Now we are going to compare the values determined by our simulation with the values identified by our experimental platform. We propose as a first step, a comparison of temporal evolution curves (powers and temperatures) obtained by simulation and measure. Then we present an analysis of mean absolute error for each component.

Fig. 7 et 8: Comparison of the temporal evolution of simulated and measured temperatures

Fig. 9 et 10: Comparison of the temporal evolution of simulated and measured powers

M. Jaradat*, R. Heinzen, U. Jordan, K. Vajen

Institut fur Thermische Energietechnik, 34109 Kassel, Germany Corresponding Author, Jaradat@uni-kasselde

Abstract

Liquid desiccant systems are used for comfort and industrial air-conditioning and represent a promising alternative when driven by solar heat, to vapour compression machines usually employed in these applications. A novel design of the most important component, the internally heated regenerator, is presented and experimentally examined in this paper. The main focus for reengineering the regenerator is to avoid carry-over of the salt-solution to the air which is accompanied with both, corrosion and environmental impact problems. Furthermore, an important issue is to realize an even distribution of the liquid desiccant inside the regenerator.

The experiments presented here will therefore concentrate on the liquid desiccant (LD) distribution system inside the regenerator which consists of perforated plexiglass tubes with different, equally spaced, throttling-points and a wick material attached to the transfer area between the desiccant solution and the air stream. In order to determine the evenness of distribution, experiments were conducted with different combinations of the throttling-points diameters with a range between 0.5 mm-0.9 mm, varying the LD volume flow in different ranges between 0.3 l/min-1.2 l/min. A second set of experiments concentrated on the distribution behaviour of different types of textiles (cotton, viscose, polyamide, polyester and wood-pulp based textiles). Each type of the textiles has been tested to measure the absorption capacity and the diffusion speed by simply pouring a quantity of lithium chloride (LiCl) onto the upper surface of a taut piece of textile, and measuring the time needed for the LiCl droplets to be completely absorbed by the textile fibers. Each type has been tested in both, dry and wet state. Then polycarbonate plates were coated with these textiles and exposed to the salt solution throttled through the perforated tube. A violet fluorescent light has been used to support the visual inspection of the LD diffusion through the textile fibers.

A factorial design analysis was carried out for the results gained by testing the perforated tube. The analysis shows the optimal throttling-points diameter and the optimal spacing that will give the optimal conditions for an even distribution over the whole length of the tube. Furthermore, the analysis shows the minimum volume flow rate that might be obtained and fulfils a fairly evenness distribution. The second set of experiments revealed that new fibres have the best absorption and diffusion characteristics among the tested textiles compared to the traditional textiles currently in use such as cotton. The obtained results are implemented to build a LD regenerator that will be used for air conditioning applications.

Keywords: Desiccant, carryover, factorial design analysis, throttling-points.

1. Introduction

Conventional vapour-compression air-conditioning systems are completely powered by electricity, which is often accompanied by peak load charges, carbon dioxide emissions into the atmosphere,

since the generation of electricity involves most often the utilization of fossil fuelled power plants, as well as high operational costs.

The main disadvantage of vapour-compression air-conditioning systems is that it is considered as an inefficient thermodynamic process. The handling of the latent load part requires cooling the air below its dew point which leads to an air temperature that is colder than the temperature needed to meet the sensible load. Thus, reheating the air is necessary.

Liquid desiccant air-conditioning systems remove the latent load directly from the air by absorbing the moisture by a hygroscopic salt solution e. g. lithium chloride (LiCl), calcium chloride (CaCl2). The main components of an open-loop liquid desiccant air-conditioning system are the absorber (dehumidifier) and the desorber (regenerator) shown in Fig. 1.

In the absorber, moisture absorbed from the conditioned air stream dilutes the desiccant solution loading the desiccant with water vapour. The dilute solution is reconcentrated in the regenerator, where it is heated to elevate its water vapor pressure. A scavenging air stream, usually ambient air, contacts the heated solution in the regenerator. There, water evaporates from the desiccant solution into the air and the solution is reconcentrated. A high impact on the system’s performance results from the design of the regenerator as the driving heat is consumed in this component.

