Thermal Hydraulic Analysis of a Water Tank With Large Aspect Ratio

2014 ◽  
Author(s):  
Qi Min ◽  
Li Zhang ◽  
Hongtao Wang ◽  
Junpeng Zhai
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Aspect Ratio ◽  
Hot Water ◽  
Water Tank ◽  
Large Aspect Ratio ◽  
Strong Function ◽  
Uniform Temperature Field ◽  
Cooling Pipes ◽  
Thermal Hydraulic Analysis

A special-shaped water tank with large aspect ratio and limited volume for cooling was investigated using computational fluid dynamics. The influence of a separator on the heat transfer ability in the water tank is analyzed. When there is no separator, the arrangement of cooling pipes is very important to the heat transfer and temperature field in the water tank. The total heat flux of the pipe bundle and the temperature field will become bad if the pipe bundle is arranged not uniform in the water tank. Adding a separator can greatly enhance the integral natural convection of cold and hot water in the water tank and a uniform temperature field and regular velocity field could be got. The heat transfer ability for the structure with a separator is better than the structure without a separator, and is not sensible to the arrangement of the pipe bundle. The heat transfer ability also did not change when the position of separator and pipe bundle exchanged, and is not a strong function of the distance between separator and the pipe bundle or the wall of the water tank. Finally, the inclination of the water tank is discussed.

A Study Regarding the Unsteady Heat Transfer and Phase Change

2014 ◽  
Vol 659 ◽  
pp. 353-358
Author(s):  
Gelu Coman ◽  
Cristian Iosifescu ◽  
Valeriu Damian
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Temperature Field ◽  
Temperature Distribution ◽  
Finite Elements ◽  
Experimental Research ◽  
Theoretical Study ◽  
Ice Formation ◽  
Unsteady Heat Transfer ◽  
Cooling Pipes

The paper presents the experimental and theoretical study for temperature distribution around the cooling pipes of an ice rink pad. The heat transfer in the skating rink track is nonstationary and phase changing. In case of skating rinks equipped with pipe registers, the temperature field during the ice formation process can’t be modeled by analytical methods. The experimental research was targeted on finding the temperatures in several points of the pad and also details on ice shape and quality around the pipes. The temperatures measured on the skating ring surface using thermocouples is impossible due to the larger diameter of the thermocouple bulb compared with the air-water surfaces thickness. For this reason we used to measure the temperature by thermography method, thus reducing the errors The experimental results were compared against the numerical modeling using finite elements.

Evaluation of Passive Anti-Fouling Technology Applied to CO2 Heat Pump Water Heaters

2014 ◽  
Author(s):  
Portia Murray ◽  
Stephen J. Harrison ◽  
Ben Stinson
Keyword(s):  
Heat Transfer ◽  
Water Supply ◽  
Heat Pump ◽  
Hot Water ◽  
Normal Operation ◽  
Mineral Deposits ◽  
Reverse Direction ◽  
Water Tank ◽  
Flow Rates ◽  
Water Heaters

Heat pump water heaters are increasing in popularity due to their increased energy efficiency and low environmental impact. This paper describes the experimental testing of a transcritical CO2 heat pump water heater at Queen’s University. A modified 4.5 kW Eco-Cute unit was studied. It sourced heat from a constant temperature water supply and rejected the heat to a 273 litre hot water tank through a gas-cooler. The high temperatures that occur in the gas-cooler of this unit make it ideally suited for natural convection, (i.e., thermosyphon) circulation on the potable water side. This has the potential to reduce pumping power, simplify system operation and design, and increase thermal stratification in the hot water storage tank. This configuration, however, is susceptible to the accumulation of sediments, scale and mineral deposits (i.e., fouling) in geographic regions where high mineral deposits may be present in the water supply. To counteract fouling in these cases, a passive back-flushing system was proposed to prevent the accumulation of deposits on the heat transfer surfaces of the gas-cooler. As hot water is drawn from the system, the cold “mains” supply water is directed through the gas-cooler in the reverse direction of normal operation, scouring the heat transfer surfaces and dissolving deposits of inverse-soluble salts which are a major contributor to fouling on hot heat transfer surfaces. The gas-cooler used was a specially designed unit that, although offering high performance in a compact unit, may be susceptible to the fouling and blockage of the heat transfer passages when used at thermosyphon flow rates. Experiments were conducted to evaluate the effects of the back-flush operation on heat pump performance (i.e., COP) and operation. These were conducted under controlled laboratory conditions, at a range of draw flow rates and temperatures, and are summarized in this paper.

