scholarly journals Determination of transient fluid temperature using the inverse method

2014 ◽  
Vol 35 (1) ◽  
pp. 61-76 ◽  
Author(s):  
Magdalena Jaremkiewicz
Keyword(s):  
Inverse Method ◽  
Control Volume ◽  
Steam Pressure ◽  
Transient Temperature ◽  
Feed Water ◽  
Fluid Temperature ◽  
Blow Down ◽  
Steam Header ◽  
Control Volumes ◽  
Cylindrical Element

Abstract This paper proposes an inverse method to obtain accurate measurements of the transient temperature of fluid. A method for unit step and linear rise of temperature is presented. For this purpose, the thermometer housing is modelled as a full cylindrical element (with no inner hole), divided into four control volumes. Using the control volume method, the heat balance equations can be written for each of the nodes for each of the control volumes. Thus, for a known temperature in the middle of the cylindrical element, the distribution of temperature in three nodes and heat flux at the outer surface were obtained. For a known value of the heat transfer coefficient the temperature of the fluid can be calculated using the boundary condition. Additionally, results of experimental research are presented. The research was carried out during the start-up of an experimental installation, which comprises: a steam generator unit, an installation for boiler feed water treatment, a tray-type deaerator, a blow down flashvessel for heat recovery, a steam pressure reduction station, a boiler control system and a steam header made of martensitic high alloy P91 steel. Based on temperature measurements made in the steam header using the inverse method, accurate measurements of the transient temperature of the steam were obtained. The results of the calculations are compared with the real temperature of the steam, which can be determined for a known pressure and enthalpy.

scholarly journals Application of a Two-Stage Steam Jet Injector Unit for Latent Heat Recovery of a Marine Steam Turbine Propulsion Plant

2021 ◽  
Vol 11 (12) ◽  
pp. 5511
Author(s):  
Szymon Grzesiak ◽  
Andrzej Adamkiewicz
Keyword(s):  
Steam Turbine ◽  
Steam Pressure ◽  
Relative Increase ◽  
Parameters Optimization ◽  
Feed Water ◽  
Water Heating ◽  
Two Stage ◽  
Heating Systems ◽  
Heating Steam ◽  
Numerical Research

The paper presents the results of the numerical research of the steam jet injector applications for the regenerative feed water heating systems of marine steam turbine propulsion plants. The analysis shows that the use of a single injector for a single heat exchanger results in a relative increase in the thermal efficiency of the plant by 0.6–0.9%. The analysis also indicates the legitimacy of the usage of multistage feed water heating systems, which would enable the operating parameters optimization of the injectors. The obtained steam pressure up to the value of 1.8 barA allows for the heating of the feed water up to 110 °C. For higher degrees of feed water heating in the heat exchangers, it is necessary to supply heating steam of higher pressure. Therefore, the usage of two-stage steam jet injector units was considered advisable for the analyses.

Identification of three-dimensional transient temperature fields in thick-walled elements using the inverse method

2018 ◽  
Vol 28 (1) ◽  
pp. 138-150 ◽  
Author(s):  
Magdalena Jaremkiewicz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Inverse Method ◽  
Thermal Stresses ◽  
Computing Time ◽  
Transient Temperature ◽  
Content Type ◽  
Inner Surface ◽  
The Heat Transfer Coefficient

Purpose The purpose of this paper is to propose a method of determining the transient temperature of the inner surface of thick-walled elements. The method can be used to determine thermal stresses in pressure elements. Design/methodology/approach An inverse marching method is proposed to determine the transient temperature of the thick-walled element inner surface with high accuracy. Findings Initially, the inverse method was validated computationally. The comparison between the temperatures obtained from the solution for the direct heat conduction problem and the results obtained by means of the proposed inverse method is very satisfactory. Subsequently, the presented method was validated using experimental data. The results obtained from the inverse calculations also gave good results. Originality/value The advantage of the method is the possibility of determining the heat transfer coefficient at a point on the exposed surface based on the local temperature distribution measured on the insulated outer surface. The heat transfer coefficient determined experimentally can be used to calculate thermal stresses in elements with a complex shape. The proposed method can be used in online computer systems to monitor temperature and thermal stresses in thick-walled pressure components because the computing time is very short.

