Fluid Loop Research Articles

A steady-state simulation model of supplemental cooling system integrated with vapor compression refrigeration cycles for commercial airplane

For predicting the performance of supplemental cooling system (SCS) integrated with vapor compression refrigeration cycles for commercial airplane, a steady-state simulation model for SCS systems was proposed. In the present study, a graph-theory based description model for SCS was developed to describe arbitrary layouts of refrigerant cycles and cooling fluid loop, and a decoding method of the description model was presented to identify the involved components and connection relations for the simulator; the mathematical model for SCS was established by combining the system governing equations and component models, and a tailor-made iteration algorithm using graph-based traversal method was developed to solve the mathematical model. The proposed simulation model for SCS was validated experimentally, and the model deviations of the cooling capacity, temperature and pressure are within 8%, ±8 °C and ±10%, respectively.

Study on the Fluidity Experiments of Engine Oil-Based Magnetic Fluid with Fe3O4/Ag Nanoparticles

In this research, a new engine oil-based Fe3O4/Ag magnetic fluid is prepared applying the method of modified chemical co-precipitation. This preparation method is green without toxic gases being released. The nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibration sample magnetometer (VSM). These characterizations demonstrate that the Fe3O4/Ag nanoparticles modified by oleic acid are successfully synthesized and uniformly dispersed in the engine oil. The hysteresis loop of this new magnetic fluid shows that it has no remnant magnetism and maintains superparamagnetic properties. Shear stress and viscosity of both Fe3O4magnetic fluid and Fe3O4/Ag magnetic fluid are measured by the rotational rheometer. The shear stress increases with the increasing shear rate while the viscosity decreases with the increasing shear rate. What’s more, the viscosity of Fe3O4/Ag magnetic fluid significantly increases compared with the traditional magnetic fluid.

МАЛОИНЕРЦИОННЫЙ ТЕПЛООБМЕННИК АММИАК-АНТИФРИЗ ДЛЯ ИССЛЕДОВАНИЯ ПЕРЕХОДНЫХ ПРОЦЕССОВ В ЭЛЕМЕНТАХ ДВУХФАЗНОЙ СИСТЕМЫ ТЕРМОРЕГУЛИРОВАНИЯ СПУТНИКА

Technical progress entails the use of more powerful equipment on satellites. In connection with the growth of heat generation onboard the spacecraft, the task is to develop thermal control systems based on two-phase mechanically pumped fluid loop (2PMPFL). The advantage of such systems is the ability to transport a greater amount of heat, reduced to a unit of flow, than when using circuits with a single-phase coolant. The study of two-phase thermal control systems in terrestrial conditions is difficult because gravity affects the hydraulics and heat transfer of two-phase flows. Particularly difficult is the study of transients. This article presents the results of tests of a recuperative heat exchanger, which allows to study transient processes in 2PMPFL with high accuracy.It was designed and manufactured the heat exchanger of simple “tube in tube” type design. The thermal characteristics of the heat exchanger were determined on the experimental stand, which is a prototype of a closed-type 2PMPFL with ammonia coolant. Single-phase “liquid” modes, two-phase modes with low mass vapor content (up to 0.04), and single-phase transient modes were investigated. It has been experimentally determined that a heat exchanger under given conditions is capable of removing up to 1323 W of heat in a single-phase mode and up to 1641 W of heat - when operating in a two-phase mode. The data obtained in the course of the experiments allowed us to select the most appropriate known correlation for calculating the stationary characteristics of the heat exchanger with an error not exceeding 5%, which is a high indicator of accuracy for engineering calculations.The heat exchanger has low thermal inertia. The conclusion is relevant for the range of parameters: the ammonia temperature at the inlet is 24...60 ⁰C; antifreeze inlet temperature 5… 16 ⁰C; ammonia mass flow rate 8...17 g / s; mass flow rate of antifreeze 1...4 kg/min.Due to the low thermal inertia of the heat exchanger, it can be used to study transients with the rate of change of the coolant temperature at the inlet up to 1.85 K / min. You can use the stationary method of thermal calculation, i.e. calculate the transient process in the quasi-stationary approximation.

Hyponatremia in Heart Failure: Pathogenesis and Management.

