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Preliminary Modeling, Testing, and Analysis of a Gas Tankless Water Heater. Preprint.

DE2008932897

Publication Date	2008
Personal Author	Burch, J.; Thornton, J.; Hoeschele, M.; Springer, D.; Rudd, A.
Page Count	11
Abstract	Today's gas tankless water heaters offer significant energy savings over conventional gas storage tank water heaters, but savings depends on the draw pattern. A one-node model incorporating heat exchanger mass is used to address this and other issues. Key model parameters are determined from least-squares regression on short-term data, including burner efficiency, thermal capacitance, and thermal loss coefficient. The calibrated model agrees with data to approximately 5% on Qgas, with temperature RMS deviation of approximately 4 degrees C. Efficiency with a standard realistic draw is 71%, compared to 81% predicted from standard energy-factors. Adding a small tank controlled by the tankless heater solves issues of oscillations with solar pre-heat, low-flow and hot-water-delay issues. Future work includes model refinements and developing optimal data protocols for model parameter extraction.
Keywords	Solar energy Water heaters Simulation Burners Oscillations Heat exchangers Capacitance
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	National Renewable Energy Lab., Golden, CO.
Document Type	Technical Report
NTIS Issue Number	200824
Contract Number	DE-AC36-99-GO10337

Preliminary Modeling, Testing, and Analysis of a Gas Tankless Water Heater. Preprint.

Preliminary Modeling, Testing, and Analysis of a Gas Tankless Water Heater. Preprint.
DE2008932897

Publication Date	2008
Personal Author	Burch, J.; Thornton, J.; Hoeschele, M.; Springer, D.; Rudd, A.
Page Count	11
Abstract	Today's gas tankless water heaters offer significant energy savings over conventional gas storage tank water heaters, but savings depends on the draw pattern. A one-node model incorporating heat exchanger mass is used to address this and other issues. Key model parameters are determined from least-squares regression on short-term data, including burner efficiency, thermal capacitance, and thermal loss coefficient. The calibrated model agrees with data to approximately 5% on Qgas, with temperature RMS deviation of approximately 4 degrees C. Efficiency with a standard realistic draw is 71%, compared to 81% predicted from standard energy-factors. Adding a small tank controlled by the tankless heater solves issues of oscillations with solar pre-heat, low-flow and hot-water-delay issues. Future work includes model refinements and developing optimal data protocols for model parameter extraction.
Keywords	Solar energy Water heaters Simulation Burners Oscillations Heat exchangers Capacitance
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	National Renewable Energy Lab., Golden, CO.
Document Type	Technical Report
NTIS Issue Number	200824
Contract Number	DE-AC36-99-GO10337