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International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 60 Application of Evaporative Air Coolers Coupled With Solar Heater for Dehumidification of Indoor Air

A S Alosaimy Department, Faculty of Engineering, Taif University, KSA [email protected]

Abstract-- In the present work, novel configuration of solar have been proposed and most of them are economically powered dehumidification system is investigated. The justified. These systems include sorption systems containing proposed system comprises two evaporative air coolers. One of / or solid/vapor absorption/adsorption, vapor the two coolers functions as an absorber and the second, which is compression systems, and hybrid desiccant vapor compression coupled with solar water heater, functions as a desiccant systems [6]. regenerator. In the experimental part of this investigation, Chloride is regenerated using solar energy. Hot water The regenerator is one of the key components in liquid from a solar collector is circulated through an air heater to desiccant air-conditioning systems, in which desiccant is regenerate the liquid desiccant. Mathematical model, which can concentrated and can be reused in the system. The heat be applied for analysis of the proposed system, is developed. required for regenerating the weak desiccant solution is Absorption-regeneration cycle for the is described supplied into the regenerator by either hot air or hot desiccant and analyzed. An expression for the efficiency of the simple cycle solution. This heat can be provided by any form of low-grade is introduced. Theoretical analysis shows that strong and weak thermal energy which is suitable for solar thermal applications. solution limits play a decisive role in the value of Different regenerator designs have been examined and a cycle efficiency. System efficiency with consideration of heat and variety of theoretical models have been employed to analyze work added to the system is well defined. The limits of regeneration and mass of strong solution per kg of the regeneration process [7-9]. An analytical procedure for produced vapor are found highly dependent on the operating calculating the mass of water evaporated from the weak concentration of desiccant. Experimental results show that solution in the regenerator in terms of climatic conditions and solution with 30% concentration can be regenerated up to 50% solution properties at the regenerator inlet has been developed using solar energy. Good agreement is found between the trained by Kakabayev and Khandurdyev[1].Alizadeh and Saman [10] data of the ANN model and the experimental measurements for developed a computer model using Calcium Chloride as the the whole range of the air inlet temperature. working desiccant to study the thermal performance of a forced parallel flow solar regenerator. A parametric analysis of the Index Term-- Desiccant; humidification; absorption; air system has been performed to calculate the rate of conditioning; Calcium chloride. of water from the solution as a function of the system variables 1. INTRODUCTION and the climatic conditions. However, the solar radiation In hot and humid areas,interest in utilizing solar powered- intensity was assumed constant in the analysis. The effect of cooling systems for air-conditioning and purposes regeneration temperature on the rate of water evaporation from has been growing continuously. Being considered as one path the liquid desiccant shows that an increase in solution towards more sustainable energy systems, solar-cooling is temperature increases the vapor on the surface of the comprised of many attractive features. This technology can solution and consequently the potential of mass transfer. Solar efficiently serve large latent loads and greatly improve indoor water heaters can be applied for regeneration of the desiccant air quality by allowing more ventilation while tightly solution if the heated water in the solar heater is used for controlling [1]. On the other hand, solar-powered air regeneration purposes. In this case, hot water can be used to conditioning has seen renewed interest in recent years due to heat the regeneration air in an air heater and then blown to the the growing awareness of environmental problems such as packing of the , where the solution is recalculated by global warming [2,3]. Solar collector/regenerator (C/R) the solution . The main function of desiccant systems can achieve liquid regeneration at lower dehumidification system is to pump humidity from the which is suitable for buildings with high outdoor air conditioned space, which has moisture sources, to the outside requirements in high humidity areas [4,5]. Several solar-driven space. Different design configurations for such systems are refrigeration systems available in literature [5,6]. These systems use solid or liquid desiccant as sorbent. A new desiccant dehumidifier for supermarket application is presented in [11]. It is a self-

