Flow Rate Mode Research Articles

Study on the effect of air–water flow rate ratio of heat source tower on the soil heat storage

As direct contact heat exchanger, heat source tower (HST) can absorb the total heat of air by water, and then inject the heat into soil through ground heat exchanger (GHE) for soil heat storage in non-heating season. To achieve an optimal soil heat storage dynamic performance, the air–water flow rate ratio (AWFRR) of the HST and the operation strategy of the soil heat storage system should be optimized. Based on the proposed soil heat storage system and self-built module of the HST, the effects of AWFRR of the HST on soil heat storage characteristics were simulated and discussed in different operation modes with the TRNSYS software. In mode A, the values of AWFRR are the same during the whole non-heating season. While in mode B, the values of AWFRR are different during the transition season and cooling season. The results show that the soil heat storage capacity increases obviously with the increasing of AWFRR under specific water mass flow rate. About 64 % of the total soil heat storage capacity in the non-heating season comes from the soil heat storage capacity by HST in the cooling season. The coefficient of performance (COP) of the soil heat storage system first increases and then decreases with the increasing of AWFRR, and there is an optimal AWFRR under specific water mass flow rate to obtain the highest COP. The amounts of soil heat storage capacity, energy consumption and COP of mode A and mode B are similar, and mode A can be assumed to be the more suitable operating mode for its simple operation in engineering application. After optimization of mode A, not only the operating time of the system is reduced from 4440 h to 3264 h, but also more soil heat injection, less energy consumption and higher COP are achieved. To meet the needed soil heat storage of the proposed building in Changchun, the AWFRR and water mass flow rate in mode A should be 0.7 and 7.7 kg/s respectively.

Work With Chemical Additives Advances Understanding of Relative Permeability Shifts

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 201520, “Advances in Understanding Relative Permeability Shifts by Imbibition of Surfactant Solutions Into Tight Plugs,” by Mohammad Yousefi, Lin Yuan, and Hassan Dehghanpour, SPE, University of Alberta, prepared for the 2020 SPE Annual Technical Conference and Exhibition, originally scheduled to be held in Denver, Colorado, 5–7 October. The paper has not been peer reviewed. Various chemical additives have been proposed recently to enhance imbibition oil recovery from tight formations during shut-in periods after hydraulic fracturing operations. In the complete paper, the authors develop and apply a laboratory protocol mimicking leakoff, shut-in, and flowback processes to evaluate the effects of fracturing-fluid additives on oil regained permeability. A conventional coreflooding apparatus is modified to measure oil effective permeability (koeff) before and after the surfactant-imbibition experiments. Methodology Proposed Technique for Measuring Oil Effective Permeability. Despite the simplicity of the steady-state method, measuring permeability of tight rocks with this technique is challenging because of its time-consuming nature and the fact that accurate measurement is necessary of extremely low flow rates corresponding to low injectivity of tight rocks. The authors use a pair of plugs from a well drilled in the Montney formation that is a stratigraphic unit of the Lower Triassic age in the western Canadian sedimentary basin located in British Columbia and Alberta. It is mainly a low-permeability siltstone reservoir. In the modified coreflooding apparatus, the authors reduce the effect of compressibility in order to reduce the duration of the transient period by approximately one order of magnitude. Because monitoring changes in pressure is much easier and more accurate than monitoring flow-rate changes, a constant flow-rate mode is used and pressure is recorded with time. Oil is injected at different constant flow rates (qo), and the inlet pressure is monitored. The stable pressure difference across the plug is recorded for each flow rate. After steady-state conditions are reached based on the pressure profile, the qo is increased. This process is repeated until four stable pressure differences corresponding to four different qo are obtained. After the highest qo is reached, it is decreased in similar steps to check the repeatability of each data point. The permeability is calculated with the Darcy equation and slope of the qo vs. stable pressure difference across the plug.

Influence of operating conditions of milled peat jet transport on relative sliding of air and solid phases

Air-and-peat mixture in horizontal jet transport pipeline is considered as a compressible two-component mixture with uniform distribution of solid peat particles in continuous air phase. Such heterogeneous medium flow is substituted for a flow of interpenetrating air phase and a quasi-solid phase approximating the flow of discrete particles. Such approach makes it possible to write individual equations of continuity and motion for each phase, but it is required to introduce the forces of aerodynamic interference at the phase boundaries in the motion equations. From the analysis of the known theoretical and experimental research data on jet transport of granular materials, it is possible to identify some parameters such that variation of any of these parameters changes the jet transport energy consumption. Such parameters are: jet capacity per mass of air and solid, Qair and Qs (kg/s) or input-output characteristic of mass concentration, μ = Qs/Qair; reduced velocities of air, Vair, solid particles, Vs, and soaring, Vsn, hereinafter called the flow-rate mode parameters, as well as the size and density of solid particles and the profile of the jet pipeline route. The flow-rate mode parameters are simply registered in the jet transport tests. The numerical determination procedure of the actual operating conditions of milled peat jet transport is justified. The known experimental data on jet transport of milled and treated peat are processed. It is found that the relative sliding ratio is functionally connected with all operating conditions in horizontal jet transport. The change of any parameter or their combination induces transition to air-and-peat mixture flow with various relative sliding of air and solid phases at different energy consumption of horizontal jet transport.

