Dehumidification of air with a newly suggested liquid desiccant

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1 ARTICLE IN PRESS Renewable Energy 33 (28) Dehumidification of air with a newly suggested liquid desiccant A.A.M. Hassan, M. Salah Hassan Department of Mechanical Power Engineering and Energy, Faculty of Engineering, Minia University, Post Office 6, El-Minia, Egypt Received 23 July 27; accepted 4 December 27 Available online 8 January 28 Abstract Calcium chloride solution is a cheap desiccant. It is unstable at certain solution concentrations and dehumidified air temperatures. The aim of this research is to stabilize it by mixing with calcium nitrate in different weight combinations. The physical properties of a proposed liquid desiccant such as density, viscosity, and vapor pressure were obtained. Heat and mass transfer analysis between a thin liquid layer of the proposed desiccant and the air flowing through rectangular channel has been studied. The different factors affecting the dehumidification process of air were studied. r 27 Elsevier Ltd. All rights reserved. Keywords: Liquid desiccant mixtures; Air dehumidification; Desiccant vapor pressure; Rectangular channel dehumidifier. Introduction Dehumidifying air by direct contact with desiccant finds an application in solar air conditioners. These systems take air either from outside or from building, dehumidify it with a solid or liquid desiccant, cool it sensibly and evaporatively to the desired state. The desiccant in these systems is regenerated by solar energy. Any of these systems composed of liquid desiccant heat exchangers, air dehumidifier, evaporative cooler and liquid desiccant regenerator. In addition, desiccant-air systems can be used in drying crops. Removal of moisture from air before passing over the dried products decreases the need for high inlet temperatures of air. In the dehumidification process, the air is passed over a thin layer of strong liquid desiccant. The desiccant absorbs the moisture from the air passing over it. The desiccant is diluted during this process. This liquid can be regenerated to the required concentration by using solar energy. Extensive studies were made to develop solid desiccants system but little attention was given to liquid desiccant systems. Several works were done to investigate the performance of single desiccant system [ 5]. A little attention was given to the characteristics of a mixture of Corresponding author. address: Salahkun@hotmail.com (M.S. Hassan). two desiccants. A Etras et al. [5] mixed lithium chloride and calcium chloride in different weight combinations. They measured the partial pressure of a selection from this mixture at different temperatures. Also they measured the physical properties of these mixtures. These data are helpful for the analysis of heat and mass transfer between desiccant air system and packed tower. They showed that lithium chloride is the most stable liquid desiccant. Although it has a large dehydration concentration (3 45%), its cost is relatively high. It reduces air relative humidity to as low as 5%. Calcium chloride is the cheapest and most readily available desiccant, but it has the disadvantage of being unstable at certain air inlet conditions and desiccant concentrations. They measured the physical properties and partial pressure of a new costeffective and stable mixture of these two desiccants. Al- Farayedhi et al. [6] studied the heat and mass transfer between air and liquid desiccant in a gauze-type structured packing tower. Three different types of liquid desiccant are compared. It was found that the mixture of calcium chloride and lithium chloride has a significant increase in the mass transfer coefficient compared with the other two solutions. Giovanni and Gasparella [7] carried out an experimental tests on the dehumidification of air and the regeneration of the solution by using traditional hygroscopic solution H 2 O/Li Br, new solution H 2 O/KCOOH. They reported the experimental results in terms of 96-48/$ - see front matter r 27 Elsevier Ltd. All rights reserved. doi:.6/j.renene

2 99 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) Nomenclature C pa specific heat of dry air (kj/kg K) C pv specific heat of water vapor (kj/kg) D eq equivalent diameter (m) G a air mass velocity at inlet (kg/m 2 s) H c channel depth (m) H c channel height (m) h heat transfer coefficient (kj/m 2 K) k m mass transfer coefficient of gas phase (kg/m 2 s) L channel length (m) Le Lewis nimber, h/k m C pa _m a air mass flow rate (kg/s) Nu Nusselt number, hd eq /l a Pr Prandtl number, mc p /l Re Reynolds number, rvd eq /m t a temperature of air stream (K) dt a differential change in t a (K) t temperature of liquid stream (K) V a air inlet velocity (m/s) W c channel width (m) x coordinate in the direction of air flow (m) X w Y a dy a Y i z Greek letters concentration of water in the liquid phase (kg water/kg liquid mixture) specific humidity of air, k =k gh2 O g d:a differential change in Y a, k =k gh2 O g d:a value of Y at the interface, k =k gh2 O g d:a coordinate in the direction of channel width (m) l thermal conductivity (kj/m s K) r density (kg/m 3 ) f relative humidity Subscripts a c i l m w air channel interface liquid mass transfer water humidity reduction, desiccant concentration and tower