In the literature concerning liquid desiccant systems, the most examined type of both, the absorber and the regenerator is the adiabatic heat and mass exchanger. A typical representative of an adiabatic heat and mass exchanger is a packed bed with both, regular and random structures. The history of packed bed heat and mass exchangers used in liquid desiccant systems dates back to

1930’s when Kathabar Inc. [1] produced the first LiCl system, primarily for industrial applications. Despite the intensive research that has been conducted to develop these systems, there are still disadvantages of packed bed structures in absorbers and regenerators, the main ones are high pressure drop, high auxiliary energy consumption, high liquid to air ratio, flooding risks and the entrainment of desiccant mists into the air stream are the main disadvantages of packed bed structures in absorbers and regenerators.

Newer studies [2-4] favoured internally heated regenerators designed with a parallel plate structure to obtain regular cross-sections for the air flow to prevent carry-over and to reduce essentially the desiccant flow rate. Out of this design the need for a sophisticated distribution system emerges as the low desiccant flow rate needs to be equally distributed over a large area. Bi-sectional or nozzle distributors have been proposed so far. They promised good results in the investigated prototypes but had problems during longer operation as crystallization of salt particles in the distribution channels occurred or air entered the distribution system.

Uneven horizontal distribution of the liquid desiccant as it enters the generator is undesirable because it reduces the effective area of contact between the liquid desiccant and air and thus decreases the mass transfer and heat exchange between the liquid and vapour. To ensure proper operation of the generator, it is also important to ensure that the ratio of liquid to vapour is constant over the cross-section of the plates. For this reason, it is important to have an even distribution of liquid as it enters the generator. A need has thus developed in this paper for a liquid distributor that is capable of facilitating uniform LD distribution at low flow rates.

A further part of the distribution system consists of textiles which are attached to the plate. Former studies revealed the necessity for closer investigations as the used materials e. g. cotton fleece did not distribute the desiccant as a uniform film over the vertical plate but formed runlets on the surface.

Victor Afyan1 and Arsen Karapetyan2

1 SolarEn, LLC, 2/2 Shrjanayin St., Yerevan 0068, Armenia.

2 SolarEn, LLC, 2/2 Shrjanayin St., Yerevan 0068, Armenia.

* Corresponding Author, victor afyan@solaren. com

Abstract

10 kW PV power station is integrated into the roof of the five-store medical center building and connected to the 3-phase grid on the net metering basis. For cooling needs of the building there is a hot water driven lithium bromide absorption chiller with 420kW cooling capacity. The chiller is powered by a gas boiler and supplies chilled water to the fan-coils system of the building. PV station is installed and tested. Absorption chiller is installed and commissioned. Technical data for PV and cooling systems are presented.

Keywords: BIPV, net metering, cooling, absorption chiller.

1. Introduction

Building integrated photovoltaic (BIPV) and grid-tied solar power stations are well known and implemented in developed countries due to the favorable feed-in tariff and rebates. Although PV technology has a long history in CIS countries, particularly for autonomous power supply applications, its BIPV implementation is hampered by absence of grid connection legal mechanisms and financial stimuli.

PV power plant as well as other renewable energy (RE) power plants connection and parallel operation with the grid has been ensured and regulated by the net metering mechanism adopted in Armenia in 2005. According to the regulation all RE power plants and even combined heat and power (CHP) units with capacity up to 150kW can benefit parallel operation with the grid based on the net metering.

The PV power station and tri-generation energy efficient system has been designed for the renovated building of the Armenian-American Wellness Center in Yerevan. The design is based on 10kW roof-integrated grid-connected PV power station, hot water driven lithium bromide absorption chiller with 420kW cooling capacity and cooling tower, gas genset with 110kWe and 150 kWth capacity and a back-up gas boiler. The CHP issue is still pending but other components of the system are already installed and described below

P. Kohlenbach*, D. Rossington and A. Weigand

1 CSIRO Energy Technology, PO Box 330, Newcastle, NSW, 2300, Australia
Corresponding Author, paul. kohlenbach@csiro. au

Abstract

CSIRO Energy Technology is developing a small-scale desiccant-based air-conditioning system for residential applications. In this context, a desiccant wheel made of a novel material has been experimentally tested for its dehumidification performance. The material is an iron-alumino-phosphate zeolite with an AFI structure and traded under the name of FAM Z-01. A 300mm diameter desiccant wheel was tested under varying inlet conditions of temperature and humidity with regard to its dehumidification performance. It was found that for constant regeneration humidity the maximum moisture removal capacity of the material is 17 grams of water per kg dry air at 50°C regeneration temperature and 24 grams of water per kg dry air at 80°C regeneration temperature from an inlet air stream of 40 °C and 95% relative humidity. At supply inlet temperature between 10 and 30°C and supply inlet relative humidity between 20 and 50% it was found that the difference in moisture removal at a regeneration temperature of 50 °C and at 80 °C is around 1 g/kg d. a.. At varying regeneration humidity (matching ambient conditions) it was found that the moisture removal is considerably lower, even though the regeneration air is supplied at the same temperature. Maximum moisture removal was 5.1 g/kg d. a. and 14.5 g/kg d. a. for supply inlet conditions of 40°C/95% RH at 50 degC and 80 degC regeneration temperature, respectively.

