Sensitivity analysis and component modelling of a packed-type liquid desiccant system at partial load operating conditions

District heating networks (DHNs) are crucial infrastructures for the implementation of energy efficiency and CO2 reduction plans, especially in countries with continental climate. DHNs are often complex systems and their energy performance may be largely affected by the operating conditions. Optimal operation of DHNs involves the optimization of the pumping system. This is particularly important for large networks and for low temperature networks. A common practice to perform optimization consists in using a phyical model. Nevertheless, simulation and optimization of DHNs may involve large computational resources, because of thire possible large extension and the number of scenarios to be examined. A reduced model, obtained from the physical model, can be effectively applied to multiple simulations of a network, with significant reduction of the computational time and resources. In this paper, a large district heating system, which supplies heating to a total volume of buildings of about 50 million of cubic meters, is considered. The use of a reduced model based on proper orthogonal decomposition (POD) is investigated. Various operating conditions corresponding to partial load operation are analyzed using a fluid-dynamic model of the network. Results show that optimal settings are not particularly regular with respect to load variation. This means that any variation in the thermal load generally involves changes in the set points of all groups. For this reason, a sensitivity analysis is performed using the POD model in order to check the opportunities to limit the number of variations in the pumping settings without significant penalization of the total pumping power. The proposed approach is shown to be very effective for the optimal management of complex district heating systems.

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Sensitivity Analysis of OTEC-CC-MX-1 kWe Plant Prototype

Energies ◽

10.3390/en14092585 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2585

Author(s):

Jessica Guadalupe Tobal-Cupul ◽

Estela Cerezo-Acevedo ◽

Yair Yosias Arriola-Gil ◽

Hector Fernando Gomez-Garcia ◽

Victor Manuel Romero-Medina

Keyword(s):

Sensitivity Analysis ◽

Experimental Tests ◽

Caribbean Sea ◽

Ocean Model ◽

Operating Conditions ◽

Working Fluid ◽

Ocean Energy ◽

Mexican Caribbean ◽

Water Temperature Data ◽

Mass Flows

The Mexican Caribbean Sea has potential zones for Ocean Thermal Energy Conversion (OTEC) implementation. Universidad del Caribe and Instituto de Ciencias del Mar y Limnologia, with the support of the Mexican Centre of Innovation in Ocean Energy, designed and constructed a prototype OTEC plant (OTEC-CC-MX-1 kWe), which is the first initiative in Mexico for exploitation of this type of renewable energy. This paper presents a sensitivity analysis whose objective was to know, before carrying out the experimental tests, the behavior of OTEC-CC-MX-1 kWe regarding temperature differences, as well as the non-possible operating conditions, which allows us to assess possible modifications in the prototype installation. An algorithm was developed to obtain the inlet and outlet temperatures of the water and working fluid in the heat exchangers using the monthly surface and deep-water temperature data from the Hybrid Coordinate Ocean Model and Geographically Weighted Regression Temperature Model for the Mexican Caribbean Sea. With these temperatures, the following were analyzed: fluctuation of thermal efficiency, mass flows of R-152a and water and power production. By analyzing the results, we verified maximum and minimum mass flows of water and R-152a to produce 1 kWe during a typical year in the Mexican Caribbean Sea and the conditions when the production of electricity is not possible for OTEC-CC-MX-1 kWe.

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Determination of cost-efficient cooling power range for improving the performance of internally cooled ultrasonic atomization liquid desiccant dehumidifiers

Indoor and Built Environment ◽

10.1177/1420326x20913325 ◽

2020 ◽

Vol 29 (9) ◽

pp. 1260-1276

Author(s):

Zili Yang ◽

Lu-An Chen ◽

Ruiyang Tao ◽

Ke Zhong

Keyword(s):

Power Efficiency ◽

Removal Rate ◽

Operating Conditions ◽

Cooling Power ◽

Internal Cooling ◽

Liquid Desiccant ◽

Improvement Rate ◽

Ultrasonic Atomization ◽

Internally Cooled ◽

Cost Efficient

Liquid desiccant dehumidifiers (LDDs) can be improved by adding internal cooling. However, the addition of excessive cooling power may deteriorate the system‘s cost-efficiency, whereas the addition of insufficient cooling power leads to negligible performance improvements. The objective of this study is to determine the suitable cost-efficient cooling power range for improving the performance of internally cooled LDDs (IC-LDDs). A novel method and a set of criteria related to the moisture removal rate, cooling-power efficiency ( ηc) and coefficient of dehumidification performance from cooling power ( DCOPcooling) were proposed to determine cost-efficient cooling power. The internally cooled ultrasonic atomization liquid desiccant system (IC-UADS), together with a well-validated model based on the conservation laws of mass and energy and the sensible heat balance, was adopted to demonstrate the analysis. The results showed that, although the dehumidification performance improves with increasing cooling power, the improvement rate decreases, while ηcand DCOPcoolingdecline quickly (by 87.9%). For cost-efficient improvement, the necessary power proportion of internal cooling to the system‘s target dehumidification capacity tends to be stable, which was about 29% for the IC-UADS, and independent of the operating conditions. The results may help to determine the reasonable cooling power range for cost-efficient improvement of IC-LDDs.

