Chemical Industry & Chemical Engineering Quarterly Available on line at Association of the Chemical Engineers of Serbia AChE www.ache.org.rs/CICEQ Chem. Ind. Chem. Eng. Q. 24 (1) 43-50 (2018) CI&CEQ 43 MUHAMMAD IMRAN AHMAD 1 MANSOOR UL HASSAN SHAH 1 MUHAMMAD ALAM ZAIB KHAN 2 MUHAMMAD ALI KAMRAN 2 AFZAL AHMAD 1 MUHAMMAD IRFAN 1 ALI AHMED DURRANI 3 1 Department of Chemical Engineering, University of Engineering and Technology, Peshawar, Pakistan 2 Department of Mechanical Engineering, University of Engineering and Technology, Peshawar, Pakistan 3 Petroleum Institute, Abu Dhabi, United Arab Emirates SCIENTIFIC PAPER UDC 633.61:66:66.021.4 CONCENTRATION OF CANE-SUGAR SYRUP IN A PILOT SCALE CLIMBING FILM EVAPORATOR Article Highlights • Effect of feed flow rate and steam pressure on the heat transfer coefficient is inves- tigated • Optimum operating parameters are determined for the concentration of sugar cane juice • Correlation is proposed for predicting the heat transfer coefficient in a climbing film evaporator Abstract A climbing film evaporator is similar to a vertical tube heat exchanger, where a hot fluid, such as steam is introduced in shell side and a cold fluid such as sugar syrup is fed in tube side. In this work, variation of the overall heat transfer coefficient due to changes in process variables was investigated experimentally for concentration of cane-sugar syrup in a pilot scale climbing film evaporator. A full two-level factorial experiment was performed and significant factors were determined using Analysis of Variance. The factors investigated in this work were feed flow rate, re-circulation ratio, steam pressure, and feed temperature. The selected process response was the overall heat transfer coefficient for the climbing film evaporator. Feed flow rate and steam pressure were found to have a significant influence on the overall heat transfer coefficient. Keywords: climbing film evaporator; statistical experimental design; heat transfer coefficient; factorial experiment. A climbing film evaporator is a plate heat exchanger or a tubular heat exchanger consisting of tubes inside a shell, and a vapour-liquid separator at the top [1]. Steam usually flows in shell side, whereas liquid flows inside the tubes. The feed enters the bottom of the tube and starts moving upward. At the entry point, the flow is highly turbulent and film begins to form on the surface of the tube wall accelerating heat transfer rate. Climbing film evaporators are widely employed in various chemical industries to obtain a concentrated product from a dilute aqueous solution [1]. In climbing film evaporators, a high heat transfer coefficient (W/(m 2 K)) may be obtained, res- Correspondence: M.I. Ahmad, Department of Chemical Eng- ineering, University of Engineering and Technology, 25000, Peshawar, Pakistan. E-mail: imran.ahmad@uetpeshawar.edu.pk Paper received: 13 June, 2016 Paper revised: 19 December, 2016 Paper accepted: 5 May, 2017 https://doi.org/10.2298/CICEQ160613017A ulting in a relatively small heat transfer area require- ment with low initial capital investment. Climbing film evaporators are employed in var- ious chemical industries such as fertilizer, pulp and paper, textile industries and wastewater treatment plants. Multistage evaporators have been employed in sugar industries since the first commercial imple- mentation in 1844 in the USA [2]. In sugar industries, multiple effect climbing film evaporators are emp- loyed, where the operating temperature and pressure are higher in the first effect and lowest in the last effect [3]. Pakistan, with more than 70 sugar mills, produced 5.139 million t of cane-sugar in 2014-15 [4]. An overwhelming majority of sugar mills in Pakistan employ climbing film evaporators with shell-and-tube configuration with multiple effects for concentration of cane-sugar syrup. Performance of climbing/falling film evaporators Climbing/falling film evaporators have been stu- died previously by various researchers and perform-