Plate Diffuser Performance in Spherical Tank Thermocline Storage System

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Fahad Khan ◽  
Brian J. Savilonis
Keyword(s):  
Flow Rate ◽  
Thermal Efficiency ◽  
Volume Flow Rate ◽  
Storage System ◽  
Water Desalination ◽  
Hot Water ◽  
Discharge Process ◽  
Water Tank ◽  
Dimensionless Numbers ◽  
Spherical Tank

Thermal energy storage (TES) systems that store sensible heat in liquid media require the use of storage tanks. Spherical tanks require less building material and insulation, which might reduce the overall cost of a TES system while providing structural rigidity. The current study investigates an optimized plate diffuser in a thermocline spherical tank storage system to possibly increase the discharge flow rate without disrupting the thermocline region and without reducing the tank thermal efficiency. For low temperature (10–90 °C heat storage applications), such as heating, ventilation, and air conditioning (HVAC) and thermal water desalination, storing hot water in a thermocline system can increase the system thermal efficiency by up to 40% when compared to a fully mixed water tank and reduce the installation cost by 30% compared to a two-tank system. This study examines using a spherical tank in a thermocline system for such applications. A computational fluid dynamic (CFD) study simulated the discharge process from a spherical storage tank thermocline water system. Thermocline thickness and temperature profile in the tank were numerically determined for Reynolds number, Re = 600 and Froude number, Fr = 1.2; results were then experimentally validated. A CFD parametric study with (500 < Re < 7500) and (0.5 < Fr < 3.3): (i) determined the influence of tank flow dimensionless numbers (Reynolds, Froude, Richardson, and Archimedes) on thermal efficiency and thermocline thickness, (ii) produced an equation to predict the tank thermal efficiency using flow dimensionless numbers, and (iii) estimated the thermocline region volume occupation as a percentage of the total volume. The study of an optimized plate diffuser produced an equation for thermal efficiency based on Re and Fr numbers and estimated a thermocline volume equal to 15% of total tank volume. Flow rate ramp up by a factor of 3 was possible after the thermocline region was formed without losing tank thermal efficiency.

scholarly journals Thermal Performance Analysis of the Charging/Discharging Process of a Shell and Horizontally Oriented Multi-Tube Latent Heat Storage System

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6193
Author(s):  
Mohamed Fadl ◽  
Philip Eames
Keyword(s):  
Latent Heat ◽  
Flow Rate ◽  
Thermal Performance ◽  
Thermal Energy ◽  
Volume Flow Rate ◽  
Storage System ◽  
Volume Flow ◽  
Hot Water ◽  
Working Fluid ◽  
Heat Demand

In this study, the thermal performance of latent heat thermal energy storage system (LHTESS) prototype to be used in a range of thermal systems (e.g., solar water heating systems, space heating/domestic hot water applications) is designed, fabricated, and experimentally investigated. The thermal store comprised a novel horizontally oriented multitube heat exchanger in a rectangular tank (forming the shell) filled with 37.8 kg of phase change material (PCM) RT62HC with water as the working fluid. The assessment of thermal performance during charging (melting) and discharging (solidification) was conducted under controlled several operational conditions comprising the heat transfer fluid (HTF) volume flow rates and inlet temperatures. The experimental investigations reported are focused on evaluating the transient PCM average temperature distribution at different heights within the storage unit, charging/discharging time, instantaneous transient charging/discharging power, and the total cumulative thermal energy stored/released. From the experimental results, it is noticed that both melting/solidification time significantly decreased with increase HTF volume flow rate and that changing the HTF inlet temperature shows large impacts on charging time compared to changing the HTF volume flow rate. During the discharging process, the maximum power output was initially 4.48 kW for HTF volume flow rate of 1.7 L/min, decreasing to 1.0 kW after 52.3 min with 2.67 kWh of heat delivered. Based on application heat demand characteristics, required power levels and heat demand can be fulfilled by employing several stores in parallel or series.

Modeling and Simulation Assessment of Solar Photovoltaic/Thermal Hybrid Liquid System Using TRNSYS

2015 ◽  
Vol 813-814 ◽  
pp. 700-706 ◽  
Author(s):  
R. Geetha ◽  
M.M. Vijayalakshmi ◽  
E. Natarajan
Keyword(s):  
Modeling And Simulation ◽  
Hybrid System ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Water Flow Rate ◽  
Exergy Efficiency ◽  
Hot Water ◽  
Solar Photovoltaic ◽  
Solar Pv ◽  
Electrical Efficiency

The PV/T hybrid system is a combined system consisting of PV panel behind which heat exchanger with fins are embedded. The PV/T system consists of PV panels with a battery bank, inverter etc., and the thermal system consists of a hot water storage tank, pump and differential thermostats. In the present work, the modeling and simulation of a Solar Photovoltaic/Thermal (PV/T) hybrid system is carried out for 5 kWp using TRNSYS for electrical energy and thermal energy for domestic hot water applications. The prominent parameters used for determining the electrical efficiency, thermal efficiency, overall thermal efficiency, electrical thermal efficiency and exergy efficiency are the solar radiation, voltage, current, ambient temperature, mass flow rate of water, area of the PV module etc. The simulated results of the Solar PV/T hybrid system are analyzed for the optimum water flow rate of 25 kg/hr. The electrical efficiency, thermal efficiency, overall thermal efficiency, equivalent thermal efficiency, exergy efficiency are found to be 10%, 34%, 60%, 35% and 13% respectively. The average tank temperature is found to be 50°C.

