Evaluation of membrane-based air pre-dehumidification for a capillary radiant air conditioning system

The polyvinylidene fluoride hollow fibre membrane air dehumidification tests were carried out between the liquid desiccant solutions and the wet air. Three liquid desiccant solutions of LiBr solution (50%), LiCl solution (35%) and CaCl2 solution (40%) were tested under different wet air conditions. The results showed that all the membrane dehumidification processes were stable. The air moisture content in the outlet of the membrane was maintained as 6.5 g/kg (da)–8.2 g/kg (da) when the air moisture content in the inlet of the membrane was operated from 17.1 g/kg (da) to 32.4 g/kg (da). The dehumidification amount of LiBr solution (50%) and LiCl solution (35%) was more productive. On this basis, a membrane-based air pre-dehumidification process for the capillary radiant air conditioning system was built. Since the ideal dew point temperature range of the indoor air is below 14–17°C according to the cold supply water, all the air moisture content at the membrane outlet is much lower than that of the ideal dew point temperature range, which means non-condensing occurs in the capillary tube surface. The membrane-based air pre-dehumidification process can easily form an adaptive regulation process of humidity with the capillary radiant air conditioning system under different environmental parameters.

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Vapour Compression and Liquid Desiccant Hybrid System for Air Conditioning

Volume 1: Advanced Energy Systems, Advanced Materials, Aerospace, Automation and Robotics, Noise Control and Acoustics, and Systems Engineering ◽

10.1115/esda2006-95541 ◽

2006 ◽

Cited By ~ 1

Author(s):

Stefano Bergero ◽

Anna Chiari ◽

Enrico Nannei

Keyword(s):

Air Conditioning ◽

Power Saving ◽

Operating Conditions ◽

Dew Point ◽

Operating Parameters ◽

Direct Expansion ◽

Liquid Desiccant ◽

Hydrophobic Membrane ◽

Air Conditioning System ◽

Vapour Compression

The present study examines the performance of a hybrid air-conditioning system in which a vapour compression inverse cycle is integrated with an air dehumidification system working with hygroscopic solution and hydrophobic membrane. This approach may prove to be a valid alternative to the traditional summertime air-conditioning system, which involves cooling the air to below its dew point and subsequently reheating it. The system examined simultaneously cools and dehumidifies the air in an air-LiCl solution membrane vapour exchanger before it enters the conditioned environment. The LiCl solution is cooled by means of a vapour compression inverse cycle that uses the refrigerant KLEA 407C. The heat rejected by the condenser is used to regenerate the solution. A SIMULINK calculation programme was used to simulate the system in steady-state conditions. The performance of the system was analysed on varying significant operating parameters and was compared with that of a traditional direct-expansion air-conditioning plant. The results of the simulations revealed significant power saving which, in certain operating conditions, was as much as 50%.

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DEW-POINT HYGROMETER FOR USE AT LOW TEMPERATURES

Canadian Journal of Research ◽

10.1139/cjr39d-005 ◽

1939 ◽

Vol 17d (2) ◽

pp. 35-38 ◽

Cited By ~ 1

Author(s):

C. A. Winkler

Keyword(s):

Relative Humidity ◽

Moisture Content ◽

Low Temperatures ◽

Dew Point ◽

Slow Cooling ◽

Point Temperature ◽

Dew Point Temperature

An apparatus is described in which provision for slow cooling of a metal mirror by circulating over it liquid from a vessel in a thermoregulated bath, and the use of multiple thermocouple elements contained in the mirror, enable the dew-point temperature to be gradually approached and accurately determined. Precise measurements of relative humidity at low temperatures, where the moisture content of the air is small, are therefore possible. A precision of ± 0.5% relative humidity was readily attained at temperatures down to − 15 °C.