efficiency. Ali and Vafai [8] studied the heat and mass transfer between air and falling desiccant film for inclined parallel and counter flow configurations. It is shown that inclination angle plays a significant role in enhancing the dehumidification, cooling, and regeneration process. Yango et al. [9] carried out experimental study on a new type of air conditioning system. They introduced a liquid desiccant evaporation cooling system. The mean mass transfer coefficient of the packing regeneration process in their study was 4 g/m 2 s. The different factors affecting the dehumidification and regeneration processes were studied... Study objectives Previous work showed that calcium chloride is a cheap but unstable desiccant if it was used alone. Therefore, this study aimed to decrease the cost and improve the stability by mixing it with calcium nitrate, which is an expensive desiccant. The partial pressure of vapor was measured for different combinations of the two desiccants. From these data, proposed mixture that fulfills higher air dehumidification was obtained. The performance of a rectangular channel dehumidifier was studied theoretically. A steady-state model for heat and mass transfer between liquid desiccant layer and air contacting it was made. The data of vapor pressure obtained from experiments were used as an input data for this model. The governing equations are solved on a digital computer to simulate the performance of the dehumidification system. Using the proposed desiccant, the effect of operating, and design parameters on the performance of the dehumidifier are studied..2. Experimental work The driving force for dehumidification is the partial pressure difference between the vapor pressure of bulk air and the vapor pressure at the air interfacing desiccant solution. Therefore, the lower vapor pressures at interface means the higher performance of dehumidification. The interface vapor pressure was taken as the saturation pressure corresponding to the temperature and concentration of the desiccant solution. The partial pressure of vapor was measured for different mixtures of calcium nitrate and calcium chloride solutions. All concentrations in this work were given as percentage of the weight of water..3. Vapor pressure measurements The partial water vapor pressure of a solution is the pressure of water vapor at solution interface, which is in equilibrium with the solution at a given temperature. It is a function of temperature and concentration of solution. The apparatus used for measuring the partial pressure is shown in Fig.. The liquid desiccant () to be boiled is poured in the glass vessel (2). It is heated to the required temperature by plate heater (3). A 25 W vacuum pump (4) was used to reach the vacuum saturation pressure corresponding to the saturation temperature of the liquid desiccant. Vapor trap (5) was connected in the line between the glass vessel and the vacuum pump to decrease the vapor content in air before entering the vacuum pump. An

3 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) Liquid desiccant, 2- Glass vessel, 3- Plate heater, 4- Vacuum pump, 5- Vapor trap, 6- Air bleeding valve, 7- Dial vacuum pressure gauge, 8- Digital thermometer Fig.. Vapor pressure measurement apparatus. air-bleeding valve (6) was used to remove the dissolved air from the liquid desiccant at the beginning of experiment. It also regulates the rate of vacuum during the experiment. The saturation pressure was measured by dial type vacuum pressure gauge (7) with accuracy of. bar. Desiccant solution saturation temperature was measured by digital thermometer (8) with copper constantan thermocouples with accuracy of. C. The test procedure was as follows:. The system was tested for leaks. 2. The flask was half filled with the solution. 3. An electric heater was used to control solution temperature during the test period. 4. Solution temperature and pressure were measured by digital thermometer and vacuum gauge, respectively. 5. The vacuum pump was operated and the pressure was lowered at constant rate. 6. The pressure and temperature were recorded at the beginning of boiling. Vapor pressure, mm-hg %CaCl 2 4 %CaCl 2 25 %CaCl 2 Steam.4. Experimental results and discussions Figs. 2 4 show the vapor pressure results for pure calcium chloride desiccant solutions and for the proposed desiccant solutions, which is a mixture of calcium chloride and calcium nitrate. Fig. 2 shows the vapor pressure versus saturation temperature for different concentrations of pure calcium chloride desiccant as a percentage of the weight of water. For different desiccant solutions, the vapor pressure increases exponentially with increasing temperature. The vapor pressure depression was defined as the reduction of vapor pressure from that of steam due to adding salt to the pure water. To show that depression, the results are Temperature, C Fig. 2. Vapor pressure of calcium chloride solution. compared with the data of steam vapor pressure taken from steam tables. Table shows the vapor pressure depression in mmhg for 25%, and 5% CaCl 2 desiccants at different temperatures. The results show that 5% calcium chloride concentration gives the lowest vapor pressure at different values of temperatures. Because of the solubility limits we could not try concentrations more than 5%.