Experimental Evaluation of a Water Source CO2 Heat Pump Incorporating Novel Gas-Cooler Configuration

2014 ◽  
Author(s):  
Portia Murray ◽  
Stephen Harrison ◽  
Gary Johnson ◽  
Ben Stinson
Keyword(s):  
Heat Pump ◽  
Flow Rate ◽  
Storage Tank ◽  
Experimental Testing ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Convection Flow ◽  
Water Tank ◽  
Forced Circulation ◽  
Side Flow

Carbon dioxide’s use as an alternative refrigerant has been increasing in popularity due to its low global warming and ozone depletion potentials. In recent years, a number of companies and researchers have investigated applications of CO2 heat pumps for water heating. This study investigates the experimental testing of a CO2 heat pump water heater (HPWH) at Queen’s University. For the tests, the conventional factory gas-cooler on an Eco-cute unit and air-source evaporator was replaced with a specially designed brazed-plate gas-cooler. It rejected heat to a 273 litre hot water and the evaporator sourced heat from a warm water supply. Experiments were conducted using both forced and natural convection (i.e., thermosyphon) flow between the gas-cooler and hot water tank. Thermosyphon flow was studied to evaluate its effects on storage tank stratification and heat pump operation (i.e., coefficient of performance). Results were compared to forced circulation cases run over a range of flow rates. In the forced convection flow test, it was observed that a decrease in gas-cooler average water temperature increased the coefficient of performance (COP) non-linearly and an increase in the water-side flow rate increased the COP and the effectiveness of the gas-cooler. The thermosyphon had an average flow rate of 0.75 L/min and an average COP of 3.1. Thermosyphon flow kept the hot water tank fully stratified until fully charged. Water was delivered at an average of 70°C. It was also observed that thermosyphon flow rate depended on the state of charge (i.e., temperature distribution) in the storage tank. In order to increase the performance, a gas-cooler with a lower pressure drop should be used to increase the thermosyphon flow rate.

scholarly journals A METHODOLOGY FOR EVALUATING FIELD PERFORMANCE AND EMISSIONS OF A GAS MICROTURBINE BASED COGENERATION SYSTEM

2008 ◽  
Vol 7 (1) ◽  
pp. 21
Author(s):  
A. F. Orlando ◽  
M. M. Huamani ◽  
J. V. Araujo
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
New Technology ◽  
Field Performance ◽  
Electrical Energy ◽  
Hot Water ◽  
Evaluation Procedure ◽  
Water Tank ◽  
Performance And Emissions ◽  
Cogeneration System

Due to its high economic impact, when a new technology is handed over from manufacturer to customer, the contractually fixed guarantees and specifications have to be proven. Besides guarantees concerning environmental tasks, such as flue gas emissions, the availability and performance data of the new technology are the key issue. Field performance usually lacks very accurate measuring equipments and stable measurement conditions, as in many manufacturer testing laboratories. In this work a methodology was developed to evaluate performance and emissions under field conditions, together with a critical analysis of the resulting uncertainty of the main parameters, which are representative of the system performance, which was also detailed. In order to overcome field measurement difficulties, a methodology was used to measure combustion air flow rate from emission and gas flow rate measurements. The evaluation procedure was demonstrated by testing a microturbine based cogeneration system, which comprises a microturbine, a heat recovery system, and a steel storage hot water tank, providing electrical energy to Pontifical Catholic University of Rio de Janeiro grid and thermal energy for heating domestic water in cogeneration to its gymnasium showers. Data were acquired at carefully chosen stable test periods in which the gas microturbine was setup to produce electrical energy at nominal power outputs of 100, 75, 50 and 25% of maximum load. In addition, this paper presents an economical analysis for the system, which operates during peak hours (17:30 to 20:30) from Monday to Friday.

Thermal Stratification in Spherical Tanks

2014 ◽  
Author(s):  
Fahad Khan ◽  
Brian J. Savilonis
Keyword(s):  
Reynolds Number ◽  
Froude Number ◽  
Parametric Study ◽  
Richardson Number ◽  
Storage System ◽  
Discharge Process ◽  
Flow Parameters ◽  
Spherical Tank ◽  
Proportional Decrease ◽  
Tank Diameter

Spherical tanks have the potential for cost reduction in sensible thermal energy storage (TES) systems, by using less tank building material and insulation. The current CFD study compares the Thermal Efficiency (TE) of a thermocline storage system in a spherical tank to a cylindrical tank of the same volume. A parametric study is then performed on a spherical tank during the discharge process to determine the flow parameters that govern the thermocline formation and entrainment. The following parameters are used: tank diameter to inlet diameter ratio D/d = 10, inlet velocity (0.02–0.1 m/s), and ΔT (10–70° C), leading to an inlet Froude number (0.4–3), inlet Reynolds number (500–7500), and tank Richardson number (2–100). The results show a significant correlation between the inlet Reynolds and inlet Froude numbers, and the tank TE, in addition to a weak correlation between the tank Richardson number, based on the tank diameter, and the tank TE. The parametric study also shows a maximum tank TE at a Froude number equal to 0.5, and a proportional decrease of TE as the Reynolds number increases.

