Intermediate Pumping Research Articles

Thermal-hydraulic analysis of wetted airside plain fin flat tube heat exchangers and the role of vortex generators

This study addresses the demand for efficient and compact heat exchange solutions in industrial applications. Unlike previous studies that predominantly focused on round tube configurations, this research investigates the impact of vortex generators and geometrical parameters on plain-fin flat-tube designs. Using ANSYS Fluent, the study evaluated the effects of fin geometry, vortex generators, and flow conditions on thermal–hydraulic performance. The key findings revealed that vortex generators enhanced heat transfer by 5–48% by promoting fluid mixing and turbulence but also leading to an increment in friction losses reaching 35–62%, depending upon the number of vortex generators. Condensation rates increased downstream of vortex generators due to enhanced mixing with cooler surfaces. In terms of thermal–hydraulic performance, specific plain-fin configurations outperformed others, offering efficient heat transfer with relatively lower friction losses, even when compactness was considered. Some configurations were recommended for applications where heat exchanger size is less important, but high heat transfer is crucial. Lastly, it was discovered that the effect of vortex generators is more pronounced for lower to intermediate pumping powers per unit area. New empirical correlations were also derived to predict thermal–hydraulic behavior based on geometry and vortex generator placement. A comparison with the literature revealed significantly higher performance as compared to convex/concave vortex generators. Lastly, it was discovered that the effect of vortex generators is more pronounced for lower to intermediate pumping powers per unit area. Empirical correlations for “j” and “f” were correlated with all geometric parameters.

Enhanced harris hawks optimization based load frequency control of multi area microgrid based water treatment plant with consideration of 3DOF-(FO-PIDN)/(TIDN) controller

Municipal water supply system (WSS) consist of different pumping stages viz. intake, water treatment plant (WTP) and intermediate pumping station (IPS). Usually, the power supply for WSS is obtained through public power tapping sources. However, this often leads to load shedding and disruption of the water supply. This paper focuses on the concept, considering WSS as a multi-source multi-area microgrid scheme, this includes renewable energy sources (RES) such as solar, wind, etc. Moreover, the study incorporates a Battery Energy Storage System (BESS) and a Diesel Engine Generator (DEG) to provide power supply during peak demand at each pumping station. Frequency control is essential for optimizing system performance. This paper proposes Enhanced Harris Hawks Optimization Algorithm (EHHO) based PID controller for regulating the frequency in the multi-microgrid-based water supply system. The proposed controller is implemented in MATLAB simulation software, and its response is compared with other optimization methods such as Particle Swarm Optimization (PSO) and Grey Wolf Optimization (GWO). Moreover, implementation and comparison of higher degree order controller such as 3DOF-FOPIDN controller and 3DOF-TIDN controllers are tested under PSO method to observe the performance as well as robustness of the controller. The results indicate that the proposed controller provides better performance in controlling the load frequency deviation, thus improving the efficiency and reliability of the multi-microgrid system for consideration of municipal water supply.

Nonlinear self-action of ultrashort guided exciton–polariton pulses in dielectric slab coupled to 2D semiconductor

Recently reported large values of exciton–polariton nonlinearity of transition metal dichalcogenide (TMD) monolayers coupled to optically resonant structures approach the values characteristic for GaAs-based systems in the regime of strong light-matter coupling. Contrary to the latter, TMD-based polaritonic devices remain operational at ambient conditions and therefore have greater potential for practical nanophotonic applications. Here, we present the study of the nonlinear properties of Ta2O5 slab waveguide coupled to a WSe2 monolayer. We confirm that the hybridization between the waveguide mode and the exciton resonance in WSe2 gives rise to the formation of guided exciton–polaritons with Rabi splitting of 36 meV. By measuring transmission of ultrashort optical pulses through this TMD-based polaritonic waveguide, we demonstrate the strong nonlinear dependence of the output spectrum on the input pulse energy. We develop a theoretical model that shows agreement with the experimental results and gives insights into the dominating microscopic processes which determine the nonlinear pulse self-action: Coulomb exciton–exciton interaction and scattering to an incoherent excitonic reservoir. Based on the numerical simulation of nonlinear phenomena in our polariton system, we conclude that it may support a quasi-stationary solitonic regime of pulse propagation at intermediate pump energies. Our results provide an important step for the development of nonlinear on-chip polaritonic devices based on 2D semiconductors.

