A fuel-fired heating appliance comprises a burner and a first housing adjacent the burner so that an interior of the first housing receives combustion gasses from combustion at the burner. A heat exchanger defines a second housing with an inlet proximate an outlet of the first housing so that the inlet of the second housing receives combustion gasses from the outlet of the first housing, and wherein the first and second housings attach at an interface. A barrier extends within, and across an interface between, the outlet of the first housing and the inlet of the second housing and defines a thermal resistance that inhibits heat transfer from the combustion gasses to the interface.

A tube bundle heat exchanger having a straight-tube configuration, comprising a pressure vessel, a straight-tube bundle comprising a number of straight tubes which are arranged so as to be guided through an inlet tubesheet and an outlet tubesheet and to extend through the interior space of the pressure vessel. A cooler for gas turbine cooling air comprising a tube bundle heat exchanger, a gas turbine power plant and a gas and steam turbine power plant comprising a cooler for gas turbine cooling air according to the invention, as well as a process gas cooler and a method for the cooling of cooling air using such a cooler for gas turbine cooling air.

In one aspect, a tubular membrane assembly is provided for a heat exchanger. The tubular membrane assembly includes a header having a header body, a tubular membrane, and a fitting connecting the tubular membrane to the header body. The fitting is configured to form a fluid tight connection between the fitting and the tubular membrane. The tubular membrane assembly further includes potting of the header keeping the tubular membrane connected to the fitting.