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Falling-film drain water heat recovery (DWHR) systems are heat exchangers used to recover energy from warm water travelling down vertical drainpipes. DWHR systems are rated at constant inlet temperatures at multiple flow rates while maintaining an equal flow rate through both sides of the heat exchanger. The outcome of the rating system is an effectiveness value that is the main metric used to sell DWHR systems to the public. Unfortunately, the rated conditions may not be representative of what occurs during operation in a typical house. The present work aims to bridge this gap by presenting several semi-empirical correlations that are combined into a model capable of predicting the steady-state performance of a DWHR system at variable temperatures and flow rates, based on data generated during the rating process. This model is then validated experimentally for eight different DWHR systems for a total of 135 validation cases. The results show that the model is very effective at estimating the performance of DWHR systems for validation cases, and the mean absolute percentage error for the model predictions versus the experimental results is less than 3%.
Ramin Manouchehri; Michael R. Collins. Modelling the Steady-State Performance of Coiled Falling-Film Drain Water Heat Recovery Systems Using Rated Data. Resources 2020, 9, 1 .
AMA StyleRamin Manouchehri, Michael R. Collins. Modelling the Steady-State Performance of Coiled Falling-Film Drain Water Heat Recovery Systems Using Rated Data. Resources. 2020; 9 (6):1.
Chicago/Turabian StyleRamin Manouchehri; Michael R. Collins. 2020. "Modelling the Steady-State Performance of Coiled Falling-Film Drain Water Heat Recovery Systems Using Rated Data." Resources 9, no. 6: 1.
Drain water heat recovery systems are heat exchangers designed to recover energy from a building's greywater, and use it to preheat incoming mains water. The rated performance of such systems is determined at controlled mains-side and drain-side inlet temperatures, and under conditions of equal flow. This work aims to experimentally investigate the impact of having unequal mains-side and drain-side flow rates on the performance of these systems. As expected, experiments show that heat exchanger performance is strongly linked to fluid inlet flow rates. However, the findings also showed that variations in either of these flow rates lead to predictable changes in performance, regardless of diameter, length, or temperature. A semi-empirical equation is established that is capable of correcting system performance for different inlet flow rates based on the rated performance results.
Ramin Manouchehri; Michael R. Collins. An experimental analysis of the impact of unequal flow on falling film drain water heat recovery system performance. Energy and Buildings 2018, 165, 150 -159.
AMA StyleRamin Manouchehri, Michael R. Collins. An experimental analysis of the impact of unequal flow on falling film drain water heat recovery system performance. Energy and Buildings. 2018; 165 ():150-159.
Chicago/Turabian StyleRamin Manouchehri; Michael R. Collins. 2018. "An experimental analysis of the impact of unequal flow on falling film drain water heat recovery system performance." Energy and Buildings 165, no. : 150-159.