The Effect of Groundwater Flow on the Thermal Performance of a Novel Borehole Heat Exchanger for Ground Source Heat Pump Systems: Small Scale Experiments and Numerical Simulation

New small-scale experiments are carried out to study the effect of groundwater flow on the thermal performance of water ground heat exchangers for ground source heat pump systems. Four heat exchanger configurations are investigated; single U-tube with circular cross-section (SUC), single U-tube with an oval cross-section (SUO), single U-tube with circular cross-section and single spacer with circular cross-section (SUC + SSC) and single U-tube with an oval cross-section and single spacer with circular cross-section (SUO + SSC). The soil temperature distributions along the horizontal and vertical axis are measured and recorded simultaneously with measuring the electrical energy injected into the fluid, and the borehole wall temperature is measured as well; consequently, the borehole thermal resistance (Rb) is calculated. Moreover, two dimensional and steady-state CFD simulations are validated against the experimental measurements at the groundwater velocity of 1000 m/year with an average error of 3%. Under saturated conditions without groundwater flow effect; using a spacer with SUC decreases the Rb by 13% from 0.15 m·K/W to 0.13 m·K/W, also using a spacer with the SUO decreases the Rb by 9% from 0.11 m·K/W to 0.1 m·K/W. In addition, the oval cross-section with spacer SUO + SSC decreases the Rb by 33% compared with SUC. Under the effect of groundwater flow of 1000 m/year; Rb of the SUC, SUO, SUC + SSC and SUO + SSC cases decrease by 15.5%, 12.3%, 6.1% and 4%, respectively, compared with the saturated condition.

Middle Neolithic of the Kamchatka Peninsula

Purpose. The study of archaeological sites of the Middle Neolithic of Kamchatka should offer a chronology and a set of criteria for identifying the period. Results. The research data is based on the materials of the studied cultural layer, buried dwellings and individual artifacts of 46 archaeological sites. It has been established that the average Neolithic of Kamchatka can be dated back to 4 000–1 500 cal BP. The sites were found on high water-glacial terraces with a height of 4 to 30 meters on the banks of large rivers and lakes, the sea coast of the eastern part of the peninsula. Their number had increased compared to the previous period. Dwellings had become more complex. Perhaps this is due to the need to have more reliable shelters in the conditions of the marine climate and frequent precipitation of volcanic ash. The ground buildings, semi-underground dwellings and workshops for the manufacture of stone tools were found at the sites. Near the dwellings, special fortifications in the form of artificial ditches and ramparts made of stones and soil were also found. These may have been defensive structures. The increased population size, its settlement mainly along the coast in order to develop marine resources, may have caused conflicts between certain groups of the population in the struggle for the best fishing sites. The stone industry is represented by cores (amorphous and prismatic knife-shaped blades) and primary cleavage products (knife-shaped blades of different sizes without retouching, with edge retouching and on both sides). Among the tools there were retouched triangular stone arrowheads without stem and with stem, leaf-shaped, including miniature, arrowheads; knives – narrow and wide-bladed with a dedicated handle, leaf-shaped oval; roughly beaten and polished sharp-edged adzes of different sizes with a sub-triangular and oval cross-section; end scrapers of various geometric shapes; calibrators of arrow shafts. The strategy of life support of society was aimed at hunting for marine mammals, fishing and gathering, including shellfish. In the sphere of spiritual culture, signs of ceremonial activity (labrets) and art (small figurines and ornaments) have also been identified. Conclusion. It is assumed that with an increased population size and changes in the environmental situation, a new way of life of the population developed, associated with a highly specialized and complex appropriating economy which essentially formed its own archaeological culture (Taryinskaya culture).

Flow "reflexion" and " refraction" on perforated wall

This article presents some results accumulated by author during investigation of an oblique impact of fluid flow on a wall consisting of a spatially periodic rods of very simple oval cross section. The flowfield in the vicinity of the impact is quite complex and strongly Reynolds -number dependent. A part of the jet downstream from the impact is “reflected” from the wall — while the rest, which passes through the empty spaces between the cascade members, leaves the other wall side in what appears to be “refraction” direction.

Joining by Die-Less Hydroforming of Profiles with Oval Cross Section

Joining by die-less hydroforming is used to produce overlap joints by means of hydraulic expansion. Due to a difference in the elastic recovery of the two joining partners an interference pressure p remains at their contact area. Due to the possibility to produce multi-material joints without relying on heat, the process has great potential for joining parts in lightweight applications. Therefore, the process limits were extended so that profiles with non-rotationally symmetric cross-sections can be joined. For this purpose a new tool for profiles with oval cross-section was developed. The inner and the outer joining partner ware made of aluminum 6060 and aluminum 6082 respectively. The influence of the overlap length and different wall thicknesses of the outer joining partner were investigated by numerical simulations and validated by experiments. An upper limit in interference pressure was observed which was also found previously for profiles with circular cross sections. The fluid pressure limit is compared with the analytically calculated value for a configuration with circular tubes under equivalent conditions. The analytical model underestimated the pressure limit. In contrast to circular tubes, the strain distribution of profiles with oval cross sectional shapes is not uniform, which results in superposed bending stresses. Also a difference in stiffness of the inner and outer joining partner leads to a pressure depended contact area which is assumed constant in the analytical model.