Keywords: Dehumidification, desiccant wheel, zeolite, FAM Z-01

1. Introduction

CSIRO is currently developing a solar-powered air-conditioning unit for residential houses, using a desiccant-evaporative process to provide cool and dehumidified air. This process is very well suited for the recovery of low-grade solar energy or waste heat. Thermal energy and water are used to provide air-conditioning, hence consuming only a very small amount of electrical power. As part of the development CSIRO is testing novel desiccant wheel materials for dehumidification purposes. The two most common materials for desiccant wheels are silica gel and LiCl due to their low cost and ease of handling. They are however limited in their moisture removal capacity, especially at regeneration temperatures below 80 degC. Recently researchers and manufacturers have been developing advanced materials to increase the moisture removal capacity and hence to allow for smaller unit size.

Jia et. al. [1, 2] describe a comparison between a novel composite desiccant wheel made of silica gel and lithium chloride and a conventional wheel made of silica gel only. They found that the composite wheel has a greater moisture removal capacity compared to the silica gel wheel, especially at lower inlet humidity. The regeneration temperature of the composite wheel was found to be lower than that of the pure silica gel wheel. Tokarev et. al. [3] have analysed a composite sorbent based on CaCl2 as an
impregnated salt and MCM-41 as a host matrix. At regeneration temperatures between 70 and 120 degC the moisture removal capacity of the composite was greater than of silica gel. Cui et. al. [4] investigated the properties of DH5, DH7 and 13x adsorbents with regard to their use in desiccant cooling systems. Their results show that DH5 and DH7 adsorbents have greater moisture removal capacity than silica gel when tested at a regeneration temperature of 100 degC. Restuccia et. al [5] also investigated a composite sorbent SWS-1L, a mesoporous silica gel KSK impregnated with CaCl2. It showed a promising moisture removal capacity of up to 0.7 g of water per 1 g of dry sorbent at regeneration temperatures of 90-100°C. Kakiuchi [6] presented the FAM-Z01 material used in this work as an application for adsorption heat pumps and proposed the application for desiccant wheels. This application was further investigated by Oshima et. al [7] who evaluated the performance of a desiccant rotor containing FAM-Z02 zeolite material. Various regeneration temperatures and air inlet conditions have been investigated in a parameter study. The moisture removal of the FAM-Z02 rotor was found to be 11-22% higher than that of a silica gel rotor at regeneration temperatures of 50-70°C.

One important aspect of using adsorbents in a solar cooling system is the long-term stability of the desiccant. Earlier investigations by Belding et. al [8] have shown that silica gel and 13x adsorbents can lose up to 63% and 13%, respectively, of their original moisture removal capacity after 50,000 cycles. The FAM Z-01 material used in this work has been tested by the manufacturer and has shown a 5% capacity loss after 50,000 cycles [6].

2. System and methodology

The experimental testing has been undertaken at CSIRO’s Energy Technology site in Newcastle, Australia. Figures 1 and 2 show the test rig used for experimental purposes.

As shown in Figure 1 and 2, the test rig consists of two separate conditioned air streams, one for desiccant wheel supply, and the other for desiccant wheel regeneration. Each of these two air streams enter via an intake filter (item 1 of Figure 1), and is then pressurised by a centrifugal fan (item 2) which is controlled by a variable speed drive to enable air volume control. Peak flow of 1000m3/hr is achievable with a 300Pa pressure drop across the desiccant wheel. The air stream then passes through two cooling coils. The first coil (item 3) is cooled with a 2°C chilled glycol solution capable of dehumidification of the leaving air stream to a moisture ratio of approximately 7 g/kg dry air. The second cooling coil (item 4) is cooled with a -5°C chilled glycol solution capable of further dehumidification of the leaving air stream to a moisture ratio of approximately 4 g/kg dry air. The dehumidified air stream then passes through a primary electric heater bank (item 5). This heater bank is capable of heating the air stream to 90°C in the case of the regeneration air stream, and 40°C in the case of the supply air stream. The air stream is then humidified as required using a steam injection lance (item 6). Low pressure steam at 1.5 bar is injected in the air stream via nozzles at a rate of up to 45 g/kg dry air. Finally the air stream passes though a secondary electric heater bank (item 7). The secondary heater bank is of similar capacity as the primary heater bank allowing for load sharing and fine temperature control. The supply and regeneration air streams are then ducted to the test desiccant wheel. This can be done in counter flow and parallel flow arrangement. The supply and regeneration air streams leaving the desiccant wheel are ducted from the wheel and exhausted outside. Temperature and Humidity are measured and recorded after each of the control elements described above. The temperature and humidity entering and exiting the desiccant wheel is calculated by averaging a number of sensors distributed over the cross section of the ductwork entering and leaving the desiccant wheel. Volume flow rate of the supply and regeneration air streams is calculated from velocity measured at the entering side of the desiccant wheel.

