In the GRA method, the grey relational grade (GRG) can be used to evaluate the overall performance of each experiment based on the weights assigned to each attribute considered. One of the most well-known methods for generating objective weights is the entropy method (Heiner 2004). If an attribute has similar responses across all experiments, it means that this attribute does not help to differentiate different experimental conditions. The entropy method therefore assigns a small weight to this attribute according to the information theory (Zeng et al. 2015). Since the entropy method can express the relative intensities of important attributes to indicate average intrinsic information (Heiner 2004), the entropy method can objectively determine the weights of the quality characteristics for performance optimisation to calculate the GRG in GRA. The mean of S/N ratios for the GRG is then used to determine the optimal combination of operating parameters of ED for regenerating liquid desiccants. Finally, a confirmation test is carried out under the optimal operating conditions already identified.
At the start of the experiment, a valve from the propane cylinder is opened, and then the micro-tubular SOFC, the WHR pump, and the environmental chamber are switched on. WRR pump and chamber temperature/humidity is then set. Valves to the dehumidifier are switched off and a by-pass loop is opened to allow the system to gain working temperature rapidly. For the first 30 minutes or so, the micro-SOFC does not produce electrical power because it needs to reach a temperature of 200-300°C to enable it to reform fuel into hydrogen. The system is allowed to operate in by-pass mode until the water outlet temperature reaches approximately 50°C. In advance of the system reaching 50°C, the fans and pumps in the dehumidifier rig are started and flows are set. Once the system temperature reaches 50°C, the by-pass valves are shut and the valves to the regenerator are opened. Temperatures and humidity are recorded by a datalogger and voltage, current and volume flows and recorded until the completion of testing.
5. CSE Energy - A technical report of energy and buildings by Centre for Science and Environment. (2014). Available at <http:// www.cseindia.org/userfiles/Energy- and -% 20 buildings. pdf > [Accessed 5 th June 2017].
6. Ge, G., Ghadiri Moghaddam, D., Abdel-Salam, A.H., Besant, R.W. & Simonson, C.J. (2014). Comparison of experimental data and a model for heat and mass transfer performance of a liquid-to-air membrane energy exchanger (LAMEE) when used for air dehumidification and salt solution regeneration. Int J Heat Mass Transf,
Liquiddesiccant air-conditioning systems (LDAC) have emerged as a potential alternative to conventional vapour compression systems for air-conditioning. Desiccants are materials that have high affinity for absorbing water vapour. This technology, which can efficiently serve large latent loads, can greatly improve indoor air quality by allowing for easier humidity control while reducing the electrical energy consumption of traditional vapour compression systems. Air dehumidification is an important process not only in industrial applications, but also in space cooling for occupant health and comfort. In the case of desiccant based dehumidification systems, much of the thermal energy required to operate the systems can be drawn from sustainable sources such as solar thermal collectors. The present work studies one such desiccantsystem. The dehumidifier component (also referred to as the conditioner) of this system is the principle topic under investigation as it is directly responsible for the dehumidification of the air and the other components of the system exist to support its operation. Its performance greatly influences the overall performance of the complete system.
energy. El-Dessouky, et al. 9 proposed a novel air conditioning system integrating a membrane dehumidification unit with an indirect/direct evaporative cooler, and found that 86.2% energy saving can be achieved compared with a stand-alone vapour compression system. Jradi and Riffat 10 developed a hybrid dehumidification cooling system, with which the supply air temperature and humidity reduce from 33.8 ℃ to 22.3 ℃ and 68.6% to 35.5% respectively. Regarding to the membrane-based liquiddesiccantdehumidification cooling system, few researches have been carried out for feasibility study and performance evaluation through experimental work. In this study, a membrane-based hybrid dehumidification cooling system is built for experimentalinvestigation. The system feasibility and performance are evaluated under various operation conditions; the influences of inlet air condition, desiccant concentration and regeneration temperature on the system performance are investigated based on the experimental results.
