Currently, the waste heat for one year in Japan is equivalent to about 1% of the total power generation, and in order to effectively utilize such waste heat, heat is recovered with high efficiency using a heat transfer tube, etc. It is expected that it will be converted into energy and used.

　It has been known that the heat transfer performance can be improved by using a porous body for the heat transfer tube and further, by sintering the heat transfer tube and the porous medium.Therefore, the researchers created a special porous heat transfer tube in which a fiber made of the same material was filled in an aluminum tube, and conducted a comparative experiment with a normal aluminum heat transfer tube.

　As a result of the experiment, in a normal heat transfer tube with a length of 150 mm, when the inlet temperature is set to 200 ° C and the circumference of the heat transfer tube is cooled to 2 ° C, hot air of about 130 ° C comes out from the outlet of the heat transfer tube. On the other hand, a heat transfer tube filled with 20 mm of fiber at a space ratio of only 25% discharged cold air at 2 ° C.By filling the aluminum fiber body and shortening the length of the heat transfer tube, an astonishing temperature difference of about 200 ° C was created between the inlet and outlet of the heat transfer tube, and heat recovery with almost 100% loss was successful. become.This heat exchange efficiency is said to be about 20 times higher than before.

　Since both the tube and the fiber are made of aluminum, it is easy to develop with the same material, and it also has the advantage of being lightweight and easy to carry.Since the installation cost is expected to be significantly reduced, it can be expected to be used for waste heat from factories that are currently discarded, and for cold heat recovery of LNG (liquefied natural gas) and liquefied hydrogen that are transported at about -200 ° C.

　In this study, by repeating the experiment by changing the inner diameter of the heat transfer tube, the thickness and length of the aluminum fiber body, and the space ratio, the frictional pressure loss required for designing the mechanical equipment using this heat transfer tube is estimated. I also succeeded in guiding the arrangement ceremony.It is expected to become a technology that greatly contributes to the realization of a carbon-neutral and sustainable society.

Paper information:[Applied Thermal Engineering] Experimental investigation into the heat transfer and pressure drop performance of sintered high porosity media