A method for determining a stiffness of a tube bundle heat exchanger. The heat exchanger has a core tube and a plurality of coil tubes coiled around the core tube to form a tube bundle having a plurality of coil layers at a respective layer coiling angle. The method determines a geometric strength parameter for a coil layer, the strength parameter being an area ratio of a coil-tube cross-sectional area to a cell cross-sectional area resulting from the axial spacing of the coil tubes and an outer diameter of the coil tubes. The area ratio is corrected by a correction factor taking the orientation of the coil tubes of the coil layer in relation to the force of gravity acting on the coil tubes into consideration. The stiffness of the respective coil layer is determined from the corrected area ratio and a modulus of elasticity of the coil-tube material.

A method for determining a stiffness of a tube bundle heat exchanger. The heat exchanger has a core tube and a plurality of coil tubes coiled around the core tube to form a tube bundle having a plurality of coil layers at a respective layer coiling angle. The method determines a geometric strength parameter for a coil layer, the strength parameter being an area ratio of a coil-tube cross-sectional area to a cell cross-sectional area resulting from the axial spacing of the coil tubes and an outer diameter of the coil tubes. The area ratio is corrected by a correction factor taking the orientation of the coil tubes of the coil layer in relation to the force of gravity acting on the coil tubes into consideration. The stiffness of the respective coil layer is determined from the corrected area ratio and a modulus of elasticity of the coil-tube material.

The present invention discloses a manufacturing method of an unequal-torque coil spring and a manufacturing machine thereof for a curtain spring motor, providing a feedback torque that corresponds to an actual requirement from different stages in a curtain-folding working process, so that when the curtain is folded back, the torque can be used to stabilize the speed of folding back the curtain, and the lower beam of the curtain can be fixed at any heights as the curtain is lowered.

The present invention discloses a manufacturing method of an unequal-torque coil spring and a manufacturing machine thereof for a curtain spring motor, providing a feedback torque that corresponds to an actual requirement from different stages in a curtain-folding working process, so that when the curtain is folded back, the torque can be used to stabilize the speed of folding back the curtain, and the lower beam of the curtain can be fixed at any heights as the curtain is lowered.

A machine (1) for working a ribbon-shaped element (T1, T2, T2) is described, comprising at least one cutting station (2) crossed by the ribbon-shaped element (T1, T2, T2), guiding means (3, 4) adapted to position and drag the ribbon-shaped element (T1, T2, T2) onto at least one fixed plane (PI) of the cutting station (2) keeping an edge of the ribbon-shaped element (T1, T2, T2) tangent to a fixed point (A1) of the fixed plane (Pi); at least one of the guiding means (3, 4) rests onto an arm (31) free of rotating with respect to a fixed axis (33); the fixed axis (33) is at the same distance with respect to the cutting station (2) and the at least one of the guiding means (3, 4).

A machine (1) for working a ribbon-shaped element (T1, T2, T2) is described, comprising at least one cutting station (2) crossed by the ribbon-shaped element (T1, T2, T2), guiding means (3, 4) adapted to position and drag the ribbon-shaped element (T1, T2, T2) onto at least one fixed plane (PI) of the cutting station (2) keeping an edge of the ribbon-shaped element (T1, T2, T2) tangent to a fixed point (A1) of the fixed plane (Pi); at least one of the guiding means (3, 4) rests onto an arm (31) free of rotating with respect to a fixed axis (33); the fixed axis (33) is at the same distance with respect to the cutting station (2) and the at least one of the guiding means (3, 4).

A counterflow heat transfer system comprises a heat exchanger and a flow controller arranged to convey a first fluid through the heat exchanger in a first flow direction and a second fluid through the heat exchanger in a second counterflow direction. The heat exchanger comprises at least one first thermally conductive tube conveying the first fluid and at least one second thermally conductive tube conveying the second fluid. The first and second tubes are wound around one another and in contact with one another in an entwined tubular arrangement.

A counterflow heat transfer system comprises a heat exchanger and a flow controller arranged to convey a first fluid through the heat exchanger in a first flow direction and a second fluid through the heat exchanger in a second counterflow direction. The heat exchanger comprises at least one first thermally conductive tube conveying the first fluid and at least one second thermally conductive tube conveying the second fluid. The first and second tubes are wound around one another and in contact with one another in an entwined tubular arrangement.

The objective of the present invention is to provide an apparatus for manufacturing an elbow-shaped duct, comprising: a main body obliquely provided at the upper part thereof; a duct movement guiding part provided to rotate and vertically move; a duct vane forming part including forming jigs symmetrically formed and respectively slid in the opposite directions to be coupled to and separated from each other; a duct vane coupling part including a duct fixing member for guiding the fixing of a duct and a duct vane pressing member for coupling upper and lower vanes of the duct; and a rotary driving part rotatably provided inside the main body, and including an eccentric rotary roller having, at the upper part thereof, a cutting roller for cutting the duct and a forming roller for forming the upper and lower vanes of the duct, thereby enabling the duct to be manufactured, by loading the cylindrical duct on the movement guiding part, as is, and simultaneously performing cutting and forming to correspond to an elbow shape, and thus remarkably reduces manufacturing time.

The objective of the present invention is to provide an apparatus for manufacturing an elbow-shaped duct, comprising: a main body obliquely provided at the upper part thereof; a duct movement guiding part provided to rotate and vertically move; a duct vane forming part including forming jigs symmetrically formed and respectively slid in the opposite directions to be coupled to and separated from each other; a duct vane coupling part including a duct fixing member for guiding the fixing of a duct and a duct vane pressing member for coupling upper and lower vanes of the duct; and a rotary driving part rotatably provided inside the main body, and including an eccentric rotary roller having, at the upper part thereof, a cutting roller for cutting the duct and a forming roller for forming the upper and lower vanes of the duct, thereby enabling the duct to be manufactured, by loading the cylindrical duct on the movement guiding part, as is, and simultaneously performing cutting and forming to correspond to an elbow shape, and thus remarkably reduces manufacturing time.