A METHODE TO IMPROVE EVAPORATIVE COOLING SYSTEM IN GREENHOUSES UNDER HOT AND HUMID CLIMATIC CONDITIONS

Almuhanna, Emad A.

doi:10.21608/mjae.2010.105393

A METHODE TO IMPROVE EVAPORATIVE COOLING SYSTEM IN GREENHOUSES UNDER HOT AND HUMID CLIMATIC CONDITIONS

Document Type : Original Article

Author

Emad A. Almuhanna

Assistant Professor, Department of Agricultural Systems Engineering, King Faisal University, Hofuf, Saudi Arabia.

10.21608/mjae.2010.105393

Abstract

A combining cooling system is proposed and analyzed to achieve higher cooling efficiency in hot and humid climatic conditions such as in Saudi Arabia. The system was investigating and tested under the weather conditions of Al-Ahssa, Saudi Arabia. In this paper, the results of a study on combining cooling coil unit (CCU) and direct evaporative cooling (DEC) have been discussed.The cooling effectiveness of the cooling coil unit and direct evaporative cooling systems are experimentally investigating on small greenhouse model.Total solar radiation entering the greenhouse, temperature and relative humidity of outdoor air, dry and wet-bulb temperatures of air just leaving the cooling coil unit CCU), and dry and wet-bulb temperatures of air just leaving the direct evaporative cooling system (DEC) were measured and recorded on a data-logger to analyses their correlation with the effectiveness of each cooling system. The obtained data showed that, the hourly average solar radiation flux incident outside and transmitted into the greenhouse was 555.7 and 298.7 W/m², respectively, consequently, the effective transmittance of the covering material was on the average 53.75%. The temperature and relative humidity of outdoor air, respectively, were 37.3ºC and 21.8%, dry and wet-bulb temperatures just leaving the cooling coil were 29.4ºC and 18.8ºC, respectively, and dry-bulb temperatures of air just leaving the direct evaporative cooling were 22.8ºC. The obtained results also revealed that, the overall effectiveness of the combining cooling system was more than 100%. Thus, this system environmentally clean and energy efficient system, which considered as an alternative to the mechanical, vapour compression systems. This combining cooling system provided and maintained optimal microclimatic conditions that achieved vapour pressure deficit (VPD)

*Assistant Professor, Department of Agricultural Systems Engineering, King Faisal University, Hofuf, Saudi Arabia.

of 0.76 and 0.40 kPa inside the greenhouse model during daylight and at night, respectively. It can also conclude that, this combining cooling system can use in various climatic conditions as an environmentally clean and energy efficient system.

Keywords

Main Subjects

Agricultural Constructions Engineering

References

Abdel-Wahab, S. (1994) "Energy and water management in evaporative cooling system in Saudi Arabia: Resources, conservation and Recycling, 12(3-4):135-146.

Al-Helal, I. M. (2002) "Water consumption by fan-pad evaporative cooling system under arid climate conditions" Arab Universities Journal of Agricultural Science, 10(2): 429-440

Al-Helal, I. M.; Al-Abbadi, N. ; and Al-Ibrahim, A. (2004) "A study of fan-pad cooling performance for a photovoltaic powered greenhouse in Saudi Arabian summer" International Agricultural Engineering Journal, 13(4):113-124.

Arbel, A. ; Yekutieli, O. ; and Barak, M. (1999) "performance for cooling greenhouses" Journal of Agricultural Engineering Research, 72(2):129-136.

Argus Control Systems, LTD (2009) "Understanding and using VPD" Argus Application Note, Printed in Canada.

ASHRAE (2005) "Handbook of Fundamentals" American Society of Heating, Refrigerating and Air Conditioning Engineers, New York, USA.

Bailey, B. J. ; and Kano, A. (1995) "greenhouse climate control-new challenges" Acta Horticulturae, 399:13-23.

Camargo, J. R. ; Ebinuma, C. D. ; Silveria, J. L. (2005) "Experimental performance of a direct evaporative cooler operating during summer in a Brazilian city" International journal of Refrigeration, 28:1124-1132.

Cerci, Y. (2003) "A new ideal evaporative freezing cycle" International Journal of Heat and Mass Transfer, 46:2967–2974.

Costelloe, B. ; Finn, D. (2003) "Indirect evaporative cooling potential in air-water systems in temperate climates" Energy and Buildings, 35 (6):573-591.

Elad, Y. ; Malathrakis, N. E. ; and Dik, A. J. (1996) "Biological control of Botrytis-incited diseases and powdery mildews in greenhouse crops" Crop Protection, 15(3):229-238

Heidarinejad, G. ; Farahani, M. F. ; and Delfani, S. (2010) "Investigation of a hybrid system of nocturnal radiative cooling and direct evaporative cooling" Building and Environment, 45:1521-1528.

Jain, D. ; and Tiwari, G. N. (2002) "Modeling and optimal design of evaporative cooling system in controlled greenhouse" Energy Conversion and Management, 43:2235-2250.

Jamal, K. A. (1994) "Greenhouse cooling in hot countries" Energy, 19(11):1187-1192.

Jin Guang-Yu ; Cai Wen-Jian ; Wang Yao-Wen ; and Yao-Ye (2006) "A simple dynamic model of cooling coil unit" energy Conversion and Management, 47(15-16): 2659-2672.

Kittas, C. ; Bartzanas, T. ; Jaffarin, A. (2001) "Greenhouse evaporative cooling measurement and data analysis" Transactions of the ASAE, 44(3):683-689.

Kittas, C. ; Bartzanas, T. ; Jaffarin, A. (2003) "Temperature gradients in a partially shaded large greenhouse equipped with evaporative cooling pads" Bio-systems Engineering, 85(1):87-94.

Meir, M. G. ; Rekstad, J. B. ; and Lovvik, O. M. (2003) "A study of a polymer-based radiative cooling system" Solar energy, 73(6):403-417.

Nelson, P. V. (1996) "Greenhouse operation and management: Fifth edition, Prentice-hall, Inc., New Jersey, 07632

Prenger, J. J. ; and Ling, P. P. (2004) "Greenhouse condensation control" understanding and using vapour pressure deficit (VPD), Fact Sheet, Ohio State University Extension, Columbus, USA.

Sethi, V. and Sharma, S. K. (2007) "Survey of cooling technologies for worldwide agricultural greenhouse application" Journal of Solar Energy, 81:1447-1459

Toida, H. ; Kozai, T. ; and Ohyama, K. (2006) "Enhancing for evaporative rate using an upward air stream to improve greenhouse-cooling performance" Bio-systems Engineering, 93(2):205-211.

Wang, S. K. (2001) "Handbook of air conditioning and refrigeration" 2^nd edition, McGraw-hill, USA

Willits, D. H. (2003) "Cooling fan ventilated greenhouse; a modeling study" Bio-Systems Engineering, 84(3):315-329.

Wu, J. M. ; Huang, X. ; and Zhang, H. (2009) "Numerical investigation on the heat and mass transfer in a direct evaporative cooler" applied Thermal Engineering, 29:195-201.