Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow

1992 ◽  
Vol 114 (1) ◽  
pp. 46-54 ◽  
Author(s):  
P. J. Vermeulen ◽  
P. Grabinski ◽  
V. Ramesh
Keyword(s):  
Strouhal Number ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Mixing Zone ◽  
Wake Region ◽  
Mixing Processes ◽  
Jet Mixing ◽  
Air Jet ◽  
Percent Increase ◽  
Jet Structure

The mixing of an acoustically pulsed air jet with a confined hot crossflow has been assessed by temperature profile measurements. These novel experiments were designed to examine the effects of acoustic driver power and Strouhal number on jet structure, penetration, and mixing. The results showed that excitation produced strong changes in the measured temperature profiles. This resulted in significant increases in mixing zone size, penetration (at least 100 percent increase), and mixing, and the length to achieve a given mixed state was shortened by at least 70 percent. There was strong modification to the jet-wake region. The increase in jet penetration and mixing was saturating near 90 W, the largest driving power tested. The jet response as determined by penetration and mixing was optimum at a Strouhal number of 0.27. Overall, pulsating the jet flow significantly improved the jet mixing processes in a controllable manner.

Mixing of an Acoustically Excited Air Jet With a Confined Hot Crossflow

1990 ◽  
Author(s):  
P. J. Vermeulen ◽  
P. Grabinski ◽  
V. Ramesh
Keyword(s):  
Strouhal Number ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Mixing Zone ◽  
Wake Region ◽  
Zone Size ◽  
Mixing Processes ◽  
Jet Mixing ◽  
Air Jet ◽  
Jet Structure

The mixing of an acoustically pulsed air jet with a confined hot crossflow has been assessed by temperature profile measurements. These novel experiments were designed to examine the affects of acoustic driver power and Strouhal number on jet structure, penetration and mixing. The results showed that excitation produced strong changes in the measured temperature profiles. This resulted in significant increases in mixing zone size, penetration (at least 100% increase), mixing, and the length to achieve a given mixed state was shortened by at least 70%. There was strong modification to the jet-wake region. The increase in jet penetration and mixing was saturating near 90 W the largest driving power tested. The jet response as determined by penetration and mixing was optimum at a Strouhal number of 0.27. Overall, pulsating the jet flow significantly improved the jet mixing processes in a controllable manner.

NOx Measurements for Combustor With Acoustically Controlled Primary Zone

1997 ◽  
Vol 119 (3) ◽  
pp. 559-565 ◽  
Author(s):  
P. J. Vermeulen ◽  
V. Ramesh
Keyword(s):  
Operating Conditions ◽  
Gas Temperature ◽  
Mixing Processes ◽  
Jet Mixing ◽  
Air Jets ◽  
Air Jet ◽  
A Value ◽  
Primary Zone ◽  
Turbine Design ◽  
Lean Conditions

Successful NOx measurements at the end of the primary zone of a small tubular combustor of conventional gas turbine design, employing acoustically controlled primary zone air-jet mixing processes, have been made at scaled 1/4 and 1/8 load operating conditions. Testing at 1/8 load significantly increased the effective strength of the acoustic drive, which strongly improved the mixing by the acoustically driven primary zone air-jets. The acoustic drive caused partial blockage of the combustor primary zone airflow. This increased the equivalence ratio and the gas temperature, and made the gas temperature distribution more uniform, except for lean conditions at 1/8 load, in the plane of the NOx measurements. This explained the measured greater NOx “with-drive,” and the distinctly more uniform NOx distribution, which confirmed that mixing was acoustically augmented. The acoustically produced changes were greater at 1/8 load. The acoustic drive significantly changed the combustor operating characteristic so far as mean NOx was concerned, and under lean conditions at 1/8 load mean NOx was reduced, indicating that a value of 10 ppm is possible (a 50 percent reduction).

scholarly journals NO x Measurements for Combustor With Acoustically Controlled Primary Zone

1996 ◽  
Author(s):  
Peter J. Vermeulen ◽  
Venkataramanayya Ramesh
Keyword(s):  
Operating Conditions ◽  
Gas Temperature ◽  
Mixing Processes ◽  
Jet Mixing ◽  
Air Jets ◽  
Air Jet ◽  
A Value ◽  
Primary Zone ◽  
Turbine Design ◽  
Lean Conditions

