Abstract: A heat exchanger, illustratively utilized in a fuel-fired pool heater, circumscribes a burner operative to discharge hot combustion gases outwardly through the heat exchanger. The heat exchanger has a tube portion helically coiled about an axis, with a series of heat transfer fins circumscribing the tube portion and spaced apart along it length. The fins on longitudinally adjacent pairs of coils of the tubing have nested facing edge portions which collectively form a seal area that coils between the tubing portion adjacent coil pairs in axially spaced relationships therewith, the seal area substantially impeding combustion gas flow therethrough in a direction generally transverse to the axis of the heat exchanger. Additionally, the fins have deformed laterally outer portions that define a coiled, circumferentially spaced series of restricted combustion gas outlets in substantial axial alignment with the helically coiled tube portion.

Abstract: A heat exchanger, illustratively utilized in a fuel-fired pool heater, circumscribes a burner operative to discharge hot combustion gases outwardly through the heat exchanger. The heat exchanger has a tube portion helically coiled about an axis, with a series of heat transfer fins circumscribing the tube portion and spaced apart along it length. The fins on longitudinally adjacent pairs of coils of the tubing have nested facing edge portions which collectively form a seal area that coils between the tubing portion adjacent coil pairs in axially spaced relationships therewith, the seal area substantially impeding combustion gas flow therethrough in a direction generally transverse to the axis of the heat exchanger. Additionally, the fins have deformed laterally outer portions that define a coiled, circumferentially spaced series of restricted combustion gas outlets in substantial axial alignment with the helically coiled tube portion.

Abstract: An infrared gas analyzer includes an infrared source for emitting infrared energy, a sample cell for gases to be analyzed in the path of infrared energy emitted by the source and an assembly having first and second detectors also in the path of infrared energy and a third detector out of the path of infrared energy, mounted within the assembly and in close thermal proximity to each other and being responsive to impinging infrared energy to produce an electrical response. All detectors are sandwiched between a base and a single window that overlies them. The analyzer further includes a narrow band filter corresponding to an absorption wavelength band for a gas of interest and a narrow band reference filter corresponding to a reference wavelength band. Each of the narrow band filters are positioned outside the assembly and between the assembly and the source in the path of infrared energy.

Abstract: An infrared spectrophotometer is described wherein an infrared source is provided for emitting infrared energy. A sample cell is provided for containing gases to be analyzed and is positioned in the path of infrared energy emitted by the source. A detector assembly includes first, second and third thermopile detectors mounted in thermal proximity to each other and being responsive to impinging infrared energy to produce an electrical response. The first and second detectors are positioned in the path of infrared energy emitted by the source and the third detector is positioned out of the path of infrared energy emitted by the source. The spectrophotometer further comprises a narrow band filter corresponding to an absorption wavelength band for a gas of interest and a narrow band reference filter corresponding to a reference wavelength band.

Abstract: Very generally, the gas analyzer of the invention includes a source of infrared energy, a sample cell for containing an analyte gas mixture positioned in the path of infrared energy, and a monochrometer including a movable diffraction grating for producing a beam of infrared energy wherein the constituent wavelengths are spetrally separated. The device also includes a wide band interference filter for transmitting a predetermined wavelength band spanning the characteristic absorption wavelength of each of a plurality of constituent gases in the analyte gas mixture. A detector positioned to receive radiation passing through the filter produces an electrical response related to the infrared energy impinging thereon. The monochrometer includes provision for moving the diffraction grating to sequentially cause infrared energy of different wavelengths to impinge upon the detector, and for intermittently causing infrared energy directed toward the detector from the source to be blocked by the interference filter.

Abstract: A non-dispersive infrared (NDIR) multi-gas analyzer has an optical element that is positioned with respect to the axis of incident IR radiation such that it passes nearly all of the IR energy within a narrow band pass to one detector and reflects nearly all of the IR energy outside the narrow band pass to another detector. Thus, the optical element simultaneously functions both as a narrow band pass filter and a beam splitter, which transmits nearly all the IR energy within a band pass and reflects nearly all the IR energy outside the band pass. Additionally, the separation of the incoming energy can be achieved without an extended roll off. This allows using a reference transmission band that is very close to the absorption band of the gases of interest. It more specifically allows using a reference transmission band that is located between the absorption bands for hydrocarbons and carbon dioxide in an infrared analyzer that uses beam splitters.

Abstract: In the embodiments described in the specification, a stabilized, pigmented hot melt ink contains a thermoplastic vehicle, a coloring pigment, and a dispersion-stabilizing agent to inhibit settling or agglomeration of the pigment when the ink is molten comprising 1.5 to 20 weight percent of a nitrogen-modified acrylate polymer. A preferred dispersion-stabilizing agent is the nitrogen-modified methacrylate polymer marketed by Rohm and Haas as Plexol 1525.

Abstract: A non-dispersive infrared gas analyzer is disclosed that accurately measures the concentration levels of a plurality of gases within a gas mixture. The analyzer includes first and second sample cells and is utilized advantageously for the measurement of NO.sub.x and hydrocarbon gas present in the exhaust of an automobile engine. The gas mixture of the exhaust is chilled before entering the first sample cell to remove a substantial amount of the water vapor from that sample cell to facilitate measurement of the NO.sub.x gas. The second sample cell receives the gas mixtue in an unchilled state to allow for accurate measurement of the hydrocarbon gas. The analyzer includes processors which are utilized to further correct the NO.sub.x measurement and which also interact with each other to provide an output data stream that is representative of the concentration levels of the gases that are being analyzed.

Abstract: A gas analyzer is described comprising a sample cell for containing a gas mixture to be analyzed, a source for producing and directing infrared energy through the sample cell, a rotary filter wheel having at least one filter thereon for passing infrared energy limited to a wavelength band within the characteristic absorption band of a predetermined gas and having a dark level region substantially opaque to infrared energy, a drive for supporting and rotating the filter wheel to successively interpose the filter and the dark level region between the source and the sample cell in the path of the infrared energy directed by the source, a detector for detecting infrared energy passing through the sample cell and producing an electrical signal representative thereof, and a signal processor connected to the detector for producing an output indicating the concentration of the predetermined gas in the sample cell by comparing the electrical signals produced by the detector with the filter positioned in the infrared e

Abstract: Pulse modulated infrared energy is directed through a sample cell containing a gas mixture. The gas mixture may include a selected one of a plurality of gases. Each gas exhibits a characteristic absorption in the infrared wavelengths. A detector responsive to infrared energy at a preselected wavelength develops an AC signal having an amplitude proportional to the infrared energy passing through the sample cell at the preselected wavelength and having a frequency corresponding to the preselected pulse modulation frequency. The preselected wavelength is common to the absorption characteristic of each of said gases. The AC signal is processed to develop a DC signal having an amplitude determined from the AC signal. The DC signal is applied to an amplifier having a variable gain feedback which provides a plurality of gain steps. Each gain step is associated with a different one of the gases a single surrogate gas may be used to calibrate each gain step.

Abstract: A gas analyzer of the non-dispersive infrared type is described. An infrared beam passing through a sample cell containing a gas mixture to be analyzed is detected. The resulting electrical signals are processed to produce an output indicating the concentration of the constituents of the gas mixture in the sample cell. The gas analyzer includes provision for temperature stabilizing both a rotary filter wheel and the detector, and for compensating the output of the signal processor for variation in the absorption characteristics of gas with temperature. The emissivity characteristic of the infrared energy source substantially compensates for wavelength dependence of the detector response. The motor drive for the rotary filter wheel is servo-controlled in accordance with synchronizing pulses developed directly from the detector output.