Experimental Investigation on Heat Transfer Characteristics of Smooth Water Wall Tube of an Ultra-Supercritical CFB Boiler

2018 ◽  
Author(s):  
Wenyu Wang ◽  
Ziyu Liang ◽  
Li Wan ◽  
Dan Liu ◽  
Dong Yang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Mass Flux ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Cfb Boiler ◽  
Flow Acceleration ◽  
Transfer Characteristics ◽  
Water Wall Tube

In this study, an experimental investigation was carried out to explore the heat transfer characteristics of the smooth water wall tube of an ultra-supercritical circulating fluidized bed (CFB) boiler. The ranges of the test pressure, mass flux, and heat flux were 23–32 MPa, 550–1200 kg·m−2·s−1, and 200–560 kW·m−2, respectively. The material of the tube used in the test was 12 Gr1MoVg. The diameter and wall thickness were 30 and 5.5 mm, respectively. The length of the test section was 2 m. The effects of the pressure, mass flux, heat flux, buoyancy, and flow acceleration on the heat transfer characteristics were analyzed. The formulas of the heat transfer coefficient were fitted, and the existing classical formula was used to evaluate the experimental data. The mechanism of heat transfer enhancement and deterioration of the tube were also investigated. Results showed that at the area of supercritical pressure, the wall temperature gradually increased with the increase of enthalpy in the pseudo-enthalpy region and sharply increased with the increase of enthalpy in the low-enthalpy region (enthalpy < 1200 kJ kg−1) and high-enthalpy region (enthalpy > 2400 kJ kg−1). This phenomenon indicated that heat transfer enhancement occurs near a pseudo-critical point. The increase of heat flux resulted in rapid heat transfer deterioration. Thereafter, the wall temperature rose immediately. The deterioration was delayed with the increase of mass flux and pressure. The effect of buoyancy and flow acceleration on the heat transfer concentrated on the pseudo-critical temperature of the fluid. Among the five selected heat transfer correlations, the Jackson and Bishop correlations agreed well with the experimental data.

Numerical Investigation of Heat and Mass Flux Effects on Heat Transfer Characteristics of Supercritical Water in an Upward Flow Vertical Tube

2014 ◽  
Vol 592-594 ◽  
pp. 1667-1671
Author(s):  
T. Vinoth ◽  
K. Karuppasamy ◽  
D. Santhosh Kumar ◽  
R. Dhanuskodi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Supercritical Water ◽  
Mass Flux ◽  
Vertical Tube ◽  
Upward Flow ◽  
Heat Transfer Characteristics ◽  
Ansys Fluent ◽  
Transfer Characteristics

In the present work, the heat transfer characteristics of supercritical pressure water are numerically investigated in an upward flow vertical smooth tube. The numerical simulations are carried out by using Ansys-Fluent solver. The objective of the present work is to investigate the effect of heat flux and mass flux on heat transfer characteristics in supercritical water. In order to perform numerical simulation, experimental data of Mokryet al.[2] is considered. Various simulations were carried out for the inlet parameters of temperature 350°C, pressure 240bar; heat flux values ranging from 190 to 884kW/m2and mass flux values ranging from 498 to 1499kg/m2s. Based on the available parameters of heat flux and mass flux, they are segregated as groups with heat flux to mass flux ratios of 0.39 and 0.67. According to computational data, the heat transfer enhancement and heat transfer deterioration phenomenon of supercritical water were analyzed and based on the comparison with experimental data; their occurrence and mechanism were addressed.

An Experimental Study On Cryogenic Spray Quenching of a Circular Metal Disk I. Effects of Mass Flux, Spray Fluid Inlet Subcooling, and Gravity

2021 ◽  
Author(s):  
Jun Dong ◽  
Hao Wang ◽  
Samuel Darr ◽  
Jason Hartwig ◽  
Jacob Chung
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Film Boiling ◽  
Gravitational Acceleration ◽  
Heat Transfer Characteristics ◽  
Spray Cone ◽  
Transfer Characteristics ◽  
Metal Disk