Consequently, the purpose of this study is to investigate empirically the performance of an ICLD using evaporative cooling for use of internal cooling sources. The ICLD used in this study was designed for a cross-flow type between the process and working air streams. The impact of the variation in working air stream on the dehumidification cooling performance of an ICLD is a key factor of this study. Therefore, the dehumidification cooling performance of an ICLD was examined under various working airflows in an environmental climate chamber. The airflow ratio (AFR) between the working and process air was adjusted from 0.25 to 1.0 while increasing the AFR 0.25 for each experimental step. The measured data were estimated using system performance indicators such as the cooling capacity, wet-bulb effectiveness, volume mass transfer coefficient, and coefficient of performance (COP) of the ICLD.
The selection of an evaporative cooling unit for an LDDC system depends on climate condition, supply air demand, cost and etc. The feasibility of an LDDC system with an indirect evaporative cooling unit is evaluated by experimental work in , in which the indoor air temperature reduces from 33.8°C to 22.3°C and the relative humidity decreases from 68.6% to 35.5%. With the similar design concept, a drop of 7.5°C in the indoor air temperature is achieved in . In response to the climate condition and air conditioning requirement in Hong Kong, a hybrid liquiddesiccant air conditioning system is developed by integrating both direct and indirect evaporative cooling means , whose performance is investigated by theoretical modelling. The LDDC system with an evaporative cooling unit is proved with remarkable energy and cost saving potentials . By installing an evaporative-cooling assisted LDDC system for an open office building in Seoul, South Korea, 12% saving of the annual primary energy consumption could be achieved compared with the conventional air conditioning system . More than 50% of the lifetime operating cost can be saved with an LDDC system compared to the conventional air conditioning system in Singapore . By utilizing renewable energy in the regeneration process, the LDDC system can be more sustainable and economical, for example the abundant solar energy. Not only solar thermal but also photovoltaic technologies can be integrated into a solar-assisted LDDC system . The feasibility of a membrane-based liquiddesiccantdehumidification cooling (MLDDC) system powered by solar thermal energy is proved in with significant economic and environmental benefits.
Abstract: In this study, energy and exergy analysis of experimental results obtained from a dehumidificationsystem using LiBr-aq (lithium bromide-water) and LiCl-aq (lithium chloride- water) as desiccant was made. In dehumidifier and regenerator columns polycarbonate sheets, which have not been used before, were used as packing material to increase contact area in purposed liquiddesiccantdehumidificationsystem. In the analysis, variation of electrical coefficient of performance and exergy efficiency with airflow rate for different solution mass flow rates were investigated. Because of investigation, maximum values of electrical coefficient of performance and exergy efficiency were calculated approximately as 2.8 and 18%, respectively. Keywords: energy; exergy; liquiddesiccant; liquiddesiccantdehumidification; polycarbonate packing
energy. El-Dessouky, et al. 9 proposed a novel air conditioning system integrating a membrane dehumidification unit with an indirect/direct evaporative cooler, and found that 86.2% energy saving can be achieved compared with a stand-alone vapour compression system. Jradi and Riffat 10 developed a hybrid dehumidification cooling system, with which the supply air temperature and humidity reduce from 33.8℃ to 22.3℃ and 68.6% to 35.5% respectively. Regarding to the membrane-based liquiddesiccantdehumidification cooling system, few researches have been carried out for feasibility study and performance evaluation through experimental work. In this study, a membrane-based hybrid dehumidification cooling system is built for experimentalinvestigation. The system feasibility and performance are evaluated under various operation conditions; the influences of inlet air condition, desiccant concentration and regeneration temperature on the system performance are investigated based on the experimental results.
V. O Berg et al.  discussed the experimentalinvestigation of the heat and mass transfer between a liquiddesiccant (triethylene glycol) and air in a packed bed absorption tower using high liquid flow rates. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of dehumidification, as well as the effectiveness of the dehumidification process is assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, a comparison between the findings in the present study and findings previously reported in the literature is made. The results obtained from this study make it possible to characterize the important variables which impact the system design.