Successful NOx measurements at the end of the primary zone of s small tubular combustor of conventional gas turbine design, employing acoustically controlled primary zone air-jet mixing processes, have been made at scaled 1/4 and 1/5 load operating conditions. Testing at 1/5 load significantly increased the effective strength of the acoustic drive which strongly improved the mixing by the acoustically driven primary zone air-jets. The acoustic drive caused partial blockage of the combustor primary zone air flow. This increased the equivalence ratio and the gas temperature, and made the gas temperature distribution more uniform, except for lean conditions at 1/5 load, in the plane of the NOx, measurements. This explained the measured greater NOx, “with-drive”, and the distinctly more uniform NOx, distribution which confirmed that mixing was acoustically augmented. The acoustically produced changes were greater at 1/5 load. The acoustic drive significantly changed the combustor operating characteristic so far as mean NOx was concerned, and under lean conditions st 1/5 load mean NOx was reduced indicating that a value of 10 ppm is possible (a 50% reduction).

AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

1993 ◽  
Vol 17 (2) ◽  
pp. 145-160
Author(s):  
P.H. Oosthuizen ◽  
A. Sheriff
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Lower Surface ◽  
Local Heat ◽  
Electrical Heating ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Transfer Rates ◽  
Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

scholarly journals Sensors in the Autoclave-Modelling and Implementation of the IoT Steam Sterilization Procedure Counter

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 510
Author(s):  
Lukas Boehler ◽  
Mateusz Daniol ◽  
Ryszard Sroka ◽  
Dominik Osinski ◽  
Anton Keller
Keyword(s):  
The Body ◽  
Surgical Instruments ◽  
Sensor System ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Steam Sterilization ◽  
Automated Evaluation ◽  
Normative Requirements ◽  
Thermal Simulations ◽  
The Relationship

Surgical procedures involve major risks, as pathogens can enter the body unhindered. To prevent this, most surgical instruments and implants are sterilized. However, ensuring that this process is carried out safely and according to the normative requirements is not a trivial task. This study aims to develop a sensor system that can automatically detect successful steam sterilization on the basis of the measured temperature profiles. This can be achieved only when the relationship between the temperature on the surface of the tool and the temperature at the measurement point inside the tool is known. To find this relationship, the thermodynamic model of the system has been developed. Simulated results of thermal simulations were compared with the acquired temperature profiles to verify the correctness of the model. Simulated temperature profiles are in accordance with the measured temperature profiles, thus the developed model can be used in the process of further development of the system as well as for the development of algorithms for automated evaluation of the sterilization process. Although the developed sensor system proved that the detection of sterilization cycles can be automated, further studies that address the possibility of optimization of the system in terms of geometrical dimensions, used materials, and processing algorithms will be of significant importance for the potential commercialization of the presented solution.

Wireless probes for measuring vertical temperature profiles in borehole heat exchangers (BHEs)

2021 ◽  
Author(s):  
Simon Schüppler ◽  
Roman Zorn ◽  
Hagen Steger ◽  
Philipp Blum
Keyword(s):  
Measurement Uncertainty ◽  
Fiber Optics ◽  
Heat Exchangers ◽  
Measurement Errors ◽  
High Reliability ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Distributed Temperature Sensing ◽  
Vertical Temperature ◽  
Borehole Heat Exchangers

<p>The measurement of the undisturbed ground temperature (UGT) serves to design low-temperature geothermal systems, in particular borehole heat exchangers (BHEs), and to monitor shallow aquifers. Wireless and miniaturized probes such as the Geosniff (GS) measurement sphere, which are characterized by an autarkic energy supply and equipped with pressure and temperature sensors, are increasingly being used for the measurement of highly resolved vertical temperature profiles. The measurement probe sinks along the course of the BHE with a selectable measurement frequency to the bottom of the BHE and is useable for initial measurements as well as long term groundwater monitoring. To ensure quality assurance and further improvement of this emerging technology, the analysis of measurement errors and uncertainties of wireless temperature measurements (WTMs) is indispensable. Thus, we provide an empirical laboratory analysis of random, systematic, and dynamic measurement errors, which lead to the measurement uncertainty of WTMs using the GS as a representative device. We subsequently transfer the analysed uncertainty to measured vertical temperature profiles of the undisturbed ground at a BHE site in Karlsruhe, Germany. The precision and accuracy of 0.011 K and -0.11 K, respectively, ensure a high reliability of the GS measurements. The largest measurement uncertainty is obtained within the first five meters of descent resulting from the thermal time constant τ of 4 s. The measured temperature profiles are qualitatively compared with common Distributed Temperature Sensing (DTS) using fiber optic cables and punctual Pt-100 sensors. Wireless probes are also suitable to correct temperature profiles recorded with fiber optics with systematic errors of up to -0.93 K. Various boundary conditions such as the inclination of the BHE pipes or changes of the viscosity and density of the BHE fluid effect the descent rate of the GS of up to 40 %. We additionally provide recommendations for technical implementations of future measurement probes and contribute to an improved understanding and further development of WTMs.</p>

