Experimental study of thermally stratified hot water storage tanks

An evaluation of ASHRAE Standard 94-77 for testing water tanks for thermal storage

“…13 Prior to all testing, the various type-T thermocouples used for the temperature difference measurements were calibrated. The calibration was done in two steps.…”

“…The ordinate represents the difference between the inlet and outlet transfer fluid temperatures normalized by the step change in temperature. At, (identical concept utilized in Figure 16), The abscissa represents a non-dimensional time defined by: tf^tf At T TSC (13) A value of non-dimensional time equal to 1.0 corresponds precisely to the test fill time or fluid dwell time of a perfectly-insulated, completely-stratified water tank. It is noted that the area under the curve on such a plot represents the amount of energy capable of being stored relative to the ideal device.…”

“…Upon completing the tests and analysis of data described above, it was decided to reanalyze the results obtained in accordance with a recent paper dealing with the stratification of hot water tanks [13],…”

“…The test procedure utilized in [13] was identical to the discharge tests described in this paper. That is, the cold transfer fluid (water) was introduced into the bottom of the model tanks and the hot fluid removed from the top elevation.…”

“…A unique concept of extraction efficiency, n, was introduced in [13]. It is defined as: Several factors thought to influence the extraction efficiency were studied in reference [13].…”