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The horizontal ground heat exchanger has been extensively employed to collect geothermal energy from mine backfill bodies. A novel method for avoiding thermal interference using the thermal influencing radius coupling pipe spacing was investigated. Thermal interference between adjacent heat-transfer pipes can be neglected when D40°C=2R40°C is used as the pipe spacing. The comprehensive impacts of heat-transfer fluid and backfill body on the heat-transfer efficiency and thermal influencing radius of the horizontal single pipe were investigated. The growth ratio of heat-transfer capacity can be as high as 227.3% when thermal conductivity increases from 0.5 kJ/(kg·°C) to 2 kJ/(kg·°C). The heat-transfer capacity increases by 4% for every 1°C reduction in inlet temperature. The thermal influencing radius is significantly influenced by specific heat capacity and thermal conductivity. This study can provide theoretical recommendations for the design and improvement of heat-transfer pipes in the backfill body. [ABSTRACT FROM AUTHOR]

In this study, the stress and deformation rules of the double-row fiber-reinforced plastic sand pipes under the two loading methods of single-pipe and double-pipe loading were discussed. First, the indoor full-scale test was used to analyze the single-tube pipe top loading. The 90° measurement point of the loaded pipe and the 270° measurement point of the adjacent pipe were the most unfavorable positions for the stress of the pipeline. Through investigating the influence of cover soil height, load level, and compaction on the mechanical index of the most unfavorable load-bearing measuring point of the pipeline, the height of the overburden is found to be the most significant factor affecting the double-pipe stress system. Second, the numerical calculation model of the stress of the double-row pipeline was established to analyze the stress and deformation of the pipe culvert when the spacing of the double pipe was changed. The results indicated the critical spacing equivalent to the stress of the single pipe was 2.5D. Finally, the numerical method was also used to optimize the parameter of the geogrid at the top of the pipe in the most unfavorable stress state of the double pipe with 550-mm pipe spacing and double-loaded mode. [ABSTRACT FROM AUTHOR]

Considering heat and moisture transfer, seepage and freezing simultaneously, a three-dimensional dynamic simulation platform of the ground source heat pump system (GSHPS) is established. Based on this platform, the annual performance of the GSHPS is analyzed. The results show that with the increase of pipe spacing, the soil moisture transfer radius, freezing time and freezing distance become smaller, and the unit performance becomes better. Compared with the pipe spacing of 3.5 m, when the pipe spacing is 4.5 m and 5.5 m, the moisture transfer radius decreases by 11.6% and 20.9% in summer and 6.7% and 15.6% in winter, the freezing time decreases by 25 days and 45 days, the maximum freezing distance decreases by 28.6% and 63.3% in unsaturated soil and 31.7% and 63.4% in saturated soil, and the unit average coefficient of performance (COP) increases by 0.7% and 1.9% in cooling period and 5.2% and 12.1% in heating period, respectively. The moisture transfer radius and freezing distance around the central borehole are the largest, and those around the boundary intersection borehole are the smallest. Compared with all other possible working conditions in heating period, the system performance is the best when considering heat and moisture transfer, seepage and freezing simultaneously. • A numerical model considering heat and moisture transfer, seepage and freezing simultaneously is proposed. • A three-dimensional dynamic simulation platform of the ground source heat pump is established. • Moisture transfer radius of the soil under different pipe spacing is studied. • Freezing distance of the soil under different pipe spacing is compared. • The annual performance of the unit under different pipe spacing is analyzed. [ABSTRACT FROM AUTHOR]

With the help of a three dimensional mathematical model of groundwater of Modflow, the high-efficiency agriculture park in Yuyao City was chosen as study area to research the groundwater dynamic regulation under various rainfall recharges, on the basis of collecting fundamental information of the park and conducting hydro-geological investigation. According to the hydrodynamic processes of groundwater level under different designed rainfall events and water-level control boundaries in rivers as well as different pipe drainage schemes, the relationship between groundwater level regulation and depth and spacing of drainage pipes was analyzed, and then groundwater dynamic drainage system was determined. The result shows that the optimized drainage scheme is the pipe drainage system with space width 15 m and 2.5 m for depth. The drainage rule for the shallow groundwater at complex hydrogeological region was explored, which will provide scientific decision-making reference for groundwater level control of precision agriculture and prevention and cure of soil salinization. [ABSTRACT FROM AUTHOR]

An active pipe-embedded building envelope, which is an external wall or roof with pipes embedded inside, was presented. This structure may utilize the circulating water in the pipe to transfer heat or coolth inside directly. This kind of structure is named 'active pipe-embedded building envelope' due to dealing with the thermal energy actively inside the structure mass by circulating water. This structure not only deals with thermal energy before the external disturbance becomes cooling/heating load by using the circulating water, but also may use low-grade energy sources such as evaporative cooling, solar energy, and geothermal energy. In the meantime, this structure can also improve the indoor thermal comfort by tempering the internal wall surface temperature variation due to the thermal removal in the mass. This work further presents the thermal performance of this structure under a typical hot summer weather condition by comparing it with that of the conventional external wall/roof with numerical simulation. The results show that this pipe-embedded structure may reduce the external heat transfer significantly and reduce the internal wall surface temperature for improving thermal comfort. This work also presents the effects of the water temperature and the pipe spacing on the heat transfer of this structure. The internal surface heat transfer may reduce by about 2.6 W/m when the water temperature reduces by 1 °C as far as a brick wall with pipes embedded inside is concerned. When the pipe spacing reduces by 50 mm, the internal wall surface heat flux can also reduce by about 2.3 W/m. [ABSTRACT FROM AUTHOR]

A numerical simulation model of a greenhouse floor heating system was developed and validated using data collected in a research greenhouse located at Cook College, Rutgers University, New Brunswick, New Jersey. The model was then modified and used to evaluate two different heat pipe diameters and spacings that are typical in the greenhouse industry today: 13 mm (0.5 in.) diameter pipe placed on 22.9 cm (9 in.) centers, and 19 mm (0.75 in.) diameter pipe placed on 30.5 cm (12 in.) centers. Two heat pipe elevations within the solid concrete floor system were also simulated, and the effects of the pipe's vertical position, diameter, and spacing on surface heat flux, surface temperature, and surface temperature uniformity were evaluated. The simulation results showed that the smaller diameter pipe placed closer together and at a lower elevation provided the best temperature uniformity without compromising other performance criteria. The model was then further modified to simulate flats with growing media placed on the floor surface. Model simulations were conducted for six different supply water temperatures ranging from 32.2 °C (90 °F) to 60 °C (140 °F), while maintaining a target ambient greenhouse air temperature of 15.6 °C (60 °F). The simulation outputs showed that using the smaller diameter pipe placed closer together resulted in a higher surface heat flux, a higher growing media temperature, and greater temperature uniformity within the growing media, for each supply water temperature simulated. [ABSTRACT FROM AUTHOR]