Hyponatremia is a very common electrolyte abnormality, associated with poor short- and long-term outcomes in patients with heart failure (HF). Two opposite processes can result in hyponatremia in this setting: Volume overload with dilutional hypervolemic hyponatremia from congestion, and hypovolemic hyponatremia from excessive use of natriuretics. These two conditions require different therapeutic approaches. While sodium in the form of normal saline can be lifesaving in the second case, the same treatment would exacerbate hyponatremia in the first case. Hypervolemic hyponatremia in HF patients is multifactorial and occurs mainly due to the persistent release of arginine vasopressin (AVP) in the setting of ineffective renal perfusion secondary to low cardiac output. Fluid restriction and loop diuretics remain mainstay treatments for hypervolemic/dilutional hyponatremia in patients with HF. In recent years, a few strategies, such as AVP antagonists (Tolvaptan, Conivaptan, and Lixivaptan), and hypertonic saline in addition to loop diuretics, have been proposed as potentially promising treatment options for this condition. This review aimed to summarize the current literature on pathogenesis and management of hyponatremia in patients with HF.

Why the semicircular canals are not stimulated by linear accelerations

Head accelerations are sensed by the vestibular system in the inner ear. Linear accelerations stimulate the otolith organs, while the semicircular canals (SCC) sense angular accelerations. Fluid–structure interaction (FSI) models of the cupula sensor (simulated with finite element method (FEM)) and the endolymph fluid (simulated with computational fluid dynamics (CFD)) in the semicircular canal offer the possibility to investigate why the SCC are not stimulated by linear accelerations. Two hypotheses exist in the literature. The first hypothesis focusses on the density of the cupula sensor in the SCC, while the second is based on the continuous loop of fluid in the semicircular canal. However, neither increasing the cupula density, nor disrupting the continuous fluid circulation substantially increase the cupula deformation under linear head acceleration, thereby rejecting both existing hypotheses. We propose an alternative hypothesis, based on the circular geometry of the semicircular canal. During angular head acceleration, the cupula intersects the body of endolymph and ‘pushes’ it forward because the cupula seals the semicircular canal like a diaphragm. This results in cupula deflection and neural stimulation. During linear head acceleration, on the other hand, a large part of the canal wall also ‘pushes’ the endolymph forward, which leads to hardly any cupula deflection.

A Thermoelectric-Heat-Pump Employed Active Control Strategy for the Dynamic Cooling Ability Distribution of Liquid Cooling System for the Space Station’s Main Power-Cell-Arrays

A proper operating temperature range and an acceptable temperature uniformity are extremely essential for the efficient and safe operation of the Li-ion battery array, which is an important power source of space stations. The single-phase fluid loop is one of the effective approaches for the thermal management of the battery. Due to the limitation that once the structure of the cold plate (CP) is determined, it is difficult to adjust the cooling ability of different locations of the CP dynamically, this may lead to a large temperature difference of the battery array that is attached to the different locations of the CP. This paper presents a micro-channel CP integrated with a thermoelectric heat pump (THP) in order to achieve the dynamic adjustment of the cooling ability of different locations of the CP. The THP functions to balance the heat transfer within the CP, which transports the heat of the high-temperature region to the low-temperature region by regulating the THP current, where a better temperature uniformity of the CP can be achieved. A lumped-parameter model for the proposed system is established to examine the effects of the thermal load and electric current on the dynamic thermal characteristics. In addition, three different thermal control algorithms (basic PID, fuzzy-PID, and BP-PID) are explored to examine the CP’s temperature uniformity performance by adapting the electric current of the THP. The results demonstrate that the temperature difference of the focused CP can be declined by 1.8 K with the assistance of the THP. The proposed fuzzy-PID controller and BP-PID controller present much better performances than that provided by the basic PID controller in terms of overshoot, response time, and steady state error. Such an innovative arrangement will enhance the CP’s dynamic cooling ability distribution effectively, and thus improve the temperature uniformity and operating reliability of the Li-ion space battery array further.

