Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity

The transient critical heat flux (CHF) due to exponentially increasing heat input was experimentally measured for upward water flowing in vertical small tubes. The heat generation rate was increased exponentially with a function of Qoexp (t/τ ), where, Qo is an initial heat generation rate, t repres...

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Autores principales:	Yuji NAKAMURA, Qiusheng LIU, Makoto SHIBAHARA, Koichi HATA, Katsuya FUKUDA
Formato:	article
Lenguaje:	EN
Publicado:	The Japan Society of Mechanical Engineers 2019
Materias:	transient heat input transient critical heat flux small channel vertical water flowing e-folding time Mechanical engineering and machinery TJ1-1570
Acceso en línea:	https://doaj.org/article/7759498b703648a588da8a755f73a7d9
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spelling	oai:doaj.org-article:7759498b703648a588da8a755f73a7d92021-11-29T05:34:41ZTransient critical heat flux of upward water flow boiling in vertical small tube at slow velocity2187-974510.1299/mej.18-00425https://doaj.org/article/7759498b703648a588da8a755f73a7d92019-01-01T00:00:00Zhttps://www.jstage.jst.go.jp/article/mej/6/1/6_18-00425/_pdf/-char/enhttps://doaj.org/toc/2187-9745The transient critical heat flux (CHF) due to exponentially increasing heat input was experimentally measured for upward water flowing in vertical small tubes. The heat generation rate was increased exponentially with a function of Qoexp (t/τ ), where, Qo is an initial heat generation rate, t represents time and τ is e-folding time. The test tubes were made of platinum with inner diameters of 0.7 mm and 1.0 mm, and heated lengths of 12.0 mm and 40.9 mm. The flow velocities and the inlet liquid temperatures ranged from 2.0 m/s to 8.0 m/s, 90 K to 140 K, and the inlet pressure was 800 kPa. It was obtained that the transient CHF was affected by inner diameter of test tube, liquid subcooling, flow velocity, and e-folding time. The transient CHF values increased with the increases in flow velocity and inlet subcooling. The transient CHFs increased with a decrease in e-folding time at τ <1 s, and they approached steady-state values at τ >1 s. It was understood that the heat transfer is in steady-state at τ >1 s, and it is in transient state at τ <1 s. Moreover, the values of transient CHFs at diameter of 0.7 mm were higher than those at the diameter of 1.0 mm. The correlation by Hata and Noda (2008) can express authors’ transient CHFs at e-folding time larger than about 1 s (steady-state region), however, it shows larger values than authors’ data at e-folding time smaller than 1 s (transient region).Yuji NAKAMURAQiusheng LIUMakoto SHIBAHARAKoichi HATAKatsuya FUKUDAThe Japan Society of Mechanical Engineersarticletransient heat inputtransient critical heat fluxsmall channelvertical water flowinge-folding timeMechanical engineering and machineryTJ1-1570ENMechanical Engineering Journal, Vol 6, Iss 1, Pp 18-00425-18-00425 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	transient heat input transient critical heat flux small channel vertical water flowing e-folding time Mechanical engineering and machinery TJ1-1570
spellingShingle	transient heat input transient critical heat flux small channel vertical water flowing e-folding time Mechanical engineering and machinery TJ1-1570 Yuji NAKAMURA Qiusheng LIU Makoto SHIBAHARA Koichi HATA Katsuya FUKUDA Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity
description	The transient critical heat flux (CHF) due to exponentially increasing heat input was experimentally measured for upward water flowing in vertical small tubes. The heat generation rate was increased exponentially with a function of Qoexp (t/τ ), where, Qo is an initial heat generation rate, t represents time and τ is e-folding time. The test tubes were made of platinum with inner diameters of 0.7 mm and 1.0 mm, and heated lengths of 12.0 mm and 40.9 mm. The flow velocities and the inlet liquid temperatures ranged from 2.0 m/s to 8.0 m/s, 90 K to 140 K, and the inlet pressure was 800 kPa. It was obtained that the transient CHF was affected by inner diameter of test tube, liquid subcooling, flow velocity, and e-folding time. The transient CHF values increased with the increases in flow velocity and inlet subcooling. The transient CHFs increased with a decrease in e-folding time at τ <1 s, and they approached steady-state values at τ >1 s. It was understood that the heat transfer is in steady-state at τ >1 s, and it is in transient state at τ <1 s. Moreover, the values of transient CHFs at diameter of 0.7 mm were higher than those at the diameter of 1.0 mm. The correlation by Hata and Noda (2008) can express authors’ transient CHFs at e-folding time larger than about 1 s (steady-state region), however, it shows larger values than authors’ data at e-folding time smaller than 1 s (transient region).
format	article
author	Yuji NAKAMURA Qiusheng LIU Makoto SHIBAHARA Koichi HATA Katsuya FUKUDA
author_facet	Yuji NAKAMURA Qiusheng LIU Makoto SHIBAHARA Koichi HATA Katsuya FUKUDA
author_sort	Yuji NAKAMURA
title	Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity
title_short	Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity
title_full	Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity
title_fullStr	Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity
title_full_unstemmed	Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity
title_sort	transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity
publisher	The Japan Society of Mechanical Engineers
publishDate	2019
url	https://doaj.org/article/7759498b703648a588da8a755f73a7d9
work_keys_str_mv	AT yujinakamura transientcriticalheatfluxofupwardwaterflowboilinginverticalsmalltubeatslowvelocity AT qiushengliu transientcriticalheatfluxofupwardwaterflowboilinginverticalsmalltubeatslowvelocity AT makotoshibahara transientcriticalheatfluxofupwardwaterflowboilinginverticalsmalltubeatslowvelocity AT koichihata transientcriticalheatfluxofupwardwaterflowboilinginverticalsmalltubeatslowvelocity AT katsuyafukuda transientcriticalheatfluxofupwardwaterflowboilinginverticalsmalltubeatslowvelocity
_version_	1718407653129977856

Transient critical heat flux of upward water flow boiling in vertical small tube at slow velocity

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