Feed Water Mass Flow Rate Research Articles

Experimental investigation of a portable desalination unit configured by a thermoelectric cooler

Possible use of a novel portable desalination system was investigated experimentally. The system is based on humidification–dehumidification principle and thermoelectric cooling technique. A thermoelectric cooler was integrated into the system to enhance the process of both humidification and dehumidification. A prototype was fabricated and its performance was tested for various working conditions of the prototype to observe complex relation between psychrometric and thermoelectric phenomena. The effect of feed water mass flow rate and air flow velocity on the COP value of the thermoelectric cooler and clean water production of the system were examined. The maximum daily yield of the system and the COP value of the thermoelectric cooler unit were recorded as 143.6g and 0.78, respectively.

A hybrid solar desalination system of air humidification, dehumidification and water flashing evaporation: Part II. Experimental investigation

This paper describes laboratory experiments with a hybrid solar desalination system consisting of a humidification–dehumidification unit and single stage flashing evaporation unit configured by a (Al2O3/H2O) nano-fluid solar water heater under the climatological conditions of Tanta City, Egypt. The laboratory work has been carried out in actual thermal environment in August 2013. The validation has an emphasis on the main parameters with impact on the water production capacity. These are the solar radiation, feed water mass flow rate, inlet cooling water temperature, mass flow rate of cooling water and nano-particle volume fraction. The main conclusion is that good agreement is obtained between simulated and measured variations of water production and performance ratio values for variations of these parameters. The performance ratio of SSF unit is varied between 0.32 and 1.4 and flashing ranges between 3 and 9°C. The maximum productivity of the system reached 41.8kg/day according to test and operation conditions. The solar water heater efficiency is affected by the nano-particle volume fraction. The humidifier efficiency is affected by increasing water mass flow rate more than the increasing air mass flow rate and reaches about 98%. Finally, collector's efficiencies are about 55% and 56% for solar water heater and solar air heater respectively.

Object-oriented modelling and simulation for the ALFRED dynamics

In this paper, a control-oriented modelling and simulation tool for the study of the Advanced Lead-cooled Fast Reactor European Demonstrator (ALFRED) plant dynamics is presented. It has been developed in order to perform design-basis transient analyses aimed at providing essential feedbacks for the system design finalization. The simulator has been meant to be modular, open and efficient. In this perspective, an object-oriented modelling approach has been adopted, by employing the reliable, tested and well-documented Modelica language. Simulation of core behaviour is based on point kinetics for neutronics and one-dimensional heat transfer models for thermal-hydraulics, coherently with ALFRED specifications. An effort has been spent to model the bayonet-tube Steam Generator (SG) foreseen to be installed within the reactor vessel. The primary loop model has been built by connecting the above-mentioned components (taking into account suitable time delays) and by incorporating the cold pool, which has revealed to be fundamental for an accurate definition of the time constants characteristic of the system because of its large thermal inertia. The description of the overall plant has been finalized by connecting standard turbine, condenser and other components of the balance of plant. Afterwards, the reactor responses to three typical transient initiators have been simulated (i.e., reduction of feedwater mass flow rate, variation of the turbine admission valve coefficient and transient of overpower). Simulation outcomes confirm the strong coupling between core and SG, besides showing the characteristic time constants of the various component responses. Results of the present study constitute a starting point in the definition of plant control strategies, laying the basis for investigation and development of a model-based control-system design.

A Data Reconciliation Based Approach to Accuracy Enhancement of Operational Data in Power Plants

Accuracy of operational data of a power plant is essential for power plant performance monitoring and fault diagnosis. However, due to inevitable occurrence of systematic and measurement errors in the course of obtaining operational data, these errors can only be reduced to a certain level but never be eliminated. In this work, we propose a data reconciliation based approach to reduce the errors of operational data thus enhance the accuracy of the data. The reconciled data can then be used in performance monitoring and fault diagnosis systems to improve their performances. The proposed method is based on more efficient use of redundant data and a first-principle mathematical model of a power plant. Then an optimization process is performed where the weighted least square form of aggregated differences between measured data and their estimated values are minimized. To illustrate the capability of the proposed method, we provide a case study of data reconciliation for feedwater heater heat balance analysis in a 660 MW coal- fired power plant in China. Results show that uncertainty of four key parameters, namely feed water mass flow rate, condensate mass flow rate, deaerator pressure and outlet temperature, can be reduced by 24 %, 30 %, 5 % and 65 %, whilst the uncertainty of other parameters are also reduced to various extent. Moreover, the results also indicate that the proposed approach is effective over a wide range of measured data quality, where quality of some data could be much worse than others and the estimated measurement uncertainties of operational data may not be accurate.