Modeling of Free Vertical Turbulent Diffusion Flames

1991 ◽  
Author(s):  
M. A. Gadalla ◽  
M. A. R. Sharif
Keyword(s):  
Temperature Distribution ◽  
Turbulent Diffusion ◽  
Diffusion Flames ◽  
Turbulent Diffusion Flame ◽  
Jet Mixing ◽  
Turbulent Diffusion Flames ◽  
Air Jet ◽  
Annular Jet ◽  
Fuel Jet ◽  
Model Predictions

Abstract A mathematical/empirical model compatible with the jet mixing theory for predicting the flow field properties, flame envelope, temperature distribution, and flame heights around a free vertical axi-symmetric turbulent diffusion flame has been developed. The model considers the effects of buoyancy force and the relative angle between the reactant jets. The flames are issued from a burner which consists of a central air jet and an annular fuel (commercial butane) jet. The annular jet is issued either vertically or at an angle to the flame axis. Experiments were performed earlier to measure the temperature distribution and concentration of carbon dioxide and oxygen in such flames. Three angular positions of the annular fuel jet and nine burner geometries were investigated. The model predictions in similar configurations are found to be in fair agreement with the experimental data.

Prediction of Confined Coaxial Turbulent Jet Mixing With a Streamwise Differencing Scheme

1991 ◽  
Author(s):  
M. A. R. Sharif ◽  
M. A. Gadalla
Keyword(s):  
Reynolds Stresses ◽  
Low Velocity ◽  
Mean Velocity ◽  
Jet Mixing ◽  
Air Jet ◽  
Air Stream ◽  
Constant Diameter ◽  
Flow Domain ◽  
The Mean ◽  
Secondary Air

Abstract Isothermal turbulent mixing of an axisymmetric primary air jet with a low velocity annular secondary air stream inside a constant diameter cylindrical enclosure is predicted. The flow domain from the inlet to the fully developed downstream locations is considered. The predicted flow field properties include the mean velocity and pressure and the Reynolds stresses. Different velocity and diameter ratios between the primary and the secondary jets have been investigated to characterize the flow in terms of these parameters. A bounded stream-wise differencing scheme is used to minimize numerical diffusion and oscillation errors. Predictions are compared with available experimental data to back up numerical findings.

scholarly journals A Hydrodynamical Model for Calculating the Vertical Temperature Profile in Lakes During Cooling

1983 ◽  
Vol 14 (4) ◽  
pp. 239-254 ◽  
Author(s):  
Jörgen Sahlberg
Keyword(s):  
Heat Flux ◽  
Temperature Profile ◽  
Vertical Mixing ◽  
Hydrodynamical Model ◽  
Measured Temperature ◽  
Vertical Temperature ◽  
Mixing Rate ◽  
Mixing Processes ◽  
Vertical Temperature Profile ◽  
Radiation Fluxes

A one-dimensional hydrodynamical model is used for simulating the vertical temperature profile in a lake during cooling conditions. The vertical mixing rate is calculated by solving the equations for turbulent kinetic energy, k, and dissipation of energy, ε. The heat exchange between the water and atmosphere consists of the radiation fluxes, sensible and latent heat flux. Temperature measurements from Lake Väsman during November-December, 1981, were used in the verification study. The agreement between calculated and measured temperature profiles is very good. This indicates that both the mixing processes and the net heat flux are well described in the model.

INFLUENCE OF CALORIMETRIC MIXING ON THE TEMPERATURE PROFILE WHEN EVALUATING WORKING INTERVALS

2021 ◽  
Author(s):  
Марат Финатович Закиров ◽  
Айрат Шайхуллинович Рамазанов ◽  
Рим Абдуллович Валиуллин ◽  
Рамиль Фаизырович Шарафутдинов
Keyword(s):  
Temperature Profile ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Vertical Wells

В данной работе исследуется профиль термограммы в зависимости от производительности работающих интервалов вертикальной скважины. Установлено, что существуют уникальные профили температур в зависимости от проявления эффекта калориметрического смешивания. Полученные результаты могут быть использованы для анализа экспериментальных профилей температуры с целью выделения работающих интервалов. In this paper, the thermogram profile is studied depending on the performance of the working intervals of the vertical wells. It is established that there are unique temperature profiles depending on the manifestation of calorimetric mixing. The obtained results can be used to analyze measured temperature profiles in order to identify working intervals.

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