مدل‌سازي و شبيه‌سازي يك سيستم تبريد جذبي آب-آمونياك با بررسي تاثير فشار پايين بر عملكرد سيستم

Modeling and simulation of an ammonia-water absorption refrigeration system with investigation of the low pressure effects on system performance

در اين مقاله، تاثير فشار پايين بر خواص ترمو-فيزيكي جريان، بارهاي حرارتي و عملكرد سيستم تبريد جذبي آب-آمونياك تحت دو حالت مختلف بررسي مي‌گردد. اين حالات عبارتند از بررسي تحت يك دماي ثابت ژنراتور و بررسي تحت دماهاي بهينه تعيين شده متناسب با تغييرات فشار پايين. همچنين تغييرات كيفيت اشباع مبرد ورودي-خروجي اواپراتور و ورودي ابزوربر بر حسب فشار پايين مورد توجه قرار مي‌گيرد و مقدار بهينه فشار پايين با تمركز بر حالت مبرد در نقاط مذكور و عملكرد سيستم تعيين مي‌گردد. نتايج نشان مي‌دهد كه فشار پايين بهينه بايستي با تمركز بر كيفيت مبرد در نقاط مذكور تعيين گردد.

In this paper, modeling of ammonia-water absorption refrigeration system has been carried out by EES software with mass and energy balances in all system components. Then, a computer program has been developed to examine the system's performance by coupling the MATLAB and EES softwares. The effect of low pressure on performance and operating parameters of the system under two different conditions are investigated. These conditions include operation at a constant generator temperature and operation at optimum obtained values for generator temperature proportional to low pressure variations. The investigated parameters are concentration of weak and strong solutions, mass flow rates of weak solution and refrigerant, enthalpy variations at different points of the system, generator temperature, thermal loads of all components, coefficient of performance and absorption cycle efficiency. Also, the variations of saturation quality at inlet-outlet the evaporator and inlet the absorber are considered in terms of low pressure. The optimal value of low pressure is determined by focusing on the performance of system and refrigerant saturation quality at mentioned points. As obtained results, coefficient of performance, optimal value of low pressure and generator temperature are evaluated equal to 0.473, 2.28 bar and 139.3 °C, respectively at temperatures of 35, 35 and -15 ° C for absorber, condenser and evaporator, and also it was shown that in determining the optimal value of the parameters, it is necessary to consider the refrigerant saturation quality at mentioned points as well as performance investigation as essential constraints of simulation and optimization process.