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Performance analysis and mixing ratio selection of mixed liquid desiccant for a dehumidification system

Indoor and Built Environment ◽

10.1177/1420326x19862009 ◽

2019 ◽

Vol 29 (5) ◽

pp. 711-720 ◽

Cited By ~ 3

Author(s):

Xiaoqiang Jiang ◽

Huaming He ◽

Xingyou Li ◽

Huimin Mao

Keyword(s):

Air Conditioning ◽

Removal Rate ◽

High Energy ◽

Dew Point ◽

Moisture Removal ◽

Mixing Ratio ◽

Liquid Desiccant ◽

Mixed Salt ◽

Dew Point Temperature ◽

Selection Of

Liquid-desiccant dehumidification system in building air-conditioning has high energy efficiency in comparison to traditional dehumidification technology that needs to cool air below the dew point temperature. Since the dehumidification process dominates the performance of a liquid-desiccant system, this study aims to develop a deeper understanding in the dehumidification performance of some liquid desiccants. Then, an experiment test was conducted to determine the CaCl2-LiCl mixed liquid-desiccant system in a dehumidification system. The effects of the pure and mixture liquid desiccant solution on the moisture removal rate, refrigerating capacity and dehumidification performance were compared and analysed. Results show that with the increase in the LiCl concentration, the dehumidification capacity and dehumidification coefficient first increased rapidly and then increased slowly after 30% LiCl concentration. According to the economic analysis of mixed salt solution, the mixed LiCl and CaCl2 solution with a mixing ratio of 3:1 would achieve the best optimal dehumidification efficiency and would incur a low system cost under the working conditions of a dry-bulb temperature at 26°C and a relative humidity of 60% of fresh and return air.

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Extending dew-point temperature scale up to +50 °C

International Journal of Metrology and Quality Engineering ◽

10.1051/ijmqe/2018017 ◽

2018 ◽

Vol 9 ◽

pp. 17

Author(s):

Doaa Mohamed Abd El-Gelil ◽

Mohamed Gamal Ahmed

Keyword(s):

Temperature Scale ◽

Scale Up ◽

Temperature Stability ◽

Dew Point ◽

Point Temperature ◽

Dew Point Temperature ◽

Temperature Range ◽

Saturator Efficiency ◽

Uncertainty Of Measurements ◽

First Time

Extension of dew-point temperature scale has been performed using a two-temperature (2-T), constant pressure humidity generator that is developed for the first time by the National Institute of Standard (NIS) in order to extend the calibration capabilities to the high dew-point temperature range at NIS. It relies on the saturation of a stream of gas flowing over a water surface maintained at constant, well-known, temperature. In this paper, primary realization of dew-point temperature scale in a dew-point temperature range up to +50 °C was performed to extend calibration capabilities and to improve the uncertainties of the dew-point temperature scale realization. Several experiments were carried out in order to characterize the generator. Characterization comprises studies of the saturator efficiency, temperature stability and a comparison with a calibrated chilled-mirror hygrometer. The results of the efficiency tests showed good performance of the generator. For uncertainty of measurements, a thorough analysis was also described representing estimations of contributions for all the sources that possibly affect measurements.

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Indoor Environment Numerical Simulation of All Cold Air Distribution System With Stratified Air Conditioning

ASME 2008 2nd International Conference on Energy Sustainability, Volume 1 ◽

10.1115/es2008-54112 ◽

2008 ◽

Author(s):

Wei Bing ◽

Li Li ◽

Jiang Lu ◽

Zhang Wei

Keyword(s):

Numerical Simulation ◽

Distribution System ◽

Air Conditioning ◽

Distribution Systems ◽

Dew Point ◽

Air Distribution ◽

Large Space ◽

Cold Air ◽

Point Temperature ◽

Dew Point Temperature

At present all cold air distribution systems are being used widely due to their advantages of smaller ductwork, shorter floor-to-floor height and less energy consumption etc. They are mostly used in VAV (Variable Air Volume) systems or with the radiant panel systems in the office and residential buildings at the supply air dew point temperature of 6∼10°C, rarely used in large space buildings. The technology of stratified air conditioning is one of the energy saving technologies to large space buildings, which has been popularly used in the conventional air supply systems with the supply air dew point temperature of 11∼16°C. In this paper, the cold air distribution system and the stratified air conditioning technology in a large space building are combined to study. With the method of CFD, the indoor thermal environment of a large space workshop is simulated. The velocity and the temperature as well as the relative humidity fields under different air flow modes are presented, analyzed and compared. With the help of numerical simulation results, the optimal airflow mode is proposed, which show that the all cold air distribution with the stratified air conditioning is a good option for large space buildings. All these above will be good references to the application of cold air distribution system and the selection of the airflow mode in large space buildings.

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