Development of a control-oriented simulator for a LFR demonstrator

In this work, the development of a control-oriented dynamics simulator for a Generation IV Lead-cooled Fast Reactor (LFR) demonstrator has been undertaken aimed at providing a very flexible and straightforward – though accurate – fast-running tool allowing to perform transient design-basis and stability analyses, and laying the foundations for the study of the system control strategy. The simulator, realized in the MATLAB/SIMULINK® environment, is composed of five essential parts: core, steam generator, primary pump, collectors, and coolant cold pool. An analytical lumped-parameter core model has been developed to treat the coupling between neutronics and thermal-hydraulics. For the steam generator a moving boundary approach has been adopted, allowing to get the physical behavior while satisfying the controller specifications, besides assuring coherence with the zero-dimensional core modeling. The complete primary loop model has been assembled by connecting the above-mentioned main subsystems through the hot and cold collectors, and by adding the remaining components blocks. Five different transients have been then simulated to analyze the whole system dynamic behavior in a control-oriented perspective: three scenarios have been initiated by acting on the secondary water side (i.e., enhancement of feedwater mass flow rate and temperature, and turbine admission valve coefficient variation), and two by perturbing the primary side nominal state (i.e., simulations of Unprotected Loss of Flow, ULOF, and of Unprotected Transient of OverPower, UTOP). As a major outcome, it can be stated that the free dynamics simulations results are very satisfactory, and they may constitute the basis and provide the means for conceiving suitable control strategies for the innovative small-size LFR systems currently under development.

A hybrid solar desalination system of air humidification–dehumidification and water flashing evaporation: Part I. A numerical investigation

This paper presents a hybrid solar desalination system consisting of a humidification–dehumidification unit and single stage flashing evaporation unit. The hybrid solar desalination system was studied numerically. The heat and mass transfer and flow field are modeled theoretically in two dimensions using the finite difference scheme. For different operating and weather conditions, the fresh water productivity and salinity are computed. The model is developed to investigate the steady-state behavior of each component of the system. Six main parameters that have influence on the system productivity are studied; feed water mass flow rate of SSF unit, feed water mass flow rate of HDH unit, cooling water mass flow rate of SSF unit, cooling water mass flow rate of HDH unit, air mass flow rate and inlet cooling water temperature. The results show that, the studied hybrid desalination system gives a significant operational compatibility between the air humidification–dehumidification method and flash evaporation desalination with daily water production up to 11.14kg/m2/day. The efficiency of the system is measured by the gained output ratio (GOR) with day time. The gained output ratio (GOR) of the system reaches 4.5. The effect of the water and the air solar heaters collecting areas on the system productivity is measured. The trend of air solar heater collecting area variation showed a pronounced increase in the fresh water productivity than that of the water solar heater collecting area variation.

A solar desalination system using humidification–dehumidification process: experimental study and comparison with the theoretical results

In this study, influence of the different system operating conditions on the performance of a solar desalination system using humidification-dehumidification process have been investigated experimentally under the climatological conditions of Ankara (40°N, 33°E), Turkey. An experimental set-up that consists of a double-pass flat plate solar air heater with two glass covers, pad humidifier, dehumidifying exchanger and water storage tank was designed and manufactured. Working principle of the set-up is based on the idea of closed water and open-air cycles. A series of tests were performed on it in outdoor environment, in order to assess the effect of mass flow rate of the feed water, process air and cooling water, double-pass flat plate solar air heater, initial water temperature and amount of the water inside the storage tank on the productivity of the system. Additionally, an evacuated tubular solar water heater unit was integrated to the existing system and the effect of this integration on the performance of the system was examined. Solar radiation, wind speed, relative humidity, mass flow rate of the feed water, process air and cooling water, mass of condensate water and temperatures at various locations were obtained during the experiments.The results of the experimental study showed that under certain operating conditions, the system productivity decreases about 15% if double-pass solar air heater is not used and significant improvement on the productivity of the system is achieved by increasing the initial water temperature inside the storage tank. In addition, productivity of the system increases with increasing the feed water mass flow rate and quantity of water inside the storage tank. However, productivity of the system remains approximately the same when the air mass flow rate is increased. Moreover, increasing the cooling water mass flow rate results in the improvement on the productivity of the system investigated. Finally, results obtained from the present investigation were compared with the theoretical study and a good agreement between them is observed.

