A temperature pre-rectifier with continuous heat storage and release for waste heat recovery from periodic flue gas

Flue gas from periodic furnaces with large temperature fluctuation is difficult to be recovered by regular heat exchangers. To recover that unstable waste heat, a Temperature Pre-Rectifier (TPR) with honeycombed structure is developed to smooth down the temperature fluctuation by continuous heat-storing and releasing. A three-dimensional model with unsteady flow and heat transfer is constructed to analyze the heat transfer process. Temperature rectification rate η is defined to quantify the smoothing-down effect of temperature fluctuation. The η exhibit the most efficient performance when relative scale (s/δ) is 1.0. The optimized honeycomb size sopt increases exponentially with the inlet temperature fluctuation intensity ξinlet. The η is increased with dimensionless length l*. TPR with segmented structure (s and δ decreased in each segment) can enhance the η with relatively shorter length. Three-segmented structure with a proportion of 0.18:0.33:0.49 can achieve η higher than 0.947, which is recommended for application. Industrial experiments verified that the temperature fluctuation is rectified from 568~1709 K to 1089~1174 K (η = 0.926). A new perspective on waste heat recovery of periodic flue gas based on TPR is provided, and enhancing the efficiency of TPR may be a future challenge.