Life Estimation of Pressurized-Air Solar-Thermal Receiver Tubes

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
David K. Fork ◽  
John Fitch ◽  
Shawn Ziaei ◽  
Robert I. Jetter
Keyword(s):  
Large Body ◽  
Inelastic Strain ◽  
Current Data ◽  
Solar Thermal ◽  
Estimation Methods ◽  
Inlet Temperature ◽  
Operational Conditions ◽  
Thermal Receiver ◽  
Cyclic Operation ◽  
Strain Model

The operational conditions of the solar-thermal receiver for a Brayton cycle engine are challenging, and lack a large body of operational data unlike steam plants. We explore the receiver's fundamental element, a pressurized tube in time varying solar flux for a series of 30 yr service missions based on hypothetical power plant designs. We developed and compared two estimation methods to predict the receiver tube lifetime based on available creep life and fatigue data for alloy 617. We show that the choice of inelastic strain model and the level of conservatism applied through design rules will vary the lifetime predictions by orders of magnitude. Based on current data and methods, a turbine inlet temperature of 1120 K is a necessary 30-yr-life-design condition for our receiver. We also showed that even though the time at operating temperature is about three times longer for fossil fuel powered (steady) operation, the damage is always lower than cyclic operation using solar power.

scholarly journals Energy Cost of Resistance Exercises: an Uptade

2011 ◽  
Vol 29A (Special-Issue) ◽  
pp. 33-39 ◽  
Author(s):  
Victor Reis ◽  
Roberto Júnior ◽  
Adam Zajac ◽  
Diogo Oliveira
Keyword(s):  
Resistance Exercise ◽  
Strength Training ◽  
Body Mass ◽  
Energy Cost ◽  
Large Body ◽  
Oxygen Deficit ◽  
Estimation Methods ◽  
Cost Calculation ◽  
Resistance Exercises ◽  
Cost Of Resistance

Energy Cost of Resistance Exercises: an UptadeThe use of resistance exercises and of typical strength training methods have been progressively used to control body mass and to promote fat mass loss. The difficulties involved in the energy cost calculation during strength training are associated with the large amount of exercises and their several variations. Mean values between ≈3 and 30 kcal·min-1are typically reported but our studies indicate that it may attain values as high as 40 kcal·min-1in exercises which involve a large body mass. Therefore, in our opinion, the next step in research must be the isolated study of each of the main resistance exercises. Since the literature is scarce and that we do consider that the majority of the studies present severe limitations, the aim of this paper is to present a critical analysis of the energy cost estimation methods and provide some insights that may help to improve knowledge on resistance exercise. It seems necessary to rely on the expired O2measurements to quantify aerobic energy. However, it is warranted further attention on how this measure is performed during resistance exercises. In example, studies on the O2on-kinetics at various conditions are warranted (i.e. as a function of intensity, duration and movement speed). As for anaerobic lactic energy, it is our opinion that both the accumulated oxygen deficit and the blood lactate energy equivalent deserve further studies; analyzing variations of each method as an attempt to establish which is more valid for resistance exercise. The quantification of alactic anaerobic energy should be complemented by accurate studies on the muscle mass involved in the different resistance exercises. From the above, it is concluded that knowledge on the energy cost in resistance exercises is in its early days and that much research is warranted before appropriate reference values may be proposed.

Saturation Flow and Capacity of Shared Lanes: Comparative Evaluation of Estimation Methods

1996 ◽  
Vol 1555 (1) ◽  
pp. 50-58
Author(s):  
G. A. Glannopoulos ◽  
Muhammad A. S. Mustafa
Keyword(s):  
Flow Rate ◽  
Comparative Evaluation ◽  
Field Measurements ◽  
Estimation Methods ◽  
Highway Capacity ◽  
Operational Conditions ◽  
Highway Capacity Manual ◽  
Traffic Volumes ◽  
Saturation Flow Rate ◽  
Saturation Flow

The operation of shared lanes, especially in the case of permitted phasing control, is still considered a complicated task and one for which many procedures and methods have been introduced. Dealt with here is the complexity when left- or right-turn movements or both are made during the unsaturated part of the opposing traffic flow. Three main methods used for estimating the shared lane's saturation flow rate and capacity values—that used in the 1985 Highway Capacity Manual (HCM) and the Australian Road Research Board (ARRB) and the Canadian methods—were analyzed and evaluated. The methodology for the comparative evaluation was based on two main approaches. In the first approach, example 1 of Chapter 9 of the HCM was used as a case study in which left through and left through right shared lanes exist in permitted phase control. In this case several computer runs were performed using the programs SIDRA and SINTRAL to estimate saturation flow and capacity values of the shared lanes opposed by different traffic volumes of the conflicting movements. Results of this approach showed that the 1985 HCM and ARRB methods are fairly close in estimating saturation flow and capacity, whereas the Canadian method gave considerably different results. Analysis showed that the sensitivity of the Canadian method to estimate saturation flow rates of the shared lane in cases of different levels of opposing traffic was an average of 10 times higher than the average of the two other methods, which were very close in their estimation of levels of opposing traffic volumes. In the second approach, field measurements of saturation flow rate values of shared lanes at different locations and operational conditions were compared with the values estimated by the three methods under the same conditions. Results, based on field observations, revealed that the Canadian method estimates of saturation flow were always lower than the measured values. At low saturation flow values, HCM estimates were slightly higher than the observed values; however, at higher saturation flow rate values. HCM estimates closely matched the observed ones. The ARRB method estimates were quite close to the observed saturation flow values under all of the different conditions considered in the field observation task.

