ABSTRACT

The paper presents a gas-water heat exchanger based on the technology of a microheat pipe. The heat exchanger parameters, such as inlet and outlet temperature of flue gas, wind speed and inlet and outlet temperature of the water, were measured in practice. The analysis data showed that the temperature difference between the flue gas and the flue gas before and after heat exchange increased with the inlet temperature. At the same time, the water temperature difference remained unchanged. This paper analyzed the influence of different inlet temperatures and wind speed on heat transfer using the control variable method. It was found that the inlet temperature of flue gas was 190°C and the heat transfer efficiency was stable above 0.7 when the heat transfer was maximum, which was higher than the national standard. The irreversibility of the heat transfer process was analyzed by introducing the dimensionless equivalent thermal resistance R* and the thermal conductivity N*, which were derived from the dissipation number of the entransy. It was found that the heat exchanger operated stably when the flue gas temperature and the wind speed were constant. However, when the flue gas temperature or wind speed was increased, it was appropriate to use a lower wind speed to maintain the heat transfer performance before the temperature reached the critical temperature. After getting the critical temperature, the heat transfer performance was compared with the effective degree-NTU method and the effective degree-thermal conductivity method.

摘要

本文提出了一种基于微热管技术的气水换热器。实际测量了烟气进出口温度、风速、水进出口温度等换热器参数。分析数据表明，随着入口温度的增加，换热前后烟气与烟气的温差增大。与此同时，水温差保持不变。采用控制变量法分析了不同入口温度和风速对传热的影响。结果发现，烟气入口温度为190℃，最大传热时传热效率稳定在0.7以上，高于国家标准。通过引入由火积耗散数导出的无因次等效热阻R*和热导率N*，分析了传热过程的不可逆性。结果发现，当烟气温度和风速一定时，换热器运行稳定。但当烟气温度或风速升高时，在温度达到临界温度之前，宜采用较低的风速来维持传热性能。得到临界温度后，将传热性能与有效度-NTU法和有效度-导热系数法进行比较。这是从火积的耗散数导出的。结果发现，当烟气温度和风速一定时，换热器运行稳定。但当烟气温度或风速升高时，在温度达到临界温度之前，宜采用较低的风速来维持传热性能。得到临界温度后，将传热性能与有效度-NTU法和有效度-导热系数法进行比较。这是从火积的耗散数导出的。结果发现，当烟气温度和风速一定时，换热器运行稳定。但当烟气温度或风速升高时，在温度达到临界温度之前，宜采用较低的风速来维持传热性能。得到临界温度后，将传热性能与有效度-NTU法和有效度-导热系数法进行比较。在温度达到临界温度之前，宜采用较低的风速来维持传热性能。得到临界温度后，将传热性能与有效度-NTU法和有效度-导热系数法进行比较。在温度达到临界温度之前，宜采用较低的风速来维持传热性能。得到临界温度后，将传热性能与有效度-NTU法和有效度-导热系数法进行比较。