Improvement on Heat Release Performance of Direct-contact Heat Exchanger Using Phase Change Material for Recovery of Low Temperature Exhaust Heat

Abstract

Latent heat storage using a phase change material (PCM) is a promising method for utilizing the exhaust heat from steelworks. The purpose of this study was to improve the heat release performance of a direct-contact heat exchanger using a PCM and heat transfer oil (HTO). Erythritol (with a melting point of 391 K), which is a kind of sugar alcohol, was selected as a PCM. A vertical stainless steel cylinder with an inner diameter of 200 mm and height of 1 400 mm was used as the heat storage unit (HSU). A ringshaped injector with 18 holes positioned vertically downward was placed at the bottom of the HSU. Each hole in this injector had a diameter of 2.5 mm. We investigated the effects of the height of the PCM in the HSU, the HTO flow rate, and an increase in the number of injection-nozzle holes on the temperature effectiveness and heat exchange rate as indices of the heat release performances. As results, we found that an increase in the number of nozzle holes accelerated the uniform distribution of the HTO in the liquid PCM, prevented the HTO drift flow and adverse solidification of the PCM, and improved the heat release performance under the condition of a high HTO flow rate.

VO2-dispersed glass: A new class of phase change material

“…Hence, heat storage technology is indispensable for efficient energy utilization and sustainable development. This technology can appropriately balance the supply and demand amounts of thermal energy for different times and/or spaces, i.e., heat compensation by the shift in the time or space 1 . Thus, heat storage materials are crucial for realizing the time-/space shift in motor vehicles and solar-thermal electric generation.…”

High-Temperature Latent Heat Storage Technology to Utilize Exergy of Solar Heat and Industrial Exhaust Heat

“…The fluidized-bed type can transport dense thermal energy from one process to another. Combinations of the PCM with liquid [17] or gas [18,19] Prospects of latent heat storage method based on exergy recuperation T. Nomura and T. Akiyama [2,[20][21][22][23] where the heat exchange proceeds between the PCM and the HTF without any heat transfer wall. Here, the PCM is required to be insoluble in the heat transfer medium, and the density of the PCM is required to be high enough to ensure that a phase separation is possible.…”

High-temperature latent heat storage technology to utilize exergy of solar heat and industrial exhaust heat

“…Combinations of the PCM with liquid or gas as the HTF have been proposed. The other type is a direct‐contact heat exchanger where the heat exchange proceeds between the PCM and the HTF without any heat transfer wall. Here, the PCM is required to be insoluble in the heat transfer medium, and the density of the PCM is required to be high enough to ensure that a phase separation is possible.…”