Influences of mass flow rate on heat and mass transfer performances of water sublimator combined with fluid loop

For spacecraft working in vacuum environment, sublimator is an effective heat rejection approach to reject system’s peak heat load, and supplement spacecraft radiation heat rejection. For a spacecraft active fluid loop thermal control system combined with sublimator, waste heat generated from multi-point distributed heat sources could be collected by the fluid loop efficiently. However, the heat and mass transfer performances of the sublimator combined with fluid loop have not been adequately studied in previous research, especially for the influences of the heat load. Since work fluid mass flow rate is the main factor affecting heat load of the fluid loop, this context experimentally studied influences of the fluid loop mass flow rate on sublimator start-up transient characteristics, including heat transfer performances, response time, and work stability. Results indicated that the fluid loop mass flow rate affected the sublimator heat and mass transfer performances obviously, but the heat rejection ability is not always increase with the increasing of the fluid loop mass flow rate. In addition, we obtained the condition to judge whether there is a positive correlation between heat rejection ability and fluid loop mass flow rate.

Streamlining the Power Generation Profile of Concentrating Solar Power Plants

A scheme to streamline the electric power generation profile of concentrating solar power (CSP) plants of the parabolic trough collector (PTC) type is suggested. The scheme seeks to even out heat transfer rates from the solar field (SF) to the power block (PB) by splitting the typical heat transfer fluid (HTF) loop into two loops using an extra vessel and an extra pump. In the first loop, cold HTF is pumped by the cold pump from the cold vessel to the SF to collect heat before accumulating in the newly introduced hot vessel. In the second loop, hot HTF is pumped by the hot pump from the hot vessel to a heat exchanger train (HXT) to supply the PB with its heat load before accumulating in the cold vessel. The new scheme moderately decouples heat supply from heat sink allowing for more control of heat delivery rates thereby evening out power generation.

Precision Thermal Control Scheme of Fluctuating Temperature for Space Fluid Loop

空间流体回路的载荷支路来流温度在一定范围内随机变化，需采取有效热控措施消除来流温度变化对回路单点位置处恒温工作载荷的热影响.传统电加热方式需要额外能耗并且会产生废热，本文提出一个PID控制下的冷热回路交混控温方案，在充分利用工质吸收的废热、提高机柜内能源利用率的同时，实现对恒温设备冷板入口温度的精确控制，以满足冷板上载荷的恒温工作需求；设计流体回路组成与控制方案，并通过仿真分析对方案进行了验证.结果表明，该流体回路系统可以满足对来流温度的高精度控制要求，且相比于PID控制算法，模糊PID的控制效果更好，具有响应快、超调量小、控制精度高等特点，应优先选择模糊PID作为控制算法.

CFD Simulation Study on Mixing Experiment of Anaerobic Digestion Tank

The anaerobic fermentation produces biogas with the participation of sensitive microorganisms. The smooth fermentation needs to ensure good heat transfer and mass transfer effects. Stirring is very important to create these fermentation conditions. In this paper, the computational fluid dynamics method is used to simulate the flow field inside a fully-mixed stirred anaerobic reactor. It is divided into a single-layer six-leaf open-type turbine with baffles and two-layer four-leaf inclined 45-degree paddles. Group conditions, and quantitative calculation and analysis of the internal flow field of the simulated reactor. The effects of different blades and different stirring speeds are investigated. The results show that the double-layer oblique upward paddle can produce a better axial velocity distribution, which is more conducive to the formation of a large fluid loop structure that circulates up and down. The average speed of double-layer agitation at 125-320 rpm is less than the average speed of a single layer, but the speed of double-layer agitation at 60 rpm is greater than the speed of a single layer.

A hybrid cooling system combining self-adaptive single-phase mechanically pumped fluid loop and gravity-immune two-phase spray module

Although single-phase mechanically pumped fluid loop (MPFL) and two-phase spray cooling technologies have been investigated independently for decades, there is a lack of understanding on the combined operation of these two modules. The MPFL has been extensively utilized in the space thermal control system due to its technological maturity and gravity immunity. The spray cooling, which is characterized by the speciality in thermally dealing with the high heat flux equipment, has not gone that far owing to its complexity in the management of the two-phase flow in the space environment. It is also acknowledged that the MPFL, as an overall cooling strategy in the space thermal control system, will not be replaced completely in the foreseeable future because the primary on-board electronic devices require normal heat dissipation demand and only a few equipment such as on-board laser diode and multi-chip modules demand extreme high heat removal technologies. Therefore, a combination of the MPFL and spray cooling technologies, which constitutes the biggest innovation in this paper, is imperatively needed. A hybrid cooling system (HCS) combining the single-phase self-adaptive MPFL and gravity-immune two-phase spray module which satisfies various cooling demands is proposed in the present study. A validating system as a prototype was established on the basis of the optimal design method. Three test cases were conducted to verify the coordinated operation between the single-phase module and two-phase one and investigate thermal performances of both modules. In all the experiments, the controlled temperature of the cold plate in the MPFL remains within a range between 35.9 °C and 41.9 °C under the heat load from 50 W to 150 W. The highest heat flux acquired by the spray cooling module can be up to 468.8 W/cm2 with the superheat level being 70.0 °C. Results can be drawn that the two modules can be operated simultaneously and independently. Systematic operation efficiency of the proposed HCS is calculated to be 17.7 which displays a high economy of the proposed system.

