Investigation of heat transfer at the critical point of a sphere around which flows a hypersonic flow of carbon dioxide gas

1976 ◽  
Vol 10 (1) ◽  
pp. 102-105 ◽  
Author(s):  
N. A. Afonina ◽  
V. G. Gromov
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Critical Point ◽  
Hypersonic Flow ◽  
Carbon Dioxide Gas

Heat Transfer Performance of Supercritical Carbon Dioxide in Microchannels

2015 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Kun-Chieh Liao
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Pressure Drop ◽  
Critical Point ◽  
Test Section ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Test Results ◽  
Test Conditions ◽  
Critical Carbon Dioxide

This paper provides an experimental investigation of heat transfer performance and pressure drop of supercritical carbon dioxide cooling in microchannel heat exchanger. An extruded flat aluminum tube with 37 parallel channels and each channel of 0.5 mm × 0.5 mm cross section was used as the test section. Super critical carbon dioxide at pressure of 7.5 MPa and inlet temperature varied from 55 to 25 °C was tested. The temperature drops of CO2 cooled inside the test section was controlled at 2, 4 and 8 °C separately for each test to investigate the effect of properties change on the friction and heat transfer performance at various temperature cooling ranges near the critical point. The test results showed that while the test conditions were away from (approximately 5 °C higher or lower) the critical point, both heat transfer and pressure drop performance agreed very well with those predicted by convention correlations. However, while the test conditions near the critical point, the difference between the present test results and the prediction values is very high. From the experiment results of various temperature change range inside the test section, we can find that both heat transfer and pressure drop were strongly affected by the temperature cooling ranges near the critical point. Since there is a drastic peak of the properties change near the critical point, neither fluid properties at the average temperature nor the average properties at the inlet and exit temperatures may appropriately present the actual properties change in the test process. If we use the properties integrated but not averaged from inlet to the exit temperatures, we may obtain the results that agree well with the values predicted by conventional correlations. The heat transfer and pressure drop performance of super critical carbon dioxide are indeed similar to these at normal conditions if its properties were appropriately evaluated.

Paper 8: Heat Transfer from a Wire in the Critical Region

1967 ◽  
Vol 182 (9) ◽  
pp. 52-57 ◽  
Author(s):  
U. Grigull ◽  
E. Abadzic
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Natural Convection ◽  
Critical Point ◽  
Critical Region ◽  
High Speed ◽  
Nucleate Boiling ◽  
Flow Patterns ◽  
Film Boiling ◽  
High Speed Camera

This work deals with experimental results on boiling from a horizontal platinum wire, 0·1 mm in diameter, submerged in saturated liquids as carbon dioxide (CO2) and Freon 13 (CF3Cl) in the critical region. Three discrete regimes without steady transition could be observed: natural convection, nucleate boiling, and film boiling. Near the critical point particular flow patterns appeared in the rising vapour in film boiling: regular bubbles, vapour columns, and vapour hazes with garland-like boundaries. These flow patterns could be simulated in model experiments with liquids and were also photographed with a high-speed camera.

Heat Transfer Performance of Twisted Heat Exchanger for Carbon Dioxide Gas in a Dispersed Power Plant System Using Marine Biomass Resource

2014 ◽  
Author(s):  
Makoto Shibahara
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Renewable Energy ◽  
Heat Exchanger ◽  
Power Plant ◽  
Flow Velocity ◽  
Gas Flow ◽  
Marine Renewable Energy ◽  
Carbon Dioxide Gas ◽  
Marine Biomass

