Proposed energy-efficient air-conditioning system using liquid desiccant

Kinsara, Adnan A.; Elsayed, Moustafa M.; Al‐Rabghi, Omar M.

doi:10.1016/1359-4311(95)00090-9

Cited by 104 publications

(30 citation statements)

References 8 publications

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“…Where P at is theatmosphericpressure, Kinsara et al [20]. From property of air at w s and the solution temperature can calculate the equilibrium enthalpy of air with the CaCL 2 solution.…”

Section: Appendix 2: Equilibrium Equationsmentioning

confidence: 99%

Computer Simulation of Heat and Mass Transfer in a Cross Flow Parallel-Plate Liquid Desiccant-Air Dehumidifier

Mohammad

Mat²,

Sulaiman³

et al. 2014

Progress in Sustainable Energy Technologies Vol II

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A MATLAB program using finite difference technique is investigated to predict the distribution of air stream parameters as well as desiccantsolution parameters inside the parallel plate absorber. The present absorber consists of 14 parallel plates with a surface area per unit volume ratio of 80 m 2 /m 3 . Calcium chloride as a liquid desiccant flows through the top of the plates to the bottom while the air flows through the gap between the plates making it a cross flow configuration. The model results show the effect of desiccant mass flow rate on the performance of the dehumidifier (moisture removal rateand the effectiveness). The results show that the maximum temperature and humidity ratio differences of the air are 2.56 C and 11 g/Kg with a maximum solution mass flow rate of 160 g/s. The maximum temperature and minimum concentration differences of solution in the direction flow of solution are 3.185 C and 0.34 % with a maximum solution mass flow rate of 160 g/s. The moisture removal rate increases rapidly with solution flow rate from 1.41 to 2.196 g s À1 , but the moisture removal stagnates at high desiccant solution mass flow rates. The effectiveness achieves an increase of 0.39-0.66 when the solution mass flow rate increases from 30 to 160 g s À1 .

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“…Where P at is theatmosphericpressure, Kinsara et al [20]. From property of air at w s and the solution temperature can calculate the equilibrium enthalpy of air with the CaCL 2 solution.…”

Section: Appendix 2: Equilibrium Equationsmentioning

confidence: 99%

Computer Simulation of Heat and Mass Transfer in a Cross Flow Parallel-Plate Liquid Desiccant-Air Dehumidifier

Mohammad

Mat²,

Sulaiman³

et al. 2014

Progress in Sustainable Energy Technologies Vol II

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“…Ghaddar et al (1997) performed a study on solar-operated lithium-bromide absorption cycle performance under climatic conditions of Beirut. A desiccant-based air-conditioning system was proposed and evaluated by Kinsara et al (1996). The proposed configuration utilized a vapour compression refrigeration system for sensible cooling and a liquid desiccant system for dehumidification.…”

Section: Introductionmentioning

confidence: 99%

Use of desiccant dehumidification to improve energy utilization in air-conditioning systems in Beirut

Ghaddar

Ghali

Najm

2003

Int. J. Energy Res.

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SUMMARYHumidity and indoor moist surrounding affect air cleanliness and protects harmful microorganisms when relative humidity is above 70%. In humid climates, the humidity issues are a major contributor to energy inefficiency in HVAC devices. The use of liquid desiccant dehumidification systems of supply air is a viable alternative to reduce the latent heat load on the HVAC system and improve efficiency. Thermal energy, at a temperature as low as 40-508C, required for the operation of a liquid desiccant hybrid air conditioner can be efficiently obtained using a flat-plate solar collector.In this work a model of a solar-operated liquid desiccant system (using calcium Chloride) for air dehumidification is developed. The system utilizes packed beds of counter flow between an air stream and a solution of liquid desiccant for air dehumidification and solution regeneration. The desiccant system model is integrated with a solar heat source for performance evaluation at a wide range of recorded ambient conditions for Beirut city. Standard mass and energy balances are performed on the various components of the system and a computer simulation program is developed for the integrated system analysis.The desiccant system of the current study replaces a 3 TR (10.56 kW) vapour compression unit for a typical house as low latent load application, and is part of a hybrid desiccant-vapour compression system for a high latent load application, namely a small restaurant with an estimated cooling load of 11.39 TR (40 kW), including reheat. The relevant parameters of the desiccant system are optimized at peak load, and it is found out that there is an important energy saving if the ratio of the air flow rate in the regenerator to that in the dehumidifier is about 0.3 to 0.4. The COP of the desiccant unit is 0.41 for the house, and 0.45 for the restaurant. The size of the vapor compression unit of the restaurant is reduced to 8 TR when supplemented by a desiccant system.The performance is studied of the desiccant system integrated with a solar collector system and an auxiliary natural gas heater to heat the regenerator. The transient simulation of the solar desiccant system is performed for the entire cooling season. The solar fraction for the house is equal to 0.25, 0.47, and 0.68 for a collector area of 28.72, 57.44, and 86.16 m 2 , respectively. The solar fraction for the restaurant is 0.19, 0.38, and 0.54, for the same collector areas. The life cycle savings for the house run solely on desiccant system were positive only if natural gas is available at a cheap price. For the restaurant, the economic benefit of the desiccant system is positive, because the need for reheat in the vapor compression system is eliminated. For a gas price of 0.5638 $/kg, the payback period for the restaurant turned out to be

