ENERGY CONSERVATION BY ENHANCEMENT IN HEAT TRANSFER IN POOL BOILING PROCESSES A. R. Acharya, Sameer Gajghate and A.T.Pise ( aracharya@rediffmail.com and ashokpise@yahoo.com ) Department of Mechanical Engineering, Govt. College of Engineering, Karad 415124, India Phone: 02164 272414, Fax: 02164271713, e-mail: aracharya@rediffmail.com Abstract For researchers, it is a challenge to carry processes which will consume less energy, using some efficient and effective techniques. Pool boiling process is used in various industries and in day to day life. It is need to augment the heat transfer rate in pool boiling applications for saving the energy required to complete the process as well as time required to boil if reduced can have good impact on productivity of the process. There are different techniques used for the enhancement in heat transfer process in pool boiling. These are categorized as active, passive and compound techniques. An extensive survey of these techniques is carried in view to optimize the energy required for pool boiling processes. These techniques accelerate the bubble dynamics (i.e. bubble formation, its growth, mixing and departure) that optimize the energy required for processes. The addition of small amount additive in the solution is one of the cost effective technique and simple to handle. Environment friendly additives like NH 4 Cl and Betel nut were tested in search of to optimize their quantity to be added in water. Bubble dynamics and their behavior were observed in view to minimize the conservation of energy. Presence of additives in water shifts the boiling curves to the minimum energy requirements. The main motive of this paper is to reduce the energy required for the pool boiling processes and to understand the mechanism of pool boiling. Keywords: Pool boiling, Additive, Bubble, Enhancement techniques 1. Introduction Boiling is a liquid to vapor phase change, occurring at the solid liquid interface, when a liquid is brought into contact with a surface maintained at a temperature T w . It is sufficiently above the saturation temperature T sat of the liquid. Pool boiling is boiling of stationary fluids. In pool boiling the fluid is not forced to flow by a mover such as pump and any motion of the fluid is due to natural convection currents and motion of the bubbles under the influence of buoyancy force. Pool boiling processes are used in various industries and day to day life. There is a general need to increase the heat transfer rate in pool boiling applications for saving the energy required to phase change. Energy requirements are becoming stringent day by day due to the depleting energy sources and growing concern for the environment. To cope up with the need, a huge effort has already been made in the investigation of boiling heat transfer. The research in boiling heat transfer can be broadly classified into experimentation, mechanistic modelling and computational simulation [1]. Research work in this direction conducted experimentally by the authors in the department of Mechanical Engineering, Govt. College of Engineering, Karad are briefed below.Now lots of efforts are takes place to save the energy from different applications because of energy crisis and global warming. Hence the main motive is to reduce the energy i.e. increase the heat transfer for pool boiling. Many researchers found enhancement techniques in heat transfer for the boiling are discussed in this paper. The addition of surfactant as additive is the cost effective technique and simple to handle. The paper is based on pool boiling experiments for pure water and water with varying concentrations of different surfactants namely ammonium chloride and Betel Nut. These surfactants are added in the wide range in the pure water i.e. below and above the solubility limit in search of to find optimum quantity of surfactants for enhancement of heat transfer. The reading for the pure water is taken as a baseline data. Boiling curves for heat transfer coefficient are plotted for with and without surfactants in the pure water . The effects of properties of different surfactants mainly the surface tension, density and viscosity on heat transfer mechanism have been studied. The pool boiling techniques are used in various industries like processing, thermal, refrigeration and air conditioning, production etc. The interest in enhanced heat transfer is closely tied to energy prices. In the 1980s and