Upgrade of the Taskila WWTP with an MBR line: the first treatment results, performance assessment and lessons learnt

Abstract In this paper, we present the first results of a large-scale membrane bioreactor application implemented for increasing the wastewater treatment plant capacity. The Taskila plant in Finland was upgraded in 2018 and is now operated as a hybrid system with parallel membrane bioreactor and conventional biological lines. The results showed that membrane filtration improved the plant performance significantly in terms of the solids and pathogens removal. Nitrogen removal has been stable with the current operating set-points and notably better than before the plant expansion. The analysis using key performance indicators showed that there were no significant differences in operational expenditures between the membrane and conventional lines. The membrane filtration results highlight the importance of maintaining the good sludge filterability properties that enable higher operational fluxes and reduced energy consumption. The low membrane aeration flow-rate mode, the standard operating mode with good sludge filterability, enabled reduction of total aeration energy consumption by 34% for the membrane bioreactor, including both activated sludge and membrane aeration. Fine-tuning of the hybrid plant is still going on and, therefore, improved overall results are expected in the forthcoming years.

Temperature State of the Last Cascades of Low Pressure Cylinders of Heat Turbines in Low Flow Rate Modes

Operation of high-power turbines during the power grid regulation results in that the last cascades of low pressure section are switched over to the power consumption mode which results in additional energy losses. It is especially related to the heat turbines in which the operation modes are regulated by the rotary regulating orifice in the range of purely condensing flow rate to the flow rate that is actually close to a zero. The modes of power consumption by the last turbine cascades are attributed to low flow rate modes and are in the domain below the mode of idle running of the last cascade. Operation of the cascade with long blades in the domain of low flow-rate modes is accompanied by a high level of ventilation losses, and accordingly by the rise in steam temperature and it significantly affects its density. The suggested paper gives consideration to the approach used for the definition of power inputs in the cascades with low bushing ratio based on the use of Zutter-Traupel formula. A complicated character of a change in the steam temperature in the cascade for the domain of low flow-rate modes required to determine an averaged value of it as a function of the relative volumetric flow rate and correlate it to the steam temperature value measured behind the turbine wheel, based on the analysis of available experimental data. It allowed us to obtain the dependence of a change in the density on the pressure in the capacitor and the temperature measured at the turbine wheel output in the entire range of low flow-rate modes.

General well function for soil vapor extraction

This paper develops a well function applicable to extraction of groundwater or soil vapor from a well under the most common field test conditions. The general well function (Perina and Lee, 2006) [12] is adapted to soil vapor extraction and constant head boundary at the top. For groundwater flow, the general well function now applies to an extraction well of finite diameter with uniform drawdown along the screen, finite-thickness skin, and partially penetrating an unconfined, confined, and leaky aquifer, or an aquifer underneath a reservoir. With a change of arguments, the model applies to soil vapor extraction from a vadose zone with no cover or with leaky cover at the ground surface. The extraction well can operate in specified drawdown (pressure for soil vapor) or specified flowrate mode. Frictional well loss is computed as flow-only dependent component of the drawdown inside the extraction well. In general case, the calculated flow distribution is not proportional to screen length for a multiscreen well.

Lithium technologies for edge plasma control

We have investigated two new modes of operation been in T-10 limiter tokamak experiments with a novel rotary feeder of lithium dust. Quasi steady-state mode I and pulse mode II of dust delivery were realized in both OH and OH+ECRH disruption free plasmas at the lithium flow rate up to 2×1021atoms/s. A higher flow rate in mode II with injection rate of ∼5×1021atoms/s caused a series of minor disruptions, which was completed by discharge termination after the major disruption. The observed decreases of bolometer and Dβ signals, with increase of the electron density during the lithium dust injection, reveal the effects of the first wall conditioning. The lithium technology may provide inherent safety pathway for major disruption mitigation in a tokamak reactor, which requires demonstration in contemporary tokamak experiments.

Transient analysis of a natural circulation solar water heater with a heat exchanger

This paper presents a transient analysis of the performance of a solar water heating system with natural circulation of hot water between the collector and the insulated storage tank. Provision for hot water delivery for domestic/industrial uses has been made through a heat exchanger placed in the storage tank. Explicit expressions for the mean system and water delivery temperature obtained in this paper are simpler and more straightforward than those obtained numerically by Tzafestas using a finite difference method, who also defines an artificial heat transfer coefficient. This paper further investigates the effect of the exchanger length on the performance of the system and may help a designer to properly size the heat exchanger. Numerical calculations have been made for a typical cold day (Jan. 26, 1980) at Delhi for two modes of hot water withdrawal, viz., the constant flow-rate mode and the constant water delivery temperature mode.