No abstract

Despite the wide applications of multi-effect vapor absorption systems, their energy requirement is relatively higher. Also, their exergy analyses found in the literature reveal that the exergy destruction rate at the absorber is quite significant and has the potential for improvement in its energy efficiency. In this work, the exergy destruction rate at the absorber is minimized using the penalty factor method against the optimized generator temperature of the double-effect vapor absorption system by considering absorber, evaporator, and condenser temperatures into consideration. Modeling of the double-effect vapor absorption system was performed using a thermodynamic toolbox in SIMULINK. The present model employed a refrigerant heat exchanger to enhance the system cooling capacity. The Liquid-vapor ejector valve at the absorber also improved the mixing of the solution and refrigerant vapor resulting in lower irreversibility of the system. Results show that the coefficient of a performance increase by 2.4 % with refrigerant heat exchanger and exergy loss at absorber decrease by 9.4 % with ejector. The optimum performance was seen at the condenser and evaporator temperatures of 308.8 K and 278.1 K, respectively with an 8.2 % improvement in exergetic efficiency. Finally, it is concluded that the multi-effect absorption system shows better performance by minimizing the irreversibility.

Original scientific paper https://doi.org/10.2298/TSCI180615291SThermal-hydraulic characteristics of water based ZrO 2 nanofluids has been investigated in a segmental baffled shell and tube heat exchanger in turbulent flow regime. The effect of Reynolds number, nanoparticle loading, mass-flow rate, and tube lay-out has been analysed on overall heat transfer coefficient. The effect of Reynolds number on the tube side pressure drop and convective heat coefficient have also been discussed. The effect of shell side mass-flow rate was also investigated on shell side heat transfer coefficient determined using Bell-Delaware method. The nanoparticle volume concentration is taken very low i. e. 0.2%, 0.4%, and 0.8%, respectively. The improvement in both tube side convective heat transfer coefficient and overall heat transfer coefficient has been observed. The maximum improvement in the convective heat transfer coefficient is found to be 14.1% for 0.8% ZrO 2 nanofluids. However, the percentage enhancement in tube side pressure drop was higher than the percentage increment in the tube side heat transfer coefficient.