Pretreating anaerobic fermentation liquid with calcium addition to improve short chain fatty acids extraction via in situ synthesis of layered double hydroxides

In situ synthesis of layered double hydroxides (LDHs) was proved to be an effective way to extract short chain fatty acids (SCFAs) from anaerobic fermentation liquid (AFL) as carbon source for biodenitrification, but the SCFAs content in SCFAs-LDH was unsatisfactory because of the existence of much carbonate in AFL. Pretreatment of AFL with calcium addition was investigated to remove carbonate and improve SCFAs extraction via LDHs synthesis. Results of batch tests showed that, the carbonate removal efficiency was as high as 76.6% when the calcium addition was 0.06 mol/L at pH 12. When using the optimal SCFAs/Al3+ ratio of 3.0, the total SCFAs content in SCFAs-LDH with pretreatment was improved to 46.5 mg COD/g LDH, which was 4.5 times of the control (10.4 mg COD/g LDH). These results suggest that adding calcium to AFL was an effective way to eliminate the negative effect of carbonates on SCFAs-LDH synthesis

Development of cryogenic loop heat pipes: A review and comparative analysis

Loop heat pipes (LHPs) are highly efficient two-phase heat transfer devices with the ability to transport a large amount of heat over a long distance. Due to increasing demand of efficient cryocooling applications in both space and terrestrial surroundings, LHPs operating in cryogenic temperature range have been extensively investigated in recent years. This work provided a comprehensive review of the state-of-the-art of cryogenic loop heat pipes (CLHPs). Five different types of CLHPs were categorized, and a comparative analysis between CLHPs and ambient LHPs and among different types of CLHPs was conducted. More attention was paid to the supercritical startup of CLHPs, and the operation and performance characteristics of different types of CLHPs were compared in terms of system structure, supercritical startup, heat transport capacity and the effect of parasitic heat load. The parameters that affect the CLHP performance were analyzed, and the optimization strategy was proposed in order to progress their future development and engineering applications

Pool boiling with high heat flux enabled by a porous artery structure

A porous artery structure utilizing the concept of “phase separation and modulation” is proposed to enhance the critical heat flux of pool boiling. A series of experiments were conducted on a range of test articles in which multiple rectangular arteries were machined directly into the top surface of a 10.0 mm diameter copper rod. The arteries were then covered by a 2.0 mm thickness microporous copper plate through silver brazing. The pool wall was fabricated from transparent Pyrex glass to allow a visualization study, and water was used as the working fluid. Experimental results confirmed that the porous artery structure provided individual flow paths for the liquid supply and vapor venting, and avoided the detrimental effects of the liquid/vapor counter flow. As a result, a maximum heat flux of 610 W/cm2 over a heating area of 0.78 cm2 was achieved with no indication of dryout, prior to reaching the heater design temperature limit. Following the experimental tests, the mechanisms responsible for the boiling critical heat flux and performance enhancement of the porous artery structure were analyzed