Modeling and Simulation of Dynamic Heat Dissipation Based on S-Function under MATLAB Simulink Environment

This paper discusses a model implementation of dynamic heat dissipation simulation based on S-Function under MATLAB Simulink Environment. The subtle changes in heat dissipation process can be simulated through this model and the model can be easily used to build thermal control system. A multiloop thermal system, including two payloads and fluid loop system, has been built to test this model. From the simulation results we can analyze the efficiency of heat dissipation in different payload distributions and different flow rate allocations. This model is possibly used for high accuracy temperature control and complex multiloop thermal system analysis.

Multi-plant indirect heat integration based on the Alopex-based evolutionary algorithm

Multi-plant indirect heat integration via an intermediate fluid loop is an effective and energy-saving method of heat recovery. It is most suitable in practical applications because it requires fewer inter-plant pipelines and has the advantages of a simple heat exchanger network. A well-designed heat exchanger network will significantly increase economic efficiency and reduce energy consumption in plants. In this paper, a multi-plant indirect heat exchanger network model is developed for recycling heat using intermediate fluid. This model aims to minimize the total annual cost, including utility cost, number of units and heat transfer area cost. An Alopex-based evolutionary algorithm is used to optimize the model and obtain the heat capacity flow rate of intermediate fluids, the temperature of the heat transfer medium and the configuration of the superstructure simultaneously. Results from three examples demonstrate that the proposed model can perform well in multi-plant heat exchanger network synthesis.

Interventions for chronic non-hypovolaemic hypotonic hyponatraemia.

Interventions for chronic non-hypovolaemic hypotonic hyponatraemia.

Equal split of gas–liquid two-phase flow at variable extraction ratio

In this work, a special distributor is proposed to distribute gas–liquid two-phase flow equally at different extraction ratio. A swirl vane is inserted at the entrance to achieve uniform swirling annular flow and ensure all the splitting holes have identical inlet conditions. A balance pipe is also applied to balance the pressure difference between the sample fluid loop and main fluid loop. Experiments were conducted in an air–water two-phase flow loop. The effect of gas and liquid superficial velocity, inlet flow pattern and splitting hole’s diameter were investigated. The results demonstrate that the extraction ratio is only dependent on the ratio of sample fluid hole number to that of main fluid. The fraction of gas and liquid taken off is not influenced by flow gas and liquid velocity, inlet flow pattern and size of the splitting hole. The desired extraction ratio can be obtained by regulating the number of sample fluid holes.

Ground-source heat pump systems: The effect of variable pipe separation in ground heat exchangers

Closed loop ground-source heat pump (GSHP) systems use ground heat exchangers (GHEs) to transfer heat to and from the ground and efficiently provide clean and renewable energy for heating and cooling purposes. Vertical GHEs contain pipes with circulating fluid (loops), which transfer thermal energy between the ground and the fluid. One very common assumption made in designing GSHP systems is that, when installed, these loops remain evenly separated along the length of the GHE, something that due to the nature of construction is rarely true. This can result in thermal interference not accounted for in the design, leading to a potential negative impact on the performance of the system. This paper investigates the effect of this interference, using detailed numerical simulations to compare different geometries, modelling fixed and variable pipe separations. A comprehensive parametric analysis is conducted to identify some of the most influential design parameters and the potential consequences on running and capital costs. Amongst the key findings of this study is the importance of the borehole filling material, as a highly thermally conductive material can minimise these negative effects from the thermal interference by up to 60%. Moreover, potential increases in drilling (capital) costs of up to 24% are shown, while the potential increases in running costs due to the reduced efficiency were found to be relatively minor.