The basic control schemes have been applied on the following three basic configurations for the installation:

2.2. Direct use configuration

The basic scheme used to execute the simulations in this case is the one on the following figure.

Fig.2. Configuration for direct use

This corresponds to the habitual configuration for installations with absorption chiller. In this case to start the chiller working they must be fulfilled two requirements: to have solar energy enough stored on the tank and to have cold demand.

The main results within the first level are the

… primary energy ratio of the installed solar assisted heating and cooling ((Equation 1)

. primary energy ratio of an assumed reference system working under the conditions as the installed SHC system ((Equation 2).

Herewith the annual savings of primary energy through the utilisation of the SHC system can be expressed.

Further through the calculated cost per installed cooling capacity ((Equation 4), it will be possible in the following years to draw a learning curve for SCH systems.

3.1. Expected results — 2nd level

The main result within the second level is the calculation of the solar thermal energy which could not be exploited by the SHC system — this shows the “efficiency” of the SHC system ((Equation 12 and (Equation 13, see Fig. 5)

Pedro Adao1*, Manuel Collares Pereira1, Andrea Costa2

1 Ao Sol SA (SunCool SA), Lugar da Sesmaria Limpa, 2135-402 Samora Correia, Portugal
2 ACE, Pfalzerstr. 75, 83109 Grosskarolinenfeld, Germany
* Corresponding Author, pedro. adao@aosol. pt

Abstract

This work presents the development results of a novel absorption chiller for solar cooling applications built at Ao Sol (SunCool laboratories) in Portugal. The chiller is at pre­commercial stage at the time of writing. Focus of the ongoing development work is the optimisation of technical and economic parameters such as overall dimensions. A thermo­economic analysis will give insight on the commercial potential and challenges.

Under present conditions, dictated by a new European legislation and current fuel price, the use of small absorption chillers coupled to solar thermal technology for residential applications turns out to be potentially both environmentally sound and economically viable. Necessary requirements are cost-efficient solar collectors and chillers, and an economically optimized combined system.

Relying on previous work performed at the University of Lisbon, a compact absorption chiller working with a solution of ammonia and water has been built and tested. The device is mainly made of plate heat exchangers and it is directly cooled by air, thus avoiding the need of a wet cooling tower. The control strategy is aimed to an overall concept that includes collector field, storage, gas back-up, chiller and building.

The thermodynamic design is presented along with experimental results of the thermal performance — in terms of chilled water production and coefficient of performance. The economic impact of the developed chiller for a common residential application in Portugal is compared with a reference system and discussed.

Keywords: solar cooling, air-cooled chiller, ammonia-water absorption, net present value

1. Introduction

The present European Directive on Energy establishes ambitious goals for the year 2020: 20% contribution of renewable energies to the final energy demand and 20% reduction of the final energy consumption through energy efficiency measures [1]. This creates a very strong drive for the solar penetration in the Heating and Cooling of Buildings, responsible for about 40% of the total final energy consumption in the EU [1].

Combining this directive with the ESTIF solar thermal installed capacity goals for 2020 [2 ESTIF Newsletter July 2007] an upper limit of about 4 million new solar driven machines can be anticipated for the residential and services market.

If the more ambitious ESTIF expectations are taken into consideration this figure will be multiplied by a factor of 5 to 10 to 2030.

The present situation in Europe shows a huge potential for renewable energies. In the building sector, with its highest emissions share, the potential for energy savings is over proportional high. Building cooling is rising to become a crucial issue in the next years. Solar energy is indisputably assessed as a major contributor to these savings and it is being fully backed by policy makers through long-term directives at EU-level.