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 61 regenerating liquid desiccant cooling system able to Alosaimy [11]. Isothermal operation of HP on the dehumidify, heating or cooling the ambient air by an electric psychrometric chart isdemonstrated in Fig. 1. As shown in fig., heat pump that is a part of the equipment. It appears in the the system transfers moisture from the indoor air, which has shape similar to a traditional air-handling unit but it puts lower humidity, to the outdoor airthrough the line R-O, where together inside in a new way a chemical dehumidification the conditions R and O represent the room (dehumidified air) system and an electric vapor compression heat pump: in such a and outside conditions, respectively. The system which carries way it can be defined as a hybrid machine. A novel desiccant out this process is called a humidity pump (HP). The statement based system was designed and tested "humidity pump" comes from the similarity between pumping experimentally to improve the and reduce heat from the cooled space to the hot outside air and pumping energy consumption [12]. In the system studied, the moisture humidity from an indoor air to a more humid outside air. of the air sent to the place being air-conditioned was reduced However, isothermal absorption of from air can be passing it through a solid desiccant wheel and then its carried out with continuous cooling of the desiccant during the temperature was brought to the desired blowing temperature by process. At the end of absorption the desiccant must be the “dry coil” of a vapor compression cycle. A liquid desiccant regenerated to remove the absorbed water and re-concentrate based air-conditioning system is described in [13]. The the solution. dehumidifier and regenerator used in the system are adiabatic. The absorption-regeneration cycle, which can be applied, The air flows upward and the solution flows downward in the for operation as a humidity pump, is shown in Fig. 2. The packing of the dehumidifier and the regenerator: that is, the air- theoretical cycle is plotted on the -concentration solution is under counter flow. The coefficient of performance diagram for the operating absorbent and consists of four (COP) of the liquid desiccant based system decreases sharply thermal processes which are [11,12]: when the fresh air ratio exceeds 60%. The results also show Process 1-2: isothermal absorption of water vapor from that the proposed system can save power notably. The room air; maximum power saving ratio is 58.9% when the fresh air ratio Process 2-3: constant concentration heating of the is 20%. The application of commercially available air absorbent; , which are used for evaporative cooling in Process 3-4: constant vapor pressure regeneration of areas (dry zones), for the purposes of dehumidification of absorbent and humid air and regeneration of desiccant solution is proposed in Process 4-1: constant concentration cooling of absorbent. the present work. This application to a decrease in the overall cost of the dehumidification system and there is no need of specific design. In the present work solar collector has been applied for regeneration of CaCl2 solution. The proposed system ho comprises a flat plate solar collector which is used for water heating to heat the regeneration air in an air heater. The heated w air is used to regenerate the solution in the dehumidifier. In the hR O o theoretical part, simplified analysis of the performance of o desiccant operated humidity pump has been presented. Several objectives are formulated to address the overall goal of the present study; application of solar water heater coupled with evaporative coolers to function as desiccant dehumidifier. H

These objectives are to: P ω φ R R 1- Design and installation of a solar water o  coupled with an air heater and for R R regeneration of calcium chloride (CaCl2) desiccant solution.

2- Study and discuss the operation of the proposed system and evaluate the possibility of steady state operation with t = application of hot water storage tank. Fig. 1. Isothermal Operation of Humidity Pump on the Psychrometric ChartC

2. OPERATION OF HUMIDITY PUMP (HP) The thermal processes of this cycle are carried out between Desiccant dehumidification system, in general, functions as two concentration limits: x1 and x2 and the cycle has another humidity pump. The function of the humidity pump is to operation limits which are its maximum regeneration transfer the humidity of room air (indoor conditions) to the temperature, t4; vapor pressure, pv,O and outside air(outdoor conditions). The energy required to power maximum absorption vapor pressure, pv,R. Evaluation of these such systems is mainly the regeneration heat required to heat operation limits is important from the point of view of system the desiccant regenerator. The basic concept of isothermal design and construction. Therefore, description of the effect of humidity pump is discussed and analyzed by Hamed and air conditions on the cycle operation is presented as follows: if

