Transient Turbulent Natural Convection in Vertical Tubes for Indirect Thermal Energy Storage

2015 ◽  
Author(s):  
Reza Baghaei Lakeh ◽  
H. Pirouz Kavehpour ◽  
Richard E. Wirz ◽  
Adrienne S. Lavine
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Convection Heat Transfer ◽  
Energy Storage System ◽  
Turbulent Natural Convection ◽  
Vertical Tubes

In this study, turbulent natural convection heat transfer during the charge cycle of a Thermal Energy Storage system was studied computationally and analytically. The storage fluids were supercritical CO2 and liquid toluene which are stored in vertical and sealed storage tubes. A computational model was developed and validated to study turbulent natural convection during the charge cycle. The results of this study show that the aspect ratio of the storage tube (L/D) has an important effect on the heat transfer characteristics. A conceptual model was developed that views the thermal storage process as a hot boundary layer that rises along the tube wall and falls in the center to replace the cold fluid in the core. This model shows that dimensionless mean temperature of the storage fluid and average Nusselt number are functions of a Buoyancy-Fourier number.

Transient Turbulent Natural Convection in Vertical Tubes for Thermal Energy Storage

2014 ◽  
Author(s):  
Reza Baghaei Lakeh ◽  
H. Pirouz Kavehpour ◽  
Richard E. Wirz ◽  
Adrienne S. Lavine
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Convection Heat Transfer ◽  
Energy Storage System ◽  
Turbulent Natural Convection ◽  
Vertical Tubes

In this study, turbulent natural convection heat transfer during the charge cycle of a Thermal Energy Storage system was studied computationally and analytically. The storage fluids were supercritical CO2 and liquid toluene which are stored in vertical and sealed storage tubes. A computational model was developed and validated to study turbulent natural convection during the charge cycle. The results of this study show that the aspect ratio of the storage tube (L/D) has an important effect on the heat transfer characteristics. A conceptual model was developed that views the thermal storage process as a hot boundary layer that rises along the tube wall and falls in the center to replace the cold fluid in the core. This model shows that dimensionless mean temperature of the storage fluid and average Nusselt number are functions of a Buoyancy-Fourier number.

Assessment of Natural Convection Heat Transfer in an Isochoric Thermal Energy Storage System

2015 ◽  
Author(s):  
Reza Baghaei Lakeh ◽  
Yetlanezi B. Guerrero ◽  
Karthik Nithyanandam ◽  
Richard E. Wirz
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage Systems ◽  
Storage System ◽  
Energy Storage System ◽  
Energy Storage Systems ◽  
Thermal Energy Storage System

Most of the renewable energy sources, including solar and wind suffer from significant intermittency due to day/night cycles and unpredictable weather patterns. Energy Storage systems are required to enable the renewable energy sources to continuously generate energy for the power grid. Thermal Energy Storage (TES) is one of the most promising forms of energy storage due to simplicity and economic reasons. However, heat transfer is a well-known problem of most TES systems that utilize solid state or phase change. Insufficient heat transfer impairs the functionality of the system by imposing an upper limit on the power generation. Isochoric thermal energy storage system is suggested as a low-cost alternative for salt-based thermal energy storage systems. The isochoric thermal energy storage systems utilize a liquid storage medium and benefit from enhanced heat transfer due to the presence of buoyancy-driven flows. In this study, the effect of buoyancy-driven flows on the heat transfer characteristics of an Isochoric Thermal Energy Storage system is studied computationally. The storage fluid is molten elemental sulfur which has promising cost benefits. For this study, the storage fluid is stored in horizontal storage tubes. A computational model was developed to study the effect of buoyancy-driven flow and natural convection heat transfer on the charge/discharge times. The computational model is developed using an unsteady Finite Volume Method to model the transient heat transfer from the constant-temperature tube wall to the storage fluid. The results of this study show that the heat transfer process in Isochoric thermal energy storage system is dominated by natural convection and the buoyancy-driven flow reduces the charge time of the storage tube by 72–93%.

Experimental Investigation on Enhancement of Heat Transfer in Thermal Energy Storage System Using Paraffin Wax as PCM

2015 ◽  
Vol 766-767 ◽  
pp. 457-462 ◽  
Author(s):  
N. Beemkumar ◽  
A. Karthikeyan
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Energy Storage System ◽  
Paraffin Wax ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Thermal Energy Storage System

An experimental study is conducted to investigate heat transfer enhancement in Thermal Energy Storage system (TES) with paraffin wax as a Phase Change Material (PCM). Therminol 66 is used as a heat transfer fluid (HTF) to carry the heat throughout circuit. The PCM is encapsulated in spherical shells which is stored in the storage tank. The work includes study of heat transfer rates between HTF and PCM with different encapsulation materials namely Copper, Aluminium and Brass. A series of experiments were conducted to investigate the time required and heat transfer rates of HTF during the processes of charging and discharging of the PCM. Experimentally, Copper was found to have the maximum heat transfer rate and Brass was found to have the least cost/kW of energy stored. In discharging process, the cumulative heat gained by HTF from the brass encapsulated PCM is higher (1419.8 kJ) than aluminium (1199.96 kJ) and copper (815.24 kJ). Thus it can be concluded the brass is the most economical encapsulating material for enhancing the heat transfer in a thermal storage system than copper. The heat transfer from the HTF to PCM occurs in copper are 4.9% faster when compared to Brass and 2.3% faster than Aluminum encapsulation. On the other hand, The cost per kW energy transfer from the different encapsulated materials proves that the brass is cost effective during both charging and discharging process.

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