Numerical analysis of a hybrid tubular and cavity air receiver for solar thermal applications

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sayuj Sasidharan ◽  
Pradip Dutta
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Analysis ◽  
Heat Loss ◽  
Solar Thermal ◽  
Heat Transfer Analysis ◽  
Receiver Design ◽  
Radiation Emission ◽  
Content Type ◽  
Thermal Receiver

Purpose This paper aims to deal with characterisation of the thermal performance of a hybrid tubular and cavity solar thermal receiver. Design/methodology/approach The coupled optical-flow-thermal analysis is carried out on the proposed receiver design. Modelling is performed in two and three dimensions for estimating heat loss by natural convection for an upward-facing cavity. Heat loss obtained in two dimensions by solving coupled continuity, momentum and energy equation inside the cavity domain is compared with the loss obtained using an established Nusselt number correlation for realistic receiver performance prediction. Findings It is found that radiation emission from a heated cavity wall to the ambient is the dominant mode of heat loss from the receiver. The findings recommend that fluid flow path must be designed adjacent to the surface exposed to irradiation of concentrated flux to limit conduction heat loss. Research limitations/implications On-sun experimental tests need to be performed to validate the numerical study. Practical implications Numerical analysis of receivers provides guidelines for effective and efficient solar thermal receiver design. Social implications Pressurised air receivers designed from this method can be integrated with Brayton cycles using air or supercritical carbon-dioxide to run a turbine generating electricity using a solar heat source. Originality/value The present paper proposes a novel method for coupling the flux map from ray-tracing analysis and using it as a heat flux boundary condition for performing coupled flow and heat transfer analysis. This is achieved using affine transformation implemented using extrusion coupling tool from COMSOL Multiphysics software package. Cavity surface natural convection heat transfer coefficient is obtained locally based on the surface temperature distribution.

scholarly journals Re-examining the Impact of ACFTA on ASEAN's Exports of Manufactured Goods to China

2014 ◽  
Vol 13 (3) ◽  
pp. 63-82 ◽  
Author(s):  
Tham Siew Yean ◽  
Andrew Kam Jia Yi
Keyword(s):  
Positive Impact ◽  
Large Body ◽  
Trade Agreement ◽  
Estimation Methods ◽  
Utilization Rate ◽  
Production Networks ◽  
Regional Trade ◽  
Firm Level ◽  
Manufactured Goods ◽  
The Impact

There is a relatively large body of literature examining ASEAN–China relations, including assessments of the impact of the ASEAN–China Free Trade Agreement (ACFTA) on ASEAN's welfare and its trade with China. Overall, the results of these studies indicate a positive impact of ACFTA on the region's exports to China. These results differ from firm-level surveys that indicate a low utilization rate of most regional trade agreement tariff concessions, including those provided by ACFTA. Moreover, trade in manufactured goods in the region has been characterized as market-led, and governed by multinationals (MNCs) and their regional production networks. Thus, MNC decisions are the driving force influencing changes in manufactured parts and components trade in the region. This trade is also fostered by duty-free imports in the export enclaves provided by the host economies for these MNCs. In view of the conflicting empirical evidence on the trade effects of regional trade agreements, the objective of this study is to re-assess the impact of ACFTA on ASEAN's manufactured exports to China. In performing this analysis, we separately evaluate the effects of trade in parts and components (P&C) and non–parts and components (non P&C) or final manufactured goods. When we apply gravity estimation methods to individual regressions for these two forms of trade, we find that the determinants of trade are indeed different for the two sectors, and that the implementation of ACFTA had different effects on P&C versus final goods ASEAN exports to China.

scholarly journals Performance Evaluation of a Small Scale Modular Solar Trigeneration System

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Handong Wang
Keyword(s):  
Vapor Pressure ◽  
Thermal Power ◽  
Hot Water ◽  
Solar Thermal ◽  
Modular System ◽  
Small Scale ◽  
Inlet Temperature ◽  
Increase With Increase ◽  
Energy And Exergy ◽  
System Operating