Defining the Thermodynamic Efficiency in a Wave Rotor

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Shining Chan ◽  
Huoxing Liu ◽  
Fei Xing
Keyword(s):  
Gas Turbine ◽  
Control Volume ◽  
Thermodynamic Efficiency ◽  
Wave Rotor ◽  
Wave Rotors ◽  
Compression And Expansion ◽  
Efficiency Estimation ◽  
Parametric Analyses ◽  
Control Volumes ◽  
Thermodynamic Processes

A wave rotor enhances the performance of a gas turbine with its internal compression and expansion, yet the thermodynamic efficiency estimation has been troubling because the efficiency definition is unclear. This paper put forward three new thermodynamic efficiency definitions to overcome the trouble: the adiabatic efficiency, the weighted-pressure mixed efficiency, and the pressure pre-equilibrated efficiency. They were all derived from multistream control volumes. As a consequence, they could correct the efficiency values and make the values for compression and expansion independent. Moreover, the latter two incorporated new models of pre-equilibration inside a control volume, and modified the hypothetical “ideal” thermodynamic processes. Parametric analyses based on practical wave rotor data demonstrated that the trends of those efficiency values reflected the energy losses in wave rotors. Essentially, different thermodynamic efficiency definitions indicated different ideal thermal cycle that an optimal wave rotor can provide for a gas turbine, and they were recommended to application based on that essence.

Numerical prediction of the performance of gas-lubricated spiral groove thrust bearings

1997 ◽  
Vol 211 (2) ◽  
pp. 117-128 ◽  
Author(s):  
Y Yue ◽  
T. A. Stolarski
Keyword(s):  
Control Volume ◽  
Numerical Procedure ◽  
Operating Conditions ◽  
Hydrodynamic Bearings ◽  
Thrust Bearings ◽  
Flow Balance ◽  
Control Volumes ◽  
Volume Method ◽  
Spiral Angle ◽  
Spiral Grooves

The objective of this paper is to develop an accurate numerical procedure for the analysis of nominally flat contacts with spiral grooves lubricated by gases. The numerical procedure, which is based on the control-volume method, enables the solutions of the non-linear Reynolds equation to be obtained without limitation in geometry and operating conditions. Satisfactory flow balance was achieved on the control volumes as well as on the whole boundary and the method was proved to be very accurate. Convergence of the method was quick for any compressibility number. Three types of contact with spiral grooves were analysed. They were hydrodynamic bearings without interior chambers, hydrodynamic bearings with interior chambers and hybrid bearings. The effects of spiral angle, groove geometry (length, depth and width) and compressibility on performances were investigated for all possible designs.

Application and Research of Rotate-Lookup-Summation in Robot Motion

2011 ◽  
Vol 467-469 ◽  
pp. 186-191
Author(s):  
Hao Bin Shi ◽  
Wen Jie Dong
Keyword(s):  
Control Volume ◽  
Dimensional Space ◽  
Control Variable ◽  
Control Process ◽  
Controlling Factors ◽  
Dimensional Control ◽  
Control Factors ◽  
Look Up Table ◽  
New Research ◽  
Control Volumes

How to exercise reasonable motion control on robot becomes a new research focus in robot technology research. This paper proposes the Rotate-Lookup-Summation according to the deficiency of traditional look-up table. This method first confirm the controlling factors P1，P2….Pn that would affect the control volume Z, and then the multi-dimensional control volumes and multi-dimensional control factors would be projected to sub-dimensional space. Finally, the same controlling factors of different sub-dimensional space would be rotated to a single sub-dimensional space and establish a corresponding table. According to the single sub-dimensional space value of the controlling factors, the corresponding control variable could be found in table and eventually complete the control process. Experiments show that the method could ensure the integrity and accuracy of table, reduce the table memory capacitance and lookup time, so as to realize the control of look-up table in micro-device.

