Abstract
Activated carbons are widely used for sustainable technology of adsorptive transformation and storage of heat. Here, we analyze the applicability of twelve commercial carbons and an innovative carbonaceous composite “LiCl confined to multi-wall carbon nanotubes” (LiCl/MWCNT) for a new cycle “Heat from Cold” (HeCol). It has recently been proposed for amplification of low- temperature ambient heat in cold countries. The analysis is made in terms of the methanol mass exchanged and the useful heat generated per cycle; the latter is the main performance indicator of HeCol cycles. The maximum specific useful heat, reaching 990 and 1750 J/g, can be obtained by using carbon Maxsorb III and the composite, respectively. For these materials, methanol adsorption dynamics under typical HeCol conditions are experimentally studied by the large pressure jump method. Before making this analysis, the fine carbon powder is consolidated by either using a binder or just pressing to obtain larger particles (ca. 2 mm). The methanol desorption from the consolidated samples of Maxsorb III at T = 2 °C is faster than for LiCl/MWCNT, and the maximum (initial) useful power reaches (2.5–4.0) kW/kg sorbent. It is very promising for designing compact HeCol units utilizing the carbon Maxsorb III.
Highlights
Porous carbonaceous materials have been known about since earliest times, e.g., the Egyptians and Sumerians used wood chars in medicine [1], water purification and the manufacture of bronze [2].Nowadays, an enormous variety of activated carbons (ACs) are available in grains, extrudates, monolith, fibers, cloths, etc. [2,3,4]
Porous carbonaceous materials have been well known since ancient times, when wood chars were used in medicine, water purification and the manufacture of bronze
This work addresses the applicability of commercial ACs and an innovative carbonaceous composite “LiCl in multi-wall carbon nanotubes” (LiCl/MWCNT) in a new cycle “Heat from Cold” (HeCol)
Summary
Porous carbonaceous materials have been known about since earliest times, e.g., the Egyptians and Sumerians used wood chars in medicine [1], water purification and the manufacture of bronze [2]. For the first theoretical [10,11] and experimental [12,13,14,15] studies of the HeCol cycle, methanol was Foranthe first theoretical and freezing experimental [12,13,14,15] studies It always liquid was used as an adsorptive because of its low freezing temperature HeCol cycle is feasible, and the temperature level of the useful heat can be sufficient for floor heating in low-energy buildings. Q us reachable by using the working pair does not exceed 235 J/g-carbon (for the cycle with boundary temperatures TL /TM /TH = −20/20/35 ◦ C) This be mostly to the relatively smallwith specific mass oftemperatures methanol exchanged cycle Their textural characteristics were studied by a low-temperature nitrogen adsorption
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