Effect of Rib Configuration and Lateral Ejection on a High Aspect Ratio Trailing Edge Channel

2013 ◽  
Author(s):  
Rui Kan ◽  
Li Yang ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Local Heat Transfer ◽  
Large Aspect Ratio ◽  
Thermochromic Liquid Crystal ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Average Heat ◽  
Edge Channel ◽  
Heat Transfer Coefficients

Thermal issues of gas turbine blade trailing edge are complex and challenging, due to limited space for effective cooling. The trailing edge cavities are usually large aspect ratio ducts with lateral ejection. The objective of this study is to investigate the effects of different rib configurations and lateral ejection on heat transfer characteristics inside a trailing edge channel. The investigations were conducted on a large aspect ratio wedge-shaped channel with square ribs of e/Dh = 0.05, under Reynolds number 15,000. Twelve different configurations were tested: 1)three rib types, including a symmetry V-shaped rib configuration and two non-symmetry V-shaped rib configurations, of which the rib angles are 60 degrees, 2) two rib pitches, P/e = 10 and P/e = 5, 3) two flow directions, with an open tip outlet or with lateral ejection. Spatially resolved heat transfer distributions were obtained using the transient thermochromic liquid crystal experimental method. The configurations were also investigated numerically for the detailed flow field and for the validation of CFD codes. Results show that with lateral ejection, the heat transfer coefficients decrease from inlet to outlet. The heat transfer near the ejection holes is enhanced while heat transfer coefficients near the wall opposite to the exit holes decrease. The curvature of the streamlines creates a large separation area near the end of the channel and thus results in low local heat transfer coefficients. The P/e = 10 configurations have higher average heat transfer compared with P/e = 5 configurations. Average heat transfer coefficient is the highest with the center of the V-shaped rib placed at the middle of the channel, and is the lowest when the V-shaped rib center is located near the narrow part of the channel.

Thermal effect on large-aspect-ratio Couette–Taylor system: numerical simulations

2015 ◽  
Vol 771 ◽  
pp. 57-78 ◽  
Author(s):  
Changwoo Kang ◽  
Kyung-Soo Yang ◽  
Innocent Mutabazi
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Aspect Ratio ◽  
Numerical Simulations ◽  
Convective Cell ◽  
Base Flow ◽  
Large Aspect Ratio ◽  
Radial Temperature ◽  
Instability Modes ◽  
Momentum And Heat Transfer

We have performed numerical simulations of the flow in a large-aspect-ratio Couette–Taylor system with rotating inner cylinder and with a radial temperature gradient. The aspect ratio was chosen in such a way that the base state is in the conduction regime. Away from the endplates, the base flow is a superposition of an azimuthal flow induced by rotation and an axial flow (large convective cell) induced by the temperature gradient. For a fixed rotation rate of the inner cylinder in the subcritical laminar regime, the increase of the temperature difference imposed on the annulus destabilizes the convective cell to give rise to co-rotating vortices as primary instability modes and to counter-rotating vortices as secondary instability modes. The space–time properties of these vortices have been computed, together with the momentum and heat transfer coefficients. The temperature gradient enhances the momentum and heat transfer in the flow independently of its sign.

Transient Thermal Field Measurements in a High Aspect Ratio Channel Related to Transient Thermochromic Liquid Crystal Experiments

2007 ◽  
Author(s):  
Sean C. Jenkins ◽  
Igor V. Shevchuk ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Liquid Crystal ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Field Measurements ◽  
Bulk Temperature ◽  
Fluid Temperature ◽  
Thermochromic Liquid Crystal ◽  
Temperature Distributions

