Models and Methods of Determining the Minimum Stack Metal Temperature During Sonic Blowdown of Natural Gas

2014 ◽  
Author(s):  
C. Hartloper ◽  
K. K. Botros ◽  
E. Abdalgawad ◽  
S. Reid
Keyword(s):  
Boundary Layer ◽  
Natural Gas ◽  
Wall Temperature ◽  
Steel Grade ◽  
Metal Temperature ◽  
Suitable Model ◽  
Gas Temperature ◽  
Flow Reynolds Number ◽  
Flow Through ◽  
Temperature Recovery

During a natural gas blowdown event, the flow through the blowdown stack is either sonic or supersonic at the stack exit. In this case, the temperature of the gas at the stack exit can drop significantly as the gas enthalpy is converted to kinetic energy. Depending on the initial pipeline temperature, it is possible for the gas temperature at the stack exit to drop below the minimum metal temperature specification of the stack steel grade. Traditionally in this case it is assumed that the blowdown-stack metal temperature follows the gas temperature; therefore, it would also drop below this minimum temperature. However, analogous to the decrease in the temperature of the gas as the velocity increases, the gas will increase in temperature as the velocity decreases near the wall of the stack due to the boundary layer. As such, the blowdown-stack wall temperature will not decrease to the same extent as the bulk gas temperature during the blowdown event. This phenomenon is referred to as wall temperature recovery. This paper describes the various models and methods for determining the extent of this temperature recovery via a parameter known as “recovery factor” which is a function of the flow Reynolds number, Prandtl number, Mach number, etc. These methods are evaluated and compared for several pipeline conditions, and the most suitable model is determined. It is recommended that fundamental blowdown testing on natural gas be conducted on well instrumented full-bore blowdown stack to validate the predictions by these methods.

Paradoxes of Heat Transfer on a Permeable Wall

2010 ◽  
Author(s):  
A. I. Leontiev ◽  
V. G. Lushchik ◽  
A. E. Yakubenko
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Numerical Modeling ◽  
Turbulent Boundary Layer ◽  
Prandtl Number ◽  
Wall Temperature ◽  
Gas Injection ◽  
Gas Mixtures ◽  
Permeable Wall ◽  
Gas Temperature

Numerical modeling of a turbulent boundary layer on a permeable wall with gas injection is performed. New effects are discovered. It is shown in particular that the wall temperature in the region of the gas film may be lower than the injected gas temperature. This effect is especially essential for gas mixtures with low values of the Prandtl number.

Transient Simulation of Natural Gas Citygates Stations

2010 ◽  
Author(s):  
Claudio Veloso Barreto ◽  
Luis F. G. Pires ◽  
Renata C. Sarmento
Keyword(s):  
Natural Gas ◽  
Power Plants ◽  
Gas Flow ◽  
Heating Process ◽  
Gas Temperature ◽  
Minimal Set ◽  
Temperature Loss ◽  
Thermoelectric Power Plants ◽  
Valve Position ◽  
Flow Through

The demand of natural gas in the Brazilian energy market is increasing very fast over the few years and it was necessary to enhance the operational performance and safety of the gas distribution. The perfect operation of the natural gas citygate stations is essential to guarantee the delivery of natural gas for the end users like local distribution companies, thermoelectric power plants and large industrial customers within the contracted marketing conditions. These stations receive natural gas directly from high pressure pipelines and reduce the pressure using regulation valves that provoke a temperature reduction due the Joule-Thompson (JT) behavior, typical of natural gases. This temperature loss is compensated by forcing part of the gas flow through water/glycol bath heaters that use natural gas as fuel in the heating process. Usually the downstream gas temperature condition is controlled above a minimal set point while modifying the three-way valve position that regulates hot and cold streams flows. A numerical tool has been developed to simulate the dynamic process inside the natural gas citygate station, and proved to be a reliable tool to analyze the transient performance of the main equipments (filter, three way valve, heater, JT valve, relief valves) when submitted to abnormal conditions or changes in capacity. The methodology developed is able to handle a variety of citygate design.

Measurements of the Stack Metal Temperature During a Natural Gas Blowdown Event Through a Full-Bore Blowdown Valve

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
C. Hartloper ◽  
K. K. Botros ◽  
J. de Vries
Keyword(s):  
Natural Gas ◽  
Compressible Flow ◽  
Flow Model ◽  
Recovery Factor ◽  
Coefficient Of Determination ◽  
Test Cases ◽  
Measured Temperature ◽  
Gas Temperature ◽  
Empirical Correlations ◽  
Temperature Recovery

Experiments were used in conjunction with a compressible flow model to investigate the temperature recovery phenomenon along a blowdown stack during a high-pressure natural gas pipeline blowdown. The test rig involved instrumented 2 in. blowdown stacks mounted on a full-bore valve. Stacks with two wall thicknesses and stagnation pressures of approximately 3000 kPa-a and 5600 kPa-g were tested, giving a total of four test cases. Using the compressible flow model, which was calibrated using static pressure measurements, the stack-gas temperature was calculated to range from −38 °C to −18 °C for the four test cases. The respective stack wall temperatures were measured to range between −13 °C and 0 °C; thus, the temperature recovery ranged between 18 °C and 26 °C. Empirical correlations available in the literature, which were developed for aeronautical applications, were tested against the experimental results. Poor agreement was found between the measured temperature recovery factor and that predicted by five empirical correlations: the coefficient of determination (R2) between the measured and correlation-calculated recovery factor was found to be negative for all five correlations.

