Feasibility study of using agriculture waste as desiccant for air conditioning system

Renewable Energy (Impact Factor: 3.36). 08/2003; 28(10):1617-1628. DOI: 10.1016/S0960-1481(03)00003-X

ABSTRACT This research was aimed at investigating the feasibility of using dried agricultural waste as desiccant for an open cycle air conditioning system. The natural fibers are, therefore, intended to replace chemical desiccant such as silica gel, molecular sieves etc. The investigation was limited to Coconut coir (Cocos nucifera) and Durian peels (Durio zibethinus).Experimental results confirmed that dry coconut coir and durian peel can absorb 30 g and 17 g H2O per 100 g dry product, respectively, from air at the average condition of 32°C and 75% relative humidity. The optimum airflow rate is about 84 and 98 m3/hr-100 g dry product, respectively. Therefore, the dry coconut coir is more suitable than the dry durian peel.Comparison between the dry coconut coir and silica gel showed that the average adsorption rate of coconut coir is less than that of silica gel by about 5 g/h-100 g dry product at an airflow rate of 84 m3/h and 60 min operating time. However, it is still an interesting option to replace silica gel in open cycle air conditioning system, as the decrease of average adsorption rate is rather small.The other extremely interesting advantage of coconut coir is that during moisture absorption the heat generated during the process is less important. That means the air leaves the coconut coir bed at a lower temperature compared to that with a silica gel. Therefore, the saving of cooling energy is much more important.

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    ABSTRACT: This paper reports a performance analysis for a new sustainable engineering application to beneficially reuse an abundant agricultural waste, coconut coir (Cocos nucifera), in evaporative cooling pads. Two small coconut coir pads of different configurations were fabricated and tested using a laboratory‐scale experimental arrangement. The air supply velocity was controlled and varied between 1.88 and 2.79 m s−1. Heat and mass transfer coefficients, evaporative cooling efficiency and pressure drop across the two types of coconut coir pad were analysed and compared with those of a commercial rigid media paper pad. Results show that the cooling efficiency of the manufactured coconut coir evaporative cooling pad was fairly good (about 50%) and close to that of the commercial paper pad (about 47%). The average pressure drop across the two coconut coir pads was 1.5 and 5.1 Pa respectively. Correlations for heat and mass transfer coefficients expressed using Nusselt and Sherwood numbers are also reported. In addition, the cooling potential of the coconut coir pads was analysed using the average climatic conditions of the central region in Thailand throughout the year. The analysis showed that the air temperature leaving the coconut coir pad varied from 23 to 28°C. Commercial development appears feasible given the coconut coir pad's good performance, lower cost and its availability throughout the country.
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    ABSTRACT: In the present work, experimental performance data of a solid desiccant based hybrid air conditioning system are presented. The system consists of a packed bed solid desiccant integrated with a R407C conventional vapor compression refrigeration system. Experiments are carried out during dehumidification operation mode for various operating parameters such as; desiccant mass on shelves (5, 10 and 15 kg), air mass flow rate (7.4 and 10.2 kg/min), shelves number (1, 2 and 3) and three values of shelves span (7, 14 and 28 cm) at evaporator air inlet conditions of 28 °C DBT and 66% RH, condenser air inlet volume flow rate of 850 m3/h and temperature of 35 °C. The reactivation of the desiccant at different regeneration temperatures and air flow rates as well as desiccant masses is also investigated. During the dehumidification mode, the average system coefficient of performance increases by 6.2% and 1.61% when the mass of desiccant increases from 5 to 10 kg and from 10 to 15 kg, respectively. The enhancement in the coefficient of performance is 6.2% due to increasing the air mass flow rate from 7.4 to 10.2 kg/min. Increasing both shelves number and span yields to a reduction in the adsorption rate that can be extracted by the desiccant material in the ranges of considered operating conditions. The regeneration temperature and the air flow rate of regeneration have significant effects on the reactivation process. It was found that, with increasing the mass flow rate of regenerated air from 7.4 to 10.2 kg/min produces a reduction in regeneration time by 87.5% and an augmentation in the desorption rate by 16% after 10 min of regeneration. In addition, with escalating the regeneration temperature from 45 to 55 °C, the reactivation time reduces by 25%. Reported results revealed that solid desiccant based hybrid air conditioning system reduces the compressor electric power and the number of electric unit (kW h) by 10.2%.
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    ABSTRACT: Substantial effort has recently been devoted to passive solar desiccant air dehumidification. This research aims to describe the passive room dehumidifying system with the combination of an existing wooden attic space as a chamber and desiccant; an optimization of ventilation system and solar energy as system operation. The field measurement was carried out in the test house in Japan over hot humid summers in 2003 and 2004. It was found that the dehumidification rate of the wooden attic space was approximately 25 g/h per square meter of floor area of attic space. The electric coefficient of performance was ap- proximately 15. In addition to the attic space, regarding to the investigation on the system in- cluding the ventilation between the attic space and the bedroom, in the presence of an occupant, the humidity of the bedroom during the night- time was lower compared to the traditional natural ventilation approach throughout the night. Therefore, the system outlined in this study could be promising as a new passive tool for moisture control in hot humid region.