Assessing the performance of a gas-water heat exchanger based on micro-heat pipe technology

Abstract

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.