| Organic Rankine Cycle(ORC)system can utilize waste heat at medium and low temperatures to achieve the energy conservation and emissions reduction.Under offdesign conditions,the operating characteristics of ORC system are affected by various operating parameters.According to the constraints,the loop parameters can be divided into two parts.One is external parameters,which is determined by its own conditions,such as ambient temperature and mass flow of working medium,etc.The other is the internal parameters which responds to the selection of various conditions,such as evaporating pressure,pressure drop of expander,etc.The external parameters are often changed due to the external factors,such as the temperature of heat source fluctuations due to the floatability of waste heat resources,so it is necessary to evaluate the impact of these parameters on system performance.In this paper,the influence of three external parameters on the system performance was studied by reforming the existing test bench of Organic Rankine cycle.In the ORC experimental bench,with R123 as the organic working fluid,with cooling water as the cold source,heat conducting oil boiler was as the heat source.Multivariate experiments were carried out by changing heat source temperature and cooling water flow respectively.The temperature of the heat source has a significant effect on the outlet temperature of the evaporator.However,the inlet and outlet temperature of condenser is more affected by the flow rate of cooling water.The evaporating pressure rises with the increase of temperature of heat source,and the condensing pressure reduces with the increase of the flow rate of cooling water.The increase in temperature of the heat source,flow rate of cooling water are all beneficial to improving the performance of system.At the 0.025kg/s of mass flow rate of working fluid,the thermal efficiency increased by 18.8% when the flow rate of cooling water increased by 20.9%,the thermal efficiency increased by 39.2% when the temperature of heat source increased by 33.3%.The maximum network of the system is 0.518 KW,the maximum thermal efficiency is 8.2%,and the maximum electrical power is 0.156 KW,and the maximum electrical efficiency is 2.5%.In order to study the operating characteristics of ORC system on off-design conditions,the modular mathematical model for each equipment was established based on thermodynamic analysis.In order to verify the validity of the model,the simulation results by inputting the same working condition parameters into the model,were compared with the experimental results.It can be seen from the comparative analysis that the maximum relative error was no more than 15%.Therefore,this model can be used to provide theoretical guidance for subsequent studies.Since the low-pressure exhaust gas after expansion still has considerable heat energy,in order to improve the system efficiency,this paper uses the condenser heat as the heat source of building heating,and builds an ORC cogeneration simulation system based on TRNSYS platform.Taking a residential building in Lhasa as an example,the heating simulation is carried out,and the indoor temperature is adjusted by the temperature difference controller during the system operation.In the heating season,the highest residential temperature is 24℃ and the lowest is 18.11℃,which meets the heating standard,indicating that this system can meet the heating demand.The average temperature of heating supply and return water is 50.39℃/45.45℃,and the average temperature of heat storage tank is 52.24℃,which is enough to provide domestic hot water.During 120 days of operation,the net output power and thermal efficiency varied from 1.83 K to 2.49 KW,8.4% to 9.97% respectively,with an average of 1.96 KW and8.80%,and the total power generation of the system was 5633.8KW ·h. |
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