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“…In this way, the evaporation temperature is higher than the air dew-point temperature, leading to the improvement of refrigeration efficiency. Liquid desiccant dehumidification is to dehumidify moist air by using such solutions as lithium bromide (LiBr) and/or lithium chloride (LiCl) which have lower vapor pressure than that of moist air [2][3][4][5]. In this dehumidification process, there are simultaneously heat and mass transfer between moist air and liquid desiccant, where the heat transfer potential is temperature difference and the mass transfer potential is vapor pressure difference.…”

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confidence: 99%

Moisture transfer resistance method for liquid desiccant dehumidification analysis and optimization

Chen

et al. 2010

Chin. Sci. Bull.

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The concepts of entransy, entransy dissipation and transfer resistance are introduced into liquid desiccant dehumidification analysis to reveal the irreversibility and moisture transfer resistance between moist air and liquid desiccant. By analyzing a typical water (vapor) transfer process coupled with heat transfer, we define the concepts of mass entransy of water and its dissipation, derive the expression of moisture transfer resistance (MTR) that reflects the irreversibility of water transfer during dehumidification processes, and also point out the relationship between MTR and dehumidification performance. With these concepts, both adiabatic and internal cooling liquid desiccant dehumidification systems with various operation conditions are analyzed and optimized. It is found that for the adiabatic dehumidification system, increasing the mass transfer coefficient leads to the reduction of MTR, and consequently, the improvement of dehumidification performance. Meanwhile, for the dehumidification system with internal cooling, in order to reduce the MTR and improve the dehumidification performance, pre-cooling should be centralized ahead of the liquid desiccant inlet when the flow rates ratio of air to desiccant is small, whereas, uniform cooling should be applied when the flow rates ratio of air to desiccant is large. liquid desiccant dehumidification, energy conservation, heat and mass transfer, entransy dissipation, moisture transfer resistance Citation: Chen L, Chen Q, Li Z, et al. Moisture transfer resistance method for liquid desiccant dehumidification analysis and optimization.With social development and living standard progress, air conditioning becomes more and more popular in our daily life. However, it consumes a large amount of energy to create a comfortable habitation. For a traditional vapor compression air conditioner using condensation dehumidification, the evaporation temperature must be lower than the air dew-point temperature in order to dehumidify air, which decreases the refrigeration efficiency. Besides, the air is so cold that it has to be reheated before it is supplied to conditioned area requiring precise temperature control, and reheating will further increase both system complexity and energy consumption. In the interest of releasing the restriction that the evaporation temperature must be lower than the air dew-point temperature, researchers developed the independent temperature and humidity control system [1], where moist air was first dehumidified with desiccant and then cooled. In this way, the evaporation temperature is higher than the air dew-point temperature, leading to the improvement of refrigeration efficiency. Liquid desiccant dehumidification is to dehumidify moist air by using such solutions as lithium bromide (LiBr) and/or lithium chloride (LiCl) which have lower vapor pressure than that of moist air [2][3][4][5]. In this dehumidification process, there are simultaneously heat and mass transfer between moist air and liquid desiccant, where the heat transfer potential is ...

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Proposed energy-efficient air-conditioning system using liquid desiccant

Cited by 104 publications

References 8 publications

Computer Simulation of Heat and Mass Transfer in a Cross Flow Parallel-Plate Liquid Desiccant-Air Dehumidifier

Computer Simulation of Heat and Mass Transfer in a Cross Flow Parallel-Plate Liquid Desiccant-Air Dehumidifier

Use of desiccant dehumidification to improve energy utilization in air-conditioning systems in Beirut

Moisture transfer resistance method for liquid desiccant dehumidification analysis and optimization

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