Mathematical modeling of an inclined solar water distillation system

An inclined solar water distillation (ISWD) system, which generates distilled water (i.e., condensate) and hot water at the same time, was modeled and simulated. In the parametric studies, the effects of feed water mass flow rate and solar intensity on the system parameters were investigated. Finally, the system was simulated using actual deviations of solar intensity and environment temperature during a typical summer day in North Cyprus. The system can generate 3.5–5.4 kg (per m 2 absorber plate area) distilled water during a day (i.e., 7 am till 7 pm). The temperature of the produced hot water reached as high as 60°C, and the average water temperature was about 40°C, which is good enough for domestic use, depending on the type of feed water. The simulation results are in good agreement with the experimental results.

A Concept of Passive Safety, Pressurized Water Reactor System with Inherent Matching Nature of Core Heat Generation and Heat Removal

The reduction of manpower in operation and maintenance by simplification of the system are essential to improve the safety and the economy of future light water reactors. At the Japan Atomic Energy Research Institute (JAERI), a concept of a simplified passive safety reactor system JPSR was developed for this purpose and in the concept minimization of developing work and conservation of scale-up capability in design were considered. The inherent matching nature of core heat generation and heat removal rate is introduced by the core with high reactivity coefficient for moderator density and low reactivity coefficient for fuel temperature (Doppler effect) and once-through steam generators (SGs). This nature makes the nuclear steam supply system physically-slave for the steam and energy conversion system by controlling feed water mass flow rate. The nature can be obtained by eliminating chemical shim and adopting in-vessel control rod drive mechanism (CRDM) units and a low power density core. In order to simplify the system, a large pressurizer, canned pumps, passive residual heat removal systems with air coolers as a final heat sink and passive coolant injection system are adopted and the functions of volume and boron concentration control and seal water supply are eliminated from the chemical and volume control system (CVCS). The emergency diesel generators and auxiliary component cooling system of “safety class” for transferring heat to sea water as a final heat sink in emergency are also eliminated. All of systems are built in the containment except for the air coolers of the passive residual heat removal system. The analysis of the system revealed that the primary coolant expansion in 100% load reduction in 60 s can be mitigated in the pressurizer without actuating the pressure relief valves and the pressure in 50% load change in 30 s does not exceed the maximum allowable pressure in accidental conditions in regardless of pressure regulation.

A Concept of Passive Safety Pressurized Water Reactor System with Inherent Matching Nature of Core Heat Generation and Heat Removal.

The reduction of manpower in operation and maintenance by simplification of the system are essential to improve the safety and the economy of future light water reactors. At the Japan Atomic Energy Research Institute (JAERI), a concept of a simplified passive safety reactor system JPSR was developed for this purpose and in the concept minimization of developing work and conservation of scale-up capability in design were considered. The inherent matching nature of core heat generation and heat removal rate is introduced by the core with high reactivity coefficient for moderator density and low reactivity coefficient for fuel temperature (Doppler effect) and once-through steam generators (SGs). This nature makes the nuclear steam supply system physically-slave for the steam and energy conversion system by controlling feed water mass flow rate. The nature can be obtained by eliminating chemical shim and adopting in-vessel control rod drive mechanism (CRDM) units and a low power density core. In order to simplify the system, a large pressurizer, canned pumps, passive residual heat removal systems with air coolers as a final heat sink and passive coolant injection system are adopted and the functions of volume and boron concentration control and seal water supply are eliminated from the chemical and volume control system (CVCS). The emergency diesel generators and auxiliary component cooling system of “safety class” for transferring heat to sea water as a final heat sink in emergency are also eliminated. All of systems are built in the containment except for the air coolers of the passive residual heat removal system. The analysis of the system revealed that the primary coolant expansion in 100% load reduction in 60 s can be mitigated in the pressurizer without actuating the pressure relief valves and the pressure in 50% load change in 30 s does not exceed the maximum allowable pressure in accidental conditions in regardless of pressure regulation.

Dynamic analysis and control of a solar power plant—II. Control system design and simulation

Based on the process analysis developed in the first part[1] of the present study and on frequency and time domain methods, the design of the steam generator control system of the EEC solar power plant is dealt with in this paper. More precisely, two different solutions are considered: the one, of quite simple and traditional implementation, using only Proportional Integral Differential (PID) regulators; the other, including more sophisticated control functions, using adaptive dynamic compensators of special form. The comparison of the two control systems, both endowed with feedback and feedforward control actions, clearly shows how the application of the more sophisticated temperature regulation does guarantee much better feedback control capability. This latter property is certainly crucial for water cooled solar receivers due to the very large time delays existing between the main control variable (the feedwater mass flow rate) and the controlled temperatures. On the other hand, feedback control performance requirements are strictly dependent on the achievable accuracy of the measurement of the thermal power entering the receiver, as this measurement is used to get feedforward solar disturbance compensation. In this regard, it is also shown that, with reasonable accuracy of the thermal power measurement, the control system is able to compensate solar disturbances of any amplitude.