CO2 Heat Pumps (Cooling heat transfer of supercritical carbon dioxide)
Since the conventional refrigerants have
considerable Ozone depleting effect and global warming impact, Carbon
Dioxide (CO2) is being expected to be an alternative refrigerant for vapor
compression system. In addition to its environmental benefits, CO2 offers
certain attractive thermal characteristics such as small viscosity and
large refrigerant capacity. But because the heat rejecting process in gas
cooler (a substitute of condenser, since there is no phase change occurs)
is operated under supercritical pressure condition, the rapid variation of
thermodynamic properties with temperature and pressure makes the flow and
heat transfer differ from that at constant property greatly. An extensive
investigation about the understanding of cooling heat transfer and a
proper prediction method is critical for the design of CO2 heat pump. In
addition, the lubricant oil is always present in vapor compression
refrigeration system, thus the knowledge about flow and heat transfer of
refrigerant-oil mixture is of the same importance as that of pure
refrigerant.
In this research, the heat transfer of supercritical CO2
cooled in a circular tube was investigated theoretically and
experimentally. Some general features of flow and heat transfer with
drastic property variation were clarified. And influence of lubricant oil
on flow and heat transfer was investigated.
See also:
heat transfer characteristics of supercritical fluid
Flow boiling heat transfer of carbon dioxide
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| Experimental apparatus (left) and heat transfer coefficient (right) |
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| Experimental apparatus (left) and pressure drop (right) |
References
Dang C., Iino K., Hihara E., "Effect of PAG-type lubricating oil on heat transfer characteristics of supercritical carbon dioxide cooled inside a small internally grooved tube," Int. J. Refrigeration (2010)
[doi:10.1016/j.ijrefrig.2009.12.010] |
Dang, C.; Iino, K.; Hihara, E. "Study on two-phase flow pattern of supercritical carbon dioxide with entrained PAG-type lubricating oil in a gas cooler," Int. J. Refrigeration 31, 1265-1272 (2008)
[doi:10.1016/j.ijrefrig.2008.01.014] |
Dang, C.; Iino, K., Fukuoka; K.; Hihara, E. "Effect of lubricating oil on cooling heat transfer of supercritical carbon dioxide," Int. J. Refrigeration 30, 724-731 (2007)
[doi:10.1016/j.ijrefrig.2006.09.006] |
Dang, C.; Hihara, E. "In-tube cooling heat transfer of supercritical carbon dioxide, part 1: experimental measurement," Int. J. Refrigeration 27, 736-747 (2004)
[doi:10.1016/j.ijrefrig.2004.04.018] |
Dang, C.; Hihara, E. "In-tube cooling heat transfer of supercritical carbon dioxide, part 2: comparison of turbulence models in numerical calculation," Int. J. Refrigeration 27, 748-760 (2004)
[doi:10.1016/j.ijrefrig.2004.04.017] |
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