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 62 the is equal to t1 and strong solution pressure is reduced again to p1 by cooling from t4 to the room concentration is x1, absorption process starts only when the temperature where the cycle ends at point 1. vapor pressure on the absorbent surface is lower than the 3. THE PROPOSED SYSTEM vapour pressure in the room air pv,R (Fig. 2). Theoretically, The proposed system is presented in Fig.3. The system absorption continues from 1 to 2, i.e. ends at equilibrium comprises two air evaporative coolers. One of the two coolers condition when the pressure of vapor on the absorbent surface functions as an absorber (the indoor unit) and the second (the is the same as that in room air. When the absorption process outdoor unit), which is coupled with solar water heater, ends, absorbent is pumped to the regenerator and heated from functions as a desiccant regenerator. Calcium Chloride solution an external source. Regeneration of weak absorbent can be is regenerated in the evaporative cooler (desiccant regenerator) carried out at constant pressure. The vapour pressure on the which is supplied with hot air from a finned tube air/water heat absorbent surface at point 2 is equal to pv,R which is exchanger. Water from the solar water heater is circulated determined in terms of room relative humidity and temperature. through the to heat the flowing air. Strong Constant pressure regeneration at this pressure requires that the solution from the outdoor unit is directed to the indoor unit and regeneration temperature is the saturation temperature of water weak solution from the indoor unit is pumped to the vapour corresponding to the vapor pressure of the outdoor air; regenerator via a solution pump. Room humid air is blown and pv,O. When regeneration is assumed to be at ambient dehumidified in the indoor unit. This system actually functions temperature, weak solution must be heated from t2 to t3 where as humidity pump. Direct contact between air and desiccant is as concentration is constant and vapour pressure increases from carried out in the packing used in the evaporative cooler to pv,Rto pv,O, which is the saturation pressure of vapour increase the contact area. For the purpose of heat recovery, corresponding to ambient (outdoor) conditions . The increase solution heat exchanger is applied to cool the strong solution in temperature from t2 to t3 depends on the relative humidity coming out from the regenerator (outdoor unit). of air or the weak solution concentration, x2, which depends also on the relative humidity at the given ambient temperature. 4. THEORETICAL ANALYSIS During the constant pressure condensation, solution In the theoretical part of this study, thermodynamic analysis concentration increases from x2 to x4. The maximum of the proposed system as well as artificial neural network regeneration temperature depends on the available heat source model will be considered and presented in the following and the limits required of desiccant concentration. Strong subsections. (regenerated) solution at point 4 is not able to absorb vapour 4.1 THERMODYNAMIC ANALYSIS from room air due to its higher vapourpressure, therefore An important aspect of any system simulation is the

φ φR to o Pv,o

3 4

tR

P

v,R 2

t = Const.

1 Vapor pressureon the desiccant surface Relativehumidity C = Crystallization zone

Desiccant concentration by weight

Fig. 2. Operation processes of isothermal absorption humidity pump on the Vapor pressure-concentration chart

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 63 determination of the conditions for optimized performance. 50 Date: 10/10/2010 When sorption / desorption cycle is applied with absorption of Initial mass of solution =2 kg, water vapour from air, system efficiency can be simply Initial concentration =0.3 Final concentration =0.38 evaluated from the multiplication of the cycle efficiency by the efficiency of the equipment (ex. collector

efficiency, when solar energy is applied). In case of forced air 40

C

absorption, energy added to forced air stream must be ,

e r

accounted in definition of system efficiency. Therefore, system u

t

a r

efficiency is defined as the ratio of heat added to generated e p

water vapour qv to the total equivalent heat added to the m e system H, i.e T 30 Air temperatures at ηsys  qv H (1) regenerator inlet&exit The heat added to generated water vapor is assumed equal inlet temperature, C to the latent load removed by the system from the dehumidified outlet temperature, C space. From Fig. 2 ,during regeneration, heat must be applied to 20 the desiccant to accomplish the following: 8 9 10 11 12 13 Time, hr heat the solution to minimum regeneration temperature

(process 2-3, Fig. 2),; Fig. 6. variation of water and air temperatures at inlet and exit of the heat vaporize the liquid water; exchanger and humidifier for the first group of tests heat the solution to its final temperature in the (process 3-4, 50 Fig. 2 ), and Air temperatures at regenerator inlet&exit heat the regenerated vapour to its final temperature. inlet temperature, C The heat added to desiccant and water vapour during the outlet temperature, C desorption process can be expressed as given in [12] as

40

C

Q  mh  M h  M  m h (2) ,

d  v d r  d  a  e r

u t

where h is the . Subscripts v, r and a denote a

r e

water vapour, desiccant condition at the end of regeneration p

m and desiccant condition at the end of adsorption, respectively. e T 30 60 Date: 11/10/2010 Water temperatures at Initial mass of solution =3.684 kg, heater inlet&exit Initial concentration =0.3 Final concentration =0.48 inlet temperature, C 50 outlet temperature, C 20

