Effective desiccant dehumidification system with two-stage evaporative cooling for hot and humid climates (original) (raw)
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Journal of Building Engineering, 2021
Hot and humid climates present a challenge for implementing passive cooling practices in office spaces, due to the inherent small temperature difference between day and night, which affects the utilization of thermal storage systems. Moreover, added means are required to maintain the humidity in the space at an acceptable level for comfort. The novelty of this study is to design and implement a feasible hybrid cooling system for office spaces in such climates by uniquely combining several sustainable cooling, thermal storage, and dehumidification solutions. The proposed system integrates a phase change material (PCM) thermal storage layer with a melting temperature of 25 � C to cool the supply air and a personalized evaporative cooler (PEC) to provide cooling for the occupants. The supply air humidity is controlled using a solid desiccant wheel regenerated via an auxiliary heater assisted with a Trombe wall. Mathematical models were adopted for each system component/process, solved numerically and integrated to size the system components, simulate their operation and predict the overall system's performance in an office space during the summer months of Beirut climate. The proposed system was found to achieve acceptable thermal comfort levels in the space. Moreover, it reduced the total energy cost by 87% compared with a conventional air conditioning unit over the summer period. In addition, the Trombe wall provided energy savings of 55% compared to relying only on the auxiliary heater. Hence, integrating several sustainable solutions succeeded in implementing an effective cooling system of office spaces in hot humid climates.
International Journal of Green Energy, 2008
In this work, the transient performance of a hybrid desiccant vapor compression air conditioning system is numerically simulated for the ambient conditions of Beirut. The main feature of this hybrid system is that the regenerative heat needed by the desiccant wheel is partly supplied by the condenser dissipated heat while the rest is supplied by an auxiliary gas heater. The hybrid air conditioning system of the present study replaces a 23 kW vapor compression unit for a typical office in Beirut characterized by a high latent load. The vapor compression subsystem size in the hybrid air conditioning system is reduced to 15 kW at the peak load when the regeneration temperature was fixed at 75 °C. Also the sensible heat ratio of the combined hybrid system increased from 0.47 to 0.73.
Desiccant-evaporative cooling system for residential buildings
This paper describes a prototype desiccant evaporative cooling system (DEC) and presents its performance in term of indoor humidity control and energy efficiency. Experimental and simulation results show that the desiccant evaporative cooling system can achieve better humidity control and acceptable comfort conditions. The simulation results show that the desiccant cooling system is especially well suited for areas of the country with a high latent load. However the study identified a series of improvement measures to undertake in order to improve the energy efficiency of the unit. Cet article décrit un prototype de système de refroidissement à évaporation par déshydratant (DEC) et décrit sa performance en termes de contrôle de l'humidité intérieure et d'efficacité energétique. Les résultats expérimentaux et ceux de la simulation montrent que le système de refroidissement à évaporation par déshydratant peut permettre un meilleur contrôle de l'humidité et fournir des cond...
Energies, 2019
The technical and economic attractiveness of a solid desiccant based evaporative cooling system depend on several factors: Configuration of the system components and their individual performance, availability of cheap but reliable regeneration heat source. In the tropical and subtropical regions, the air conditioning systems are expected to address not only the sensible loads but also, and most importantly—the loads due to higher outside humidity levels that can severely affect the thermal comfort of the building occupants. This paper reports on the dehumidification potentials of solid desiccant based evaporative cooling systems with an enthalpy exchanger operating in subtropical and tropical climates. In particular, the study presents the cooling and dehumidification capabilities of the enthalpy exchanger observed through the impact of its sensible and latent effectiveness on the thermal comfort of the conditioned space. The key performance indicators are split into two groups: (1)...
Investigating performance of solid desiccant dehumidification in an evaporative cooling system
2018
Desiccant evaporative cooling (DEC) systems are still at early stage of utilisation and commercialise development. The primary focus of this study is to analyse the simulated performance of DEC in hot and humid climates. Four configurations of one-stage solid desiccant dehumidifiers with two-stage evaporative cooling systems have been simulated using TRNSYS simulation software for a typical test room. The psychrometric process and the coefficient of performance (COP) for each configuration is presented and configurations for the most efficient system have been identified.
Simulation of a desiccant-evaporative cooling system for residential buildings
One technology that can help reduce the electricity consumption of conventional air-conditioning technology is the coupling of active dehumidification with evaporative cooling. In this case sensible cooling and moisture removal from indoor and outside ventilation air are decoupled. In this study simulation models are developed for a conventional vapor compression based cooling system and a desiccant evaporative cooling system installed in an R-2000 house. Electricity consumption and comfort indices are then predicted for the two systems for three regions of the country with varying sensible heat ratios. It is found that, compared to a conventional system, the desiccant evaporative cooling system can lead to significant electricity consumption reductions and also reduce the number of hours when conditions inside the space are uncomfortable.
Performance Analysis of a Desiccant Evaporative Cooling System Under Hot and Humid Conditions
The control of air conditioning latent and sensible load separately by using a desiccant dehumidifier operating in conjunction with evaporative cooler can reduce the air conditioning power requirement significantly. This system can also utilize the alternative resources of energy such as solar, waste heat, and natural gas effectively. In this article a mathematical model of desiccant evaporative cooling has been developed and the performance of the system is analyzed for its feasibility under the climatic conditions of Dhahran, Saudi Arabia. Different performance curves have been drawn to get optimum values of parameters under different operating conditions. Some new parameters such as sensible energy ratio have also been introduced for better prediction of system cooling capacity. The results showed that the proposed system is suitable and feasible solution to meet the high cooling demands for the conditions of Dhahran, Saudi Arabia with performance largely dependent on optimum selection of operating parameters.
Energy Procedia, 2011
The objective of this research is evaluating and comparing two methods of improving dehumidification in air conditioning systems. The two methods are the hybrid system: (refrigeration cyclerotary desiccant) and the heat exchanger cycle. The impact of the desiccant performance on the hybrid system performance was studied. The impact of the heat exchanger efficiency on the performance of heat exchanger cycle was studied. Hybrid system, heat exchanger cycle, and conventional refrigeration cycle were compared at different design air flow rates and different air conditions. It was found that the hybrid system and the heat exchanger cycle can achieve lower SHR and dew point temperature than those of the conventional cooling system. On general, the hybrid system can achieve lower SHR and dew point than those of the heat exchanger cycle. Although the heat exchanger cycle can achieve lower SHR and dew point than those of the conventional cooling system, the coefficient of performance and the cooling effect of the heat exchanger cycle are lower than those of the conventional cooling system, because the temperature of the cooling coil of the heat exchanger cycle is lower than that of the conventional cooling system. The coefficient of performance and the cooling effect of the hybrid system are close to those of the conventional cooling system, because the temperature of the cooling coil of the hybrid system is close to that of the conventional cooling system.