Abstract
The relation between rotation speed, air pressure and the velocity of air-rotary drilling using the down the hole method is determined in an empirical manner. For the study, velocity measurements are obtained for combinations of the aforementioned parameters during fieldwork for the installation of borehole heat exchangers near Lublin, Poland. The tests consider three drill bit diameters—110, 127 and 140 mm; three rotational speeds—20, 40 and 60 1/min; and three air pressures—16, 20 and 24 bar. The borehole heat exchangers need 100 m deep wells. The lithology consists mainly of loess and clays to 24 m, sand and carbonate rocks to 36 m, and marls and limestone to 100 m. It is found that the highest drilling velocity is achieved when the greatest pressure is applied, while the lowest drilling velocity is connected to the lowest pressure. However, the relation between rotation speed and drilling velocity is more complex, as drilling velocity seems to be more affected by depth. Therefore, lithology can be a major factor. The results may find direct use in drilling, and provide a basis for further studies on the optimization of drilling technology.
Highlights
Heat pumps were first described in the mid-19th century
After each section was drilled, each of the carbide buttons located on the drill bit was measured and checked in order to assess if any damage occurred (Figure 2)
The relation between drilling velocity and rotations per minute is shown for the considered drill bit diameters and velocity air pressures
Summary
Heat pumps were first described in the mid-19th century. In 1852, it was proposed to use them for space heating, as an open cycle tool connected to a compressor, and two water tanks serving as upper and lower heat sources. The idea never came to fruition, despite multiple tries. The first practical use for the heat pump came much later—in 1928, T.G. Haldane created an installation for heating his own house [1,2]. Industrial, high-power heat pumps were used in the interwar period in the USA. In the post-war period, a significant increase in the use of heat pumps was noted in various countries [3]
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