Library Subscription: Guest

ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Latent heat recovery from actual flue gas

Get access (open in a dialog) DOI: 10.1615/IHTC12.5480
6 pages

Abstract

Latent heat recovery from exhaust flue gas is a key technology to improve the thermal efficiency of power plants, fuel cells and boilers. A prediction method has been proposed for the design of heat exchanger to recover the latent heat in the flue gas. For the condensation of steam on heat transfer tubes, the modified Sherwood number taking account of the mass absorption effect on the wall was used. The thermal hydraulic behavior was experimentally studied in several heat exchangers for the latent heat recovery fromactual flue gas generated with the combustion of air-fuel or oxy-fuel. The steam mass concentration of the flue gas was approximately 10% in the air-fuel combustion and 30% in the oxy-fuel combustion. The countercurrent cross-flow heat exchangers consisted of bare tubes or spirally finned tubes of fin pitch 5 to 10mm. The total heat recovered in the experimental heat exchangers was 55 to 900 kW. Generally, the experimental results agreed well with the present one-dimensional prediction code. Finally, the prediction code was used on the parametric study of the heat exchanger design for the latent heat recovery. The thermal-hydraulic behavior was calculated for several kinds of heat exchangers using finned tubes or bare tubes. The calculation result indicated that the most compact heat exchanger was that using the bare tube of small diameter. So the compact countercurrent cross-flow heat exchanger using small bare tubes of SUS304 was designed and constructed to prove its high ability. The proposed compact heat exchanger was considered to be preferable for the latent heat recovery fromthe flue gas and the prediction code was useful for the design of the compact heat exchanger.