STUDY OF LIQUID DESICCANT AIR CONDITIONING SYSTEM USING MARQUISE SHAPED CHANNEL SOLAR COLLECTOR

Abstract

The present thesis deals with the study of a liquid desiccant air conditioning system using a Marquise shaped channel Flat-plate solar collector. Initially, there is an investigation for the performance of a Marquise shaped channel Flat-plate solar collector using Al2O3–water nanofluid and pure water as the base fluid. Using nanofluids as heat transfer fluid instead of conventional fluid (like pure water) improves heat transfer and thermal properties and also there is a remarkable effect on the collector efficiency. The experimental setup comprises of developing a marquise shaped channel flat plate collector of the aluminium absorber plate, a closed-loop working fluid system and measurement devices (thermocouples, temperature meter, flow meter and solar Pyranometer). The effect of various parameters like mass flow rate of fluid, collector inlet and outlet fluid temperature, solar radiation, and ambient temperature on the collector efficiency is investigated. The experimental results show that, each of these parameters can affect the collector efficiency differently by changing the value of the other parameters. The optimization of results indicates that under the favourable conditions, in both Al2O3-water nanofluids and pure water cases the efficiency of collector is increased with increasing solar intensity. The enhancement in performance of solar collector when using Al2O3-water nanofluid in comparison to pure water has been studied here. The mass flow rate was varied from 1 to 5 L/min (1, 2, 3, 4 & 5) and the volume fraction is 0.1 vol. % of nanofluid. Experiments were carried out with stable nanofluid. By suspending Al2O3 nanoparticles (particle size 20 nm) in the base fluid (water) the maximum collector efficiency attained is 83.2% and to the pure water is 59.7%, whereas exergy efficiency maximum are achieved 18.7% and 12.3% for the 20nm Al2O3 nanofluid and base water at the mass flow rate of 3 L/min. Hence, our aim for efficient solar flat plate collector is achieved. Finally, there is a study of a liquid desiccant air conditioning using this marquise shaped channel solar flat plate collector. The main problem in the use of liquid desiccant air conditioning is the utilization energy for regeneration, corrosiveness to metals and carryover of the solution to the air. To overcome this problem, there is the development of a dehumidifier using corrosion-resistant materials and regeneration using solar energy rather than fossil fuel. The main components to use liquid desiccant as air conditioning are dehumidifier, evaporative cooler and the regenerator. The dehumidifier is made of stainless steel tubes of type 316L since the solution is corrosive to metal and these tubes are stacked in aluminium fins to maintain the desiccant solution temperature using the evaporative cooler. In this experiment, calcium chloride solution (CaCl2-H2O) is used as a liquid desiccant solution. The marquise shaped channel flat plate collector is used for heating water using closed-loop of thermosiphon as a regeneration of the diluted desiccant solution. The flow rate for air is fixed at 10CFM and the concentration of calcium chloride is 33% by mass. The inlet air is humidified and controlled by a constant temperature bath to maintain the inlet conditions. The inlet parameters considered are solution volume flow rate, inlet temperature, inlet relative humidity, regeneration temperature, and desiccant solution temperature. The performance parameters are the absolute humidity reduction, outlet temperature and dehumidifier and enthalpy effectiveness of the dehumidifier. The solution volume flow rates of 14 L/min, 16 L/min, 18 L/min and 20 L/min are used for the experiments. The experiments show that for a fixed Ta, inlet and RH% as solution volume flow rate increases, there is increase in absolute humidity reduction. The temperature of the dehumidified air is reduced compared to that of inlet air if this air is passed over the pad used for the evaporating cooler. It is seen that the increase in relative humidity from 68.88% to 92.8% for the flow rate of 20 L/min and fixed inlet air temperature, increases absolute humidity reduction from 5.56 to 13.3 g/kg. The increase in solution temperature reduces the absolute humidity reduction and dehumidifier effectiveness. When the solution temperature changes from 31.5 to 34 0C, there are reductions in the absolute humidity reduction and dehumidifier effectiveness by 34.4% and 13.04% respectively.