Abstract: A hammer 28 is provided for a material size-reducing machine of the type including a rotor on which the hammer is individually pivotally mounted. The hammer 28 includes a mounting end 36 having a throughbore for receiving a pivot pin therethrough in connection with the pivot mounting of the hammer on the rotor, an extending portion 40 with the center of mass CGM located therein. The extending portion has a non-linear body portion 44 and a linear body portion 46 with the linear body portion 46 being inclined in a direction opposite to the rotation direction at an angle between 5 to 45 degrees as measured relative to a line RFL extending through the center of the pivot pin and the center of mass CGM of the hammer.

Abstract: The thermal performance of the heat transfer element assemblies for rotary regenerative air preheaters is enhanced to provide a desired level of heat transfer and pressure drop with a reduced weight. The heat transfer plates in the assemblies have spaced apart dimples for maintaining plate spacing and oblique undulations with the undulations on adjacent plates preferably extending at opposite oblique angles. The dimples may be on every other plate and alternate between the two sides of the plates or they may be on every plate and all extend to the same side.

Abstract: Heat transfer elements for rotary regenerative heat exchangers are formed with spacing ridges or notches having flow-disrupting indentations in the peaks of the notches formed at selected intervals to project into the flow channels. These projections interrupt the boundary layer and cause turbulence and mixing to enhance the heat transfer. Various methods of forming the indentations are disclosed.