Thermal analysis of a three-layered radiant porous heat exchanger including fluid flow simulation

Abstract

Based on an effective energy conversion method between flowing gas enthalpy and thermal radiation, a three-layered type of porous heat exchanger (PHE) has been proposed. The PHE has one high temperature (HT) and two heat recovery (HR1 and HR2) sections. In HT section, the enthalpy of gas flow converts to thermal radiation and the opposite process happens in HR1 and HR2. In each section, a 2-D rectangular porous medium which is assumed to be absorbing, emitting and scattering is presented. For theoretical analysis of the PHE, the gas and solid phases are considered in non-local thermal equilibrium and separate energy equations are used for these two phases. Besides, in the gas flow simulation, the Fluent code is used to obtain the velocity distribution in the PHE from inlet to outlet section. For thermal analysis of the PHE, the coupled energy equations for gas and porous layer at each section are numerically solved using the finite difference method. In the computation of radiative heat flux distribution, the radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The effects of scattering albedo, optical thickness, particle size of porous medium and inlet gas temperature on the efficiency of PHE are explored. Numerical results show that this type of PHE has high efficiency especially when the porous layers have high optical thickness. The present results are compared with those reported theoretically by other investigators and reasonable agreement is found.

Keywords

Porous heat exchanger discrete ordinates method radiation

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References

Echigo R. Effective energy conversion method between gas enthalpy and thermal radiation and application to industrial furnaces. In: Proceeding of the 7th international heat transfer conference, München, vol. 6, 1982, pp.361–366.

Wang

Tien

. Thermal insulation in flow systems combine radiation and convection through a porous segment. J Heat Transfer 1984; 106: 453–459.

Echigo R. Heat transfer augmentation in high temperature heat exchangers. In: High temperature equipment, hemisphere, Washington, DC, USA, 1986, pp.41–72.

Tanigawa

Hanamura

Echigo

. Effective heat exchange method by a pair of porous radiative converters. Trans Jpn Soc Mech Eng 1991; 57(533): 302–308.

Echigo

Tomimura

Yoshiazwa

. Effective energy conversion method between gas enthalpy and thermal radiation (effects of gaseous radiation and incoming thermal radiation). Rep Inst Adv Mater Study Kyusyu Univ 1988; 2(1): 53–66.

Yoshida

Yun

Echigo

. Transient characteristics of combined conduction, convection and radiation heat transfer in porous media. Int J Heat Mass Transfer 1990; 33(5): 847–857.

Gandjalikhan Nassab

. Transient characteristics of an energy recovery system using a porous medium. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2002; 216: 387–394.

Tomimura

Hamano

Honda

. Experimental study on a multilayered type gas-to-gas heat exchanger using porous media. Int J Heat Mass Transfer 2004; 47: 4615–4623.

Gandjalikhan Nassab

Maramisaran

. Transient numerical analysis of a multi-layered porous heat exchanger including gas radiation effect. Int J Thermal Sci 2009; 48: 1586–1595.

10.

Keshtkar

Gandjalikhan Nassab

. Theoretical analysis of porous radiant burners under 2-D radiation field using discrete ordinates method. J Quant Spectrosc Radiat Transf 2009; 110: 1894–1907.

11.

Andrade

JS Jr

Costa

UMS

Almeida

. Inertial effect on fluid flow through disordered porous media. Phys Rev Lett 1999; 26: 5249–5252.

12.

Rahimianv

Pourshaghaghy

. Direct simulation of forced convection flow in a parallel plate channel filled with porous media. Int Commun Heat Mass Transf 2002; 29(6): 867–878.

13.

Sozen

Vafai

. Longitudinal heat dispersion in porous beds with real-gas flow. J Thermophys Heat Transf 1993; 7: 153–157.

14.

Chen

Hadim

. Numerical study of non-darcy forced convection in a packed bed saturated with power-law fluid. J Porous Media 1998; 1, 2: 147–157.

15.

Leong

Jin

. Numerical and experimental study of forced convection in graphite foams. Thermal Eng 2010; 30(5): 520–532.

16.

Guo

Zhao

. Lattice Boltzmann model for incompressible flows through porous media. Phys Rev E 2002; 66(3): 036304–036304.

17.

Nabovati

Sousa

ACM

. Fluid flow simulation in random porous media at pore level using the lattice Boltzmann method. J Eng Sci Technol 2007; 2(3): 226–237.

18.

Jahanshahi Javaran

Nassab

. Thermal analysis of a 2-D heat recovery system using porous media including lattice Boltzmann simulation of fluid flow. Int J Thermal Sci 2010; 49(6): 1031–1041.

19.

FLUENT User’s Guide, Release 6.3. Lebanon: FLUENT Inc., 2006.

20.

Dullien

FAL

. Porous media – fluid transport and pore structure 1992; vol. 2. San Diego: Academic Press.

21.

Ben Kheder

Cherif

Sifaoui

. Numerical study of transient heat transfer in semitransparent porous medium. Renew Energy 2002; 27: 543–560.

22.

Modest

. Radiative heat transfer, New York: McGraw-Hill, 2003.

23.

Talukdar

Mishra

Trimis

. Heat transfer characteristics of a porous radiant burner under the influence of a 2-D radiation field. J Quant Spectrosc Radiat Transf 2004; 84: 527–537.