Closed-ended oscillating heat-pipe (CEOHP) air-preheater for energy thrift in a dryer

The CEOHP air-preheater consisted of two main parts, i.e. the rectangular house casing and the CEOHP. The house casing was designed to be suitable for the CEOHP. The inside house casing divided the CEOHP into three parts, i.e. the evaporator, the adiabatic section and condenser section. The CEOHP air-preheater design employed copper tubes: thirty-two sets of capillary tubes with an inner diameter of 0.002 m, an evaporator and a condenser length of 0.19 m, and each of which has eight meandering turns. The evaporator section was heated by hot-gas, while the condenser section was cooled by fresh air. In the experiment, the hot-gas temperature was 60, 70 or 80 °C with the hot-gas velocity of 3.3 m/s. The fresh-air temperature was 30 °C. Water and R123 was used as the working fluid with a filling ratio of 50%. It was found that, as the hot-gas temperature increases from 60 to 80 °C, the thermal effectiveness slightly increases. If the working fluid changes from water to R123, the thermal effectiveness slightly increases. The designed CEOHP air-preheater achieves energy thrift.