scholarly journals Melting and Heat Transfer Characteristics of Urea Water Solution According to a Heating Module’s Operating Conditions in a Frozen Urea Tank

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8164
Author(s):  
Byeong Gyu Jeong ◽  
Kwang Chul Oh ◽  
Seong Uk Jang
Keyword(s):  
Heat Transfer ◽  
Freezing Point ◽  
Water Solution ◽  
Operating Conditions ◽  
Urea Solution ◽  
Heat Transfer Characteristics ◽  
Frozen Solution ◽  
Transfer Characteristics ◽  
Melting Characteristics ◽  
Scr System

The urea-selective catalytic reduction (SCR) system, a nitrogen oxide reduction device for diesel vehicles, is a catalytic system that uses urea water solution (UWS) as a reducing agent. This system has a relatively wide range of operating temperatures. However, the freezing point of the reducing urea solution used in this system is −11 °C. When the ambient temperature dips below this freezing point in winter, the solution may freeze. Therefore, it is important to understand the melting characteristics of frozen UWS in relation to the operating conditions of the heating device to supply the minimum amount of aqueous solution required by the system in the initial stage of normal operation and startup of the urea–SCR system. In this study, we artificially froze a liquid solution by placing it along with a heating module in an acrylic chamber to simulate a urea solution tank. Two types of heating modules (P120 and P160) consisting of two heating elements and heat transfer bodies were used to melt the frozen solution. The melting characteristics of the frozen solution were observed, for example, changes in the temperature distribution around the heating module and the cross-sectional melting shape with the passage of time since the start of the power supply to the heating module. The shape of melting around the heating module differed depending on the level of UWS relative to the heater inside the urea tank. In case 1, it melted in a wide shape with an open top, and in case 2, it melted in a closed shape. This shape change was attributed to the formation of internal gaseous space due to volume reduction during melting and the heat transfer characteristics of the fluid and solid substances.

Numerical Investigation of Heat Transfer Characteristics of Different Nanoparticles Using Modified Eulerian-Eulerian Model

2020 ◽  
Author(s):  
Muzafar Hussain ◽  
Shahbaz Tahir
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchangers ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Operating Conditions ◽  
Phase Model ◽  
Heat Transfer Characteristics ◽  
Eulerian Model ◽  
Transfer Characteristics

Abstract Nanofluids are widely adopted nowadays to enhance the heat transfer characteristics in the solar applications because of their excellent thermophysical properties. In this paper, a modified Eulerian-Eulerian model recently developed based on experiments was validated numerically to account for the deviations from the experimental data. The modified Eulerian-Eulerian model is compared with the single-phase model, Eulerian-Eulerian models for TiO2-water at different operating conditions and deviation from the experimental data for each of the model was documented. However, the modified Eulerian-Eulerian model gave much closer results when compared to the experimental data. For the further extension of work, the modified Eulerian-Eulerian model was applied to different nanofluids in order to investigate their heat transfer characteristics. Three different nanoparticles were investigated namely Cu, MgO, and Ag and their heat transfer characteristics is calculated based on the modified Eulerian-Eulerian model as well as the single-phase model for the comparison. For lower values of Reynolds numbers, the average heat transfer coefficient was almost identical for both models with small percentage of error but for higher Reynolds numbers, the deviation got larger. Therefore, single-phase model is not appropriate for higher Reynolds numbers and modified Eulerian-Eulerian model should be used to accurately predict the heat transfer characteristics of the nanofluids at higher Reynolds numbers. From the analysis it is found that the Ag-water nanofluid have the highest heat transfer characteristics among others and can be employed in the solar heat exchangers to enhance the heat transfer characteristics and to further improve the efficiency.