On the computation of compressible multiphase flows with heat and mass transfer in elastic pipelines

The present work is motivated by the engineering need to simulate the multiphase flows in the course of the start-up of a long-distance crude oil pipeline. We propose a model for compressible multiphase flows with heat and mass transfer and diffusion processes in elastic pipelines. The model is derived with two approaches, i.e., (a) the spatial averaging procedure of a single phase model and (b) the Arbitrary Lagrangian Eulerian (ALE) formulation of the Baer-Nunziato model with quasi-1D approximation. The diffusion processes include the viscous dissipation, wall friction, heat conduction, and heat exchange with external environment. In particular, the wall friction consists of steady friction term calculated by Darcy-Weisbach formula, and the unsteady friction determined by the instantaneous-acceleration-based (IAB) model. The unsteady friction modifies the characteristic structure of the hyperbolic part of the model. For the solution of the hyperbolic part, we propose a three-wave approximate Riemann solver incorporating the unsteady friction term. Mass and heat transfer are realized via instantaneous relaxations of the chemical potential and temperature, respectively. Efficient iterative relaxation procedures for N-phase flows have been proposed. We have validated the proposed model and numerical methods against some benchmark multiphase problems and applied the model to calculate the start-up of a realistic liquid pipeline with intermediate pump station boundary condition.

Оценка перспективы и технологические особенности строительства магистрального продуктопровода

This article is devoted to the prospects for designing and laying the pipeline system «Komsomolsk Refinery - Vanino Port», the implementation of which will facilitate the export of petroleum products from the Far East regionof the Russian Federation to the countries of the Asia-Pacific region. The article provides an analysis of the characteristics of the construction area, and specifically, the pipeline will run in the southern partof the Khabarovsk Territory, the construction plan was conditionally divided into two parts. This main pipelinehas a high throughput capacity (about 5 million tons/year). In the article, we evaluate the features that should be taken into account when designing a pipeline. In terms of technological features, we describe the route of the pipelinefrom the Komsomolsk Oil Refinery to the port of Vanino, describe in detail the entire route of the pipeline, including river crossings, and also note the construction of an intermediate pumping route for 180 km. The article also discusses structures through water obstacles, railways and highways. The article concludes with a detailed descriptionof a series of actions for cleaning the cavity and testing the pipeline.

Waste Water Treatment Performance of Two Vertical Flow Constructed Wetlands for Agricultural Reuse in Jordan: Enhancing Nitrogen Removal

This study demonstrates the treatment performance of two vertical flow constructed wetlands (VFCWs) for decentralized wastewater treatment plants in Jordan, for reuse purposes to meet the WHO regulations for reuse in agriculture and the Jordanian standards (JS 893/2006). The first system is a recirculating VFCW that has shown high removal efficiency of COD, TSS, and CBOD5 over the study period, conforming to the JS (Category A). Whereas, the Total Nitrogen (TN) and Nitrate (NO3-) removal were limited (55 and 44 mg/L) over the baseline monitoring, conforming to the JS Category-B (TN: 70 mg/L and NO3-N: 45 mg/L). Therefore, the system was modified by converting the recirculation tank into attach growth tank (using electric conduit pipes as plastic media). TN concentration reduced effectively of 40 mg/L, conforming to the JS category-A (TN: 45 mg/L), whereas, NO3–N concentration reduced to 37 mg/L, conforming to the JS Category-B (TN: 45 mg/L). Over the study period, E. coli reduction were constant, 2 log10 reduction, conforming to the JS category C (more than 1000 MPN/100 mL). The second system is two-stage VFCW that has shown high removal efficiency of COD, TSS, and BOD5, conforming to the JS Category-A over the study period. But, TN and NO3–N concentrations were limited (55 and 44 mg/L), conforming to the JS Category-B, due to insufficiency of carbon source to promote denitrification (high BOD5 removal by first filter). Thus, the two-stage VFCW was modified with raw wastewater step-feeding application to the intermediate pump shaft before the second stage filter. The results of operational modification showed a small significant improvement in TN removal (p = 0.005); TN and NO3–N concentrations were reduced to 52 and 50 mg/L, respectively; conforming to the JS Category-B. Higher E. coli removal was observed in the two-stage system than the recirculating system, with an overall average removal of 4.5 log10 units, conforming to the JS category B (less than 2.0 log10 units). While, E. coli reduction influenced negatively by step-feeding modification, conforming to the JS category C

Exergoeconomic assessment of air separation units for pressurized O2 production incorporating two-phase expanders

