A significant increase in the use of wood pellets for residential space heating has occurred over the past decade. The performance of two modern residential wood pellet boilers (designated PB and WPB) were evaluated including boiler thermal efficiency, thermal energy storage (TES) tank discharge efficiency, and system efficiency. A correlation applicable to both systems between the boiler thermal efficiency (ηth, in %) and the boiler output load (χ, in %) was found in the form of ηth = 52.69 ln χ – 137.7 with R2 = 0.79 (for 25 < χ < 75). This equation provides an easy, accurate estimation of the boiler thermal efficiency in field operations. The boiler thermal efficiency decreased with time and this decline was determined using a Mann-Kendall trend analysis with Sen’s slope. This decrease was primarily the result of fouling in the heat exchanger and thus, this analysis identifies the need for manual cleaning of the heat exchanger tubes to restore maximal system performance. The evaluation of the TES tank performance found that the TES tank discharge efficiency was correlated with a dimensionless function of tank inlet Reynolds number (Red) and temperature differences in the tank and inlet and outlet pipes. Overall system efficiency showed a seasonal average of 62.8%, 62.0%, and 75.8% for three heating seasons of the PB system. These results provide a comprehensive performance evaluation of these wood pellet boiler heating systems in the field over an extended period of operation.
|Titolo:||Performance Evaluation of Two 25 kW Residential Wood Pellet Boiler Heating Systems|
|Data di pubblicazione:||2017|
|Appare nelle tipologie:||2.1 Articolo su rivista |
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|043 Wang et al 2017 [E&F 31] Performance Evaluation.pdf||Article||Versione dell'editore||Open Access Visualizza/Apri|