Heat Transfer Characteristics of a Radial Jet Reattachment Flame

1997 ◽  
Vol 119 (2) ◽  
pp. 258-264 ◽  
Author(s):  
J. W. Mohr ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Combustion Process ◽  
Local Heat ◽  
Operating Conditions ◽  
Recirculation Region ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Surface

A Radial Jet Reattachment Combustion (RJRC) nozzle forces primary combustion air to exit radially from the combustion nozzle and to mix with gaseous fuel in a highly turbulent recirculation region generated between the combustion nozzle and impingement surface. High convective heat transfer properties and improved fuel/ air mixing characterize this external mixing combustor for use in impingement flame heating processes. To understand the heat transfer characteristics of this new innovative practical RJRC nozzle, statistical design and analysis of experiments was utilized. A regression model was developed which allowed for determination of the total heat transfer to the impingement surface as well as the NOx emission index over a wide variety of operating conditions. In addition, spatially resolved flame temperatures and impingement surface temperature and heat flux profiles enabled determination of the extent of the combustion process with regards to the impingement surface. Specifically, the relative sizes of the reaction envelope, high temperature reaction zone, and low temperature recirculation zone were all determined. At the impingement surface in the reattachment zone very high local heat flux values were measured. This study provides the first detailed local heat transfer characteristics for the RJRC nozzle.

Experimental and Numerical Investigation of Heat Transfer Characteristics of Liquid Flow With Micro-Encapsulated Phase Change Material

2008 ◽  
Author(s):  
Rami Sabbah ◽  
Jamal Yagoobi ◽  
Said Al Hallaj
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Pressure Drop ◽  
Phase Change ◽  
Phase Change Material ◽  
Operating Conditions ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Encapsulated Phase Change Material ◽  
Change Material

This experimental and numerical study investigates Micro-Encapsulated Phase Change Material (MEPCM) heat transfer characteristics and corresponding pressure drop. To conduct this study, an experimental setup consisting of a steel tube with an inner diameter of 4.3mm, outer diameter of 6.5mm and a length of 1,016mm is selected. A MEPCM mass concentration of 20% slurry with particle diameter ranging between 5–15μm is included in this study. Tube wall temperature profile, fluid inlet, outlet temperatures, the pressure drop across the tube are measured and corresponding Nusselt number are determined for various operating conditions. The experimental results are used to validate the numerical model predictions. The numerical model results show good agreement with the experimental data under various operating conditions. The controlling parameters are identified and their effects on the heat transfer characteristics of micro-channels with MEPCM slurries are evaluated.

Air Side Heat Transfer Characteristics of Wavy-Finned-Tube in a Forced Draft Direct Air-Cooled Steam Condenser

2012 ◽  
Vol 516-517 ◽  
pp. 3-8
Author(s):  
Zhao Ying Zhang ◽  
Jian Guo Yang ◽  
Hai Zhen Zhang
Keyword(s):  
Heat Transfer ◽  
Environmental Temperature ◽  
Finned Tube ◽  
Operating Conditions ◽  
Heat Transfer Characteristics ◽  
Power Generating Unit ◽  
Transfer Characteristics ◽  
Actual Operating ◽  
Forced Draft ◽  
Face Velocity

An experimental study was performed on wavy-finned-tube used in forced draft direct air-cooled steam condenser (DACSC) under actual working conditions of the power generating unit. Tests were carried out to study the air side heat transfer characteristics of wavy-finned-tube in actual operating conditions of DACSC, such as: air temperature, air face velocity, environmental temperature, exhaust pressure of steam turbine and temperature of exhaust steam. The air-side heat transfer characteristics of wavy-finned-tube heat exchangers were tested and analyzed by varying air face velocity .One empirical correlations for predicting the h-factor was developed.

Thermal Stability and Heat Transfer Characteristics of Methane and Natural Gas Fuels

1994 ◽  
Author(s):  
Douglas Chin ◽  
James C. Hermanson ◽  
Louis J. Spadaccini
Keyword(s):  
Heat Transfer ◽  
Thermal Stability ◽  
Natural Gas ◽  
High Purity ◽  
Operating Conditions ◽  
Stainless Steel Tube ◽  
Heat Transfer Characteristics ◽  
Hydrocarbon Mixtures ◽  
Transfer Characteristics ◽  
Gas Fuel

