Absorption characteristics of NH3/NASCN working pair in an adiabatic absorber with structured packing

Adiabatic absorbers with structured packing are widely used in small and medium scale absorption refrigeration units. Also, ammonia-sodium thiocyanate is a considerable potential working pair for small-scale absorption refrigeration system. The present study experimentally analyzes the absorption characteristics of ammoniasodium thiocyanate working pair in an adiabatic absorber with stainless-steel structured packing. An adiabatic absorber filled with 4 blocks of stainless-steel structured packing as well as an experimental apparatus have been carefully designed and constructed to evaluate the absorption characteristics. Through the adjustments of working conditions of absorber such as solution inlet mass flowrate, absorption pressure and solution inlet subcooling, various experimental state points are obtained at cooling water temperatures ranging from 27.3 to 33.5 degrees C. Contrasts of parameters characterizing absorption performance have been made under these various working conditions. In the period of present experimental research, mass transfer coefficient reaches its maximum at 4.67 x 10(-6) m/s at Reynolds numbers ranging from 339 to 611. Subcooling degree of inlet solution at range of 1.7-27.1 degrees C is supposed to gain a linear relationship with absorption ratio while heat load with range of 1.05-3.09 kW of the absorber gains the reverse. Absorption pressure and solution inlet flowing intensity are considered to be the promotion factor for absorption process. Parameters such as pressure potential, approach to equilibrium factor have also been analyzed. According to all these experimental results, solution inlet flowing intensity, differences between vapor pressure and solution partial pressure (i.e. the core absorption driving force) are the two main factors which greatly influence the performance of absorption process. Variables such as absorption pressure, solution inlet subcooling and cooling water temperature can be rationally adjusted in order to increase the pressure difference, enhancing the absorption performance. The adiabatic absorber with structured packing also gains a relatively high-efficient absorption performance which is sufficient for the small-scale absorption refrigeration system. Otherwise, through this study, all the parameters' data and correlations are concluded for further study of absorption technique with ammonia-sodium thiocyanate working pair, and provide references for the designing of the adiabatic absorber with structured packing. The presents study provides significant reference for advance of research of ammonia/salt absorption refrigeration technology as well as design of structured packing adiabatic absorber with ammonia-sodium thiocyanate working pair.