Analysis and Design of Efficient Absorbers for Low-Temperature Desiccant Air Conditioners

1981 ◽  
Vol 103 (1) ◽  
pp. 67-74 ◽  
Author(s):  
C. S. P. Peng ◽  
J. R. Howell
Keyword(s):  
Mass Transfer ◽  
Low Temperature ◽  
Heat And Mass Transfer ◽  
Mass Transfer Rate ◽  
Falling Film ◽  
Air Conditioners ◽  
Tube Heat Exchanger ◽  
Analysis And Design ◽  
Fin Tube ◽  
Air Conditioning Systems

Desiccant dehumidification and air-conditioning systems require careful design to minimize large parasitic power requirements for pumps and blowers. Each component depends to some extent on overall system characteristics, yet each component must be carefully modeled in itself. The most challenging part of optimizing a system is the absorber design. In order to increase the heat and mass transfer rate while minimizing the pressure loss in the absorber, a direct contact falling film fin-tube heat exchanger is analyzed with water flowing on the tube side and desiccant flowing as a falling film on the fin side. Air is cooled and dehumidified by the water and desiccant as it is circulated through the absorber. A model to analyze the heat and mass transfer in the absorber has been developed. An optimum design has been selected based on not only thermal performance but also practical and economic considerations. Application of the absorber design is then made to design of a complete desiccant system for use with low-temperature heat as an energy source.

Analysis of Heat and Mass Transfer of an Adiabatic Cross-Flow Liquid Desiccant Absorber Operating at Low Temperatures

2009 ◽  
Author(s):  
Sergio M. Pineda ◽  
Gerardo Diaz
Keyword(s):  
Mass Transfer ◽  
Low Temperature ◽  
Heat And Mass Transfer ◽  
Cross Flow ◽  
Ambient Air ◽  
Liquid Desiccant ◽  
Cooling Fluid ◽  
Air Temperatures ◽  
Increasing Demand ◽  
Air Conditioning Systems

With the rising costs of electricity due to increasing demand of electric power, liquid desiccant systems have received significant attention as a way to reduce latent loads on air conditioning systems. In particular, the performance of liquid desiccant systems in humid climates has shown significant reductions in energy consumption. In general, these liquid desiccant systems are composed by an absorber or dehumidifier and a regenerator that utilizes a heat source to reject the water from the diluted liquid desiccant. As the humidity of the air is absorbed at the dehumidifier, the temperature of the liquid desiccant increases due to the addition of heat from the enthalpy of condensation of the water vapor. Thus, many designs of liquid desiccant absorbers include the flow of a cooling fluid that removes heat from the liquid desiccant. A novel application of liquid desiccant systems corresponds to the localized removal of moisture from the air inside low temperature rooms that contain relatively high levels of humidity such as refrigerated warehouses for the food industry. The purpose is to reduce the formation of ice at the surface of the evaporator. Due to the low temperature of the air inside these rooms, no cooling fluid is necessary for the removal of heat from the liquid desiccant. Thus, the designs of the absorbers differ from the designs used for ambient air temperatures. In this paper, a mathematical model of the heat and mass transfer for an adiabatic parallel-plate absorber for which a thin film of liquid desiccant flows down its walls and dehumidifies the air in cross-flow configuration is developed.

COMPARISON OF HEAT AND MASS TRANSFER IN FALLING FILM AND BUBBLE ABSORBERS OF AMMONIA-WATER

2002 ◽  
Vol 15 (3) ◽  
pp. 191-205 ◽  
Author(s):  
Ki Bong Lee ◽  
Byung Hee Chun ◽  
Jae Cheol Lee ◽  
Jae Chun Hyun ◽  
Sung Hyun Kim
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Falling Film ◽  
Ammonia Water

Effect of Nanoparticles on H2O/LiBr Falling Film Absorption Process

2016 ◽  
Author(s):  
L. Y. Zhang ◽  
Y. Li ◽  
Y. Wang ◽  
L. X. Cao ◽  
X. Z. Meng
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Fe3o4 Nanoparticles ◽  
Falling Film ◽  
Absorption Process ◽  
Nanoparticle Concentration ◽  
Water Vapor Absorption ◽  
Libr Solution ◽  
Falling Film Absorption ◽  
Film Absorption

Absorber is an important component in absorption refrigerating system. Its performance plays a significant role on the overall efficiency of absorption refrigerating system. The nanofluids which can enhance the heat and mass transfer will be utilized to absorber for enhancing the water vapor absorption process and improving the absorber efficiency. The software CFD-FLUENT is used to analyze the falling film absorption process of the nanofluids, which consists of H2O/LiBr solution with Fe3O4 nanoparticles in this paper. The results indicate that the enhancing heat and mass transfer of nanofluids is related to the nanoparticle concentration and size. The stronger the nanoparticle concentration, the greater enhancement of heat and mass transfer of falling film; while the smaller the nanoparticle size, the greater enhancement of heat and mass transfer of falling film. It is also found that the enhancement ratio of heat and mass transfer flux reach 1.48 and 1.37, respectively, as the Fe3O4 nanoparticles mass concentration of 0.01wt% and the size of 50nm.

scholarly journals Modeling of conjugated heat and mass transfer in the entrance region of falling liquid film at various values of the Froude number

2018 ◽  
Vol 194 ◽  
pp. 01007
Author(s):  
Maria V. Bartashevich
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Liquid Film ◽  
Froude Number ◽  
Heat And Mass Transfer ◽  
Water Solution ◽  
Lithium Bromide ◽  
Entrance Region ◽  
Falling Film ◽  
Falling Liquid Film

Mathematical model of conjugated heat and mass transfer in absorption on the entrance region of the semi-infinite liquid film of lithium bromide water solution is investigated for different values of Froude number. The calculations shown that larger values of Froude number corresponds to a smaller thickness of the falling film. It was demonstrated that for large values of the Froude number the heat transfer from the surface is greater than for smaller values.

scholarly journals Analysis of heat and mass transfer mechanism during thermal energy storage and temperature regulation

2020 ◽  
Vol 24 (5 Part B) ◽  
pp. 3185-3193
Author(s):  
Sina Dang ◽  
Hongjun Xue ◽  
Xiaoyan Zhang ◽  
Chengwen Zhong
Keyword(s):  
Mass Transfer ◽  
Energy Storage ◽  
Low Temperature ◽  
Phase Change ◽  
Heat And Mass Transfer ◽  
Latent Heat ◽  
Temperature Regulation ◽  
Phase Change Materials ◽  
Heat Energy ◽  
Temperature Environment

To strengthen the heat and mass transfer capacity and improve the temperature regulation rate, potential storage is taken as the research object in this research to study the heat energy storage of the battery in the low temperature environment. Lattice Boltzmann method is adopted to study the heat energy storage influence mechanism of the temperature regulation system of the low temperature phase-change materials. In addition, the influence of different physical parameters (thermal conductivity and latent heat of phase change) on the thermal insulation of the system in the process of temperature control is revealed. The results show that the mechanism of heat and mass transfer in the process of heat storage and temperature control is related to the different physical properties of phase change materials. The decrease of thermal conductivity and the increase of latent heat of phase change materials will greatly increase the effect of heat energy storage. Therefore, under the action of phase change latent heat, phase change material can effectively extend the holding time of the battery in the low temperature environment.

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