Abstract This is the first part of a two-paper series that reports the design, experimentation, and results of a spray quenching experiment of a circular metal disk in terrestrial gravity conditions. The objective of this experiment is to provide experimental data and corresponding analysis on the heat transfer characteristics and chilldown performance of the cryogenic spray quenching process. In this paper, the presented continuous-flow spray quenching results include the spray-cone angle visualization, spray cooling heat transfer characteristics represented by chilldown curves and boiling curves, gravity effects, and Leidenfrost rewet point temperatures. Additionally, detailed discussion is given on the film boiling heat transfer and rewet temperature in terms of various contributing factors such as gravitational acceleration, spray mass flux, and radial position on the plate. Based on experimental data, empirical correlations for film boiling heat transfer coefficient and rewet temperatures are provided. We expect that, the current terrestrial study would offer invaluable information for the design of a robust in-space cryogenic propellant storage tank spray chilldown system.

Investigation on Heat Transfer Characteristics in the Test Section With Non-Uniform Heat Flux Distribution Under Natural Circulation

2017 ◽  
Author(s):  
Qiang Wang ◽  
Puzhen Gao ◽  
Xianbing Chen ◽  
Zhongyi Wang ◽  
Ying Huang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Test Section ◽  
Flux Distribution ◽  
Natural Circulation ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Natural circulation served as an indispensable part of nuclear, attracted much more attentions in recent years. It does not need a pump to provide power. The operating principle of natural circulation caused its complexity in analysis process. It was still a difficult issue to reveal the law of natural circulation accurately. Many experiments and calculations had to be conducted to study the basic physical regulation. This paper concentrated upon the heat transfer characteristics in the test section with two different types of heat flux distribution. The two types of heating flux distribution in the test section were linear and chopped cosine along axial direction. Based on a natural circulation experimental facility, physical models and mathematic models were established. RELAP5 code was used to calculate the thermal hydraulic state of natural circulation loop. The variation of heat transfer coefficient along flow direction was different. It was tightly related to heat flux. Some relevant experiments were conducted in many different conditions and steady sate experimental data were achieved to verified theoretical calculations. Experimental data, such as water temperature, wall temperature and flow rate were recorded when the system is stable. The heat transfer coefficients were calculated according to the experimental data. The factors that affected the heat transfer characteristics of natural circulation were analyzed by comparing the heat transfer coefficient under different conditions. The heat transfer coefficient was calculated according to the empirical correlations as well. After a series of analysis, the results indicated heat transfer coefficient had an obvious difference, which influenced ability of natural circulation. Comparing with experimental data, the evaluation of different empirical correlations was conducted in two test sections. Some empirical correlations turned out to be suitable for the estimation of heat transfer in experiment facility. The increase of heat flux could enhance heat transfer process in the two test section under low pressure. Average heat transfer coefficient increased with the decrease of inlet subcooling degree. The system pressure effected the heat transfer characteristics of natural circulation as well. The increase of mass flux would promote heat transfer while the level was different. RELAP5 had a great agreement with experimental data in single phase flow. Natural circulation ability was influenced by the position of average heat source center, which was slightly different in the research objects. The research would lend strong empirical support to the guideline of experiment and subsequence study in natural circulation.

scholarly journals Numerical Investigation of Heat Transfer Characteristics of scCO2 Flowing in a Vertically-Upward Tube with High Mass Flux

Entropy ◽  
2022 ◽  
Vol 24 (1) ◽  
pp. 79
Author(s):  
Kaigang Gong ◽  
Bingguo Zhu ◽  
Bin Peng ◽  
Jixiang He
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Supercritical Pressure ◽  
High Mass ◽  
Inlet Temperature ◽  
Wall Region ◽  
Heterogeneous Structure ◽  
Heat Transfer Characteristics ◽  
Flow Acceleration ◽  
Transfer Characteristics