4 992 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) Fig. 3 shows the vapor pressure versus saturation temperature for different liquid desiccants. These desiccants are different mixtures of calcium chloride and calcium nitrate solutions. All the concentrations were given as a percentage of the water weight. Two groups of five different liquid desiccants were studied. In the first group, two liquid desiccants were made by adding 2% and 5% calcium nitrate to calcium chloride 25% concentration, respectively. In the second group, three liquid Vapor pressure, mm-hg % CaCl 2 +5% 5 % CaCl 2 +2% 5 %CaCl 2 +% 25 % CaCl 2 +5% 25 % CaCl 2 +2% 25 % CaCl 2 desiccants were made by adding %, 2%, and 5% calcium nitrate to calcium chloride 5% concentration, respectively. The figure shows that the vapor pressure increases exponentially with saturation temperature for all desiccants. When adding calcium nitrate, 5% instead of 2% to calcium chloride of concentration 25%, the vapor pressure changes were negligible. Noticeable reduction in vapor pressure was obtained by adding calcium nitrate to calcium chloride of concentration 5%. The maximum solubility of 5% calcium chloride occurs at 28 C, which is suitable desiccant liquid temperature in air dehumidification systems. Figure shows that making liquid desiccants with calcium nitrate concentrations higher than 2% does not give reasonable reduction in vapor pressure. Therefore, the liquid desiccant, which composed of 5% of the weight of water calcium chloride, 2% calcium nitrate was chosen as the most suitable desiccant solution within the concentrations tested in this work. Table 2 shows vapor pressure depressions in mmhg for a liquid desiccant, which composed of 5% of the weight of water CaCl 2 versus proposed desiccant at different temperatures. Fig. 4a shows a summary of the results. The performance of desiccant solution improves only when adding calcium nitrate to 5% calcium chloride Temperature, C Fig. 3. Vapor pressure of various mixture ratios. Table Vapor pressure depression in mmhg for a liquid desiccant which, composed of 25% of the weight of water CaCl 2, versus liquid desiccant composed of 5% CaCl 2 3 C 4 C 5C 6C Dp 25% CaCl Dp 5% CaCl Vapor pressure, mm-hg % CaCL % 5 % CaCL 2 25 % CaCL % 25% CaCL Temperature, C Vapor pressure, mm Hg Wt = 4%, [Ca(No 3 )/CaCl 2 ] =.4 (Present Study) Wt = 3% [LiCl/CaCl 2 = ] Ref.[5] Wt = 35% [LiCl/CaCl 2 = ] Ref. [5] Wt = 4% [LiCl/CaCl 2 = ] Ref.[5] Temperature, C Fig. 4. (a) Vapor pressure versus desiccant solution temperature for various mixture ratios. (b) The best liquid desiccant of the present study compared with the liquid desiccants of Ref. [5].

