Krishnadash S. Kshetrimayum

Simulation Study of Heat Transfer Enhancement due to Wall Boiling Condition in a Microchannel Reactor Block for Fischer-Tropsch Synthesis

Abstract A microchannel reactor block, with process and coolant channel planes arranged in alternate fashion and cross flow mode was considered for Fischer-Tropsch(FT) synthesis. Computational Fluid Dynamic (CFD) simulation of heat transfer in the microchannel block was carried out to gain insights on the complex thermal behavior. Cooling oil, subcooled water and saturated water were chosen as coolants to simulate the heat transfer phenomena.The study revealed significant enhancement in heat transfer across the channel walls due to wall boiling condition which occures in case of saturated water as coolant. Consequently, near isothermal condition was able to achieve by adjusting saturated water flow rate. Scenario for partial boiling, with saturated water as coolant, was investigated. Simulations were carried out to study effects of different conditions of heat generation and coolant flow rate on reactor performance parameters.

A sustainable design and simulation of waste sulfuric acid concentration process for semiconductor industry

Abstract In this work, a sustainable design for waste sulfuric acid concentration process that meets a set of constraints and easily integrable to the existing semiconductor fabrication system was pursued. The constraints are related to the stringent environmental, economical and process safety conditions. A set of candidate design was analyzed and the evaporation under vacuum was found to be a sustainable design model. The design model (based on symmetric electrolyte NRTL model 1 for thermodynamics property predictions) developed using ASPEN, identified the optimum operating temperature, pressure for the desired product purity and product rate specifications. The results from our steady state simulations were compared with the data from existing literature, and they showed good agreement. Further, the process compactness and its sensitivity to the process variables demand a strict start-up procedure and control of the operating variables. To address this, a dynamic simulation was carried out by developing a dynamic model using ASPEN Dynamics. Initial settling and set-point change behaviour were studied to get a better understanding of the process dynamics.