In this work, the heat transfer characteristics of supercritical pressure CO2 in vertical heating tube with 10 mm inner diameter under high mass flux were investigated by using an SST k-ω turbulent model. The influences of inlet temperature, heat flux, mass flux, buoyancy and flow acceleration on the heat transfer of supercritical pressure CO2 were discussed. Our results show that the buoyancy and flow acceleration effect based on single phase fluid assumption fail to explain the current simulation results. Here, supercritical pseudo-boiling theory is introduced to deal with heat transfer of scCO2. ScCO2 is treated to have a heterogeneous structure consisting of vapor-like fluid and liquid-like fluid. A physical model of scCO2 heat transfer in vertical heating tube was established containing a gas-like layer near the wall and a liquid-like fluid layer. Detailed distribution of thermophysical properties and turbulence in radial direction show that scCO2 heat transfer is greatly affected by the thickness of gas-like film, thermal properties of gas-like film and turbulent kinetic energy in the near-wall region. Buoyancy parameters Bu < 10-5, Bu* < 5.6 × 10−7 and flow acceleration parameter Kv < 3 × 10−6 in this paper, which indicate that buoyancy effect and flow acceleration effect has no influence on heat transfer of scCO2 under high mass fluxes. This work successfully explains the heat transfer mechanism of supercritical fluid under high mass flux.

Experimental Study on the Heat Transfer Characteristics of Water in Vertically-Upward Internally-Ribbed Tubes

2013 ◽  
Author(s):  
Qing Zhang ◽  
Huixiong Li ◽  
Weiqiang Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Enhancement ◽  
Mass Velocity ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Geometric Structures ◽  
Nondimensional Parameter ◽  
Transfer Characteristics ◽  
New Type

In the present paper, a systematic study of the heat transfer characteristics of water in a new-type vertically-upward internally-ribbed tube has been carried out experimentally. The ranges of the experimental parameters were as follows: the pressure at the inlet of the test section ranged from 12 to 28 MPa, and the mass velocity was from 400 to 1200 kg/m2s, and the internal wall heat flux varied from 300 to 600 kW/m2. The experimental results showed that no matter at subcritical pressures or at supercritical pressures, with the increase in pressure or heat flux, the heat transfer in the internally ribbed tube was weakened, while with the increase in mass velocity, the heat transfer was improved. A systematic comparison between the heat transfer of water in internally ribbed tubes and that in smooth tubes was made in this paper. It was found that compared with the smooth tube, the internally ribbed tube can effectively enhance the heat transfer at subcritical pressures, and also at supercritical pressures. In this paper, the heat transfer enhancement of the internally ribbed tube was attributed to the enlarged heat transfer area, disturbing effect of ribs and the rotational flow in the internally ribbed tube. On the basis of analysis of the effects of tube geometric structures on heat transfer in internally ribbed tubes, a new nondimensional parameter composed of the geometric parameters of the internally ribbed tube was put forward in the present paper to qualitatively compare the capacity of heat transfer enhancement of internally ribbed tubes with different geometric structures, and this new nondimensional parameter got verified by comparison of experimental data of different internally ribbed tubes from open literatures.

Experimental Study on Heat Transfer to Supercritical CO2 Flowing in Vertical Upward Tube at Medium Mass Flux

2017 ◽  
Author(s):  
Qian Zhang ◽  
Huixiong Li ◽  
Xiangfei Kong ◽  
Jun Zhang ◽  
Xianliang Lei ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Mass Flux ◽  
Temperature Peak ◽  
Buoyancy Effect ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Medium Mass ◽  
The Heat Transfer Coefficient

An experimental study was performed on heat transfer characteristics of supercritical pressure CO2 (SC-CO2) flowing at medium mass flux conditions in a vertically-upward tube of 16 mm inner diameter at the Heat Transfer and Flow test loop of Supercritical CO2 (HTF-SCO2) in Xi’an Jiaotong University. Experimental parameters included the pressure ranging from 7.5 to 10.5 MPa, the mass flux of 400–600 kg/m2s, and the heat flux of 20–100 kW/m2. Based on the experimental data, effects of mass flux, heat flux and operation pressure on heat transfer characteristics of SC-CO2 were thoroughly discussed. With the decrease of mass flux and increase of heat flux, heat transfer characteristics of SC-CO2 becomes worse and worse. The wall temperature rises to high levels with the occurrence of a wall temperature peak and the wall temperature peak also rises remarkably with the decrease in mass flux and increase in heat flux. Especially, effect of pressures on the heat transfer of SC-CO2 was found to be quite different from that previously reported in literature. When the heat flux is low (such as 30 kW/m2), the HTD was diminished with the increase in pressures, but when the heat flux is up to 50 kW/m2, the HTD is surprisingly intensified by the increase of pressure. The buoyancy effect was considered to explain this distinct influence of pressure on the heat transfer of SC-CO2 by employed a non-dimensional parameter Bu. With the increase of pressure, buoyancy effect was diminished owing to the decrease of density difference between fluids near the wall and the center. When heat flux was lower, the Bu was located between 5×10−6 and 10−4, where buoyancy effect impaired heat transfer, so the heat transfer coefficient increased by rising pressure. But when heat flux was larger, the Bu was above 10−4, where buoyancy effect began to enhance heat transfer, as a result, the heat transfer coefficient was reduced by weakened buoyancy effect because of the increase of pressure. (CSPE)

