International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 04 | Apr -2017
p-ISSN: 2395-0072
www.irjet.net
REVIEW ON STEAM CONDENSATION HEAT TRANSFER COEFFICIENT IN VERTICAL MINI DIAMETER TUBE Rahul D. Mathurkar1, Dr. S. M. Lawankar2 P.G. Student, Department of Mechanical Engineering Govt Engineering College, Amravati, Maharashtra, India Assit. Professor, Department of Mechanical Engineering Govt Engineering College, Amravati, Maharashtra, India ---------------------------------------------------------------------***--------------------------------------------------------------------1
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Abstract - Design of tubular heat exchanger is commonly
part of technology system. The most efficient tubular heat exchanger use latent heat of fluid as is phase change from gas to liquid. Thermal design of tubular heat exchanger based on condensation requires knowledge of phase change process in the tubes. This paper focused on review of condensation of steam inside the vertical tube. Condensation experiment are conducted on water steam as a heating medium flow inside tube and water as a base fluid from in shell side by varying saturation temperature and mass flow of water steam and cooling water. Different theoretical or experimental correlation are present for calculating condensation heat transfer coefficient. All this correlation attributes the different condensation heat transfer coefficient. Nusselt gives less condensation heat transfer coefficient than other correlation. Nusselt not studied wave of water steam on condensate surface. Flow of water steam in tubes side form waves on condensate surface and wave effect increase condensation heat transfer coefficient. Key Words: Condensation, vertical tube, water steam, heat exchanger, condensation heat transfer coefficient, wave effect. 1. INTRODUCTION: Condensers are used in a range of chemical, petroleum, processing and power facilities for distillation, for refrigeration and for power generation. Most condensers used in the chemical process industries are water-cooled shell-and-tube exchangers and air-cooled tube or platen exchangers. Shell-and-tube condensers, which are used for condensing process vapors, are classified according to orientation (horizontal and vertical) and according to the placement of the condensing vapor (shell-side and tubeside). This project deals with vertical shell-and-tube condensers with tube-side condensation. Calculations of the overall heat transfer coefficient necessary for the design of the condenser heat transfer area are well described in the literature, but for limited operating conditions only. The Nusselt’s condensation model, which is often recommended for calculating the condensing side heat transfer coefficient, is derived for conditions which need not be satisfied in real operation. The Grober’s method is commonly used for calculating the shell-side heat transfer coefficient. Many industrial systems use vertical tube condensers and industrial practice has © 2017, IRJET
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indicated that, often, much higher condensation coefficients of heat transfer are obtained when vapors are condensed inside tubes rather than outside. Condensation heat transfer plays an important role in many engineering applications, electric power generation, refrigeration and air-conditioning, process industries. Many different physical phenomena are involved in the condensation process, their related importance depending on the circumstances and application.
1.1 Types of condensation: Condensation occurs when the vapour temperature is reduced below its saturation temperature Tsat. This is usually done by bringing the vapor into contact with a solid surface whose temperature Ts is below the saturation temperature Tsat of the vapor. Two distinct forms of condensation are observed: film condensation and drop condensation. 1.1.1 In film condensation: In film condensation, the condensate wets the surface and forms a liquid film on the surface that slides down under the influence of gravity. The liquid film thickness increases in the flow direction as more vapor condenses on the film. This is how condensation normally occurs. 1.1.2 In drop condensation: In drop condensation, the condensed vapor forms droplets on the surface instead of a film, and the surface is covered by countless droplets of varying diameters. In film condensation, the surface is blanketed by a liquid film of increasing thickness, and this “liquid wall” between solid surface and the vapor serves as a resistance to heat transfer. The heat of vaporization hfg released as the vapor condenses must pass through this resistance before it can reach the solid surface and be transferred to the medium on the other side. In drop condensation, however, the droplets slide down when they reach a certain size, clearing the surface and uncover it to vapor. There is no liquid film in this case to resist heat transfer. As a result, heat transfer rates that are more than 10 times larger than those associated with film condensation can be achieved with drop condensation. Therefore, drop-wise condensation is the preferred mode of condensation in heat transfer applications, and people have long tried to achieve sustained drop-wise condensation by using various vapor additives and surface coatings. These attempts have not been very successful, however, since
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