Cryogenic air separation units (ASU) are the predominant method for delivering high-purity pressurized O2 at large capacities to relevant industrial processes. This study presents an exergoeconomic assessment of the integration of two-phase expanders (TPE) in two ASU configurations with (1) intermediate liquid oxygen pumping followed by gaseous O2 compression and (2) total liquid oxygen pumping to the delivery pressure. A comprehensive exergy analysis showed that TPE integration in the latter resulted in exergy efficiency increase of 1.1%-points and specific power consumption (SPC) reduction 15.5 kWh/ton (−4.4%), while for the former, the exergy efficiency increase amounted to 1.8%-points with 17.9 kWh/ton (−5.2%) lower SPC. A complete thermodynamic mapping for the different cases was presented. From an economic perspective, total liquid pumping reached levelized cost of oxygen reductions of 1.68 €/ton (−4.7%), while in the configuration with gas compressors it was limited to only 0.45 €/ton (−1.2%), relative to analogous ASU configurations with Joule-Thomson valve expansion. The total liquid pumping scheme with TPE presented a cost reduction of 4.3 €/ton (−11.2%) relative to the gaseous O2 compression counterpart. N2 by-product monetization can further improve the plant economic performance. Based on this assessment, integration of reliable TPE technology for incremental efficiency gains of pressurized O2 production in ASUs presents a promising opportunity to profitably contribute to energy efficiency and decarbonization goals.

Trapped ion in an optical cavity: Numerical study of an optomechanical transition in the few-photon regime

We consider an optomechanical system composed by a trapped ion dispersively coupled to a single mode of a pumped optical cavity. We focus in a parameter range for which the semiclassical description predicts two clearly distinct equilibrium configurations in the limits of small and large photon pumping, while a bistable regime is found for intermediate pumping. This semiclassical description, however, is not valid in close proximity of the system transitions or when the mean photon number is low. Here we provide a numerical analysis of the fully quantum state in the few-photon regime, exploring the features of the asymptotic state across the transition and analyzing possible markers of semiclassical bistability. We find an increase in the entropy of the system and of the entanglement in the transition region, but no clear signatures of metastability in the spectrum of the evolution.

A multivalent supply concept: 4th Generation District Heating in Moosburg an der Isar

With regard to the decarbonisation of the heating sector, district heating is of paramount importance considering its potential for the efficient utilisation of renewable energies and waste heat sources. Against this background, the transformation and expansion of an existing heating network in the city of Moosburg an der Isar (Germany) is planned within the “District Heating 4.0” funding programme of the German Federal Office of Economic Affairs and Export Control.The innovative concept involves a heat supply based entirely on renewable energies and industrial waste heat. In particular, the integration of unused waste heat from mechanical and chemical industrial processes enables an ecologically and economically optimal supply concept. Depending on the temperature level, the waste heat is fed into the grid directly or by an intermediate heat pump. In addition, solar thermal systems on roofs are integrated into the grid and optimised in terms of efficiency by using a heat storage. Biomass boilers operated by woodchips of waste wood cover peak loads as well as part of the base load and guarantee the security of supply.Considering the overall system behaviour, the multivalent concept is designed to maximise the share of renewable fuel-free heat sources and capitalise on the beneficial marginal costs of waste heat and solar thermal energy. A profitability analysis shows that low heat generation costs can be realised, not least because of the funding of investment costs. In addition to the technical design process and the economic evaluation, the analysis of legal aspects is a key element of this first phase of the project. In further project phases, the implementation of the heating network, the monitoring of the energy flows and the ongoing acquisition of new customers will be carried out.

МОДЕЛЬ РАСЧЕТА СБОРА И ПЕРЕКАЧКИ ДОЖДЕВЫХ И ТАЛЫХ ВОД ПРИ ПРОЕКТИРОВАНИИ МНОГОФУНКЦИОНАЛЬНЫХ ЗДАНИЙ ОБЩЕСТВЕННОГО И ПРОМЫШЛЕННОГО НАЗНАЧЕНИЙ

In drainage systems, it is often necessary to raise polluted rain and melt water to a low height. For example, pumping wastewater from one gravity collector to another, raising wastewater by several meters in order to reduce the deepening of the collecting sewer collector and, as a result, reduce capital costs for its construction. In such places, it may be more economically feasible to reduce such deepening. The novelty of the study is that the development of a drain can be fulfilled only if the filling of the throughput of the collectors is sufficiently ensured. The study shows that the possibilities of expanding collectors can be achieved based on compensation for energy consumption. The study outlined the necessity of allocating the device of a high-pressure pumping station with the subsequent laying of a pressure sewage collector to a common collector, or to the main sewer network, which in turn supplies rain and melt water to the main collector. The practical significance of the study is the widespread introduction of intermediate pumps of low pressure in sewerage networks is constrained by the lack of a sufficient range of reliable and economical low pressure pumps for contaminated liquids.

