Fifteen years of research in innovative heating, ventilation and air conditioning plants at the Department of Management and Engineering (University of Padova) (original) (raw)
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Design of heat pump-driven liquid desiccant air conditioning systems for residential building
Applied Thermal Engineering, 2021
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International Journal of Refrigeration, 2006
The paper presents a new desiccant cooling cycle to be integrated in residential mechanical ventilation systems. The process shifts the air treatment completely to the return air side, so that the supply air can be cooled by a heat exchanger. Purely sensible cooling is an essential requirement for residential buildings with no maintenance guarantee for supply air humidifiers. As the cooling power is generated on the exhaust air side, the dehumidification process needs to be highly efficient to provide low supply air temperatures. Solid rotating desiccant wheels have been experimentally compared with liquid sorption systems using contact matrix absorbers and cross flow heat exchangers. The best dehumidification performance at no temperature increase was obtained in an evaporatively cooled heat exchanger with sprayed lithium chloride solution. Up to 7 g kg-1 dehumidification could be reached in an isothermal process, although the surface wetting of the first prototype was low. The process then provides inlet air conditions below 20°C for the summer design conditions of 32°C, 40% relative humidity. With air volume flow rates of 200 m³ h-1 the system can provide 886 W of cooling power. A theoretical model for both the contact absorber and the cross flow system has been developed and validated against experimental data for a wide range of operating conditions. A simulation study identified the optimisation potential of the system, if for example the surface wetting of the liquid desiccant can be improved.
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.
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, 2018
The main objective of this research is to investigate the energy performance enhancement obtained by applying a heat pump to a liquid desiccant and indirect and direct evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS). In conventional LD-IDECOAS operation, the boiler providing regeneration heat to the weak desiccant solution consumes most of the energy. In order to reduce the regeneration energy consumption in the LD-IDECOAS, a heat pump-integrated LD-IDECOAS (HPLD-IDECOAS) is suggested in this research. The heat pump reclaims waste heat from the absorber side of the system, and delivers the reclaimed heat to the regenerator side. Detailed energy simulations for both the LD-IDECOAS and HPLD-IDECOAS were conducted to analyze the energy saving potentiality of the proposed system over the conventional LD-IDECOAS. In both systems, it was assumed that a packed-bed type liquid desiccant unit with an aqueous solution of lithium chloride (LiCl) was used. In the proposed system, a heat pump with R-134a refrigerant was adopted. The results show that the proposed system was able to provide a 33% reduction in annual primary energy consumption compared with the conventional LD-IDECOAS. This significantly enhanced energy performance was mainly obtained through an 83% reduction in the gas energy consumed for regeneration of the desiccant solution in the proposed system by applying the heat pump.
Parametric study of an energy efficient air conditioning system using liquid desiccant
Applied Thermal Engineering, 1998
ÐLiquid desiccant can be used eectively to reduce energy consumed in air conditioning (AC). Unlike conventional AC, the latent part of the cooling load is overcome using liquid desiccant. In a previous article, an energy ecient system utilizing CaCl 2 as liquid desiccant was proposed. This study is an extension of that work. The eect of key variables on the performance of the proposed system is undertaken. The inlet temperature of the liquid desiccant to the dehumidi®er, space sensible heat ratio, and heat exchanger eectivenesses are the variables studied. Variations of these parameters and their eects on system performance are presented. Good system performance and energy saving could be achieved if proper values of these variables are selected.
Potential of a desiccant-evaporative cooling system performance in a multi-climate country
International Journal of Refrigeration, 2011
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Air conditioning systems with desiccant wheel for Italian climates
International Journal on …, 2000
Hybrid air conditioning systems based on chemical dehumidification are characterised by high energy efficiency and low environmental impact. They can result profitable if compared to traditional air conditioning systems and allow to obtain better indoor thermal comfort and air quality. In this paper, different hybrid air conditioning system configurations with desiccant wheel are examined; later, a first evaluation of operating costs is carried on, for Italian climates. For this purpose, a commercial computer program, DesiCalc TM , has been employed: from the European file known as TRY, hourly climatic data have been derived and adequately processed. For retail store application, for four Italian sites, maximum saving of about 22% has been obtained, while for theatre obtainable saving is greater and has been evaluated between 23% and 38%. For both the applications, the required comprehensive electric power is reduced (up to about 55%), and also the hours during which the system does not well control indoor relative humidity are strongly reduced.
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.