Description

The effects of a twisted baffle tape on the heat transfer in the center flue tube of a gas-fired water heater are investigated both theoretically and experimentally. The combustion products enter the flue tube at a temperature of about 2300 F (1260°C) and transfer heat by the combined modes of radiation and convection to the cross tape and the water-backed tube wall.

The twisted tape causes an augmentation of the convective heat transfer from the flue gases to the wall surfaces. In addition, radiative heat transfer from the relatively hot cross tape plays an important role in the heat transfer to the tube wall, which has usually been neglected in the past.

A theoretical study is performed under conditions of radiating gas flow and varying temperatures of the tube wall and cross tape along the flow direction. The results are compared to experimental measurements taken on one particular flue tube of a gas-fired water heater and are found to be in good agreement.

The heat transfer to the tube wall is enhanced by more than 50% due to the presence of the inserted tape. The velocity of the flue gases, the twist (i.e., number of turns) of the cross tape and the surface emissivities; and their influence on the performance of the flue tube is investigated in a parametric study.

Units: Dual

Citation: Symposium, ASHRAE Transactions, 1986, vol. 92, pt. 2B, Portland, OR

Product Details

Published:

1986

Number of Pages:

11

File Size:

1 file , 1 MB

Product Code(s):

D-PO-86-11-1