Behavior and Testing Performance of a Gas Tankless Water Heater

2011 ◽  
Author(s):  
Peter Grant ◽  
Jay Burch ◽  
Moncef Krarti
Keyword(s):  
Steady State ◽  
Flow Rate ◽  
Scientific Community ◽  
Energy Use ◽  
Water Flow Rate ◽  
Heat Rate ◽  
Feedback Controls ◽  
Minimum Flow ◽  
Water Heaters ◽  
Minimum Flow Rate

Tankless water heaters present an opportunity to dramatically reduce water heating energy use. These impacts are possible because of their dramatic reduction of environmental losses through lower heat transfer areas and not keeping the heat exchanger at operating temperature between draws. The potential for energy savings has caused a lot of interest in the scientific community. However, the scientific community has not yet gained an understanding of these devices and several questions regarding their behavior remain. The areas of uncertainty include the following: 1) how these heaters behave around the minimum flow rate, 2) how well they adapt to changes in water flow rate, 3) how they behave in situations with preheated water (i.e. when used with solar water heaters) and 4) whether or not draw characteristics impact the steady state efficiency. Tests have been performed on a Rinnai R75Lsi to determine the answers to these questions for a specific heater. Tests were performed with 1) gradually changing flow rate to identify the minimum flow rate, 2) rapidly adjusting the flow rate to observe how the heater responded to suddenly changing draws, 3) temperature-flow combinations such that the minimum heat rate exceeded the required heat rate, and 4) draws under steady state conditions with varying flow rates and set temperatures. Minimum flow rate results indicate that the heater will not fire unless the flow rate surpasses 2.8 L/min and will cease firing if the flow rate decreases below 2.15 L/min while the owners manual states that the minimum flow rate is 2.3 L/min. Rapidly changing flow rate results indicate that there can be temperature fluctuations up to 9 °C and unsteady operation for up to 1 minute depending on the magnitude of the flow rate change. Tests with preheated inlet water showed that the heater uses feedback controls to avoid unstable operation at low heat rates. Steady state efficiency tests did not identify any variables which impact efficiency. Future work should include testing additional units to determine how other heaters, particularly those not manufactured by Rinnai, behave in similar situations.

The minimum flow rate of electrosprays in the cone-jet mode

2019 ◽  
Vol 876 ◽  
pp. 553-572 ◽  
Author(s):  
Manuel Gamero-Castaño ◽  
M. Magnani
Keyword(s):  
Dielectric Constant ◽  
Reynolds Number ◽  
Flow Rate ◽  
Numerical Solutions ◽  
Viscous Stress ◽  
Flow Rates ◽  
Minimum Flow ◽  
Electric Stress ◽  
Work Done ◽  
Minimum Flow Rate

Stable electrospraying in the cone-jet mode is restricted to flow rates above a minimum, and understanding the physics of this constraint is important to improve this atomization technique. We study this problem by measuring the minimum flow rate of electrosprays of tributyl phosphate and propylene carbonate at varying electrical conductivity $K$ (all other physical properties such as the density $\unicode[STIX]{x1D70C}$, surface tension $\unicode[STIX]{x1D6FE}$ and viscosity $\unicode[STIX]{x1D707}$ are kept constant and equal to those of the pure liquids), and through the analysis of numerical solutions. The experiments show that the dimensionless minimum flow rate is a function of both the dielectric constant $\unicode[STIX]{x1D700}$ of the liquid and its Reynolds number, $Re=(\unicode[STIX]{x1D70C}\unicode[STIX]{x1D700}_{o}\unicode[STIX]{x1D6FE}^{2}/\unicode[STIX]{x1D707}^{3}K)^{1/3}$. This result is unexpected in the light of existing theories which, for the conditions investigated, predict a minimum flow rate that depends only on $\unicode[STIX]{x1D700}$ and/or is marginally affected by $Re$. The experimental dependency on the Reynolds number requires the viscous stress to be a factor in the determination of the minimum flow rate. However, the numerical solutions suggest that a balance of opposing forces including the fixing viscous stress, which at decreasing flow rates may lower the acceleration of the flow to the point of making it unstable, is unlikely to be the cause. An alternative mechanism is the significant viscous dissipation taking place in the transition from cone to jet, and which at low flow rates cannot be supplied by the work done by the tangential electric stress in the same area. Instead, mechanical energy injected into the system farther downstream must be transferred upstream where dissipation predominantly takes place. This mechanism is supported by the balance between the energy dissipated and the work done by the electric stress in the transition from cone to jet, which yields a relationship between the minimum flow rate, the Reynolds number and the dielectric constant that compares well with experiments.

