Intermittent spray cooling: A new technology for controlling surface temperature

Panão, Miguel R. Oliveira; Moreira, A.L.N.

doi:10.1016/j.ijheatfluidflow.2008.10.005

Cited by 74 publications

(33 citation statements)

References 17 publications

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“…(2). The three curves correspond to different impingement distances and the pattern is similar to the observed in intermittent spray cooling [4], and the magnitude similar to typical values found in cryogen spray cooling [7]. The maximum wall heat flux occurs 0.5-0.6 s after impact, for all distances L, and decreases thereafter, probably due to the CO2 saturation close to the impinging surface, inhibiting sublimation.…”

Section: Effect Of Distance On Dry-ice Particle Spray Coolingsupporting

confidence: 77%

See 1 more Smart Citation

Application of dry-ice for transient spray cooling

Panão¹,

Costa²,

Bernardo³

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Spray cooling systems are able to remove large amounts of heat due to phase-change. Although vaporization is the most common phase-change process used in applications requiring thermal management, the use of liquids often implies the presence of a liquid film which is known to mitigate cooling performance. Thus, it is worth exploring other approaches for spray cooling avoiding liquid films. The work presented here explores sublimation using CO2 particles (dry-ice) formed through the Joule-Thomson effect. The application of interest is the molding industry, where reducing the cycle time taking advantage of the time-frame available between the mold opening and closing during the part's extraction, allows a production increase and, consequently, a higher competitive advantage in the market. The purpose of the experiments performed in dry-ice particle spray cooling is to investigate the effect of the impingement distance (350-450mm), and injection duration, on the total energy flux removed from the surface, and cooling efficiency, in order to assess the performance of sublimation spray cooling. The results show an evolution of temperature distribution from a more homogeneous pattern with shorter pulses to a heterogeneous one for pulse durations longer than 1 s. This is particularly useful in hotspot cooling. In terms of changing the spray impact distance, the higher particle dispersion achieved with a larger distance led to a decrease in thermal performance, probably due to the saturation of CO2 close to the impact surface. However, the pattern observed for the evolution of the total energy flux removed, with a maximum around an injection duration of 0.5 s, remains unaltered. The maximum cooling efficiency, obtained for the shortest distance, is up to 30%, which is comparable to spray cooling systems based on vaporization. Keywords Dry-Ice, spray cooling, molding processes IntroductionThe optimization of cycle times in molding processes depends on the ability to improve the cooling period. Wire coil inserts inside water channels already contribute to enhance heat transfer. However, the time between the extraction of the plastic molded part and closing for initiating the next cycle presents an opportunity for an additional cooling. Although most phase-change technique involving sprays consider liquid coolants, our purpose is to avoid the formation of liquid films. Therefore, this work explores sublimation phase-change using a dry-ice (solid CO2) particle spray to assess its potential for reducing cycle times in molding processes. There are few cooling systems using dry-ice particles. To the best of our knowledge, only Linde developed a patented spot cooling system using CO2 to perform thermal management in local hotspots of molded parts [1]. However, the process operates in steady-state and may not apply in short transient cooling. Most applications using dry-ice sprays aim at surface cleaning due to the solvent properties of CO2 particles [2]. Only a few studies consider the thermal effects of its impact on ...

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Section: Effect Of Distance On Dry-ice Particle Spray Coolingsupporting

confidence: 77%

“…This implies calculating the transient (t) heat flux at the impinging surface from local (ri) temperature measurements for a given impingement distance (L). In Panão and Moreira [4], assuming an adiabatic condition at the bottom surface, the wall heat flux is given by…”

Section: Measurement Methods and Analysismentioning

confidence: 99%

Application of dry-ice for transient spray cooling

Panão¹,

Costa²,

Bernardo³

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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“…To estimate the surface temperature, thermocouples are frequently used, but these provide only point temperature information (Panão and Moreira 2009;Reichelt et al 2002;Serras-Pereira et al 2013). For this reason, infrared thermography-based techniques have been developed to provide spatially resolved temperature information as demonstrated by Schulz and Schmidt (2012) and Weickgenannt et al (2011).…”

Section: Introductionmentioning

confidence: 99%

Planar measurements of spray-induced wall cooling using phosphor thermometry

et al. 2018

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The wall cooling induced by spray impingement is investigated using phosphor thermometry. Thin coatings of zinc oxide (ZnO) phosphor were applied with a transparent chemical binder onto a steel surface. Instantaneous spatially resolved temperatures were determined using the spectral intensity ratio method directly after the injection of UV-grade hexane onto the surface using a commercial gasoline injector. The investigations showed that 2D temperature measurements with high spatial and shot-to-shot precision of, respectively, 0.5 and 0.6 K can be achieved, allowing the accurate resolution of the cooling induced by the spray. The presence of a liquid film over the phosphor coating during measurements showed no noticeable influence on the measured temperatures. However, in some cases a change in the intensity ratio at the spray impingement area, in the form of a permanent "stain", could be observed after multiple injections. The formation of this stain was less likely with increasing annealing time of the coating as well as lower plate operating temperatures during the injection experiments. Finally, the experimental results indicate a noticeable influence of the thickness of the phosphor coating on the measured spray-induced wall cooling history. Hence, for quantitative analysis, a compromise between coating thickness and measurement accuracy needs to be considered for similar applications where the heat transfer rates are very high.

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“…Moreira and Panao [32] conducted intermittent spray cooling experiments to control the surface temperature of a heat generating device. They have concluded that the frequency of injection does not have any significant effect on the spray characteristics.…”

Section: Variable Flow Spray Coolingmentioning

confidence: 99%