Organic Rankine cycles in waste heat recovery: a comparative study

A theoretical study of organic Rankine cycles (ORCs) powered by three different waste heat sources is presented. The heat sources, all found in industrial processes, span a range of energy scales capable of powering ORCs from ∼10 kW to 10 MW. A novel method of pinch point analysis is presented, allowing variable heat input to the ORC. This study models the ORC over a range of operating conditions and with different working fluids for each heat source. Results from each source are compared to assess the influence of different heat source characteristics on optimal ORC design

Nonperiodicity of the flow within the gap of a thermoacoustic couple at high amplitudes

International audienceThe flow inside a thermoacoustic couple is investigated experimentally using particle image velocimetry. Measurements show the oscillation of the shear layers flowing out of a single stack, thus forming an asymmetric vortex street at high driving amplitudes. Development of vortices is also observed within the gap of a thermoacoustic couple. It causes the flow not to repeat from one acoustic period to another. The nonperiodicity of the flow will lead to unsteady heat transfer between the stack and heat exchangers and to the oscillation of the cooling load

Vortex identification and tracking in unsteady flows

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A strategy to eliminate all nonlinear effects in constant-voltage hot-wire anemometry

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Measurement of acoustic velocity in the stack of a thermoacoustic refrigerator using particle image velocimetry

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On the use of hot-wire anemometry in pulsating flows. A comment on 'A critical review on advanced velocity measurement techniques in pulsating flows'

International audienceIn their recent topical review, Nabavi and Siddiqui (Meas. Sci. Technol. 2010 21 042002) recommended the use of hot-wire anemometry for velocity measurements in pulsating flows, especially at high frequency. This recommendation is misleading. The procedures invoked by these authors are valid only for small-amplitude fluctuations, which are of little interest for pulsating flows. When large-amplitude velocity changes occur without flow reversal, new procedures for the correction of the nonlinearities of the hot wire are required. This case was thoroughly investigated for a constant-voltage anemometer by Berson et al (Rev. Sci. Instrum. 2009 80 045102). In addition, we show that when flow reversal occurs--a case most relevant to pulsating flows--accurate hot-wire velocity measurements are not possible because heat transfer is not well defined when velocity passes through zero and changes direction