INTRODUCTION TO DESICCANT BASED AIR CONDITIONING (original) (raw)
ADVANCEMENT IN DESICCANT AIR-CONDITIONING TECHNOLOGY
IRJMETS Publication, 2021
Due to the current energy crisis and high energy costs, various air conditioning systems are being investigated. Desiccants are a type of adsorbent substance with a strong attraction to water vapour. Desiccant air conditioning technology delivers improved indoor air quality with comparatively less power consumption. A brief overview on the working principle along with different types of desiccant evaporative cooling systems has been provided. The advancement is demonstrated through a literature analysis. Different types of desiccant materials and obstacles for the acceptance in recent market is summarized in the review.
Review on Recent development in Desiccant Cooling
International Journal of Energy Resources Applications
Due to its sustainable cooling design and inexpensive operation, desiccant based dehumidification and cooling systems have been popular in recent years for humid areas. In general, the desiccant cooling used in conjunction with evaporative cooling as two separate types of configurations according to direct or indirect cooling. The relative humidity of moist outside air can potentially be controlled by both the systems during dehumidification and cooling to produce indoor thermal comfort. The solid desiccant-assisted evaporative cooling technologies may enable the use of the technique in a wider variety of climates, including those with high humidity. The development of innovative desiccant materials, improvement of the structure and material of the dehumidifier setup, desorption consumption rate and operating strategy of the system are some of the potential research possibilities and recommendations that were made. According to this review study, the desiccant integrated innovative ...
Application of Liquid Desiccant Cooling Technology in Built Environment: A Review
International Journal of Modern Studies in Mechanical Engineering, 2020
The role of the desiccant used in the dehumidifier is to remove water vapor from the conditioned air due to vapor pressure difference between the hot desiccant and the supply conditioned air. The desiccant can be categorized mainly into the two categories as solid adsorption and liquid absorbent desiccant materials. Several other types of solid materials are available in nature that can hold water vapor to the great extent to its weight, e.g., silica, polymers, zeolites, alumina and mixtures. Other commonly used liquid desiccant materials are calcium chloride, lithium chloride, lithium bromide, triethylene glycol and an equal mixture between calcium chloride and lithium chloride. These liquid desiccants have many thermo-physical properties, but their requirements cannot be fully described by any single desiccant. These requirements include low vapor pressure, low crystallization point, high density, low viscosity, low reactivation temperature, and economy [1]. The moist air is dehumidified by being brought into contact with strong liquid or solid desiccant, after this to provide sensible cooling to dehumidification process, traditional vapor compression, and vapor absorption, direct or indirect evaporative cooler units used. When the solution is weakened by absorption of moisture, it provided for the regeneration process that can loses its moisture content due to external thermal source. This called as reactivating the saturated desiccant material [2]. Thermal energy, at a temperature as low as 46-72°C required for reactivating of the liquid desiccant can efficiently obtained using a particular type of air or water solar collector or other primary heat renewable source [3]. The typical cycle of the desiccant is made up by three processes as shown in Figure 1and Figure 2 depicts the fundamental deviation among traditionally used air conditioner and novel desiccant assisted dehumidification and cooling process [4]. The traditionally used vapor-compression cycle is now the foundation of the world air conditioning industry and will remain so for many years in conjunction with other hybrid cooling systems. The following problems are being addressed through a number of approaches including: (1) More efficient designs for household and commercial air conditioners, (2) More efficient buildings that require minimum or zero cooling, (3) The conversion Abstract: Liquid-desiccant assisted dehumidification and cooling system has been proved to be an effective method to extract the moisture of air with relatively less energy consumption, especially compared with conventional vapor compression system. To date, the conventional dehumidification mode with desiccant solution has been improved or replaced by newly emerged energy-saving systems with better performance. This paper gives a detailed account of the general features of the various components used in desiccant dehumidification and cooling techniques; meanwhile, the effect of various operating parameters on system performance also highlighted. Moreover, a summary of the experimental and analytical studies to evaluate the system performance has been made. Some new hybrid systems that greatly expand the desiccant dehumidification technique in industrial and residential applications, as well as effectively promoting the single system's performance, are also reviewed through literature. Through a literature review, the feasibility of the desiccant cooling is proven by its comparison with conventional vapor compression system in terms of energy and cost savings are underscored. Finally, future study and application for liquiddesiccant dehumidification techniques are concluded.
An overview of solid desiccant dehumidification and air conditioning systems
Renewable and Sustainable Energy Reviews, 2015
To address the importance of desiccant airconditioning (DAC) systems, this paper discusses the comparison between DAC and conventional vapor compression airconditioning (VAC). Performance and economic feasibility (PEF) of the system is conferred with reference literature to correlate the types of DAC system from the perspective of energy saving and system payback period. The present study provides three examples of existing desiccant cooling systems namely (i) standalone DAC system, (ii) single-stage hybrid DAC system, and (iii) two-stage hybrid DAC system, which highlight their importance under different environmental conditions. This study provides scientific and experimental supports on how the standalone or hybrid desiccant cooling can be a supplement to the exiting VAC system.