8 10 12 14 16

C

, Time, hr

e

r u

t Fig. 7. Variation of water and air temperatures at inlet and exit of the heat a r 40 exchanger and humidifier for the first group of tests

e p

m e

T

30 Date: 10/10/2010 Initial mass of solution =2 kg, Initial concentration =0.3 Final concentration =0.38 20 8 10 12 14 Time, hr

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 64

Air vent

Water tank

Solar water Compensation heater line

O utdoor unit

Packing Air heater

Air outlet Air inlet

Weak solution Strong solution Water circulating pump

Solution heat exchanger

Indoor unit

Dehumidified Room air out humid air in

Solution pump

Fig. 3. Schematic diagram of solar powered desiccant dehumidification system.

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 65

Knowing desiccant concentration limits and mass of In terms of desiccant parameters, cycle efficiency can be desiccant Md one can evaluate the mass of adsorbed (or expressed as given in [15], regenerated) water vapour as follows,   Xahr  Xrha (11) ηcyc  L hv   Xr  Xa X  X m    M (3)  r a  X d a 4.2 NEURAL NETWORK (ANN) MODEL where Xr and Xa are desiccant concentration at the end of regeneration and end of adsorption, respectively. As the The artificial neural network (ANN) is a new form of computing, inspired by biological models and composed of a mass of desiccant changes during the processes, in eq.(3) Md is taken at start of adsorption. The heat equivalent to energy large number of processing elements organized into layers. A added to air stream, blown through the desiccant packing, can computing system, made up of a number of simple, highly be evaluated by dividing the mechanical work by the Carnot interconnected processing elements, which processes energy factor [14], information by its dynamic state response to external inputs. 1 The ANN is supposed to consist of artificial neurons or Qe  vo A P (4) processing elements. Fig.4. shows the architecture of the Ca neural network model used in our previous work [16, 17]. The wherevo is the air velocity at bed entrance, A is the face basic structure is a multilayer ANN model where the chosen area of packing in contact with air, P is the pressure drop six inputs are fed into the first layer of hidden units. There, the through the packing and Ca is the Carnot energy factor. This circles represent the neurons (weights, bias, and activation factor is dependent on the operating temperature limits of the functions) and the lines represent the connections between the cycle. As the temperature limits of the operating cycle are the inputs and neurons, and between the neurons in one layer and room temperature, which is equal to the absorption temperature those in the next layer. Several studies have found that a three- Ta and maximum regeneration temperature, which is equal to layered neural network, where there are three stages of neural the desiccant temperature at the end of regeneration process Tr. processing between the inputs and outputs, can approximate Consequently, Carnot energy factor can be expressed as any nonlinear function to any desired accuracy. Each layer of the neural network consists of units which receive their input Tr  Ta Ca    (5) from units from a layer directly below and send their output to Tr units in a layer directly above the unit. Each connection to a The total equivalent heat added to the system is expressed neuron has an adjustable weighting factor associated with it. as The output of the hidden units is distributed over the next layer of hidden units, until the last layer of hidden units, of which the H  Q  Q (6) d e outputs are fed into a layer of no output units. Training of the Room conditions (temperature and relative humidity) are ANN model typically implies adjustments of connection indoor controlling parameters, which determine the maximum weights and biases so that the differences between ANN possible mass of vapor absorbed by the desiccant (see fig. 2). outputs and desired outputs are minimized. Details of the ANN In other words, for specific sorbent the lower value of model is presented and discussed in [17] desiccant concentration at the end of sorption process is dependent on indoor parameters. When Calcium Chloride is EXPERIMENTAL WORK the working desiccant, the lower concentration can be In the experimental part of this investigation, calcium expressed as given in [15] by chloride solution is regenerated in an air humidifier (desiccant regenerator) which is supplied with hot air from a finned tube air/water heat exchanger. Water from the storage tank of a   b o   b1  (7) X min  lnp v  a o   a1   solar  t 111.9   t 111.9       where, t is the sorbent temperature, oC, ao, bo, a1, b1 are regression constants given in [15]. The vapour pressure in room air is dependent on the relative humidity  and saturation pressure of water, ps(t), i.e

pv  φpst (8) Cycle efficiency is defined as the ratio of heat added to generate vapour to the heat added to desiccant, during regeneration process, i.e., ηcyc  qv Qd (9) where qv = m L (10) Fig. 4. A schematic of multilayer neural network [17]

