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Research Papers: Forced Convection

Conjugate Heat Transfer in Air-to-Refrigerant Airfoil Heat Exchangers

[+] Author and Article Information
Yutaka Ito

Tokyo Institute of Technology,
4259-G3-33-402, Nagatsuta-cho,
Midori-ku, Yokohama,
Kanagawa 226-8502, Japan
e-mail: itoyu110@00.alumni.u-tokyo.ac.jp

Naoya Inokura

Tokyo Institute of Technology,
4259-G3-33-402, Nagatsuta-cho,
Midori-ku, Yokohama,
Kanagawa 226-8502, Japan

Takao Nagasaki

Tokyo Institute of Technology,
4259-G3-33-402, Nagatsuta-cho,
Midori-ku, Yokohama,
Kanagawa 226-8502, Japan
e-mail: tnagasak@es.titech.ac.jp

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received October 28, 2013; final manuscript received April 7, 2014; published online May 21, 2014. Assoc. Editor: Giulio Lorenzini.

J. Heat Transfer 136(8), 081703 (May 21, 2014) (12 pages) Paper No: HT-13-1554; doi: 10.1115/1.4027554 History: Received October 28, 2013; Revised April 07, 2014

A light and compact heat exchange system was realized using two air-to-refrigerant airfoil heat exchangers and a recirculated heat transport refrigerant. Its heat transfer performance was experimentally investigated. Carbon dioxide or water was used as a refrigerant up to a pressure of 30 MPa. Heat transfer coefficients on the outer air-contact and inner refrigerant-contact surfaces were calculated using an inverse heat transfer method. Correlations were developed for the Nusselt numbers of carbon dioxide and water on the inner refrigerant-contact surface. Furthermore, we proposed a method to evaluate a correction factor corresponding to the thermal resistance of the airfoil heat exchanger.

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References

Figures

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Fig. 1

Heat exchange system in which refrigerant transports heat from hot section to cold section

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Fig. 2

NACA65-(12A2I8b)10 airfoil heat exchanger as test model

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Fig. 3

Configurations of tested cascade of NACA65-(12A2I8b)10 airfoils

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Fig. 4

Refrigerant recirculation loop (in case of carbon dioxide as refrigerant) and piping around airfoils

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Fig. 5

Control volumes for inverse heat transfer method based on numerical analysis of heat conduction in airfoil heat exchanger and applied boundary conditions

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Fig. 6

Schematic view of air boundary layers around airfoil heat exchangers

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Fig. 7

Experimental air Mach, Prandtl, and Reynolds numbers versus airflow direction angle from airfoil chord

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Fig. 8

Comparison of temperature distributions of airfoil heat exchangers for large and small air modified Stanton numbers

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Fig. 9

Distributions of air pressure coefficient, air local Mach number, and adiabatic air temperature corresponding to experimental results shown in Fig. 8 (air pressure coefficient data were taken from Ref. [13])

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Fig. 10

Experimental air Nusselt number for each part versus air modified Stanton number

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Fig. 11

Average air Nusselt number versus air Reynolds number at outlet at various angles-of-attack α

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Fig. 12

Comparison of experimental refrigerant Nusselt number with Dittus–Boelter, Liao–Zhao, and our proposed correlations for carbon dioxide turbulent flows

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Fig. 13

Example of correction factor for heat transfer with refrigerant temperature effectiveness ϕref and the ratio of refrigerant heat capacity rate to that of air εRA at α = 10.5 deg, i.e., ξ = 1.03 deg

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Fig. 14

Comparison of experimental air Nusselt number with estimated values calculated by our proposed method

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