Suprasellar cyst after subarachnoid intraventricular hemorrhage and ventriculoperitoneal shunt implantation

The objective is to describe a rare clinical case of a suprasellar cyst formed after implantation of a ventriculoperitoneal shunt. Clinical observation . A female patient, 51 years, suffered non-traumatic subarachnoid intraventricular hemorrhage, acute obstructive and subsequently normal pressure hydrocephalus requiring implantation of a ventriculoperitoneal shunt. In several years, the patient developed a suprasellar cyst manifesting through cerebral symptoms. Results . Two (2) surgeries were performed. During the 1st surgical intervention, endoscopic ventriculostomy was performed with positive outcome (full regression of the symptoms). After 6 months, cyst recurrence was confirmed, and endoscopic ventriculocystocisternostomy with replacement of a low pressure pump with intermediate pressure pump was performed. Full regression of neurological disorders was observed; magnetic resonance imaging did not show cyst recurrence 6 months after the 2 nd surgery. Conclusion . This clinical observation expands our knowledge on the diversity of mechanisms of suprasellar arachnoid cyst formation and demonstrated effectiveness of one of the techniques for prevention of cyst formation in the context of ventriculoperitoneal shunt.

Fluence and wavelength dependent ultrafast differential transmission dynamics in graphene

We performed degenerate pump-probe transmission measurements of graphene supported on glass for a range of pump fluences that enable us to observe both positive and negative deferential transmission dynamics. Our results show that at an intermediate pump fluence, where a transition from negative to positive response occurs, the differential transmission dynamics is an order of magnitude faster than at higher and lower pump fluences. This effect can be explained by equal contributions of inter- and intraband transitions with opposite signs to the transient optical conductivity of graphene at an intermediate pump fluence. Moreover, the intermediate threshold pump fluence is shown to increase with decreasing probe energy, which is in agreement with the theoretical model. Furthermore, we show that the relaxation time of the electronic temperature increases monotonically over the range of fluences studied. In perspective, this work is of importance to graphene-based opto-electronic applications such as light modulators.

Dual-wavelength rectangular pulses in a mode-locked ytterbium-doped fiber laser

We demonstrate dual wavelength rectangular pulses in an ytterbium-doped fiber laser in a simple, all-fiber standing wave cavity configuration. The laser cavity consists of a nonlinear optical loop mirror as a saturable absorber at one end and two fiber Bragg gratings at the other end at wavelengths of 1025 and 1055 nm. There are three distinct regimes of operation in the cavity with an increase in the pump power, one where only 1025 nm wavelength pulses appear, then both 1025 and 1055 nm pulses are supported in the cavity after that, only 1055 nm wavelength pulses are present in the cavity. In the intermediate pumping regime, two sets of pulses are supported in the cavity. These pulses move in the cavity at different speeds and on the cross-over there is no interaction in the pulses. The mode-locked pulses at the 1025 nm wavelength are polarized, whereas pulses corresponding to 1055 nm are nearly unpolarized. Pulses corresponding to both the wavelength bands exhibit a dissipative soliton resonance signature. The laser generates 60 mW total average output power at the maximum pump power of 260 mW at a ∼1.8 MHz repetition rate. The presented cavity mechanism can be utilized to generate various dual- or multi-wavelength mode-locked pulses.

Implementation and operation of anti-pressure systems of oil pipelines

The article analyzes the issue of protection of oil pipelines from high-pressure waves arising from pressure pulsation, water impacts during normal or abnormal shutdown of pumping units or an intermediate pumping station caused by the unauthorized closure of valves, etc. Main aspects of implementation of anti-pressure systems (APS) were considered and economic criteria for their installation on existing and projected oil pipelines were determined. An example of calculation of non-stationary processes required to substantiate the expediency of using high-pressure pumps at intermediate oil pumping stations was presented. The main types of system designs, features of their operation and planned maintenance were presented.

