Abstract: A gas cooling device capable of efficiently cooling a gas such as an EGR gas, etc. is provided. A multiplicity of cooling pipes perpendicularly intersecting a gas flow direction in a gas pipe for a gas such as an EGR gas, etc. are provided to extend through an outer peripheral wall of the gas pipe, a cooling jacket is provided on an outer surface of the gas pipe on both sides of a group of the cooling medium pipes in an axial direction, or on the entire outer surface of the gas pipe, and the gas in the gas pipe is cooled by a cooling medium flowing through the cooling pipes.

Abstract: A heat exchanger tube has an inner peripheral surface serving as an exhaust gas flow path with a flat cross-sectional shape. A thin structure is incorporated in the heat exchanger tube and has a substantially rectangular channel-shaped waveform in cross section. The corrugated fin structure has a curved surface forming waveform meandering with a predetermined wavelength in the lengthwise direction. The wave width of the channel-shaped waveform is H, the wavelength of the waveform meandering in the lengthwise direction is L and the amplitude of the waveform meandering in the lengthwise direction is A. The heat exchanger tube is formed so that H/L is set at 0.17 to 0.20 and the ration (G/H) of a gap G determined by H?A to H is set at ?0.21 to 0.19.

Abstract: A fin structure, a heat-transfer tube and a heat exchanger are formed of plate fins housed in a heat-transfer tube and have an excellent cooling efficiency by making the distribution and flow velocity of a flow uniform and by promoting an efficient heat-exchanging action. The fin structure includes plate fins housed in a heat-transfer tube and having a square section and a free shape in the longitudinal direction for dividing a passage for a fluid composed of a cooled medium or a cooling medium to flow in the heat-transfer tube, into a plurality of small passages. In the fin structure, notches, through holes, raised portions, ridges and/or troughs are formed in the sides or the upper or lower walls of the plate fins. The heat-transfer tube has the fin structure housed therein. The heat exchanger has the heat-transfer tube assembled therein.

Abstract: A heat exchanger tube has an inner peripheral surface serving as an exhaust gas flow path with a flat cross-sectional shape. A thin structure is incorporated in the heat exchanger tube and has a substantially rectangular channel-shaped waveform in cross section. The corrugated fin structure has a curved surface forming waveform meandering with a predetermined wavelength in the lengthwise direction. The wave width of the channel-shaped waveform is H, the wavelength of the waveform meandering in the lengthwise direction is L and the amplitude of the waveform meandering in the lengthwise direction is A. The heat exchanger tube is formed so that H/L is set at 0.17 to 0.20 and the ration (G/H) of a gap G determined by H-A to H is set at ?0.21 to 0.19.

Abstract: A fin structure, a heat-transfer tube and a heat exchanger are formed of plate fins housed in a heat-transfer tube and have an excellent cooling efficiency by making the distribution and flow velocity of a flow uniform and by promoting an efficient heat-exchanging action. The fin structure includes plate fins housed in a heat-transfer tube and having a square section and a free shape in the longitudinal direction for dividing a passage for a fluid composed of a cooled medium or a cooling medium to flow in the heat-transfer tube, into a plurality of small passages. In the fin structure, notches, through holes, raised portions, ridges and/or troughs are formed in the sides or the upper or lower walls of the plate fins. The heat-transfer tube has the fin structure housed therein. The heat exchanger has the heat-transfer tube assembled therein.

Abstract: A fluid agitating plate fin is mounted to a heat exchanger tube to agitate a cooling fluid and to create a turbulent flow. Edges of the plate fins are opposed to each other and the opposed butted blade edges cross each other.

Abstract: A gas cooling device capable of efficiently cooling a gas such as an EGR gas, etc. is provided. A multiplicity of cooling pipes perpendicularly intersecting a gas flow direction in a gas pipe for a gas such as an EGR gas, etc. are provided to extend through an outer peripheral wall of the gas pipe, a cooling jacket is provided on an outer surface of the gas pipe on both sides of a group of the cooling medium pipes in an axial direction, or on the entire outer surface of the gas pipe, and the gas in the gas pipe is cooled by a cooling medium flowing through the cooling pipes.

Abstract: A multi-frequency signal receiver comprising an automatic gain control circuit for adjusting the level of the multi-frequency signal, a plurality of bandpass filters for separating the output from the automatic gain control circuit into respective frequency signals, the bandpass filters being grouped into two groups, two detectors respectively detecting the outputs from the two groups of the bandpass filters for producing output voltages respectively proportional to the outputs from the two groups, a recognition circuit for producing an output when the level of the sum of the outputs from the two detectors exceeds a predetermined level, and a plurality of gate circuits respectively responsive to the output from the recognition circuit for passing the outputs from the plurality of bandpass filters.