Experimental study of nucleate boiling on surface of cooling channel of silicon crystal

ABSTRACTHeat transfer experiments were carried out to investigate the boiling characteristics of LN2 in a narrow channel madeby silicon crystal, which simulated one of the cooling channels of first crystal of DXM. Heat transfer coefficients in nucleateboiling and DM3 heat fluxs in the narrow channel were obtained and compared with some existing correlations. These valueswill be used in the numerical simulation to calculate the thermal distortion of the crystal more accurately.LINTRODUCTIONX—ray irradiation ofthe optics causes thermal distortion of the optics. Excessive thermal distortion of the optics harmesthe performance of the optics. As for the first crystals of double crystal monochromators (DXM), which will be installed inthe beamlines of large scale SR facilities, it is often reported that a fall in the intensity of X—rays will become noticeablebecause these optics will be exposed by strong X—ray radiated from insertion device.A lot of effort has been made by scientists and engineers to decrease the thermal distortion of these crystals. Twopossible solutions which are receiving wide attention both involve the selection of coolants for the cooling system. One solutionis to use cryogen as a coolant for ciystals 1)