Allowable Temperature Difference Research Articles

Adaptability of hydraulic fracturing packers and optimization of their sealing performance for three common clastic rock reservoirs based on finite element analysis

In this paper, the adaptability characteristics of the packer to three types of common clastic rock reservoirs (mudstone, shale, sandstone) are analyzed systematically. Moreover, the identification and structural design of the packer in hydraulic fracturing are systematically conducted based on the finite element calculation. Finally, the nonlinear mathematical models of the packing safety factor and the pressure under the packer and the conditions of casing, mudstone, shale and sandstone are obtained. The results show that the maximum stress of the rubber cylinder in the three formation models of mudstone, shale and sandstone is lower than the compression set strength of the rubber cylinder, indicating that the rubber cylinder will not cause stress damage. At the same time, by analyzing the common rubber materials and constitutive models of the packers, the structure of the packer rubber cylinder and a new anti-shoulder protrusion device were redesigned. The Nitrile-butadiene rubber (NBR) meets the performance requirements of the rubber tube under the allowable pressure difference and temperature difference. The designed new anti-protrusion device can ensure the structural integrity and stress uniformity of the rubber tube, thereby ensuring good sealing performance. Under the three formation conditions of mudstone, shale and sandstone, the rubber cartridge can be in a safe working state, and its sealing width is close to the contact length of the rubber cartridge. In addition, the rubber cartridge is in a good elastic deformation range. The design of the packer in this study satisfies the third strength theory and the safety requirements. The deformation and sealing performance of the rubber cylinder are relatively stable, and the size of the rubber cylinder also meets the field requirements.

Thermal Energy Consumption Assessment in a Fluid Milk Plant

The main energy conservation opportunities in a dairy plant are in refrigeration, and steam generation. This paper aims to identify potential energy and water savings and opportunities to improve the thermal efficiency of a fluid milk processing plant, using energy analysis and Heat Integration methods. Methodologies for energy analysis and Pinch Analysis with the use of HENSAD and Aspen Energy Analyzer are applied. The main specific energy consumptions are defined as indicators of the progress of improved energy efficiency. The determination of energy performance indicators and energy targets of the heat exchanger network, as well as its design, allowed identifying opportunities for improvement to reduce fuel and water consumption through heat recovery in the milk pasteurization process. Current hot and cold utilities duties are satisfied, for a minimum allowable temperature difference of 20 °C. Total annual savings of 60 t of fuel oil and 15,800 m3 of water allow assessing the feasibility of an investment project for improved heat recovery.

A composite superconducting energy pipeline and its characteristics

A superconducting energy pipeline cooled during its clean energy transferring becomes attractive recently to be a promising alternative way for combined green energy transmission to meet the ever-rising energy demand across the world. Though, study on superconducting energy pipelines gets into the conceptual design of single energy integration, the critical multi-composite structure and its characteristics have not yet been systematical. A novel high-temperature superconducting (HTS) energy pipeline integrated with power cable and liquid hydrogen (LH2) and liquefied natural gas (LNG) is proposed in this paper. The maximum allowable temperature difference and pressure drop methods are adopted to design the pipeline. A two-dimensional axisymmetric electromagnetic thermal coupling model has been established using the finite element method. The interface magnetic field formulation, heat transfer modeling, and multiphysics interface has been applied to conduct a detailed analysis of the designed superconducting energy pipeline (LH2-LNG-HTSEP). The results show that the designed LH2-LNG-HTSEP is feasible for practical operation and has more favorite characteristics to suit the HTS cable for the composite pipeline operation. The model and analysis method provide a theoretical base for the composite superconducting energy pipeline design and structural optimization.

Concept Design of 1 GW LH2-LNG-Superconducting Energy Pipeline

A 1 GW LH2-LNG-superconducting energy pipeline has been designed, and the design parameters under the consideration of the maximum allowable temperature difference and pressure drop are verified to achieve high efficiency.

Factorial analysis and experimental study of water-based cooling system effect on the performance of photovoltaic module

A study of the performance of a photovoltaic system with water cooling was carried out experimentally. Three main parameters, namely the water flow rate, the setpoint temperature of the photovoltaic panel, and the maximum allowable temperature difference of the photovoltaic panel, were investigated. In addition, the effect of dust accumulation, in terms of the cleanness factor, ambient temperature, and relative humidity, was studied. An experimental setup was constructed to investigate the cooling effect of water flowing over the panel surface on the performance of a photovoltaic module built at the campus of Jordan University of Science and Technology. Cooling of the photovoltaic module was performed for the period from June to September 2015. The photovoltaic module temperature was controlled to be between 30 and 50 °C, with different levels of water flow rate: high, medium, and low, i.e., 0.9, 0.6, and 0.3 m3/h, respectively. In addition, a statistical factorial analysis of the three-level full factorial design for the experimental data was conducted. It was found that the photovoltaic system performance was higher under water-cooling conditions. The optimum photovoltaic panels cooling temperature was shown to be 37 °C. The designed cooling system achieved an acceptable percentage of excess energy production, i.e., 15.28–17.75%, with minimum water losses. Furthermore, it was found from the statistical analysis that the setpoint temperature of the photovoltaic module had the largest effect on the percentage of excess energy production from photovoltaic, while the effect of maximum allowable temperature difference was negligible.

