New formula proposal for the determination of variable speed pumps efficiency
ABSTRACT The use of pumps which work with variable rotation speed consists of an appropriate tactics for reduction of energy costs in the pump systems. In case of change in speed, the pump starts to work in a new flow pattern, head and efficiency values. Two empirical formulas can be found in the li...
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Veröffentlicht in: | Revista brasileira de recursos hídricos 2018-01, Vol.23 |
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Sprache: | eng |
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Zusammenfassung: | ABSTRACT The use of pumps which work with variable rotation speed consists of an appropriate tactics for reduction of energy costs in the pump systems. In case of change in speed, the pump starts to work in a new flow pattern, head and efficiency values. Two empirical formulas can be found in the literature in order to estimate the final efficiency of a pump in this situation. This article aims at assessing the accuracy of these formulas and, next, to present a new proposal for the efficiency estimate in the new operating conditions. 50 pumps have been chosen and, for each of them, the above-mentioned formulas have been assessed in three procedures of speed reduction. The analysis of these equations’ accuracy has been accomplished by means of the comparison between the efficiencies estimated by them with the efficiencies calculated with the aid of the affinity laws. The results indicated that, in 95 of the 150 analysis procedures accomplished, the formula proposed presented estimates which have shown to be more precise than the other two formulas. It has also been possible to verify that the average of error detected through the procedure of the new formula (1.60%) has been lower than the average of the other two (1.93% and 2.22%). In light of this fact, the use of the equation here presented is considered advantageous since, from their more accurate efficiency estimates, the calculations for power and energy are also more precise.
RESUMO O uso de bombas que funcionam com velocidade de rotação variável configura uma tática adequada para que sejam reduzidos os custos de energia nos sistemas de bombeamento. Na ocasião da mudança de velocidade, a bomba passa a trabalhar em novo regime de vazão, carga manométrica e valores de rendimento. Podem ser encontradas na literatura duas fórmulas empíricas para se estimar o rendimento final de uma bomba nessa situação. Este artigo objetiva avaliar a precisão dessas fórmulas e, em seguida, apresentar uma nova proposta para a estimativa do rendimento nas novas condições de operação. Escolheram-se 50 bombas e, para cada uma, as fórmulas mencionadas foram avaliadas em três procedimentos de redução de velocidade. A análise da precisão dessas equações foi realizada através da comparação dos rendimentos estimados por elas com os rendimentos calculados com o auxílio das leis de semelhança. Os resultados apontaram que, em 95 dos 150 procedimentos de análise realizados, a fórmula proposta apresentou estimativas mais precisas do q |
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ISSN: | 1414-381X 2318-0331 2318-0331 |
DOI: | 10.1590/2318-0331.231820180003 |