A Liquid Desiccant Enhanced Two Stage Evaporative Cooling System—Development and Performance Evaluation of a Test Rig

M Rafique,Shafiqur Rehman,Muhammad Ali Shakir,Luai Alhems

doi:10.3390/en11010072

M Rafique, Shafiqur Rehman + Show 2 more

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https://doi.org/10.3390/en11010072

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Abstract

Desiccant technology is found to be a good alternative to conventional cooling systems. It can provide better thermal comfort under hot and humid climatic conditions. The major component of a liquid desiccant cooling system is the desiccant dehumidifier which controls the latent cooling load. In this paper, a newly developed liquid desiccant enhanced evaporative cooling system has been tested experimentally. The effects of ambient conditions and other parameters on the performance of the system are investigated. The system performance curves which help to determine the air outlet conditions and coefficient of performance (COP) of the system are drawn for a wide range of ambient air humidity ratios (0.010–0.026 kg/kg), ambient air temperature (25–40 °C), process air flow rate (1.5–8.0 kg/m2·s), regeneration air flow rate (1.5–4.5 kg/m2·s), and regeneration temperature (55–85 °C). The results showed that better supply air conditions are achieved for hot and humid climatic conditions with effectiveness of the system largely dependent on process and regeneration air flow rates, regeneration temperature, and humidity ratio of process air. The dehumidification performance is increased by 62% for a change of ambient air humidity ratio from 0.01 to 0.025 kg/kg. The thermal coefficient of performance improved by 50% for the above variation in humidity ratio. This shows that such thermally activated systems are feasible options for hot and humid climatic conditions as indicated by better performance under these conditions.

Highlights

Statistics prove that the performance of an individual human being is more effective in a conditioned space compared to that in an untreated environment, as a result of which the thermal comfort requirement becomes essential because people spend most of the time in confined environments
The electrical, thermal, and overall performance increased with the increase in inlet air humidity ratio
The mass transfer potential enhanced with increased humidity ratio of ambient air which in turn improved the capacity and performance of the system

Summary

Introduction

Statistics prove that the performance of an individual human being is more effective in a conditioned space compared to that in an untreated environment, as a result of which the thermal comfort requirement becomes essential because people spend most of the time in confined environments. Human comfort conditions are achieved when temperature and moisture are held within a certain narrow range. The acceptable ranges of temperature and relative humidity for human comfort as given by the ASHRAE standards 55 are 20–26 ◦ C and 30–60%, respectively. This increases the demand of air conditioning, both in the residential and commercial sectors. The use of conventional cooling system consumes large amount of energy to fulfill thermal comfort conditions. This technology is not energy efficient for climatic conditions where latent loads are dominant [1]

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