Advanced Materials Research Vols. 860-863

Abstract: Stirling engine has the characteristics of diversification of heat source and high thermal power conversion efficiency. It has broad application prospects in using low-grade energy, such as solar energy, biomass emergy and industrial waste heat. In this paper, Schmidt Method used in the Stirling engine working cycle is analyzed theoretically, and the Stirling engine power output is calculated. The effects of temperature and the average cycle pressure on the output characteristics of the system are analyzed. Theoretical calculations show that the output characteristics can be improved significantly by adjusting the heating temperature and the average cycle pressure. An experiment station is then designed and constructed for the research on Stirling engine power output characteristics. Experimental results show that by improving pre-charge pressure in the working chamber with low temperature conditions, the system can achieve higher power output and thermal efficiency. Pre-charge pressure in the working chamber is adjusted to 2MPa, when the heater tube wall temperature reaches 650 °C, the output power exceeds 1750W, and the effective efficiency will be 23.3%.

Abstract: In the thermal power plant, as an important auxiliary equipment of turbine, the condenser plays an important role in the normal operation of power plant. At present, the domestic operating unit has a large number of old condenses, which has low efficiency and emerging problems because of the increasing running time. Therefore, the transformation of old condenser becomes an important means to tap the potential of the old unit. In this paper, we transform one 300MW unit condenser with its tube layout, then through the numerical simulation and date analysis of the condenser before and after transformation to explore the possibility of modification.

Abstract: The cylinder type natural gas heater is an indispensable piece of equipment in gas production, transmission, and application systems. According to the distinctive structure of the cylinder natural gas heater, the natural convection heat transfer model of both heating surface and cooling surface in the cylinder was built, the temperature and velocity field of the natural convection of the heat-transfer medium--ethylene glycol were numerically simulated. The simulation results show that the symmetrical arrangement of heating and cooling surfaces is not conducive to the formation of an effective heat flow field. Therefore, effective optimizing the layout of the heating and cooling surfaces is obviously a problem that must be solved, to help the heat-transfer medium form a well-organized flow and enhance the heat transfer.

Abstract: In order to obtain the more real condition of the flow field at condenser, the commercial software FLUENT is used to simulate the flow field of the condenser tube bundle area, alone or coupling with the low-pressure exhaust hood and condenser throat. The analysis indicates that the calculation result of combined model is different from the single calculation result of condenser tube bundle area. The flow field of condenser tube bundle area is strongly influenced by low-pressure exhaust hood, the frustums diffuse-angle, the low-pressure heater and the injection of the exhaust steam from the small turbine. The uneven velocity distribution at the outlet of the throat has great influence on the heat exchange of condenser tube. Combined numerical simulation gives more reasonable result.

Abstract: Natural convection conjugated by two partial enclosures, connected by refrigerator/heater, has been numerically studied. Thick walls facing the opening are heated in one zone and cooled in the other zone respectively by constant heat fluxes. The isothermals, streamlines and heatlines are presented for varied governing parameters, Rayleigh numbers, Ra from 10³ to 10⁷, solid thick walls to fluid thermal conductivity ratio λ_S from 0.01 to 10.0, cavity aspect ratio, Ar from 1.0 to 8.0, and refrigeration coefficient, COR from 0.1 to 10.0. The streamlines and heatlines visualize the real fluid flow and heat transfer process or structures. Anti-clock streamlines are generated in both zones. Variations of extreme temperatures, T_max or T_min and dimensionless volumetric flow rate on the opening, M, along with these governing parameters are also presented in tables or figures. Correlations of extreme temperatures with Ra, λ_S and COR are given for varied Ar. At last, the unified correlations of with those parameters also are presented and analyzed. The results show that the common trends and characteristics of heat and fluid flow independent of Ar for both zones are summarized, though the convection is amplified with increased Ar.

Abstract: Risk factor in gas-steam combined cycle power plant (CCPP) was identified by application of safety system engineering principles and techniques. The CCPP system was divided into gas transmission subsystem, gas turbine subsystem, waste heat boiler subsystem, steam turbine subsystem and generation & transformation subsystem. The accident-proneness areas in each subsystem were studied, and various accident-causation modes were clarified. The bursting leakage accident caused by failure of steam-water pipelines was analyzed, and evaluated with Fault Tree method. The targeted countermeasures of safe operation and management were proposed.

Abstract: Software FLUENT is used to carry out the numerical simulation of SCR reactor for studying the influence of the guide plates.The results show that the flowing conditions of the flue gas in the SCR system have a significant influence upon the actual effect of the denitration reaction based on a 330MW coal-fired power plant.In order to improve the performance of the device, choosing the solution that can satisfy the requirement of design which σ (uneven speed value of the first section upon the catalyst) is less than 15%. In the optimal decision,σ is 14.4% and the system pressure drop is 134.43Pa. The appropriate arrangement of the guide plates has a positive impact on the denitration reaction and the workinglife of the catalyst.

Abstract: This paper analyzed the way that dynamic load influenced heat transfer performance of ground heat exchanger in summer conditions, taking a ground source heat pump central air conditioning project in toll stations in Shanxi Province as research subjects. Data analysis indicates that dynamic load effect on the changes of supply and return water temperature of both buried side and load side.

Abstract: The lumped parameter method was used to establish a mathematical model for the spiral heat exchanger with complex structures and specific heat transfer. By implementing the finite difference method, the differential equation was discretized, and then the steady temperature field of the spiral heat exchanger and the dynamic response of temperature can be obtained under boundary conditions and initial conditions. And the essential correctness and measurement accuracy of the model was proved by fluent. The results show that this model can simulate the temperature field and the dynamic response of it well.

Abstract: The heat transfer performance of heat exchanger dependents on the pattern of finned array. The heat transfer coefficient of jacketed tube heat exchanger with and without finned array was investigated by computational fluid dynamics. The results reveal that: the heat transfer coefficient of jacketed tube heat exchanger with in-line-fin and staggered-fin increase to the 87.8% and 98.2% of that without finned array, respectively, and with 35.1% and 37.6% increments of pressure drop correspondingly. The heat transfer coefficient of heat exchanger with staggered-fin increased to 5.4% compared with that with in-line-fin.