Mass And Heat Transfer During Absorption Of Ammonia Into Ammonia Water Mixture

Through tens of years of human industrial activities, huge amounts of heat-trapping gases have been releasing to the atmosphere through the exhausts of power generation stations, factories, automobiles, etc. These gases, together with the chemical compounds and refrigerants that belong to the Chlorofluorocarbons (CFCs), have been causing our environment serious damages. Global warming and Ozone layer depletion are two examples only. For the sake of our environment it is quite important and urgent to look for applications that can utilize those tons of heat energies that are being releasing to the atmosphere. One of the most attractive applications of waste heat is an absorption refrigeration machine.A great attention is recently being directed to absorption refrigeration machines because of the advantages of utilizing Ozone-friendly working fluids and the possibility of providing them with energy from waste heat or solar.The phenomenon of absorption in absorber is very important in the refrigerator. Thus, the study on the absorption is chose in many laboratories.In the present experimental work I tried to learn some about the absorption phenomenon by allowing superheated ammonia vapor, which is existed in a cylinder, to flow into a test cell to be absorbed into ammonia liquid mixture with certain initial ammonia mass fraction. Temperaturechanges in both liquid and vapor bulks and pressure changes during absorption were measured. Two different methods were used to estimate mass transfer rate. The first one is based on approximating the measured vapor pressure decrease by least square method, then inserting this approximation into the ideal gas equation to get ammonia absorption rate. The second method is based on converting an interface estimated heat flux, which was obtained by using inverse heat conduction solution, to ammonia mass absorbed.Effects of initial ammonia concentration upon mass transfer rate have been investigated. First, It has been found that the less the initial ammonia concentration, the greater the mass transfer rate. Secondly, it has been noticed that there is a great affinity between ammonia vapor and water liquid to form ammonia aqueous.The complexity of this absorption phenomenon is that heat transfer and mass transfer occur at the same time during the chemical reaction. MacrrZehnder Two-Beam Interferometer was used for visualization. Upon the concentration distribution of the ammonia water mixture in liquid bulk during absorption, two analysis methods were established. One is based on optical fundamental theory of the interference fringes phenomenon. The other is based on the calculation of mass transfer equation.