Experimental study of a small scale organic Rankine cycle waste heat recovery system for a heavy duty diesel engine with focus on the radial inflow turbine expander performance

The purpose of this work is to experimentally evaluate the effect on fuel efficiency of a small scale organic Rankine cycle (ORC) as a waste heat recovery system (WHRS) in a heavy duty diesel engine that operates at steady state conditions. The WHRS consists of two operating loops, namely a thermal oil loop that extracts heat from the engine exhaust gases, and the working fluid loop which is the ORC system. The expansion machine of the ORC system is a radial inflow turbine with a novel back-swept blading that was designed from scratch and manufactured specifically for this WHR application. The engine test conditions include a partial engine load and speed operating point where various operating conditions of the ORC unit were tested and the maximum thermal efficiency of the ORC was defined close to 4.3%. Simultaneously, the maximum generated power was 6.3 kW at 20,000 rpm and pressure ratio of 5.9. The isentropic efficiency reached its peak of 35.2% at 20,000 rpm and 27% at 15,000 rpm. The experimental results were compared with the CFD results using the same off-design conditions, and the results were in good agreement with a maximum deviation of 1.15% in the total efficiency. Last but not least, the engine-WHRS energy balance is also discussed and presented.

Optimization of a radiator for a MPFL system in a GEO satellite

One of the components that used in the satellite thermal control subsystem is the Mechanically Pumped Fluid Loop (MPFL) system; this system mostly used in geosynchronous orbit (GEO) satellites, and can transfer heat from a hot point to a cold point using the fluid which circulated in a closed loop. Heat radiates to the deep space at the cold plate to cool down the fluid temperature. In this research, the radiative heatexchanger (RHX) for a MPFL system is optimized. The genetic algorithm has been used for minimizing the total mass and pressure drop by considering a constant transferred heat rate at the heat exchanger. The optimization has been done in two cases. In case I, two parameters are considered as a goal function, so optimization is performed using NSGA-II method. Results of optimization are shown in the pareto diagram. In case II, the diameter of pipe is considered constant, so the optimized value for distances of the parallel pipes is obtained by using the genetic algorithm, in which the system has the least total mass. Results show that in the RHX, by increasing the pipe diameter, pressure drop decreases and total mass increases. Also by considering a constant value for pipe diameter, an optimum distance between pipes and pipe length are obtained in which the system has a minimum mass.

Managing hyponatremia in lung cancer: latest evidence and clinical implications.

Hyponatremia is the most common electrolyte disorder in lung cancer patients. This condition may be related to many causes including incidental medications, concurrent diseases and side effects of antineoplastic treatments or the disease itself. Although not frequently life-threatening, it is usually associated with prolonged hospitalization, delays in scheduled chemotherapy, worsening of patient performance status and quality of life and may also negatively affect treatment response and survival. Most of the available data focus on thoracic tumors, especially small-cell lung cancer (SCLC), where hyponatremia is frequently related to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Few studies specifically focus on non-small cell lung cancer (NSCLC) patients. Hyponatremia treatment needs to be personalized based on severity and duration of sodium serum reduction, extracellular fluid volume and etiology. However, literature data highlight the importance of early correction of the serum concentration levels. To achieve this the main options are fluid restriction, hypertonic saline, loop diuretics, isotonic saline, tolvaptan and urea. The aim of this review is to analyze the role of hyponatremia in lung cancer patients, evaluating causes, diagnosis, management and clinical implications.

A finite line source simulation model for geothermal systems with series- and parallel-connected boreholes and independent fluid loops

A model for the simulation of geothermal systems with parallel- and series-connected boreholes is presented. Mass and heat balance problems are formulated for each component in the system and are assembled into system-level problems. A third problem is formulated to account for heat transfer in the bore field, using the finite line source solution. This third problem is coupled to the system-level heat balance problem by an analytical solution of the heat transfer inside boreholes with multiple U-tubes. The simulation model allows for any number of independent fluid loops within the bore field or within individual boreholes and allows for combinations of specified inlet fluid temperatures and heat extraction rates in independent fluid loops. The model accounts for the axial variation of the fluid and borehole wall temperatures and heat extraction rates. The capabilities of the model are demonstrated through three example simulations.