Performance assessment of hybrid desiccant cooling system at various climates
In our work, operation of hybrid desiccant cooling system (HDCS) has been investigated based on experimental studies. Different climates have been created by changing the temperature and humidity of HDCS inlet air, using an electrical heater and a centrifuge humidifier. Input energies, temperature of various points, and their relative humidity have been measured at the created climates. Coefficient of performance (COP), thermal coefficient of performance, and electrical coefficient of performance (ECOP) of the HDCS have been calculated. As a reference situation, vapor compression system (VCS) was examined at the same condition as HDCS. Results show that COP of HDCS in comparison with VCS decreased about 36% and 28% in hot-dry and hot-humid climates, respectively, which is due to the thermal energy consumption in HDCS. In contrast its ECOP increased, which means that by using HDCS some electrical energy would be saved. Defining operating cost index (OCI) parameter, operation costs of VCS and HDCS have been compared. Analyzing the OCI results shows that in HDCS, although decreasing the electricity consumption results in more usage of natural gas, these systems are economical especially in those countries with low natural gas prices.
Entropy Generation in Liquid Desiccant Dehumidification System
Abstract In this paper, performance of the liquid desiccant dehumidification system in evaporation coolers was investigated by the Second Law of Thermodynamics analysis. This system was designed and manufactured for this purpose. Lithium chloride (LiCl), as liquid desiccant, and a packed bed column were used for dehumidification. The described system includes a part for processed air simulation in various temperatures and humidities. Entropy generation of the liquid desiccant dehumidifier was analyzed based on the second thermodynamic law. The effect of inlet parameters of the dehumidification column on the entropy generation was also investigated. The results showed that the entropy generation was highly dependent to operational conditions and inlet parameters of the desiccant dehumidification column.
Performance enhancement of some alternatives to R‐502
The results of an experimental study on the behaviour of some new alternatives to R-502 using heated suction accumulator are presented. The experimental set up was composed of a fully instrumented air-source heat pump with a capacity of 12000 BTUH and equipped with a heated suction accumulator. The refrigerant temperatures were varied at the evaporator entrance to simulate various extreme conditions encountered in air-source heat pump applications. The primary parameters observed during the course of this study were mass flux, heat flux, quality evaporator and condenser thermal capacities, power consumed and pressure ratios for the azeotropic refrigerant mixtures under investigation. The test results showed that a heated suction accumulator enhanced the evaporation of more volatile component of ternary azeotropic refrigerant mixtures. Thus, increasing the mixture thermal capacity as well as the COP. Furthermore, experiments have also shown capacity increases of 27 per cent with a heat accumulator over an unheated accumulator at - 15°C outside air temperatures.