A New Approach to the Design of the Large Turbofan Power Plant

1995 ◽  
Vol 209 (2) ◽  
pp. 85-104
Author(s):  
G L Wilde
Keyword(s):  
Power Plant ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Dominant Factor ◽  
Gas Generator ◽  
Propulsion Efficiency ◽  
Turbofan Engines ◽  
Cruise Flight

The lower direct operating costs of the Big Twin subsonic transports encourage the building of ever larger turbofan engines installed on the wings. The steadily improving reliability of the turbofans and the good safety statistics of twin-engined aircraft over many years encourages this trend. Fuel economy is still the dominant factor in determining the design layout of turbofan engines. It requires the combination of the highest possible thermal efficiency of the gas generator core of the engine with optimum propulsion efficiency of the power plant as a whole in cruise flight, allowing for engine nacelle drag and nacelle to wing interference drag. High thermal efficiency and high propulsion efficiency together, lead to relatively small volume flow rate gas generators and high volume flow rate propulsion fans. The resulting geometrical mismatch between the compressors and turbines of the principal turbomachinery components within the engine, introduces losses that penalize the performance gains expected from theoretical considerations of thermodynamics cycle and component efficiencies alone. The paper presents two possible turbofan design layouts intended to overcome the limitation of current turbofan power plant designs. The aim is to design a power plant with the highest thrust per unit frontal area combined with the highest air miles per gallon in cruise flight.

Novel epoxy/anhydride alternatives for biological electron microscopy: Physical and performance characteristis of embed 812 and LX 112 in combination with NSA/NMA/DMAE

1989 ◽  
Vol 47 ◽  
pp. 1000-1001
Author(s):  
Joe A. Mascorro ◽  
Gerald S. Kirby
Keyword(s):  
Electron Microscopy ◽  
Flow Rate ◽  
Succinic Anhydride ◽  
Volume Flow Rate ◽  
Mass Density ◽  
Uranyl Acetate ◽  
Volume Flow ◽  
Base Resin ◽  
And Performance ◽  
Acid Anhydrides

Embedding media based upon an epoxy resin of choice and the acid anhydrides dodecenyl succinic anhydride (DDSA), nadic methyl anhydride (NMA), and catalyzed by the tertiary amine 2,4,6-Tri(dimethylaminomethyl) phenol (DMP-30) are widely used in biological electron microscopy. These media possess a viscosity character that can impair tissue infiltration, particularly if original Epon 812 is utilized as the base resin. Other resins that are considerably less viscous than Epon 812 now are available as replacements. Likewise, nonenyl succinic anhydride (NSA) and dimethylaminoethanol (DMAE) are more fluid than their counterparts DDSA and DMP- 30 commonly used in earlier formulations. This work utilizes novel epoxy and anhydride combinations in order to produce embedding media with desirable flow rate and viscosity parameters that, in turn, would allow the medium to optimally infiltrate tissues. Specifically, embeding media based on EmBed 812 or LX 112 with NSA (in place of DDSA) and DMAE (replacing DMP-30), with NMA remaining constant, are formulated and offered as alternatives for routine biological work.Individual epoxy resins (Table I) or complete embedding media (Tables II-III) were tested for flow rate and viscosity. The novel media were further examined for their ability to infilftrate tissues, polymerize, sectioning and staining character, as well as strength and stability to the electron beam and column vacuum. For physical comparisons, a volume (9 ml) of either resin or media was aspirated into a capillary viscocimeter oriented vertically. The material was then allowed to flow out freely under the influence of gravity and the flow time necessary for the volume to exit was recored (Col B,C; Tables). In addition, the volume flow rate (ml flowing/second; Col D, Tables) was measured. Viscosity (n) could then be determined by using the Hagen-Poiseville relation for laminar flow, n = c.p/Q, where c = a geometric constant from an instrument calibration with water, p = mass density, and Q = volume flow rate. Mass weight and density of the materials were determined as well (Col F,G; Tables). Infiltration schedules utilized were short (1/2 hr 1:1, 3 hrs full resin), intermediate (1/2 hr 1:1, 6 hrs full resin) , or long (1/2 hr 1:1, 6 hrs full resin) in total time. Polymerization schedules ranging from 15 hrs (overnight) through 24, 36, or 48 hrs were tested. Sections demonstrating gold interference colors were collected on unsupported 200- 300 mesh grids and stained sequentially with uranyl acetate and lead citrate.

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