Application Of Gravity Heat Pipe In Flue Gas Waste Heat Recovery Of Gas Boiler Heating System

In recent years,with the implementation of coal-to-gas projects,the gas-fired heating system has been gradually implemented,and the proportion of natural gas consumption in energy consumption has continued to increase.In order to avoid the occurrence of "gas shortage" phenomenon,in response to the "energy saving and emission reduction" policy,the energy cascade utilization method is adopted to recover and reuse the waste heat of the gas boiler.In this paper,the gravity gas-liquid heat pipe heat exchanger is used to treat the waste heat recovery and reuse of two 2.8WM self-contained gas boilers in the heating system.According to the parameters of the project conditions,the conventional design method and the overall design idea are used to select the equipment for the gravity heat pipe gas-liquid heat exchanger.The 4-row tube gravity heat pipe heat exchanger is used to recover the waste heat from the low-temperature flue gas.The energy efficiency of the heat pipe heat exchanger in the system operation is analyzed through the parameter detection of the actual operation condition.When the heat and heat capacity of the heat exchanger is higher than the heat capacity(MC)When the ratio is between 0.26-0.60,the temperature difference between the inlet and outlet of the flue gas side is between 5.2 and 9.6 °C,and the heat recovery efficiency of flue gas is between 6.36% and 8.76%.The temperature difference between the water inlet and outlet of the heat exchanger ranges from 11.2 to 28.6 °C.At this time,the energy efficiency of the gravity gas-liquid heat pipe heat exchanger is between 20% and 40%,and the maximum energy efficiency of the heat pipe heat exchanger appears in the heating.At the peak,the maximum energy efficiency value is 40%,and the ratio of the hot and cold fluid to the heat capacity(MC)is 0.3.The fluent software was used to simulate the flue gas side of the heat pipe heat exchanger,and the distribution of each flow field was analyzed.By comparing the temperature field distribution,it is found that the error between the simulated value and the measured value is within 6.4%,indicating that the numerical simulation results can well reflect the temperature distribution of the heat exchanger in the real situation.Through the simulation analysis of the same inlet temperature and different inlet velocities of 1.5m/s,2m/s,2.5m/s,3m/s and 4m/s,the temperature of the flue gas in the direction of the airflow is Decrease the trend,as the inlet flow rate increases,the temperature gradient along the airflow direction increases,the denser the isotherm,the higher the outlet temperature;the flue gas has a larger temperature gradient on the windward side of the heat pipe,and the heat transfer effect is good,in the leeward Due to the double eddy current phenomenon,the heat transfer effect of the heat pipe is relatively low.As the flow velocity increases,the turbulence intensity increases,the turbulent side flue gas flow disturbance becomes stronger,the heat transfer is strengthened,and the isotherm becomes Dense and the reflow area is decreasing.The flow of the flue gas flows through the wall of the heat pipe,and the maximum flow velocity appears at the narrowest flow cross section.The pressure difference between the inlet and outlet of the heat exchanger increases with the increase of the inlet flow velocity.By simulating the same speed and different inlet temperatures,the variation of the temperature field distribution in the heat pipe heat exchanger is similar.In the direction of the gas flow,the temperature gradient change position appears at the same point of the heat exchanger.The inlet flow rate is constant,and the temperature change rate of the high temperature flue gas inlet and outlet is higher than the temperature change rate of the low temperature inlet and outlet.