 Avanesh Yadev and V.K.Bajpai (2011) had conducted the experiment in operating parameters of desiccant wheel for refrigeration temperature. Desiccant wheels are utilized as a part of commercial and industrial applications to perform air dehumidification activities by using low grade heat source. Programming gave by the maker is utilized to choose a honeycombed rotational desiccant wheel according to necessities of the customer on the website by Novel Air Technologies. The fundamental parameters for a specific wheel of thickness 200 mm and measurement 550 mm are ambient air at 30C DBT and 17 g/kg humidity ratio, regeneration temperature differs from 650C to 850C, process air flow rate change between 1.5 m/s to 5.5 m/s, reactivation air flow rate lies between 1.5 m/sec to 5.5 m/sec. Process/reactivation zone was observed to be optimum between of 1 and 1.5, flow rate of process air between 1.5 m/s and 2.5 m/s and reactivation air between 2.5 m/s and 3 m/s. The focus is on maximizing the process removed moisture and for the given desiccant wheel model, the optimum process inlet speed is found to lie in the between of 1.5 and 2.5 m/s. The expansion in process removed moisture removed remains almost steady after 2.5 m/s. Best outcomes are acquired at higher regeneration temperature i.e. 85 C.  Alireza Zendehboudi at el. (2014) had conducted a study on performance of solar desiccant cooling system by TRNSYS in IRAN. Increase in air humidity leads to discomfort and can cause health problems. This paper computed the execution of a basic desiccant evaporative cooling cycle in four chose urban communities in Warm and Humid climatic zone of IRAN (i.e. Kish, Bandarabbas, Bushehr and Gheshm).The coefficient of performance (COP) has been processed for every area
In the proposed system, a specifically designed concentrating solar collector will be used to heat up seawater to temperature above 50~55°C. The hot seawater is then sprayed to humidify the incoming air in the humidification chamber. The humidified air enters the dehumidification chamber and is cooled by the incoming seawater, in the meantime the seawater is pre-heated to recover heat. The moisture is condensed out using a specially designed membrane and the pure water is accumulated at the base of the chamber. The dehumidified air is discharged to the outside or re-circulated. The experimental set up as shown in Figure 1 consists of the desalination unit with dimension of 1.5m x 0.5m x 0.8m. The unit incorporates the humidification and dehumidification chambers and also a fan to blow air into the system. An electric heater of 2.4kW heat capacity was used to supply the energy required. Two pumps were used to circulate the feed water in the system; One pump circulates the feed water through the dehumidification chamber and the other pump circulates the feed water through the electric heater to the humidification chamber.
used in the process of air dehumidification or drying. There are several desiccant column configurations in- cluding solid packed bed, multiple vertical beds, radial bed, and inclined bed which have been used for dehu- midification. Adsorption-desorption operations of a hol- low cylindrical packed bed were investigated by Awad et al. . The pressure drop in radial bed is too small com- paring with that for the vertical bed. The effect of flow- bed geometries on desiccant column were investigated by Visit and Juntakan . The hollow cylindrical bed was the feasible and practical dehumidifier for dehumidifica- tion process. With respect to desiccant wheels, a study on solid desiccant based hybrid air-conditioning systems was reported by Dhar and Singh . The evaluation and optimization of solar desiccant wheel (rotating honey- comb) performance was reported by Ahmed et al. . Nia et al.  presented the modeling of a desiccant wheel used for dehumidifying the ventilation air of an air-con- ditioning system.
loads in ventilation air by at least 3:1 and often as much as 8:1. A designer can use the engineering shorthand indexes to quickly assess the importance of this fact for a given system design. To size those components after they are selected, the designer can refer to Chapter 24 of the 1997 Handbook of Fundamentals, which, for the first time, includes separate values for peak moisture and peak temperature.
