Comparison of Model-Based Flow Rate Estimation Methods in Frequency-Converter-Driven Pumps and Fans

Fluid handling systems such as pump and fan systems are found to have a significant potential for energy efficiency improvements. To deliver the energy saving potential, there is a need for easily implementable methods to monitor the system output. This is because information is needed to identify inefficient operation of the fluid handling system and to control the output of the pumping system according to process needs. Model-based pump or fan monitoring methods implemented in variable speed drives have proven to be able to give information on the system output without additional metering; however, the current model-based methods may not be usable or sufficiently accurate in the whole operation range of the fluid handling device. To apply model-based system monitoring in a wider selection of systems and to improve the accuracy of the monitoring, this paper proposes a new method for pump and fan output monitoring with variable-speed drives. The method uses a combination of already known operating point estimation methods. Laboratory measurements are used to verify the benefits and applicability of the improved estimation method, and the new method is compared with five previously introduced model-based estimation methods. According to the laboratory measurements, the new estimation method is the most accurate and reliable of the model-based estimation methods.

Ventricular rate during acute atrial fibrillation and outcome of electrical cardioversion: The FinCV Study

The impact of ventricular rate (VR) on the outcome of electrical cardioversion (ECV) of acute atrial fibrillation (AF) is currently unknown. We aimed to determine the effect of VR during acute AF on the success of ECV, recurrence of AF and occurrence of post-cardioversion complications in 30 days follow-up. All ECVs performed in patients with acute atrial fibrillation lasting <48 hours in 2 Finnish university hospitals during 2003-2010 and 1 central hospital during 2010 were retrospectively identified. A total of 6,624 ECVs were performed in 2,821 consecutive patients. VR≤60 BPM was defined low and VR≥160 BPM high. The median VR before ECV was 109 BPM. The success rate of ECV was 94.2%. Bradycardia occurred in 62 (0.9%) and thromboembolic complications in 39 (0.6%) ECVs. Low VR was observed before 75 (1.1%) ECVs and male sex was its only independent predictor. High VR was observed in 165 (2.5%) ECVs. The independent predictors of high VR were younger age, <12 h episode duration, no previous history of AF and alcohol abuse. Low or high VR were not related to the success of ECV, incidence of thromboembolic or bradycardic complications, or recurrence of AF, although VR was significantly (p<0.001) lower in the patients in whom AF recurred. In conclusion, ECV of acute AF is an effective procedure and VR during AF does not affect its efficacy, the maintenance of sinus rhythm or the incidence of bradycardic, thromboembolic or other complications during 30 days follow-up after ECV. Low VR is predominately observed in male patients, while high VR was a feature related to a shorter history of AF and high alcohol-intake.