decreases when the skylight width increases. The ventilation rate increases very slightly when the skylight width increases from 6 meters to 9 meters, while it increases sharply when w exceeds 10 meters. When the skylight width increases, more hot air is exhausted and the higher temperature environment in the upper zone of the workshop is improved.

Abstract: An alternate means for protecting high-rise stairwell enclosures using the positive pressure ventilation is evaluated. An analysis performed by using the Fire Dynamics Simulator (FDS) model shows that the positive pressure ventilation can be an effective method for protecting the stairwell enclosure. Three types of ventilation methods are compared in the same fire condition and the best one is determined based on the decrease of temperature in the stairwell. The optimal rate for ventilating the stair requires optimization of the airflow rate according to postulated fire scenarios for the building and the desired performance with respect to tenability conditions within the stair.

Abstract: In order to improve the city environment, and achieve a leap in making reasonable use of natural gas and optimizing energy structure, the Beijing municipal government has established its basic policy to “transform its coal-based energy structure, introduce large amount of natural gas”. As the wall-hung gas boiler has easy operation, flexible adjustment and high energy efficiency, the application of it is becoming more widely considered among the residential building. The work proposes the survey of the heating way about affordable housing and the “two limit” commodity housing in Beijing. The adaptability between the household wall-hung gas boiler heating way and other heating ways is compared. The energy efficiency, initial investment and operating cost of all the heating ways that are being used in Beijing are discussed in the paper. The final analysis is then evaluated by a panel of experts to determine its accuracy and potential for use in a greenway development plan of heating way in Beijing. Analysis shows that the commercial housing is more suitable than affordable housing to use the wall-hung gas boiler. This is mainly be effected by the characteristics of the user’s economic condition and the residences’ distribution.

Abstract: In this paper, numerical simulations of heat transfer process in thin heating floor were done by ANSYS. The influence of tube spacing, the average temperature of hot water and indoor air temperature on surface temperature distribution of heating floor and heat density were analyzed. The results can provide reference and basis for optimization, application and promotion of the thin heating floor.

Abstract: The construction of indemnificatory housing has been speeded up from 2009 so as to tackle the difficulty in housing for low-income families in Beijing. With an increasing emphasis on easy operation, flexible adjustment and high energy efficiency, the application of the wall-hung gas boiler are becoming more widely considered among the indemnificatory housing building as a competitive or alternative way to district and central heating. The work proposes the survey of the heating way about indemnificatory housing buildings including low-rent housing, indemnificatory housing and policy-regulated rental housing. The SWOT audit is employed to analyze the satisfaction index of the wall-hung gas boiler and other heating ways. The final analysis is then evaluated by a panel of experts to determine its accuracy and potential for use in a greenway development plan of heating way in Beijing.

Abstract: Parallel fracture formation on surfaces of bi-layered columnar materials like growing tree trunk has been previously studied numerically. In this paper, numerical results of a continuous transition from parallel to polygonal fracture patterns with principal stress ratio provides the clear convincing theoretical explanation for fracture spacing. We perform three-dimensional simulations of fracture growth in a bi-layered columnar model with an embedded heterogeneous layer under inner radial expansion and terminal tension by finite element approach. As a result of this expansion, the bark stretches until it reaches its limit of deformation and cracks. A novel numerical code, 3D Realistic Failure Process Analysis code (abbreviated as RFPA3D) is used to obtain numerical solutions. In this numerical code, the heterogeneity of materials is taken into account by assigning different properties to the individual elements according to statistical distribution function. Elastic-brittle constitutive relation with residual strength for elements and a Mohr-Coulomb criterion with a tensile cut-off are adopted so that the elements may fail either in shear or in tension. The discontinuity feature of the initiated crack is automatically induced by using degraded stiffness approach when the tensile strain of the failed elements reaching a certain value. Numerical results of a continuous transition from parallel to polygonal fracture patterns with principal stress ratio are obtained by varying simulation parameters, the thickness of the material layer. We find that, except for further opening of existing fractures after they are well-developed (saturation), new fractures may also initiate and propagate along the interface between layers, which may serve as another mechanism to accommodate additional strain for fracture saturated layers.