A Study of Desiccant-Based Cooling and Dehumidifying System in Hot-Humid Climate
International Journal of Materials, Mechanics and Manufacturing, 2013
The objective of this study is to investigate the feasibility of using desiccant cooling system as an alternative HVAC solution in buildings to achieve thermal comfort. This solution is more attractive when the solar energy is used to regenerate the desiccant wheel. An extensive experimental study has been performed in Tohoku University in Japan. A TRNSYS model of the desiccant cooling system combined with the heat wheel and heat source has been simulated and compared with the experimental data. The results of the simulation show that such system is feasible for cooling building in hot-humid climates.
A review on desiccant based evaporative cooling systems
The air conditioner should control the building sensible and latent load properly in order to provide the indoor comfort conditions. The conventional mechanical vapor compression system usually controls the latent load by the process of condensation of water vapor in which air is cooled below its dew point temperature and then reheated again up to the required supply conditions. The conditions where latent load is dominant these two processes i.e. overcooling and then reheating again will increase the consumption of electrical energy and emission of CO 2 remarkably. To avoid this wastage of primary energy and emission of harmful gases, desiccant based evaporative cooling system is a good alternative to traditional air conditioning system which is cost effective as well as environment friendly. It can be driven by thermal energy which makes a good use of solar energy which is free as well as clean. In this paper, a review of desiccant based evaporative cooling systems has been presented. The present study is undertaken from variety of aspects including background and need of alternative cooling systems, concept of conventional and desiccant based evaporative coolers, system configurations, operational modes, as well as current status of the desiccant based evaporative cooling technology. The review work indicated that the technology of desiccant based evaporative cooler has a great potential of providing human thermal comfort conditions in hot and humid climatic conditions at the expense of less primary resources of energy as compared to conventional cooling systems. Some modified and modern evaporative coolers have also been introduced in this paper.
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...
Nowadays, the increasing demand of summer cooling is typically covered by electric chillers, often determining electric peak loads and blackouts. Thus, a wide interest is spreading in small scale natural gas-fired cogenerators driving desiccant-based airconditioning systems, which represent interesting alternatives to conventional systems based on vapor compression cooling only. In this article, experimental tests performed on an air handling unit (AHU) equipped with a desiccant wheel (DW), coupled to a small scale cogenerator and an electric chiller are described. A new layout of the desiccantbased AHU is investigated, considering a third flow (the cooling air), besides the process air flow and the regeneration one. A cross-flow heat exchanger between process air and cooling air is used; the cooling air, cooled by an adiabatic humidifier, is aimed to precool the process air exiting the DW. The relevant influence of the heat exchanger and of the humidifier, as well as that of the chiller performance, on global primary energy requirements, water consumption and CO 2 equivalent emissions of the system is experimentally evaluated.
Desiccant cooling with solar energy
2001
Desiccant cooling systems combine sorptive dehumidification, heat recovery, evaporation and heating to create a cooling process which can offer energy savings compared to conventional air conditioning systems. Waste heat or solar energy can be used for the required regeneration of the sorbens in the dehumidifier, leading to further energy savings. A desiccant cooling plant with solar air collectors has been installed and parametric studies, particularly of the dehumidifier, have been undertaken. These show that it is possible to reduce the regeneration air flow with only a small reduction in the dehumidification efficiency, enabling desiccant cooling systems to run with high COPs. The results of the measurements were used as input parameters to a new dynamic simulation program, which was specifically developed for the purpose of assessing the potential for desiccant cooling under different climatic conditions. The program predicts the hourly performance of a desiccant cooling system and the associated building. With this new simulation tool it is possible to optimise desiccant cooling systems with solar components. The simulations were executed for a desiccant cooling system with solar air collectors connected to a test building and using climatic data of Stuttgart,
ENHANCEMENT OF THE PROCESSES OF DESICCANT AIR CONDITIONING SYSTEM
An experimental study was carried out to evaluate the liquid desiccant system performance during dehumidification and humidification processes using air injection through the liquid desiccant solution (Calcium Chloride). The air flows cross the desiccant solution with different air mass flow rates. The system is studied at different operating condition (air flow rate, temperature, humidity ratio and solution levels). The effectiveness of the proposed system for both dehumidification and humidification processes were evaluated. Also, the cooling effect and mass transfer coefficient was obtained. It is found that the system effectiveness reached 0.75 in the dehumidification process and 0.7 in the humidification process. Mass transfer coefficient depends on the air mass flow rate and the desiccant solution level in the tank Economical Results of the presented system is estimated