Trends in Southern Europe: Southern European countries are in a particularly dire situation with a growth of energy consumption in the buildings sector precisely because of the widespread use of electrically-driven air-conditioning units; a situation which will even worsen with the warming trends associated with global warming. In the Portuguese residential and services sector the average increase rate of electricity consumption over the last three years is more than 4 times the average rate of the European Union [3]. This is mainly due to the rise in air-conditioning demand traditionally achieved with highly inefficient small-size chillers (window units). This generates a tendency, which is against the goal of 20% energy use reduction and requires even stronger action than in Northern European countries.

In the past, INETI and some of the people involved in the present development participated in a European funded project [4] to analyze the technical and economic potential of solar absorption cooling in the Mediterranean region. Essentially the conclusion was that — through savings induced by solar energy — an all-year system providing heating, cooling and domestic hot water would compare favourably with a conventional system with a boiler for heating and an electric chiller for cooling with a payback time of less than 10 years. The conclusions and ideas developed in that study were truly influential on the decision of AO SOL to take up the present R&D effort.

On this day (07/07/2008) no cooling energy was needed in the rooms because the ambient air temperature was approximately 20 °C. Hence, the ice-storage could be charged. At the beginning of the day the storage was partially charged with approximately 15 kWh of cooling capacity. At the end of the day the storage was completely iced and a cooling capacity of 35 kWh had been available. This cooling energy had been used in the morning hours of the next days. Figure 6 shows the power supplied to the generator and the evaporator, and the solar radiation on this day.

The solar radiation on this day was very changeable. This is the reason why the operation of the chiller did not start before 11:30. It is remarkable that in spite of the inconstant solar radiation the power of the evaporator is very constant. The average COP on this day was 0.50. Figure 7 shows the operating temperatures of the chiller.

5. Conclusions

The developed absorption chiller is able to cool the rooms where the cooling system is installed, and has still some buffer capacities for higher cooling loads. In the mornings (until 9:45) and in the evenings (after 16:30) cooling performance is lacking and has to be covered with the ice storage. The ice storage could be charged on days when no cooling was required. Even on days with changeable solar radiation the charging of the ice-storage is possible. Despite the promising results so far, additional work is required. For example, the automatic control of the system must be upgraded and more measurement data have to be acquired to optimize the complete system.

References

[1] Zetzsche, Koller, Brendel, Muller-Steinhagen: Solar cooling with an ammonia/water absorption chiller, 2nd International Conference Solar Air-Conditioning, Oct. 18th/19 th 2007, Ostbayerisches Technologie-Transfer-Institut e. V., Regensburg, Germany, p. 536-541 [14]

W. Mittelbach, T. Btittner and R. Herrmann

SorTech AG, Weinbergweg 23, 06120 Halle, Germany, walter. mittelbach@sortech. de

ABSTRACT

Beside the well-known liquid absorption chillers with LiBr-water as sorption pair also solid adsorption chillers may be used for generating chilled water with low-temperature heat. In the range of cooling capacities of 70 kW and higher Japanese products are on the market for many years using silica gel as adsorbent and water as refrigerant. But due to the much larger volume and weight of the machines compared to LiBr absorption chillers adsorption chillers only found niche markets up to now. The main reason for the large volume of the adsorption chillers sold up to now is the low heat transfer rate between silica gel and the heat exchanger surfaces. SorTech AG developed a coating process, which enables to apply heat exchanger surfaces directly with the adsorbent. This enabled the development of more compact and lightweight adsorption chillers. Based on this technology SorTech AG developed a small adsorption chiller with a nominal cooling capacity of 7.5 kW. The objective is to provide a compact machine, which may be used for solar air-conditioning in private homes and small offices.

Keywords: adsorption chiller, solar cooling, silica gel

The traditional method of collecting large quantities of data by holding each factor constant, in turn until all possibilities, is an approach that quickly becomes impossible due to the number of factors increases (full factorial) as in this case of seven-factor test with about 3 levels in each factor. It i

solved by choosing a set of test points that allow to estimate the model with the maximum confidence using just a fraction of the number of test runs; for this case only 100 optimally-chosen (space-filling) runs is enough to fit the model.

The chosen operating conditions are those typical for an air conditioning (Tev = 10°C, TCon = 30°C): condensation pressure of 250 hPa, evaporation pressure of 40 hPa and ambient temperature of 25°C. The simulation factors were summarized in Table 1 with the correspondent range of variation. As material of the fins were tested the aluminium, the cooper and the stainless steel AISI 316L. The input data relevant to implicit numerical aspects are: 6 s of time step, 12 nodes for axial and radial direction.