In order to improve the efficiency of solar thermal power (STP) system, a novel modular system combining cooling, heating, and power generation (CCHP) is proposed and introduced in this work. This modular CCHP system can simultaneously provide 10 kW electricity, −15~5°C coolant, and 60°C hot water to meet the requirements of cooling, heating, and electricity in a general family or other fields. The flow chart and working process of the modular system are introduced, based on which the energy and exergy efficiencies at the CCHP and STP operation modes are primarily evaluated and discussed. The results show that when the output electricity is constant, the overall efficiencies of energy and exergy of the system operating at the CCHP mode are 9.37 times and 2.62 times as big as those of the system operating at the STP mode, respectively. Thus, the modular solar thermal CCHP system can improve the energy and exergy efficiencies. Furthermore, calculation shows that both the overall energy and exergy efficiencies decrease with increase of inlet vapor temperature at given inlet vapor pressure, but both the efficiencies increase with increase of inlet vapor pressure at given inlet temperature.

scholarly journals A Review of Innovation-Based Methods to Jointly Estimate Model and Observation Error Covariance Matrices in Ensemble Data Assimilation

2020 ◽  
Vol 148 (10) ◽  
pp. 3973-3994 ◽  
Author(s):  
Pierre Tandeo ◽  
Pierre Ailliot ◽  
Marc Bocquet ◽  
Alberto Carrassi ◽  
Takemasa Miyoshi ◽  
...  
Keyword(s):  
Data Assimilation ◽  
Current Data ◽  
Covariance Matrices ◽  
Estimation Methods ◽  
Observation Error ◽  
Correlated Noise ◽  
Unified Framework ◽  
Error Covariance ◽  
Error Terms ◽  
Observation Space

AbstractData assimilation combines forecasts from a numerical model with observations. Most of the current data assimilation algorithms consider the model and observation error terms as additive Gaussian noise, specified by their covariance matrices and , respectively. These error covariances, and specifically their respective amplitudes, determine the weights given to the background (i.e., the model forecasts) and to the observations in the solution of data assimilation algorithms (i.e., the analysis). Consequently, and matrices significantly impact the accuracy of the analysis. This review aims to present and to discuss, with a unified framework, different methods to jointly estimate the and matrices using ensemble-based data assimilation techniques. Most of the methods developed to date use the innovations, defined as differences between the observations and the projection of the forecasts onto the observation space. These methods are based on two main statistical criteria: 1) the method of moments, in which the theoretical and empirical moments of the innovations are assumed to be equal, and 2) methods that use the likelihood of the observations, themselves contained in the innovations. The reviewed methods assume that innovations are Gaussian random variables, although extension to other distributions is possible for likelihood-based methods. The methods also show some differences in terms of levels of complexity and applicability to high-dimensional systems. The conclusion of the review discusses the key challenges to further develop estimation methods for and . These challenges include taking into account time-varying error covariances, using limited observational coverage, estimating additional deterministic error terms, or accounting for correlated noise.

Theoretical Performance of Silica Gel Desiccant Wheel

2019 ◽  
Vol 7 (3) ◽  
pp. 66-74
Author(s):  
Zainab Mahdi Salih ◽  
Abdulsalam D. M.Hassan ◽  
Amer Majeed Al-Dabagh
Keyword(s):  
Silica Gel ◽  
Air Temperature ◽  
Inlet Temperature ◽  
Moisture Removal ◽  
Humidity Ratio ◽  
Desiccant Wheel ◽  
Operational Conditions ◽  
Removal Capacity ◽  
Air Inlet ◽  
Theoretical Performance

Abstract— Silica gel is a substance commonly used in desiccant wheel, which in turn is used in many applications to reduce moisture from the supplied air to a specific space. In this research,  the effect of different operational conditions on the performance of silica gel wheel were studied. The desiccant wheel, which has been used, has a diameter of 55 cm and thickness of 20 cm. It contains 34 kg of silica gel and rotate at a speed of 30 rph. The theoretical performance coefficients of the desiccant wheel which have been studied include ,moisture removal capacity(MRC),dehumidification performance(DCOP),latent coefficient of performance (COPlat), and desiccant wheel effectiveness(ϵ_d). The theoretical investigation of these coefficients was done by using Novel Aire Technology software program (Simulation program of desiccant wheel) (2012). While the operational conditions like process air (humid air)inlet temperature between(30 to 43.4)0C, process air inlet humidity ratio between (0.011 to 0.019)kg/kgdry air ,regeneration air inlet temperature between (56.5 to 70)0C,and process air mass flow rate between(0.0814 to 0.199)kg/s. The results shows that the effectiveness and the moisture removal capacity have the same behavior increase with the increasing in mass flow rate from(0.0814 to 0.199) kg/s, humidity ratio from(11 to19)g/kgdry air, and regeneration air temperature from(56 t0 70)oC. But they reduces with increasing of inlet process air temperature from(30 to43.4)oC..

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