The objective of the study is to investigate the performance improvement in a split air conditioning system using evaporative cooling pads at ODU (outdoor unit) and to determine optimum thickness and material of the cooling pad. For this purpose experiments were conducted on 0.8 TR capacity split air conditioner charged with refrigerant R-22. For comparison experiments were performed with and without evaporative cooling pad. The effect of the different cooling pad material and thickness on the overall performance of split air conditioner is experimentally found by measuring cooling capacity and the power consumption of the system including water circulation pump. From the experimental work it is found that the cellulose cooling pad gives the best results among the selected materials. Split air conditioner coupled with cellulose cooling pad of 100 mm thickness at ODU results in to 13.8% increase in overall COP, 9.5 % reduction in power consumption and 5.1 % increase in cooling capacity at 35°C DBT and 32% relative humidity outdoor air condition.

Split Air Conditioners (ACs) are more commonly use now a days in residential and commercial buildings for achieving thermal comfort in all seasons. Split ACs works on well-known VCR (Vapour Compression Refrigeration) cycle. Split ACs used more in summer season and due to high outside temperature condenser pressure in a VCR cycle and ultimately result in to high electricity consumption. One of the way to reduce energy consumption of Split ACs and increase cooling capacity is reduce air temperature entering to the condenser in ODU using evaporative cooling principle. In this paper detailed review have been carried out for the improvement of split air conditioner performance and experimental study conducted on Split AC (0.8 TR cooling capacity) with and without evaporative cooling pad at ODU. Evaporative cooling pad material and thickness have been varied to analyse their effects on cooling capacity and coefficient of performance (COP) of Split AC. Out of the PVC, Grass and Cellulose cooling pad of same thickness 150 mm, cellulose cooling pad at ODU of Split AC results about 2 bar reduction in condenser pressure and 1.5 KWH energy saving for 10 hours of operation in a day. Split AC with 100 mm thick cooling pad of cellulose material at ODU results in to approximately 16% increase in overall COP, 10.8 % increase in cooling capacity and 4.6 % reduction in power consumption and at 32°C DBT and about 35% RH outdoor weather condition.

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The nucleate pool boiling heat transfer over micro-finned cylindrical surfaces has application in the heat exchangers used in thermal power plants and chemical industries. The estimation of boiling heat transfer coefficient is an important parameter in the design of two-phase heat exchangers using micro-finned cylindrical surfaces. In the present work, related experimental investigations on four micro-finned cylindrical surfaces with different surface geometry using refrigerant R-141b at atmospheric pressure are conducted to determine the boiling heat transfer coefficient over micro-finned cylindrical surfaces. A correlation is developed by dimensional analysis wherein the effects of geometrical parameters, operating pressure and thermo-physical properties of fluids are taken into consideration and dimensional analysis conducted using Buckingham π-theorem. The correlation developed utilizes experimental data obtained over the present study as well as from previous studies by various researchers including experimental data for water over different micro-finned cylindrical surfaces at 1 bar by Mehta and Kandlikar, experimental data for R123 at 0.97 bar by Saidi et al. and experimental data for R134a over micro-finned cylindrical surface at 6.1 bar, 8.1 bar, 10.1 bar and 12.2 bar by Rocha et al. The heat flux ranging from 5 to 1100 kW/m2 are considered for the analysis. The data points have been compared with the proposed correlation and the absolute average deviation of the whole data set was obtained as 13.43% with root mean square deviation of 0.0273. All the predicted values were within ±15% of the experimental values of the boiling heat transfer coefficient.