Vapour compression refrigeration is used in almost 80 % of the refrigeration industries in the world for refrigeration, heating, ventilating and air conditioning. The high-grade energy consumption of these devices is very high and the working substance creates environmental problems due to environmental unfriendly refrigerants such as chloroflurocarbons, hydrochloroflurocarbons and hydroflurocarbons. Heating, ventilating, air conditioning and refrigeration industries are searching for ways to increase performance, durability of equipments and energy efficiency in a sustainable way while reducing the cost of manufacturing. With the present refrigerants, environmental problems such as ozone layer depletion, global warming potential, green house gases and carbon emission are increasing day by day. In this paper, the popular refrigerant is thoroughly studied experimentally and recommendations are given for alternatives such as carbon dioxide, ammonia and hydrocarbons and new artificially created fluid, HydroFluoro-Olefin 1234yf by DuPont and Honeywell which exhibit good thermo-physical and environmental properties and will be commercialized in the near future.

The air-lift pump is a well-established method for vertical transport of liquids and solid-liquid mixtures. The objectives of the present study are to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters for the use of the pump for two-phase mixtures of air and water when a compressor is readily available. This paper is focused on the general mathematical functions applicable to air-lift pump installations. The effect of various design parameters on the performance of air-lift pump is presented. A user-friendly computer program is developed on the basis of the optimization of influencing variables. This program will be useful for the design and installation of an air-lift pump handling air-water mixtures. A comparative study of an air-lift pump with a centrifugal pump handling two-phase mixtures is also discussed in the paper.

Airlift pumps are finding increasing use where pump reliability and low maintenance are required, where corrosive, abrasive, or radioactive fluids must be handled and when a compressor is readily available. The objective of the present study is to evaluate the performance of a pump under predetermined operating conditions and to optimize the related parameters The effects of design parameters viz. mass flow rate of air, immersion ratio, diameter of rising main etc. on the performance of airlift pump are presented. The larger diameter of rising main is found to be suitable for high flow rate of water. The injecting device used in the system has considerable effect on the performance of the pump. The paper is focused on the general mathematical expression to determine the effective diameter of nozzle applicable to air lift pump installations in the diameter range of 25.4 mm ≤ d ≤101.6 mm.The various types of flows are visualized in the rising main of a pump and the corresponding airlift pump performance is analyzed. It is observed that the slug flow is more predominant for improving the performance of the pump.

The performance of Scheffler reflector has been studied. In this system storage reservoir was installed at Focus point. It has a single large diameter drum which serves the dual purpose of absorber tube and storage tank. The drum is sized to have a storage capacity of 20 liter for experiment. The tests were carried out with this set up and were repeated for several days. Performance analysis of the collector has revealed that the average power and efficiency in terms of water boiling test to be 1.30 kilowatts and 21.61 % respectively against an average value of beam radiations of 742[Wm-2]. The maximum water temperature in the storage tank of 98°C has been achieved on a clear day operation and ambient temperature between 28°C to 31°C

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Gray Cast Iron Casting (GCIC) materials are widely used particularly in automotive industries. However, the high cost of processing these materials limits the use of their improved mechanical properties. Tool life is one of the most important factors in machining operations of such materials and it is mainly affected by cutting conditions including the cutting speed, depth of cut, insert material and cooling environment along with length and diameter of the tool body. In addition, the modern industry is moving towards automating the manufacturing processes. Therefore, tool life monitoring is important to achieve an efficient manufacturing process. In this study, a tool wear prediction model during the boring machining operation of gray cast iron is studied. It is based on the monitoring of tool performance in controlled machining tests with measurements of tool life, surface finish, bore size variation, cutting time and load on spindle in terms of % current under different combinations of cutting parameters (cutting speed, depth of cut, tool nose radius, length & diameter of tool, tool material and coolant pressure & concentration). The influence of cutting parameters on the tool life was studied experimentally by performing more than 120 cutting tests. A prediction model was then developed to predict tool wear. The basic steps used in generating the model adopted in the development of the prediction model are: collection of data; analysis, pre-processing and feature extraction of the data, design of the prediction model, training of the model and finally testing the model to validate the results and its ability to predict tool wear. The evolution of boring machining operation properties using different parameters is a complex phenomenon. There are many factors (like cutting speed, depth of cut, insert material and cooling environment along with length and diameter of the tool bodyaffecting the performance of cast iron boring machining operation resulting to poor tool life. This paper presents an experimental investigations and Sequential classical experimentation technique has been used to perform experiments for various independent parameters. An attempt of mini-max principle has been made to optimize the range bound process parameters for minimizing cutting time and surface finish during cast iron boring machining operation. The test results proved that cutting time and surface finish were significantly influenced by changing important four dimensionless π terms. The process parameters grouped in π terms were suggested the effective guidelines to the manufacturer for improving tool life by changing any one or all from theavailable process parameters.

Microchannel condensers are widely used in automobile and household air conditioners with R134a as a refrigerant. In order to reduce the global warming potential as well as the refrigerant charge, hydrocarbon mixture of R290 and R600a (50:50 % by mass) was used as a drop in substitute to R134a in the vapour compression refrigeration system. Versatile vapour compression refrigeration system of 1 ton of refrigeration capacity was designed, developed and fabricated for testing different refrigerants. Various parameters such as ambient temperature in the condenser cabin, different condensation and evaporation temperatures, different mass flow rates of refrigerant and air can be controlled precisely in the test rig. Experiments were performed using R134a and hydrocarbon mixture of R290 and R600a (50:50 % by mass) for condensation temperature of 44°C and evaporation temperature ranging from -15 to 15 °C. Refrigerant charge was reduced by 45 % with the hydrocarbon mixture of R290 and R600a (50:50 % by mass) over R134a. Performance parameters such as compressor power consumption increases by 13.3 %, coefficient of performance reduced by 43 %, refrigeration capacity increased by 140.8 %, condenser capacity increased by 185.4 % and the product of overall heat transfer coefficient and surface area of condenser was increased by 243.7 % by using hydrocarbon mixture of R290 and R600a (50:50 % by mass) over R134a with the microchannel condenser at condensation temperature of 44°C and evaporation temperature of 0°C. It is suggested to use an environmental friendly refrigerant, hydrocarbon mixture of R290 and R600a (50:50 % by mass) as a drop in substitute to the conventional refrigerant R134a in the automobile, household air conditioning and refrigeration systems.

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