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Thermosiphon loop thermal collector for low-temperature waste heat recovery.

Author(s) : MATSUBARA K., MATSUDAIRA Y., KOURAKATA I.

Type of article: Article

Summary

This paper describes the thermal collector type loop thermosiphon for low-temperature waste heat recovery. Water is used as the working fluid for heat transport at temperatures 100 °C and higher. The loop thermosiphon comprises of a thermal receiver, a condenser, and riser and downcomer tubes. The thermal receiver is made of a cupper plate brazed by meandering heat transfer tube. This receiver collects the thermal radiation from the electric heater at the heat transfer area of 1000 cm2 (40 cm × 25 cm), and transports the heat by vaporization of water to the condenser having heat transfer area of 62 cm2. In the no inclination mode, the thermosiphon is upright so that the thermal receiver and the condenser are placed vertically. In this mode, the effective thermal conductivity exceeds 60 kW/(m K) when the thermal receiver temperature was higher than 125 °C for the water filling ratio a = 30–70%. Although the effective thermal conductivity is deteriorated for the higher filling ratio a = 80% and 90%, the effects from the filling ratio are tiny for a = 30–70%. The experimental tests were also made for the negatively inclined mode where the inlet and exit ports of the receiver were directed downward and for the positively inclined modes where they were directed upward. The tests revealed that the negative inclination almost halted the heat transport. However, the tests also indicated that the positive inclination showed the performance comparable to the no inclination mode for the cases up to the inclination angle 90°.

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