An air filter has a filter housing. A first flat filter element and a second flat filter element, each having a filter medium body with an inflow surface and an outflow surface, are arranged in the filter housing. A flow guiding device selectively guides an air flow to be filtered through the first flat filter element and the second flat filter element in series or at least partially past the second flat filter element. The outflow surface of the first flat filter element and the inflow surface of the second flat filter element are spaced apart from each other and form a widening bypass channel. The filter medium body of at least one of the first flat filter element and the second flat filter element has an intrinsically changing height and has a reduced height in a region of a larger width of the bypass channel.

A system for biological methane production and removing carbon dioxide from the methane comprises (a) a primary anaerobic digester adapted and arranged to generate a gaseous mixture comprising methane and carbon dioxide from organic materials; (b) an electrochemical reactor comprising at least one reactor cell including an anode spaced from a cathode by a porous ion exchange resin wafer with a cation exchange membrane between the anode and the resin wafer and a bipolar ion exchange membrane between the cathode and the resin wafer; the electrochemical reactor being adapted and arranged to capture gaseous carbon dioxide within the resin wafer as aqueous bicarbonate, and to electrochemically generate hydrogen gas at the cathode; and (c) a hydrogenotrophic methanogenesis bioreactor adapted and arranged to convert the bicarbonate and hydrogen from the electrochemical reactor to methane. An electrochemical reactor and a method for producing methane with reduced carbon dioxide content also are described.

The invention provides a membrane filter assembly for analytical sample systems, and a sample system block assembly having a built-in membrane filter assembly. The filter assembly has a housing having recessed inner face having non-uniform depth, and a cover member having a plurality of concentric grooves and a radially oriented shallow groove crossing the concentric grooves, wherein the grooves each have wider top than the bottom.

A filter element for filtering a fluid has two or more axially extending filter medium bodies arranged to be sequentially flowed through radially and including a first and a second filter medium body. The first filter medium body has an outer diameter smaller than an inner diameter of the second filter medium body, is arranged radially inside the second filter medium body, and has a section projecting axially away from the second filter medium body. A casing is arranged at an outer wall surface of the projecting section and extends at least partially circumferentially around the outer wall surface. The casing fluid-impermeably closes at least temporarily the outer wall surface. The first filter medium body is a particle filter and the second filter medium body is an adsorption filter, or vice versa. A filter system is provided with such a filter element for filtering a fluid.

A filter device of a motor vehicle may include a step filter, two flow paths, and a plurality of adjustable air flaps. The step filter may include a plurality of individual filter elements arranged fluidically in series. A first flow path may extend through at least two individual filter elements. A second flow path may extend through a number of the plurality of individual filter elements which, compared to a number of the plurality of individual filter elements through which the first flow path extends, may be reduced by at least one single individual filter element. The plurality of adjustable air flaps may be arranged at least one of upstream and downstream of the step filter. At least one air stream may be guidable through the step filter along at least one of the first flow path and the second flow path via the plurality of adjustable air flaps.

A filter element for filtering a fluid has a frame and at least one filter bellows arranged in the frame and provided with a first areal inflow surface for a first fluid flow and at least one second inflow surface for a second fluid flow separate from the first fluid flow. The second inflow surface is separate from the first areal inflow surface. A flow channel is provided to guide the second fluid flow and has a raw-side flow channel section arranged within the frame. A filter system provided with a filter housing is provided with such a filter element arranged exchangeably in the filter housing between a raw side and a clean side. The filter housing has a first inlet for the first fluid flow communicating with the first inflow surface and at least a second inlet for the second fluid flow communicating with the second inflow surface.

An indirect evaporative cooling apparatus includes a housing, a heat exchanger core, a bypass valve, a filter, an indoor fan, and an outdoor fan. The heat exchanger core is in the housing. A first space, a second space, a third space, and a fourth space are formed by the heat exchanger core and the housing, and a first air vent, a second air vent, a third air vent, and a fourth air vent are disposed in the housing. The first space and the second space are connected by using the heat exchanger core to constitute an indoor circulation air duct, the third space and the fourth space are connected by using the heat exchanger core to constitute an outdoor circulation air duct.

The present invention provides a multi-stage coalescing filter for separating coalesced liquid from an aerosol-containing gas stream. The multi-stage coalescing filter includes an end cap having a chamber formed within and a plurality of coaxial, nested, tubular filter elements supported upright on the end cap. Pairs of successive filter elements are spaced from each other such that the end cap between pairs of successive filter elements forms respective annular sumps for collection of coalesced liquid separated by the filter elements from the aerosol-containing gas stream as it passes radially through the nested filter elements. The chamber has one or more inlets in fluid communication with the or each sump for receiving the coalesced liquid from the sump, and further has one or more outlets for guiding the received coalesced liquid out of the filter. The chamber houses a porous element which is configured to saturate under contact with the received coalesced liquid so as to allow the received coalesced liquid to flow through the porous element to the outlet while simultaneously preventing the aerosol-containing gas stream from passing through the chamber to bypass the nested filter elements.