This paper is to propose a basic concept of marine renewable energy power plant system as a dispersed one, which is composed of a marine biomass plantation and a micro gas turbine. In this system, high-efficiency compact heat exchanger becomes necessary for the limit of the marine plant space. The author has already reported about a steady and transient heat transfer process for CO2 flowing over a horizontal plate under wide experimental conditions assuming a plate-type heat exchanger. For the heat transfer enhancement of the heat exchanger, the twisted plates were inserted in the tube and parallel plates. In the experiment, the overall heat transfer coefficients of the heat exchanger for carbon dioxide gas (CO2) are measured to construct a fundamental database for the proposed marine renewable energy system. Moreover, the three-dimensional analysis of the twisted heat exchanger has been conducted using the commercial CFD code, CFD2000. The twisted plate with a thickness of 0.3 mm is inserted in a tube which inner diameter is 7 mm. The gas flow velocities are ranged from 2.5 to 7.18 m/s for the inlet gas temperature of 323K. In the experiment, the overall heat transfer coefficient increases as the gas flow velocity increases. In the numerical simulation, the fluid structure in the tube has been changed caused by the twisted plate. The flow velocity near the twisted plate increases due to the blockage of the flow-pass. The temperature distribution was affected by the helically twisting fluid motion.

Mini-Channel Supercritical CO2 Heat Transfer Measurements for Brayton Cycle Regenerators

2009 ◽  
Author(s):  
Alan Kruizenga ◽  
Mark Anderson ◽  
Michael Corradini
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Critical Point ◽  
Heat Exchangers ◽  
Nuclear Power ◽  
Power Plants ◽  
Effective Length ◽  
Transfer Coefficients ◽  
Capital Costs ◽  
Mini Channels

Recently, it has become increasingly important to improve efficiency and reduce capital costs in nuclear power plants. This prompted significant work in studying advanced Brayton cycles for high temperature energy conversion. A particular improvement in the operation of an advanced carbon dioxide cycle, is the use of compact, highly efficient, diffusion bonded heat exchangers for the recuperators. These heat exchangers operate near the pseudo-critical point of liquid carbon dioxide, making use of the drastic variation of the thermo-physical properties. This paper focuses on the experimental measurements of heat transfer and pressure drop characteristics within mini-channels. Two test section channel geometries are studied: a straight channel and a zig-zag channel. Both configurations are 0.5m in length and constructed out of 316 stainless steel with a series of nine parallel 1.9mm semi-circular channels. The zig-zag configuration has an angle of 115 degrees with an effective length of ∼0.58m. Heat transfer measurements are conducted for varying ranges of inlet temperatures, pressures, and mass flow rates. Local and average heat transfer coefficients near the critical point are determined from measured wall temperatures and calculated local bulk temperatures.

Design and Real Fluid Modelling of Micro-Channel Recuperators for a Nominal 100 MW Class Recuperated Recompression Brayton Cycle Using Supercritical Carbon Dioxide

2015 ◽  
Author(s):  
Joshua Schmitt ◽  
David Amos ◽  
Jayanta Kapat
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Supercritical Carbon Dioxide ◽  
Critical Point ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Micro Channel ◽  
One Dimensional ◽  
Supercritical Carbon

The goal of this study is to design and assess the effectiveness of a micro-channel recuperator using supercritical carbon dioxide as a working fluid. A one-dimensional thermal analysis is performed for a micro-channel recuperator suitable for a Brayton cycle with a nominal 100 MW class turbomachine. The impact of supercritical carbon dioxide properties near the critical point on the thermal performance of the recuperator is studied in detail. The cycle parameters are first obtained from an overall cycle analysis. Two adjacent flow passages with square cross-section in counter-flow configuration are considered for this analysis along with appropriate symmetry. The high pressure of SCO2 is also addressed and the structural stresses on the micro-channel walls are analyzed. Only the axial temperature variations in the hot stream and the cold stream are considered in the one-dimensional analysis. Each channel is discretized in the axial direction. Axial conduction through the wall is included in the energy balance. Of particular interest in this analysis is the variation of transport properties of the CO2 working fluid as thermodynamic conditions approach the critical point. These property variations are provided to the computer code through the REFPROP database. Over the length of the heat exchanger local changes in Reynolds number, Nusselt number, and heat transfer coefficient are charted. From the results of the heat transfer calculations, the log mean temperature difference and heat exchange effectiveness of the heat exchanger is calculated. Using the code to produce multiple results, the optimum heat exchanger design is found. Recommendations on the manufacturing method of a micro-channel recuperator are made.

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