5 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) Table 2 Vapor pressure depressions in mmhg for a liquid desiccant which, composed of 5% of the weight of water CaCl 2 versus proposed desiccant at different temperatures 3 C 4 C 5 C 6 C Dp 5% CaCl Dp (proposed desiccant) Desiccant film m. a Air m. a Y a Y a + dy a t a dx t l t a + dt a.m The measured density and viscosity of the proposed desiccant solution are 354 kg/m 3 and 3.25 cp, respectively, at 28 C. To explore the degree of improvement, the vapor pressure of the best liquid desiccant of this study was compared with the liquid desiccant of Ref. [5]. In Ref. [5], a desiccant solutions were tested with different combinations of lithium chloride and calcium chloride mixtures. In their study, the concentration was defined as the ratio of the mass of salt to the total mass of the solution. They obtained the cost effective liquid desiccant (CELD) when the ratio by weight of LiCl/CaCl 2 ¼. According to this definition, the concentration of the best desiccant of the present study is 4% and the ratio [Ca(No 3 )/CaCl 2 ] ¼.4. This comparison is shown in Fig. 4b. The data in the figure show that the liquid desiccant of the present study gives a vapor pressure lower than that of CELD with 3% concentration. When the concentration of CELD increased to 35%, it gave vapor pressure higher than that of the present study at solution temperatures below 42 C. In this case, the liquid desiccant of the present study is preferable in air conditioning applications. The CELD of 4% concentration is better than the liquid desiccant of this study with taking into consideration that [Ca(No 3 )/ CaCl 2 ] ¼.4 compared with LiCl/CaCl 2 ¼. The economy of using these mixtures will depend on the price of Ca(No 3 ) as compared with LiCl. 2. Governing equations of heat and mass transfer of a channel type dehumidifier An elemental volume in the dehumidifier along air flow is shown in Fig. 5. Air enters the channel and paths over a very thin layer of desiccant solution. During its path, simultaneous heat and mass transfer between the air and desiccant solution takes place. The driving force for mass transfer is the partial pressure difference between the bulk air and the air at desiccant solution interface. The following assumptions were considered:. Heat loss through channel walls was neglected. 2. Heat resistance through very thin layer of solution was neglected. Accordingly, temperature at interface was equal to the bulk solution temperature. 3. Desiccant solution temperature was kept constant by water-cooling jacket under the dehumidifier. It was taken as a parameter and its variation along channel length was neglected. Cooling water jacket Fig. 5. An elemental volume of the dehumidifier. 4. Surface of the channel base was completely covered with the solution layer. 5. Lewis number was taken as unity in the evaluation of mass transfer coefficient. The governing equations of heat and mass transfer are: Mass balance between the air and the desiccant solution: _m a dy a ¼ k m dx dzðy a Y i Þ, () dy a dx ¼ k m ðy a Y i Þ. (2) H c G a An energy balance of the air: _m a ðc pa þ Y a C pv Þ dt a ¼ hdx dzðt a t l Þ, (3) dt a dx ¼ h ðt a t l Þ. (4) H c ðc pa þ Y a C pv ÞG a The interfacial specific humidity at liquid interface was obtained from the experimental data as: Y i ¼ f ðt l ; X w Þ. (5) The heat transfer coefficient between the air and the desiccant solution was given as follows []: For laminar flow: Nu ¼ :86ðRe PrÞ =3 D =3 eq. (6) L For turbulent flow: Nu ¼ :23Re :8 Pr n, where n ¼.4 for heating and n ¼.3 for cooling. D eq ¼ 4W ch c 2ðW c þ H c Þ ¼ 2W ch c, (7) W c þ H c h ¼ Nu k a. (8) D eq When Le ¼., then k m ¼ h. (9) C pa Eqs. () (9) were solved numerically by fourth order Runge Kutta method. x

6 994 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) The input data to the computer program are:. Inlet air temperature, and humidity 2. Inlet airflow rate 3. Desiccant solution temperature, and concentration 4. The data of Y i as function of (t l, x w ) 5. The channel design parameters 6. The physical properties of air 3. Results of theoretical work For all runs, values for velocity, relative humidity, and temperature of air at inlet were taken as m/s, 8%, 45 C, respectively. The solution temperature was taken as 3 C. Fig. 6a c shows the effect of inlet air temperature, velocity, and relative humidity on the performance of the dehumidifier. The dimensionless specific humidity was defined as the ratio Y a /Y ai. Fig. 6a shows the effect of air inlet temperature on the performance of dehumidifier. It shows an increase of air inlet temperature from 3 to 4 C and from 3 to 5 C and from 3 to 