| The technology of condensing heat recovery is designed to recycle the wasted air emissions of air-conditioning systems for producing hot water or providing heat for production process.It mainly aims to improve the efficiency of air-conditioning system by reducing the direct emission of condensing heat,which is one of the most significant measures for energy saving.This technique eases some issues of conventional system such as energy consumption,energy waste and environmental pollution.There has been great progress in the relevant research of condensing heat recovery both at home and abroad in recent years,which contributes to a wide range of its application.There are still many problems need to be solved in the system application of condensing heat recovery.Firstly,some key problems in the theoretical performance of this system need to be further studied such as its theoretical upper limit,the theoretical optimal configuration,the evaluation method of system performance.Comparing with the usual air conditioning system for separate cooling or heating,the increase of the condensing heat recovery process makes the evaluation method more complicated.To explore the system performance limits exactly and evaluate the system efficiently are reasonable and urgent.Secondly,the unreasonable component matching in existing condensing heat recovery systems always results in poor overall performance,energy waste and even shortened life expectancy,bringing a huge waste of social resources.It is feasible to determine the existing flaws from studying states of the working medium,thus putting forward a reasonable transformation scheme.It is a demanding issue to establish a convenient and reliable inversion simulation model for condensing heat recovery system and analyze its unreasonable factors.Thirdly,the extensive application of condensing heat recovery technology in air conditioning needs further study.At present,air-conditioning equipment with hot water supply is the most widely used condensing heat recovery technology,but the application of this technique is far more than the supply of hot water.With the improvement of medical system and the needs of medical research,the high demand for air conditioning system with constant temperature and humidity environment in operating room and biological laboratory has been rapidly increased.It is an important task to carry out the application research of air conditioning condensing heat recovery in air conditioning process and to explore an energy efficient and economical scheme.This paper conducts theoretical and experimental research on the problems encountered in the existing air-conditioning condensing heat recovery system.A thermodynamic model of condensing heat recovery based on irreversible Carnot refrigeration cycle is proposed.Three heat sources(high temperature heat source,that is the ambient environment;low temperature heat source,that is chilled water and other refrigerant;heat recovery sources,that are hot water,hot air and other heat carrier)thermodynamic equation is established when considering different irreversible factors,such as heat leakage,heat transfer resistance,heat loss of auxiliary pipe.Based on the comprehensive and systematic summarization of existing research of finite kinetics of the inverse Carnot cycle,the performances of all heat recovery air-conditioning system and partial heat recovery air-conditioning system are optimized respectively with the cooling efficiency,heat recovery efficiency and comprehensive energy efficiency ratio as the optimization target.The optimal range of condensing heat recovery in air-conditioning system is defined.The influence of irreversible loss such as heat leakage,thermal resistance and friction on the target value is analyzed,and the optimization of the exergy efficiency of the condensing heat recovery system is further discussed.Meanwhile,a quasi-static inversion equation based on heat balance and pressure balance is established based on the structural parameters of an air-cooled heat pump unit with condensing heat recovery function,and the external parameters of a cycle of this condensing heat recovery system are measured.A condensing heat recovery operation is measured for one cycle.The internal parameter variation process,state distribution and the working state of the heat transfer unit are deduced by the inversion model.The temperature of the compressor inlet and outlet and real-time power are measured by the test to verify the inversion result.Then the unreasonable factors of the air-cooled heat pump unit with the condensing heat recovery function are finally found and a reasonable optimization and transformation scheme is put forward.This paper presents an air-conditioning system which uses a built-in heat pump cycle and recovers the condensing heat as air reheat source(condensing heat recovery fresh air system)based on the object of a constant temperature and humidity air-conditioning system in a clean operating room of a hospital in central and southern China.The applicability and energy consumption of different air conditioning methods under the design conditions are analyzed,and the application range and energy saving effect of the new system are discussed.The generalized finite time thermodynamics optimization method based on the inductive formula of the compressor performance curve is proposed,and the optimal configuration and the best energy efficiency coefficient of the new system are analyzed.The thermodynamic optimization method is applied to optimize the thermal economic performance of the system based on the measurement.Furthermore,an experimental unit of condensing heat recovery fresh air system is established and tested.The experimental results are compared with the results of the finite time thermodynamics model based on the inductive formula of the compressor performance curve.The experimental results are compared with the theoretical optimization values.The errors between the experimental results and the theoretical optimization values are analyzed,and the main influencing factors that lead to these errors are analyzed.This paper proposes new methods on the structural optimization,performance evaluation and optimization of the air conditioning condensing heat recovery system.It mainly aims to provide theoretical guidance for the optimization design,system transformation and related standard formation,development and improvement of the condensing heat recovery system. |
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