scholarly journals Penerapan Dinamika Fluida dalam Perhitungan Kecepatan Aliran dan Perolehan Minyak di Reservoir

2014 ◽  
Vol 5 (2) ◽  
pp. 707
Author(s):  
Dwi Listriana Kusumastuti
Keyword(s):  
Fluid Dynamics ◽  
Fluid Flow ◽  
Flow Velocity ◽  
Oil Recovery ◽  
Control Volume ◽  
Petroleum Industry ◽  
Reservoir Rock ◽  
Curved Pipe ◽  
Fluid Flow Velocity ◽  
Control Volumes

Water, oil and gas inside the earth are stored in the pores of the reservoir rock. In the world of petroleum industry, calculation of volume of the oil that can be recovered from the reservoir is something important to do. This calculation involves the calculation of the velocity of fluid flow by utilizing the principles and formulas provided by the Fluid Dynamics. The formula is usually applied to the fluid flow passing through a well defined control volume, for example: cylinder, curved pipe, straight pipes with different diameters at the input and output, and so forth. However, because of reservoir rock, as the fluid flow medium, has a wide variety of possible forms of the control volumes, hence, calculation of the velocity of the fluid flow is becoming difficult as it would involve calculations of fluid flow velocity for each control volume. This difficulties is mainly caused by the fact that these control volumes, that existed in the rock, cannot be well defined. This paper will describe a method for calculating this fluid flow velocity of the control volume, which consists of a combination of laboratory measurements and the use of some theories in the Fluid Dynamics. This method has been proofed can be used for calculating fluid flow velocity as well as oil recovery in reservoir rocks, with fairly good accuration.

Gradient-Driven Diffusion Using Dual Control Volume Grand Canonical Molecular Dynamics (DCV-GCMD)

1995 ◽  
Vol 408 ◽  
Author(s):  
Frank Van Swol ◽  
Grant S. Heffelfinger
Keyword(s):  
Molecular Dynamics ◽  
Chemical Potential ◽  
Control Volume ◽  
Simulation Method ◽  
Steady State Mode ◽  
Transient Phenomena ◽  
Insertion And Deletion ◽  
Separate Control ◽  
Control Volumes ◽  
Grand Canonical

AbstractRecently we developed a new nonequilibrium molecular simulation method [1] that allows the direct study of interdiffusion in multicomponent mixtures. The method combines stochastic insertion and deletion moves characteristic of grand canonical (GC) simulations with molecular dynamics (MD) to control the chemical potential μi of a species i. Restricting the insertions and deletions to two separate control volumes (CV's) one can apply different μ's in distinct locations, and thus create chemical potential gradients. DCV-GCMD can be used to study transient phenomena such as the filling of micropores or used in steady-state mode to determine the diffusion coefficients in multicomponent fluid mixtures. We report on the effects of molecular interactions and demonstrate how in a sufficiently nonideal ternary mixture this can lead to up-hill or reverse diffusion. In addition we introduce a novel extension of DCV-GCMD that is specifically designed for the study of gradient-driven diffusion of molecules that are simply too large to be inserted and deleted.

A Unified Theory for the Pressure Change of Sudden Expansions and Contractions Based on the Momentum Balance

2021 ◽  
Author(s):  
Sebastian Müller ◽  
Andreas Malcherek
Keyword(s):  
Control Volume ◽  
Pressure Change ◽  
Sudden Expansion ◽  
Momentum Balance ◽  
Unified Approach ◽  
Pressure Distributions ◽  
Analytical Functions ◽  
Specific Geometry ◽  
Control Volumes ◽  
Pressure Changes