FEATURES OF IMPLEMENTATION AND OPERATION OF PRESSURE WAVES SMOOTHING SYSTEMS IN OIL PIPELINE TRANSPORTATION

Background The scale of PJSC Transneft activities implies a high load and almost uninterrupted operation of the pipeline network. At the same time, during its operation, deviations from the standard modes of transportation, pressure pulsations and hydraulic shocks are possible, the consequences of which can damage equipment or cause damage to the pipe and oil outflow into the environment. A regular or abnormal shutdown of an aggregate or an entire intermediate oil pumping station (OPS) during pumping is accompanied by an increase in pressure, resulting in a steep pressure wave propagating upstream in the direction of the previous station. Due to friction losses, the initial perturbation decays, i.e. its slope and amplitude decrease in absolute value. Reaching the previous station, the increase in pressure wave leads to an increase in pressure at the station outlet. To maintain the setpoint at the LPS outlet, the automatic control system (ACS) of the pressure creates a wave of pressure reduction (vacuum). If the speed of the ACS is not enough to offset the surge pressure, the pressure at the outlet of the pump station can reach the setpoint for the operation of the corresponding station overpressure protection. The action of general station protection comes down to shutting down a single pump or an entire station. When this protection is triggered, a wave of pressure reduction begins to propagate towards the incoming wave of pressure increase downstream. As a result of wave interference, the pressure decreases in the linear part of the pipeline. However, before the wave reaches the previous OPS, the pressure in the section between stations may exceed the allowable working pressure of the pipe sections, which can lead to depressurization of the pipeline. In most cases, in the Transneft system, the protection of line pipes sections from verpressure in transient processes caused by the disconnection of the main pumping unit or the whole pumping station is protected by means of pressure wave smoothing systems. Aims and Objectives The study aim is study of the issues of protection of trunk pipeline facilities from high-pressure waves arising from pressure pulsations, water hammer during normal or abnormal shutdown of pumping units or an intermediate pumping station as a whole, with unauthorized closure of valves, etc. Results The main aspects of the implementation of pressure wave smoothing systems are considered and the economic criteria for their installation on existing and projected oil pipelines are defined. An example is given of the calculation of non-stationary processes necessary to substantiate the expediency of using the high pressure pump at intermediate oil pumping stations. Presents the main types of system designs, features of their operation and planned maintenance.

New graphical methods for estimating aquifer hydraulic parameters using pumping tests with exponentially decreasing rates

AbstractActual pumping tests may involve continuously decreasing rates over a certain period of time, and the hydraulic conductivity (K) and specific storage (Ss) of the tested confined aquifer cannot be interpreted from the classical constant‐rate test model. In this study, we revisit the aquifer drawdown characteristics of a pumping test with an exponentially decreasing rate using the dimensionless analytical solution for such a variable‐rate model. The drawdown may decrease with time for a short period of time at intermediate pumping times for such pumping tests. A larger ratio of initial to final pumping rate and a smaller radial distance of the observation well will enhance the decreasing feature. A larger decay constant results in an earlier decrease, but it weakens the extent of such a decrease. Based on the proposed dimensionless transformation, we have proposed two graphical methods for estimating K and Ss of the tested aquifer. The first is a new type curve method that does not employ the well function as commonly done in standard type curve analysis. Another is a new analytic method that takes advantage of the decreasing features of aquifer drawdown during the intermediate pumping stage. We have demonstrated the applicability and robustness of the two new graphical methods for aquifer characterization through a synthetic pumping test.

Vertical flow constructed wetlands for decentralized wastewater treatment in Jordan: Optimization of total nitrogen removal

The baseline performance of two full-scale vertical flow (VF) constructed wetlands operating in the arid climate of Jordan is presented in this study, within the context of the Jordanian Standards for reuse of treated wastewater. One system was a recirculating VF wetland, and the other was a single-pass two-stage VF wetland. Operational modifications were made to each treatment system, with the aim of improving Total Nitrogen (TN) removal. For the recirculating VF system, attached-growth media was added to the recirculation tank to provide increased surface area for growth of denitrifying bacteria. The modification showed a small but significant improvement in TN removal (8 mg/L less than the baseline phase; p = 0.004). Statistical analysis showed that 30% and 4.5% of the increase in compliance with the TN limits (Class A and Class B/C, respectively) could be attributed to the modification. The two-stage VF wetland was modified with a step-feeding line that introduced carbon-rich raw wastewater to the intermediate pump shaft just upstream of the second-stage filter. The modification also resulted in a small but significant improvement in TN removal (13 mg/L less than the baseline phase; p = 0.005). The increase in compliance with the TN standard due to the modification was estimated at 20% and 22% for Class A and B/C, respectively. The simple operational modifications proved to be effective for improving total nitrogen removal in arid climate VF wetland systems.