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S

Fig. 5. Air heater coupled with humidifier. International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 66

are recorded during the experiments: heating water at inlet and exit of the air heater; flowing air at inlet and exit of the 60 humidifier. Also, the relative humidity of air at inlet and exit of Outdoor temp. = 40 C the humidifier are recorded during the experiments. At the end of the experimental test, the mass and concentration of Outdoor temp. = 30 C

regenerated solution are evaluated and the mass of evaporated C

, Outdoor temp. = 20 C e

r mass of water is determined. K-type thermocouples connected u

t 50 50% to a digital with a resolution of 0.1C are used for

a r

e % temperature measurements. A digital having a p 0% 60 H=4 m or R resolution of 0.1% is used for measuring the relative humidity. e do t In

70% The solution is evaluated by measuring the mass and

n o

i . A digital balance of 1 gmresolution and 7000 gm t

a 40

r measuring range is used for mass measurements. An

e n

e thermometer is used to check the temperatures of the tubes of

g 0% e =4 the air heat exchanger. r H or R ndo 0% m I 7

u RESULTS AND DISCUSSION

m 30 i

n The minimum limit of the regeneration temperature for the i

M applied desiccant, at indoor temperature of 20 C, is plotted in % =40 RH Fig 5 at different values of room relative humidity, and outdoor oor % Ind 70 temperatures versus the outdoor relative humidity. As shown in 20 the fig., it can be observed that the minimum regeneration 40 50 60 70 80 90 temperature increases with decrease in the room relative Outdoor humidity,% humidity, at constant values of ambient parameters (temperature and humidity). This can be explained by the need to a solution with higher concentration to absorb moisture from Fig. 5. Minimum regeneration temperature versus outdoor relative humidity at air with lower values of relative humidity at the same ambient different values of indoor humidity and outdoor temperatures temperature. In general, it can be stated that the temperature potential required to pump humidity from the room condition to the ambient air is directly proportional with the humidity water heater is circulated through the heat exchanger to heat potential between the room and the ambient air. On the other the flowing air. The south faced solar water heater connected hand, an increase in the outdoor temperature increases the with the storage tank is installed on the roof of the Fluid required regeneration temperature for constant values of room Mechanics Laboratory, Mechanical Department, Taif and outdoor humidity. University, Saudi Arabia. Hot water from the tank exit is For an initial mass of solution of 2 kg and initial pumped by a water circulating pump through the air heater and concentration of 30%, an experimental test is carried out for a then returns to the tank inlet. Ambient air which is drawn period of 5 hrs (from 8 am to 1 pm). For the first group of tests, fig. 6 demonstrates the variation of water and air temperatures through the heater is used to heat the solution which is at inlet and exit of the heat exchanger and humidifier, circulated in the humidifier. The air heater is installed at the respectively. From the plot it can be noted that a maximum inlet of the humidifier. Solution from a pan in the humidifier is water temperature at heat exchanger inlet of about 57 ˚C is pumped to the top of the packing and flows downward, recorded at 9 a.m, whereas, this temperature fluctuates around whereas hot air from the air heart is blown across the packing. 45 ˚C for the last period of the test. This variation in heating The solar heater is connected to water compensation line and it water temperature is limited due to the use of hot water is equipped with an air vent near the top of the storage tank. storage tank. The hot water accumulate the solar energy which is variable with time and supply the regeneration unit with PVC tubes are used to connect the indoor units (air heater and water at an average temperature of 45 ˚C during the variation regenerator ) and the outdoor unit (solar heating system). The of solar radiation. In this test, water stored in the tank was air passage between the heater and the regenerator is insulated heated in the day before the test and kept at higher temperature. using polyethylene layer. The temperature of water at exit of the heat exchanger nearly A sample of solution with a specified initial mass and follows that of the inlet water with a variable temperature concentration is put in the solution pan of the humidifier. The difference. One of the most important factors affecting the solution concentration is evaluated by using the tables of regeneration process is the temperature of air at humidifier thermo-physical properties [18], by knowledge of the density (regenerator) inlet. As shown in Fig. 6, it can be noted that the and temperature. To start the experiment, the water level in the heating process, to some extent, is carried out at nearly steady hot water storage tank is checked, then water pump, solution state condition for the period from 9 am to 1 pm . The variation pump and air are switched on. The following temperatures in hot air temperature is limited to about 5 ˚C for this specific

