The receiver behavior of parabolic troughs in direct steam generation (DSG) has been studied under different experimental conditions. When cool water was fed into steel receiver pipes (empty set = 2.54 cm), the pipes deflected. This bend advanced like a wave from the inlet to the outlet end, having a deflection of about 6.5 cm at the center of each section (2.90 m long) in the parabolic trough module (14.5 m long and 2.5 m aperture). This phenomenon was due to a temperature difference of about 50 degrees C in the circumferential direction. When the steel receiver pipe was changed to a copper receiver, We circumferential temperature difference was practically eliminated and no appreciable bending of the pipe was observed, hence DSG was obtained without these problems.