Abstract
Hot-water storage in residential and commercial tanks is of growing interest for peak-shifting the electrical demand associated with hot-water loads. How the water enters the tank can significantly affect the extraction efficiency of the storage. Vertical-tube inlets (VTIs) direct cold water into the tank. The VTI design influences whether large-scale mixing occurs, which can reduce the delivery capacity of the hot-water storage. In this work, the mixing at the VTI discharge was characterized by the eddy diffusivity factor (EDF) in an allometric curve fit to the ratio Re:Ri using inlet superficial velocities. The full experimental campaign tested VTI's with Re's between 170 and 22,300 and Ri's between 0 and 376. Animated visualization of the experimentally measured data is provided, showing tank temperature evolution during inlet flows. The most predictive correlations for EDF are for VTI Re in the transition zone (i.e. ~2300 < Re < ~10,000) and at a Ri corresponding to a stably stratified tank (i.e. Ri > 5). For vertical-tubes that distribute cold water below the thermocline, increasing the EDF will decrease the stratification in a hot-water tank as EDF quantifies inlet mixing. The new correlations for VTIs can be used to design and model thermally-stratified storage tanks.
| Original language | English |
|---|---|
| Article number | 104838 |
| Journal | International Communications in Heat and Mass Transfer |
| Volume | 119 |
| DOIs | |
| State | Published - Dec 2020 |
Funding
This project was supported in part by an appointment to the Oak Ridge National Laboratory HERE program, administered by ORAU through the U.S. Department of Energy Oak Ridge Institute for Science and Education.This research used resources at the Building Technologies Research and Integration Center, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This project was supported in part by an appointment to the Oak Ridge National Laboratory HERE program, administered by ORAU through the U.S. Department of Energy Oak Ridge Institute for Science and Education.This research used resources at the Building Technologies Research and Integration Center, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This work was sponsored by the U. S. Department of Energy's Building Technologies Office under Contract No. DEAC05-00OR22725 with UT-Battelle, LLC. The authors would like to acknowledge Mr. Antonio Bouza, Technology Manager ? HVAC&R, Water Heating, and Appliance, U.S. Department of Energy Building Technologies Office. The authors have no conflicts of interest to declare, as defined by the Elsevier Publishing Ethics Duties of Authors. Author statements. Joseph Rendall (Conceptualization, Investigation, Methodology, Validation, Writing ? Original Draft). Kyle Gluesenkamp (Conceptualization, Methodology, Supervision, Funding, Writing). Ahmad Abuheiba (Data curation, Software, Writing). Kashif Nawaz (Data curation, Writing - review). Anthony Gehl (Software, Writing ? review). William Worek (Supervision, Data curation, Writing ? revision). This work was sponsored by the U. S. Department of Energy’s Building Technologies Office under Contract No. DEAC05-00OR22725 with UT-Battelle, LLC. The authors would like to acknowledge Mr. Antonio Bouza, Technology Manager – HVAC&R, Water Heating, and Appliance, U.S. Department of Energy Building Technologies Office.
| Funders | Funder number |
|---|---|
| U. S. Department of Energy's Building Technologies Office | |
| U. S. Department of Energy’s Building Technologies Office | DEAC05-00OR22725 |
| U.S. Department of Energy Building Technologies Office | |
| Office of Science | |
| Oak Ridge Associated Universities | |
| Oak Ridge National Laboratory |
Keywords
- Richardson number
- Stratification
- Thermal energy storage
- Vertical tube distributor or diffuser