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 67 period. During this period of experiments the radiation intensity on the surface of the solar collector extremely 14 increases until reaching its maximum value at noon time. For the second group of tests, the test results of an operation period 12 of 8 hrs (from 8 am to 4 pm) for an initial mass of solution of

g

3.684 kg are plotted in Fig. 7. It can be noted that the k 10 /

g

maximum temperature is limited to 42 ˚C at 1 pm and the ,

o i variation in heating water temperature from 8 am to 16 pm is t

a 8

r

limited to about 5 ˚C. The limited variation in the heating water y t

i temperature, compared with the variation in radiation intensity d i 6 proofs the importance of the heat storage during the day time m u Inlet humidity ratio of regeneration air for more stable and steady operation of the H

solar system when coupled with the desiccant regenerator. 4 Date: 11/10/2010 The heating air temperature increases from 30 ˚C at 9 to about Initial mass of solution =3.684 kg, 38 at the end of the test. This increase in heating temperature 2 Initial concentration =0.3 improves the operation of the regeneration system, where the Final concentration =0.48 desiccant concentration increases also with time and the 0 increase in heating temperature is essential to build the 8 10 12 14 16 required mass transfer potential to continue the regeneration Time, hr process. Fig 8.demonstrates the humidity ratio of air at regenerator exit, for the tests, with time. The fluctuation of the Fig. 8. Humidity ratio of air at regenerator exit measured data is explained by the error in the humidity measuring instruments. The solid line in Fig.8 is the humidity ratio of the ambient air. At the end of regeneration process, desiccant concentration is evaluated by measuring its temperature and density and using the tables of thermo- physical properties[18]. For a regeneration period of 5 hours, solution concentration increases up to 38% as shown in Fig. 6.

Data presented in Fig. 7shows that the regeneration of solution takes place for 8 hours and as a result, solution concentration reaches 48% at the end of regeneration process. Fig. 9.shows a comparison between the trained data of the ANN model and the experimental data for all the output variables with respect to the air inlet temperature. Good agreement is found between the trained data of the model and the experimental measurements for the whole range of the air inlet temperature.

16

g

k 12

/ g

Fig. 9. ANN model training results.

,

o

i

t

a r

CONCLUSIONS

y t i 8

d Novel design of solar powered desiccant operated humidity

i m

u pump has been presented and analyzed. In the proposed design, H Inlet humidity ratio of regeneration air air humidifiers are applied for dehumidification of processed 4 air and regeneration of liquid desiccant. The effects of Initial mass of solution =3.684 kg, meteorological conditions and system design parameters are Initial concentration =0.3 well defined. Also, system efficiency is defined in terms of operating cycle efficiency and system design parameters. 0 Effect of indoor and outdoor parameters on the required 32 36 40 44 48 52 56 Water inlet temperature,C regeneration temperature has been highlighted. The appropriate selection of desiccant concentration at the end of

