International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 03 Issue: 09 | Sep -2016 www.irjet.net p-ISSN: 2395-0072 © 2016, IRJET | Impact Factor value: 4.45 | ISO 9001:2008 Certified Journal | Page 805 EFFECT OF HEAT FLUX AND PRESSURE ON HEAT TRANSFER COEFFCIENT DURING THE BOILING OF DISTILLED WATER AND BENZENE Tarun Kumar 1 , Dr. C. H. Tyagi 2 , Varun Tyagi 3 1 Assistant Professor, Department of Mechanical Engineering, IIMT Engineering College, Meerut, UP, INDIA 2 Professor & Head, Department of Mechanical Engineering, Subharti University, Meerut, UP, INDIA 3 Assistant Professor, Department of Mechanical Engineering, Subharti University, Meerut, UP, INDIA ---------------------------------------------------------------------***-------------------------------------------------------------------- ABSTRACT: This investigation presents experimental work on the studies of nucleate pool boiling of distilled water and benzene at atmospheric and sub atmospheric pressure. The experimental investigation is carried out on heat transfer studies from a submerged horizontal stainless steel cylinder under the condition of constant heat flux to the pool of distilled water and benzene. The heating surface consisted of a horizontal SS cylinder of 70 mm diameter, 4 mm thickness and the length of 244 mm was taken. The surface temperature of the cylinder was measured at three different positions by means of copper constantan thermocouple. They were placed in three axial holes in the thickness of the heating cylinder. These were at its top-, side- and bottom- positions. The liquid temperatures were also measured at the corresponding positions in the bulk of the liquid. The experimental data were conducted to account for the effect of heat flux and pressure on heat transfer coefficient. The pressure was varied from 35.36 to 100.07 kN/m 2 and the heat flux was varied from 13027.99 to 33740.46 watt/m 2 . The heating surface exhibited distinct thermal response to the changes in heat flux. For all the data conducted with distilled water and benzene, the heating surface showed a distribution of boiling heat transfer coefficient around its circumference. The coefficient decreases from top- to side- to bottom- positions distinctly. The average value of heat transfer coefficient for the boiling of benzene has functional relationship with heat flux. The data analysis shows that the seven-tenth power law relating heat transfer coefficient is valid for the boiling of distilled water and benzene at atmospheric and sub atmospheric pressures. The effect of pressure for the sub atmospheric pressure range, it is found that the heat transfer coefficient increases with pressure raised to the power 0.32. Actually, the heating surface characteristics and the physico- thermal properties of boiling fluids have marked influence on heat transfer coefficient for sub atmospheric as well as for the data at atmospheric pressure also. 1. INTRODUCTION Free convection and nucleate pool boiling from horizontal surface are of wide occurrence in process industries, refrigeration industries and in many other industries. Because of their industrial applications, a considerable research has been done by the scientists to investigate the various aspects which may give an insight into the fundamental principles involved. All such studies have been carried out extensively both theoretically as well as experimentally by employing heating surfaces of different materials, shapes and sizes. There are so many parameters which affects the heat transfer coefficient during the pool boiling of liquids. In the present investigation we have conducted the experiments on the boiling of distilled water and the benzene. The effect of the various parameters like heat flux, pressure, surface characteristics etc. has also been studied. The present investigations have been carried out with the following objectives. I. To obtain the experimental data representing the circumferential temperature distribution of a horizontal cylindrical surface and of the liquid surround it. II. To conduct the experiments on the boiling fluids like distilled water and benzene at their saturation temperature over a range of low heat flux and atmospheric and sub atmospheric pressures. III. To account for the parametric effects of operating variable like heat flux, system pressure and heating surface characteristics on boiling heat transfer coefficient and to recommend a generalised correlation.