Phenomena Identification and Ranking Table (PIRT) study for metallic structural materials for advanced High-Temperature reactor

The Fluoride High-Temperature Reactor (FHR) technology promises many benefits including passive safety, proliferation-resistant waste forms, and improved economics. However, selection of reliable structural materials and identification of the possible degradation mechanisms for these is important for the licensure and the safe operation of FHRs. In order to address this task, the Georgia Tech led Integrated Research Project (IRP) hosted a Phenomena Identification and Ranking Table (PIRT) panel of experts to address degradation mechanisms and other materials related issues of importance to the FHRs. Materials, ones that come in contact with FLiBe or FLiNaK molten salts or other related environments like high temperature steam etc., were considered in this PIRT. Focus of this PIRT was the metallic alloys, especially the ones that are permitted for the construction of elevated temperature Class A components by the ASME code. Degradation mechanisms considered in this PIRT included chemical degradation, mechanical degradation, radiation degradation, and synergistic effect of these mechanisms that may negatively impact operations or cause some safety concerns for the major structural components of FHRs. Main components which were considered included vessel and primary piping, primary heat exchangers, steam generator vessel, steam generator tubes, intermediate loop piping, valves and pumps. Welds in all structural components were identified as an important class of material, which varies in composition and properties, and needs more attention. Importance of impurity control in molten fluorides considered for FHR was highlighted throughout PIRT panel discussions. This paper gives a summary of important results from the PIRT panel discussions and report.

Strength analysis of the intermediate shaft of the hypocycloidal fuel pump

Diesel engines are currently characterized by very high injection pressure. The high pressure allows to achieve better parameters of the fuel atomization process, thus contributing to the improvement of the engine’s ecological parameters. Achieving such a high pressure is possible thanks to the use of reciprocating positive displacement pumps, enabling the fuel pressure to be increased up to 3000 bar. A common feature of currently produced pumps is the drive of the pressing sections through the camshaft, which is lubricated using fuel. For this reason, cam-driven pumps are very sensitive to the quality of the fuel used, and one of its disadvantageous features is also the generation of lateral force on the piston of the section. For this reason, the authors of the article have developed a pump solution, using a hypocycloid drive, in which the disadvantages of traditional cam-driven pumps have been eliminated. The hypocycloid mechanism used has a separate lubrication system, and due to the generated rectilinear motion only the force parallel to the direction of the movement works on the piston. An important problem in the construction of a hypocycloid pump is the high loads of cooperating elements. The intermediate pump shaft is considered to be the most loaded element due to the complex state of stress. The article presents the methodology and results of simulation tests. Stress states have been determined for the position of the shaft in which it takes the highest load. As a result, it was recognized that the pump shaft was designed properly and despite the high force acting on the piston section, it is possible to ensure its long-term and reliable operation.

Unified theory for excited-state, fragmented, and equilibriumlike Bose condensation in pumped photonic many-body systems

We derive a theory for Bose condensation in nonequilibrium steady states of bosonic quantum gases that are coupled both to a thermal heat bath and to a pumped reservoir (or gain medium), while suffering from loss. Such a scenario describes photonic many-body systems such as exciton-polariton gases. Our analysis is based on a set of kinetic equations for a gas of noninteracting bosons. By identifying a dimensionless scaling parameter controlling the boson density, we derive a sharp criterion for which system states become selected to host a macroscopic occupation. We show that with increasing pump power, the system generically undergoes a sequence of nonequilibrum phase transitions. At each transition a state either becomes or ceases to be Bose selected (i.e. to host a condensate): The state which first acquires a condensate when the pumping exceeds a threshold is the one with the largest ratio of pumping to loss. This intuitive behavior resembles simple lasing. In the limit of strong pumping, the coupling to the heat bath becomes dominant so that eventually the ground state is selected, corresponding to equilibrium(-like) Bose condensation. For intermediate pumping strengths, several states become selected giving rise to fragmented nonequilibrium Bose condensation. We compare these predictions to experimental results obtained for excitons polaritons in a double-pillar structure [Phys. Rev. Lett. 108, 126403 (2012)] and find good agreement. Our theory, moreover, predicts that the reservoir occupation is clamped at a constant value whenever the system hosts an odd number of Bose condensates.