A Mechanistic Study on Minimum Flow Rate for the Continuous Removal of Liquids from Gas Wells

2012 ◽  
Vol 30 (2) ◽  
pp. 122-132 ◽  
Author(s):  
W. Zhibin ◽  
L. Yingchuan ◽  
L. Zhongneng ◽  
Z. Haiquan ◽  
L. Yonghui
Keyword(s):  
Flow Rate ◽  
Mechanistic Study ◽  
Gas Wells ◽  
Minimum Flow ◽  
Minimum Flow Rate

scholarly journals Solar Desalination by Humidification-Dehumidification of Air

2018 ◽  
Vol 149 ◽  
pp. 02092 ◽  
Author(s):  
J. Moumouh ◽  
M. Tahiri ◽  
L. Balli
Keyword(s):  
Water Temperature ◽  
Flow Rate ◽  
Energy Use ◽  
Mechanical Energy ◽  
Water Flow Rate ◽  
Operating Conditions ◽  
Water Desalination ◽  
Arid Zones ◽  
Transfer Coefficients ◽  
System Productivity

The importance of supplying potable water can hardly be overstressed. In many arid zones, coastal or inlands, seawater or brackish water desalination may be the only solution to the shortage of fresh water. The process based on humidification-dehumidification of air (HDH) principle mimic the natural water cycle. HDH technique has been subjected to many studies in recent years due to the low temperature, renewable energy use, simplicity, low cost installation and operation. An experimental test set-up has been fabricated and assembled. The prototype equipped with appropriate measuring and controlling devices. Detailed experiments have been carried out at various operating conditions. The heat and mass transfer coefficients have been obtained experimentally. The results of the investigation have shown that the system productivity increases with the increase in the mass flow rate of water through the unit. Water temperature at condenser exit increases linearly with water temperature at humidifier inlet and it decreases as water flow rate increases. HDH desalination systems realised on also work at atmospheric pressure; hence they do not need mechanical energy except for circulation pumps and fans. These kinds of systems are suitable for developing countries. The system is modular, it is possible to increase productivity with additional solar collectors and additional HDH cycles.

Analysis and Prediction of Minimum Flow Rate for the Continuous Removal of Liquids from Gas Wells

1969 ◽  
Vol 21 (11) ◽  
pp. 1475-1482 ◽  
Author(s):  
R.G. Turner ◽  
M.G. Hubbard ◽  
A.E. Dukler
Keyword(s):  
Flow Rate ◽  
Gas Wells ◽  
Minimum Flow ◽  
Minimum Flow Rate

scholarly journals Modelling Minimum Flow Rate Required for Unloading Liquid in Gas Wells

2020 ◽  
Author(s):  
Adesina Fadairo ◽  
Gbadegesin Adeyemi ◽  
Temitope Ogunkunle ◽  
Oreoluwa Lawal ◽  
Olugbenga Oredeko
Keyword(s):  
Flow Rate ◽  
Gas Wells ◽  
Minimum Flow ◽  
Minimum Flow Rate

The minimum flow rate scaling of Taylor cone-jets issued from a nozzle

2014 ◽  
Vol 104 (2) ◽  
pp. 024103 ◽  
Author(s):  
William J. Scheideler ◽  
Chuan-Hua Chen
Keyword(s):  
Flow Rate ◽  
Taylor Cone ◽  
Minimum Flow ◽  
Minimum Flow Rate
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