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A preliminary experimental investigation on characteristics of natural convection based on solar thermal collection using supercritical carbon dioxide
Author(s) -
Zhang X. R.
Publication year - 2013
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.2936
Subject(s) - supercritical fluid , thermal , supercritical carbon dioxide , mass flow rate , thermodynamics , materials science , mechanics , volumetric flow rate , supercritical flow , critical point (mathematics) , convection , natural convection , carbon dioxide , meteorology , nuclear engineering , chemistry , physics , engineering , mathematical analysis , mathematics , organic chemistry
SUMMARY In this paper, an experimental work is carried out to investigate the characteristics of solar thermal collection using supercritical CO 2 . This solar thermal conversion is based on supercritical CO 2 natural convection, which is much easily induced because a small change in temperature can result in large change in density close to the critical point. In addition, its critical temperature is 31.1°C and low enough to be easily reached in the low‐temperature solar thermal conversion system. The obtained results show that the supercritical CO 2 flow rate is smooth curve and not affected by the sudden variation of the solar radiation. The solar thermal conversion operation process can be divided into three periods: starting‐up, transition, and stable period. When the system reaches the stable period, the CO 2 flow rate will keep at a high value even if the solar radiation stays at a low level. It is also found that the smaller local solar radiation variation is, the better ability of keeping the flow rate near the peak level the supercritical CO 2 fluid owns. It is also found that a small pressure difference can drive a supercritical CO 2 flow with high flow rate. Furthermore, high solar thermal conversion efficiency is found at a high mass flow rate and under operation pressure near the critical point. Copyright © 2012 John Wiley & Sons, Ltd.