Heat Exchanger Network Synthesis Considering Different Minimum Approach Temperatures

The minimum approach temperature (?Tmin) has been used in the design of heat exchanger networks (HEN) and in energy targeting based on Pinch Analysis. It refers to the minimum allowable temperature difference between a heat source and a heat sink for designing an energy-efficient HEN. Smaller ?Tmin can improve process heat recovery but require large heat transfer area and may result in a higher capital cost. Capital-energy trade-off is typically performed to determine the cost-optimum ?Tmin during HEN synthesis (HENs). Conventionally, an entire process is analysed to obtain the optimum value of ?Tmin. In this work, the capital-energy trade-off is performed using the individual stream temperature versus enthalpy plot (STEP) to obtain an optimum ?Tmin for each identified STEP. First, simultaneous area and utility targeting of HEN is performed using the established STEP HEN targeting procedure. The capital-energy trade-off is then analysed separately for every identified STEP. The different values of ?Tmin obtained are then applied for the grassroots synthesis of HEN. Application of the proposed procedure on a literature case study shows that the total annualised cost is reduced by 7.03 % when the capital-energy trade-off is performed separately for every STEP as compared to trading-off ?Tmin for an entire process.

Modeling, parametric analysis and optimization of an anode-supported planar solid oxide fuel cell

Solid oxide fuel cell is a promising tool for distributed power generation systems. This type of power system will experience different conditions during its operating life. The present study aims to simulate mathematically a direct internal reforming planar type anode supported solid oxide fuel cell considering mass and energy conservation equations along with a complete electrochemical model. Two main reactions, namely water–gas shift reaction and methane steam reforming reaction, are considered as two dominant reactions occurring in a fuel cell. Such a model may be employed to examine the effect of different operating conditions on main solid oxide fuel cell parameters, such as temperature gradients, power, and efficiency. Furthermore, using such mathematical model, a multi-objective optimization procedure can be applied to determine maximum cell efficiency and output power under constraints such as the allowable temperature difference and limited operating potential. The selected design variables are air ratio, fuel utilization, average current density, steam to carbon ratio, and pre-reforming rate of methane. It has been revealed that any increase in pre-reforming rate of methane and steam to carbon ratio of the entering fuel will lead to efficiency penalty and more uniform temperature distribution along the cell. In addition, the more average current density increases, the less electric efficiency is achieved, and on the other hand, the more temperature difference along the cell is seen. Besides, it is shown that some interesting and important relationships as useful optimal design principles involved in the performance of solid oxide fuel cells can be discovered by Pareto based multi-objective optimization of the mathematically obtained model representing their electric performance. Such important optimal principles would not have been obtained without the use of both mathematical modeling and the Pareto optimization approach.

Conceptual Thermosyphonic Loop Cooled Thermoelectric Power Cogeneration System for Automotive Applications

Thermoelectric cogeneration may be applied to the exhaust of an automobile to generate additional electric power, by applying a temperature differential across the thermoelectric power generation modules. To obtain maximum net power, the highest allowable temperature difference should be obtained. Therefore, a cooling system should be employed to ensure that the cold side of the thermoelectric modules remain as cold as possible. An evaporative cooling system patented by Einstein and Szilard is used as a base for a non-parasitic cooling system to be used together with thermoelectric modules. The cooling system utilizes the same heat which powers the thermoelectric modules as a power source. By utilizing the high solubility of ammonia in water, the solubility dependency with temperature, and usage of polar and non-polar solvents to direct the flow of ammonia as a coolant, it is possible to create a cooling system which performs better than passive heat sinks, but negates the power requirements of active cooling systems.

Design of Steam Cycles for Oxy-combustion Coal based Power Plants with Emphasis on Heat Integration

The Oxy-combustion method of CO2 capture is considered to have several advantages over other methods for CO2 capture from coal based power plants. The capture process is energy intensive and hence expensive. Heat integration is often recommended to recover part of the energy expended in the capture process. In this study, pinch analysis is used as a tool to integrate heat from the CO2 capture process into the steam cycle of the power plant. This way of heat integration provides an opportunity to make better use of the available low grade heat at the power plant premises by approaching the minimum allowable temperature difference between the hot and the cold streams. This ultimately results in a better overall efficiency by generating additional power for the same fuel input and also by reducing the consumption of cooling required in the capture process. The resulting steam cycle will be a custom design for oxy-combustion coal based power plants and will be tightly integrated with the capture process. As this method brings a lot of changes to the steam cycle configuration, this is best suited for new power plants rather than retrofit of existing plants. Results show that the Pinch method of heat integration achieves better overall thermal efficiency compared to the conventional method of steam cycle design and heat integration. A techno-economic is however required to justify the efficiency gains achieved. Further work will be done later to optimize some of the simulation assumptions and to arrive at the network design.