The Effects of Conjugate Heat Transfer on the Thermal Field Above a Film Cooled Wall

2011 ◽  
Author(s):  
Jason E. Dees ◽  
David G. Bogard ◽  
Gustavo A. Ledezma ◽  
Gregory M. Laskowski
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Wall Temperature ◽  
Film Cooling ◽  
Thermal Boundary Layer ◽  
Heat Transfer Analysis ◽  
Gas Temperature ◽  
Adiabatic Wall ◽  
Thermal Fields ◽  
Conducting Wall

Common gas turbine heat transfer analysis methods rely on the assumption that the driving temperature for heat transfer to a film cooled wall can be approximated by the adiabatic wall temperature. This assumption implies that the gas temperature above a film cooled adiabatic wall is representative of the overlying gas temperature on a film cooled conducting wall. This assumption has never been evaluated experimentally. In order for the adiabatic wall temperature as driving temperature for heat transfer assumption to be valid, the developing thermal boundary layer that exists above a conducting wall must not significantly affect the overriding gas temperature. In this paper, thermal fields above conducting and adiabatic walls of identical geometry and at the same experimental conditions were measured. These measurements allow for a direct comparison of the thermal fields above each wall in order to determine the validity of the adiabatic wall temperature as driving temperature for heat transfer assumption. In cases where the film cooling jet was detached, a very clear effect of the developing thermal boundary layer on the gas temperature above the wall was measured. In this case, the temperatures above the wall were clearly not well represented by the adiabatic wall temperature. For cases where the film cooling jet remained attached, differences in the thermal fields above the adiabatic and conducting wall were small, indicating a very thin thermal boundary layer existed beneath the coolant jet.

Laminarization of a Turbulent Boundary Layer in Nozzle Flow—Boundary Layer and Heat Transfer Measurements With Wall Cooling

1970 ◽  
Vol 92 (3) ◽  
pp. 333-344 ◽  
Author(s):  
L. H. Back ◽  
R. F. Cuffel ◽  
P. F. Massier
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Nozzle Flow ◽  
Conical Nozzle ◽  
Gas Temperature ◽  
Temperature Ratio ◽  
Half Angle ◽  
Flow Through ◽  
Complicated Nature

Boundary layer and heat transfer measurements are presented for flow through a cooled, conical nozzle with a convergent and divergent half-angle of 10 deg for a wall-to-total-gas temperature ratio of about 0.5. A reduction in heat transfer below values typical of a turbulent boundary layer was found when values of the parameter K = (μe/ρeue2) (due/dx) exceeded about 2 to 3 × 10−6. The boundary layer measurements, when viewed in conjunction with the heat transfer measurements, reveal the complicated nature of the flow and thermal behavior and their interrelationship when laminarization occurs.

Lime kiln conversion from coke to natural gas operation – an option in direction of sustainable energy

2020 ◽  
pp. 431-434
Author(s):  
Oliver Arndt
Keyword(s):  
Natural Gas ◽  
New Technology ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Gaseous Fuels ◽  
Lime Kiln ◽  
Lime Kilns ◽  
Co2 Balance ◽  
Exhaust Gas Temperature

This paper deals with the conversion of coke fired lime kilns to gas and the conclusions drawn from the completed projects. The paper presents (1) the decision process associated with the adoption of the new technology, (2) the necessary steps of the conversion, (3) the experiences and issues which occurred during the first campaign, (4) the impacts on the beet sugar factory (i.e. on the CO2 balance and exhaust gas temperature), (5) the long term impressions and capabilities of several campaigns of operation, (6) the details of available technologies and (7) additional benefits that would justify a conversion from coke to natural gas operation on existing lime kilns. (8) Forecast view to develop systems usable for alternative gaseous fuels (e.g. biogas).

Boundary Layer Flashback Limits of Hydrogen-Methane-Air Flames in a Generic Swirl Burner at Gas Turbine Relevant Conditions

2020 ◽  
Author(s):  
Dominik Ebi ◽  
Peter Jansohn
Keyword(s):  
Boundary Layer ◽  
Gas Turbine ◽  
Wall Temperature ◽  
Gas Turbines ◽  
High Speed ◽  
Cooling System ◽  
Atmospheric Conditions ◽  
Preheat Temperature ◽  
Swirl Burner ◽  
Wide Range

Abstract Operating stationary gas turbines on hydrogen-rich fuels offers a pathway to significantly reduce greenhouse gas emissions in the power generation sector. A key challenge in the design of lean-premixed burners, which are flexible in terms of the amount of hydrogen in the fuel across a wide range and still adhere to the required emissions levels, is to prevent flame flashback. However, systematic investigations on flashback at gas turbine relevant conditions to support combustor development are sparse. The current work addresses the need for an improved understanding with an experimental study on boundary layer flashback in a generic swirl burner up to 7.5 bar and 300° C preheat temperature. Methane-hydrogen-air flames with 50 to 85% hydrogen by volume were investigated. High-speed imaging was applied to reveal the flame propagation pathway during flashback events. Flashback limits are reported in terms of the equivalence ratio for a given pressure, preheat temperature, bulk flow velocity and hydrogen content. The wall temperature of the center body along which the flame propagated during flashback events has been controlled by an oil heating/cooling system. This way, the effect any of the control parameters, e.g. pressure, had on the flashback limit was de-coupled from the otherwise inherently associated change in heat load on the wall and thus change in wall temperature. The results show that the preheat temperature has a weaker effect on the flashback propensity than expected. Increasing the pressure from atmospheric conditions to 2.5 bar strongly increases the flashback risk, but hardly affects the flashback limit beyond 2.5 bar.

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