Measurements of transient fluid temperature distributions were made in a high aspect ratio (4:1) internally ribbed two-pass channel relating to the measurement of heat transfer using the transient thermochromic liquid crystal (TLC) technique. The temperature field was measured at several positions leading up to and around the 180° bend in a two-passage channel to account for variations in the bulk temperature used as a reference for the transient TLC technique. Results showed that the normalized distribution of the temperature field was time-invariant, an important result for the validation of heat transfer results using the transient TLC method. The normalized fluid temperature field was shown to be independent of the inlet temperature step and relatively independent of channel Reynolds number. Fluid temperature distributions were shown to be consistent over the length of the inlet channel, however, temperature field measurements made downstream of the bend exhibited a strong asymmetry. Finally, local temperature distributions were used to adjust the reference temperature used in calculating heat transfer coefficient distributions and to show the behavior of heat transfer due to 180° bends.

scholarly journals A computational modeling on transient heat and fluid flow through a curved duct of large aspect ratio with centrifugal instability

2021 ◽  
Vol 136 (4) ◽  
Author(s):  
Shamsun Naher Dolon ◽  
Mohammad Sanjeed Hasan ◽  
Giulio Lorenzini ◽  
Rabindra Nath Mondal
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Aspect Ratio ◽  
Computational Modeling ◽  
Flow Velocity ◽  
Numerical Technique ◽  
Large Aspect Ratio ◽  
Duct Flow ◽  
Curved Duct ◽  
Centrifugal Instability

AbstractDue to remarkable applications of the curved ducts in engineering fields, scientists have paid much attention to invent new characteristics of curved-duct flow in mechanical systems. In the ongoing study, a computational modeling of fluid flow and energy distribution through a curved rectangular duct of large aspect ratio is presented. Governing equations are enumerated by using a spectral-based numerical technique together with the function expansion and collocation method. The main purpose of the paper is to analyze the effect of centrifugal force in the flow transition as well as heat transfer in the fluid. The investigations are performed for the aspect ratio, Ar = 4; the curvature ratio, $$\delta = 0.5$$ δ = 0.5 ; the Grashof number, $${\text{Gr}} = 1000$$ Gr = 1000 ; and varying the Dean number, $$0 < {\text{Dn}} \le 1000.$$ 0 < Dn ≤ 1000 . It is found that various types of flow regimes including steady-state and irregular oscillations occur as Dn is increased. To well understand the characteristics of the flow phase spaces and power spectrum of the solutions are performed. Next, pattern variations of axial and secondary flow velocity with isotherms are illustrated for different Dn’s. It is revealed that the flow velocity and the isotherms are significantly influenced by the duct curvature and the aspect ratio. Convective heat transfer and temperature gradients are calculated which explores that the fluids are diversified due to centrifugal instability, and as a consequence the overall heat transfer is enhanced significantly in the curved duct.

Numerical Modeling of Turbulent Heat Transfer and Fluid Flow in a Tunnel Pasteurization Process

1999 ◽  
Author(s):  
Y. H. Zheng ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Cold Water ◽  
Hot Water ◽  
Turbulent Heat Transfer ◽  
Parameter Method ◽  
Turbulent Heat ◽  
Water Tank ◽  
Lumped Parameter

Abstract The purpose of this study is to model the heat transfer and fluid flow in a tunnel pasteurizer, which can be used to predict the operation status of the pasteurization process. This modeling is very useful when some changes must be made to the design, operation, or the types of products to be pasteurized. Moreover, the model can be used to provide valuable data for the optimization of the pasteurization design. In the modeling two approaches have been adopted. One is the Lumped Parameter Method (LPM), which is used to model the whole pasteurization system, including pipes, zones and heat exchangers. The other one is the Computational Fluid Dynamics (CFD) technology for calculations of the heat transfer and fluid flow rates in the heat exchanger tank. A steady state model in a tunnel pasteurizer has been developed by using the LPM. The temperatures of the spray water and the products in the pasteurization process were calculated by employing this model. The comparisons showed reasonably good agreements between the predicted results and the experimental data. The pressure variations along the regenerative loops were also calculated. With the CFD technology, the numerical calculations of heat transfer and fluid flow have been performed on the temperature distribution in the cylindrical heat exchanger tank that provides a hot water through the top and a cold water through the bottom of tank. There are two outlets. In the heat exchanger tank, the tube arrays are set along the azimuth direction of the tank. This is a thermally stratified layered water tank that can control the four zones of the water temperatures.

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