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01 68 sorption has been discussed.Based on the obtained simulation [15] Hamed AM. Absorption–regeneration cycle for production of water from results, the following conclusions can be drawn: air-theoretical approach. Renewable Energy Journal 19(2000) 625–35. [16] A.S.Alosaimy and A.M Hamed, Theoretical and Experimental 1-Desiccant minimum regeneration temperature is Investigation on theApplication of Solar Water Heater Coupled with Air proportional to the humidity potential between the indoor and Humidifier for Regeneration of Liquid Desiccant. Energy 36 (2011) outdoor conditions (temperature and humidity). 3992-4001. 2- Experimental results show that CaCl2 solution with 30% [17] A. S. Alosaimy, A. M. Hamed, A. M. El-Kersh and A. A. Aly, Application Of Solar Energy For Air Conditioning In Humid Zones, Final concentration can be regenerated up to 48% using solar energy. Report, Taif University, 2010. 3- Stability of heating temperature is important. The [18] E.Z. Zaetsev, G.G. Aseev, Physical-chemical properties of binary non- application of storage tank coupled with the solar water heater organic solutions, Khemia, Leningrad, USSR, 1988. limits the variation in the heating temperature in a range of 5 oC in the specified experimental conditions. NOMENCLATURES 4-Good agreement between the outputs from the ANN Ca Carnot factor, dimensionless model and the corresponding results from the experimental Cp specific heat, J/kg.oC measurements are found. It is also concluded that the proposed h enthalpy, J/kg model can be successfully used for predicting the overall H total equivalent heat, W performance of the system on the basis of experimental data L of evaporation of water, J/kg collected for different system parts from the literature. m mass flow rate of evaporated water during regeneration, kg/s ACKNOWLEDGMENTS M mass flow rate of desiccant kg/s The authors would like to acknowledge the financial p vapour pressure, mmHg support of the University of Taif, Saudi Arabia. q heat added to vapour, W Q heat added, W REFERENCES t ambient temperature, oC [1] A. Kakabaev, A. Khandurdyev, Absorption solar refrigeration unit with open regeneration of Solution, Gliotekhnika (in Russian) 5(4) (1969) 28- T desiccant temperature, K 32. X desiccant mass concentration [2] R. Yang, P.L. Wang, Experimental study of a forced solar collector/regenerator for open cycle absorption cooling, Trans. ASME J GREEK SYMBOLS Solar Energy Engineering 116 (1994) 194-199. [3] G. Grossman, Solar-powered systems for cooling, dehumidification and air-conditioning, Solar Energy 72(1) (2002) 53–62.  efficiency [4] M. Krause, W. Saman, K. Vajen, Open cycle liquid desiccant air  relative humidity conditioning systems-Theoretical and experimental investigations, in: Proceeding of the ANZSES Conference, Dunedin, New Zealand, 2005. [5] K. Daou, R.Z. Wang, Z.Z. Xia, Desiccant cooling air conditioning: a Subscripts review, Renewable and Sustainable Energy Reviews 10 (2006) 55-77. [6] J.R.KDieckmann, J. Brodrick, Liquid Desiccant Air Conditioners, a condition at the end of absorption ASHRA Journal, October 2008. [7] R. Yang, W.J. Yan, Simulation study for an open-cycle absorption solar- b bed cooling system operated in a humid area, Energy 17(7) (1992) 649-655. d desiccant [8] A.A. Aly, E.B. Zeidan, A.M. Hamed, Performance evaluation of open- cyc cycle cycle solar regenerator using artificial neural network technique, Energy e equivalent and Buildings 43 (2011) 454–457. [9] R. Yang, P.L. Wang, A simulation study of the performance evaluation o initial, inlet of single-glazed and double-glazed collectors/regenerators for an open- r condition at the end of regeneration cycle absorption solar cooling system, Solar energy 71(4) (2001) 263- s saturation condition 268. sys system [10] A. Alizadeh, W. Saman, Modeling and performance of a forced flow v vapor solar collector/regenerator using liquid desiccant, Solar Energy 72(2) (2002) 143-154. [11] R.M. Lazzarin, F. Castellotti, A new heat pump desiccant dehumidifier for supermarket application, Energy and Buildings 39 (2007) 59–65 [12] E. Hurdogana, O. Buyukalaca, T. Yılmaz and A. Hepbasl, Experimental investigation of a novel desiccant cooling system, Energy and Buildings 42 (2010) 2049–2060. [13] X. Niu, F. Xiao, G. Ge, Performance analysis of liquid desiccant based air-conditioning system under variable fresh air ratios, Energy and Buildings 42 (2010) 2457–2464. [14] Hamed AM and Alosaimy AS. Modeling and Simulation of Desiccant Operated Humidity Pump (DOHP).Int. J. of Thermal & Environmental Engineering. Volume 4, No. 1 (2012) 39-45.

1312001-6767-IJMME-IJENS @ February 2013 IJENS I J E N S