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Metal Temperature Prediction of a Dry Low NOx Class Flame Tube by Computational Fluid Dynamics Conjugate Heat Transfer Approach

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4031384 ◽

2015 ◽

Vol 138 (3) ◽

Cited By ~ 2

Author(s):

Riccardo Da Soghe ◽

Cosimo Bianchini ◽

Antonio Andreini ◽

Lorenzo Mazzei ◽

Giovanni Riccio ◽

...

Keyword(s):

Heat Transfer ◽

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Operating Conditions ◽

Metal Temperature ◽

Thermal Loads ◽

Flame Tube ◽

Numerical Predictions ◽

Partial Load ◽

Critical Components

Combustor liner of present gas turbine engines is subjected to high thermal loads as it surrounds high temperature combustion reactants and is hence facing the related radiative load. This generally produces high thermal stress levels on the liner, strongly limiting its life expectations and making it one of the most critical components of the entire engine. The reliable prediction of such thermal loads is hence a crucial aspect to increase the flame tube life span and to ensure safe operations. The present study aims at investigating the aerothermal behavior of a GE Dry Low NOx (DLN1) class flame tube and in particular at evaluating working metal temperatures of the liner in relation to the flow and heat transfer state inside and outside the combustion chamber. Three different operating conditions have been accounted for (i.e., lean–lean partial load, premixed full load, and primary load) to determine the amount of heat transfer from the gas to the liner by means of computational fluid dynamics (CFD). The numerical predictions have been compared to experimental measurements of metal temperature showing a good agreement between CFD and experiments.

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Efficiency and Sensitivity Analysis of Cavern-Based CAES Systems During off-Design Operating Conditions

Springer Proceedings in Energy - Sustaining Tomorrow ◽

10.1007/978-3-030-64715-5_10 ◽

2021 ◽

pp. 177-199

Author(s):

Mehdi Ebrahimi ◽

David S.-K. Ting ◽

Rupp Carriveau ◽

Andrew McGillis ◽

David Brown

Keyword(s):

Sensitivity Analysis ◽

Operating Conditions

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Performance optimization of polymeric porous membrane-based liquid desiccant air dehumidifier used in air conditioning system

International Journal of Energy and Environmental Engineering ◽

10.1007/s40095-019-00324-1 ◽

2019 ◽

Vol 11 (1) ◽

pp. 55-71

Author(s):

Ali Mohammad Jafarpour ◽

Farivar Fazelpour ◽

Seyyed Abbas Mousavi

Keyword(s):

Performance Optimization ◽

Air Conditioning ◽

Weather Conditions ◽

Porous Membrane ◽

Operating Conditions ◽

Regeneration System ◽

Liquid Desiccant ◽

Air Conditioning System ◽

Air Stream ◽

Improved Performance

AbstractIn this study an experimental design was developed to optimize the performance and structure of a membrane-based parallel-plate liquid desiccant dehumidifier used in air conditioning regeneration system which operates under high humidity weather conditions. We conducted a series of polymeric porous membranes with different compositions fabricated that were prepared with various weight percentages of polysulfone (PSU), mixed with N-methyl-2-pyrrolidone (NMP) and dimethyl form amide (DMF) solvents. Furthermore, the designed experiments were performed under various operating conditions, indicating that the dehumidification efficiency declines with increasing flow rate, temperature, and humidity. Consequently, a membrane with optimized porosity and moisture permeability was selected which resulted in eliminating the carryover of solution droplets in the air, largely due to separating the flow condition of liquid desiccant (Li Cl) and air. This specific design is also greatly benefited by removing the water vapor from the air stream. The results of mathematical model simulations indicate that the DMF solvent had higher dehumidification capability compared with that of NMP under the optimized operating conditions. Additionally, it can clarify the porosity of the membrane which plays a significant role in the overall performance. Therefore, the fabricated membrane produces fresh cool air, and it can be applied as a guiding sample for designing the membrane-based dehumidifier with improved performance.