Heat Transfer Simulation of A-Frame Assembly to Support Alcator C-Mod Outer Divertor Upgrade

To design the Alcator C-Mod outer divertor to operate at 600°C and determine its effect on the surrounding vessel and diagnostics, heat transfer analysis must be performed. This paper describes the analysis and the results of heat transfer simulations of the outer divertor tiles, tile-mounting plate, support structure, and current shunt. Using Comsol, commercial FEA software package, a 3D wedge model that exploits the cyclic symmetry of the divertor, is created. By adjusting the power level of each of the 7 heaters used to elevate and control the divertor temperature, a uniform poloidal temperature distribution is achieved and the power requirements for the heaters are determined. The temperature of each component in the assembly is calculated, and results are used for further design changes. Additionally, radiation simulation on thermal shields are presented, which is used as ambient temperature for the heat transfer of the A-frame assembly. Furthermore, a full model of the entire outer divertor ring is presented with its toroidal temperature distribution. Finally, thermal stress of the plate is analyzed besides an analytical calculation of the maximum allowable temperature difference.

Criteria for Heated Band Width Based on Through-thickness Temperature Distribution. Numerical Study on Local PWHT of Butt Welded Pipe. Report 1.

The heated band width is the most important processing parameter for local postweld heat treatment of tubes and pipes.A correct heated band width must be chosen so that the allowable maximum temperature difference in the soak band is maintained and a sufficient degree of stress relaxation is achieved.In this paper, the effects of the geometrical and the thermal parameters in the postweld heat treatment are investigated using axisymmetric FEM.The most severe condition in which the heat input and insulation are only applied to the outside surface of the pipe has been studied in detail. The effect of the geometrical and the thermal parameters on the through thickness temperature gradients is investigated.Through this study, it is found that the required heated band width is mainly influenced by the wall thickness and the heat transfer coefficient on the internal surface.The computed results show that the Hi number is inadequate for practical use under general conditions.A more general Hi number is proposed as a linear function of the thickness. Further, based on the computed results, the authors propose criteria for the heated band width which includes the effect of the geometrical and the thermal parameters.

Analyses of thermal stresses and control schemes for fast temperature ramps of batch furnaces [IC manufacture

This work studies fast temperature ramps of batch furnaces under different control schemes based on thermal and stress analyses. A thermal model is first developed to predict temperature distributions on silicon wafers during ramping processes. Thermoelastic model of stresses is then used to predict the onset of slip-line generation under dynamic conditions. Three control schemes, one based on a maximum allowable within-wafer temperature difference, one with a constant cooling rate, and the third based on the condition for onset of slip generation, are then analyzed. The results show that in order to achieve the highest ramp rates while maintaining defect-free wafer processing, the ultimate criterion for temperature control of the furnaces should be the condition for the onset of defect generation instead of the conventional scheme based on constant ramp rates.

Thermal Characteristics of a Nickel‐Hydrogen Battery

The maximum allowable temperature difference inside a nickel‐hydrogen battery to avoid water relocation was calculated by using a graphical method together with a vapor pressure vs. temperature correlation equation for water vapor over potassium hydroxide solution. An equation was developed for this maximum allowable temperature difference for vessel‐wall temperatures from 0 to 30°C and potassium hydroxide concentrations from 20 to 32%. A heat‐generation equation for the nickel‐hydrogen battery was used to investigate the effect of the location of heat generation on the maximum temperature in the cell and the temperature distribution in the cell.

The optimal spacing of parallel plates cooled by forced convection

This paper reports the optimal board-to-board spacing and maximum total heat transfer rate from a stack of parallel boards cooled by laminar forced convection. The optimal spacing is proportional to the board length raised to the power 1/2, the property group (μα) 1 4 , and (ΔP) − 1 4 , where ΔP is the pressure head maintained across the stack. The maximum total heat transfer rate is proportional to (ΔP) 1 2 , the total thickness of the stack ( H), and the maximum allowable temperature difference between the board and the coolant inlet. Board surfaces with uniform temperature and uniform heat flux are considered. It is shown that the surface thermal condition (uniform temperature vs uniform heat flux) has a minor effect on the optimal spacing and the maximum total heat transfer rate.

Stability of Thermal Convection in a Vertical Porous Layer

Experiments were carried out to study the stability of thermal convection generated in a vertical porous layer by lateral heating in a tall, narrow tank. The porous medium, consisting of glass beads, was saturated with distilled water. It was found that the flow became unstable at a critical ΔT of 29.2°C (critical Rayleigh number of 66.2). Linear stability analysis was applied to study the effects of the Brinkman term and of variable viscosity separately using a quadratic relationship between the density and temperature. It was found that with the Brinkman term, no instability could occur within the allowable temperature difference across the tank. With the effect of variable viscosity included, linear stability theory predicts a critical ΔT of 43.4°C (Rayleigh number of 98.3).