Matsushita Electric Industrial Co., Ltd.

Toshiaki Andoh

Shoichi Yokoyama

Hitoshi Motegi

Kaoru Ishida

Hiroaki Kosugi

Makoto Sakakura

Takeshi Miura

Osamu Aoyagi

A high-frequency oscillating circuit that is not degraded by external electromagnetic interference. The high-frequency oscillating circuit includes first and second oscillating transistors wherein the bases are connected together directly or via a capacitor having a sufficiently low impedance at an oscillating frequency, and wherein a differential signal output is obtained between the emitters of the first and second oscillating transistors. Also provided is a resonating circuit formed in a module and a separate negative-resistance-generating circuit formed on an integrated circuit for achieving an oscillator that has a high Q factor and a high C/N ratio.

High-frequency oscillating circuit

The fin-tube heat exchanger includes a group of fins arranged parallel to one another at predetermined intervals; cylindrical fin collars formed on each fin at a predetermined column pitch and a predetermined row pitch; and heat transfer tubes extending through the respective fin collars and secured thereto in intimate contact therewith. Seat portions are formed on each fin around the fin collars. A curved protuberance of a generally angular cross-section is formed on the fin adjacent to an outer periphery of each of the seat portions, which has a ridge line of an arcuate or circular shape arranged in concentric relation to the associated fin collar. A plurality of straight protuberances of a generally angular cross-section are formed on each fin adjacent to outer peripheries of the respective seat portions between any two adjacent rows of the fin collars. With this structure, heat transfer performance is improved by a turbulence promoting effect of the straight protuberances. Also an air flow is guided into slip streams behind the heat transfer tubes by the curved protuberances, thereby reducing stagnation zones and increasing the effectively used heat transfer area to improve heat transfer performance.

Fin-tube heat exchanger

A plate fin heat exchanger has a group of fins arranged at predetermined intervals so that an air current flows between the respective fins and a group of tubes respectively inserted into and joined to the cylindrical fin collars which are formed in the fin group with a predetermined longitudinal pitch and lateral pitch. Elliptical seats each having a longitudinally extending short axis are respectively provided around the fin collars on the surface of each of the fins, and seat-side ridge portions are respectively formed along the outer peripheries of the seats. A plurality of fin-side ridge portions, each having a longitudinally linearly extending ridge and substantially the same height as that of each of the seat-side ridge portions, are formed in each line of the fin collars outside the seat-side ridge portions on each of the fins. The turbulence promoting effect of the fin-side ridge portions, each having a longitudinally linearly extending ridge, improves the heat transfer efficiency. In addition, the highest portions of the seat-side ridge portions formed between the fin-side ridge portions cause the air current to be controlled by the wake in the tubes so as to decrease the stagnation region, thereby increasing the heat transfer effective area and improving the heat transfer efficiency.

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Otsu, Japan

Toshiaki Andoh