Table 1 — Simulation factors and the respectively range of variation

Hot water temperature, Tae Hot water mass flow, ma Cycle period, t Number of tubes, nt Number of fins, nc Thickness of the fins Fin and tube material

The designed test plan was simulated and the results were tested by a variety of radial basis functions (Gaussian, Thin-Plate Spline, Logistic, Wendland, Multiquadrics, Reciprocal Multiquadrics) and Quadratic to find out the function that has the lowest root mean square error (RMSE); it was chosen Quadratic for coefficient of performance (COP) and specific cooling power (SCP) with the following RMSE of 0.012056 and 2.7091, respectively.

4. Results

The statistical model results are extensive and spread; for this reason a base-case, taken as reference, was chosen by the great COP with the relatively higher SCP, considering that the maximum of both occurs in different operating conditions. It was found: a hot water temperature of 100 °C with 0.8 kg/s, the cycle period of 40 minutes, 56 tubes and 100 cooper fins of 0.5 mm.

To evaluate the influence of the simulation factors, the results are showed in the surrounding of the base-case. Fig. 4 reports the effects on the COP of: (a) cycle period for some number of fins; (b) hot water temperature for some cycle periods; (c) number of fins, switching the material; (d) hot water mass flow, switching the material; (e) number of tubes, switching the material; (f) number of fins for a given thickness. Analyzing these graphics it was concluded that the coefficient of performance (COP) increases with:

• the number of fins, however for long cycles (40 min.) fewer fins is more efficient;

• the cycle period;

• the hot water temperature; for levels greater than 105 °C, it does not change the COP;

• the number of fins; the maximum happens in 135 fins independently of the material;

• the material, in this case, aluminium is the best;

In the same way, the Fig. 5 depicts the effects on the SCP of: (a) hot water mass flow, switching the material; (b) cycle period for some number of fins; (c) number of tubes, switching the hot water mass

flow; (d) number of tubes, switching the material; (e) number of fins, switching the material; (f) hot water temperature for some number of tubes. The main conclusions that can be taking is that the specific cooling power (SCP) increases with:

• the material; in this case, cooper is the best;

• the number of fins.

(c) (d) n. n t c (e) (f) Fig. 4 — Influence of the simulation factors on the COP.

(b)

t

(d)

c

(e) (f)

Fig. 5 — Influence of the simulation factors on the SCP.

5. Concluding remarks

The present study investigated statistically the results of an adsorber mathematical model in order to optimize its design, founding the best operation point and the influence of each of the seven design factors (hot water temperature and mass flow, cycle period, number of tubes, number of fins, thickness of the fins and material of the fins).

The results showed that all the factors are statistically significant and interdependent. In other words, a change in one factor affects directly the others. It shows the importance of the statistical model for analyzing the main design parameters. As main results, it was found that the system performance (COP) is strongly dependent on the number of fins, the material and the cycle period. For the specific cooling power (SCP), the more relevant factors are the number of fins, the number of tubes and the hot water temperature.

The optimized adsorber parameters were the following: the hot water temperature of 100 °C with 0.8 kg/s, the cycle period of 40 minutes, 56 tubes and 100 cooper fins of 0.5 mm. It results on a COP of 0.52 and SCP of 51 W/kg.

6. Acknowledgements

The authors gratefully acknowledge the CNPq for the financial support provided to this work through

Research Project Grant No. 504229/2004-4 and the CAPES for the scholarship given for the first

author (DBR) of this paper.

References

[1] Leite, A., Belo, F. A., Martins, M. M., Riffel, D. B. e Meunier, F., 2006, Central air conditioning based on adsorption and solar energy, In: Proc. of 2nd Int. Solar Cities Congress, Oxford, UK.

[2] Dubinin, M. M., Astakhov, V. A., 1971, Description of adsorption equilibria of vapors on zeolites over wide ranges of temperature and pressure, Adv. Chem. Series, Vol. 102, pp. 69.

[3] Gnielinski, V. Warmeubertragung bei der Stromung durch Rohre, VDI-Warmeatlas: Berechnungsblatter fur den Warmeubergang, Springer-Verlag, 2002.

[4] Guilleminot, J. J., Meunier, F., Pakleza, J., 1987, Heat and mass transfer in a non-isothermal fixed bed solid adsorbent reactor: a uniform pressure/non-uniform temperature case. Int. J. Heat Mass Transfer, Vol. 30 (8), pp. 1595-1606