Abstract: In the Ammonia Recovery process of the nickel company the pressure drop of the Ammonia liquor cooling process, by means of the plate heat exchangers, is associated to the incorrect estimate of the overall heat transfer coefficients and fluid parameters: Water and ammonia liquor outlet temperature, Water and ammonia liquor mass flow. The above increases the consumption of water, the available energy in the system and the maintenance costs. The investigation was carried out in plate heat exchangers, with the objective of determining the overall heat transfer coefficients and the behavior of pressure drop and power required for the ammonia liquor cooling process. By means of an iterative procedure was determined the equation and behavior of the overall heat transfer coefficients and their dependence with the Reynolds and Prandtl, for it was used a multifactor experimental design and measurements of the installation work parameters in function of the time. The results predict the knowledge of the overall heat transfer coefficients for the calculation of the Nusselt number with the Reynolds and Prandtl values for both fluids (water and ammonia liquor). The comparison with other investigators shows correspondence with Thonon results. To the overall heat transfer coefficient values less than 2500 W/m 2 K, the outlet temperature of the ammonia liquor exceeds 40 O C so the maintenance of the installation is recommended in less than 27 days period. The behavior of pressure drop and power demand as a function of the Reynolds number was obtained. Values for cooling the liquor are diminished compared to the water, it is because more water is used. Keywords: Overall heat transfer coefficients, Pressure drop, Plate heat exchanger I. INTRODUCTION The heat exchange processes between two fluids that are to different temperatures and separated by a solid wall take place in many applications in the nickel companies. The device that is used to carry out this process is denominated heat exchanger. The ammonia liquor cooling process takes place with the purpose to obtaining good ammonia and carbon dioxide absorption. E. T. Tamayo is with, Cotopaxi Technical University, Latacunga City, Ecuador Republic (e-mail: enrique.torres@utc.edu.ec ). E. J. Díaz is with Equinoccial Technological University, Santo Domingo de los Tsáchilas City, Ecuador Republic (e-mail: eduardo.diaz@ute.edu.ec). M. P. Cedeño is with Equinoccial Technological University, Santo Domingo de los Tsáchilas City, Ecuador Republic (e-mail: mariapaulina1980@hotmail.com). C. L. Vargas is with, Cotopaxi Technical University, Latacunga City, Ecuador Republic (e-mail: cavafer2@hotmail.com). S. G. Peralta is with Equinoccial Technological University, Santo Domingo de los Tsáchilas City, Ecuador Republic (e-mail: gustavopl1287@yahoo.es) M. A. Falconi is with Equinoccial Technological University, Santo Domingo de los Tsáchilas City, Ecuador Republic (e-mail: itofalconi@hotmail.com) The plate heat exchanger consists of a pack of corrugated metal plates with portholes for the passage of the two fluids between which heat transfer will take place. The plate pack is assembled between a fixed frame plate and a movable pressure plate and compressed by tightening bolts. The plates are fitted with a gasket which seals the inter plate channel and directs the fluids into alternate channels. The number of plates is determined by the flow rate, physical properties of the fluids, pressure drop and temperature program. The plate corrugations promote fluid turbulence and support the plates against differential pressure. The plate heat exchangers are most efficient in comparison with the shell and tube exchangers. They achieve a high efficiency due to the great exchange surface that exists between the two fluids. The contact surface increase due to the circulate of the fluid for very narrow channels, but on the other hand they have an inlays problems and high loss of charge due to the use of ammonia liquor. The investigation was carried out in plate heat exchangers, with the objective of determining the transfer coefficients and the influence of the inlays in the efficiency loss of the installation. To obtain the heat transfer coefficients and thermal efficiency in the heat exchanger is necessary to take in consideration different concepts related to thermodynamic, fluids dynamic and experimental considerations. These coefficients are obtained between two fluids in terms of the total thermal resistance; it includes convection and conduction resistances for plane or cylindrical surfaces [1]- [4]. The heat transfer coefficients obtained for different applications are exposed in the consulted literature [5]-[8]. The authors summarize the experimental techniques used to obtain the coefficients and their dependence on various dimensionless numbers: Nusselt, Reynolds and Prandtl. In all cases the results are applicable to the specific conditions, under which the experiments were conducted, so under different conditions are necessary experiments to determine the applicability of the results. There have been many investigations regarding to evaluate the fouling influence on the heat exchanger efficiency. Suarez [9] established two three-dimensional numerical models, one single and another biphasic. He applied the models to the power plant condenser to assess the influence of the fouling accumulation on heat transfer surfaces. The behavior of the main parameters is analyzed and compared to traditional procedure. Evaluation of fouling in shell and tube heat exchangers without phase change used by Bonals [5] essentially comprises an algorithm or code based on the Bell-Delaware method. From process variables determine homogeneous fouling thicknesses of both currents corresponding to each Enrique T. Tamayo, Eduardo J. Díaz, María P. Cedeño, Carlos L. Vargas, Segundo G. Peralta, and Manuel A. Falconi Overall heat transfer coefficients, pressure drop and power demand in plate heat exchangers during the ammonia liquor cooling process INTERNATIONAL JOURNAL OF MECHANICS Volume 10, 2016 ISSN: 1998-4448 342