A borehole heat exchanger cycle, comprising at least two borehole heat exchangers for exchanging heat between a heat transfer liquid and ground soil in which the borehole heat exchangers are disposed in the operating condition, each with a) an inflow pipe having an inner surface of the inflow pipe facing into the inflow pipe and an outer surface of the inflow pipe facing towards the ground soil, b) an outflow pipe comprising an inner surface of the outflow pipe, which faces into the outflow pipe and encloses an outflow pipe chamber, and an outer surface of the outflow pipe pointing outwards away from the outflow pipe, c) an annular chamber, which is located within the inflow pipe and is horizontally delimited by the inner surface of the inflow pipe and the outer surface of the outflow pipe, d) a connecting portion, which interconnects the annular chamber and the outflow pipe chamber in a fluid-conducting manner and is disposed at a lower end of the borehole heat exchanger, e) a feed pipe, which is connected to the annular chamber in a fluid-conducting manner and is disposed at an upper end of the borehole heat exchanger, and f) a drain pipe, which is connected in a fluid-conducting manner to the outflow pipe chamber and is also disposed at an upper end of the borehole heat exchanger, g) at least one means for producing turbulence in the heat transfer liquid, which is provided in the annular chamber, h) a connector cover in which the fluid-conducting connection between the feed pipe and the annular chamber and between the drain pipe and the outflow pipe chamber is disposed, which has a vent opening, i) a vent pipe connected to the vent opening of the borehole heat exchanger and comprising a vent valve spaced apart from the borehole heat exchanger, via which the annular chambers of the borehole heat exchanger can be vented, wherein the borehole heat exchangers in the borehole heat cycle are connected in series, and a heat transfer liquid can be conducted through the inflow pipes and the outflow pipes, and, in the process, the heat transfer takes place in each case between the heat transfer liquid and the ground soil at least through the inflow pipe, wherein the means for producing turbulence in the heat transfer liquid is formed from at least one turbulence-producing blade attached to a collar which is formed like a cylindrical pipe section and which, on a surface facing inside, corresponds to the shape of the outflow pipe, is disposed thereon in a displaceable manner for mounting in order to position the means for producing turbulence in the heat transfer liquid along the inner pipe of the borehole heat exchanger, and can be disposed in a slip-proof manner in the annular chamber. a) an inflow pipe having an inner surface of the inflow pipe facing into the inflow pipe and an outer surface of the inflow pipe facing towards the ground soil, b) an outflow pipe comprising an inner surface of the outflow pipe, which faces into the outflow pipe and encloses an outflow pipe chamber, and an outer surface of the outflow pipe pointing outwards away from the outflow pipe, c) an annular chamber, which is located within the inflow pipe and is horizontally delimited by the inner surface of the inflow pipe and the outer surface of the outflow pipe, d) a connecting portion, which interconnects the annular chamber and the outflow pipe chamber in a fluid-conducting manner and is disposed at a lower end of the borehole heat exchanger, e) a feed pipe, which is connected to the annular chamber in a fluid-conducting manner and is disposed at an upper end of the borehole heat exchanger, and f) a drain pipe, which is connected in a fluid-conducting manner to the outflow pipe chamber and is also disposed at an upper end of the borehole heat exchanger, g) at least one means for producing turbulence in the heat transfer liquid, which is provided in the annular chamber, h) a connector cover in which the fluid-conducting connection between the feed pipe and the annular chamber and between the drain pipe and the outflow pipe chamber is disposed, which has a vent opening, i) a vent pipe connected to the vent opening of the borehole heat exchanger and comprising a vent valve spaced apart from the borehole heat exchanger, via which the annular chambers of the borehole heat exchanger can be vented,