Applied Mechanics and Materials Vols. 204-208

Abstract: In earth energy utilization, different multi-well flow match modes determine the different groundwater thermal flow transport characteristic. In this study, a laboratory experimental system was designed and set up to study the aquifer heat transfer performance and temperature field variation in different multi-well flow match modes. The experimental results show that under the condition of certain total flow rate, different multi-well flow match modes have great effects on the change of groundwater seepage field and temperature field. The bigger the flow rate, the greater the heat transfer per unit time and temperature field variation, and the closer the occurrence time between cold water frontal and cold water effect frontal, which is not conducive to the active control of aquifer temperature field.

Abstract: In city gas leak detection, common methane detector is vulnerable to gases such as CO, CO₂,H ₂O and actual conditions of interference (such as humidity, coverings and wind direction), causing false detections and failure judgment. we put the optimization of optical methane detector with infrared absorption principle to replace the traditional combustible gas detector. In order to improve accuracy and efficiency of the gas leak detection, we put forward vehicle-mounted OMD^TM optical methane detectors and complementary methane portable RMLD^TM laser distance measuring instrument using a new method for gas leak detection. This method is effective to exclude other combustible gases such as methane to leak detection of interference effects, it not only covers the whole of the city gas network, proactively preventing leakage accidents from happening. In the leaks rescue operation, with it, testing vehicles can quickly arrive at the scene to participate to find the leaks, and deal with the leaks as soon as possible. Engineering field application effect suggests that the gas leak detection accuracy rate is higher, low false positive rates, fast response, and it meets the needs of modern urban gas leak detection.

Abstract: The absorption heat pump was studied with finite time thermodynamics. A four reservoirs model of absorption heat pump which is treated as an irreversible Carnot heat pump driven by an irreversible Carnot heat engine was established considering the heat resistance and the irreversibility of the internal cycle. A generalized optimization relationship between the main parameters and the corresponding conditions were derived. It is show that, two internal irreversibility parameters, the heat engine cycle and the heat pump cycle has different effects on system performance, and the reduction of the friction, heat loss, and internal dissipations of the equivalent heat pump cycle are more important than its reduction of heat engine cycle.

Abstract: There were many issues in numerical methods of heat transfer problems such as instability at a big time step length or grid size and no-existence of inverse matrix by time-precise integration method. For sake of avoiding instability and calculating an inverse matrix, a coupling method was put forward based on EFGM and IDPIM. Formulae were deduced according to EFGM and IDPIM. Results show that the coupling method has a higher accuracy and its stability is small subjected to the time step length or grid size, and is to deserve to be popularized.

Abstract: Floor radiant heating system has many advantages, energy and space saving, for example. The radiant floor is the radiator of floor radiant heating system, and its thermal parameters influence surface temperature distribution and comfort. In this paper, mathematical model of heat exchange coil under floor was established, and boundary heat transfer conditions were given. Based on these, surface temperature of different covering layer was calculated. According to the results, using different covering layer, the floor surface temperature has a great difference. Using wooden floor as cover material, the floor surface temperature is more moderate and uniform.

Abstract: The laying of gas pipeline with tunnel crossing method, except under the influence of pressure, temperature, and out of gas direction, it also subjected to constraints of soil, soil temperature, terrain conditions and the impact of earthquakes. Also crossing pipes are in the constraints of fixed pier, anchorage pier and pier pipeline deformation, which makes the stress analysis of boundary is difficult to determine. In order to compare the effect of different constraints and out of gas direction on the entire tunnel crossing pipeline under operating conditions, this paper has established three pipe models: the symmetrical form of the direction of access to gas, completely without supporting (do not canceled the fixed pier at both ends)and with supporting form, then the primary stress, secondary stress and compound stress are checked in turn. By comparing their impact on the stress of the whole pipeline, we get the importance and extent of the main constrains on the pipeline stress.

Abstract: Building ventilation has typical regional characteristics, due to its annual high wet climate characteristics in hot summer and cold winter area, the choice of ventilation type is especially important. The present building energy consumption simulation and thermal comfort evaluation of is inadequate to air humidity effects, and easily to ignore ventilation energy saving potential with building thermal environment control. In this paper based on the region annual building humidity environment characteristic, author put forward a kind of building ventilation and dehumidification integrated solutions, from a methodological point of view to explore a ventilation and dehumidification integrated technique with air conditioning and heating period , try to deal with the indoor thermal environment quality problems with lower energy consumption.

Abstract: For the purpose of realizing non-dewfall condition of the radiant panels, low energy consumption and nice comfort of the freezing dehumidification-based radiant air-conditioning system, the design temperature and humidity of the room were figured out according to the mean comfort index of human body during the design. And in order to lower the energy consumption, the necessity of the reasonable load allocation between the dehumidification unit and the radiant unit was discussed by means of the calculation with the quasi heat-humidity-ratio line. As a result, much more precise design parameters were acquired through the approximation calculation. And it was proven to be a good design method by applying these parameters to the design of the reading rooms of the library. In the design example of the reading room, the load ratio between the dehumidification unit and the radiant unit was 48 to 52, and the recirculation air flow rate of the dehumidification unit was not less than 36.8% of the total air rate of the room.

Abstract: Considering the central air conditioning system is highly susceptible to interferences from external environment, this paper established a dynamic mathematical model for chilled water system with the air conditioning area, fan coil unit and air conditioning area interference factors. Selection of chilled water system as a controlled object, designed the energy saving control system for central air-conditioning. The inputs of PID controller are deviation of actual temperature and setting temperature, and the change rate of the deviation; output is operation frequency of pump. Experiment shows that, PID control system in 90% time operating at a frequency of 10Hz-40Hz, average is 32.5Hz. Compared with no control system, the pump power consumption was reduced 33.9%.In conclusion, PID control in the central air conditioning system have a good energy saving effect.

Abstract: Central air-conditioning control system have characteristics of susceptible to outside interference, nonlinear, time-varying, hysteresis and difficult to build precise mathematical model. Central air conditioning chilled water system with variable water flow was taken as subject. According to the principle of energy saving, on the basis of traditional PID controller, adaptive fuzzy PID controller was designed. Fuzzy control algorithm determines the choice of parameters of PID controller K_P、K_I、K_D , with which, then, regulate the output of adaptive fuzzy PID controller; Finally the output value determination of the operation frequency of the chilled water pumps. Compared with conventional system temperature control, adaptive fuzzy PID control in central air conditioning system has good energy-saving effect.