Abstract: A unitary heat exchanger device, for the transfer of total heat, comprising air-to-air heat transfer means and configured such that air may pass there through. The heat transfer means comprisesan air-to-air water vapor transfer element andan air-to-air sensible heat transfer element,the exchanger elements being in air communication with each other. The device may be used in ventilation systems which replace air exhausted from the interior of a building with fresh outside air; the use of the device under cold weather conditions may avoid or attenuate the need for using a defrost mechanism to defrost the device.

Abstract: The invention relates to a method for fabricating a piece of structural steel that includes thermal or thermomechanical treatment steps that could ordinarily lower the fatigue strength and shock and impact resistance of the steel piece. In the method of the invention a workpiece of microalloy steel is fabricated containing the following elements in the mounts indicated and having a bainitic structure:______________________________________ C 0.05-0.5 wt. % Mo 0-0.5 wt. % Mn 1-2 wt. % V 0-0.30 wt. % Si 0.05-1.5 wt. % B 0-0.010 wt. % Cr 0.1-1 wt. % Ti 0-0.030 wt. % Nb 0-0.1 wt. % ______________________________________The workpiece is then subjected to a treatment that includes a heating stage wherein at least a part of said piece is subjected to a temperature in the range 500.degree.-900.degree. C., followed by a cooling stage in which at least the part of the piece is subjected to cooling at a rate greater than 500.degree. C./hr.

Abstract: The present invention relates to an apparatus for defrostable ventilation systems which include an element for the transfer of heat from warm exhaust air (taken from inside a building) to cooler exterior fresh air which is drawn into the building, the system using warm interior air as defrost air for defrosting the system during cool weather. The present invention in particular provides an apparatus whereby, during a defrost cycle, the interior defrost air may circulate through both of the fresh air and exhaust air paths for delivery back into the building, i.e. the warm interior air may be confined to circulate from the interior of the building into the ventilation apparatus and back to the interior of the building. The apparatus can thus use interior air as defrost air while diminishing or avoiding the creation of a negative air pressure in the building.