Advanced Materials Research Vols. 614-615

Abstract: The paper analyses some common handling processes on the dedicated outdoor air system with conventional fan-coil units in summer, and studies undertaking cooling loads and humidity loads separately.

Abstract: The performance of the CO₂ trans-critical system is affected significantly not only by optimal system pressure but also by instantaneous ambient temperatures. This paper presents the results of a study carried out to elucidate the influence of the source and sink temperatures on the experimental research of a CO₂ trans-critical refrigeration and heat pump system which used a new dual expansion valve and a balance CO₂ liquid receiver adjustment device. The unit had been fully tested along a multistate experimental study, at various evaporating temperatures and different gas cooler outlet pressures. The results showed that: the source and sink temperatures rose from 15°C to 25°C, trans-critical CO₂ systems COPH average increase of 4.4% each 5°C, but COP decrease of 6.8%. The influence of the source temperature on the chilled water outlet temperature which is less than the sink temperature. The effect of the source or sink temperature on the cooling water outlet temperature to average every 5°C to change the range of from 0.7°C to 1.9°C.

Abstract: In this paper, at first, an effective soil thermal conductivity model was established. Single factor regression analysis for 6 uncertain factors contained in the model was then conducted respectively. Finally, the primary and secondary characters of these uncertain factors were analyzed by using the orthogonal test. The analysis results show that the effective soil thermal conductivity has linear relationships with the saturation degree of unsaturated soil and the depth of water table and has power function relationships with other 4 uncertain factors; the porosity of unsaturated soil has the greatest effect on the effective soil thermal properties, followed by saturation degree of unsaturated soil, porosity of saturated soil, solid phase thermal conductivity of unsaturated soil, solid phase thermal conductivity of saturated soil and the depth of water table.

Abstract: In order to realize long-range real-time online monitor and control of the measured data on the spot, and bring about control consumption of heat-energy according to need, a heat meter is developed for heating supply based on GPRS network technology. Low-power single-chip microcomputer MSP430FW427 is adopted as the measuring instruments in which SIEMENS MC55 module was used as a GPRS communication and LC oscillator coupling technology as flow sensor. In addition, the measurement principle of the heat quantity, the design methods of the software and hardware for heat meter are explained in detail, and the mathematical models of temperature and liquid sensor are established in the paper. Application of GPRS communication technology provides a transparent data transmission channel, thus realizing real-time data exchange between fared knots and monitoring center. On-the-spot operations prove that when the system is in real operation, data transmission rate is about 61.8kbps, thus having more advantages of security，accuracy and data transmission rate, effectively solving the problem of a large number of investment on traditional remote monitoring and control system.

Abstract: Based on European Standard EN441-2, an experiment system for measuring the thermal properties of refrigerated display cabinet is designed and constructed. Considering the practice requirements from user, the air distribution analysis is doing under various air-flow form in the testing room. This paper uses the FLUENT, which is one of the CFD simulation software, to verify the design method of air movement. Finally a series of tests required for laboratory quality regulation have been done and the data of velocity or temperature is under the new requirement.

Abstract: In recent years, the rapid growth of the air conditioning load has become the most important reason of the seasonal power shortage. It has great significance to adjust the air conditioning load for changing the load curve of commercial users and realizing the power grid load shifting. In order to achieve the optimal allocation of resources and improve efficiency of using electricity that make the central air conditioning run efficiently, it needs to study the key technologies of load regulation and management of energy efficiency about the central air-conditioning.

Abstract: The air flow and heat transfer performance of a solar chimney with the inclination angle of 30deg was investigated by using numerical method. It was found that there is a correlation between solar radiation and ventilation rate and there is a temperature field under the effect of thermal pressure. The research result shows that in the certain scope of research, the ventilation rate is influenced by solar radiation. With the solar radiation increasing, the temperature of chimney decrease along direction from the heat absorption wall to the glass cover-plate surface, and the air flow speed distribute nonuniform along the channel width direction.

Abstract: There exists an optimization problem of neutral grounding mode in distribution network with a large number of cable lines. In order to choose the best grounding mode for distribution network, factors of effect of neutral grounding mode on reliability of distribution network are analyzed. The development process of distribution line's fault under each neutral grounding mode is simulated with Monte Carlo simulation method by MATLAB programming. At the same time, the reliability index is got to evaluate and compare this effect quantitatively. An example is used to prove this method’s rationality and effectiveness.

Abstract: This paper summarized the basic steps and processes of urban distribution network planning. It used genetic algorithm with strong global optimization ability for medium voltage distribution network substation outlet to make optimization calculation, and then formed radiation type of power supply network. According to the radial network structure, considering the limitation of the outlet of substation standby capacity and reliability constraint conditions, to meet the situation of minimum investment cost, determined the connection mode of distribution network and contact line direction. This paper adopts an actual distribution network planning project of Tianjin as an example, according to the load forecasting results, determine the connection mode of distribution network and contact line direction, the results meet the reliability, economy and other requirements.

Abstract: This paper introduces the wireless power transfer system( WPT system ) of application prospect, introduces the WPT system of basic components, put forward the LC bridge type resonant compensation circuit topology structure, put forward the new modes to completely symmetrical resonant compensation network apply to the primary and secondary sides ; the simulation results show the effectiveness of the compensation circuits.