Feasibility analysis of membrane distillation in a ammonia-water absorption refrigeration system

• Main Authors: Sheng-Yen Wu, 吳聲彥
• Other Authors: Jenq-Shing Chiou
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/18965808138962139274

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 92 === ABSTRACT 　　Many popular halocarbon refrigerants (Freons) are found to have Ozone Depletion potential (ODP) and Global Warming potential(GWP), some natural inorganic refrigerants are thus regain people’s attention. Ammonia-water absorption chiller not only used ammonia (an inorganic substance) as the refrigerant, it has another advantage in the use of power source. Instead of electrical power, a relatively low grade heat is used to power the absorption chiller. From the view points of environmental protection and energy conservation, it is meaningful to investigate more in depth about this kind of chiller. 　　The cooling ability of an ammonia-water absorption chiller is closely related to the evaporation of ammonia only (not water). Since NH3 and H2O have a strong affinity, the separation of NH3 from ammonia-water solution is rather difficult and usually requires a bulky distillation tower. In this study, a new separation technique called membrane distillation (MD) is used to hopefully replace the distillation tower. 　　To ensure the feasibility of replacement, ABSIM code is applied to simulate five different absorption systems, which, in sequence, has different degree in complication to separate NH3 and can demonstrate the relation between of the degree of NH3 purity and the performance of chiller. Finally, the system with MD (call SECMD in this system) is used to replace the most complicate system using traditional distillation tower. 　　After the confirmation of feasibility study, the absorption system with MD is used in the integration system coupled with a gas-turbine power system. The heat required by absorption system is recovered from the waste-heat of turbine’s flue gases. The cooling effect obtained from absorption chiller, in turn, is used to cool down the inlet air of gas turbine. power generation capacity can then be boosted by the cooling of inlet-air temperature. Both the LiBr-H2O absorption system and NH3-H2O absorption system are considered in the integration system with a absorption chiller and a power system. Results indicate that the integration of the NH3-H2O absorption system and the gas turbine power generation system has the best improvement in both the thermal efficiency（from 29.31﹪to 33.57﹪）and the output capacity（from 52.14MW to 66.37MW）. However, the COP of NH3-H2O absorption system is relatively low, the required heat to power the absorption system is thus much higher.