TY - JOUR
T1 - A multi-stage down-draft evaporative cool tower for semi-enclosed spaces
T2 - Experiments with a water spraying system
AU - Pearlmutter, David
AU - Erell, Evyatar
AU - Etzion, Yair
N1 - Funding Information:
This research was supported by a Grant from the Israel Ministry of Science, Culture and Sport and Forschungszentrum Juelich GmbH, Germany, within the Joint German–Israeli Research Program. Installation of the equipment and supervision of the monitoring program were carried out by Mr. Wolfgang Motzafi-Haller. Eng. S. Guetta assembled data concerning the operating characteristics of sprayers nozzles.
PY - 2008/5/1
Y1 - 2008/5/1
N2 - A novel down-draft evaporative cool tower (DECT) was developed which incorporates a secondary air inlet and a complex longitudinal section that comprises two partly overlapping cones. The objective of this design is to conserve water while providing equal or superior cooling to conventional DECTs, in which dry ambient air is drawn in through a single inlet at the top and cooler moist air is delivered at the bottom. The complex section and the addition of a secondary air intake near the middle required a sophisticated water spraying system. In addition to maximizing the cooling potential, the spraying system was designed to limit spray drift beyond the base of the tower, to reduce maintenance costs (especially due to clogging of the sprayers) and to minimize pumping energy. Analysis shows that maximum cooling may be obtained either by employing a very fine spray, requiring the introduction of a relatively small volume of water, or by spraying a larger volume of coarser drops. However, spraying fine drops requires more pumping power, finer nozzles are more likely to clog and small drops of water aggravate the problem of drift near the tower base. If full evaporation of the water spray is not required and excess water is collected for reuse, the second option is thus preferable. In addition to the theoretical analysis, the paper presents experimental findings on temperature reduction, water consumption and cooling output of an 8-m high prototype tower constructed at Sede-Boqer, Israel.
AB - A novel down-draft evaporative cool tower (DECT) was developed which incorporates a secondary air inlet and a complex longitudinal section that comprises two partly overlapping cones. The objective of this design is to conserve water while providing equal or superior cooling to conventional DECTs, in which dry ambient air is drawn in through a single inlet at the top and cooler moist air is delivered at the bottom. The complex section and the addition of a secondary air intake near the middle required a sophisticated water spraying system. In addition to maximizing the cooling potential, the spraying system was designed to limit spray drift beyond the base of the tower, to reduce maintenance costs (especially due to clogging of the sprayers) and to minimize pumping energy. Analysis shows that maximum cooling may be obtained either by employing a very fine spray, requiring the introduction of a relatively small volume of water, or by spraying a larger volume of coarser drops. However, spraying fine drops requires more pumping power, finer nozzles are more likely to clog and small drops of water aggravate the problem of drift near the tower base. If full evaporation of the water spray is not required and excess water is collected for reuse, the second option is thus preferable. In addition to the theoretical analysis, the paper presents experimental findings on temperature reduction, water consumption and cooling output of an 8-m high prototype tower constructed at Sede-Boqer, Israel.
KW - DECT
KW - Evaporation
KW - Passive cooling
KW - Semi-enclosed spaces
UR - http://www.scopus.com/inward/record.url?scp=41949086355&partnerID=8YFLogxK
U2 - 10.1016/j.solener.2007.12.003
DO - 10.1016/j.solener.2007.12.003
M3 - Article
AN - SCOPUS:41949086355
SN - 0038-092X
VL - 82
SP - 430
EP - 440
JO - Solar Energy
JF - Solar Energy
IS - 5
ER -
