Abstract: A tube bundle heat exchanger has tubes which are held at each side in tube plates or oval-tube collecting-tube plates and are connected to these in each case by means of a weld seam. The connection of the tubes to the inlet-side tube plate or oval-tube collecting-tube plate is formed in each case by means of a conical and/or trumpet-shaped transition piece. The cross section of the transition piece reduces as viewed in the gas flow direction in such a way that the inlet-side end, as viewed in the gas flow direction, of the transition piece is connected in a butt joint to the tube plate or oval-tube collecting-tube plate. The inner and outer contours of the transition piece and of the welded connection region are formed without gaps and corners to the tube plate or oval tube collecting-tube plate and so as to be straight and/or with a radius, measured from the outer contour, of at least 5 mm.

Abstract: A rotary regenerative heat exchanger (1) employs heat transfer elements (100) shaped to include notches (150), which provide spacing between adjacent elements (100), and undulations (corrugations) (165,185) in the sections between the notches 150. The elements (100) described herein include undulations (165,185) that differ in height and/or width.

Abstract: A method for welding two or more conduits includes aligning end portions thereof in an abutting relationship to define a gap. The method includes performing a spatter free root weld along the gap to configure a root layer while the inner circumferential surface side is unobstructed. After the root weld is complete, an outward thrust is applied along the inner circumferential surfaces of the conduits. During the application of the outward thrust, a filler weld is performed along the gap to fill the gap and to facilitate shrinkage of the filler and root weld materials longitudinally and radially outward while preventing pressing out of the filler and root weld materials radially inward of the inner circumferential surface.

Abstract: Disclosed is a heat transfer assembly for a rotary regenerative preheater. The heat transfer assembly, includes, a plurality of heat transfer elements stacked in spaced relationship to each other in a manner such that each notch from a plurality of notches of one of the heat transfer element rests on respective flat sections from a plurality of flat sections of the adjacent heat transfer elements to configure a plurality of closed channels, each isolated from the other, wherein each of the channels has a configuration in a manner such that each of corrugation sections from a plurality of corrugation sections of one of the heat transfer elements faces respective undulation sections from a plurality of undulation sections of the adjacent heat transfer elements.

Abstract: A tube bundle heat exchanger includes tubes channeling a gas flow and a pressure shell enclosing the tubes channeling a coolant flow. First and second nozzles are disposed at a rear end of the pressure shell and third and fourth nozzles are disposed at a front end of the pressure shell. A feed pipe includes a first three-way valve and a drain pipe includes a second three-way valve. A first bypass pipe is connected to the first three-way valve and the third nozzle, a second bypass pipe is connected to the first three-way valve and the first nozzle, a third bypass pipe is connected to the second three-way valve and the second nozzle, and a fourth bypass pipe is connected to the second three-way valve and the fourth nozzle. One of the three-way valves is controllable.