The thermal decomposition and heat transfer characteristics of gaseous, high-purity methane, several methane-hydrocarbon mixtures and a typical natural gas fuel were evaluated using an electrically heated, stainless-steel tube test apparatus. Of several candidate heat transfer correlations, the Dittus-Boelter heat transfer correlation provided the best fit of the methane heat transfer data over the range of Reynolds numbers 10,000 to 215,000. The thermal stability (i.e. deposit formation) characteristics of the methane-hydrocarbon mixtures and the natural gas fuel were established and compared with the deposition characteristics of high-purity methane. Testing was conducted at wall temperatures up to 900 K (fuel temperatures to 835 K) for durations of up to 60 hours. Measurements of deposit mass indicated that there was essentially no deposit buildup for wall temperatures below 650 K. Deposit began to form at wall temperatures between 650 K and 775 K. Above 775 K, there was a rapid monotonic increase in deposition. The data suggest that the use of high-purity methane instead of natural gas at temperatures above 775 K could reduce the deposit thickness under similar operating conditions by as much as a factor of three, or permit operation at higher temperatures.

Climate Variables That Influence the Thermal Performance of Horizontal Collector Ground Source Heat Pumps

2006 ◽  
Author(s):  
John Lohan ◽  
Niall Burke ◽  
Michael Greene
Keyword(s):  
Heat Transfer ◽  
Soil Moisture ◽  
Moisture Content ◽  
Heat Pump ◽  
Soil Moisture Content ◽  
Heat Pumps ◽  
Operating Conditions ◽  
Climate Variables ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

The performance characteristics of new heat pumps are usually evaluated under standard test conditions in certified test laboratories prior to their market release. While this data allows potential customers an opportunity to compare different heat pumps under the same conditions it is difficult to assess how variations in operating conditions, particularly around horizontally oriented ground collectors impact on heat pump Coefficient Of Performance (COP). Indeed, harsh winter conditions of continental climates dictate that horizontal collectors are buried sufficiently deep enough to operate in a thermally stable environment, independent of the weather, but this is not as critical in milder maritime climates and shallower collectors that may be influenced by climate are used. This review paper therefore seeks to identify the key climate variables that have been shown to influence the efficiency of horizontal collector heat pump systems. The literature highlights the significant impact of soil moisture content on COP, but the extended relationship between climate, moisture content and COP has not been established. Historical climate data from both a continental and maritime climate is presented and key aspects of their respective weather patterns are compared to assess their capacity to influence soil condition and COP. A series of empirical models linking changes in soil moisture content to fluctuations in soil thermal conductivity, diffusivity and resistance are also presented so that the impact of climate on soil thermal energy content and heat transfer characteristics might be assessed. However, since no one study has experimentally determined the complex relationship between climate, soil heat transfer characteristics and heat pump performance, this paper concludes with an overview of an experimental test facility that allows this relationship to be established for horizontal collector heat pumps in maritime climates.

Heat Transfer Characteristics of Oscillating Heat Pipe With Ethanol as Working Fluid

2009 ◽  
Author(s):  
Haizhen Xian ◽  
Dengying Liu ◽  
Yongping Yang ◽  
Xiaoze Du
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Effective Conductivity ◽  
Heating Temperature ◽  
Operating Conditions ◽  
Working Fluid ◽  
Experimental Investigations ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

In this paper, experimental investigations on the heat transfer characteristics of OHP with ethanol as working fluid were conducted. The experimental results show that there exists a necessary temperature difference between evaporator and condenser section to keep the heat pipe working. The minimum temperature differences for the optimal operating conditions varied from 1.5 to 2.0°C. The maximum effective conductivity achieved could reach up to 111kW/m•°C. The heat pipe was obviously affected by the filling ratio in some cases but the influence law is irregular and related to inclination angles and heating temperatures. Not all OHPs operated well in the limiting case of a zero inclination angle. In most cases, the optimal value of the inclination angle went up when the heating temperature increased. An appropriate high heating temperature is helpful for the OHP to achieved excellent performances. The startup temperature varied from 40°C to 50°C without considering the horizontal heating mode.

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