Abstract In this paper a unified approach based on the momentum balance is presented, capable of predicting the pressure change of sudden contractions and sudden expansions. The use of empirically determined correction coefficients is not necessary. Therefore, the momentum balance is derived similarly for both applications but with different control volumes. The control volume takes into account the specific geometry of the hydraulic structure. With a properly chosen control volume, the unified approach requires coefficients that account for the velocity as well as pressure distributions on the boundaries of the control volume. These coefficients can be obtained by parameterizing the results of numerical simulations by simple analytical functions. The numerical model itself is validated by checking the simulated pressure change against calculated or measured pressure changes. It is found that the formulation of the momentum balance for the sudden expansion is more complex compared with the sudden contraction. The prediction of the pressure change of flows through sudden expansions can be improved by applying the momentum balance non-idealized. Most of the correction coefficients originate from an inappropriate application of Bernoulli’s energy conservation principle. Consequently, this leads to a gap between theory and experimental results. The proposed unified approach solely contains physical coefficients that are used to substitute integrals by averaged expressions.

Geothermal-Driven Ejector Refrigeration System

2013 ◽  
Author(s):  
Mark Anthony B. Redo ◽  
Menandro S. Berana
Keyword(s):  
Geothermal Energy ◽  
System Analysis ◽  
Control Volume ◽  
Phase Region ◽  
Coefficient Of Performance ◽  
Irreversible Processes ◽  
Fluid Temperature ◽  
Refrigeration System ◽  
Two Phase ◽  
Geothermal Resources

A mathematical model of a heat-driven ejector refrigeration system that uses geothermal energy as the heat source was established. Philippine low-enthalpy geothermal resources were investigated and became the bases in computing for the heat at the generator part of the ejector refrigeration system. Analysis and comparison of the performance of the cycle considering working fluids like ammonia (R717) and R134a as the refrigerants were conducted. The properties of those fluids were based on an available thermodynamic database of various refrigerants. The governing principles and conservation equations for energy, mass and momentum were successively applied to control volume of ejector components. The properties for both fluid and flow were solved iteratively for isentropic and irreversible processes wherein entropy generation and frictional losses were accounted for. This included simulation of flows in two-phase region. Input parameters were set like the generating temperature and condensing temperature. The range of 60 to 100 °C available geothermal fluid temperature could produce 50 to 90°C of generating temperature for the fluid refrigerant. This range of generating temperature yielded an evaporating temperature of 8 to 25 °C at a fixed condensing temperature of 40 °C. After numerical analyses, the determined coefficient of performance was at the range of 0.21 to 0.39, while nozzle and ejector efficiencies were from 94% to 99%. The geometric profiles of the ejector were also projected along with the varying generating temperature for both fluids. From the calculation, ammonia offers higher performance and efficiencies and lower evaporating temperatures suitable for larger cooling needs.

An Extended Three-Control-Volume Theory for Circumferentially-Grooved Liquid Seals

1996 ◽  
Vol 118 (2) ◽  
pp. 276-285 ◽  
Author(s):  
O. R. Marquette ◽  
D. W. Childs
Keyword(s):  
Control Volume ◽  
Current Theory ◽  
Flow Section ◽  
Leakage Flow ◽  
Centrifugal Pumps ◽  
Rotordynamic Coefficients ◽  
Stiffness Coefficients ◽  
Through Flow ◽  
Control Volumes ◽  
Theoretical Results

Circumferentially-grooved seals are used in centrifugal pumps to reduce leakage flow. They can also have a significant impact on pump rotordynamic characteristics. Florjancic (1990) developed an analysis for leakage and rotordynamic coefficients, using a partition of the seal into three control volumes. This paper presents a new theory, based on an extension of Florjancic’s work (1990) for circumferentially-grooved liquid seals. The current theory differs from Florjancic’s analysis in the retention of transfer momentum terms and the introduction of diverging flow in the through-flow section within a seal groove. Validation of the new analysis is achieved through a comparison with existing experimental data taken from Kilgore (1988), and Florjancic (1990). Theoretical results are reasonable and consistent; i.e., a modification in the seal parameters induces a correct evolution of the rotordynamic coefficients. Direct and cross-coupled stiffness coefficients are slightly underpredicted, whereas the direct damping coefficient is underpredicted within 40 percent. Leakage flow predictions are very good.

Sign in / Sign up

Export Citation Format

Share Document