6 C decreases the channel length 6%, 7%, and 72% to keep the outlet air dimensionless specific humidity at.83. For the same channel length, the outlet humidity ratio decreases exponentially with increasing air inlet temperature. At certain inlet temperature, the humidity ratio decreases nonlinearly with channel length. However, the curves approach linear relation at low inlet air temperatures. Fig. 6a c shows the evaluation of dimensionless specific humidity, Y a /Y ai, along the channel length for various values of inlet condition. Fig. 6a shows the distribution of dimensionless specific humidity along channel length for values of air inlet temperatures 3, 4, 5, and 6 C. The dimensionless specific humidity decreases as air temperature increases. An increase in the inlet air temperature keeping the inlet relative humidity constant causes an increase in the inlet air specific humidity and consequently the level of vapor pressure difference between the bulk air and the layer of air at the interface, which is the driving force for mass transfer, will increase inside the dehumidifier. This causes an increase in the mass transfer rate from the air to the liquid desiccant film resulting in an increase in moisture removal. Fig. 6b shows the distribution of dimensionless specific humidity along channel length for values of air inlet velocities.5,, 2, 4, 6, and 8 m/s. Dimensionless specific humidity decreases exponentially with channel length at low inlet velocities but it tends to decrease linearly at high velocities. The curves converge at high inlet air velocities and diverge at low inlet velocity. Figure shows an increase of air inlet velocity from to 2 m/s increases the channel length by 39% to keep the outlet air dimensionless specific humidity at.7 Fig. 6c shows the distribution of dimensionless specific humidity along channel length for values of inlet relative humidity 5%, 6%, 7%, and 8%. Decreasing inlet relative humidity from 8% to 5% decreases channel length 3% to keep the outlet air dimensionless specific humidity at.67. Fig. 7a d shows the effect of air inlet velocity, inlet temperature, inlet relative humidity, and desiccant temperature on the performance of the dehumidifier. Fig. 7a shows the effect of air inlet velocity on the amount of moisture absorbed from air and the load of the dehumidifier. The load was defined as the difference between the total enthalpy of air at inlet and outlet of the dehumidifier. The average moisture removed from air Dimensionless specific humidity Y a /Y ai V a = m / s φ = 8 % t l = 3 C t a =3 C Dimensionless channel length t a = 45 C φ = 8 % t l = 3 C V a = 8 m/s Dimensionless channel length t a = 45 C V a = m / s t l = 3 C φ = 8 % 7% 6 % 5% Dimensionless channel length Fig. 6. Effect of air inlet conditions on air humidity distribution along the channel length.

7 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) Amount of moisture absorbed, grams/m 2 s t a = 45 C φ = 8 % 8 t l = 3 C Air inlet velocity, m/s Load, W Amount of moisture absorbed, grams/m 2 s V a = m / s φ = 8 %.8 t l = 3 C Air temperature, C Load, W Amount of moisture absorbed, grams/m 2 s t a = 45 C V a = m / s.8 t l = 3 C Air inlet relative humidity, (-) Solution temperature, C Load, W Amount of moisture absorbed, grams/m 2 s V a = m / s φ = 8 %.8 t a = 45 C 8 Load, W Fig. 7. Moisture removal for different values of air inlet conditions, and desiccant solution temperature. in the range of velocities from 2 to 3 m/s is.72 l/h m 2. This range of velocities is suitable for air-cooling systems and drying processes. Fig. 7b shows the effect of inlet air temperature on moisture removal and load. The increase in moisture removal is rapid at high inlet air temperature compared to low inlet temperature. The average moisture removed from air in the range of inlet air temperatures from 3 to 45 C equals.2 l/m 2 h, while.72 l/m 2 h in the range of inlet air temperatures from 45 to 6 C. These results show that the dehumidifier is more efficient in drying applications than that in air conditioning applications. Fig. 7c shows the effect of inlet air relative humidity on the moisture removal and the dehumidifier load. The moisture removal as well as the load increases linearly with increasing air inlet relative humidity. Moisture removal and load decrease linearly with increasing solution temperature as shown in Fig. 7d. These figures show that the most dominant factors affecting the performance of the desiccant are air inlet velocity and temperature. The absorbed moisture has a linear relation with air inlet relative humidity as well as solution temperature. The load shows the same trend with mentioned factors. Fig. 7d shows