scholarly journals Study on Convective Heat Transfer of Supercritical Nitrogen in a Vertical Tube for Liquid Air Energy Storage

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7773
Author(s):  
Qinghua Yu ◽  
Yuxiang Peng ◽  
Ciprian Constantin Negoescu ◽  
Yi Wang ◽  
Yongliang Li
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Mass Flux ◽  
Radial Profile ◽  
Vertical Tube ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Radial Profiles

The convective heat transfer behavior of supercritical nitrogen (S-N2) has played a significant role in optimizing the design of recently emerging cryogenic cold storage and recovery systems. However, studies on S-N2 heat transfer have been relatively scarce, not to mention that there is a legitimate urge for a robust numerical model to accurately predict and explain S-N2 heat transfer under various working conditions. In this paper, both experimental and numerical studies were conducted for convective heat transfer of S-N2 in a small vertical tube. The results demonstrated that the standard k-ε model performed better for predicting the key heat transfer characteristics of S-N2 than the SST k-ω model. The effects of heat flux and inlet pressure on the heat transfer characteristics under a large mass flux were evaluated. The variation mechanisms of local heat transfer performance were revealed by illustrating radial profiles of thermophysical properties and turbulent parameters of N2. It was found that the local performance variation along the flow direction was mainly determined by the radial profile of specific heat while the variation of the best local performance with the ratio of heat flux to mass flux was mainly determined by the radial profile of turbulent viscosity.

Heat Transfer Characteristics of Downward Facing Hot Horizontal Surfaces Using Mist Jet Impingement

2017 ◽  
Author(s):  
Ashutosh Kumar Yadav ◽  
Parantak Sharma ◽  
Avadhesh Kumar Sharma ◽  
Mayank Modak ◽  
Vishal Nirgude ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Cooling System ◽  
Water Pressure ◽  
Jet Impingement ◽  
Surface Heat ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Impinging jet cooling technique has been widely used extensively in various industrial processes, namely, cooling and drying of films and papers, processing of metals and glasses, cooling of gas turbine blades and most recently cooling of various components of electronic devices. Due to high heat removal rate the jet impingement cooling of the hot surfaces is being used in nuclear industries. During the loss of coolant accidents (LOCA) in nuclear power plant, an emergency core cooling system (ECCS) cool the cluster of clad tubes using consisting of fuel rods. Controlled cooling, as an important procedure of thermal-mechanical control processing technology, is helpful to improve the microstructure and mechanical properties of steel. In industries for heat transfer efficiency and homogeneous cooling performance which usually requires a jet impingement with improved heat transfer capacity and controllability. It provides better cooling in comparison to air. Rapid quenching by water jet, sometimes, may lead to formation of cracks and poor ductility to the quenched surface. Spray and mist jet impingement offers an alternative method to uncontrolled rapid cooling, particularly in steel and electronics industries. Mist jet impingement cooling of downward facing hot surface has not been extensively studied in the literature. The present experimental study analyzes the heat transfer characteristics a 0.15mm thick hot horizontal stainless steel (SS-304) foil using Internal mixing full cone (spray angle 20 deg) mist nozzle from the bottom side. Experiments have been performed for the varied range of water pressure (0.7–4.0 bar) and air pressure (0.4–5.8 bar). The effect of water and air inlet pressures, on the surface heat flux has been examined in this study. The maximum surface heat flux is achieved at stagnation point and is not affected by the change in nozzle to plate distance, Air and Water flow rates.

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