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Analytical Modeling and Performance Study of a Cross Flow Air Dehumidifier Using Liquid Desiccant

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.875-877.1205 ◽

2014 ◽

Vol 875-877 ◽

pp. 1205-1213 ◽

Cited By ~ 2

Author(s):

Mohamed M. Bassuoni

Keyword(s):

Numerical Solutions ◽

Removal Rate ◽

Cross Flow ◽

Operating Conditions ◽

Maximum Deviation ◽

Performance Study ◽

Liquid Desiccant ◽

Mass Transfer Processes ◽

And Performance ◽

Air Conditioning Systems

The dehumidifier is a key component in liquid desiccant air conditioning systems. Various mathematical models of heat and mass transfer processes inside the dehumidifier are introduced and numerically solved in the literature. Analytical solutions have more advantages than numerical solutions in studying the dehumidifier performance parameters. This paper presents the results from an analytical model for the performance of an adiabatic cross flow liquid desiccant air dehumidifier. Calcium chloride is used as desiccant material in this investigation. Both humidity and temperature effectiveness of the dehumidifier are used to predict the performance of the device under various operating conditions. Good accuracy has been found between analytical solution and reliable experimental results with a maximum deviation of +6.63% and -5.65% in the moisture removal rate. The method developed here can be used in the quick prediction of the dehumidifier performance. The exit parameters from the dehumidifier are evaluated under the effects of variables such as air temperature and humidity, desiccant temperature and concentration and air to desiccant flow rates. The results show that hot humid air and desiccant concentration have the greatest impact on the performance of the dehumidifier.

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A Field Study of a Low-Flow Internally Cooled/Heated Liquid Desiccant Air Conditioning System: Quasi-Steady and Transient Performance

Journal of Solar Energy Engineering ◽

10.1115/1.4033026 ◽

2016 ◽

Vol 138 (3) ◽

Cited By ~ 11

Author(s):

Ahmed H. Abdel-Salam ◽

Chris McNevin ◽

Lisa Crofoot ◽

Stephen J. Harrison ◽

Carey J. Simonson

Keyword(s):

Air Conditioning ◽

Field Performance ◽

Ambient Air ◽

Operating Conditions ◽

Coefficient Of Performance ◽

Low Flow ◽

Transient Field ◽

Liquid Desiccant ◽

Internally Cooled ◽

Steady Performance

The field performance of a low-flow internally cooled/heated liquid desiccant air conditioning (LDAC) system is investigated in this paper. The quasi-steady performance (sensible and latent heat transfer rates, coefficient of performance (COP), and uncertainties) of the LDAC system is quantified under different ambient air conditions. A major contribution of this work is a direct comparison of the transient and quasi-steady performance of the LDAC system. This paper is the first to quantify the importance of transients and shows that, for the environmental and operating conditions in this paper, transients can be neglected when estimating the energy consumption of the LDAC system. Another major contribution of this work is the development and verification of a new method that quantifies (with acceptable uncertainties) the quasi-steady performance of a LDAC system from transient field data using average data.

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Performance of Francis Turbine Operating at Excess Load Condition

Volume 3: Computational Fluid Dynamics; Micro and Nano Fluid Dynamics ◽

10.1115/fedsm2020-20053 ◽

2020 ◽

Author(s):

Muhannad Altimemy ◽

Justin Caspar ◽

Alparslan Oztekin

Keyword(s):

Flow Field ◽

Draft Tube ◽

Turbine Blades ◽

Pressure Fluctuations ◽

Load Condition ◽

Operating Conditions ◽

Francis Turbine ◽

Partial Load ◽

Dynamics Simulations ◽

Excess Load

Abstract Computational fluid dynamics simulations are conducted to characterize the spatial and temporal characteristics of the flow field inside a Francis turbine operating in the excess load regime. A high-fidelity Large Eddy Simulation (LES) turbulence model is applied to investigate the flow-induced pressure fluctuations in the draft tube of a Francis Turbine. Probes placed alongside the wall and in the center of the draft tube measure the pressure signal in the draft tube, the pressure over the turbine blades, and the power generated to compare against previous studies featuring design point and partial load operating conditions. The excess load is seen during Francis turbines in order to satisfy a spike in the electrical demand. By characterizing the flow field during these conditions, we can find potential problems with running the turbine at excess load and inspire future studies regarding mitigation methods. Our studies found a robust low-pressure region on the edges of turbine blades, which could cause cavitation in the runner region, which would extend through the draft tube, and high magnitude of pressure fluctuations were observed in the center of the draft tube.

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