that, for the same desiccant solution and the same inlet and outlet conditions of air, a reduction C in solution temperature increase the amount of moisture absorbed by 6.7%. Fig. 8a shows the dimensionless specific humidity versus dimensionless channel length for different values of solution desiccant temperatures. It can be seen that the channel length is shortened by 25% to keep the outlet air dimensionless specific humidity at.7 when decreasing the solution temperature from 4 to 35 C. At certain channel length, the dimensionless specific humidity decreases linearly with decreasing solution temperature from 44 to 33 C. Fig. 8b shows that the channel length is shortened by 27% to keep the outlet air dimensionless specific humidity at.7 when using the suggested desiccant instead of pure calcium chloride desiccant. It shows that the higher concentration liquid desiccant the smaller channel length to reach the same outlet dimensionless humidity. This is due to that the vapor pressure at interface, which controls

8 996 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) wt 5% Ca Cl 2 + % Ca (NO 3 ).9.9 wt 5% Ca Cl 2 + Dimensionless specific humidity t a = 45 C φ = 8 % t l 44 C Dimensionless specific humidity V a = m / s φ = 8 % t a = 45 C t l = 35 C 2% Ca (NO 3 ) Dimensionless channel length Dimensionless channel length Fig 8. Dimensionless specific humidity distribution for different values of desiccant solution temperature (a) and desiccant solution concentration (b). Absorbed moisture (g/m.s) Present work Ref. [5] Load (W) different weight combinations was obtained experimentally. A proposed desiccant, which is a mixture of 5% of the weight of water calcium chloride and 2% calcium nitrate, gave a significant increase in vapor pressure depression compared with other solution within the concentrations tested in this work. The vapor pressures of this desiccant at temperatures 3, 4, 5, and 6 C were 4.7, 2.6, 34.4, and 47.3 mmhg, respectively. The heat and mass transfer between this liquid desiccant and the air passing through rectangular channel duct were studied theoretically. The different factors affecting the performance of the system were also studied..5 the driving force for mass transfer, is exponential function of solution temperature as it was declared from the experimental results Fig. 3. Fig. 9 shows comparison between using calcium nitrate (present study), and lithium chloride (Ref. [5]) as additives to obtain two proposed liquid desiccants. The results show that the proposed desiccant is more efficient in dehumidification at temperatures less than 45 C. 4. Conclusions Air temperature, C Fig. 9. Comparison between using calcium nitrate and lithium chloride as additive to calcium chloride for proposed desiccant solution. The data of vapor pressure of a desiccant solution composed of a calcium chloride and calcium nitrate with References [] Ali A, Vafai K, Khaled ARA. Comparative study between parallel and counter flow configurations between air and falling film desiccant in the presence of nanoparticle suspensions. Int J Energy Res 23;27: [2] Ali A, Vafai K, Khaled ARA. Analysis of heat and mass transfer between air and falling film in a cross flow configuration. Int J Heat Mass Transfer 24;47: [3] Dai YJ, Zhang HF. Numerical simulation and theoretical analysis of heat and mass transfer in a cross flow liquid desiccant air dehumidifier packed with honeycomb paper. Energy Convers Manage 24;45: [4] Gommed K, Grossman G. Experimental investigation of a liquid desiccant system for solar cooling and dehumidification. Solar Energy 26;8:3 8. [5] Etras A, Anderson EE, Kiris I. Properties of a new liquid desiccant solution-lithium chloride and calcium chloride mixture. Solar Energy Operation 992;49(3):25 2. [6] Al-Farayedhi AA, Gandhidasan P, Al-Mutair MA. Evaluation of heat and mass transfer coefficient in gauze type structured packing air dehumidifier operation with liquid desiccant. Int J Refrig 22;25(3): 33 9.

9 ARTICLE IN PRESS A.A.M. Hassan, M.S. Hassan / Renewable Energy 33 (28) [7] Giovanni AL, Gasparella A. Experimental analysis on chemical dehumidification of air by liquid desiccant and desiccant regeneration in a packed tower. J Solar Energy Eng 24;25(): [8] Ali A, Vafai K. An investigation of heat and mass transfer between air and desiccant film in an inclined parallel and counter flow channel. Int J Heat Mass Transfer 24;47: [9] Yango Y, Zheng X, Chen Z. Experimental study on dehumidifier and regeneration of liquid desiccant cooling air conditioning system. Build Environ 27;42(7):255. [] Chapman AJ. Heat transfer. 3rd ed. New York: Macmillan; 974.

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