solar fraction was much lower (0.39). Since the solar LDAC was simulated for an entire year in Miami, the average daily solar irradiance over the simulated period was much lower than in Toronto and Vancouver (4.98 kWh//m 2 compared to 5.48 kWh//m 2 in Toronto and 5.71 kWh//m 2 in Vancouver). Despite the lower solar fraction, operating the LDAC in Miami offers the distinct advantage of year-round operation. The total solar output was much higher than in the other cities (57.0 GWh compared to 15.8 GWh for Toronto and 16.5 GWh for Vancouver). This result also highlights the benefits of combining the LDAC with a solar combi-system that provides heat and domestic hot water. In Toronto and Vancouver, the total collected solar energy could be increased dramatically if the solar collectors were used for heating in the winter. For example, between October 2011 and May 2012, the solar array was operated and monitored while rejecting heat to the dry cooler. During this time, 18.8 GWh were collected with an average collector efficiency of 61%. Investigating the integration of the LDAC into a larger combi-system is therefore a recommended area of future work and is further discussed in Section 7.2.
drawbacks like large input and high CO2 emissions. Humidification and dehumidification process (HDH) is a promising technique for desalination which can be implemented with low cost and no environmental impact. Mostafa H. Sharqwy et al  humidification-dehumidification (HDH) process is used for producing fresh potable water from saline water at sub-boiling temperature. This process utilizes a low-temperature source such as waste heat source solar energy. In this work, the design and performance characteristics are investigated for two humidification and dehumidification cycles namely, water heater and air heated cycles. Furthermore, increasing the temperature of the water entering the humidifier minifies GOR for the water heated cycle whereas it increases for the air heated cycle. A comparison is also made between the two cycles to provide valuable guidelines for designers in terms of, components size and power requirements. A.E.Kabeel et al : It is concluded that the humidification and dehumidification desalination process will be a satisfactory choice for fresh potable water production when the demand is localized. Humidification and De-humidification desalination process is the low-temperature process where solar energy is utilized to extract required thermal energy. The capacity of HDH units is between that generated by solar stills and conventional methods. Moreover, HDH is differentiated by simple operation and maintenance. From the condensed review, it was derived that an increase in condenser and evaporator surface areas remarkably improves system productivity there are many simulation studies has been conducted in the past, further design simulation is essential to fully understand the complicated effects of water and air flow rates. It is also useful to an optimum size of individual components of the unit and to create a comprehensive model for the system.
In this chapter, the cooling and dehumidifying capacities of two liquiddesiccant membrane air- conditioning (M-LDAC) systems are investigated and compared when installed in an office building located in a hot-humid climate (Miami, Florida). The building HVAC system consists of a radiant cooling system to cover the sensible load and either a 2-fluid or 3-fluid M-LDAC system to meet the latent load. The systems are simulated over the warmest week of the year using TRNSYS simulation software and modelled using a previously developed analytical model for the 2-fluid M-LDAC system and empirical models for the 3-fluid M-LDAC systems. Sensitivity studies are performed where the systems are evaluated under different latent load conditions due to different occupant densities and infiltration rates. The 2-fluid and 3-fluid M-LDAC systems can meet the latent loads at lower occupant densities and infiltration rates but fail to provide thermal comfort conditions as occupancy and infiltration rates increase. It is concluded that the 3-fluid M- LDAC system uses less energy to meet the latent load than the 2-fluid M-LDAC system. The 2- fluid M-LDAC system consumes 50% more energy than the 3-fluid M-LDAC system in order to provide thermal comfort to the office building during the weekly simulation.
Two centrifugal pumps each which have a maximum discharge of 800 liters /hour are used for pumping the desiccant into the two towers. In order to vary the inlet air relative humidity and temperature an electric heater is used which is made of Tungsten and is wound in a manner concentric to the inlet pipe which has a diameter of 4 inch made of GI . Glass wool is used to insulate the heater from the pipe for minimizing heat loss. The heat flux of the heater is controlled using a rheostat. Desiccant is distributed into the towers by means of an E-shape distributor made of PVC pipes and it trickles down through the packing to the outlet which is situated at the bottom .Demister pads are placed at the top of the