- Author
- Liu, S. T. | Kelly, G. E. | Terlizzi, C. P.
- Title
- Evaluating the Off-Cycle Losses of a Gas-Fired, Power Vented Furnace Employing Post Purge.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Department of Energy, Washington, DC
- Report
- NISTIR 4908, August 1992, 30 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- ANSI/ASHRAE 103 | burner off-cycle | calculation procedure | DOE test procedure | furnace/boiler test | off-cycle loss | performance test | post purge | power-vented burner | tracer gas test | purging
- Abstract
- A gas-fired, induced draft furnace employing post purge for venting after the burner shut off was tested by using a continuous tracer gas measurement technique over the entire off-cycle to determine the off-cycle sensible loss for various durations of post-purge. The results were compared with those obtained by the existing optional tracer gas method described in ANSI/ASHRAE Standard 103-1988. The existing optional tracer gas procedure uses tracer gas data obtained at one prescribed time in the off-cycle along with an analytical procedure to calculate the loss. This optional procedure was found to under-estimate the off-cycle loss and to give significant error with longer post purge durations. A new analytical procedure was developed to correct the deficiency in the existing procedure. The new procedure divides the off-cycle period into two intervals. The loss during the purging interval was calculated analytically by assuming a linear variation of the flue gas temperature and a constant volumetric flow rate of the flue gas. The loss during the interval after post-purge was calculated by the existing optional tracer gas procedure where the prescribed time to measure the one point tracer gas data was delayed by the length of the post-purge interval. The total off-cycle loss calculated by the new procedure gave reasonably good agreement with the integrated results from the continuous tracer gas measurement technique over the entire off-cycle. The new procedure is simpler to apply than the one using the continuous tracer gas measurement and requires only a small increase in the data taking effort and some minor revision of the existing test and calculation procedures.