Theoretical Analysis Of Open Cycle Absorption Heat Transformer And Experiment On Absorber And Generator

As one of clean energies, more and more natural gas is comsumed in the urban development. With about 85-90% methane, the combustion of natural gas can produce a lot of vapour which contains the considerable latent heat. The heat recovered in a certain way can not only increase the utilization efficiency of natural gas but also reuse the recovered water. Especially for humid gas turbine cycle, the latent heat and water recovery can improve the system economy. The latent heat recovery in the condensation method is limited by the dew point of the flue gas and can hardly recover the latent heat and water simultaneously. An open cycle absorption heat transformer (OAHT) which integrates the heat pump and the liquid desiccation is a new kind of technology for the latent heat and water recovery. The CaCl₂ is considered as the desiccant and the water from the flue gas as the working fluid. The latent heat and water can be recovered simultaneously. Theoretical analysis and experimental research are developed. This paper is summarized as follows:(1) In order to compare with the condensation method, the heat and water recovery from the OAHT is analyzed in the flow sheet simulation. The amount of latent heat and water recovery in OAHT is more than in the condensation method which is limited by the dew point of the flue gas.(2) The thermodynamic analysis of the OAHT is developed. The coefficient of performance (COP) of the system is 0.65, which is not less than the COP of the closed cycle. The exergy efficiency of the system is 27.11%, which can be improved by reducing the exergy loss of absorber and generator. The exergy analaysis shows that the condenser is just used for water recovery.(3) A one-dimensional model is developed in order to study the heat and mass transfer in the falling film absorber. The mass transfer coefficient is reasonable by comparing with reference. The inlet parameters of the absorber affect the solution and the cooling water temperature more than the gas temperature. Increasing the height and the radium of the falling film tube is good to water and heat recovery.(4) The off design model of OAHT is set up. The off design performance is studied under the system fixed. Results show that the COP little change under this conditions. The system can sustain the stable operation. Within the same heat eject, the system has the most stable performance as the humidity of flue gas change. Flue gas temperature and flowrate, cooling water temperature and flowrate can be used as the regulation parameters to ensure the stable operation.(5) To recover the heat and water from the HAT cycle exhaust, several types of absorption heat pump are selected and incorporated into the HAT cycle. Results show that problems of water recovery and low temperature exhaust gas emission can be settled in a certain extent. The OAHT has more effect on water recovery than the closed cycle absorption heat pump. The heat pump which rejects heat at high temperature is beneficial to system efficiency; whereas the heat pump which rejects heat at medium temperature can realize heat and power generation.(6) The experiment system of OAHT is built up. The experiments on the solution absorption and regeneration have been done separately. In the solution evaporation experiments, the relation between concentration and temperature is tested under the different pressures. The relative error between the experiment results and the theoretical data is about 2%. In the absorption experiments, mass transfer is strengthened with the tangential gas inlet. Experimental results show the process of open-cycle absorption heat pump system can be realized.The effect of OAHT on heat and water recovery is proven in this study. The results have practical value, which provide theoretical basis for the further study.