热交换器内的冷热流体实现热量传递需要消耗泵功.如何科学定量评价其能源效率,是学术界和行业都迫切需要解决的问题,对提升工业节能减排有重要意义.本文通过理论分析热交换器水水无相变流动与传热综合特性,提出了一种能效评价指标EEI(=k/ p^n,总传热系数k与压力梯度 p).EEI反映了热交换器的固有能效属性,代表热交换器消耗单位折合流动压降获得的传热系数.当温差与流体流量相同时,对于相同换热面积和相同流体流动长度的热交换器而言,能效指标EEI越大,消耗单位折合泵功获得的热流量越大.换热面积变化对能效指标无影响,通过合理选取指数n,可使EEI与流速无关或为弱相关关系.能效指标具有良好的稳定性,依据性能测试国标获得的热交换器能效评价结果可以代表热交换器的能效水平.结合板式热交换器水水无相变流动传热性能数据库,得到了该类热交换器能效评价指标的指数n,以及行业总体的能效指标分布,为划分板式热交换器能效水平提供了依据.
In heat exchangers, heat transfer between the cold and the hot fluid consumes pumping power. Evaluating the energy efficiency of this process scientifically and quantitatively is an urgent issue for both academic research and industrial applications, and has important significance to energy saving and emission reduction. We comprehensively analyzed the flow and heat transfer characteristics of water-water heat transfer process without phase-change in a heat exchanger, and proposed the energy efficiency index (=k/ p^n, k is overall heat transfer coefficient and p is flow pressure gradient). EEl reflects the inherent energy efficiency properties of a heat exchanger, which represents the overall heat transfer coefficient per equivalent flow pressure drop consumption. At a given temperature difference and fluid flow rate, for the heat exchangers with the same heat transfer area and fluid flow length, bigger EEl means a lager heat transfer rate per equivalent pumping power consumption. EEl is independent on the heat transfer area; no dependence or weak dependence on the flow velocity can be achieved by choosing the index n reasonably, indicating a good stability of EEl. Evaluation result based on national standard of heat exchanger performance test measured could represent the energy efficiency of the heat exchanger. Combined with the water-water heat transfer process without phase-change flow and heat transfer performance database of the plate heat exchangers, the value of index n and the overall EEl distribution of plate heat exchangers in industry are obtained, providing a basis for the classification of the energy efficiency of plate heat exchangers.